chore: adopt remaining local development state

Catch-all for the intermixed residue of the unpushed otko-development
work ported into this tree: combinations/console-dock/quick-guide wiring
across commands, core, services, views and tests; repo-wide ruff-format
normalization; README/CONTRIBUTING updates; and the toolbar default
(both toolbars now open in the top area, quick guide text updated).

Splitting this further would require hunk-level surgery with low
confidence; the preceding commits in this branch isolate the
self-contained features.

CONTRIBUTING.md

@@ -1,37 +1,97 @@
 # Contributing
 
-Early-stage project. The bar is architecture cleanliness, not feature
+Thanks for helping with OTKO — a SAP2000-style desktop GUI for
-count. If your change breaks a layering rule below, it won't merge —
+OpenSeesPy. Early-stage project: the bar is architecture cleanliness, not
-no matter how useful the feature.
+feature count. If your change breaks a layering rule below, it won't
+merge — no matter how useful the feature.
 
 ## Dev setup
 
 ```bash
 python -m venv .venv
-source .venv/bin/activate
+source .venv/bin/activate           # Linux / macOS
-pip install -e ".[dev]"
+# .venv\Scripts\activate            # Windows
+pip install -e ".[gui,dev]"
 pre-commit install
 ```
 
+`pip install -e ".[gui,dev]"` pulls the Qt/PyVista desktop stack plus the
+dev tools. For a headless checkout (core + services only, no Qt) use
+`pip install -e .` instead. Python 3.10+; on Windows use 3.12+.
+
+Launch the GUI with:
+
+```bash
+python -m otko
+```
+
+`pre-commit install` wires ruff + mypy into your local git hooks so
+obvious issues are caught before a commit. Run it once per clone.
+
 ## Before opening a PR
 
+Run the verify commands in this order and make sure they are all clean:
+
 ```bash
 ruff check src tests
-ruff format src tests
+ruff format src tests          # line-length 100, E501 ignored
 mypy src/otko/core src/otko/services
-pytest -m "not slow"
+pytest -m "not slow"           # CI gate: lint → this, on 3.10/3.11/3.12 × ubuntu/windows/macos
 ```
 
+Focused runs are faster while iterating: `pytest tests/unit` (pure logic,
+milliseconds), `pytest tests/gui -k <name>` (pytest-qt, needs a display;
+Linux GUI tests want `xvfb-run -a pytest ...`), and
+`pytest tests/integration -k <name>` (real OpenSeesPy runs). Single test:
+`pytest tests/unit/test_project.py::test_name -q`. Markers: `gui`, `slow`.
+
 ## Architectural rules (enforced in review)
 
-1. `core/` may not import Qt or `openseespy`. Period.
+OTKO uses a strict one-way **MVVM + service** architecture. Dependencies
-2. `services/` may not import Qt.
+flow outward-in only:
-3. `views/` may not import `openseespy` directly — go through a service.
+
-4. Public functions and methods need type hints and a docstring.
+```
-5. New domain entities go through Pydantic validation.
+views → viewmodels → services → core
-6. Long-running operations (>50 ms) run off the GUI thread.
+```
+
+`commands` sits alongside the bridge and owns every model mutation.
+
+1. `core/` is pure Python — stdlib + numpy + pydantic. It may **not**
+   import Qt or `openseespy`. Period.
+2. `services/` may use `core` + `h5py` + `openseespy`, but may **not**
+   import Qt.
+3. `views/` (PySide6/pyvistaqt) may **not** import `openseespy` directly —
+   go through a service. No business logic in `views`.
+4. `viewmodels/` bridges `core` ↔ Qt (signals, `QUndoStack`).
+5. `commands/` holds the `QUndoCommand` subclasses; all model mutations
+   go through `commands`, not ad-hoc edits in `views`.
+6. Public functions and methods need type hints and a docstring.
+7. New domain entities go through Pydantic validation.
+8. Long-running operations (>50 ms) run off the GUI thread (`AnalysisWorker`
+   in a `QThread`, cancelled via `isInterruptionRequested()`; results cross
+   threads as a lightweight `ResultsHandle` written to HDF5).
+
+The full package map and the fixed OpenSeesPy command order the runner
+emits live in [`docs/architecture.md`](docs/architecture.md). Never
+reorder the runner's commands.
+
+## Branch model
+
+`main` is the default and integration branch. Work on short-lived topic
+branches cut from `main` — `feat/<topic>`, `fix/<topic>`, or
+`docs/<topic>` — and open a pull request against `main`. Do not commit
+directly to `main` from an agent session. There is no `develop` branch.
 
 ## Commit style
 
 Conventional Commits — `feat:`, `fix:`, `refactor:`, `docs:`, `test:`,
-`chore:`, `ci:`.
+`chore:`, `ci:`. Keep each commit focused; a `feat:` commit should add a
+feature, not mix one in with unrelated refactors.
+
+## Documentation
+
+If your change is user-visible, update
+[`docs/QUICK_GUIDE.md`](docs/QUICK_GUIDE.md) and the relevant roadmap or
+ADR entry. Project model files are `.osmodel` (Pydantic-validated JSON);
+regenerate the checked-in `examples/*.osmodel` from their scripts with
+`python examples/<name>.py` rather than hand-editing them.

README.md

@@ -82,6 +82,13 @@ views (Qt)  →  viewmodels  →  services (OpenSeesRunner, Persistence)  →  c
 Long version in [`docs/architecture.md`](docs/architecture.md),
 including the OpenSeesPy command order the runner emits.
 
+## Documentation
+
+Practical, task-first walkthroughs live in
+[`docs/QUICK_GUIDE.md`](docs/QUICK_GUIDE.md) — a cantilever build,
+modal analysis, report/script export, display units, and undo/redo.
+The full index is [`docs/README.md`](docs/README.md).
+
 ## Install (development)
 
 **Desktop GUI** (Qt, PyVista, pyqtgraph, imageio):

src/otko/commands/__init__.py

@@ -6,6 +6,11 @@ from otko.commands.analysis import (
     UpdateAnalysisCaseCommand,
 )
 from otko.commands.base import ProjectCommand
+from otko.commands.combinations import (
+    AddCombinationsCommand,
+    DeleteCombinationsCommand,
+    UpdateCombinationCommand,
+)
 from otko.commands.constraints import (
     AddEqualDOFConstraintCommand,
     DeleteEqualDOFConstraintCommand,
@@ -67,25 +72,50 @@ from otko.commands.transforms import (
 
 __all__ = [
     "ProjectCommand",
-    "AddNodesCommand", "DeleteNodesCommand", "SetRestraintCommand", "SetMassCommand",
+    "AddNodesCommand",
+    "DeleteNodesCommand",
+    "SetRestraintCommand",
+    "SetMassCommand",
     "UpdateNodeFieldsCommand",
-    "AddElementsCommand", "DeleteElementsCommand",
+    "AddElementsCommand",
-    "AssignSectionCommand", "AssignMaterialCommand",
+    "DeleteElementsCommand",
-    "ReplaceElementsCommand", "ConvertElementTypeCommand",
+    "AssignSectionCommand",
+    "AssignMaterialCommand",
+    "ReplaceElementsCommand",
+    "ConvertElementTypeCommand",
     "UpdateElementFieldsCommand",
-    "AddMaterialsCommand", "DeleteMaterialsCommand", "UpdateMaterialCommand",
+    "AddMaterialsCommand",
-    "AddSectionsCommand", "DeleteSectionsCommand", "UpdateSectionCommand",
+    "DeleteMaterialsCommand",
-    "AddNodalLoadsCommand", "AddElementLoadsCommand",
+    "UpdateMaterialCommand",
-    "UpdateNodalLoadCommand", "DeleteNodalLoadsCommand",
+    "AddSectionsCommand",
-    "UpdateElementLoadCommand", "DeleteElementLoadsCommand",
+    "DeleteSectionsCommand",
-    "MoveNodesCommand", "ReplicateCommand", "MirrorCommand", "Plane",
+    "UpdateSectionCommand",
-    "AddAnalysisCasesCommand", "DeleteAnalysisCasesCommand", "UpdateAnalysisCaseCommand",
+    "AddNodalLoadsCommand",
+    "AddElementLoadsCommand",
+    "UpdateNodalLoadCommand",
+    "DeleteNodalLoadsCommand",
+    "UpdateElementLoadCommand",
+    "DeleteElementLoadsCommand",
+    "MoveNodesCommand",
+    "ReplicateCommand",
+    "MirrorCommand",
+    "Plane",
+    "AddAnalysisCasesCommand",
+    "DeleteAnalysisCasesCommand",
+    "UpdateAnalysisCaseCommand",
+    "AddCombinationsCommand",
+    "DeleteCombinationsCommand",
+    "UpdateCombinationCommand",
     "SetGridSystemCommand",
     "SetCoordSystemsCommand",
-    "AddTimeSeriesCommand", "AddLoadPatternCommand",
+    "AddTimeSeriesCommand",
-    "UpdateTimeSeriesCommand", "DeleteTimeSeriesCommand",
+    "AddLoadPatternCommand",
-    "UpdateLoadPatternCommand", "DeleteLoadPatternCommand",
+    "UpdateTimeSeriesCommand",
+    "DeleteTimeSeriesCommand",
+    "UpdateLoadPatternCommand",
+    "DeleteLoadPatternCommand",
     "AddEqualDOFConstraintCommand",
-    "UpdateEqualDOFConstraintCommand", "DeleteEqualDOFConstraintCommand",
+    "UpdateEqualDOFConstraintCommand",
+    "DeleteEqualDOFConstraintCommand",
     "SetUnitsCommand",
 ]

src/otko/commands/analysis.py

@@ -13,8 +13,9 @@ if TYPE_CHECKING:
 class AddAnalysisCasesCommand(ProjectCommand):
     """Add one or more analysis cases."""
 
-    def __init__(self, vm: "ProjectViewModel", cases: list[Any], *,
+    def __init__(
-                 text: str | None = None) -> None:
+        self, vm: "ProjectViewModel", cases: list[Any], *, text: str | None = None
+    ) -> None:
         super().__init__(vm, text or f"Add {len(cases)} analysis case(s)")
         self._cases = list(cases)
 
@@ -42,12 +43,9 @@ class DeleteAnalysisCasesCommand(ProjectCommand):
 
     def redo(self) -> None:
         self._removed = [
-            (i, c) for i, c in enumerate(self.project.analyses)
+            (i, c) for i, c in enumerate(self.project.analyses) if c.id in self._case_ids
-            if c.id in self._case_ids
-        ]
-        self.project.analyses[:] = [
-            c for c in self.project.analyses if c.id not in self._case_ids
         ]
+        self.project.analyses[:] = [c for c in self.project.analyses if c.id not in self._case_ids]
         self._notify()
 
     def undo(self) -> None:

src/otko/commands/base.py

@@ -38,9 +38,7 @@ class ProjectCommand(QUndoCommand):
     @property
     def project(self) -> "Project":
         if self._vm.project is None:
-            raise RuntimeError(
+            raise RuntimeError(f"Cannot apply '{self.text()}': no active project.")
-                f"Cannot apply '{self.text()}': no active project."
-            )
         return self._vm.project
 
     def _notify(self) -> None:

src/otko/commands/constraints.py

@@ -34,8 +34,7 @@ class AddEqualDOFConstraintCommand(ProjectCommand):
 
     def undo(self) -> None:
         self.project.mp_constraints[:] = [
-            mp for mp in self.project.mp_constraints
+            mp for mp in self.project.mp_constraints if mp != self._constraint
-            if mp != self._constraint
         ]
         self._notify()
 

src/otko/commands/loads.py

@@ -47,7 +47,7 @@ class AddNodalLoadsCommand(ProjectCommand):
         self._forces = forces
         self._pattern_id = pattern_id
         self._new_pattern_name = new_pattern_name
-        self._new_ts_type = new_ts_type     # "Linear" or "Constant"
+        self._new_ts_type = new_ts_type  # "Linear" or "Constant"
         self._created_ts: TimeSeries | None = None
         self._created_pattern: PlainLoadPattern | None = None
         self._added_loads: list[tuple[int, NodalLoad]] = []  # (pattern_id, load)
@@ -101,7 +101,10 @@ class AddNodalLoadsCommand(ProjectCommand):
                     break
         self._added_loads.clear()
         # Roll back any infrastructure we created.
-        if self._created_pattern is not None and self._created_pattern in self.project.load_patterns:
+        if (
+            self._created_pattern is not None
+            and self._created_pattern in self.project.load_patterns
+        ):
             self.project.load_patterns.remove(self._created_pattern)
             self._created_pattern = None
         if self._created_ts is not None and self._created_ts in self.project.time_series:
@@ -157,7 +160,10 @@ class AddElementLoadsCommand(ProjectCommand):
         pattern = self._resolve_pattern()
         for eid in self._element_ids:
             load = UniformElementLoad(
-                element_id=eid, wy=self._wy, wz=self._wz, wx=self._wx,
+                element_id=eid,
+                wy=self._wy,
+                wz=self._wz,
+                wx=self._wx,
             )
             pattern.element_loads.append(load)
             self._added_loads.append((pattern.id, load))
@@ -171,7 +177,10 @@ class AddElementLoadsCommand(ProjectCommand):
                         pat.element_loads.remove(load)
                     break
         self._added_loads.clear()
-        if self._created_pattern is not None and self._created_pattern in self.project.load_patterns:
+        if (
+            self._created_pattern is not None
+            and self._created_pattern in self.project.load_patterns
+        ):
             self.project.load_patterns.remove(self._created_pattern)
             self._created_pattern = None
         if self._created_ts is not None and self._created_ts in self.project.time_series:

src/otko/commands/materials.py

@@ -13,7 +13,9 @@ if TYPE_CHECKING:
 class AddMaterialsCommand(ProjectCommand):
     """Add one or more materials in a single undoable step."""
 
-    def __init__(self, vm: "ProjectViewModel", materials: list[Any], *, text: str | None = None) -> None:
+    def __init__(
+        self, vm: "ProjectViewModel", materials: list[Any], *, text: str | None = None
+    ) -> None:
         super().__init__(vm, text or f"Add {len(materials)} material(s)")
         self._materials = list(materials)
 
@@ -41,8 +43,7 @@ class DeleteMaterialsCommand(ProjectCommand):
 
     def redo(self) -> None:
         self._removed = [
-            (i, m) for i, m in enumerate(self.project.materials)
+            (i, m) for i, m in enumerate(self.project.materials) if m.id in self._material_ids
-            if m.id in self._material_ids
         ]
         self.project.materials[:] = [
             m for m in self.project.materials if m.id not in self._material_ids

src/otko/commands/nodes.py

@@ -14,7 +14,9 @@ if TYPE_CHECKING:
 class AddNodesCommand(ProjectCommand):
     """Add one or more nodes in a single undoable step."""
 
-    def __init__(self, vm: "ProjectViewModel", nodes: list[Node], *, text: str | None = None) -> None:
+    def __init__(
+        self, vm: "ProjectViewModel", nodes: list[Node], *, text: str | None = None
+    ) -> None:
         super().__init__(vm, text or f"Add {len(nodes)} node(s)")
         self._nodes = list(nodes)
 
@@ -42,14 +44,15 @@ class DeleteNodesCommand(ProjectCommand):
     def __init__(self, vm: "ProjectViewModel", node_ids: set[int]) -> None:
         super().__init__(vm, f"Delete {len(node_ids)} node(s)")
         self._node_ids = set(node_ids)
-        self._removed_nodes: list[tuple[int, Node]] = []      # (index, node)
+        self._removed_nodes: list[tuple[int, Node]] = []  # (index, node)
-        self._removed_elements: list[tuple[int, object]] = [] # (index, element)
+        self._removed_elements: list[tuple[int, object]] = []  # (index, element)
         self._removed_mp_constraints: list[tuple[int, object]] = []
 
     def redo(self) -> None:
         # Cascade: snapshot every element that references a doomed node.
         self._removed_elements = [
-            (i, el) for i, el in enumerate(self.project.elements)
+            (i, el)
+            for i, el in enumerate(self.project.elements)
             if any(nid in self._node_ids for nid in el.nodes)
         ]
         doomed_elem_ids = {el.id for _, el in self._removed_elements}
@@ -58,7 +61,8 @@ class DeleteNodesCommand(ProjectCommand):
         ]
 
         self._removed_mp_constraints = [
-            (i, mp) for i, mp in enumerate(self.project.mp_constraints)
+            (i, mp)
+            for i, mp in enumerate(self.project.mp_constraints)
             if mp.retained_node in self._node_ids or mp.constrained_node in self._node_ids
         ]
         doomed_mp = {id(mp) for _, mp in self._removed_mp_constraints}
@@ -69,9 +73,7 @@ class DeleteNodesCommand(ProjectCommand):
         self._removed_nodes = [
             (i, n) for i, n in enumerate(self.project.nodes) if n.id in self._node_ids
         ]
-        self.project.nodes[:] = [
+        self.project.nodes[:] = [n for n in self.project.nodes if n.id not in self._node_ids]
-            n for n in self.project.nodes if n.id not in self._node_ids
-        ]
         self._notify()
 
     def undo(self) -> None:

src/otko/commands/sections.py

@@ -13,7 +13,9 @@ if TYPE_CHECKING:
 class AddSectionsCommand(ProjectCommand):
     """Add one or more sections in a single undoable step."""
 
-    def __init__(self, vm: "ProjectViewModel", sections: list[Any], *, text: str | None = None) -> None:
+    def __init__(
+        self, vm: "ProjectViewModel", sections: list[Any], *, text: str | None = None
+    ) -> None:
         super().__init__(vm, text or f"Add {len(sections)} section(s)")
         self._sections = list(sections)
 
@@ -41,8 +43,7 @@ class DeleteSectionsCommand(ProjectCommand):
 
     def redo(self) -> None:
         self._removed = [
-            (i, s) for i, s in enumerate(self.project.sections)
+            (i, s) for i, s in enumerate(self.project.sections) if s.id in self._section_ids
-            if s.id in self._section_ids
         ]
         self.project.sections[:] = [
             s for s in self.project.sections if s.id not in self._section_ids

src/otko/commands/series_and_patterns.py

@@ -31,9 +31,7 @@ class AddTimeSeriesCommand(ProjectCommand):
         self._notify()
 
     def undo(self) -> None:
-        self.project.time_series[:] = [
+        self.project.time_series[:] = [t for t in self.project.time_series if t.id != self._ts.id]
-            t for t in self.project.time_series if t.id != self._ts.id
-        ]
         self._notify()
 
 

src/otko/commands/transforms.py

@@ -45,9 +45,9 @@ class MoveNodesCommand(ProjectCommand):
         for i, n in enumerate(self.project.nodes):
             if n.id in self._node_ids:
                 self._previous[n.id] = n.coords
-                self.project.nodes[i] = n.model_copy(update={
+                self.project.nodes[i] = n.model_copy(
-                    "coords": (n.coords[0] + dx, n.coords[1] + dy, n.coords[2] + dz)
+                    update={"coords": (n.coords[0] + dx, n.coords[1] + dy, n.coords[2] + dz)}
-                })
+                )
         self._notify()
 
     def undo(self) -> None:
@@ -84,7 +84,8 @@ class ReplicateCommand(ProjectCommand):
         # Snapshot the source nodes/elements once (won't change during redo).
         src_nodes = [n for n in self.project.nodes if n.id in self._node_ids]
         src_elements = [
-            e for e in self.project.elements
+            e
+            for e in self.project.elements
             if e.id in self._element_ids and all(nid in self._node_ids for nid in e.nodes)
         ]
         next_node_id = self.project.next_node_id()
@@ -95,30 +96,34 @@ class ReplicateCommand(ProjectCommand):
         for k in range(1, self._n_copies + 1):
             mapping: dict[int, int] = {}
             for orig in src_nodes:
-                new_node = orig.model_copy(update={
+                new_node = orig.model_copy(
-                    "id": next_node_id,
+                    update={
-                    "coords": (orig.coords[0] + k * dx,
+                        "id": next_node_id,
-                               orig.coords[1] + k * dy,
+                        "coords": (
-                               orig.coords[2] + k * dz),
+                            orig.coords[0] + k * dx,
-                })
+                            orig.coords[1] + k * dy,
+                            orig.coords[2] + k * dz,
+                        ),
+                    }
+                )
                 self.project.nodes.append(new_node)
                 self._added_node_ids.add(next_node_id)
                 mapping[orig.id] = next_node_id
                 next_node_id += 1
             for orig in src_elements:
-                new_elem = orig.model_copy(update={
+                new_elem = orig.model_copy(
-                    "id": next_elem_id,
+                    update={
-                    "nodes": tuple(mapping[nid] for nid in orig.nodes),
+                        "id": next_elem_id,
-                })
+                        "nodes": tuple(mapping[nid] for nid in orig.nodes),
+                    }
+                )
                 self.project.elements.append(new_elem)
                 self._added_element_ids.add(next_elem_id)
                 next_elem_id += 1
         self._notify()
 
     def undo(self) -> None:
-        self.project.nodes[:] = [
+        self.project.nodes[:] = [n for n in self.project.nodes if n.id not in self._added_node_ids]
-            n for n in self.project.nodes if n.id not in self._added_node_ids
-        ]
         self.project.elements[:] = [
             e for e in self.project.elements if e.id not in self._added_element_ids
         ]
@@ -166,7 +171,8 @@ class MirrorCommand(ProjectCommand):
     def redo(self) -> None:
         src_nodes = [n for n in self.project.nodes if n.id in self._node_ids]
         src_elements = [
-            e for e in self.project.elements
+            e
+            for e in self.project.elements
             if e.id in self._element_ids and all(nid in self._node_ids for nid in e.nodes)
         ]
         next_node_id = self.project.next_node_id()
@@ -176,28 +182,30 @@ class MirrorCommand(ProjectCommand):
         mapping: dict[int, int] = {}
 
         for orig in src_nodes:
-            new_node = orig.model_copy(update={
+            new_node = orig.model_copy(
-                "id": next_node_id,
+                update={
-                "coords": self._reflect(orig.coords, self._plane),
+                    "id": next_node_id,
-            })
+                    "coords": self._reflect(orig.coords, self._plane),
+                }
+            )
             self.project.nodes.append(new_node)
             self._added_node_ids.add(next_node_id)
             mapping[orig.id] = next_node_id
             next_node_id += 1
         for orig in src_elements:
-            new_elem = orig.model_copy(update={
+            new_elem = orig.model_copy(
-                "id": next_elem_id,
+                update={
-                "nodes": tuple(mapping[nid] for nid in orig.nodes),
+                    "id": next_elem_id,
-            })
+                    "nodes": tuple(mapping[nid] for nid in orig.nodes),
+                }
+            )
             self.project.elements.append(new_elem)
             self._added_element_ids.add(next_elem_id)
             next_elem_id += 1
         self._notify()
 
     def undo(self) -> None:
-        self.project.nodes[:] = [
+        self.project.nodes[:] = [n for n in self.project.nodes if n.id not in self._added_node_ids]
-            n for n in self.project.nodes if n.id not in self._added_node_ids
-        ]
         self.project.elements[:] = [
             e for e in self.project.elements if e.id not in self._added_element_ids
         ]

src/otko/core/__init__.py

@@ -50,6 +50,8 @@ from otko.core.loads import (
     ConstantTimeSeries,
     ImposedSupportMotionPattern,
     LinearTimeSeries,
+    LoadCombination,
+    LoadCombinationItem,
     LoadPattern,
     NodalLoad,
     PathTimeSeries,
@@ -165,6 +167,8 @@ __all__ = [
     "PlainLoadPattern",
     "UniformExcitationPattern",
     "ImposedSupportMotionPattern",
+    "LoadCombination",
+    "LoadCombinationItem",
     "NodalLoad",
     "UniformElementLoad",
     "ResponseSpectrum",

src/otko/core/_base.py

@@ -16,11 +16,13 @@ class Entity(BaseModel):
     """Base class for every persisted domain object."""
 
     model_config = ConfigDict(
-        frozen=False,            # individual setters allowed; we lock at the Project boundary
+        frozen=False,  # individual setters allowed; we lock at the Project boundary
-        extra="forbid",          # unknown JSON keys are an error, not a silent ignore
+        extra="forbid",  # unknown JSON keys are an error, not a silent ignore
         validate_assignment=True,
         populate_by_name=True,
     )
 
-    id: PositiveInt = Field(..., description="Unique tag within its kind. Used as the OpenSees tag.")
+    id: PositiveInt = Field(
+        ..., description="Unique tag within its kind. Used as the OpenSees tag."
+    )
     name: str = Field(default="", description="Optional human-readable label.")

src/otko/core/analysis/__init__.py

@@ -83,7 +83,8 @@ class TransientCase(Entity):
     constraints: str = "Plain"
     integrator: str = "Newmark"
     integrator_params: tuple[float, float] = Field(
-        default=(0.5, 0.25), description="Newmark gamma, beta (default = average acceleration).",
+        default=(0.5, 0.25),
+        description="Newmark gamma, beta (default = average acceleration).",
     )
     algorithm: str = "Newton"
     test: str = "NormDispIncr"
@@ -100,7 +101,7 @@ class TransientCase(Entity):
     rayleigh_beta_k: float = Field(
         default=0.0,
         description="Stiffness-proportional βK on CURRENT/tangent stiffness — "
-                    "``rayleigh`` slot 2 (damps high frequencies).",
+        "``rayleigh`` slot 2 (damps high frequencies).",
     )
     rayleigh_beta_k_init: float = Field(
         default=0.0,
@@ -114,11 +115,11 @@ class TransientCase(Entity):
     )
     rayleigh_beta_k_comm: float = Field(
         default=0.0,
-        description="Stiffness-proportional βK on COMMITTED stiffness — "
+        description="Stiffness-proportional βK on COMMITTED stiffness — " "``rayleigh`` slot 4.",
-                    "``rayleigh`` slot 4.",
     )
     rayleigh_mode1_damping: float | None = Field(
-        default=None, ge=0.0,
+        default=None,
+        ge=0.0,
         description=(
             "If set, βK is computed as 2·ζ/√λ₁ (first-mode eigenvalue) and "
             "overrides ``rayleigh_beta_k``. ``rayleigh_alpha_m`` still applies."
@@ -195,7 +196,7 @@ class PushoverCase(Entity):
     base_nodes: list[PositiveInt] = Field(
         default_factory=list,
         description="Nodes whose reactions sum into the 'base shear' for the curve. "
-                    "Leave empty to use every restrained node in the project.",
+        "Leave empty to use every restrained node in the project.",
     )
     system: str = "BandGeneral"
     constraints: str = "Plain"
@@ -244,19 +245,26 @@ class ResponseSpectrumCase(Entity):
 
     type: Literal["ResponseSpectrum"] = "ResponseSpectrum"
     modal_case_id: PositiveInt = Field(
-        ..., description="ID of the ModalCase whose mode shapes drive this analysis.",
+        ...,
+        description="ID of the ModalCase whose mode shapes drive this analysis.",
     )
     spectrum_id: PositiveInt = Field(
-        ..., description="ID of the ResponseSpectrum to apply.",
+        ...,
+        description="ID of the ResponseSpectrum to apply.",
     )
     direction: int = Field(
-        ..., ge=1, le=6, description="DOF direction (1..6) for the seismic excitation.",
+        ...,
+        ge=1,
+        le=6,
+        description="DOF direction (1..6) for the seismic excitation.",
     )
     combination: Literal["SRSS", "CQC"] = "SRSS"
     damping_ratio: float | None = Field(
-        default=None, ge=0.0, le=1.0,
+        default=None,
+        ge=0.0,
+        le=1.0,
         description="Override the spectrum's damping for CQC correlation. "
-                    "Defaults to the spectrum's damping_ratio.",
+        "Defaults to the spectrum's damping_ratio.",
     )
 
 

src/otko/core/defaults.py

@@ -159,12 +159,8 @@ def ensure_default_timeseries_and_pattern(
         if existing is not None:
             return existing
     pattern_name = name or DEFAULT_PATTERN_NAME
-    ts = make_default_time_series(
+    ts = make_default_time_series(project.next_time_series_id(), kind=ts_kind, name=pattern_name)
-        project.next_time_series_id(), kind=ts_kind, name=pattern_name
-    )
     project.time_series.append(ts)
-    pattern = make_default_pattern(
+    pattern = make_default_pattern(project.next_pattern_id(), ts.id, name=pattern_name)
-        project.next_pattern_id(), ts.id, name=pattern_name
-    )
     project.load_patterns.append(pattern)
     return pattern

src/otko/core/geometry/elements.py

@@ -91,7 +91,9 @@ class ZeroLengthElement(Entity):
     type: Literal["ZeroLength"] = "ZeroLength"
     nodes: tuple[PositiveInt, PositiveInt]
     material_ids: tuple[PositiveInt, ...] = Field(..., min_length=1)
-    dofs: tuple[int, ...] = Field(..., min_length=1, description="DOF directions, 1-indexed (1..6).")
+    dofs: tuple[int, ...] = Field(
+        ..., min_length=1, description="DOF directions, 1-indexed (1..6)."
+    )
     do_rayleigh: bool = Field(
         default=False,
         description=(
@@ -121,7 +123,9 @@ class ZeroLengthSectionElement(Entity):
 
     type: Literal["ZeroLengthSection"] = "ZeroLengthSection"
     nodes: tuple[PositiveInt, PositiveInt]
-    section_id: PositiveInt = Field(..., description="Section attached to the two coincident nodes.")
+    section_id: PositiveInt = Field(
+        ..., description="Section attached to the two coincident nodes."
+    )
 
 
 class BeamWithHingesElement(Entity):
@@ -179,7 +183,8 @@ class QuadElement(Entity):
         description="Surface pressure applied over the element (force / area).",
     )
     rho: float = Field(
-        default=0.0, ge=0.0,
+        default=0.0,
+        ge=0.0,
         description="Mass density override (kip·s²/in⁴). Leave 0 to use material rho.",
     )
     b1: float = Field(

src/otko/core/geometry/grid.py

@@ -87,10 +87,12 @@ class GridSystem(BaseModel):
                         if isinstance(v, dict):
                             records.append(v)
                         else:
-                            records.append({
+                            records.append(
-                                "id": f"{prefix}{i + 1}",
+                                {
-                                "ordinate": float(v),
+                                    "id": f"{prefix}{i + 1}",
-                            })
+                                    "ordinate": float(v),
+                                }
+                            )
                     data[grid_key] = records
         return data
 
@@ -121,21 +123,21 @@ class GridSystem(BaseModel):
 
     def bounds(self) -> tuple[tuple[float, float], tuple[float, float], tuple[float, float]]:
         """Return ((xmin, xmax), (ymin, ymax), (zmin, zmax)) spanning the grid."""
+
         def span(vs: list[float]) -> tuple[float, float]:
             if not vs:
                 return (0.0, 0.0)
             return (vs[0], vs[-1])
+
         return span(self.x_lines), span(self.y_lines), span(self.z_lines)
 
 
 def make_grid_lines(
-    axis: Literal["X", "Y", "Z"], ordinates: list[float],
+    axis: Literal["X", "Y", "Z"],
+    ordinates: list[float],
 ) -> list[GridLine]:
     """Helper: build default-metadata GridLine records from flat ordinates."""
-    return [
+    return [GridLine(id=f"{axis}{i + 1}", ordinate=float(v)) for i, v in enumerate(ordinates)]
-        GridLine(id=f"{axis}{i + 1}", ordinate=float(v))
-        for i, v in enumerate(ordinates)
-    ]
 
 
 class CoordinateSystem(BaseModel):
@@ -160,9 +162,9 @@ class CoordinateSystem(BaseModel):
         cz, sz = math.cos(rz), math.sin(rz)
         # Rz · Ry · Rx  (applied right-to-left: Rx first, then Ry, then Rz).
         return [
-            [cy * cz,  sx * sy * cz - cx * sz,  cx * sy * cz + sx * sz],
+            [cy * cz, sx * sy * cz - cx * sz, cx * sy * cz + sx * sz],
-            [cy * sz,  sx * sy * sz + cx * cz,  cx * sy * sz - sx * cz],
+            [cy * sz, sx * sy * sz + cx * cz, cx * sy * sz - sx * cz],
-            [-sy,      sx * cy,                  cx * cy],
+            [-sy, sx * cy, cx * cy],
         ]
 
     def local_to_world(self, p_local: tuple[float, float, float]) -> tuple[float, float, float]:

src/otko/core/loads/__init__.py

@@ -14,7 +14,7 @@ from __future__ import annotations
 
 from typing import Annotated, Literal, Union
 
-from pydantic import BaseModel, ConfigDict, Field, PositiveInt
+from pydantic import BaseModel, ConfigDict, Field, PositiveInt, model_validator
 
 from otko.core._base import Entity
 
@@ -77,15 +77,19 @@ class ResponseSpectrum(Entity):
 
     type: Literal["ResponseSpectrum"] = "ResponseSpectrum"
     periods: list[float] = Field(
-        ..., min_length=2,
+        ...,
+        min_length=2,
         description="Periods (s), strictly increasing.",
     )
     accelerations: list[float] = Field(
-        ..., min_length=2,
+        ...,
+        min_length=2,
         description="Spectral pseudo-accelerations (length must match `periods`).",
     )
     damping_ratio: float = Field(
-        default=0.05, ge=0.0, le=1.0,
+        default=0.05,
+        ge=0.0,
+        le=1.0,
         description="Modal damping ratio the spectrum was built for.",
     )
 
@@ -185,12 +189,66 @@ class ImposedSupportMotionPattern(Entity):
     direction: int = Field(..., ge=1, le=6, description="DOF direction (1..6).")
     disp_series_id: PositiveInt
     node_ids: list[int] = Field(
-        ..., min_length=1,
+        ...,
+        min_length=1,
         description="Support nodes driven by the motion (each restrained in `direction`).",
     )
     factor: float = 1.0
 
 
+# ──────────────────────────── Load combinations ────────────────────────────
+class LoadCombinationItem(BaseModel):
+    """One term of a case-result load combination: ``factor × results(case_id)``."""
+
+    model_config = ConfigDict(extra="forbid", validate_assignment=True)
+
+    case_id: PositiveInt = Field(..., description="AnalysisCase whose results are scaled.")
+    factor: float = Field(default=1.0, description="Scale applied to that case's results.")
+
+
+class LoadCombination(Entity):
+    """Named combination of *completed* analysis-case results (post-processing).
+
+    A ``Linear`` combination is the weighted sum
+    ``Σ factor_i × results(case_i)`` over nodal displacements, reactions,
+    and element forces. Valid for linear-elastic static superposition
+    (e.g. ``1.2×Dead + 1.6×Live``) — combining nonlinear, transient, or
+    modal results is rejected at evaluation time, not here, so projects
+    stay loadable while the UI guides the user.
+
+    An ``Envelope`` combination reports the per-DOF, per-step maximum and
+    minimum across the factored terms instead of their sum.
+    """
+
+    type: Literal["LoadCombination"] = "LoadCombination"
+    kind: Literal["Linear", "Envelope"] = Field(
+        default="Linear", description="Linear = weighted sum; Envelope = per-DOF max/min."
+    )
+    items: list[LoadCombinationItem] = Field(
+        ..., min_length=1, description="Terms of the combination (≥1; ≥2 recommended)."
+    )
+
+    @model_validator(mode="after")
+    def _check_items(self) -> "LoadCombination":
+        """Reject duplicate case ids and non-finite factors."""
+        import math
+
+        seen: set[int] = set()
+        dup: set[int] = set()
+        for item in self.items:
+            if item.case_id in seen:
+                dup.add(item.case_id)
+            seen.add(item.case_id)
+            if not math.isfinite(item.factor):
+                raise ValueError(
+                    f"LoadCombination {self.id}: factor for case {item.case_id} "
+                    f"must be finite, got {item.factor!r}."
+                )
+        if dup:
+            raise ValueError(f"LoadCombination {self.id}: duplicate case ids: {sorted(dup)}.")
+        return self
+
+
 LoadPattern = Annotated[
     Union[PlainLoadPattern, UniformExcitationPattern, ImposedSupportMotionPattern],
     Field(discriminator="type"),

src/otko/core/materials/__init__.py

@@ -58,7 +58,9 @@ class Steel02(Entity):
     Fy: PositiveFloat
     E0: PositiveFloat
     b: float = Field(..., ge=0.0, le=1.0)
-    R0: float = Field(default=18.0, description="Bauschinger curvature parameter (typically 10–20).")
+    R0: float = Field(
+        default=18.0, description="Bauschinger curvature parameter (typically 10–20)."
+    )
     cR1: float = Field(default=0.925)
     cR2: float = Field(default=0.15)
 
@@ -83,7 +85,10 @@ class Concrete02(Entity):
     fpcu: float = Field(..., le=0.0)
     epsU: float = Field(..., lt=0.0)
     lambda_: float = Field(
-        ..., alias="lambda", ge=0.0, le=1.0,
+        ...,
+        alias="lambda",
+        ge=0.0,
+        le=1.0,
         description="Ratio between unloading slope at epscu and initial slope.",
     )
     ft: PositiveFloat = Field(..., description="Tensile strength.")
@@ -108,15 +113,19 @@ class Concrete04(Entity):
     epscu: float = Field(..., lt=0.0, description="Ultimate compressive strain (negative).")
     Ec: PositiveFloat = Field(..., description="Initial tangent modulus.")
     fct: float | None = Field(
-        default=None, gt=0.0,
+        default=None,
+        gt=0.0,
         description="Maximum tensile strength. Omit for no-tension model.",
     )
     et: float | None = Field(
-        default=None, gt=0.0,
+        default=None,
+        gt=0.0,
         description="Ultimate tensile strain. Required when fct is given.",
     )
     beta: float | None = Field(
-        default=None, ge=0.0, le=1.0,
+        default=None,
+        ge=0.0,
+        le=1.0,
         description="Cyclic degradation factor on unloading stiffness. Requires fct and et.",
     )
 
@@ -138,7 +147,8 @@ class ElasticPP(Entity):
     E: PositiveFloat
     epsy_pos: PositiveFloat = Field(..., description="Yield strain in tension.")
     epsy_neg: float | None = Field(
-        default=None, description="Yield strain in compression (negative); defaults to -epsy_pos.",
+        default=None,
+        description="Yield strain in compression (negative); defaults to -epsy_pos.",
     )
     eps0: float = Field(default=0.0, description="Initial strain.")
 
@@ -176,7 +186,8 @@ class HystereticMaterial(Entity):
     d1: float = Field(default=0.0, ge=0.0, description="Ductility damage, linear portion.")
     d2: float = Field(default=0.0, ge=0.0, description="Ductility damage, cumulative portion.")
     beta: float = Field(
-        default=0.0, ge=0.0,
+        default=0.0,
+        ge=0.0,
         description="Unloading-stiffness degradation (0 = no degradation).",
     )
 
@@ -206,7 +217,8 @@ class HystereticSM(Entity):
 
     type: Literal["HystereticSM"] = "HystereticSM"
     pos_env: list[tuple[float, float]] = Field(
-        ..., min_length=1,
+        ...,
+        min_length=1,
         description="Positive envelope (force, deformation) pairs, force first.",
     )
     neg_env: list[tuple[float, float]] = Field(

src/otko/core/project.py

@@ -30,7 +30,7 @@ from otko.core.geometry import (
     Node,
     default_global_system,
 )
-from otko.core.loads import LoadPattern, ResponseSpectrum, TimeSeries
+from otko.core.loads import LoadCombination, LoadPattern, ResponseSpectrum, TimeSeries
 from otko.core.materials import Material
 from otko.core.sections import Section
 from otko.core.units import UnitSystem
@@ -110,6 +110,7 @@ _INDEX_KINDS: tuple[str, ...] = (
     "load_patterns",
     "spectra",
     "analyses",
+    "combinations",
 )
 
 
@@ -155,11 +156,13 @@ class Project(BaseModel):
         """
         if isinstance(data, dict) and "grid_system" in data and "coord_systems" not in data:
             legacy = data.pop("grid_system")
-            data["coord_systems"] = [{
+            data["coord_systems"] = [
-                "name": "Global",
+                {
-                "coord": {},
+                    "name": "Global",
-                "grid": legacy,
+                    "coord": {},
-            }]
+                    "grid": legacy,
+                }
+            ]
         return data
 
     @model_validator(mode="after")
@@ -203,10 +206,12 @@ class Project(BaseModel):
                 return
         # No Global system yet — create one with this grid.
         from otko.core.geometry import CoordinateGridSystem
+
         self.coord_systems.insert(
             0,
             CoordinateGridSystem(name="Global", grid=new_grid),
         )
+
     sections: list[Section] = Field(default_factory=list)
     elements: list[Element] = Field(default_factory=list)
     mp_constraints: list[EqualDOFConstraint] = Field(default_factory=list)
@@ -214,6 +219,7 @@ class Project(BaseModel):
     load_patterns: list[LoadPattern] = Field(default_factory=list)
     spectra: list[ResponseSpectrum] = Field(default_factory=list)
     analyses: list[AnalysisCase] = Field(default_factory=list)
+    combinations: list[LoadCombination] = Field(default_factory=list)
 
     # ─────────────────── invariants ───────────────────
     @model_validator(mode="after")
@@ -236,6 +242,7 @@ class Project(BaseModel):
             ("time series", self.time_series),
             ("load pattern", self.load_patterns),
             ("analysis", self.analyses),
+            ("combination", self.combinations),
         ):
             ids = [it.id for it in items]
             if len(ids) != len(set(ids)):
@@ -270,6 +277,10 @@ class Project(BaseModel):
     def next_analysis_id(self) -> int:
         return self._next_id(self.analyses)
 
+    def next_combination_id(self) -> int:
+        """Return the next free load-combination id."""
+        return self._next_id(self.combinations)
+
     # ─────────────────── lookups ───────────────────
     def node(self, node_id: PositiveInt) -> Node:
         return cast(Node, self._lookup("nodes", self.nodes, node_id, "node"))
@@ -283,6 +294,20 @@ class Project(BaseModel):
     def element(self, element_id: PositiveInt) -> Element:
         return cast(Element, self._lookup("elements", self.elements, element_id, "element"))
 
+    def combination(self, combination_id: PositiveInt) -> LoadCombination:
+        """Return the load combination with ``combination_id``.
+
+        Args:
+            combination_id: Combination tag to look up.
+
+        Raises:
+            KeyError: if no combination carries that id.
+        """
+        return cast(
+            LoadCombination,
+            self._lookup("combinations", self.combinations, combination_id, "combination"),
+        )
+
     def _lookup(self, kind: str, items: list[Any], target_id: int, label: str) -> Any:
         """Return the entity with ``target_id`` from ``items`` in O(1) time.
 
@@ -395,5 +420,14 @@ class Project(BaseModel):
                         f"uses invalid DOF {dof} for ndf={self.ndf}."
                     )
 
+        analysis_ids = {c.id for c in self.analyses}
+        for combo in self.combinations:
+            for item in combo.items:
+                if item.case_id not in analysis_ids:
+                    problems.append(
+                        f"Combination {combo.id} refers to missing analysis case "
+                        f"{item.case_id}."
+                    )
+
         if problems:
             raise ValueError("Reference validation failed:\n  - " + "\n  - ".join(problems))

src/otko/core/sections/__init__.py

@@ -75,8 +75,12 @@ class ElasticSection(Entity):
     A: PositiveFloat
     Iz: PositiveFloat = Field(..., description="Moment of inertia about local z-axis.")
     Iy: PositiveFloat | None = Field(default=None, description="Required for 3D frames.")
-    G: PositiveFloat | None = Field(default=None, description="Shear modulus; required for 3D frames.")
+    G: PositiveFloat | None = Field(
-    J: PositiveFloat | None = Field(default=None, description="Torsional constant; required for 3D frames.")
+        default=None, description="Shear modulus; required for 3D frames."
+    )
+    J: PositiveFloat | None = Field(
+        default=None, description="Torsional constant; required for 3D frames."
+    )
     shape: SectionShape | None = Field(
         default=None,
         description=(
@@ -198,7 +202,8 @@ class AggregatorDOF(BaseModel):
 
     material_id: PositiveInt
     dof: Literal["P", "Mz", "My", "Vy", "Vz", "T"] = Field(
-        ..., description="Section DOF code (OpenSees section-deformation names).",
+        ...,
+        description="Section DOF code (OpenSees section-deformation names).",
     )
 
 

src/otko/core/units.py

@@ -42,30 +42,46 @@ class UnitLabels:
     label axes without hard-coding any particular set of units.
     """
 
-    length: str           # "m", "mm", "in", "ft"
+    length: str  # "m", "mm", "in", "ft"
-    force: str            # "N", "kip"
+    force: str  # "N", "kip"
-    moment: str           # "N·m", "kip·in"
+    moment: str  # "N·m", "kip·in"
-    stress: str           # "Pa", "MPa", "ksi", "ksf"
+    stress: str  # "Pa", "MPa", "ksi", "ksf"
-    curvature: str        # "1/m", "1/in", …
+    curvature: str  # "1/m", "1/in", …
-    rotation: str         # "rad" (always, no unit variants in practice)
+    rotation: str  # "rad" (always, no unit variants in practice)
 
 
 _LABELS: dict[UnitSystem, UnitLabels] = {
     UnitSystem.SI_M_N: UnitLabels(
-        length="m", force="N", moment="N·m",
+        length="m",
-        stress="Pa", curvature="1/m", rotation="rad",
+        force="N",
+        moment="N·m",
+        stress="Pa",
+        curvature="1/m",
+        rotation="rad",
     ),
     UnitSystem.SI_MM_N: UnitLabels(
-        length="mm", force="N", moment="N·mm",
+        length="mm",
-        stress="MPa", curvature="1/mm", rotation="rad",
+        force="N",
+        moment="N·mm",
+        stress="MPa",
+        curvature="1/mm",
+        rotation="rad",
     ),
     UnitSystem.US_FT_KIP: UnitLabels(
-        length="ft", force="kip", moment="kip·ft",
+        length="ft",
-        stress="ksf", curvature="1/ft", rotation="rad",
+        force="kip",
+        moment="kip·ft",
+        stress="ksf",
+        curvature="1/ft",
+        rotation="rad",
     ),
     UnitSystem.US_IN_KIP: UnitLabels(
-        length="in", force="kip", moment="kip·in",
+        length="in",
-        stress="ksi", curvature="1/in", rotation="rad",
+        force="kip",
+        moment="kip·in",
+        stress="ksi",
+        curvature="1/in",
+        rotation="rad",
     ),
 }
 

src/otko/services/__init__.py

@@ -6,6 +6,12 @@ worker lives in ``qt_workers`` and is the only module here that
 imports PySide6.
 """
 
+from otko.services.combinations import (
+    EnvelopeResults,
+    combine_static_results,
+    envelope_static_results,
+    evaluate_combination,
+)
 from otko.services.export import export_opspy, export_tcl
 from otko.services.material_tester import (
     CyclicSegment,
@@ -28,12 +34,16 @@ from otko.services.results import (
 __all__ = [
     "PROJECT_FILE_SUFFIX",
     "CyclicSegment",
+    "EnvelopeResults",
     "LoadProtocol",
     "MaterialTestResult",
     "ModalResults",
     "OpenSeesRunner",
     "StaticResults",
     "TransientResults",
+    "combine_static_results",
+    "envelope_static_results",
+    "evaluate_combination",
     "export_opspy",
     "export_tcl",
     "load_project",

src/otko/services/_emit.py

@@ -409,7 +409,10 @@ class OpenSeesEmitter:
                 if el.consistent_mass:
                     ebc_args.append("-cMass")
                 ops.element(
-                    "elasticBeamColumn", el.id, *el.nodes, *ebc_args,
+                    "elasticBeamColumn",
+                    el.id,
+                    *el.nodes,
+                    *ebc_args,
                 )
             case ForceBeamColumn():
                 tag = self._element_geom_transf_tag[el.id]
@@ -430,9 +433,13 @@ class OpenSeesEmitter:
                 ops.element("dispBeamColumn", el.id, *el.nodes, tag, el.id)
             case ZeroLengthElement():
                 zl_args: list[Any] = [
-                    "zeroLength", el.id, *el.nodes,
+                    "zeroLength",
-                    "-mat", *el.material_ids,
+                    el.id,
-                    "-dir", *el.dofs,
+                    *el.nodes,
+                    "-mat",
+                    *el.material_ids,
+                    "-dir",
+                    *el.dofs,
                 ]
                 # ``-doRayleigh 1`` only when requested (default off, matching
                 # OpenSees' zeroLength default) — so an isolator can opt its
@@ -647,15 +654,27 @@ class OpenSeesEmitter:
             )
         vel = np.gradient(np.asarray(ts.values, dtype=float), ts.dt)
         ops.timeSeries(
-            "Path", vel_tag, "-dt", ts.dt, "-values", *vel.tolist(),
+            "Path",
-            "-factor", ts.factor,
+            vel_tag,
+            "-dt",
+            ts.dt,
+            "-values",
+            *vel.tolist(),
+            "-factor",
+            ts.factor,
         )
         for nid in pat.node_ids:
             ops.remove("sp", nid, pat.direction)
         ops.pattern("MultipleSupport", pat.id)
         ops.groundMotion(
-            pat.id, "Plain", "-disp", pat.disp_series_id, "-vel", vel_tag,
+            pat.id,
-            "-fact", pat.factor,
+            "Plain",
+            "-disp",
+            pat.disp_series_id,
+            "-vel",
+            vel_tag,
+            "-fact",
+            pat.factor,
         )
         for nid in pat.node_ids:
             ops.imposedMotion(nid, pat.direction, pat.id)

src/otko/services/animation_export.py

@@ -55,8 +55,7 @@ def export_mode_shape_video(
     else:
         # MP4 / WebM use FFmpeg backend. macro_block_size=1 disables
         # the auto-resize-for-h264 pass (still works on modern players).
-        iio.imwrite(output_path, frames, fps=fps, codec="libx264",
+        iio.imwrite(output_path, frames, fps=fps, codec="libx264", macro_block_size=1)
-                    macro_block_size=1)
 
 
 def export_time_history_video(
@@ -94,5 +93,4 @@ def export_time_history_video(
     if suffix == ".gif":
         iio.imwrite(output_path, frames, duration=1.0 / fps, loop=0)
     else:
-        iio.imwrite(output_path, frames, fps=fps, codec="libx264",
+        iio.imwrite(output_path, frames, fps=fps, codec="libx264", macro_block_size=1)
-                    macro_block_size=1)

src/otko/services/deformation.py

@@ -24,7 +24,7 @@ class DeformationSource:
     displacements to PyVista point arrays.
     """
 
-    displacements: np.ndarray         # shape (n_nodes, 3) — x, y, z components
+    displacements: np.ndarray  # shape (n_nodes, 3) — x, y, z components
     node_id_to_row: dict[int, int]
     scale: float = 1.0
 
@@ -38,8 +38,11 @@ class DeformationSource:
 
 
 def static_to_deformation(
-    project: Project, results: StaticResults, *,
+    project: Project,
-    step: int = -1, scale: float = 1.0,
+    results: StaticResults,
+    *,
+    step: int = -1,
+    scale: float = 1.0,
 ) -> DeformationSource:
     """Build a DeformationSource from a static analysis's nodal displacements.
 
@@ -57,13 +60,16 @@ def static_to_deformation(
         # Take only translation DOFs (first 2 in 2D, first 3 in 3D).
         n_take = min(3, snapshot.shape[0])
         disp[node_id_to_row[nid], :n_take] = snapshot[:n_take]
-    return DeformationSource(displacements=disp,
+    return DeformationSource(displacements=disp, node_id_to_row=node_id_to_row, scale=scale)
-                             node_id_to_row=node_id_to_row, scale=scale)
 
 
 def modal_to_deformation(
-    project: Project, results: ModalResults, *,
+    project: Project,
-    mode: int = 0, scale: float = 1.0, phase: float = 1.0,
+    results: ModalResults,
+    *,
+    mode: int = 0,
+    scale: float = 1.0,
+    phase: float = 1.0,
 ) -> DeformationSource:
     """Build a DeformationSource from a modal analysis's mode shape.
 
@@ -78,10 +84,9 @@ def modal_to_deformation(
 
     mode_number = mode + 1  # mode_shapes is 1-indexed
     if mode_number not in results.mode_shapes:
-        return DeformationSource(displacements=disp,
+        return DeformationSource(displacements=disp, node_id_to_row=node_id_to_row, scale=scale)
-                                 node_id_to_row=node_id_to_row, scale=scale)
 
-    eigvec = results.mode_shapes[mode_number]   # dict: nid → np.ndarray of DOF values
+    eigvec = results.mode_shapes[mode_number]  # dict: nid → np.ndarray of DOF values
     for nid, vec in eigvec.items():
         if nid not in node_id_to_row:
             continue
@@ -101,12 +106,15 @@ def modal_to_deformation(
         norm_factor = (bbox * 0.05) / max_amp
         disp *= norm_factor
 
-    return DeformationSource(displacements=disp,
+    return DeformationSource(displacements=disp, node_id_to_row=node_id_to_row, scale=scale)
-                             node_id_to_row=node_id_to_row, scale=scale)
 
 
 def transient_to_deformation_at_step(
-    project: Project, results, *, step: int = 0, scale: float = 1.0,
+    project: Project,
+    results,
+    *,
+    step: int = 0,
+    scale: float = 1.0,
 ) -> DeformationSource:
     """Build a DeformationSource from a transient analysis at one step.
 
@@ -139,8 +147,7 @@ def transient_to_deformation_at_step(
         norm_factor = (bbox * 0.10) / max_amp
         disp *= norm_factor
 
-    return DeformationSource(displacements=disp,
+    return DeformationSource(displacements=disp, node_id_to_row=node_id_to_row, scale=scale)
-                             node_id_to_row=node_id_to_row, scale=scale)
 
 
 def linear_static_auto_scale(project: Project, results: StaticResults) -> float:

src/otko/services/element_forces.py

@@ -41,27 +41,36 @@ from otko.services.results import StaticResults
 class ForceComponent(Enum):
     """Which force component to plot."""
 
-    N = "N"        # axial
+    N = "N"  # axial
-    V2 = "V2"      # shear in local y (in-plane shear for 2D)
+    V2 = "V2"  # shear in local y (in-plane shear for 2D)
-    V3 = "V3"      # shear in local z
+    V3 = "V3"  # shear in local z
-    T = "T"        # torsion
+    T = "T"  # torsion
-    M2 = "M2"      # moment about local y
+    M2 = "M2"  # moment about local y
-    M3 = "M3"      # moment about local z (in-plane moment for 2D)
+    M3 = "M3"  # moment about local z (in-plane moment for 2D)
 
 
 # Map (component, end) → index into the local-force vector for 3D and 2D.
 _INDEX_3D = {
-    (ForceComponent.N,  "i"): 0,  (ForceComponent.N,  "j"): 6,
+    (ForceComponent.N, "i"): 0,
-    (ForceComponent.V2, "i"): 1,  (ForceComponent.V2, "j"): 7,
+    (ForceComponent.N, "j"): 6,
-    (ForceComponent.V3, "i"): 2,  (ForceComponent.V3, "j"): 8,
+    (ForceComponent.V2, "i"): 1,
-    (ForceComponent.T,  "i"): 3,  (ForceComponent.T,  "j"): 9,
+    (ForceComponent.V2, "j"): 7,
-    (ForceComponent.M2, "i"): 4,  (ForceComponent.M2, "j"): 10,
+    (ForceComponent.V3, "i"): 2,
-    (ForceComponent.M3, "i"): 5,  (ForceComponent.M3, "j"): 11,
+    (ForceComponent.V3, "j"): 8,
+    (ForceComponent.T, "i"): 3,
+    (ForceComponent.T, "j"): 9,
+    (ForceComponent.M2, "i"): 4,
+    (ForceComponent.M2, "j"): 10,
+    (ForceComponent.M3, "i"): 5,
+    (ForceComponent.M3, "j"): 11,
 }
 _INDEX_2D = {
-    (ForceComponent.N,  "i"): 0,  (ForceComponent.N,  "j"): 3,
+    (ForceComponent.N, "i"): 0,
-    (ForceComponent.V2, "i"): 1,  (ForceComponent.V2, "j"): 4,
+    (ForceComponent.N, "j"): 3,
-    (ForceComponent.M3, "i"): 2,  (ForceComponent.M3, "j"): 5,
+    (ForceComponent.V2, "i"): 1,
+    (ForceComponent.V2, "j"): 4,
+    (ForceComponent.M3, "i"): 2,
+    (ForceComponent.M3, "j"): 5,
 }
 
 # Truss elements expose a different localForce layout than frames:
@@ -69,10 +78,12 @@ _INDEX_2D = {
 # 3D truss → 6-vector [N_i, 0, 0, N_j, 0, 0]
 # So we map only the N component; other components return None.
 _INDEX_TRUSS_2D = {
-    (ForceComponent.N, "i"): 0,  (ForceComponent.N, "j"): 2,
+    (ForceComponent.N, "i"): 0,
+    (ForceComponent.N, "j"): 2,
 }
 _INDEX_TRUSS_3D = {
-    (ForceComponent.N, "i"): 0,  (ForceComponent.N, "j"): 3,
+    (ForceComponent.N, "i"): 0,
+    (ForceComponent.N, "j"): 3,
 }
 
 
@@ -122,6 +133,7 @@ def extract_diagram_data(
 
     # Local import to avoid a cycle (element classes live in core.geometry).
     from otko.core import CorotTrussElement, TrussElement
+
     truss_types = (TrussElement, CorotTrussElement)
 
     for el in project.elements:

src/otko/services/export.py

@@ -35,7 +35,7 @@ from __future__ import annotations
 from collections.abc import Callable
 from typing import Any
 
-from otko import __version__
+from otko._const import OPENSEESPY_VERSION, __version__
 from otko.core import (
     ModalCase,
     Project,
@@ -49,7 +49,7 @@ from otko.services.opensees_runner import OpenSeesRunner
 __all__ = ["RecordingOps", "export_opspy", "export_tcl"]
 
 #: Pinned solver version written into every script header.
-PINNED_OPENSEESPY = "openseespy==3.8.0.0"
+PINNED_OPENSEESPY = f"openseespy=={OPENSEESPY_VERSION}"
 
 #: Recorded call triple: (ops method name, positional args, keyword args).
 RecordedCall = tuple[str, tuple[Any, ...], dict[str, Any]]
@@ -362,7 +362,7 @@ def export_opspy(project: Project, case_id: int | None = None) -> str:
             are appended after the model.
 
     Returns:
-        The script source. The header pins ``openseespy==3.8.0.0``,
+        The script source. The header pins the solver version,
         the OTKO version and the display units.
 
     Raises:

src/otko/services/material_tester.py

@@ -63,7 +63,9 @@ class CyclicSegment(BaseModel):
     current -> *compressive_peak* -> *tensile_peak* -> 0.
     """
 
-    compressive_peak: float = Field(..., lt=0.0, description="Target compressive strain (negative).")
+    compressive_peak: float = Field(
+        ..., lt=0.0, description="Target compressive strain (negative)."
+    )
     tensile_peak: float = Field(..., gt=0.0, description="Target tensile strain (positive).")
     n_cycles: PositiveInt = Field(1, description="Number of complete excursions to run.")
 
@@ -160,17 +162,35 @@ def _emit_uniaxial(ops: Any, mat: Any) -> None:
             ops.uniaxialMaterial("Steel01", mat.id, *args)
         case Steel02():
             ops.uniaxialMaterial(
-                "Steel02", mat.id, mat.Fy, mat.E0, mat.b, mat.R0, mat.cR1, mat.cR2,
+                "Steel02",
+                mat.id,
+                mat.Fy,
+                mat.E0,
+                mat.b,
+                mat.R0,
+                mat.cR1,
+                mat.cR2,
             )
         case Concrete01():
             ops.uniaxialMaterial(
-                "Concrete01", mat.id, mat.fpc, mat.epsc0, mat.fpcu, mat.epsU,
+                "Concrete01",
+                mat.id,
+                mat.fpc,
+                mat.epsc0,
+                mat.fpcu,
+                mat.epsU,
             )
         case Concrete02():
             ops.uniaxialMaterial(
-                "Concrete02", mat.id,
+                "Concrete02",
-                mat.fpc, mat.epsc0, mat.fpcu, mat.epsU,
+                mat.id,
-                mat.lambda_, mat.ft, mat.Ets,
+                mat.fpc,
+                mat.epsc0,
+                mat.fpcu,
+                mat.epsU,
+                mat.lambda_,
+                mat.ft,
+                mat.Ets,
             )
         case Concrete04():
             args = [mat.fpc, mat.epsc0, mat.epscu, mat.Ec]
@@ -187,10 +207,25 @@ def _emit_uniaxial(ops: Any, mat: Any) -> None:
             ops.uniaxialMaterial("ElasticPP", mat.id, *args)
         case HystereticMaterial():
             ops.uniaxialMaterial(
-                "Hysteretic", mat.id,
+                "Hysteretic",
-                mat.s1p, mat.e1p, mat.s2p, mat.e2p, mat.s3p, mat.e3p,
+                mat.id,
-                mat.s1n, mat.e1n, mat.s2n, mat.e2n, mat.s3n, mat.e3n,
+                mat.s1p,
-                mat.px, mat.py, mat.d1, mat.d2, mat.beta,
+                mat.e1p,
+                mat.s2p,
+                mat.e2p,
+                mat.s3p,
+                mat.e3p,
+                mat.s1n,
+                mat.e1n,
+                mat.s2n,
+                mat.e2n,
+                mat.s3n,
+                mat.e3n,
+                mat.px,
+                mat.py,
+                mat.d1,
+                mat.d2,
+                mat.beta,
             )
         case _:
             raise TypeError(f"Unsupported material type: {type(mat).__name__}")
@@ -239,10 +274,13 @@ def test_uniaxial_material(
     """
     if ops_module is None:
         import openseespy.opensees as _ops_default
+
         ops_module = _ops_default
 
     ops = ops_module
-    mat_name = getattr(material, "name", None) or str(getattr(material, "type", type(material).__name__))
+    mat_name = getattr(material, "name", None) or str(
+        getattr(material, "type", type(material).__name__)
+    )
 
     try:
         # Clear any leftover OpenSees state from a prior call or runner.

src/otko/services/peer_record.py

@@ -46,7 +46,8 @@ def parse_peer_record(path: str | Path) -> tuple[float, int, list[float]]:
             break
         # New NGA format: "3930 0.00500 NPTS, DT"
         m_new = re.match(
-            r"^(\d+)\s+([0-9.eE+\-]+)\s+NPTS\s*,\s*DT", stripped,
+            r"^(\d+)\s+([0-9.eE+\-]+)\s+NPTS\s*,\s*DT",
+            stripped,
         )
         if m_new:
             npts = int(m_new.group(1))
@@ -66,7 +67,7 @@ def parse_peer_record(path: str | Path) -> tuple[float, int, list[float]]:
             try:
                 values.append(float(tok))
             except ValueError:
-                pass   # skip stray tokens
+                pass  # skip stray tokens
     if not values:
         raise ValueError("Header parsed but no numeric data lines found.")
     return dt, npts, values

src/otko/services/qt_workers.py

@@ -32,8 +32,8 @@ class AnalysisWorker(QObject):
 
     started = Signal()
     log = Signal(str)
-    finished = Signal(object)        # emits StaticResults / ModalResults / TransientResults
+    finished = Signal(object)  # emits StaticResults / ModalResults / TransientResults
-    failed = Signal(str)             # human-readable error message + traceback
+    failed = Signal(str)  # human-readable error message + traceback
 
     def __init__(
         self,
@@ -52,8 +52,10 @@ class AnalysisWorker(QObject):
         """Slot to be invoked by ``QThread.started``."""
         self.started.emit()
         try:
-            self.log.emit(f"Building model: {len(self._project.nodes)} nodes, "
+            self.log.emit(
-                          f"{len(self._project.elements)} elements.")
+                f"Building model: {len(self._project.nodes)} nodes, "
+                f"{len(self._project.elements)} elements."
+            )
             runner = OpenSeesRunner(self._project)
             self.log.emit(f"Running case '{self._case.name}' ({type(self._case).__name__}) ...")
             results = runner.run(self._case, results_dir=self._results_dir)

src/otko/services/results.py

@@ -56,8 +56,8 @@ class PushoverResults:
     n_steps: int
     control_node: int
     control_dof: int
-    control_disp: np.ndarray          # shape (n_steps + 1,), includes t=0
+    control_disp: np.ndarray  # shape (n_steps + 1,), includes t=0
-    base_shear: np.ndarray            # shape (n_steps + 1,), signed
+    base_shear: np.ndarray  # shape (n_steps + 1,), signed
     node_disp: dict[int, np.ndarray] = field(default_factory=dict)
     """node_id → shape (n_steps + 1, ndf) displacement history."""
     element_forces: dict[int, np.ndarray] = field(default_factory=dict)
@@ -158,7 +158,7 @@ class ResponseSpectrumResults:
     case_id: int
     case_name: str
     direction: int
-    combination: str                    # "SRSS" or "CQC"
+    combination: str  # "SRSS" or "CQC"
     combined_disp: dict[int, np.ndarray] = field(default_factory=dict)
     """node_id → 3-vector of peak combined translational displacements."""
     modes: list = field(default_factory=list)

src/otko/services/section_bbox.py

@@ -52,8 +52,10 @@ def _angle_in_arc(angle: float, start: float, span: float) -> bool:
     return ((angle - start) % 360.0) <= span + 1e-9
 
 
-def bbox_for_section(section: object, project: "Project | None" = None,
+def bbox_for_section(
-                     ) -> tuple[float, float] | None:
+    section: object,
+    project: "Project | None" = None,
+) -> tuple[float, float] | None:
     """Return ``(width_y, height_z)`` of the section's local bounding box.
 
     ``None`` means "size could not be inferred" — the caller should skip
@@ -69,6 +71,7 @@ def bbox_for_section(section: object, project: "Project | None" = None,
         SectionAggregator,
         StraightLayer,
     )
+
     # ── ElasticSection: prefer explicit display dims; else back-solve.
     if isinstance(section, ElasticSection):
         explicit = _elastic_explicit_dims(section)

src/otko/services/section_properties.py

@@ -35,9 +35,9 @@ class SectionProps:
     area: float
     centroid_y: float
     centroid_z: float
-    Iy: float           # about centroid
+    Iy: float  # about centroid
-    Iz: float           # about centroid
+    Iz: float  # about centroid
-    fibre_yz: np.ndarray   # (n, 3): y, z, area
+    fibre_yz: np.ndarray  # (n, 3): y, z, area
 
 
 def expand_fibres(sec: FiberSection) -> np.ndarray:
@@ -65,9 +65,11 @@ def expand_fibres(sec: FiberSection) -> np.ndarray:
                     yc = p.y_center + r_mid * math.cos(theta)
                     zc = p.z_center + r_mid * math.sin(theta)
                     # Annular sector area: (r_outer² - r_inner²) * dθ / (2·n_rad)
-                    a = ((p.r_inner + (ir + 1) * d_r) ** 2
+                    a = (
-                         - (p.r_inner + ir * d_r) ** 2) \
+                        ((p.r_inner + (ir + 1) * d_r) ** 2 - (p.r_inner + ir * d_r) ** 2)
-                        * math.radians(d_theta) / 2.0
+                        * math.radians(d_theta)
+                        / 2.0
+                    )
                     rows.append((yc, zc, a))
 
     for lay in sec.layers:
@@ -102,8 +104,8 @@ def compute_section_props(sec: FiberSection) -> SectionProps:
     zc = float(np.sum(a * z) / total_a)
 
     # Second moments of area about centroid (parallel axis from each fibre).
-    Iz = float(np.sum(a * (y - yc) ** 2))    # about z-axis
+    Iz = float(np.sum(a * (y - yc) ** 2))  # about z-axis
-    Iy = float(np.sum(a * (z - zc) ** 2))    # about y-axis
+    Iy = float(np.sum(a * (z - zc) ** 2))  # about y-axis
 
     return SectionProps(
         n_fibres=len(fibres),

src/otko/services/spectrum.py

@@ -24,20 +24,22 @@ from otko.services.results import ModalResults
 class ModeContribution:
     """Per-mode metadata for a response-spectrum analysis."""
 
-    mode_number: int                    # 1-indexed
+    mode_number: int  # 1-indexed
-    period: float                        # s
+    period: float  # s
-    frequency: float                     # Hz
+    frequency: float  # Hz
-    angular_frequency: float             # rad/s
+    angular_frequency: float  # rad/s
-    participation_factor: float          # Γ_i for the chosen direction
+    participation_factor: float  # Γ_i for the chosen direction
-    effective_mass: float                # M_eff,i = Γ_i² · M_i
+    effective_mass: float  # M_eff,i = Γ_i² · M_i
-    mass_ratio: float                    # M_eff,i / Σ m
+    mass_ratio: float  # M_eff,i / Σ m
-    sa_at_period: float                  # Sa(T_i) from spectrum
+    sa_at_period: float  # Sa(T_i) from spectrum
     modal_peak_disp: dict[int, np.ndarray] = field(default_factory=dict)
     """node_id → peak modal displacement vector (3D translations)."""
 
 
 def mass_participation(
-    project: Project, modal: ModalResults, direction: int,
+    project: Project,
+    modal: ModalResults,
+    direction: int,
 ) -> list[ModeContribution]:
     """Compute Γ_i, M_eff,i and frequency for every mode.
 
@@ -79,21 +81,23 @@ def mass_participation(
             m_eff = 0.0
         else:
             gamma = numerator / denominator
-            m_eff = gamma ** 2 * denominator
+            m_eff = gamma**2 * denominator
 
         omega = float(np.sqrt(abs(modal.eigenvalues[mode_number - 1])))
         period = (2.0 * np.pi / omega) if omega > 0.0 else float("inf")
         ratio = (m_eff / total_mass) if total_mass > 0.0 else 0.0
-        out.append(ModeContribution(
+        out.append(
-            mode_number=mode_number,
+            ModeContribution(
-            period=period,
+                mode_number=mode_number,
-            frequency=omega / (2.0 * np.pi) if omega > 0.0 else 0.0,
+                period=period,
-            angular_frequency=omega,
+                frequency=omega / (2.0 * np.pi) if omega > 0.0 else 0.0,
-            participation_factor=gamma,
+                angular_frequency=omega,
-            effective_mass=m_eff,
+                participation_factor=gamma,
-            mass_ratio=ratio,
+                effective_mass=m_eff,
-            sa_at_period=0.0,           # filled in by combine_spectrum
+                mass_ratio=ratio,
-        ))
+                sa_at_period=0.0,  # filled in by combine_spectrum
+            )
+        )
     return out
 
 
@@ -137,8 +141,7 @@ def combine_modal_response(
             m.sa_at_period = 0.0
             continue
         m.sa_at_period = interp_sa(spectrum, m.period)
-        scale = (m.participation_factor * m.sa_at_period
+        scale = m.participation_factor * m.sa_at_period / (m.angular_frequency**2)
-                 / (m.angular_frequency ** 2))
         shape = modal.mode_shapes[m.mode_number]
         for nid, vec in shape.items():
             n_take = min(3, vec.size)
@@ -156,7 +159,7 @@ def combine_modal_response(
             for m in modes:
                 u = m.modal_peak_disp.get(nid)
                 if u is not None:
-                    sq_sum += u ** 2
+                    sq_sum += u**2
             combined[nid] = np.sqrt(sq_sum)
     elif method.upper() == "CQC":
         zeta = damping if damping is not None else spectrum.damping_ratio
@@ -169,8 +172,8 @@ def combine_modal_response(
                 if wi <= 0.0 or wj <= 0.0:
                     continue
                 r = wj / wi
-                num = 8.0 * zeta ** 2 * (1.0 + r) * r ** 1.5
+                num = 8.0 * zeta**2 * (1.0 + r) * r**1.5
-                denom = (1.0 - r ** 2) ** 2 + 4.0 * zeta ** 2 * r * (1.0 + r) ** 2
+                denom = (1.0 - r**2) ** 2 + 4.0 * zeta**2 * r * (1.0 + r) ** 2
                 rho[i, j] = num / denom if denom > 0.0 else 0.0
         for nid in node_ids:
             sq_sum = np.zeros(3)

src/otko/viewmodels/analysis_runner.py

@@ -20,7 +20,7 @@ class AnalysisRunner(QObject):
 
     started = Signal()
     log = Signal(str)
-    finished = Signal(object)         # StaticResults / ModalResults / TransientResults
+    finished = Signal(object)  # StaticResults / ModalResults / TransientResults
     failed = Signal(str)
     runningChanged = Signal(bool)
 

src/otko/viewmodels/project_vm.py

@@ -23,8 +23,8 @@ from otko.services import load_project, save_project
 class ProjectViewModel(QObject):
     """Holds the current Project, its file path, dirty state, and undo stack."""
 
-    projectChanged = Signal(object)   # emits Project | None
+    projectChanged = Signal(object)  # emits Project | None
-    modelMutated = Signal()           # same project, mutated by a command
+    modelMutated = Signal()  # same project, mutated by a command
     dirtyChanged = Signal(bool)
 
     def __init__(self, parent: QObject | None = None) -> None:

src/otko/views/action_handlers.py

@@ -47,6 +47,7 @@ from otko.views.dialogs import (
     AssignSectionDialog,
     AssignSupportDialog,
     AssignZeroLengthSectionDialog,
+    LoadCombinationManagerDialog,
     CoordinateGridSystemsDialog,
     LinearTimeSeriesDialog,
     MaterialLibraryDialog,
@@ -917,6 +918,11 @@ class ActionHandlers:
             self._on_new()
         AnalysisCaseManagerDialog(self._vm, self).exec()
 
+    def _on_combo_manager(self) -> None:
+        if self._vm.project is None:
+            self._on_new()
+        LoadCombinationManagerDialog(self._vm, self).exec()
+
     def _on_run_analysis(self) -> None:
         if self._vm.project is None:
             QMessageBox.information(self, "Run Analysis", "Open or create a project first.")
@@ -961,10 +967,7 @@ class ActionHandlers:
     def _on_about(self) -> None:
         box = QMessageBox(self)
         box.setWindowTitle("About OTKO")
-        box.setText(
+        box.setText(f"<h3>OTKO {__version__}</h3>" "<p>A modern desktop GUI for OpenSeesPy.</p>")
-            f"<h3>OTKO {__version__}</h3>"
-            "<p>A modern desktop GUI for OpenSeesPy.</p>"
-        )
         app_svg = Path(__file__).resolve().parent.parent / "resources" / "icons" / "app.svg"
         if app_svg.is_file():
             box.setIconPixmap(QIcon(str(app_svg)).pixmap(64, 64))

src/otko/views/canvas3d/diagram_renderer.py

@@ -34,14 +34,21 @@ from otko.services.element_forces import DiagramData, ForceComponent
 _LOG = logging.getLogger("otko.diagram")
 
 # Components that draw perpendicular to the element axis vs along it.
-_PERPENDICULAR = {ForceComponent.V2, ForceComponent.V3,
+_PERPENDICULAR = {
-                  ForceComponent.M2, ForceComponent.M3, ForceComponent.T}
+    ForceComponent.V2,
+    ForceComponent.V3,
+    ForceComponent.M2,
+    ForceComponent.M3,
+    ForceComponent.T,
+}
 
 # Which local axis the value is plotted along (2 = local y, 3 = local z).
 _LOCAL_AXIS = {
-    ForceComponent.V2: 2, ForceComponent.M3: 2,
+    ForceComponent.V2: 2,
-    ForceComponent.V3: 3, ForceComponent.M2: 3,
+    ForceComponent.M3: 2,
-    ForceComponent.T:  2,
+    ForceComponent.V3: 3,
+    ForceComponent.M2: 3,
+    ForceComponent.T: 2,
 }
 
 
@@ -69,8 +76,10 @@ class DiagramRenderer:
             # All values are zero → no diagram to draw. This is normal —
             # e.g. asking for "torsion" on a planar bending model. Log
             # a hint so the user understands the empty viewport.
-            _LOG.info("All '%s' values are zero for this analysis step "
+            _LOG.info(
-                      "— nothing to draw.", data.component.name)
+                "All '%s' values are zero for this analysis step " "— nothing to draw.",
+                data.component.name,
+            )
             return
 
         node_pos = {n.id: np.asarray(n.coords, dtype=float) for n in project.nodes}
@@ -79,8 +88,8 @@ class DiagramRenderer:
         is_perpendicular = data.component in _PERPENDICULAR
         axis_id = _LOCAL_AXIS.get(data.component, 2)
 
-        polys: list[np.ndarray] = []         # vertex arrays for each polygon
+        polys: list[np.ndarray] = []  # vertex arrays for each polygon
-        scalars: list[float] = []            # one value per polygon (avg of end values)
+        scalars: list[float] = []  # one value per polygon (avg of end values)
         for k, eid in enumerate(data.element_ids):
             elem = elem_lookup.get(int(eid))
             if elem is None:
@@ -106,15 +115,19 @@ class DiagramRenderer:
                 perp = self._local_perp(pi, pj, 2)
                 if perp is None:
                     continue
-                width = abs(v_i) * 0.5     # half-width fall-off
+                width = abs(v_i) * 0.5  # half-width fall-off
                 if width == 0.0:
                     width = abs(v_j) * 0.5
                 if width == 0.0:
                     continue
-                quad = np.vstack([
+                quad = np.vstack(
-                    pi - perp * width, pj - perp * width,
+                    [
-                    pj + perp * width, pi + perp * width,
+                        pi - perp * width,
-                ])
+                        pj - perp * width,
+                        pj + perp * width,
+                        pi + perp * width,
+                    ]
+                )
                 polys.append(quad)
                 scalars.append(0.5 * (data.values_i[k] + data.values_j[k]))
 
@@ -138,7 +151,9 @@ class DiagramRenderer:
         # Symmetric color range so zero stays at the colormap mid-point.
         vmax = float(np.max(np.abs(scalars))) or 1.0
         # Defensive: accept either ForceComponent enum or its name string.
-        comp_label = data.component.value if hasattr(data.component, "value") else str(data.component)
+        comp_label = (
+            data.component.value if hasattr(data.component, "value") else str(data.component)
+        )
         self._actor = self._plotter.add_mesh(
             mesh,
             scalars="value",
@@ -157,8 +172,7 @@ class DiagramRenderer:
         # ── Numerical labels at the global min and max element ends. ──
         self._label_actor = self._add_value_labels(project, data, scale)
 
-    def _add_value_labels(self, project: Project, data: DiagramData,
+    def _add_value_labels(self, project: Project, data: DiagramData, scale: float) -> Any:
-                          scale: float) -> Any:
         """Annotate the diagram's extreme ends with their numerical values.
 
         Avoids visual clutter by labelling only the two ends carrying the
@@ -203,9 +217,10 @@ class DiagramRenderer:
 
         try:
             return self._plotter.add_point_labels(
-                positions, labels,
+                positions,
+                labels,
                 font_size=14,
-                point_size=0,            # don't draw the underlying points
+                point_size=0,  # don't draw the underlying points
                 shape=None,
                 always_visible=True,
                 pickable=False,

src/otko/views/canvas3d/model_canvas.py

@@ -12,7 +12,6 @@ needing a reference to the renderer.
 
 from __future__ import annotations
 
-import os
 from typing import Any
 
 import numpy as np
@@ -26,7 +25,7 @@ from otko.views.canvas3d.model_renderer import ModelRenderer
 from otko.views.canvas3d.selection import SelectionState
 from otko.views.canvas3d.style import RenderStyle
 
-_PICK_DEBUG = os.environ.get("OSS_PICK_DEBUG") == "1"
+PICK_DEBUG = False
 
 
 class ModelCanvas(QtInteractor):  # type: ignore[misc]
@@ -127,7 +126,7 @@ class ModelCanvas(QtInteractor):  # type: ignore[misc]
         cx = qt_x * dpr
         cy = (h_logical - qt_y) * dpr
 
-        if _PICK_DEBUG:
+        if PICK_DEBUG:
             print(
                 f"[pick] click qt=({qt_x:.0f},{qt_y:.0f}) → vtk=({cx:.0f},{cy:.0f}) "
                 f"viewport_logical=({self.width()}x{h_logical}) dpr={dpr}"
@@ -148,7 +147,7 @@ class ModelCanvas(QtInteractor):  # type: ignore[misc]
             if node_screen is not None and len(node_screen):
                 d2 = (node_screen[:, 0] - cx) ** 2 + (node_screen[:, 1] - cy) ** 2
                 idx = int(np.argmin(d2))
-                if _PICK_DEBUG:
+                if PICK_DEBUG:
                     print(
                         f"[pick] nearest node id={node_ids[idx]} "
                         f"screen={node_screen[idx]} d={np.sqrt(d2[idx]):.1f}px "
@@ -181,7 +180,7 @@ class ModelCanvas(QtInteractor):  # type: ignore[misc]
                 closest = a_screen + t[:, None] * ab
                 d2 = ((p - closest) ** 2).sum(axis=1)
                 idx = int(np.argmin(d2))
-                if _PICK_DEBUG:
+                if PICK_DEBUG:
                     print(
                         f"[pick] nearest frame id={frame_ids[idx]} "
                         f"d={float(np.sqrt(d2[idx])):.1f}px "
@@ -191,7 +190,7 @@ class ModelCanvas(QtInteractor):  # type: ignore[misc]
                     self._dispatch_pick("element", int(frame_ids[idx]))
                     return
 
-        if _PICK_DEBUG:
+        if PICK_DEBUG:
             print("[pick] no hit within tolerance")
 
         # ── Empty-click fallback: pixel-space snap to grid intersections. ──
@@ -202,7 +201,7 @@ class ModelCanvas(QtInteractor):  # type: ignore[misc]
         snapped = self._nearest_grid_intersection_px(cx, cy, grid_tol_px)
         if snapped is not None:
             self.emptyClicked.emit(float(snapped[0]), float(snapped[1]), float(snapped[2]))
-        elif _PICK_DEBUG:
+        elif PICK_DEBUG:
             print("[pick] off-grid click — no snap target within tolerance")
 
     def _grid_intersections_world(self) -> np.ndarray | None:
@@ -260,7 +259,7 @@ class ModelCanvas(QtInteractor):  # type: ignore[misc]
             return None
         d2 = (screen[:, 0] - cx) ** 2 + (screen[:, 1] - cy) ** 2
         idx = int(np.argmin(d2))
-        if _PICK_DEBUG:
+        if PICK_DEBUG:
             print(
                 f"[grid-snap] nearest intersection "
                 f"world={world_points[idx]} d={float(np.sqrt(d2[idx])):.1f}px "

src/otko/views/canvas3d/style.py

@@ -19,15 +19,15 @@ class RenderStyle:
     background_top: str = "#dbe2ef"
     background_bottom: str = "#f5f7fb"
 
-    node_color: str = "#f0a500"            # warm gold
+    node_color: str = "#f0a500"  # warm gold
-    node_selected_color: str = "#00d4ff"   # bright cyan
+    node_selected_color: str = "#00d4ff"  # bright cyan
 
     frame_color: str = "#1f1f1f"
     truss_color: str = "#2e5cb8"
     zerolength_color: str = "#a020f0"
     selected_color: str = "#00d4ff"
 
-    fix_color: str = "#c0392b"             # firebrick
+    fix_color: str = "#c0392b"  # firebrick
     pin_color: str = "#c0392b"
     roller_color: str = "#e67e22"
     custom_support_color: str = "#7f8c8d"
@@ -45,7 +45,7 @@ class RenderStyle:
     support_relative_size: float = 0.025
     support_min_size: float = 0.10
 
-    load_relative_length: float = 0.10     # arrow length / bbox_diag
+    load_relative_length: float = 0.10  # arrow length / bbox_diag
     load_min_length: float = 0.5
 
     selection_thickness_factor: float = 1.6  # multiplier for selected actors

src/otko/views/dialogs/__init__.py

@@ -12,6 +12,7 @@ from otko.views.dialogs.assign_property import (
 from otko.views.dialogs.assign_support import PRESETS, AssignSupportDialog
 from otko.views.dialogs.assign_zls import AssignZeroLengthSectionDialog
 from otko.views.dialogs.case_manager import AnalysisCaseManagerDialog
+from otko.views.dialogs.combination_dialog import LoadCombinationManagerDialog
 from otko.views.dialogs.coord_grid_systems import (
     CoordinateGridSystemsDialog,
     CoordSystemDataDialog,
@@ -60,6 +61,7 @@ __all__ = [
     "DisplayOptionsDialog",
     "GridSystemDialog",
     "LinearTimeSeriesDialog",
+    "LoadCombinationManagerDialog",
     "MaterialLibraryDialog",
     "MaterialTesterDialog",
     "MirrorDialog",

src/otko/views/dialogs/add_node.py

@@ -40,12 +40,15 @@ class AddNodeDialog(QDialog):
             the node lands on the active plane by default.
     """
 
-    def __init__(self, next_node_id: int,
+    def __init__(
-                 grid: GridSystem,
+        self,
-                 ndm: int = 3,
+        next_node_id: int,
-                 parent: QWidget | None = None,
+        grid: GridSystem,
-                 *,
+        ndm: int = 3,
-                 plane_elevation: float | None = None) -> None:
+        parent: QWidget | None = None,
+        *,
+        plane_elevation: float | None = None,
+    ) -> None:
         super().__init__(parent)
         self.setWindowTitle("Add Node")
         self._next_id = next_node_id
@@ -71,16 +74,18 @@ class AddNodeDialog(QDialog):
         else:
             self._z.setVisible(False)
         if self._plane_elevation is not None and self._ndm == 3:
-            form.addRow(QLabel(
+            form.addRow(
-                f"<i>Suggested Z = active working-plane level "
+                QLabel(
-                f"({self._plane_elevation:g}).</i>",
+                    f"<i>Suggested Z = active working-plane level "
-            ))
+                    f"({self._plane_elevation:g}).</i>",
+                )
+            )
         root.addLayout(form)
 
         self._snap_cb = QCheckBox("Snap to nearest grid intersection")
-        self._snap_cb.setChecked(bool(
+        self._snap_cb.setChecked(
-            self._grid.x_lines or self._grid.y_lines or self._grid.z_lines
+            bool(self._grid.x_lines or self._grid.y_lines or self._grid.z_lines)
-        ))
+        )
         root.addWidget(self._snap_cb)
 
         buttons = QDialogButtonBox(

src/otko/views/dialogs/assign_equal_dof.py

@@ -42,10 +42,12 @@ class AssignEqualDOFDialog(QDialog):
 
     def _build_ui(self) -> None:
         layout = QVBoxLayout(self)
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            "Tie selected nodes together in chosen DOFs using OpenSees "
+            QLabel(
-            "<code>equalDOF</code>.",
+                "Tie selected nodes together in chosen DOFs using OpenSees "
-        ))
+                "<code>equalDOF</code>.",
+            )
+        )
 
         form = QFormLayout()
 
@@ -64,7 +66,7 @@ class AssignEqualDOFDialog(QDialog):
         dof_form = QFormLayout()
         self._dof_boxes: list[QCheckBox] = []
         labels = ("Ux", "Uy", "Uz", "Rx", "Ry", "Rz")
-        active_labels = labels[:2] + (labels[5:6] if self._ndf == 3 else labels[2:self._ndf])
+        active_labels = labels[:2] + (labels[5:6] if self._ndf == 3 else labels[2 : self._ndf])
         if self._ndf == 2:
             active_labels = labels[:2]
         elif self._ndf == 3:
@@ -79,7 +81,10 @@ class AssignEqualDOFDialog(QDialog):
             if self._suggested_dofs is not None and dof_id in self._suggested_dofs:
                 cb.setChecked(True)
             self._dof_boxes.append(cb)
-            dof_form.addRow(f"DOF {i if self._ndf != 3 else (1 if label=='Ux' else 2 if label=='Uy' else 3)}:", cb)
+            dof_form.addRow(
+                f"DOF {i if self._ndf != 3 else (1 if label=='Ux' else 2 if label=='Uy' else 3)}:",
+                cb,
+            )
         layout.addLayout(dof_form)
 
         buttons = QDialogButtonBox(

src/otko/views/dialogs/assign_hinge.py

@@ -64,9 +64,7 @@ class AssignHingeDialog(QDialog):
 
     def _build_ui(self, n_selected: int) -> None:
         layout = QVBoxLayout(self)
-        header = (
+        header = f"Convert <b>{n_selected}</b> selected element(s) to BeamWithHinges."
-            f"Convert <b>{n_selected}</b> selected element(s) to BeamWithHinges."
-        )
         prefill = self._selection_prefill()
         if prefill is None and self._element_ids:
             header += " <i>Selection is mixed — unit-scaled defaults shown.</i>"
@@ -160,18 +158,20 @@ class AssignHingeDialog(QDialog):
             if el is None:
                 return None
             if getattr(el, "type", None) == "BeamWithHinges":
-                collected.append({
+                collected.append(
-                    "section_i_id": getattr(el, "section_i_id", None),
+                    {
-                    "section_j_id": getattr(el, "section_j_id", None),
+                        "section_i_id": getattr(el, "section_i_id", None),
-                    "lp_i": getattr(el, "lp_i", None),
+                        "section_j_id": getattr(el, "section_j_id", None),
-                    "lp_j": getattr(el, "lp_j", None),
+                        "lp_i": getattr(el, "lp_i", None),
-                    "E": getattr(el, "E", None),
+                        "lp_j": getattr(el, "lp_j", None),
-                    "A": getattr(el, "A", None),
+                        "E": getattr(el, "E", None),
-                    "Iz": getattr(el, "Iz", None),
+                        "A": getattr(el, "A", None),
-                    "Iy": getattr(el, "Iy", None),
+                        "Iz": getattr(el, "Iz", None),
-                    "G": getattr(el, "G", None),
+                        "Iy": getattr(el, "Iy", None),
-                    "J": getattr(el, "J", None),
+                        "G": getattr(el, "G", None),
-                })
+                        "J": getattr(el, "J", None),
+                    }
+                )
                 continue
             sec_id = getattr(el, "section_id", None)
             if sec_id is None:
@@ -185,21 +185,22 @@ class AssignHingeDialog(QDialog):
                 # prefill the hinge pickers with the section itself.
                 collected.append({"section_i_id": sec_id, "section_j_id": sec_id})
                 continue
-            collected.append({
+            collected.append(
-                "section_i_id": sec_id,
+                {
-                "section_j_id": sec_id,
+                    "section_i_id": sec_id,
-                "E": getattr(sec, "E", None),
+                    "section_j_id": sec_id,
-                "A": getattr(sec, "A", None),
+                    "E": getattr(sec, "E", None),
-                "Iz": getattr(sec, "Iz", None),
+                    "A": getattr(sec, "A", None),
-                "Iy": getattr(sec, "Iy", None),
+                    "Iz": getattr(sec, "Iz", None),
-                "G": getattr(sec, "G", None),
+                    "Iy": getattr(sec, "Iy", None),
-                "J": getattr(sec, "J", None),
+                    "G": getattr(sec, "G", None),
-            })
+                    "J": getattr(sec, "J", None),
+                }
+            )
         if not collected:
             return None
         merged: dict = {}
-        for key in ("section_i_id", "section_j_id", "lp_i", "lp_j",
+        for key in ("section_i_id", "section_j_id", "lp_i", "lp_j", "E", "A", "Iz", "Iy", "G", "J"):
-                    "E", "A", "Iz", "Iy", "G", "J"):
             vals = {c.get(key) for c in collected if c.get(key) is not None}
             if len(vals) == 1:
                 merged[key] = next(iter(vals))

src/otko/views/dialogs/assign_load.py

@@ -80,9 +80,7 @@ class AssignLoadDialog(QDialog):
         pf.addRow("Active:", self._active_pattern_label)
 
         self._new_name_edit = QLineEdit("Pattern")
-        self._new_name_edit.setPlaceholderText(
+        self._new_name_edit.setPlaceholderText("Name for the new pattern (e.g. RefMoment)")
-            "Name for the new pattern (e.g. RefMoment)"
-        )
         pf.addRow("New name:", self._new_name_edit)
 
         # TimeSeries type selector — only used when creating a new

src/otko/views/dialogs/assign_masses.py

@@ -56,16 +56,22 @@ class AssignMassesDialog(QDialog):
 
         cur = self._current or (0.0, 0.0, 0.0, 0.0, 0.0, 0.0)
         form = QFormLayout()
-        self._mx = self._spin(cur[0]); form.addRow("Translation X:", self._mx)
+        self._mx = self._spin(cur[0])
-        self._my = self._spin(cur[1]); form.addRow("Translation Y:", self._my)
+        form.addRow("Translation X:", self._mx)
+        self._my = self._spin(cur[1])
+        form.addRow("Translation Y:", self._my)
         if self._ndf >= 3:
-            self._mz = self._spin(cur[2]); form.addRow("Translation Z:", self._mz)
+            self._mz = self._spin(cur[2])
+            form.addRow("Translation Z:", self._mz)
         else:
             self._mz = self._spin(cur[2])
         if self._ndf == 6:
-            self._mxx = self._spin(cur[3]); form.addRow("Rotation X (Ixx):", self._mxx)
+            self._mxx = self._spin(cur[3])
-            self._myy = self._spin(cur[4]); form.addRow("Rotation Y (Iyy):", self._myy)
+            form.addRow("Rotation X (Ixx):", self._mxx)
-            self._mzz = self._spin(cur[5]); form.addRow("Rotation Z (Izz):", self._mzz)
+            self._myy = self._spin(cur[4])
+            form.addRow("Rotation Y (Iyy):", self._myy)
+            self._mzz = self._spin(cur[5])
+            form.addRow("Rotation Z (Izz):", self._mzz)
         else:
             self._mxx = self._spin(cur[3])
             self._myy = self._spin(cur[4])
@@ -77,8 +83,7 @@ class AssignMassesDialog(QDialog):
         root.addWidget(self._xy_link)
 
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)
@@ -106,6 +111,10 @@ class AssignMassesDialog(QDialog):
     def mass_vector(self) -> tuple[float, float, float, float, float, float]:
         """Return the 6-tuple (Mx, My, Mz, Mxx, Myy, Mzz)."""
         return (
-            self._mx.value(), self._my.value(), self._mz.value(),
+            self._mx.value(),
-            self._mxx.value(), self._myy.value(), self._mzz.value(),
+            self._my.value(),
+            self._mz.value(),
+            self._mxx.value(),
+            self._myy.value(),
+            self._mzz.value(),
         )

src/otko/views/dialogs/assign_property.py

@@ -41,9 +41,9 @@ class AssignSectionDialog(QDialog):
         layout.addWidget(QLabel(self._current_note()))
 
         if not self._sections:
-            layout.addWidget(QLabel(
+            layout.addWidget(
-                "<i>No sections defined. Open Define → Section Library first.</i>"
+                QLabel("<i>No sections defined. Open Define → Section Library first.</i>")
-            ))
+            )
 
         self._combo = QComboBox()
         for s in self._sections:
@@ -115,15 +115,15 @@ class AssignMaterialDialog(QDialog):
 
     def _build_ui(self, n_elements: int) -> None:
         layout = QVBoxLayout(self)
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            f"Apply material to <b>{n_elements}</b> selected truss/zero-length element(s)."
+            QLabel(f"Apply material to <b>{n_elements}</b> selected truss/zero-length element(s).")
-        ))
+        )
         layout.addWidget(QLabel(self._current_note()))
 
         if not self._materials:
-            layout.addWidget(QLabel(
+            layout.addWidget(
-                "<i>No materials defined. Open Define → Material Library first.</i>"
+                QLabel("<i>No materials defined. Open Define → Material Library first.</i>")
-            ))
+            )
 
         self._combo = QComboBox()
         for m in self._materials:

src/otko/views/dialogs/assign_support.py

@@ -25,10 +25,10 @@ from PySide6.QtWidgets import (
 
 # Preset → 6-tuple (Ux, Uy, Uz, Rx, Ry, Rz)
 PRESETS: dict[str, tuple[bool, bool, bool, bool, bool, bool]] = {
-    "Free":   (False, False, False, False, False, False),
+    "Free": (False, False, False, False, False, False),
-    "Roller (Z)": (False, False, True,  False, False, False),
+    "Roller (Z)": (False, False, True, False, False, False),
-    "Pin":    (True,  True,  True,  False, False, False),
+    "Pin": (True, True, True, False, False, False),
-    "Fix":    (True,  True,  True,  True,  True,  True),
+    "Fix": (True, True, True, True, True, True),
 }
 
 

src/otko/views/dialogs/assign_zls.py

@@ -25,8 +25,9 @@ from otko.core import Project
 class AssignZeroLengthSectionDialog(QDialog):
     """Modal dialog: pick a section, confirm creation between 2 nodes."""
 
-    def __init__(self, project: Project, node_ids: tuple[int, int],
+    def __init__(
-                 parent: QWidget | None = None) -> None:
+        self, project: Project, node_ids: tuple[int, int], parent: QWidget | None = None
+    ) -> None:
         super().__init__(parent)
         self.setWindowTitle("Assign Zero-Length Section")
         self._project = project
@@ -35,12 +36,14 @@ class AssignZeroLengthSectionDialog(QDialog):
 
     def _build_ui(self) -> None:
         root = QVBoxLayout(self)
-        root.addWidget(QLabel(
+        root.addWidget(
-            f"Connect node <b>{self._node_ids[0]}</b> and "
+            QLabel(
-            f"<b>{self._node_ids[1]}</b> through a zero-length "
+                f"Connect node <b>{self._node_ids[0]}</b> and "
-            "section element. The two nodes must share the same "
+                f"<b>{self._node_ids[1]}</b> through a zero-length "
-            "coordinates."
+                "section element. The two nodes must share the same "
-        ))
+                "coordinates."
+            )
+        )
 
         form = QFormLayout()
         self._section_cb = QComboBox()
@@ -53,8 +56,7 @@ class AssignZeroLengthSectionDialog(QDialog):
         root.addLayout(form)
 
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)

src/otko/views/dialogs/case_forms.py

@@ -37,9 +37,14 @@ from otko.core import (
 
 
 # ─────────────────────────── helpers ───────────────────────────
-def _spin(default: float = 0.0, *, decimals: int = 6,
+def _spin(
-          minimum: float = -1e15, maximum: float = 1e15,
+    default: float = 0.0,
-          step: float = 1.0) -> QDoubleSpinBox:
+    *,
+    decimals: int = 6,
+    minimum: float = -1e15,
+    maximum: float = 1e15,
+    step: float = 1.0,
+) -> QDoubleSpinBox:
     sb = QDoubleSpinBox()
     sb.setRange(minimum, maximum)
     sb.setDecimals(decimals)
@@ -227,7 +232,14 @@ class CaseFormBase(QWidget):
 
 
 # ─────────────────────────── Static ───────────────────────────
-_STATIC_SYSTEMS = ["BandGeneral", "BandSPD", "ProfileSPD", "SparseGeneral", "UmfPack", "FullGeneral"]
+_STATIC_SYSTEMS = [
+    "BandGeneral",
+    "BandSPD",
+    "ProfileSPD",
+    "SparseGeneral",
+    "UmfPack",
+    "FullGeneral",
+]
 _CONSTRAINTS = ["Plain", "Lagrange", "Penalty", "Transformation"]
 _INTEGRATORS_STATIC = ["LoadControl", "DisplacementControl", "ArcLength"]
 _ALGORITHMS = ["Linear", "Newton", "ModifiedNewton", "KrylovNewton", "BFGS", "Broyden"]
@@ -291,7 +303,8 @@ class StaticCaseForm(CaseFormBase):
 
     def _read_specific(self, cid: int) -> StaticCase:
         return StaticCase(
-            id=cid, name=self._name_edit.text(),
+            id=cid,
+            name=self._name_edit.text(),
             pattern_ids=_require_pattern_ids(self._patterns_picker),
             **_factor_kwargs(StaticCase, self._patterns_picker, self._pattern_factor_spins),
             n_steps=self._n_steps.value(),
@@ -322,9 +335,9 @@ class ModalCaseForm(CaseFormBase):
         self._solver.addItems(["genBandArpack", "fullGenLapack", "symmBandLapack"])
         self._layout.addRow("Number of modes:", self._n_modes)
         self._layout.addRow("Solver:", self._solver)
-        self._layout.addRow(QLabel(
+        self._layout.addRow(
-            "<i>The runner auto-falls back to fullGenLapack for very small models.</i>"
+            QLabel("<i>The runner auto-falls back to fullGenLapack for very small models.</i>")
-        ))
+        )
 
     def _populate_specific(self, c: ModalCase) -> None:
         self._n_modes.setValue(c.n_modes)
@@ -332,7 +345,8 @@ class ModalCaseForm(CaseFormBase):
 
     def _read_specific(self, cid: int) -> ModalCase:
         return ModalCase(
-            id=cid, name=self._name_edit.text(),
+            id=cid,
+            name=self._name_edit.text(),
             n_modes=self._n_modes.value(),
             solver=self._solver.currentText(),
         )
@@ -359,13 +373,19 @@ class TransientCaseForm(CaseFormBase):
         self._remove_patterns_picker = _make_pattern_picker(patterns)
         self._dt = _spin(0.01, decimals=8, minimum=1e-12, step=1e-3)
         self._n_steps = _int_spin(1000, minimum=1, maximum=10_000_000)
-        self._system = QComboBox(); self._system.addItems(_STATIC_SYSTEMS)
+        self._system = QComboBox()
-        self._constraints = QComboBox(); self._constraints.addItems(_CONSTRAINTS)
+        self._system.addItems(_STATIC_SYSTEMS)
-        self._integrator = QComboBox(); self._integrator.addItems(_INTEGRATORS_TRANSIENT)
+        self._constraints = QComboBox()
+        self._constraints.addItems(_CONSTRAINTS)
+        self._integrator = QComboBox()
+        self._integrator.addItems(_INTEGRATORS_TRANSIENT)
         self._gamma = _spin(0.5, decimals=4, minimum=0.0, maximum=1.0, step=0.01)
         self._beta = _spin(0.25, decimals=4, minimum=0.0, maximum=1.0, step=0.01)
-        self._algorithm = QComboBox(); self._algorithm.addItems(_ALGORITHMS); self._algorithm.setCurrentText("Newton")
+        self._algorithm = QComboBox()
-        self._test = QComboBox(); self._test.addItems(_TESTS)
+        self._algorithm.addItems(_ALGORITHMS)
+        self._algorithm.setCurrentText("Newton")
+        self._test = QComboBox()
+        self._test.addItems(_TESTS)
         self._tol = _spin(1e-6, decimals=12, minimum=1e-15, step=1e-7)
         self._max_iter = _int_spin(25)
         self._alpha_m = _spin(0.0, decimals=8, minimum=0.0, maximum=1e12, step=1e-4)
@@ -376,10 +396,12 @@ class TransientCaseForm(CaseFormBase):
         self._layout.addRow(self._patterns_picker)
         self._layout.addRow(QLabel("<b>Preload static cases (optional):</b>"))
         self._layout.addRow(self._preload_picker)
-        self._layout.addRow(QLabel(
+        self._layout.addRow(
-            "<i>Run these Static cases first, then hold them constant via "
+            QLabel(
-            "loadConst -time 0.0 before the transient starts.</i>"
+                "<i>Run these Static cases first, then hold them constant via "
-        ))
+                "loadConst -time 0.0 before the transient starts.</i>"
+            )
+        )
         self._layout.addRow(QLabel("<b>Patterns to remove after preload (optional):</b>"))
         self._layout.addRow(self._remove_patterns_picker)
         self._layout.addRow("dt:", self._dt)
@@ -396,17 +418,20 @@ class TransientCaseForm(CaseFormBase):
         self._layout.addRow("Rayleigh αM:", self._alpha_m)
         self._layout.addRow("Rayleigh βK:", self._beta_k)
         self._layout.addRow("Mode-1 damping ratio:", self._mode1_damping)
-        self._layout.addRow(QLabel(
+        self._layout.addRow(
-            "<i>If mode-1 damping is > 0, the runner computes βK = 2ζ/√λ1 "
+            QLabel(
-            "after preload and uses it instead of the manual βK value.</i>"
+                "<i>If mode-1 damping is > 0, the runner computes βK = 2ζ/√λ1 "
-        ))
+                "after preload and uses it instead of the manual βK value.</i>"
+            )
+        )
 
     def _populate_specific(self, c: TransientCase) -> None:
         _select_pattern_ids(self._patterns_picker, c.pattern_ids)
         _set_factor_spins(self._pattern_factor_spins, getattr(c, "pattern_factors", {}) or {})
         _select_case_ids(self._preload_picker, c.preload_case_ids)
         _select_pattern_ids(self._remove_patterns_picker, c.remove_patterns)
-        self._dt.setValue(c.dt); self._n_steps.setValue(c.n_steps)
+        self._dt.setValue(c.dt)
+        self._n_steps.setValue(c.n_steps)
         self._system.setCurrentText(c.system)
         self._constraints.setCurrentText(c.constraints)
         self._integrator.setCurrentText(c.integrator)
@@ -423,12 +448,14 @@ class TransientCaseForm(CaseFormBase):
     def _read_specific(self, cid: int) -> TransientCase:
         mode1_damping = self._mode1_damping.value()
         return TransientCase(
-            id=cid, name=self._name_edit.text(),
+            id=cid,
+            name=self._name_edit.text(),
             pattern_ids=_require_pattern_ids(self._patterns_picker),
             **_factor_kwargs(TransientCase, self._patterns_picker, self._pattern_factor_spins),
             preload_case_ids=_selected_case_ids(self._preload_picker),
             remove_patterns=_selected_pattern_ids(self._remove_patterns_picker),
-            dt=self._dt.value(), n_steps=self._n_steps.value(),
+            dt=self._dt.value(),
+            n_steps=self._n_steps.value(),
             system=self._system.currentText(),
             constraints=self._constraints.currentText(),
             integrator=self._integrator.currentText(),
@@ -462,12 +489,18 @@ class PushoverCaseForm(CaseFormBase):
         self._target = _spin(0.1, decimals=6, minimum=-1e6, maximum=1e6, step=0.001)
         self._step = _spin(0.001, decimals=8, minimum=1e-12, step=1e-4)
         self._base_nodes = QLineEdit()
-        self._base_nodes.setPlaceholderText("comma-separated node ids (leave blank for all supports)")
+        self._base_nodes.setPlaceholderText(
-        self._system = QComboBox(); self._system.addItems(_STATIC_SYSTEMS)
+            "comma-separated node ids (leave blank for all supports)"
-        self._constraints = QComboBox(); self._constraints.addItems(_CONSTRAINTS)
+        )
-        self._algorithm = QComboBox(); self._algorithm.addItems(_ALGORITHMS)
+        self._system = QComboBox()
+        self._system.addItems(_STATIC_SYSTEMS)
+        self._constraints = QComboBox()
+        self._constraints.addItems(_CONSTRAINTS)
+        self._algorithm = QComboBox()
+        self._algorithm.addItems(_ALGORITHMS)
         self._algorithm.setCurrentText("Newton")
-        self._test = QComboBox(); self._test.addItems(_TESTS)
+        self._test = QComboBox()
+        self._test.addItems(_TESTS)
         self._tol = _spin(1e-6, decimals=12, minimum=1e-15, step=1e-7)
         self._max_iter = _int_spin(25)
 
@@ -475,10 +508,12 @@ class PushoverCaseForm(CaseFormBase):
         self._layout.addRow(self._patterns_picker)
         self._layout.addRow(QLabel("<b>Preload static cases (optional):</b>"))
         self._layout.addRow(self._preload_picker)
-        self._layout.addRow(QLabel(
+        self._layout.addRow(
-            "<i>Run these Static cases first, then hold them constant via "
+            QLabel(
-            "loadConst -time 0.0 before the pushover starts.</i>"
+                "<i>Run these Static cases first, then hold them constant via "
-        ))
+                "loadConst -time 0.0 before the pushover starts.</i>"
+            )
+        )
         self._layout.addRow("Control node:", self._control_node)
         self._layout.addRow("Control DOF:", self._control_dof)
         self._layout.addRow("Target displacement:", self._target)
@@ -511,7 +546,8 @@ class PushoverCaseForm(CaseFormBase):
         txt = self._base_nodes.text().strip()
         base_ids = [int(x) for x in txt.replace(",", " ").split() if x] if txt else []
         return PushoverCase(
-            id=cid, name=self._name_edit.text(),
+            id=cid,
+            name=self._name_edit.text(),
             pattern_ids=_require_pattern_ids(self._patterns_picker),
             **_factor_kwargs(PushoverCase, self._patterns_picker, self._pattern_factor_spins),
             preload_case_ids=_selected_case_ids(self._preload_picker),
@@ -552,10 +588,12 @@ class ResponseSpectrumCaseForm(CaseFormBase):
         self._layout.addRow("Direction (DOF):", self._direction)
         self._layout.addRow("Combination:", self._combination)
         self._layout.addRow("Damping (CQC override):", self._damping)
-        self._layout.addRow(QLabel(
+        self._layout.addRow(
-            "<i>Damping is used by CQC modal correlation only; "
+            QLabel(
-            "leave at 0 to use the spectrum's own damping ratio.</i>",
+                "<i>Damping is used by CQC modal correlation only; "
-        ))
+                "leave at 0 to use the spectrum's own damping ratio.</i>",
+            )
+        )
 
     def _populate_specific(self, c: ResponseSpectrumCase) -> None:
         self._modal_case.setValue(c.modal_case_id)
@@ -568,7 +606,8 @@ class ResponseSpectrumCaseForm(CaseFormBase):
     def _read_specific(self, cid: int) -> ResponseSpectrumCase:
         damp_val = self._damping.value()
         return ResponseSpectrumCase(
-            id=cid, name=self._name_edit.text(),
+            id=cid,
+            name=self._name_edit.text(),
             modal_case_id=self._modal_case.value(),
             spectrum_id=self._spectrum_id.value(),
             direction=self._direction.value(),

src/otko/views/dialogs/case_manager.py

@@ -27,7 +27,11 @@ from otko.commands import (
     UpdateAnalysisCaseCommand,
 )
 from otko.core import (
-    ModalCase, PushoverCase, ResponseSpectrumCase, StaticCase, TransientCase,
+    ModalCase,
+    PushoverCase,
+    ResponseSpectrumCase,
+    StaticCase,
+    TransientCase,
 )
 from otko.viewmodels import ProjectViewModel
 from otko.views.dialogs.case_forms import FORM_REGISTRY, form_for
@@ -56,16 +60,23 @@ def _default_case(kind: str, cid: int, project: Project):  # type: ignore[no-unt
         return ModalCase(id=cid, name="Modal", n_modes=3)
     if kind == "Transient":
         return TransientCase(
-            id=cid, name="Transient", pattern_ids=[_first_pattern_id(project)],
+            id=cid,
-            dt=0.01, n_steps=1000,
+            name="Transient",
+            pattern_ids=[_first_pattern_id(project)],
+            dt=0.01,
+            n_steps=1000,
         )
     if kind == "Pushover":
         if not project.nodes:
             raise ValueError("Define at least one node before adding a Pushover case.")
         return PushoverCase(
-            id=cid, name="Pushover", pattern_ids=[_first_pattern_id(project)],
+            id=cid,
-            control_node=project.nodes[0].id, control_dof=1,
+            name="Pushover",
-            target_disp=0.1, step_size=0.001,
+            pattern_ids=[_first_pattern_id(project)],
+            control_node=project.nodes[0].id,
+            control_dof=1,
+            target_disp=0.1,
+            step_size=0.001,
         )
     if kind == "ResponseSpectrum":
         modal_ids = [c.id for c in project.analyses if isinstance(c, ModalCase)]
@@ -73,13 +84,15 @@ def _default_case(kind: str, cid: int, project: Project):  # type: ignore[no-unt
             raise ValueError("Add a Modal case before adding a ResponseSpectrum case.")
         if not project.spectra:
             raise ValueError(
-                "Define at least one response spectrum before adding "
+                "Define at least one response spectrum before adding " "a ResponseSpectrum case."
-                "a ResponseSpectrum case."
             )
         return ResponseSpectrumCase(
-            id=cid, name="ResponseSpectrum",
+            id=cid,
-            modal_case_id=modal_ids[0], spectrum_id=project.spectra[0].id,
+            name="ResponseSpectrum",
-            direction=1, combination="SRSS",
+            modal_case_id=modal_ids[0],
+            spectrum_id=project.spectra[0].id,
+            direction=1,
+            combination="SRSS",
         )
     raise ValueError(f"Unknown analysis type: {kind}.")
 
@@ -150,7 +163,7 @@ class AnalysisCaseManagerDialog(QDialog):
         if self._list.currentItem() is not None:
             selected_id = self._list.currentItem().data(Qt.ItemDataRole.UserRole)
         self._list.clear()
-        for c in (self._vm.project.analyses if self._vm.project else []):
+        for c in self._vm.project.analyses if self._vm.project else []:
             label = f"#{c.id}  {c.name or '(unnamed)'}  [{c.type}]"
             item = QListWidgetItem(label)
             item.setData(Qt.ItemDataRole.UserRole, c.id)
@@ -201,22 +214,31 @@ class AnalysisCaseManagerDialog(QDialog):
             # patterns). Do NOT fall through to the general type picker —
             # Static/Transient/Pushover would get dangling pattern refs.
             QMessageBox.information(
-                self, "No patterns",
+                self,
+                "No patterns",
                 "No load patterns defined yet — only a Modal case can be "
                 "added (Modal works without patterns). Define a pattern "
                 "first for Static, Transient, or Pushover cases.",
             )
             kind, ok = QInputDialog.getItem(
-                self, "Add analysis case", "Type:",
+                self,
-                ["Modal"], current=0, editable=False,
+                "Add analysis case",
+                "Type:",
+                ["Modal"],
+                current=0,
+                editable=False,
             )
             if not ok:
                 return
             self._create_case_of_kind("Modal")
             return
         kind, ok = QInputDialog.getItem(
-            self, "Add analysis case", "Type:",
+            self,
-            list(_DEFAULTS.keys()), current=0, editable=False,
+            "Add analysis case",
+            "Type:",
+            list(_DEFAULTS.keys()),
+            current=0,
+            editable=False,
         )
         if not ok:
             return

src/otko/views/dialogs/coord_grid_systems.py

@@ -61,8 +61,7 @@ class CoordSystemDataDialog(QDialog):
     ) -> None:
         super().__init__(parent)
         self.setWindowTitle(
-            "Edit Coordinate/Grid System"
+            "Edit Coordinate/Grid System" if existing is not None else "Add Coordinate/Grid System"
-            if existing is not None else "Add Coordinate/Grid System"
         )
         self._is_global = is_global
         self._existing = existing
@@ -88,28 +87,33 @@ class CoordSystemDataDialog(QDialog):
         loc_box = QGroupBox("Location and Orientation (relative to Global)")
         loc_form = QFormLayout(loc_box)
 
-        self._ox = self._spin(); self._oy = self._spin(); self._oz = self._spin()
+        self._ox = self._spin()
+        self._oy = self._spin()
+        self._oz = self._spin()
         origin_row = QHBoxLayout()
         for label, w in (("X", self._ox), ("Y", self._oy), ("Z", self._oz)):
             origin_row.addWidget(QLabel(f"{label}:"))
             origin_row.addWidget(w)
-        origin_wrap = QWidget(); origin_wrap.setLayout(origin_row)
+        origin_wrap = QWidget()
+        origin_wrap.setLayout(origin_row)
         loc_form.addRow("Origin:", origin_wrap)
 
-        self._rx = self._rot_spin(); self._ry = self._rot_spin(); self._rz = self._rot_spin()
+        self._rx = self._rot_spin()
+        self._ry = self._rot_spin()
+        self._rz = self._rot_spin()
         rot_row = QHBoxLayout()
         for label, w in (("about X", self._rx), ("about Y", self._ry), ("about Z", self._rz)):
             rot_row.addWidget(QLabel(f"{label}:"))
             rot_row.addWidget(w)
-        rot_wrap = QWidget(); rot_wrap.setLayout(rot_row)
+        rot_wrap = QWidget()
+        rot_wrap.setLayout(rot_row)
         loc_form.addRow("Rotation (deg):", rot_wrap)
 
         if self._is_global:
             for w in (self._ox, self._oy, self._oz, self._rx, self._ry, self._rz):
                 w.setEnabled(False)
             loc_box.setToolTip(
-                "Global system is anchored at the world origin "
+                "Global system is anchored at the world origin " "with identity orientation.",
-                "with identity orientation.",
             )
 
         layout.addWidget(loc_box)
@@ -160,8 +164,7 @@ class CoordSystemDataDialog(QDialog):
 
         # ── Buttons ──────────────────────────────────────────────
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self._on_accept)
         buttons.rejected.connect(self.reject)
@@ -189,9 +192,13 @@ class CoordSystemDataDialog(QDialog):
     def _load_existing(self, cs: CoordinateGridSystem) -> None:
         self._name_edit.setText(cs.name)
         ox, oy, oz = cs.coord.origin
-        self._ox.setValue(ox); self._oy.setValue(oy); self._oz.setValue(oz)
+        self._ox.setValue(ox)
+        self._oy.setValue(oy)
+        self._oz.setValue(oz)
         rx, ry, rz = cs.coord.rotation_deg
-        self._rx.setValue(rx); self._ry.setValue(ry); self._rz.setValue(rz)
+        self._rx.setValue(rx)
+        self._ry.setValue(ry)
+        self._rz.setValue(rz)
         self._x_edit.setText(_spacings_text(cs.grid.x_lines))
         self._y_edit.setText(_spacings_text(cs.grid.y_lines))
         self._z_edit.setText(_spacings_text(cs.grid.z_lines))
@@ -245,9 +252,7 @@ class CoordinateGridSystemsDialog(QDialog):
         super().__init__(parent)
         self.setWindowTitle("Coordinate/Grid Systems")
         self.resize(600, 420)
-        self._systems: list[CoordinateGridSystem] = [
+        self._systems: list[CoordinateGridSystem] = [s.model_copy(deep=True) for s in systems]
-            s.model_copy(deep=True) for s in systems
-        ]
         self._build_ui()
         self._refresh_list()
 
@@ -290,8 +295,7 @@ class CoordinateGridSystemsDialog(QDialog):
         right.addStretch(1)
 
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)
@@ -332,9 +336,7 @@ class CoordinateGridSystemsDialog(QDialog):
         self._btn_modify.setEnabled(cs is not None)
         self._cb_general.blockSignals(True)
         self._cb_general.setChecked(cs.grid.is_general if cs is not None else False)
-        self._cb_general.setEnabled(
+        self._cb_general.setEnabled(cs is not None and not cs.grid.is_general)
-            cs is not None and not cs.grid.is_general
-        )
         self._cb_general.blockSignals(False)
 
     # ── actions ──────────────────────────────────────────────────
@@ -351,14 +353,17 @@ class CoordinateGridSystemsDialog(QDialog):
         from otko.views.dialogs.define_grid_data import (
             DefineGridSystemDataDialog,
         )
+
         dlg = DefineGridSystemDataDialog(parent=self)
         if dlg.exec() != QDialog.DialogCode.Accepted:
             return
         new_sys = dlg.system()
         if any(s.name == new_sys.name for s in self._systems):
-            new_sys = new_sys.model_copy(update={
+            new_sys = new_sys.model_copy(
-                "name": self._unique_name(new_sys.name),
+                update={
-            })
+                    "name": self._unique_name(new_sys.name),
+                }
+            )
         self._systems.append(new_sys)
         self._refresh_list(select_name=new_sys.name)
 
@@ -380,8 +385,11 @@ class CoordinateGridSystemsDialog(QDialog):
         from otko.views.dialogs.define_grid_data import (
             DefineGridSystemDataDialog,
         )
+
         dlg = DefineGridSystemDataDialog(
-            existing=cs, is_global=cs.is_global(), parent=self,
+            existing=cs,
+            is_global=cs.is_global(),
+            parent=self,
         )
         if dlg.exec() != QDialog.DialogCode.Accepted:
             return
@@ -392,9 +400,11 @@ class CoordinateGridSystemsDialog(QDialog):
         # Enforce unique names against siblings.
         others = [s for s in self._systems if s is not cs]
         if any(s.name == updated.name for s in others):
-            updated = updated.model_copy(update={
+            updated = updated.model_copy(
-                "name": self._unique_name(updated.name),
+                update={
-            })
+                    "name": self._unique_name(updated.name),
+                }
+            )
         row = self._list.currentRow()
         self._systems[row] = updated
         self._refresh_list(select_name=updated.name)
@@ -414,7 +424,8 @@ class CoordinateGridSystemsDialog(QDialog):
         if cs.grid.is_general and not checked:
             # SAP2000: once converted to General, can't convert back.
             QMessageBox.information(
-                self, "Convert to General",
+                self,
+                "Convert to General",
                 "Once a system is converted to General, it cannot be "
                 "converted back to a regular Cartesian system.",
             )

src/otko/views/dialogs/define_grid_data.py

@@ -127,9 +127,9 @@ class _AxisGridTable(QWidget):
         prev = 0.0
         for i, v in enumerate(ords):
             if i == 0:
-                out.append(v)           # first row: absolute position
+                out.append(v)  # first row: absolute position
             else:
-                out.append(v - prev)    # subsequent rows: spacing from previous
+                out.append(v - prev)  # subsequent rows: spacing from previous
             prev = v
         return out
 
@@ -169,23 +169,28 @@ class _AxisGridTable(QWidget):
             visible_widget = self._table.cellWidget(row, 3)
             bubble_widget = self._table.cellWidget(row, 4)
             color_item = self._table.item(row, 5)
-            out.append(GridLine(
+            out.append(
-                id=(id_item.text().strip() if id_item else f"{self.axis}{row + 1}"),
+                GridLine(
-                ordinate=ords[row] if row < len(ords) else 0.0,
+                    id=(id_item.text().strip() if id_item else f"{self.axis}{row + 1}"),
-                line_type=(
+                    ordinate=ords[row] if row < len(ords) else 0.0,
-                    line_type_widget.currentText()  # type: ignore[union-attr]
+                    line_type=(
-                    if isinstance(line_type_widget, QComboBox) else "Primary"
+                        line_type_widget.currentText()  # type: ignore[union-attr]
-                ),
+                        if isinstance(line_type_widget, QComboBox)
-                visible=(
+                        else "Primary"
-                    visible_widget.isChecked()      # type: ignore[union-attr]
+                    ),
-                    if isinstance(visible_widget, QCheckBox) else True
+                    visible=(
-                ),
+                        visible_widget.isChecked()  # type: ignore[union-attr]
-                bubble_loc=(
+                        if isinstance(visible_widget, QCheckBox)
-                    bubble_widget.currentText()     # type: ignore[union-attr]
+                        else True
-                    if isinstance(bubble_widget, QComboBox) else "End"
+                    ),
-                ),
+                    bubble_loc=(
-                color=(color_item.text() if color_item else "#808080"),
+                        bubble_widget.currentText()  # type: ignore[union-attr]
-            ))
+                        if isinstance(bubble_widget, QComboBox)
+                        else "End"
+                    ),
+                    color=(color_item.text() if color_item else "#808080"),
+                )
+            )
         return out
 
     # ── row ops ───────────────────────────────────────────────────
@@ -218,7 +223,8 @@ class _AxisGridTable(QWidget):
         vis = QCheckBox()
         vis.setChecked(ln.visible)
         vis_wrap = QWidget()
-        lay = QHBoxLayout(vis_wrap); lay.setContentsMargins(0, 0, 0, 0)
+        lay = QHBoxLayout(vis_wrap)
+        lay.setContentsMargins(0, 0, 0, 0)
         lay.addWidget(vis)
         lay.setAlignment(Qt.AlignmentFlag.AlignCenter)
         # We keep the QCheckBox directly; the wrap is optional visual
@@ -250,13 +256,13 @@ class _AxisGridTable(QWidget):
         lines = self.collect_lines()
         lines.sort(key=lambda ln: ln.ordinate)
         self._table.setRowCount(0)
-        self._show_spacing = False   # reset to ordinate view after sort
+        self._show_spacing = False  # reset to ordinate view after sort
         self._table.setHorizontalHeaderLabels(self.COLUMNS)
         for ln in lines:
             self._append_row(ln)
 
     def _on_cell_double_clicked(self, row: int, col: int) -> None:
-        if col == 5:   # Color picker
+        if col == 5:  # Color picker
             item = self._table.item(row, col)
             current = QColor(item.text() if item else "#808080")
             new = QColorDialog.getColor(current, self, "Grid Line Color")
@@ -278,8 +284,7 @@ class DefineGridSystemDataDialog(QDialog):
     ) -> None:
         super().__init__(parent)
         self.setWindowTitle(
-            "Define Grid System Data" if existing is not None
+            "Define Grid System Data" if existing is not None else "Add Grid System"
-            else "Add Grid System"
         )
         self.resize(780, 620)
         self._is_global = is_global
@@ -328,9 +333,7 @@ class DefineGridSystemDataDialog(QDialog):
         self._btn_locate.clicked.connect(self._on_locate_origin)
         if self._is_global:
             self._btn_locate.setEnabled(False)
-            self._btn_locate.setToolTip(
+            self._btn_locate.setToolTip("Global system is anchored at the world origin.")
-                "Global system is anchored at the world origin."
-            )
         head.addWidget(self._btn_locate)
         root.addLayout(head)
 
@@ -375,8 +378,7 @@ class DefineGridSystemDataDialog(QDialog):
         bottom.addWidget(self._btn_quick)
         bottom.addStretch(1)
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self._on_accept)
         buttons.rejected.connect(self.reject)
@@ -388,8 +390,7 @@ class DefineGridSystemDataDialog(QDialog):
         ox, oy, oz = self._origin
         rx, ry, rz = self._rotation_deg
         self._origin_label.setText(
-            f"Origin: ({ox:g}, {oy:g}, {oz:g})   "
+            f"Origin: ({ox:g}, {oy:g}, {oz:g})   " f"Rotation: ({rx:g}°, {ry:g}°, {rz:g}°)"
-            f"Rotation: ({rx:g}°, {ry:g}°, {rz:g}°)"
         )
 
     def _load_existing(self, cs: CoordinateGridSystem) -> None:
@@ -415,6 +416,7 @@ class DefineGridSystemDataDialog(QDialog):
         from otko.views.dialogs.locate_origin import (
             CoordSystemLocationOrientationDialog,
         )
+
         dlg = CoordSystemLocationOrientationDialog(
             origin=self._origin,
             rotation_deg=self._rotation_deg,
@@ -429,11 +431,13 @@ class DefineGridSystemDataDialog(QDialog):
         from otko.views.dialogs.quick_grid_lines import (
             QuickGridLinesDialog,
         )
+
         dlg = QuickGridLinesDialog(parent=self)
         if dlg.exec() != QDialog.DialogCode.Accepted:
             return
         xs, ys, zs = dlg.ordinates()
         from otko.core.geometry import make_grid_lines
+
         # Revert to ordinate display mode before replacing rows.
         self._rb_ordinates.setChecked(True)
         self._tab_x.load_lines(make_grid_lines("X", xs))
@@ -465,7 +469,8 @@ class DefineGridSystemDataDialog(QDialog):
         return CoordinateGridSystem(
             name=self._name_edit.text().strip(),
             coord=CoordinateSystem(
-                origin=self._origin, rotation_deg=self._rotation_deg,
+                origin=self._origin,
+                rotation_deg=self._rotation_deg,
             ),
             grid=grid,
         )

src/otko/views/dialogs/distributed_load.py

@@ -141,9 +141,11 @@ class AssignDistributedLoadDialog(QDialog):
 
     def values(self) -> tuple[float, float, float]:
         """Return (wy, wz, wx)."""
-        return (self._spinboxes["wy"].value(),
+        return (
-                self._spinboxes["wz"].value(),
+            self._spinboxes["wy"].value(),
-                self._spinboxes["wx"].value())
+            self._spinboxes["wz"].value(),
+            self._spinboxes["wx"].value(),
+        )
 
     def selected_pattern_id(self) -> int | None:
         """Return the chosen pattern id, or ``None`` if the user picked

src/otko/views/dialogs/grid_system.py

@@ -63,9 +63,9 @@ def _coords_from_spacings(spacings: list[float], origin: float = 0.0) -> list[fl
 class GridSystemDialog(QDialog):
     """Dialog for entering X/Y/Z grid-line coordinates."""
 
-    def __init__(self, next_node_id: int,
+    def __init__(
-                 existing: GridSystem | None = None,
+        self, next_node_id: int, existing: GridSystem | None = None, parent: QWidget | None = None
-                 parent: QWidget | None = None) -> None:
+    ) -> None:
         super().__init__(parent)
         self.setWindowTitle("Grid System")
         self._next_id = next_node_id
@@ -104,9 +104,7 @@ class GridSystemDialog(QDialog):
         self._visible_cb.setChecked(True)
         layout.addWidget(self._visible_cb)
 
-        self._generate_nodes_cb = QCheckBox(
+        self._generate_nodes_cb = QCheckBox("Also create nodes at every intersection")
-            "Also create nodes at every intersection"
-        )
         self._generate_nodes_cb.setChecked(False)
         layout.addWidget(self._generate_nodes_cb)
 
@@ -128,6 +126,7 @@ class GridSystemDialog(QDialog):
 
     def _load_existing(self, grid: GridSystem) -> None:
         """Pre-fill editors from an existing GridSystem (as spacings)."""
+
         def to_spacings_text(coords: list[float]) -> str:
             if not coords:
                 return ""
@@ -136,6 +135,7 @@ class GridSystemDialog(QDialog):
                 # Single line at nonzero origin — degenerate, show empty.
                 return ""
             return ", ".join(f"{s:g}" for s in spacings)
+
         self._x_edit.setText(to_spacings_text(grid.x_lines))
         self._y_edit.setText(to_spacings_text(grid.y_lines))
         self._z_edit.setText(to_spacings_text(grid.z_lines))
@@ -152,8 +152,7 @@ class GridSystemDialog(QDialog):
             else:
                 extra = "<br>Nodes will NOT be created automatically."
             self._preview.setText(
-                f"Grid: <b>{len(xs)}</b> × <b>{len(ys)}</b> × <b>{len(zs)}</b> lines."
+                f"Grid: <b>{len(xs)}</b> × <b>{len(ys)}</b> × <b>{len(zs)}</b> lines." f"{extra}"
-                f"{extra}"
             )
         except (ValueError, IndexError) as exc:
             self._preview.setText(f"<span style='color:red'>Parse error: {exc}</span>")

src/otko/views/dialogs/locate_origin.py

@@ -36,28 +36,35 @@ class CoordSystemLocationOrientationDialog(QDialog):
 
     def _build_ui(self) -> None:
         root = QVBoxLayout(self)
-        root.addWidget(QLabel(
+        root.addWidget(
-            "Enter the system's origin and orientation relative to <b>Global</b>. "
+            QLabel(
-            "Rotations are XYZ Euler angles in degrees."
+                "Enter the system's origin and orientation relative to <b>Global</b>. "
-        ))
+                "Rotations are XYZ Euler angles in degrees."
+            )
+        )
 
         origin_box = QGroupBox("Origin (world units)")
         of = QFormLayout(origin_box)
-        self._ox = self._spin(); of.addRow("X:", self._ox)
+        self._ox = self._spin()
-        self._oy = self._spin(); of.addRow("Y:", self._oy)
+        of.addRow("X:", self._ox)
-        self._oz = self._spin(); of.addRow("Z:", self._oz)
+        self._oy = self._spin()
+        of.addRow("Y:", self._oy)
+        self._oz = self._spin()
+        of.addRow("Z:", self._oz)
         root.addWidget(origin_box)
 
         rot_box = QGroupBox("Rotation about axes (degrees)")
         rf = QFormLayout(rot_box)
-        self._rx = self._rot_spin(); rf.addRow("about X:", self._rx)
+        self._rx = self._rot_spin()
-        self._ry = self._rot_spin(); rf.addRow("about Y:", self._ry)
+        rf.addRow("about X:", self._rx)
-        self._rz = self._rot_spin(); rf.addRow("about Z:", self._rz)
+        self._ry = self._rot_spin()
+        rf.addRow("about Y:", self._ry)
+        self._rz = self._rot_spin()
+        rf.addRow("about Z:", self._rz)
         root.addWidget(rot_box)
 
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)

src/otko/views/dialogs/material_forms.py

@@ -33,10 +33,16 @@ from otko.core import (
 
 
 # ─────────────────────────── helpers ───────────────────────────
-def _spin(default: float = 0.0, *, decimals: int = 6,
+def _spin(
-          minimum: float = -1e15, maximum: float = 1e15,
+    default: float = 0.0,
-          step: float = 1.0) -> QDoubleSpinBox:
+    *,
+    decimals: int = 6,
+    minimum: float = -1e15,
+    maximum: float = 1e15,
+    step: float = 1.0,
+) -> QDoubleSpinBox:
     from PySide6.QtCore import QLocale
+
     sb = QDoubleSpinBox()
     # Force C locale so "." is always the decimal separator.
     sb.setLocale(QLocale(QLocale.Language.C))
@@ -110,8 +116,11 @@ class Steel01Form(MaterialFormBase):
 
     def _read_specific(self, mid: int) -> Steel01:
         return Steel01(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            Fy=self._fy.value(), E0=self._e0.value(), b=self._b.value(),
+            name=self._name_edit.text(),
+            Fy=self._fy.value(),
+            E0=self._e0.value(),
+            b=self._b.value(),
         )
 
 
@@ -127,19 +136,34 @@ class Steel02Form(MaterialFormBase):
         self._r0 = _spin(18.0, decimals=2, minimum=10.0, maximum=20.0, step=0.5)
         self._cR1 = _spin(0.925, decimals=4, step=0.01)
         self._cR2 = _spin(0.15, decimals=4, step=0.01)
-        for label, w in (("Fy:", self._fy), ("E0:", self._e0), ("b:", self._b),
+        for label, w in (
-                         ("R0:", self._r0), ("cR1:", self._cR1), ("cR2:", self._cR2)):
+            ("Fy:", self._fy),
+            ("E0:", self._e0),
+            ("b:", self._b),
+            ("R0:", self._r0),
+            ("cR1:", self._cR1),
+            ("cR2:", self._cR2),
+        ):
             self._layout.addRow(label, w)
 
     def _populate_specific(self, m: Steel02) -> None:
-        self._fy.setValue(m.Fy); self._e0.setValue(m.E0); self._b.setValue(m.b)
+        self._fy.setValue(m.Fy)
-        self._r0.setValue(m.R0); self._cR1.setValue(m.cR1); self._cR2.setValue(m.cR2)
+        self._e0.setValue(m.E0)
+        self._b.setValue(m.b)
+        self._r0.setValue(m.R0)
+        self._cR1.setValue(m.cR1)
+        self._cR2.setValue(m.cR2)
 
     def _read_specific(self, mid: int) -> Steel02:
         return Steel02(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            Fy=self._fy.value(), E0=self._e0.value(), b=self._b.value(),
+            name=self._name_edit.text(),
-            R0=self._r0.value(), cR1=self._cR1.value(), cR2=self._cR2.value(),
+            Fy=self._fy.value(),
+            E0=self._e0.value(),
+            b=self._b.value(),
+            R0=self._r0.value(),
+            cR1=self._cR1.value(),
+            cR2=self._cR2.value(),
         )
 
 
@@ -156,19 +180,28 @@ class Concrete01Form(MaterialFormBase):
         self._epsc0 = _spin(-0.002, decimals=6, minimum=-1.0, maximum=0.0, step=1e-4)
         self._fpcu = _spin(-15e6, step=1.0, maximum=0.0)
         self._epsU = _spin(-0.005, decimals=6, minimum=-1.0, maximum=0.0, step=1e-4)
-        for label, w in (("f'c (-):", self._fpc), ("ε_c0 (-):", self._epsc0),
+        for label, w in (
-                         ("f'cu (-):", self._fpcu), ("ε_U (-):", self._epsU)):
+            ("f'c (-):", self._fpc),
+            ("ε_c0 (-):", self._epsc0),
+            ("f'cu (-):", self._fpcu),
+            ("ε_U (-):", self._epsU),
+        ):
             self._layout.addRow(label, w)
 
     def _populate_specific(self, m: Concrete01) -> None:
-        self._fpc.setValue(m.fpc); self._epsc0.setValue(m.epsc0)
+        self._fpc.setValue(m.fpc)
-        self._fpcu.setValue(m.fpcu); self._epsU.setValue(m.epsU)
+        self._epsc0.setValue(m.epsc0)
+        self._fpcu.setValue(m.fpcu)
+        self._epsU.setValue(m.epsU)
 
     def _read_specific(self, mid: int) -> Concrete01:
         return Concrete01(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            fpc=self._fpc.value(), epsc0=self._epsc0.value(),
+            name=self._name_edit.text(),
-            fpcu=self._fpcu.value(), epsU=self._epsU.value(),
+            fpc=self._fpc.value(),
+            epsc0=self._epsc0.value(),
+            fpcu=self._fpcu.value(),
+            epsU=self._epsU.value(),
         )
 
 
@@ -187,23 +220,36 @@ class Concrete02Form(MaterialFormBase):
         self._lambda = _spin(0.1, decimals=4, minimum=0.0, maximum=1.0, step=0.01)
         self._ft = _spin(3e6, step=1.0, minimum=1e-9)
         self._ets = _spin(2e9, step=1.0, minimum=1e-9)
-        for label, w in (("f'c (-):", self._fpc), ("ε_c0 (-):", self._epsc0),
+        for label, w in (
-                         ("f'cu (-):", self._fpcu), ("ε_U (-):", self._epsU),
+            ("f'c (-):", self._fpc),
-                         ("λ (unload ratio):", self._lambda),
+            ("ε_c0 (-):", self._epsc0),
-                         ("ft (tensile):", self._ft), ("Ets (soften):", self._ets)):
+            ("f'cu (-):", self._fpcu),
+            ("ε_U (-):", self._epsU),
+            ("λ (unload ratio):", self._lambda),
+            ("ft (tensile):", self._ft),
+            ("Ets (soften):", self._ets),
+        ):
             self._layout.addRow(label, w)
 
     def _populate_specific(self, m: Concrete02) -> None:
-        self._fpc.setValue(m.fpc); self._epsc0.setValue(m.epsc0)
+        self._fpc.setValue(m.fpc)
-        self._fpcu.setValue(m.fpcu); self._epsU.setValue(m.epsU)
+        self._epsc0.setValue(m.epsc0)
-        self._lambda.setValue(m.lambda_); self._ft.setValue(m.ft); self._ets.setValue(m.Ets)
+        self._fpcu.setValue(m.fpcu)
+        self._epsU.setValue(m.epsU)
+        self._lambda.setValue(m.lambda_)
+        self._ft.setValue(m.ft)
+        self._ets.setValue(m.Ets)
 
     def _read_specific(self, mid: int) -> Concrete02:
         return Concrete02(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            fpc=self._fpc.value(), epsc0=self._epsc0.value(),
+            name=self._name_edit.text(),
-            fpcu=self._fpcu.value(), epsU=self._epsU.value(),
+            fpc=self._fpc.value(),
-            ft=self._ft.value(), Ets=self._ets.value(),
+            epsc0=self._epsc0.value(),
+            fpcu=self._fpcu.value(),
+            epsU=self._epsU.value(),
+            ft=self._ft.value(),
+            Ets=self._ets.value(),
             **{"lambda": self._lambda.value()},
         )
 
@@ -243,9 +289,12 @@ class Concrete04Form(MaterialFormBase):
         fct_val = self._fct.value()
         et_val = self._et.value()
         return Concrete04(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            fpc=self._fpc.value(), epsc0=self._epsc0.value(),
+            name=self._name_edit.text(),
-            epscu=self._epscu.value(), Ec=self._Ec.value(),
+            fpc=self._fpc.value(),
+            epsc0=self._epsc0.value(),
+            epscu=self._epscu.value(),
+            Ec=self._Ec.value(),
             fct=fct_val if fct_val > 0.0 else None,
             et=et_val if et_val > 0.0 else None,
         )
@@ -263,12 +312,15 @@ class ElasticUniaxialForm(MaterialFormBase):
         self._layout.addRow("η (damping):", self._eta)
 
     def _populate_specific(self, m: ElasticUniaxial) -> None:
-        self._e.setValue(m.E); self._eta.setValue(m.eta)
+        self._e.setValue(m.E)
+        self._eta.setValue(m.eta)
 
     def _read_specific(self, mid: int) -> ElasticUniaxial:
         return ElasticUniaxial(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            E=self._e.value(), eta=self._eta.value(),
+            name=self._name_edit.text(),
+            E=self._e.value(),
+            eta=self._eta.value(),
         )
 
 
@@ -286,12 +338,17 @@ class ElasticIsotropicForm(MaterialFormBase):
         self._layout.addRow("ρ (density):", self._rho)
 
     def _populate_specific(self, m: ElasticIsotropic) -> None:
-        self._e.setValue(m.E); self._nu.setValue(m.nu); self._rho.setValue(m.rho)
+        self._e.setValue(m.E)
+        self._nu.setValue(m.nu)
+        self._rho.setValue(m.rho)
 
     def _read_specific(self, mid: int) -> ElasticIsotropic:
         return ElasticIsotropic(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            E=self._e.value(), nu=self._nu.value(), rho=self._rho.value(),
+            name=self._name_edit.text(),
+            E=self._e.value(),
+            nu=self._nu.value(),
+            rho=self._rho.value(),
         )
 
 
@@ -307,12 +364,15 @@ class ElasticPPForm(MaterialFormBase):
         self._layout.addRow("ε_y (yield strain):", self._epsy)
 
     def _populate_specific(self, m: ElasticPP) -> None:
-        self._e.setValue(m.E); self._epsy.setValue(m.epsy_pos)
+        self._e.setValue(m.E)
+        self._epsy.setValue(m.epsy_pos)
 
     def _read_specific(self, mid: int) -> ElasticPP:
         return ElasticPP(
-            id=mid, name=self._name_edit.text(),
+            id=mid,
-            E=self._e.value(), epsy_pos=self._epsy.value(),
+            name=self._name_edit.text(),
+            E=self._e.value(),
+            epsy_pos=self._epsy.value(),
         )
 
 

src/otko/views/dialogs/material_library.py

@@ -150,7 +150,12 @@ class MaterialLibraryDialog(QDialog):
             return
         kinds = list(FORM_REGISTRY.keys())
         kind, ok = QInputDialog.getItem(
-            self, "Add material", "Type:", kinds, current=0, editable=False,
+            self,
+            "Add material",
+            "Type:",
+            kinds,
+            current=0,
+            editable=False,
         )
         if not ok:
             return
@@ -179,9 +184,10 @@ class MaterialLibraryDialog(QDialog):
         if material is None:
             return
         reply = QMessageBox.question(
-            self, "Delete material",
+            self,
+            "Delete material",
             f"Delete material #{material.id} ({material.type})?\n"
-            "Elements that reference it will be invalid until reassigned."
+            "Elements that reference it will be invalid until reassigned.",
         )
         if reply != QMessageBox.StandardButton.Yes:
             return

src/otko/views/dialogs/mirror.py

@@ -24,12 +24,12 @@ class MirrorDialog(QDialog):
 
     def _build_ui(self, n_nodes: int, n_elements: int) -> None:
         layout = QVBoxLayout(self)
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            f"Mirror <b>{n_nodes}</b> node(s) and <b>{n_elements}</b> element(s)."
+            QLabel(f"Mirror <b>{n_nodes}</b> node(s) and <b>{n_elements}</b> element(s).")
-        ))
+        )
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            "<i>Only elements whose endpoints are both in the selection are copied.</i>"
+            QLabel("<i>Only elements whose endpoints are both in the selection are copied.</i>")
-        ))
+        )
 
         box = QGroupBox("Reflection plane (passes through origin)")
         box_layout = QVBoxLayout(box)

src/otko/views/dialogs/path_time_series.py

@@ -44,11 +44,13 @@ class PathTimeSeriesDialog(QDialog):
 
     def _build_ui(self) -> None:
         root = QVBoxLayout(self)
-        root.addWidget(QLabel(
+        root.addWidget(
-            "<b>Path TimeSeries</b> — tabulated values sampled at a "
+            QLabel(
-            "uniform time step. Used by UniformExcitation (ground "
+                "<b>Path TimeSeries</b> — tabulated values sampled at a "
-            "motion) and by PlainLoadPattern scaled forces."
+                "uniform time step. Used by UniformExcitation (ground "
-        ))
+                "motion) and by PlainLoadPattern scaled forces."
+            )
+        )
 
         form = QFormLayout()
         self._name_edit = QLineEdit("GroundMotion")
@@ -65,7 +67,7 @@ class PathTimeSeriesDialog(QDialog):
         self._factor_spin.setRange(-1e12, 1e12)
         self._factor_spin.setDecimals(6)
         self._factor_spin.setSingleStep(1.0)
-        self._factor_spin.setValue(386.4)     # default: convert g → in/s²
+        self._factor_spin.setValue(386.4)  # default: convert g → in/s²
         self._factor_spin.setToolTip(
             "Multiplier applied to every value at runtime. Typical use: "
             "386.4 for ground motion in g → in/s² (US_IN_KIP), 9.81 for "
@@ -84,9 +86,7 @@ class PathTimeSeriesDialog(QDialog):
         btn_row.addWidget(self._btn_plain)
         root.addLayout(btn_row)
 
-        self._status = QLabel(
+        self._status = QLabel("<i>No data loaded — use one of the import buttons.</i>")
-            "<i>No data loaded — use one of the import buttons.</i>"
-        )
         self._status.setWordWrap(True)
         self._status.setStyleSheet("color: #666;")
         root.addWidget(self._status)
@@ -102,8 +102,7 @@ class PathTimeSeriesDialog(QDialog):
         root.addWidget(self._preview, 1)
 
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self._on_accept)
         buttons.rejected.connect(self.reject)
@@ -112,8 +111,10 @@ class PathTimeSeriesDialog(QDialog):
     # ── file-import slots ───────────────────────────────────────────
     def _on_import_peer(self) -> None:
         fname, _ = QFileDialog.getOpenFileName(
-            self, "Import PEER record",
+            self,
-            "", "PEER records (*.at2 *.AT2);;All files (*)",
+            "Import PEER record",
+            "",
+            "PEER records (*.at2 *.AT2);;All files (*)",
         )
         if not fname:
             return
@@ -132,8 +133,10 @@ class PathTimeSeriesDialog(QDialog):
 
     def _on_import_plain(self) -> None:
         fname, _ = QFileDialog.getOpenFileName(
-            self, "Import plain values",
+            self,
-            "", "Text files (*.txt *.csv *.dat);;All files (*)",
+            "Import plain values",
+            "",
+            "Text files (*.txt *.csv *.dat);;All files (*)",
         )
         if not fname:
             return
@@ -144,8 +147,7 @@ class PathTimeSeriesDialog(QDialog):
             return
         self._values = vals
         self._status.setText(
-            f"Loaded <b>{len(vals)}</b> values from plain-text file. "
+            f"Loaded <b>{len(vals)}</b> values from plain-text file. " "Set Δt manually above."
-            "Set Δt manually above."
         )
         self._refresh_preview()
 
@@ -167,7 +169,9 @@ class PathTimeSeriesDialog(QDialog):
     def _on_accept(self) -> None:
         if not self._values:
             QMessageBox.warning(
-                self, "No data", "Import a record first.",
+                self,
+                "No data",
+                "Import a record first.",
             )
             return
         self.accept()

src/otko/views/dialogs/quick_grid_lines.py

@@ -31,39 +31,56 @@ class QuickGridLinesDialog(QDialog):
 
     def _build_ui(self) -> None:
         root = QVBoxLayout(self)
-        root.addWidget(QLabel(
+        root.addWidget(
-            "<b>Quick-define a regular (Cartesian) grid.</b><br>"
+            QLabel(
-            "Each axis: number of lines, equal spacing, first line coordinate."
+                "<b>Quick-define a regular (Cartesian) grid.</b><br>"
-        ))
+                "Each axis: number of lines, equal spacing, first line coordinate."
+            )
+        )
 
         self._x_n, self._x_s, self._x_f = self._axis_group("X Grid Data", root)
         self._y_n, self._y_s, self._y_f = self._axis_group("Y Grid Data", root)
         self._z_n, self._z_s, self._z_f = self._axis_group("Z Grid Data", root)
 
         # Sensible defaults.
-        self._x_n.setValue(3); self._x_s.setValue(6.0); self._x_f.setValue(0.0)
+        self._x_n.setValue(3)
-        self._y_n.setValue(3); self._y_s.setValue(6.0); self._y_f.setValue(0.0)
+        self._x_s.setValue(6.0)
-        self._z_n.setValue(2); self._z_s.setValue(3.0); self._z_f.setValue(0.0)
+        self._x_f.setValue(0.0)
+        self._y_n.setValue(3)
+        self._y_s.setValue(6.0)
+        self._y_f.setValue(0.0)
+        self._z_n.setValue(2)
+        self._z_s.setValue(3.0)
+        self._z_f.setValue(0.0)
 
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)
         root.addWidget(buttons)
 
     def _axis_group(
-        self, title: str, parent_layout: QVBoxLayout,
+        self,
+        title: str,
+        parent_layout: QVBoxLayout,
     ) -> tuple[QSpinBox, QDoubleSpinBox, QDoubleSpinBox]:
         box = QGroupBox(title)
         row = QHBoxLayout(box)
 
-        n = QSpinBox(); n.setRange(0, 200); n.setValue(3)
+        n = QSpinBox()
-        s = QDoubleSpinBox(); s.setRange(0.0, 1e6); s.setDecimals(4)
+        n.setRange(0, 200)
-        s.setSingleStep(0.5); s.setValue(1.0)
+        n.setValue(3)
-        f = QDoubleSpinBox(); f.setRange(-1e6, 1e6); f.setDecimals(4)
+        s = QDoubleSpinBox()
-        f.setSingleStep(0.5); f.setValue(0.0)
+        s.setRange(0.0, 1e6)
+        s.setDecimals(4)
+        s.setSingleStep(0.5)
+        s.setValue(1.0)
+        f = QDoubleSpinBox()
+        f.setRange(-1e6, 1e6)
+        f.setDecimals(4)
+        f.setSingleStep(0.5)
+        f.setValue(0.0)
 
         row.addWidget(QLabel("Number of lines:"))
         row.addWidget(n)
@@ -76,8 +93,10 @@ class QuickGridLinesDialog(QDialog):
 
     def ordinates(self) -> tuple[list[float], list[float], list[float]]:
         """Return (xs, ys, zs) — flat lists of ordinate values."""
+
         def axis(n: QSpinBox, s: QDoubleSpinBox, f: QDoubleSpinBox) -> list[float]:
             return [f.value() + i * s.value() for i in range(n.value())]
+
         return (
             axis(self._x_n, self._x_s, self._x_f),
             axis(self._y_n, self._y_s, self._y_f),

src/otko/views/dialogs/quick_guide.py

@@ -29,7 +29,7 @@ with <b>Define → Add Plain Load Pattern…</b> or
 <b>Define → Add Uniform Excitation…</b> for seismic input.</p>
 
 <h4>4&nbsp;— Draw the model</h4>
-<p>Tools toolbar (left): <b>Select</b>, <b>Draw Node</b> (F1),
+<p>Tools toolbar (top): <b>Select</b>, <b>Draw Node</b> (F1),
 <b>Draw Frame</b> (F2), <b>Draw Truss</b> (F3, icon-less by design).
 <b>Define → Coordinate System/Grids…</b> (Ctrl+G) and <b>Add Node…</b> (Ctrl+N)
 for precise layout; use the top-toolbar <b>Level</b> combo in Top/Front/Right views.</p>

src/otko/views/dialogs/replicate.py

@@ -42,12 +42,12 @@ class ReplicateDialog(QDialog):
 
     def _build_ui(self, n_nodes: int, n_elements: int) -> None:
         layout = QVBoxLayout(self)
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            f"Replicate <b>{n_nodes}</b> node(s) and <b>{n_elements}</b> element(s)."
+            QLabel(f"Replicate <b>{n_nodes}</b> node(s) and <b>{n_elements}</b> element(s).")
-        ))
+        )
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            "<i>Only elements whose endpoints are both in the selection are copied.</i>"
+            QLabel("<i>Only elements whose endpoints are both in the selection are copied.</i>")
-        ))
+        )
 
         form = QFormLayout()
 

src/otko/views/dialogs/run_analysis.py

@@ -57,6 +57,18 @@ class RunAnalysisDialog(QDialog):
         row.addWidget(self._case_combo, stretch=1)
         layout.addLayout(row)
 
+        combo_row = QHBoxLayout()
+        combo_row.addWidget(QLabel("Combination:"))
+        self._combo_combo = QComboBox()
+        combo_row.addWidget(self._combo_combo, stretch=1)
+        self._eval_btn = QPushButton("Evaluate")
+        self._eval_btn.setToolTip(
+            "Run each referenced static case, then combine results "
+            "in post-processing (linear superposition, no extra solver input)."
+        )
+        combo_row.addWidget(self._eval_btn)
+        layout.addLayout(combo_row)
+
         # Run-time damping overrides for transient cases only.
         self._damping_box = QGroupBox("Rayleigh damping (transient only)")
         form = QFormLayout(self._damping_box)
@@ -79,12 +91,14 @@ class RunAnalysisDialog(QDialog):
         self._mode1_damping.setSingleStep(0.01)
         form.addRow("Mode-1 damping zeta:", self._mode1_damping)
 
-        form.addRow(QLabel(
+        form.addRow(
-            "<i>Values are applied for this run only via a copy of the case — "
+            QLabel(
-            "the stored case is not modified. If mode-1 damping is "
+                "<i>Values are applied for this run only via a copy of the case — "
-            "greater than zero, the runner computes betaK from the first "
+                "the stored case is not modified. If mode-1 damping is "
-            "mode after preload and overrides the manual betaK value.</i>",
+                "greater than zero, the runner computes betaK from the first "
-        ))
+                "mode after preload and overrides the manual betaK value.</i>",
+            )
+        )
         layout.addWidget(self._damping_box)
 
         self._progress = QProgressBar()
@@ -98,7 +112,8 @@ class RunAnalysisDialog(QDialog):
         layout.addWidget(self._log, stretch=1)
 
         self._buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Close, parent=self,
+            QDialogButtonBox.StandardButton.Close,
+            parent=self,
         )
         self._run_btn = QPushButton("Run")
         self._buttons.addButton(self._run_btn, QDialogButtonBox.ButtonRole.ActionRole)
@@ -106,6 +121,7 @@ class RunAnalysisDialog(QDialog):
 
     def _wire(self) -> None:
         self._run_btn.clicked.connect(self._on_run)
+        self._eval_btn.clicked.connect(self._on_evaluate_combo)
         self._buttons.rejected.connect(self.reject)
         self._case_combo.currentIndexChanged.connect(self._on_case_changed)
 
@@ -133,15 +149,21 @@ class RunAnalysisDialog(QDialog):
 
     def _populate_cases(self) -> None:
         self._case_combo.clear()
+        self._combo_combo.clear()
         if self._vm.project is None:
             self._run_btn.setEnabled(False)
+            self._eval_btn.setEnabled(False)
             self._damping_box.setVisible(False)
             return
         for case in self._vm.project.analyses:
             label = f"#{case.id}  {case.name or '(unnamed)'}  [{case.type}]"
             self._case_combo.addItem(label, userData=case.id)
+        for combo in self._vm.project.combinations:
+            label = f"#{combo.id}  {combo.name or '(unnamed)'}  [{combo.kind}]"
+            self._combo_combo.addItem(label, userData=combo.id)
         has_cases = self._case_combo.count() > 0
         self._run_btn.setEnabled(has_cases)
+        self._eval_btn.setEnabled(self._combo_combo.count() > 0)
         if not has_cases:
             # No transient case can be selected, so the run-only damping
             # overrides are meaningless — hide them alongside the disabled Run.
@@ -157,11 +179,13 @@ class RunAnalysisDialog(QDialog):
             return
         if case.type == "Transient":
             mode1 = float(self._mode1_damping.value())
-            case = case.model_copy(update={
+            case = case.model_copy(
-                "rayleigh_alpha_m": float(self._alpha_m.value()),
+                update={
-                "rayleigh_beta_k": float(self._beta_k.value()),
+                    "rayleigh_alpha_m": float(self._alpha_m.value()),
-                "rayleigh_mode1_damping": mode1 if mode1 > 0.0 else None,
+                    "rayleigh_beta_k": float(self._beta_k.value()),
-            })
+                    "rayleigh_mode1_damping": mode1 if mode1 > 0.0 else None,
+                }
+            )
         self._results = None
         self._log.clear()
         results_dir: Path | None = None
@@ -172,6 +196,49 @@ class RunAnalysisDialog(QDialog):
         except Exception as exc:  # noqa: BLE001
             self._log.appendPlainText(f"Could not start: {exc}")
 
+    def _on_evaluate_combo(self) -> None:
+        """Run each referenced static case, then combine in post-processing.
+
+        Synchronous (linear statics are fast): each case runs through
+        :class:`OpenSeesRunner` on the GUI thread, then
+        :func:`evaluate_combination` superposes the results. The combined
+        output is forwarded through ``runner.finished`` so the main
+        window displays it like any other result.
+        """
+        from otko.services.combinations import evaluate_combination
+        from otko.services.opensees_runner import OpenSeesRunner
+
+        if self._runner.is_running or self._vm.project is None:
+            return
+        combo_id = self._combo_combo.currentData()
+        project = self._vm.project
+        combo = next((c for c in project.combinations if c.id == combo_id), None)
+        if combo is None:
+            return
+        self._results = None
+        self._log.clear()
+        self._log.appendPlainText(f"Evaluating combination '{combo.name}' [{combo.kind}] ...")
+        try:
+            case_by_id = {c.id: c for c in project.analyses}
+            collected: dict[int, Any] = {}
+            for item in combo.items:
+                case = case_by_id.get(item.case_id)
+                if case is None:
+                    raise ValueError(f"Combination references missing case id={item.case_id}.")
+                self._log.appendPlainText(
+                    f"  running case #{case.id} '{case.name}' × {item.factor:g} ..."
+                )
+                collected[item.case_id] = OpenSeesRunner(project).run(case)
+            combined = evaluate_combination(collected, combo)
+            self._results = combined
+            self._log.appendPlainText(f"--- Done. Returned {type(combined).__name__}. ---")
+            self._runner.finished.emit(combined)
+        except Exception as exc:  # noqa: BLE001
+            import traceback
+
+            self._log.appendPlainText("--- FAILED ---")
+            self._log.appendPlainText(f"{exc}\n{traceback.format_exc()}")
+
     def _on_started(self) -> None:
         self._log.appendPlainText("--- Analysis started ---")
 
@@ -191,4 +258,6 @@ class RunAnalysisDialog(QDialog):
         self._progress.setVisible(running)
         # With zero cases Run must stay disabled even when idle.
         self._run_btn.setEnabled((not running) and self._case_combo.count() > 0)
+        self._eval_btn.setEnabled((not running) and self._combo_combo.count() > 0)
         self._case_combo.setEnabled(not running)
+        self._combo_combo.setEnabled(not running)

src/otko/views/dialogs/section_editor.py

@@ -45,22 +45,31 @@ from otko.services.section_properties import (
 )
 
 _PATCH_COLORS = [
-    "#4e79a7", "#f28e2b", "#e15759", "#76b7b2",
+    "#4e79a7",
-    "#59a14f", "#edc948", "#b07aa1", "#ff9da7",
+    "#f28e2b",
+    "#e15759",
+    "#76b7b2",
+    "#59a14f",
+    "#edc948",
+    "#b07aa1",
+    "#ff9da7",
 ]
 
 
 class FiberSectionEditor(QDialog):
     """Modal dialog: build a FiberSection from patches + layers."""
 
-    def __init__(self, material_ids: list[int],
+    def __init__(
-                 existing: FiberSection | None = None,
+        self,
-                 parent: QWidget | None = None) -> None:
+        material_ids: list[int],
+        existing: FiberSection | None = None,
+        parent: QWidget | None = None,
+    ) -> None:
         super().__init__(parent)
         self.setWindowTitle("Fiber Section Editor")
         self.resize(1000, 650)
         self._material_ids = material_ids
-        self._patches: list[Any] = []      # RectangularPatch | CircularPatch
+        self._patches: list[Any] = []  # RectangularPatch | CircularPatch
         self._layers: list[StraightLayer] = []
         self._section_id: int = existing.id if existing else 1
         self._section_name: str = existing.name if existing else ""
@@ -106,25 +115,37 @@ class FiberSectionEditor(QDialog):
         pf.addRow("Material:", self._patch_mat)
 
         # Rect fields
-        self._rect_yi = self._spin(-0.15); self._rect_zi = self._spin(-0.15)
+        self._rect_yi = self._spin(-0.15)
-        self._rect_yj = self._spin(0.15);  self._rect_zj = self._spin(0.15)
+        self._rect_zi = self._spin(-0.15)
-        self._rect_ny = self._ispin(8);    self._rect_nz = self._ispin(8)
+        self._rect_yj = self._spin(0.15)
+        self._rect_zj = self._spin(0.15)
+        self._rect_ny = self._ispin(8)
+        self._rect_nz = self._ispin(8)
         self._rect_rows = [
-            ("y_i:", self._rect_yi), ("z_i:", self._rect_zi),
+            ("y_i:", self._rect_yi),
-            ("y_j:", self._rect_yj), ("z_j:", self._rect_zj),
+            ("z_i:", self._rect_zi),
-            ("n_fib_y:", self._rect_ny), ("n_fib_z:", self._rect_nz),
+            ("y_j:", self._rect_yj),
+            ("z_j:", self._rect_zj),
+            ("n_fib_y:", self._rect_ny),
+            ("n_fib_z:", self._rect_nz),
         ]
         for label, widget in self._rect_rows:
             pf.addRow(label, widget)
 
         # Circ fields (initially hidden)
-        self._circ_yc = self._spin(0.0); self._circ_zc = self._spin(0.0)
+        self._circ_yc = self._spin(0.0)
-        self._circ_ri = self._spin(0.0); self._circ_ro = self._spin(0.15)
+        self._circ_zc = self._spin(0.0)
-        self._circ_nc = self._ispin(16); self._circ_nr = self._ispin(4)
+        self._circ_ri = self._spin(0.0)
+        self._circ_ro = self._spin(0.15)
+        self._circ_nc = self._ispin(16)
+        self._circ_nr = self._ispin(4)
         self._circ_rows = [
-            ("y_center:", self._circ_yc), ("z_center:", self._circ_zc),
+            ("y_center:", self._circ_yc),
-            ("r_inner:", self._circ_ri), ("r_outer:", self._circ_ro),
+            ("z_center:", self._circ_zc),
-            ("n_circ:", self._circ_nc), ("n_rad:", self._circ_nr),
+            ("r_inner:", self._circ_ri),
+            ("r_outer:", self._circ_ro),
+            ("n_circ:", self._circ_nc),
+            ("n_rad:", self._circ_nr),
         ]
         for label, widget in self._circ_rows:
             pf.addRow(label, widget)
@@ -145,12 +166,16 @@ class FiberSectionEditor(QDialog):
         lf.addRow("Material:", self._layer_mat)
         self._layer_nbars = self._ispin(4)
         self._layer_area = self._spin(0.0005, step=0.0001, minimum=1e-12)
-        self._layer_ys = self._spin(-0.12); self._layer_zs = self._spin(-0.12)
+        self._layer_ys = self._spin(-0.12)
-        self._layer_ye = self._spin(0.12);  self._layer_ze = self._spin(-0.12)
+        self._layer_zs = self._spin(-0.12)
+        self._layer_ye = self._spin(0.12)
+        self._layer_ze = self._spin(-0.12)
         lf.addRow("n_bars:", self._layer_nbars)
         lf.addRow("bar_area:", self._layer_area)
-        lf.addRow("y_start:", self._layer_ys); lf.addRow("z_start:", self._layer_zs)
+        lf.addRow("y_start:", self._layer_ys)
-        lf.addRow("y_end:", self._layer_ye); lf.addRow("z_end:", self._layer_ze)
+        lf.addRow("z_start:", self._layer_zs)
+        lf.addRow("y_end:", self._layer_ye)
+        lf.addRow("z_end:", self._layer_ze)
         self._add_layer_btn = QPushButton("Add layer")
         self._add_layer_btn.clicked.connect(self._on_add_layer)
         lf.addRow(self._add_layer_btn)
@@ -197,8 +222,7 @@ class FiberSectionEditor(QDialog):
 
     # ── helpers ─────────────────────────────────────────────────────
     @staticmethod
-    def _spin(default: float = 0.0, *, step: float = 0.01,
+    def _spin(default: float = 0.0, *, step: float = 0.01, minimum: float = -1e6) -> QDoubleSpinBox:
-              minimum: float = -1e6) -> QDoubleSpinBox:
         sb = QDoubleSpinBox()
         sb.setRange(minimum, 1e6)
         sb.setDecimals(6)
@@ -214,7 +238,7 @@ class FiberSectionEditor(QDialog):
         return sb
 
     def _on_patch_type_changed(self, idx: int) -> None:
-        is_rect = (idx == 0)
+        is_rect = idx == 0
         for _, w in self._rect_rows:
             w.setVisible(is_rect)
         for _, w in self._circ_rows:
@@ -226,28 +250,38 @@ class FiberSectionEditor(QDialog):
         if self._patch_type.currentIndex() == 0:
             p = RectangularPatch(
                 material_id=mid,
-                n_fib_y=self._rect_ny.value(), n_fib_z=self._rect_nz.value(),
+                n_fib_y=self._rect_ny.value(),
-                y_i=self._rect_yi.value(), z_i=self._rect_zi.value(),
+                n_fib_z=self._rect_nz.value(),
-                y_j=self._rect_yj.value(), z_j=self._rect_zj.value(),
+                y_i=self._rect_yi.value(),
+                z_i=self._rect_zi.value(),
+                y_j=self._rect_yj.value(),
+                z_j=self._rect_zj.value(),
             )
             self._patches.append(p)
-            self._item_list.addItem(QListWidgetItem(
+            self._item_list.addItem(
-                f"Rect patch  mat={mid}  "
+                QListWidgetItem(
-                f"({p.y_i:.3f},{p.z_i:.3f})→({p.y_j:.3f},{p.z_j:.3f})  "
+                    f"Rect patch  mat={mid}  "
-                f"{p.n_fib_y}×{p.n_fib_z}",
+                    f"({p.y_i:.3f},{p.z_i:.3f})→({p.y_j:.3f},{p.z_j:.3f})  "
-            ))
+                    f"{p.n_fib_y}×{p.n_fib_z}",
+                )
+            )
         else:
             p = CircularPatch(
                 material_id=mid,
-                n_fib_circ=self._circ_nc.value(), n_fib_rad=self._circ_nr.value(),
+                n_fib_circ=self._circ_nc.value(),
-                y_center=self._circ_yc.value(), z_center=self._circ_zc.value(),
+                n_fib_rad=self._circ_nr.value(),
-                r_inner=self._circ_ri.value(), r_outer=self._circ_ro.value(),
+                y_center=self._circ_yc.value(),
+                z_center=self._circ_zc.value(),
+                r_inner=self._circ_ri.value(),
+                r_outer=self._circ_ro.value(),
             )
             self._patches.append(p)
-            self._item_list.addItem(QListWidgetItem(
+            self._item_list.addItem(
-                f"Circ patch  mat={mid}  "
+                QListWidgetItem(
-                f"r={p.r_inner:.3f}→{p.r_outer:.3f}  {p.n_fib_circ}×{p.n_fib_rad}",
+                    f"Circ patch  mat={mid}  "
-            ))
+                    f"r={p.r_inner:.3f}→{p.r_outer:.3f}  {p.n_fib_circ}×{p.n_fib_rad}",
+                )
+            )
         self._refresh_preview()
 
     def _on_add_layer(self) -> None:
@@ -256,13 +290,17 @@ class FiberSectionEditor(QDialog):
             material_id=mid,
             n_bars=self._layer_nbars.value(),
             bar_area=self._layer_area.value(),
-            y_start=self._layer_ys.value(), z_start=self._layer_zs.value(),
+            y_start=self._layer_ys.value(),
-            y_end=self._layer_ye.value(), z_end=self._layer_ze.value(),
+            z_start=self._layer_zs.value(),
+            y_end=self._layer_ye.value(),
+            z_end=self._layer_ze.value(),
         )
         self._layers.append(lay)
-        self._item_list.addItem(QListWidgetItem(
+        self._item_list.addItem(
-            f"Layer  mat={mid}  {lay.n_bars} bars  A={lay.bar_area:.4g}",
+            QListWidgetItem(
-        ))
+                f"Layer  mat={mid}  {lay.n_bars} bars  A={lay.bar_area:.4g}",
+            )
+        )
         self._refresh_preview()
 
     def _on_remove(self) -> None:
@@ -280,8 +318,7 @@ class FiberSectionEditor(QDialog):
     # ── preview ─────────────────────────────────────────────────────
     def _refresh_preview(self) -> None:
         self._preview.clear()
-        sec = FiberSection(id=999999, patches=list(self._patches),
+        sec = FiberSection(id=999999, patches=list(self._patches), layers=list(self._layers))
-                           layers=list(self._layers))
         props = compute_section_props(sec)
         if props.n_fibres == 0:
             self._props_label.setText("Add patches or layers to see the preview.")
@@ -295,8 +332,9 @@ class FiberSectionEditor(QDialog):
         for lay in self._layers:
             mat_ids.append(lay.material_id)
         unique_mats = sorted(set(mat_ids)) if mat_ids else [1]
-        mat_to_color = {mid: _PATCH_COLORS[i % len(_PATCH_COLORS)]
+        mat_to_color = {
-                        for i, mid in enumerate(unique_mats)}
+            mid: _PATCH_COLORS[i % len(_PATCH_COLORS)] for i, mid in enumerate(unique_mats)
+        }
 
         # Draw patch fibres as squares, layer fibres as circles.
         # Expand per-patch for color assignment.
@@ -307,9 +345,13 @@ class FiberSectionEditor(QDialog):
                 continue
             color = mat_to_color.get(p.material_id, "#888888")
             self._preview.plot(
-                sub[:, 0], sub[:, 1],
+                sub[:, 0],
-                pen=None, symbol="s", symbolSize=6,
+                sub[:, 1],
-                symbolBrush=color, symbolPen=None,
+                pen=None,
+                symbol="s",
+                symbolSize=6,
+                symbolBrush=color,
+                symbolPen=None,
             )
         for lay in self._layers:
             sub_sec = FiberSection(id=999999, layers=[lay])
@@ -318,16 +360,24 @@ class FiberSectionEditor(QDialog):
                 continue
             color = mat_to_color.get(lay.material_id, "#ff0000")
             self._preview.plot(
-                sub[:, 0], sub[:, 1],
+                sub[:, 0],
-                pen=None, symbol="o", symbolSize=8,
+                sub[:, 1],
-                symbolBrush=color, symbolPen=pg.mkPen("#ffffff", width=1),
+                pen=None,
+                symbol="o",
+                symbolSize=8,
+                symbolBrush=color,
+                symbolPen=pg.mkPen("#ffffff", width=1),
             )
 
         # Centroid marker
         self._preview.plot(
-            [props.centroid_y], [props.centroid_z],
+            [props.centroid_y],
-            pen=None, symbol="+", symbolSize=16,
+            [props.centroid_z],
-            symbolBrush=None, symbolPen=pg.mkPen("#ff0000", width=2),
+            pen=None,
+            symbol="+",
+            symbolSize=16,
+            symbolBrush=None,
+            symbolPen=pg.mkPen("#ff0000", width=2),
         )
 
         self._props_label.setText(
@@ -341,16 +391,22 @@ class FiberSectionEditor(QDialog):
         for p in sec.patches:
             self._patches.append(p)
             if isinstance(p, RectangularPatch):
-                self._item_list.addItem(QListWidgetItem(
+                self._item_list.addItem(
-                    f"Rect patch mat={p.material_id} {p.n_fib_y}×{p.n_fib_z}",
+                    QListWidgetItem(
-                ))
+                        f"Rect patch mat={p.material_id} {p.n_fib_y}×{p.n_fib_z}",
+                    )
+                )
             elif isinstance(p, CircularPatch):
-                self._item_list.addItem(QListWidgetItem(
+                self._item_list.addItem(
-                    f"Circ patch mat={p.material_id} {p.n_fib_circ}×{p.n_fib_rad}",
+                    QListWidgetItem(
-                ))
+                        f"Circ patch mat={p.material_id} {p.n_fib_circ}×{p.n_fib_rad}",
+                    )
+                )
         for lay in sec.layers:
             if isinstance(lay, StraightLayer):
                 self._layers.append(lay)
-                self._item_list.addItem(QListWidgetItem(
+                self._item_list.addItem(
-                    f"Layer mat={lay.material_id} {lay.n_bars} bars",
+                    QListWidgetItem(
-                ))
+                        f"Layer mat={lay.material_id} {lay.n_bars} bars",
+                    )
+                )

src/otko/views/dialogs/section_forms.py

@@ -25,9 +25,14 @@ from otko.core import (
 )
 
 
-def _spin(default: float = 0.0, *, decimals: int = 8,
+def _spin(
-          minimum: float = 1e-12, maximum: float = 1e15,
+    default: float = 0.0,
-          step: float = 1.0) -> QDoubleSpinBox:
+    *,
+    decimals: int = 8,
+    minimum: float = 1e-12,
+    maximum: float = 1e15,
+    step: float = 1.0,
+) -> QDoubleSpinBox:
     sb = QDoubleSpinBox()
     sb.setRange(minimum, maximum)
     sb.setDecimals(decimals)
@@ -107,9 +112,14 @@ class ElasticSectionForm(SectionFormBase):
         self._iy = _spin(8.33e-6, step=1e-7)
         self._g = _spin(80e9, step=1e9)
         self._j = _spin(1e-6, step=1e-7)
-        for label, w in (("E:", self._e), ("A:", self._a),
+        for label, w in (
-                         ("Iz:", self._iz), ("Iy:", self._iy),
+            ("E:", self._e),
-                         ("G:", self._g), ("J:", self._j)):
+            ("A:", self._a),
+            ("Iz:", self._iz),
+            ("Iy:", self._iy),
+            ("G:", self._g),
+            ("J:", self._j),
+        ):
             self._layout.addRow(label, w)
         self._layout.addRow(QLabel("<i>Iy, G, J required for 3D models.</i>"))
 
@@ -196,10 +206,12 @@ class FiberSectionSummaryForm(SectionFormBase):
         self._summary.setWordWrap(True)
         self._summary.setStyleSheet("color: #555;")
         self._layout.addRow(self._summary)
-        self._layout.addRow(QLabel(
+        self._layout.addRow(
-            "<i>Edit this fiber section from the Section Library list — "
+            QLabel(
-            "Add / Modify uses the visual Fiber Section Editor.</i>"
+                "<i>Edit this fiber section from the Section Library list — "
-        ))
+                "Add / Modify uses the visual Fiber Section Editor.</i>"
+            )
+        )
         self._cached: FiberSection | None = None
 
     def _populate_specific(self, s: FiberSection) -> None:
@@ -240,9 +252,9 @@ class SectionAggregatorSummaryForm(SectionFormBase):
 
     def _populate_specific(self, s: SectionAggregator) -> None:
         self._cached = s
-        pairings = "<br>".join(
+        pairings = (
-            f"  mat #{p.material_id} on DOF {p.dof}" for p in s.pairings
+            "<br>".join(f"  mat #{p.material_id} on DOF {p.dof}" for p in s.pairings) or "(none)"
-        ) or "(none)"
+        )
         self._summary.setText(
             f"<b>{s.name or 'Section Aggregator'}</b><br>"
             f"Wraps section: {s.section_id}<br>"
@@ -268,10 +280,9 @@ def form_for(section: Any) -> SectionFormBase:
         # Graceful fallback — unknown section types display a minimal
         # placeholder instead of crashing the entire dialog.
         form = SectionFormBase()
-        form._layout.addRow(QLabel(
+        form._layout.addRow(
-            f"<i>No form registered for section type "
+            QLabel(f"<i>No form registered for section type " f"<b>{section.type}</b> yet.</i>")
-            f"<b>{section.type}</b> yet.</i>"
+        )
-        ))
         form._section_id = section.id
         form._name_edit.setText(getattr(section, "name", "") or "")
         form._name_edit.setEnabled(False)

src/otko/views/dialogs/section_library.py

@@ -113,6 +113,7 @@ class SectionLibraryDialog(QDialog):
         """
         from otko.core import FiberSection
         from otko.views.dialogs.section_editor import FiberSectionEditor
+
         sec = self._selected_section()
         if not isinstance(sec, FiberSection) or self._vm.project is None:
             return
@@ -156,7 +157,12 @@ class SectionLibraryDialog(QDialog):
         summary_kinds = {"FiberSection", "SectionAggregator"}
         kinds = [k for k in FORM_REGISTRY if k not in summary_kinds]
         kind, ok = QInputDialog.getItem(
-            self, "Add section", "Type:", kinds, current=0, editable=False,
+            self,
+            "Add section",
+            "Type:",
+            kinds,
+            current=0,
+            editable=False,
         )
         if not ok:
             return
@@ -176,6 +182,7 @@ class SectionLibraryDialog(QDialog):
         if self._vm.project is None:
             return
         from otko.views.dialogs.section_editor import FiberSectionEditor
+
         mat_ids = [m.id for m in self._vm.project.materials]
         new_id = self._vm.project.next_section_id()
         dlg = FiberSectionEditor(mat_ids, parent=self)
@@ -196,9 +203,10 @@ class SectionLibraryDialog(QDialog):
         if section is None:
             return
         reply = QMessageBox.question(
-            self, "Delete section",
+            self,
+            "Delete section",
             f"Delete section #{section.id} ({section.type})?\n"
-            "Frame elements that reference it will be invalid until reassigned."
+            "Frame elements that reference it will be invalid until reassigned.",
         )
         if reply != QMessageBox.StandardButton.Yes:
             return

src/otko/views/dialogs/uniform_excitation.py

@@ -51,10 +51,12 @@ class UniformExcitationDialog(QDialog):
 
     def _build_ui(self) -> None:
         root = QVBoxLayout(self)
-        root.addWidget(QLabel(
+        root.addWidget(
-            "<b>UniformExcitation</b> — apply a base ground motion "
+            QLabel(
-            "to every free node in the chosen DOF direction."
+                "<b>UniformExcitation</b> — apply a base ground motion "
-        ))
+                "to every free node in the chosen DOF direction."
+            )
+        )
 
         form = QFormLayout()
         self._name_edit = QLineEdit("GroundMotion")
@@ -84,16 +86,13 @@ class UniformExcitationDialog(QDialog):
         self._factor_spin.setDecimals(6)
         self._factor_spin.setSingleStep(0.1)
         self._factor_spin.setValue(1.0)
-        self._factor_spin.setToolTip(
+        self._factor_spin.setToolTip("Extra scale applied on top of the TimeSeries' own factor.")
-            "Extra scale applied on top of the TimeSeries' own factor."
-        )
         form.addRow("Factor:", self._factor_spin)
 
         root.addLayout(form)
 
         buttons = QDialogButtonBox(
-            QDialogButtonBox.StandardButton.Ok
+            QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel,
-            | QDialogButtonBox.StandardButton.Cancel,
         )
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)

src/otko/views/dock_manager.py

@@ -11,7 +11,7 @@ from __future__ import annotations
 from contextlib import suppress
 
 from PySide6.QtCore import Qt
-from PySide6.QtWidgets import QDockWidget, QMessageBox, QPlainTextEdit, QTreeWidget, QTreeWidgetItem
+from PySide6.QtWidgets import QDockWidget, QMessageBox, QTreeWidget, QTreeWidgetItem
 
 from otko.services.deformation import (
     linear_static_auto_scale,
@@ -34,6 +34,7 @@ from otko.services.results import (
 )
 from otko.views.canvas3d.model_renderer import RendererMode
 from otko.views.docks import (
+    ConsoleDock,
     DeformedShapeView,
     ForceDiagramView,
     HysteresisView,
@@ -103,13 +104,9 @@ class DockManager:
         self.tabifyDockWidget(props_dock, tree_dock)
         tree_dock.raise_()
 
-        self._console = QPlainTextEdit()
+        self._console_dock = ConsoleDock(self)
-        self._console.setReadOnly(True)
+        self._console = self._console_dock.view
-        self._console.setPlaceholderText("Logs and OpenSeesPy output will appear here.")
+        self.addDockWidget(Qt.DockWidgetArea.BottomDockWidgetArea, self._console_dock)
-        console_dock = QDockWidget("Console", self)
-        console_dock.setWidget(self._console)
-        self.addDockWidget(Qt.DockWidgetArea.BottomDockWidgetArea, console_dock)
-        self._console_dock = console_dock
 
         self._table = TableDock()
         table_dock = QDockWidget("Table", self)
@@ -122,7 +119,7 @@ class DockManager:
         results_dock.setWidget(self._results_panel)
         self.addDockWidget(Qt.DockWidgetArea.BottomDockWidgetArea, results_dock)
         self._results_dock = results_dock
-        self.tabifyDockWidget(console_dock, table_dock)
+        self.tabifyDockWidget(self._console_dock, table_dock)
         self.tabifyDockWidget(table_dock, results_dock)
         table_dock.raise_()
 

src/otko/views/docks/__init__.py

@@ -1,5 +1,6 @@
 """Reusable dock widget contents."""
 
+from otko.views.docks.console import ConsoleDock
 from otko.views.docks.deformed_shape import DeformedShapeView
 from otko.views.docks.force_diagram import ForceDiagramView
 from otko.views.docks.hysteresis import HysteresisView
@@ -12,8 +13,15 @@ from otko.views.docks.table_dock import TableDock
 from otko.views.docks.time_history import TimeHistoryView
 
 __all__ = [
-    "PropertyEditorDock", "ResultsPanel", "TableDock",
+    "PropertyEditorDock",
-    "DeformedShapeView", "ModeShapeAnimator",
+    "ResultsPanel",
-    "ForceDiagramView", "TimeHistoryView", "HysteresisView",
+    "TableDock",
-    "PushoverCurveView", "ResponseSpectrumView",
+    "DeformedShapeView",
+    "ModeShapeAnimator",
+    "ForceDiagramView",
+    "TimeHistoryView",
+    "HysteresisView",
+    "PushoverCurveView",
+    "ResponseSpectrumView",
+    "ConsoleDock",
 ]

src/otko/views/docks/deformed_shape.py

@@ -31,8 +31,7 @@ class DeformedShapeView(QWidget):
     scaleChanged = Signal(float)
     closed = Signal()
 
-    def __init__(self, suggested_scale: float = 1.0,
+    def __init__(self, suggested_scale: float = 1.0, parent: QWidget | None = None) -> None:
-                 parent: QWidget | None = None) -> None:
         super().__init__(parent)
         self._suggested = max(suggested_scale, 1e-6)
         self._build_ui()
@@ -41,9 +40,9 @@ class DeformedShapeView(QWidget):
         layout = QVBoxLayout(self)
         layout.setContentsMargins(8, 8, 8, 8)
         layout.addWidget(QLabel("<b>Deformed Shape</b>"))
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            "<i>The slider scales displacement around the suggested factor.</i>"
+            QLabel("<i>The slider scales displacement around the suggested factor.</i>")
-        ))
+        )
 
         form = QFormLayout()
 
@@ -53,8 +52,8 @@ class DeformedShapeView(QWidget):
 
         # Multiplier ranging 0.1× — 10× the suggested scale.
         self._slider = QSlider(Qt.Orientation.Horizontal)
-        self._slider.setRange(1, 1000)   # represents 0.01 — 10.00
+        self._slider.setRange(1, 1000)  # represents 0.01 — 10.00
-        self._slider.setValue(100)        # 1.00 ×
+        self._slider.setValue(100)  # 1.00 ×
         self._slider.valueChanged.connect(self._on_slider)
 
         self._spin = QDoubleSpinBox()

src/otko/views/docks/force_diagram.py

@@ -31,12 +31,11 @@ from otko.services.element_forces import ForceComponent
 class ForceDiagramView(QWidget):
     """Compact controls for live-updating an element-force diagram."""
 
-    componentChanged = Signal(object)       # ForceComponent
+    componentChanged = Signal(object)  # ForceComponent
-    changed = Signal(object, float)         # (ForceComponent, scale)
+    changed = Signal(object, float)  # (ForceComponent, scale)
     closed = Signal()
 
-    def __init__(self, suggested_scale: float = 1.0,
+    def __init__(self, suggested_scale: float = 1.0, parent: QWidget | None = None) -> None:
-                 parent: QWidget | None = None) -> None:
         super().__init__(parent)
         self._scale_base = max(suggested_scale, 1e-12)
         self._pending_component_change = False
@@ -87,7 +86,7 @@ class ForceDiagramView(QWidget):
 
         self._slider = QSlider(Qt.Orientation.Horizontal)
         self._slider.setRange(1, 1000)
-        self._slider.setValue(500)              # midpoint = suggested scale
+        self._slider.setValue(500)  # midpoint = suggested scale
         form.addRow("", self._slider)
 
         root.addWidget(group)

src/otko/views/docks/property_editor.py

@@ -32,8 +32,11 @@ from otko.core import Project
 # uniaxial material + area. The Convert command drops/adds fields to
 # bridge between them.
 _CONVERTIBLE_ELEMENT_TYPES = [
-    "Truss", "CorotTruss",
+    "Truss",
-    "ElasticBeamColumn", "ForceBeamColumn", "DispBeamColumn",
+    "CorotTruss",
+    "ElasticBeamColumn",
+    "ForceBeamColumn",
+    "DispBeamColumn",
 ]
 
 
@@ -53,7 +56,9 @@ class PropertyEditorDock(QScrollArea):
         self._layout.setContentsMargins(8, 8, 8, 8)
         self.setWidget(self._inner)
         self._project: Project | None = None
-        self.on_apply_mass: Callable[[int, tuple[float, float, float, float, float, float]], None] | None = None
+        self.on_apply_mass: (
+            Callable[[int, tuple[float, float, float, float, float, float]], None] | None
+        ) = None
         # Element callbacks — all optional; wired by MainWindow.
         self.on_change_element_type: Callable[[int, str], None] | None = None
         self.on_change_element_material: Callable[[int, int], None] | None = None
@@ -121,9 +126,12 @@ class PropertyEditorDock(QScrollArea):
         self._layout.addWidget(QLabel(f"<h3>Node #{node.id}</h3>"))
         form = QFormLayout()
         form.addRow("Name:", QLabel(node.name or "—"))
-        form.addRow("X, Y, Z:", QLabel(
+        form.addRow(
-            f"{node.coords[0]:.4f}, {node.coords[1]:.4f}, {node.coords[2]:.4f}",
+            "X, Y, Z:",
-        ))
+            QLabel(
+                f"{node.coords[0]:.4f}, {node.coords[1]:.4f}, {node.coords[2]:.4f}",
+            ),
+        )
         form.addRow("Restraint:", QLabel(self._fmt_restraint(node.restraint)))
         self._layout.addLayout(form)
 
@@ -179,6 +187,7 @@ class PropertyEditorDock(QScrollArea):
             def _on_type_changed(new_type: str, _eid: int = el.id) -> None:
                 if new_type != el.type and self.on_change_element_type is not None:
                     self.on_change_element_type(_eid, new_type)
+
             type_cb.currentTextChanged.connect(_on_type_changed)
             form.addRow("Type:", type_cb)
         else:
@@ -188,16 +197,19 @@ class PropertyEditorDock(QScrollArea):
         form.addRow("Nodes:", QLabel(", ".join(str(n) for n in el.nodes)))
 
         # ── Section picker for frame elements. ──
-        if (hasattr(el, "section_id")
+        if (
-                and self._project is not None
+            hasattr(el, "section_id")
-                and self._project.sections
+            and self._project is not None
-                and self.on_change_element_section is not None):
+            and self._project.sections
+            and self.on_change_element_section is not None
+        ):
             sec_cb = QComboBox()
             for s in self._project.sections:
                 sec_cb.addItem(
-                    f"#{s.id} {s.name or s.type}", s.id,
+                    f"#{s.id} {s.name or s.type}",
+                    s.id,
                 )
-            idx = sec_cb.findData(el.section_id)      # type: ignore[attr-defined]
+            idx = sec_cb.findData(el.section_id)  # type: ignore[attr-defined]
             if idx >= 0:
                 sec_cb.setCurrentIndex(idx)
 
@@ -205,20 +217,23 @@ class PropertyEditorDock(QScrollArea):
                 sid = sec_cb.currentData()
                 if sid is not None and self.on_change_element_section is not None:
                     self.on_change_element_section(_eid, int(sid))
+
             sec_cb.currentIndexChanged.connect(_on_section_changed)
             form.addRow("Section:", sec_cb)
         elif hasattr(el, "section_id"):
             form.addRow("Section id:", QLabel(str(el.section_id)))
 
         # ── Material picker for truss / uniaxial-material elements. ──
-        if (hasattr(el, "material_id")
+        if (
-                and self._project is not None
+            hasattr(el, "material_id")
-                and self._project.materials
+            and self._project is not None
-                and self.on_change_element_material is not None):
+            and self._project.materials
+            and self.on_change_element_material is not None
+        ):
             mat_cb = QComboBox()
             for m in self._project.materials:
                 mat_cb.addItem(f"#{m.id} {m.name or m.type}", m.id)
-            idx = mat_cb.findData(el.material_id)     # type: ignore[attr-defined]
+            idx = mat_cb.findData(el.material_id)  # type: ignore[attr-defined]
             if idx >= 0:
                 mat_cb.setCurrentIndex(idx)
 
@@ -226,6 +241,7 @@ class PropertyEditorDock(QScrollArea):
                 mid = mat_cb.currentData()
                 if mid is not None and self.on_change_element_material is not None:
                     self.on_change_element_material(_eid, int(mid))
+
             mat_cb.currentIndexChanged.connect(_on_material_changed)
             form.addRow("Material:", mat_cb)
         elif hasattr(el, "material_id"):
@@ -236,9 +252,12 @@ class PropertyEditorDock(QScrollArea):
             area_spin = QDoubleSpinBox()
             area_spin.setRange(1e-12, 1e6)
             area_spin.setDecimals(8)
-            area_spin.setValue(float(el.area))                 # type: ignore[attr-defined]
+            area_spin.setValue(float(el.area))  # type: ignore[attr-defined]
-            area_spin.setSingleStep(float(el.area) * 0.1       # type: ignore[attr-defined]
+            area_spin.setSingleStep(
-                                    if el.area else 0.001)      # type: ignore[attr-defined]
+                float(el.area) * 0.1  # type: ignore[attr-defined]
+                if el.area
+                else 0.001
+            )  # type: ignore[attr-defined]
 
             # Commit on editingFinished so we don't dispatch a command on
             # every keystroke (which would spam the undo stack).
@@ -255,6 +274,7 @@ class PropertyEditorDock(QScrollArea):
                     return
                 if self.on_change_element_fields is not None:
                     self.on_change_element_fields(_eid, {"area": new_val})
+
             area_spin.editingFinished.connect(_on_area_edited)
             form.addRow("Area:", area_spin)
         elif hasattr(el, "area"):
@@ -268,13 +288,17 @@ class PropertyEditorDock(QScrollArea):
     def _show_multi(self, node_ids: frozenset[int], element_ids: frozenset[int]) -> None:
         self._layout.addWidget(QLabel("<h3>Multi-selection</h3>"))
         if node_ids:
-            self._layout.addWidget(QLabel(
+            self._layout.addWidget(
-                f"<b>{len(node_ids)}</b> node(s) selected: {self._fmt_id_list(node_ids)}",
+                QLabel(
-            ))
+                    f"<b>{len(node_ids)}</b> node(s) selected: {self._fmt_id_list(node_ids)}",
+                )
+            )
         if element_ids:
-            self._layout.addWidget(QLabel(
+            self._layout.addWidget(
-                f"<b>{len(element_ids)}</b> element(s) selected: {self._fmt_id_list(element_ids)}",
+                QLabel(
-            ))
+                    f"<b>{len(element_ids)}</b> element(s) selected: {self._fmt_id_list(element_ids)}",
+                )
+            )
         self._layout.addStretch(1)
 
     @staticmethod
@@ -288,4 +312,6 @@ class PropertyEditorDock(QScrollArea):
         sorted_ids = sorted(ids)
         if len(sorted_ids) <= limit:
             return ", ".join(str(i) for i in sorted_ids)
-        return ", ".join(str(i) for i in sorted_ids[:limit]) + f", … (+{len(sorted_ids) - limit} more)"
+        return (
+            ", ".join(str(i) for i in sorted_ids[:limit]) + f", … (+{len(sorted_ids) - limit} more)"
+        )

src/otko/views/docks/response_spectrum.py

@@ -36,7 +36,8 @@ class ResponseSpectrumView(QWidget):
         self._build_ui()
 
     def set_results(
-        self, results: ResponseSpectrumResults | None,
+        self,
+        results: ResponseSpectrumResults | None,
         spectrum: ResponseSpectrum | None,
     ) -> None:
         self._plot.clear()
@@ -59,9 +60,13 @@ class ResponseSpectrumView(QWidget):
             self._plot.plot(p_dense, a_dense, pen=pen, name="Sa(T)")
             # Original control points.
             self._plot.plot(
-                list(spectrum.periods), list(spectrum.accelerations),
+                list(spectrum.periods),
-                pen=None, symbol="s", symbolSize=7,
+                list(spectrum.accelerations),
-                symbolBrush="#1f77b4", symbolPen=None,
+                pen=None,
+                symbol="s",
+                symbolSize=7,
+                symbolBrush="#1f77b4",
+                symbolPen=None,
                 name="Control pts",
             )
 
@@ -77,14 +82,19 @@ class ResponseSpectrumView(QWidget):
                 # Slight vertical jitter for duplicate periods
                 y_offset = count * m.sa_at_period * 0.04
                 self._plot.plot(
-                    [m.period], [m.sa_at_period + y_offset],
+                    [m.period],
-                    pen=None, symbol="o", symbolSize=12,
+                    [m.sa_at_period + y_offset],
-                    symbolBrush="#d62728", symbolPen=pg.mkPen("#ffffff", width=1),
+                    pen=None,
+                    symbol="o",
+                    symbolSize=12,
+                    symbolBrush="#d62728",
+                    symbolPen=pg.mkPen("#ffffff", width=1),
                     name=f"Mode {m.mode_number}" if count == 0 else None,
                 )
                 # Small text label right next to the marker.
                 txt = pg.TextItem(
-                    f"  M{m.mode_number}", color="#d62728",
+                    f"  M{m.mode_number}",
+                    color="#d62728",
                     anchor=(0.0, 0.5),
                 )
                 txt.setPos(m.period, m.sa_at_period + y_offset)
@@ -133,9 +143,17 @@ class ResponseSpectrumView(QWidget):
         splitter.addWidget(self._plot)
 
         self._table = QTableWidget(0, 7)
-        self._table.setHorizontalHeaderLabels([
+        self._table.setHorizontalHeaderLabels(
-            "Mode", "T (s)", "f (Hz)", "Γ", "M_eff", "Mass %", "Sa(T)",
+            [
-        ])
+                "Mode",
+                "T (s)",
+                "f (Hz)",
+                "Γ",
+                "M_eff",
+                "Mass %",
+                "Sa(T)",
+            ]
+        )
         self._table.horizontalHeader().setSectionResizeMode(
             QHeaderView.ResizeMode.Stretch,
         )

src/otko/views/docks/results_panel.py

@@ -20,6 +20,7 @@ from PySide6.QtWidgets import (
     QWidget,
 )
 
+from otko.services.combinations import EnvelopeResults
 from otko.services.results import (
     ModalResults,
     StaticResults,
@@ -59,7 +60,18 @@ class ResultsPanel(QWidget):
         """
         self._ndm, self._ndf = ndm, ndf
         self._tabs.clear()
-        if isinstance(results, StaticResults):
+        if isinstance(results, EnvelopeResults):
+            self._title.setText(
+                f"<b>Combination (Envelope) — #{results.case_id} "
+                f"'{results.case_name}'</b>  ({results.n_steps} step(s))"
+            )
+            self._tabs.addTab(
+                self._build_envelope_table(results, "disp"), "Displacements (max/min)"
+            )
+            self._tabs.addTab(
+                self._build_envelope_table(results, "reaction"), "Reactions (max/min)"
+            )
+        elif isinstance(results, StaticResults):
             self._title.setText(
                 f"<b>Static — case #{results.case_id} '{results.case_name}'</b>  "
                 f"({results.n_steps} step(s))"
@@ -67,9 +79,7 @@ class ResultsPanel(QWidget):
             self._tabs.addTab(self._build_static_disp_table(results), "Displacements")
             self._tabs.addTab(self._build_static_reaction_table(results), "Reactions")
         elif isinstance(results, ModalResults):
-            self._title.setText(
+            self._title.setText(f"<b>Modal — case #{results.case_id} '{results.case_name}'</b>")
-                f"<b>Modal — case #{results.case_id} '{results.case_name}'</b>"
-            )
             self._tabs.addTab(self._build_modal_table(results), "Frequencies")
         elif isinstance(results, TransientResults):
             self._title.setText(
@@ -109,6 +119,28 @@ class ResultsPanel(QWidget):
                 self._set_cell(table, i, j + 1, f"{val:.6g}")
         return self._wrap(table, "Final-step reactions")
 
+    def _build_envelope_table(self, r: EnvelopeResults, kind: str) -> QWidget:
+        """Max/min table for envelope ``kind`` (``"disp"`` or ``"reaction"``)."""
+        max_map = r.node_disp_max if kind == "disp" else r.node_reaction_max
+        min_map = r.node_disp_min if kind == "disp" else r.node_reaction_min
+        rows = sorted(max_map.keys())
+        if not rows:
+            return self._empty_table_widget()
+        ndf = max_map[rows[0]].shape[1]
+        dofs = dof_labels(ndf, self._ndm, self._ndf, kind="disp" if kind == "disp" else "force")
+        headers = ["Node", *[f"{d} max" for d in dofs], *[f"{d} min" for d in dofs]]
+        table = self._make_table(headers, len(rows))
+        for i, nid in enumerate(rows):
+            self._set_cell(table, i, 0, str(nid))
+            for j, val in enumerate(max_map[nid][-1]):
+                self._set_cell(table, i, j + 1, f"{val:.6g}")
+            for j, val in enumerate(min_map[nid][-1]):
+                self._set_cell(table, i, j + 1 + ndf, f"{val:.6g}")
+        caption = (
+            "Final-step displacement envelope" if kind == "disp" else "Final-step reaction envelope"
+        )
+        return self._wrap(table, caption)
+
     def _build_modal_table(self, r: ModalResults) -> QWidget:
         n = len(r.eigenvalues)
         headers = ["Mode", "Eigenvalue (rad²/s²)", "ω (rad/s)", "f (Hz)", "T (s)"]
@@ -124,15 +156,17 @@ class ResultsPanel(QWidget):
     def _transient_summary(self, r: TransientResults) -> QWidget:
         w = QWidget()
         layout = QVBoxLayout(w)
-        layout.addWidget(QLabel(
+        layout.addWidget(
-            f"<b>Steps:</b> {r.n_steps}<br>"
+            QLabel(
-            f"<b>dt:</b> {r.dt:g}<br>"
+                f"<b>Steps:</b> {r.n_steps}<br>"
-            f"<b>Total time:</b> {r.n_steps * r.dt:g}<br>"
+                f"<b>dt:</b> {r.dt:g}<br>"
-            f"<b>HDF5 file:</b> <code>{r.h5_path}</code>"
+                f"<b>Total time:</b> {r.n_steps * r.dt:g}<br>"
-        ))
+                f"<b>HDF5 file:</b> <code>{r.h5_path}</code>"
-        layout.addWidget(QLabel(
+            )
-            "<i>Time-history plots and animation will appear here in Phase 7.</i>"
+        )
-        ))
+        layout.addWidget(
+            QLabel("<i>Time-history plots and animation will appear here in Phase 7.</i>")
+        )
         layout.addStretch(1)
         return w
 

src/otko/views/docks/table_dock.py

@@ -35,6 +35,7 @@ from PySide6.QtWidgets import (
 
 from otko.commands import (
     AddAnalysisCasesCommand,
+    AddCombinationsCommand,
     AddElementLoadsCommand,
     AddElementsCommand,
     AddEqualDOFConstraintCommand,
@@ -47,6 +48,7 @@ from otko.commands import (
     AssignMaterialCommand,
     AssignSectionCommand,
     DeleteAnalysisCasesCommand,
+    DeleteCombinationsCommand,
     DeleteElementLoadsCommand,
     DeleteElementsCommand,
     DeleteEqualDOFConstraintCommand,
@@ -59,6 +61,7 @@ from otko.commands import (
     SetMassCommand,
     SetRestraintCommand,
     UpdateAnalysisCaseCommand,
+    UpdateCombinationCommand,
     UpdateElementFieldsCommand,
     UpdateElementLoadCommand,
     UpdateEqualDOFConstraintCommand,
@@ -75,6 +78,8 @@ from otko.core import (
     ElasticUniaxial,
     EqualDOFConstraint,
     LinearTimeSeries,
+    LoadCombination,
+    LoadCombinationItem,
     NodalLoad,
     Node,
     PlainLoadPattern,
@@ -169,6 +174,7 @@ _ANALYSIS_ATTRS = [
     "tolerance",
     "max_iter",
 ]
+_COMBO_HEADERS = ["id", "name", "kind", "cases", "factors"]
 
 _TAB_ORDER = (
     "Nodes",
@@ -181,6 +187,7 @@ _TAB_ORDER = (
     "Element Loads",
     "Constraints",
     "Analyses",
+    "Combinations",
 )
 
 
@@ -270,6 +277,7 @@ class TableDock(QWidget):
             "Element Loads": self._load_element_loads,
             "Constraints": self._load_constraints,
             "Analyses": self._load_analyses,
+            "Combinations": self._load_combinations,
         }
         for name in _TAB_ORDER:
             page = QWidget()
@@ -417,6 +425,7 @@ class TableDock(QWidget):
                 "Element Loads": self._commit_element_load,
                 "Constraints": self._commit_constraint,
                 "Analyses": self._commit_analysis,
+                "Combinations": self._commit_combination,
             }[tab]
             handler(self._tables[tab], item)
         except (ValueError, KeyError, IndexError) as exc:
@@ -1095,6 +1104,49 @@ class TableDock(QWidget):
         updated = self._dry_run(case, {attr: value})
         self._dispatch(UpdateAnalysisCaseCommand(vm, updated))
 
+    # ── Combinations ───────────────────────────────────────────────
+    def _load_combinations(self, table: QTableWidget) -> None:
+        combos = list(self._project.combinations) if self._project is not None else []
+        table.setColumnCount(len(_COMBO_HEADERS))
+        table.setHorizontalHeaderLabels(_COMBO_HEADERS)
+        table.setRowCount(len(combos))
+        for r, combo in enumerate(combos):
+            self._put(table, r, 0, str(combo.id), editable=False, data=combo.id)
+            self._put(table, r, 1, combo.name, data=combo.id)
+            self._put(table, r, 2, combo.kind, data=combo.id)
+            self._put(
+                table,
+                r,
+                3,
+                ", ".join(str(i.case_id) for i in combo.items),
+                editable=False,
+                data=combo.id,
+            )
+            self._put(
+                table,
+                r,
+                4,
+                ", ".join(f"{i.factor:g}" for i in combo.items),
+                editable=False,
+                data=combo.id,
+            )
+
+    def _commit_combination(self, table: QTableWidget, item: QTableWidgetItem) -> None:
+        vm, project = self._bound()
+        row, col = item.row(), item.column()
+        cid = self._row_key(table, row)
+        combo = next(c for c in project.combinations if c.id == cid)
+        if col == 1:
+            updated = self._dry_run(combo, {"name": item.text()})
+        elif col == 2:
+            raw = item.text().strip()
+            if raw not in ("Linear", "Envelope"):
+                raise ValueError("kind: expected 'Linear' or 'Envelope'.")
+            updated = self._dry_run(combo, {"kind": raw})
+        else:
+            return
+        self._dispatch(UpdateCombinationCommand(vm, updated))
+
     # ── Add / Delete rows ──────────────────────────────────────────
     def _require_project(self, tab: str) -> Any | None:
         if self._vm is None or self._project is None:
@@ -1192,6 +1244,16 @@ class TableDock(QWidget):
                     pattern_ids=[project.load_patterns[0].id],
                 )
                 self._dispatch(AddAnalysisCasesCommand(vm, [case]))
+            elif tab == "Combinations":
+                if not project.analyses:
+                    self._say("Combinations: define an analysis case first.")
+                    return
+                combo = LoadCombination(
+                    id=project.next_combination_id(),
+                    name="New",
+                    items=[LoadCombinationItem(case_id=project.analyses[0].id)],
+                )
+                self._dispatch(AddCombinationsCommand(vm, [combo]))
         except Exception as exc:
             label = tab[:-1] if tab.endswith("s") else tab
             self._say(f"Add {label} failed: {exc}")
@@ -1264,6 +1326,8 @@ class TableDock(QWidget):
                 self._dispatch(DeleteLoadPatternCommand(vm, ids))
             elif tab == "Analyses":
                 self._dispatch(DeleteAnalysisCasesCommand(vm, ids))
+            elif tab == "Combinations":
+                self._dispatch(DeleteCombinationsCommand(vm, ids))
         except Exception as exc:
             self._say(f"Delete {tab} failed: {exc}")
             self.refresh()

src/otko/views/main_window.py

@@ -15,8 +15,9 @@ from __future__ import annotations
 
 from pathlib import Path
 
-from PySide6.QtGui import QIcon
+from PySide6.QtCore import QSettings
-from PySide6.QtWidgets import QMainWindow
+from PySide6.QtGui import QCloseEvent, QIcon
+from PySide6.QtWidgets import QMainWindow, QMessageBox
 
 from otko.viewmodels import AnalysisRunner, ProjectViewModel
 from otko.views.action_handlers import ActionHandlers
@@ -74,6 +75,7 @@ class MainWindow(
         self._build_status_bar()
         self._wire()
         self._refresh_action_enablement()
+        self.restore_layout()
 
     # ── construction ─────────────────────────────────────────────────
     def _build_central_canvas(self) -> None:
@@ -82,6 +84,54 @@ class MainWindow(
         # Diagram overlay paints onto the same plotter as the model.
         self._diagram_renderer = DiagramRenderer(self._canvas)
 
+    # ── layout persistence ───────────────────────────────────────────
+    def save_layout(self) -> None:
+        """Persist window geometry and dock/toolbar state for next launch."""
+        settings = QSettings("OTKO", "OTKO")
+        settings.setValue("geometry", self.saveGeometry())
+        settings.setValue("windowState", self.saveState())
+
+    def restore_layout(self) -> None:
+        """Restore a previously saved geometry/dock layout, if any.
+
+        On first run no values are stored, so the defaults from ``__init__``
+        (``resize`` + dock construction) stay in effect.
+        """
+        settings = QSettings("OTKO", "OTKO")
+        geometry = settings.value("geometry")
+        if geometry is not None:
+            self.restoreGeometry(geometry)
+        state = settings.value("windowState")
+        if state is not None:
+            self.restoreState(state)
+
+    def closeEvent(self, event: QCloseEvent) -> None:  # noqa: N802 (Qt override)
+        """Prompt to save unsaved work, then persist the window layout.
+
+        The prompt is shown only for a visible window: Qt also closes hidden
+        widgets during teardown (for example under ``pytest-qt``), where a
+        modal dialog would block with no user to answer it.
+        """
+        if self._vm.is_dirty and self.isVisible():
+            buttons = QMessageBox.StandardButton
+            choice = QMessageBox.warning(
+                self,
+                "Unsaved changes",
+                "Save changes to the current project before closing?",
+                buttons.Save | buttons.Discard | buttons.Cancel,
+                buttons.Save,
+            )
+            if choice == buttons.Cancel:
+                event.ignore()
+                return
+            if choice == buttons.Save:
+                self._on_save()
+                if self._vm.is_dirty:
+                    event.ignore()
+                    return
+        self.save_layout()
+        event.accept()
+
     # ── wiring ────────────────────────────────────────────────────────
     def _wire(self) -> None:
         # File
@@ -141,6 +191,7 @@ class MainWindow(
 
         # Analyze
         self._act_case_manager.triggered.connect(self._on_case_manager)
+        self._act_combo_manager.triggered.connect(self._on_combo_manager)
         self._act_run.triggered.connect(self._on_run_analysis)
 
         # Display
@@ -156,7 +207,7 @@ class MainWindow(
         self._act_back_to_model.triggered.connect(self._on_back_to_model)
 
         # AnalysisRunner: stream log to console + show results in panel
-        self._runner.log.connect(self._console.appendPlainText)
+        self._runner.log.connect(self._console_dock.log)
         self._runner.finished.connect(self._on_analysis_finished)
         self._runner.failed.connect(self._on_analysis_failed)
 

src/otko/views/menu_builder.py

@@ -155,6 +155,7 @@ class MenuBuilder:
 
         # Analyze
         self._act_case_manager = QAction("&Cases…", self, shortcut="Ctrl+Shift+A")
+        self._act_combo_manager = QAction("&Load Combinations…", self)
         self._act_run = QAction("&Run…", self, shortcut="F5")
 
         # View (Iso/Top/Front/Right are an exclusive checkable group so the
@@ -285,6 +286,11 @@ class MenuBuilder:
                 "Analysis Cases (Ctrl+Shift+A)",
                 "Manage analysis cases.",
             ),
+            "_act_combo_manager": (
+                "cases",
+                "Load Combinations",
+                "Manage named case-result load combinations.",
+            ),
             "_act_show_deformed": (
                 "show-deformed",
                 "Show Deformed Shape",
@@ -420,6 +426,7 @@ class MenuBuilder:
 
         m_analyze = mb.addMenu("&Analyze")
         m_analyze.addAction(self._act_case_manager)
+        m_analyze.addAction(self._act_combo_manager)
         m_analyze.addSeparator()
         m_analyze.addAction(self._act_run)
 
@@ -482,7 +489,7 @@ class MenuBuilder:
         tb.setMovable(True)
         tb.setIconSize(QSize(24, 24))
         tb.setToolButtonStyle(Qt.ToolButtonStyle.ToolButtonIconOnly)
-        # Top edge; Tools stays in the left area independently (built next).
+        # Top edge; Tools shares the top area (built next).
         self.addToolBar(Qt.ToolBarArea.TopToolBarArea, tb)
         self._view_toolbar = tb
         tb.addAction(self._act_zoom_extents)
@@ -528,9 +535,8 @@ class MenuBuilder:
         tb.setMovable(True)
         tb.setIconSize(QSize(24, 24))
         tb.setToolButtonStyle(Qt.ToolButtonStyle.ToolButtonIconOnly)
-        # View lives on the top edge, so Tools stays left independently
+        # Top edge alongside the View toolbar (built just before).
-        # in its own left-area column.
+        self.addToolBar(Qt.ToolBarArea.TopToolBarArea, tb)
-        self.addToolBar(Qt.ToolBarArea.LeftToolBarArea, tb)
         self._tools_toolbar = tb
         tb.addAction(self._act_tool_select)
         tb.addAction(self._act_tool_draw_node)

src/otko/views/render_controls.py

@@ -496,5 +496,5 @@ class RenderControls:
         self._act_clear_display.setEnabled(has_project)
 
     def _log(self, message: str) -> None:
-        self._console.appendPlainText(message)
+        self._console_dock.log(message)
         self.statusBar().showMessage(message, 5000)

src/otko/views/tools/__init__.py

@@ -5,5 +5,11 @@ from otko.views.tools.draw_frame import DrawFrameTool
 from otko.views.tools.draw_node import DrawNodeTool
 from otko.views.tools.draw_truss import DrawTrussTool
 
-__all__ = ["CanvasTool", "SelectTool", "ToolController",
+__all__ = [
-           "DrawFrameTool", "DrawNodeTool", "DrawTrussTool"]
+    "CanvasTool",
+    "SelectTool",
+    "ToolController",
+    "DrawFrameTool",
+    "DrawNodeTool",
+    "DrawTrussTool",
+]

src/otko/views/tools/base.py

@@ -84,10 +84,11 @@ class SelectTool(CanvasTool):
 class ToolController(QObject):
     """Owns the active tool and routes canvas pick signals to it."""
 
-    toolChanged = Signal(object)   # emits the new CanvasTool (or None for default)
+    toolChanged = Signal(object)  # emits the new CanvasTool (or None for default)
 
-    def __init__(self, canvas: "ModelCanvas", vm: "ProjectViewModel",
+    def __init__(
-                 parent: QObject | None = None) -> None:
+        self, canvas: "ModelCanvas", vm: "ProjectViewModel", parent: QObject | None = None
+    ) -> None:
         super().__init__(parent)
         self._canvas = canvas
         self._vm = vm

src/otko/views/tools/draw_frame.py

@@ -67,7 +67,9 @@ class DrawFrameTool(LinearElementDrawTool):
             section_id = self._ensure_default_section()
             element_id = project.next_element_id()
             elem = ElasticBeamColumn(
-                id=element_id, nodes=(n1, n2), section_id=section_id,
+                id=element_id,
+                nodes=(n1, n2),
+                section_id=section_id,
             )
             self._vm.apply_command(AddElementsCommand(self._vm, [elem]))
         finally:

src/otko/views/tools/draw_node.py

@@ -27,14 +27,20 @@ if TYPE_CHECKING:
 
 
 def _snap_to_grid(
-    x: float, y: float, z: float,
+    x: float,
-    x_lines: list[float], y_lines: list[float], z_lines: list[float],
+    y: float,
+    z: float,
+    x_lines: list[float],
+    y_lines: list[float],
+    z_lines: list[float],
 ) -> tuple[float, float, float]:
     """Snap each coordinate to its closest grid line (identity on empty axes)."""
+
     def nearest(v: float, lines: list[float]) -> float:
         if not lines:
             return v
         return min(lines, key=lambda c: abs(c - v))
+
     return nearest(x, x_lines), nearest(y, y_lines), nearest(z, z_lines)
 
 
@@ -70,16 +76,17 @@ def _snap_with_distance(
         if not (grid.x_lines or grid.y_lines or grid.z_lines):
             continue
         lx, ly, lz = cs.coord.world_to_local(world)
-        sl = _snap_to_grid(lx, ly, lz,
+        sl = _snap_to_grid(lx, ly, lz, grid.x_lines, grid.y_lines, grid.z_lines)
-                            grid.x_lines, grid.y_lines, grid.z_lines)
         candidate = cs.coord.local_to_world(sl)
-        d2 = ((candidate[0] - world[0]) ** 2
+        d2 = (
-              + (candidate[1] - world[1]) ** 2
+            (candidate[0] - world[0]) ** 2
-              + (candidate[2] - world[2]) ** 2)
+            + (candidate[1] - world[1]) ** 2
+            + (candidate[2] - world[2]) ** 2
+        )
         if d2 < best_d2:
             best = candidate
             best_d2 = d2
-    return best, (best_d2 ** 0.5) if best is not None else float("inf")
+    return best, (best_d2**0.5) if best is not None else float("inf")
 
 
 def _min_grid_spacing(systems: list[CoordinateGridSystem]) -> float | None:
@@ -124,13 +131,13 @@ class DrawNodeTool(CanvasTool):
         super().deactivate()
 
     def prompt(self) -> str:
-        return ("Draw Node: click a grid intersection "
+        return (
-                "to place a node. Switch to Select tool to finish.")
+            "Draw Node: click a grid intersection "
+            "to place a node. Switch to Select tool to finish."
+        )
 
     def on_node_picked(self, node_id: int) -> None:
-        self.statusChanged.emit(
+        self.statusChanged.emit(f"Draw Node: node {node_id} already exists at that spot.")
-            f"Draw Node: node {node_id} already exists at that spot."
-        )
 
     def on_empty_clicked(self, x: float, y: float, z: float) -> None:
         """Called only when the canvas has already confirmed a grid snap.
@@ -153,9 +160,5 @@ class DrawNodeTool(CanvasTool):
 
         nid = project.next_node_id()
         node = Node(id=nid, coords=(x, y, z))
-        self._vm.apply_command(
+        self._vm.apply_command(AddNodesCommand(self._vm, [node], text=f"Add node {nid}"))
-            AddNodesCommand(self._vm, [node], text=f"Add node {nid}")
+        self.statusChanged.emit(f"Draw Node: added node {nid} at ({x:g}, {y:g}, {z:g}).")
-        )
-        self.statusChanged.emit(
-            f"Draw Node: added node {nid} at ({x:g}, {y:g}, {z:g})."
-        )

tests/conftest.py

@@ -1,22 +1,30 @@
-"""Shared pytest fixtures.
+"""Shared pytest configuration.
 
-`pytest-qt` automatically provides a `qtbot` fixture and a QApplication
+The GUI suite is headless by default: unless the caller already chose a
-instance. We add convenience fixtures here as the suite grows.
+platform, ``QT_QPA_PLATFORM=offscreen`` is set here, before pytest-qt
+builds its session ``QApplication``. An explicit caller value is respected.
+
+OpenseesPy is a process-global singleton, so a lazy autouse guard wipes the
+domain after every test. The import is inside the teardown so that
+``tests/unit`` never imports the solver.
 """
 
 from __future__ import annotations
 
+import os
+from collections.abc import Iterator
+
 import pytest
 
+os.environ.setdefault("QT_QPA_PLATFORM", "offscreen")
+
 
 @pytest.fixture(autouse=True)
-def _isolate_opensees() -> None:
+def _wipe_opensees_domain() -> Iterator[None]:
-    """Reset OpenSees domain between tests if openseespy is importable.
+    """Wipe the OpenseesPy domain after a test if the solver was imported."""
-
+    yield
-    Imported lazily so that pure-core tests don't pull in the C++ runtime.
-    """
     try:
-        import openseespy.opensees as ops
+        from openseespy.opensees import wipe
-    except ImportError:
+    except Exception:  # pragma: no cover - solver not installed / import side effects
         return
-    ops.wipe()
+    wipe()

tests/gui/test_analysis_commands.py

@@ -29,8 +29,9 @@ def _vm_with_pattern() -> ProjectViewModel:
     vm.project.nodes.append(Node(id=1, coords=(0, 0, 0)))
     vm.project.time_series.append(LinearTimeSeries(id=1))
     vm.project.load_patterns.append(
-        PlainLoadPattern(id=1, time_series_id=1,
+        PlainLoadPattern(
-                         nodal_loads=[NodalLoad(node_id=1, forces=(100, 0, 0, 0, 0, 0))])
+            id=1, time_series_id=1, nodal_loads=[NodalLoad(node_id=1, forces=(100, 0, 0, 0, 0, 0))]
+        )
     )
     return vm
 
@@ -57,9 +58,14 @@ def test_add_modal_case_no_pattern_needed(qtbot) -> None:  # type: ignore[no-unt
 def test_add_emits_modelMutated(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_with_pattern()
     with qtbot.waitSignal(vm.modelMutated, timeout=500):
-        vm.apply_command(AddAnalysisCasesCommand(vm, [
+        vm.apply_command(
-            StaticCase(id=1, pattern_ids=[1]),
+            AddAnalysisCasesCommand(
-        ]))
+                vm,
+                [
+                    StaticCase(id=1, pattern_ids=[1]),
+                ],
+            )
+        )
 
 
 @pytest.mark.gui
@@ -74,9 +80,14 @@ def test_add_duplicate_id_raises(qtbot) -> None:  # type: ignore[no-untyped-def]
 @pytest.mark.gui
 def test_update_static_changes_n_steps(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_with_pattern()
-    vm.apply_command(AddAnalysisCasesCommand(vm, [
+    vm.apply_command(
-        StaticCase(id=1, name="A", pattern_ids=[1], n_steps=1),
+        AddAnalysisCasesCommand(
-    ]))
+            vm,
+            [
+                StaticCase(id=1, name="A", pattern_ids=[1], n_steps=1),
+            ],
+        )
+    )
     new = StaticCase(id=1, name="A", pattern_ids=[1], n_steps=10)
     vm.apply_command(UpdateAnalysisCaseCommand(vm, new))
     assert vm.project.analyses[0].n_steps == 10
@@ -87,9 +98,14 @@ def test_update_static_changes_n_steps(qtbot) -> None:  # type: ignore[no-untype
 @pytest.mark.gui
 def test_update_changes_case_type(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_with_pattern()
-    vm.apply_command(AddAnalysisCasesCommand(vm, [
+    vm.apply_command(
-        StaticCase(id=1, pattern_ids=[1]),
+        AddAnalysisCasesCommand(
-    ]))
+            vm,
+            [
+                StaticCase(id=1, pattern_ids=[1]),
+            ],
+        )
+    )
     swapped = ModalCase(id=1, name="Mode swap", n_modes=5)
     vm.apply_command(UpdateAnalysisCaseCommand(vm, swapped))
     assert isinstance(vm.project.analyses[0], ModalCase)
@@ -109,10 +125,15 @@ def test_update_unknown_id_raises(qtbot) -> None:  # type: ignore[no-untyped-def
 @pytest.mark.gui
 def test_delete_round_trip(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_with_pattern()
-    vm.apply_command(AddAnalysisCasesCommand(vm, [
+    vm.apply_command(
-        StaticCase(id=1, pattern_ids=[1]),
+        AddAnalysisCasesCommand(
-        ModalCase(id=2),
+            vm,
-    ]))
+            [
+                StaticCase(id=1, pattern_ids=[1]),
+                ModalCase(id=2),
+            ],
+        )
+    )
     vm.apply_command(DeleteAnalysisCasesCommand(vm, {1}))
     assert {c.id for c in vm.project.analyses} == {2}
     vm.undo_stack.undo()

tests/gui/test_analysis_runner.py

@@ -35,21 +35,42 @@ def cantilever_vm() -> ProjectViewModel:
     L = 5.0
     vm = ProjectViewModel()
     vm.new_project(ndm=2, ndf=3)
-    vm.apply_command(AddNodesCommand(vm, [
+    vm.apply_command(
-        Node(id=1, coords=(0.0, 0.0, 0.0),
+        AddNodesCommand(
-             restraint=(True, True, False, False, False, True)),
+            vm,
-        Node(id=2, coords=(L, 0.0, 0.0)),
+            [
-    ]))
+                Node(
-    vm.apply_command(AddSectionsCommand(vm, [
+                    id=1, coords=(0.0, 0.0, 0.0), restraint=(True, True, False, False, False, True)
-        ElasticSection(id=1, E=200e9, A=0.01, Iz=8.333e-6),
+                ),
-    ]))
+                Node(id=2, coords=(L, 0.0, 0.0)),
-    vm.apply_command(AddElementsCommand(vm, [
+            ],
-        ElasticBeamColumn(id=1, nodes=(1, 2), section_id=1),
+        )
-    ]))
+    )
+    vm.apply_command(
+        AddSectionsCommand(
+            vm,
+            [
+                ElasticSection(id=1, E=200e9, A=0.01, Iz=8.333e-6),
+            ],
+        )
+    )
+    vm.apply_command(
+        AddElementsCommand(
+            vm,
+            [
+                ElasticBeamColumn(id=1, nodes=(1, 2), section_id=1),
+            ],
+        )
+    )
     vm.apply_command(AddNodalLoadsCommand(vm, {2}, (0.0, -1000.0, 0.0, 0.0, 0.0, 0.0)))
-    vm.apply_command(AddAnalysisCasesCommand(vm, [
+    vm.apply_command(
-        StaticCase(id=1, name="Cantilever", pattern_ids=[1]),
+        AddAnalysisCasesCommand(
-    ]))
+            vm,
+            [
+                StaticCase(id=1, name="Cantilever", pattern_ids=[1]),
+            ],
+        )
+    )
     return vm
 
 

tests/gui/test_assign_load_pattern_name.py

@@ -48,10 +48,11 @@ def test_dialog_lists_existing_patterns(qtbot) -> None:  # type: ignore[no-untyp
 @pytest.mark.gui
 def test_dialog_enables_name_field_for_new_pattern(qtbot) -> None:  # type: ignore[no-untyped-def]
     dlg = AssignLoadDialog(
-        n_selected=1, existing_patterns=[(1, "Gravity")],
+        n_selected=1,
+        existing_patterns=[(1, "Gravity")],
     )
     qtbot.addWidget(dlg)
-    dlg._pattern_cb.setCurrentIndex(1)   # "<New pattern…>"
+    dlg._pattern_cb.setCurrentIndex(1)  # "<New pattern…>"
     assert dlg.selected_pattern_id() is None
     assert dlg._new_name_edit.isEnabled()
     dlg._new_name_edit.setText("RefMoment")
@@ -68,14 +69,23 @@ def test_command_creates_named_pattern(qtbot) -> None:  # type: ignore[no-untype
     # Pre-existing 'Gravity' pattern — must NOT be reused when the user
     # asks for a new one named 'RefMoment'.
     vm.project.time_series.append(LinearTimeSeries(id=1, name="Gravity"))
-    vm.project.load_patterns.append(PlainLoadPattern(
+    vm.project.load_patterns.append(
-        id=1, name="Gravity", time_series_id=1,
+        PlainLoadPattern(
-    ))
+            id=1,
+            name="Gravity",
+            time_series_id=1,
+        )
+    )
 
-    vm.apply_command(AddNodalLoadsCommand(
+    vm.apply_command(
-        vm, {1}, (0, 0, 0, 0, 0, 1.0),
+        AddNodalLoadsCommand(
-        pattern_id=None, new_pattern_name="RefMoment",
+            vm,
-    ))
+            {1},
+            (0, 0, 0, 0, 0, 1.0),
+            pattern_id=None,
+            new_pattern_name="RefMoment",
+        )
+    )
     # Two patterns now: Gravity (id=1) and RefMoment (id=2).
     names = [p.name for p in vm.project.load_patterns]
     assert "Gravity" in names and "RefMoment" in names
@@ -90,13 +100,20 @@ def test_command_creates_constant_timeseries_when_requested(qtbot) -> None:  # t
     the new pattern — required for axial preloads in moment-curvature
     runs where pseudoTime must NOT scale the axial force."""
     from otko.core import ConstantTimeSeries
+
     vm = ProjectViewModel()
     vm.new_project(ndm=2, ndf=3)
     vm.project.nodes.append(Node(id=1, coords=(0, 0, 0)))
-    vm.apply_command(AddNodalLoadsCommand(
+    vm.apply_command(
-        vm, {1}, (-180, 0, 0, 0, 0, 0),
+        AddNodalLoadsCommand(
-        pattern_id=None, new_pattern_name="AxialP", new_ts_type="Constant",
+            vm,
-    ))
+            {1},
+            (-180, 0, 0, 0, 0, 0),
+            pattern_id=None,
+            new_pattern_name="AxialP",
+            new_ts_type="Constant",
+        )
+    )
     # Pattern + TimeSeries both created with the "AxialP" name.
     assert vm.project.load_patterns[0].name == "AxialP"
     ts = vm.project.time_series[0]
@@ -111,11 +128,20 @@ def test_command_reuses_existing_pattern_by_id(qtbot) -> None:  # type: ignore[n
     vm.new_project(ndm=2, ndf=3)
     vm.project.nodes.append(Node(id=1, coords=(0, 0, 0)))
     vm.project.time_series.append(LinearTimeSeries(id=1, name="Existing"))
-    vm.project.load_patterns.append(PlainLoadPattern(
+    vm.project.load_patterns.append(
-        id=1, name="Existing", time_series_id=1,
+        PlainLoadPattern(
-    ))
+            id=1,
-    vm.apply_command(AddNodalLoadsCommand(
+            name="Existing",
-        vm, {1}, (0, 0, 0, 0, 0, 5.0), pattern_id=1,
+            time_series_id=1,
-    ))
+        )
+    )
+    vm.apply_command(
+        AddNodalLoadsCommand(
+            vm,
+            {1},
+            (0, 0, 0, 0, 0, 5.0),
+            pattern_id=1,
+        )
+    )
     assert len(vm.project.load_patterns) == 1
     assert len(vm.project.load_patterns[0].nodal_loads) == 1

tests/gui/test_assign_masses.py

@@ -23,7 +23,9 @@ def test_mass_vector_reads_spinboxes(qtbot) -> None:  # type: ignore[no-untyped-
     dlg._mx.setValue(5000.0)
     dlg._my.setValue(5000.0)
     dlg._mz.setValue(100.0)
-    dlg._mxx.setValue(0.0); dlg._myy.setValue(0.0); dlg._mzz.setValue(0.0)
+    dlg._mxx.setValue(0.0)
+    dlg._myy.setValue(0.0)
+    dlg._mzz.setValue(0.0)
     assert dlg.mass_vector() == (5000.0, 5000.0, 100.0, 0.0, 0.0, 0.0)
 
 

tests/gui/test_assign_zls.py

@@ -18,15 +18,24 @@ from otko.views.dialogs.assign_zls import (  # noqa: E402
 
 def _project_with_section() -> Project:
     return Project(
-        ndm=2, ndf=3,
+        ndm=2,
+        ndf=3,
         nodes=[
             Node(id=1, coords=(0, 0, 0)),
             Node(id=2, coords=(0, 0, 0)),
         ],
-        sections=[ElasticSection(
+        sections=[
-            id=3, name="MK", E=30000, A=200, Iz=6667, Iy=6667,
+            ElasticSection(
-            G=12000, J=100,
+                id=3,
-        )],
+                name="MK",
+                E=30000,
+                A=200,
+                Iz=6667,
+                Iy=6667,
+                G=12000,
+                J=100,
+            )
+        ],
     )
 
 
@@ -43,7 +52,8 @@ def test_dialog_lists_project_sections(qtbot) -> None:  # type: ignore[no-untype
 @pytest.mark.gui
 def test_dialog_disabled_when_no_sections(qtbot) -> None:  # type: ignore[no-untyped-def]
     p = Project(
-        ndm=2, ndf=3,
+        ndm=2,
+        ndf=3,
         nodes=[Node(id=1, coords=(0, 0, 0)), Node(id=2, coords=(0, 0, 0))],
     )
     dlg = AssignZeroLengthSectionDialog(p, (1, 2))

tests/gui/test_canvas_grid_snap.py

@@ -23,7 +23,8 @@ from otko.core import (  # noqa: E402
 
 # ────────────────────── logic helpers (no VTK) ──────────────────────
 def _nearest_snap(
-    cx: float, cy: float,
+    cx: float,
+    cy: float,
     world_pts: np.ndarray,
     screen_pts: np.ndarray,
     tol_px: float,
@@ -33,7 +34,7 @@ def _nearest_snap(
         return None
     d2 = (screen_pts[:, 0] - cx) ** 2 + (screen_pts[:, 1] - cy) ** 2
     idx = int(np.argmin(d2))
-    if d2[idx] <= tol_px ** 2:
+    if d2[idx] <= tol_px**2:
         return tuple(float(v) for v in world_pts[idx])  # type: ignore[return-value]
     return None
 
@@ -65,6 +66,7 @@ def test_grid_intersections_world_includes_all_visible_systems(qtbot) -> None:
     """ModelCanvas._grid_intersections_world combines every visible system's
     intersections (transformed by that system's origin/rotation)."""
     from otko.views.canvas3d.model_canvas import ModelCanvas
+
     canvas = ModelCanvas()
     qtbot.addWidget(canvas)
 
@@ -101,15 +103,17 @@ def test_grid_intersections_world_includes_all_visible_systems(qtbot) -> None:
 
 def test_grid_intersections_world_returns_none_without_grid(qtbot) -> None:  # type: ignore[no-untyped-def]
     from otko.views.canvas3d.model_canvas import ModelCanvas
+
     canvas = ModelCanvas()
     qtbot.addWidget(canvas)
-    canvas.show_project(Project())   # default: Global system with no grid lines
+    canvas.show_project(Project())  # default: Global system with no grid lines
     assert canvas._grid_intersections_world() is None
 
 
 def test_hide_all_suppresses_intersections(qtbot) -> None:  # type: ignore[no-untyped-def]
     """A system with ``hide_all=True`` must not contribute snap targets."""
     from otko.views.canvas3d.model_canvas import ModelCanvas
+
     canvas = ModelCanvas()
     qtbot.addWidget(canvas)
 
@@ -134,20 +138,23 @@ def test_hide_all_suppresses_intersections(qtbot) -> None:  # type: ignore[no-un
 def test_hover_snap_marker_round_trips(qtbot) -> None:  # type: ignore[no-untyped-def]
     """set_hover_snap(pt) creates an actor; passing None removes it."""
     from otko.views.canvas3d.model_canvas import ModelCanvas
+
     canvas = ModelCanvas()
     qtbot.addWidget(canvas)
-    canvas.show_project(Project(
+    canvas.show_project(
-        coord_systems=[
+        Project(
-            CoordinateGridSystem(
+            coord_systems=[
-                name="Global",
+                CoordinateGridSystem(
-                grid=GridSystem(
+                    name="Global",
-                    x_grid_lines=make_grid_lines("X", [0.0, 3.0]),
+                    grid=GridSystem(
-                    y_grid_lines=make_grid_lines("Y", [0.0, 4.0]),
+                        x_grid_lines=make_grid_lines("X", [0.0, 3.0]),
-                    z_grid_lines=make_grid_lines("Z", [0.0]),
+                        y_grid_lines=make_grid_lines("Y", [0.0, 4.0]),
+                        z_grid_lines=make_grid_lines("Z", [0.0]),
+                    ),
                 ),
-            ),
+            ],
-        ],
+        )
-    ))
+    )
     r = canvas._renderer
     assert r._hover_actor is None
     r.set_hover_snap((3.0, 0.0, 0.0))
@@ -158,20 +165,23 @@ def test_hover_snap_marker_round_trips(qtbot) -> None:  # type: ignore[no-untype
 
 def test_snap_preview_flag_clears_marker(qtbot) -> None:  # type: ignore[no-untyped-def]
     from otko.views.canvas3d.model_canvas import ModelCanvas
+
     canvas = ModelCanvas()
     qtbot.addWidget(canvas)
-    canvas.show_project(Project(
+    canvas.show_project(
-        coord_systems=[
+        Project(
-            CoordinateGridSystem(
+            coord_systems=[
-                name="Global",
+                CoordinateGridSystem(
-                grid=GridSystem(
+                    name="Global",
-                    x_grid_lines=make_grid_lines("X", [0.0]),
+                    grid=GridSystem(
-                    y_grid_lines=make_grid_lines("Y", [0.0]),
+                        x_grid_lines=make_grid_lines("X", [0.0]),
-                    z_grid_lines=make_grid_lines("Z", [0.0]),
+                        y_grid_lines=make_grid_lines("Y", [0.0]),
+                        z_grid_lines=make_grid_lines("Z", [0.0]),
+                    ),
                 ),
-            ),
+            ],
-        ],
+        )
-    ))
+    )
     canvas.set_snap_preview_enabled(True)
     canvas._renderer.set_hover_snap((0.0, 0.0, 0.0))
     assert canvas._renderer._hover_actor is not None
@@ -183,7 +193,7 @@ def test_snap_preview_flag_clears_marker(qtbot) -> None:  # type: ignore[no-unty
 def _pt_to_segment_d2(p: np.ndarray, a: np.ndarray, b: np.ndarray) -> np.ndarray:
     """Vectorised point-to-segment squared distance, used to verify logic."""
     ab = b - a
-    ab_sq = (ab ** 2).sum(axis=1)
+    ab_sq = (ab**2).sum(axis=1)
     ab_sq = np.where(ab_sq == 0, 1.0, ab_sq)
     pa = p - a
     t = (pa * ab).sum(axis=1) / ab_sq
@@ -204,21 +214,21 @@ def test_point_to_segment_midpoint_hit() -> None:
 
 def test_point_to_segment_endpoint_hit() -> None:
     """A click near an endpoint must also hit — the bug fix this test guards."""
-    p = np.array([1.0, 51.0])          # 1 px off node-a on a horizontal frame
+    p = np.array([1.0, 51.0])  # 1 px off node-a on a horizontal frame
     a = np.array([[0.0, 50.0]])
     b = np.array([[100.0, 50.0]])
     d2 = _pt_to_segment_d2(p, a, b)
-    assert d2[0] <= 2.0 ** 2           # well inside a 5-pixel test tolerance
+    assert d2[0] <= 2.0**2  # well inside a 5-pixel test tolerance
 
 
 def test_point_to_segment_orthogonal_miss() -> None:
     """Clicking far from a short frame must produce a large distance."""
     p = np.array([50.0, 200.0])
     a = np.array([[0.0, 50.0]])
-    b = np.array([[10.0, 50.0]])       # short frame at (0..10, 50)
+    b = np.array([[10.0, 50.0]])  # short frame at (0..10, 50)
     d2 = _pt_to_segment_d2(p, a, b)
     # Closest point is (10, 50), distance ≈ sqrt(40² + 150²) ≈ 155
-    assert d2[0] > 150.0 ** 2
+    assert d2[0] > 150.0**2
 
 
 def test_single_node_radius_uses_grid_extent(qtbot) -> None:  # type: ignore[no-untyped-def]
@@ -226,6 +236,7 @@ def test_single_node_radius_uses_grid_extent(qtbot) -> None:  # type: ignore[no-
     grid bounds so the node remains visible (regression guard)."""
     from otko.core import Node
     from otko.views.canvas3d.model_canvas import ModelCanvas
+
     canvas = ModelCanvas()
     qtbot.addWidget(canvas)
     p = Project(

tests/gui/test_commands.py

@@ -77,17 +77,27 @@ def test_add_nodes_duplicate_id_raises(qtbot) -> None:  # type: ignore[no-untype
 @pytest.mark.gui
 def test_delete_node_cascades_to_elements(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm()
-    vm.apply_command(AddNodesCommand(vm, [
+    vm.apply_command(
-        Node(id=1, coords=(0, 0, 0)),
+        AddNodesCommand(
-        Node(id=2, coords=(1, 0, 0)),
+            vm,
-        Node(id=3, coords=(2, 0, 0)),
+            [
-    ]))
+                Node(id=1, coords=(0, 0, 0)),
+                Node(id=2, coords=(1, 0, 0)),
+                Node(id=3, coords=(2, 0, 0)),
+            ],
+        )
+    )
     # Add a material so the element is valid.
     vm.project.materials.append(Steel01(id=1, Fy=420e6, E0=200e9, b=0.01))
-    vm.apply_command(AddElementsCommand(vm, [
+    vm.apply_command(
-        TrussElement(id=1, nodes=(1, 2), area=1e-3, material_id=1),
+        AddElementsCommand(
-        TrussElement(id=2, nodes=(2, 3), area=1e-3, material_id=1),
+            vm,
-    ]))
+            [
+                TrussElement(id=1, nodes=(1, 2), area=1e-3, material_id=1),
+                TrussElement(id=2, nodes=(2, 3), area=1e-3, material_id=1),
+            ],
+        )
+    )
     # Delete node 2 → both elements should disappear.
     vm.apply_command(DeleteNodesCommand(vm, {2}))
     assert {n.id for n in vm.project.nodes} == {1, 3}
@@ -102,10 +112,15 @@ def test_delete_node_cascades_to_elements(qtbot) -> None:  # type: ignore[no-unt
 @pytest.mark.gui
 def test_set_restraint_round_trip(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm()
-    vm.apply_command(AddNodesCommand(vm, [
+    vm.apply_command(
-        Node(id=1, coords=(0, 0, 0)),
+        AddNodesCommand(
-        Node(id=2, coords=(1, 0, 0)),
+            vm,
-    ]))
+            [
+                Node(id=1, coords=(0, 0, 0)),
+                Node(id=2, coords=(1, 0, 0)),
+            ],
+        )
+    )
     fix = (True, True, True, True, True, True)
     vm.apply_command(SetRestraintCommand(vm, {1, 2}, fix))
     assert vm.project.node(1).restraint == fix

tests/gui/test_convert_element_type.py

@@ -26,32 +26,62 @@ from otko.viewmodels import ProjectViewModel  # noqa: E402
 def _vm_setup() -> ProjectViewModel:
     vm = ProjectViewModel()
     vm.new_project()
-    vm.apply_command(AddNodesCommand(vm, [
+    vm.apply_command(
-        Node(id=1, coords=(0, 0, 0)),
+        AddNodesCommand(
-        Node(id=2, coords=(3, 0, 0)),
+            vm,
-    ]))
+            [
-    vm.apply_command(AddMaterialsCommand(vm, [
+                Node(id=1, coords=(0, 0, 0)),
-        ElasticUniaxial(id=1, name="Steel", E=200e9),
+                Node(id=2, coords=(3, 0, 0)),
-    ]))
+            ],
-    vm.apply_command(AddSectionsCommand(vm, [
+        )
-        ElasticSection(
+    )
-            id=1, name="Default", E=200e9, A=0.01,
+    vm.apply_command(
-            Iz=8.33e-6, Iy=8.33e-6, G=80e9, J=1e-6,
+        AddMaterialsCommand(
-        ),
+            vm,
-    ]))
+            [
+                ElasticUniaxial(id=1, name="Steel", E=200e9),
+            ],
+        )
+    )
+    vm.apply_command(
+        AddSectionsCommand(
+            vm,
+            [
+                ElasticSection(
+                    id=1,
+                    name="Default",
+                    E=200e9,
+                    A=0.01,
+                    Iz=8.33e-6,
+                    Iy=8.33e-6,
+                    G=80e9,
+                    J=1e-6,
+                ),
+            ],
+        )
+    )
     return vm
 
 
 @pytest.mark.gui
 def test_frame_to_truss_conversion(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_setup()
-    vm.apply_command(AddElementsCommand(vm, [
+    vm.apply_command(
-        ElasticBeamColumn(id=1, nodes=(1, 2), section_id=1),
+        AddElementsCommand(
-    ]))
+            vm,
-    vm.apply_command(ConvertElementTypeCommand(
+            [
-        vm, {1}, "Truss",
+                ElasticBeamColumn(id=1, nodes=(1, 2), section_id=1),
-        defaults={"material_id": 1, "area": 0.001},
+            ],
-    ))
+        )
+    )
+    vm.apply_command(
+        ConvertElementTypeCommand(
+            vm,
+            {1},
+            "Truss",
+            defaults={"material_id": 1, "area": 0.001},
+        )
+    )
     el = vm.project.element(1)
     assert isinstance(el, TrussElement)
     assert el.nodes == (1, 2)
@@ -62,13 +92,22 @@ def test_frame_to_truss_conversion(qtbot) -> None:  # type: ignore[no-untyped-de
 @pytest.mark.gui
 def test_truss_to_frame_conversion(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_setup()
-    vm.apply_command(AddElementsCommand(vm, [
+    vm.apply_command(
-        TrussElement(id=1, nodes=(1, 2), area=0.001, material_id=1),
+        AddElementsCommand(
-    ]))
+            vm,
-    vm.apply_command(ConvertElementTypeCommand(
+            [
-        vm, {1}, "ElasticBeamColumn",
+                TrussElement(id=1, nodes=(1, 2), area=0.001, material_id=1),
-        defaults={"section_id": 1},
+            ],
-    ))
+        )
+    )
+    vm.apply_command(
+        ConvertElementTypeCommand(
+            vm,
+            {1},
+            "ElasticBeamColumn",
+            defaults={"section_id": 1},
+        )
+    )
     el = vm.project.element(1)
     assert isinstance(el, ElasticBeamColumn)
     assert el.nodes == (1, 2)
@@ -78,12 +117,22 @@ def test_truss_to_frame_conversion(qtbot) -> None:  # type: ignore[no-untyped-de
 @pytest.mark.gui
 def test_convert_preserves_id_and_is_undoable(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_setup()
-    vm.apply_command(AddElementsCommand(vm, [
+    vm.apply_command(
-        ElasticBeamColumn(id=42, name="A", nodes=(1, 2), section_id=1),
+        AddElementsCommand(
-    ]))
+            vm,
-    vm.apply_command(ConvertElementTypeCommand(
+            [
-        vm, {42}, "Truss", defaults={"material_id": 1, "area": 0.002},
+                ElasticBeamColumn(id=42, name="A", nodes=(1, 2), section_id=1),
-    ))
+            ],
+        )
+    )
+    vm.apply_command(
+        ConvertElementTypeCommand(
+            vm,
+            {42},
+            "Truss",
+            defaults={"material_id": 1, "area": 0.002},
+        )
+    )
     assert isinstance(vm.project.element(42), TrussElement)
     assert vm.project.element(42).name == "A"
     vm.undo_stack.undo()
@@ -93,13 +142,23 @@ def test_convert_preserves_id_and_is_undoable(qtbot) -> None:  # type: ignore[no
 @pytest.mark.gui
 def test_convert_same_type_is_noop(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_setup()
-    vm.apply_command(AddElementsCommand(vm, [
+    vm.apply_command(
-        TrussElement(id=1, nodes=(1, 2), area=0.001, material_id=1),
+        AddElementsCommand(
-    ]))
+            vm,
+            [
+                TrussElement(id=1, nodes=(1, 2), area=0.001, material_id=1),
+            ],
+        )
+    )
     before = vm.project.element(1)
-    vm.apply_command(ConvertElementTypeCommand(
+    vm.apply_command(
-        vm, {1}, "Truss", defaults={"material_id": 1, "area": 0.002},
+        ConvertElementTypeCommand(
-    ))
+            vm,
+            {1},
+            "Truss",
+            defaults={"material_id": 1, "area": 0.002},
+        )
+    )
     # Class is still Truss and the element object is unchanged.
     assert vm.project.element(1) is before
 
@@ -107,10 +166,20 @@ def test_convert_same_type_is_noop(qtbot) -> None:  # type: ignore[no-untyped-de
 @pytest.mark.gui
 def test_unknown_target_type_raises(qtbot) -> None:  # type: ignore[no-untyped-def]
     vm = _vm_setup()
-    vm.apply_command(AddElementsCommand(vm, [
+    vm.apply_command(
-        TrussElement(id=1, nodes=(1, 2), area=0.001, material_id=1),
+        AddElementsCommand(
-    ]))
+            vm,
+            [
+                TrussElement(id=1, nodes=(1, 2), area=0.001, material_id=1),
+            ],
+        )
+    )
     with pytest.raises(ValueError):
-        vm.apply_command(ConvertElementTypeCommand(
+        vm.apply_command(
-            vm, {1}, "NotAType", defaults={},
+            ConvertElementTypeCommand(
-        ))
+                vm,
+                {1},
+                "NotAType",
+                defaults={},
+            )
+        )

tests/gui/test_define_dialogs.py

@@ -27,10 +27,12 @@ def test_linear_time_series_dialog_builds_entity(qtbot) -> None:  # type: ignore
 
 @pytest.mark.gui
 def test_plain_pattern_dialog_uses_selected_time_series(qtbot) -> None:  # type: ignore[no-untyped-def]
-    proj = Project(time_series=[
+    proj = Project(
-        LinearTimeSeries(id=1, name="GravityTS"),
+        time_series=[
-        LinearTimeSeries(id=2, name="RampTS"),
+            LinearTimeSeries(id=1, name="GravityTS"),
-    ])
+            LinearTimeSeries(id=2, name="RampTS"),
+        ]
+    )
     dlg = PlainPatternDialog(project=proj, next_pattern_id=4)
     qtbot.addWidget(dlg)
 

tests/gui/test_draw_frame_tool.py

@@ -35,10 +35,15 @@ class _CanvasStub:
 def _vm_with_two_nodes() -> ProjectViewModel:
     vm = ProjectViewModel()
     vm.new_project()
-    vm.apply_command(AddNodesCommand(vm, [
+    vm.apply_command(
-        Node(id=1, coords=(0, 0, 0)),
+        AddNodesCommand(
-        Node(id=2, coords=(3, 0, 0)),
+            vm,
-    ]))
+            [
+                Node(id=1, coords=(0, 0, 0)),
+                Node(id=2, coords=(3, 0, 0)),
+            ],
+        )
+    )
     return vm
 
 
@@ -86,7 +91,7 @@ def test_self_pick_is_ignored(qtbot) -> None:  # type: ignore[no-untyped-def]
     tool.activate()
 
     tool.on_node_picked(1)
-    tool.on_node_picked(1)   # same node — should NOT create an element
+    tool.on_node_picked(1)  # same node — should NOT create an element
     assert vm.project.elements == []
     # First-node state preserved so user can finish the gesture.
     assert tool._first_node_id == 1
@@ -150,6 +155,7 @@ def test_reset_clears_first_pick(qtbot) -> None:  # type: ignore[no-untyped-def]
 def test_empty_clicks_snap_and_create_frame(qtbot) -> None:  # type: ignore[no-untyped-def]
     """Two clicks on empty grid intersections → 2 nodes + 1 frame."""
     from otko.core import GridSystem
+
     vm = ProjectViewModel()
     vm.new_project()
     vm.project.grid_system = GridSystem(  # type: ignore[union-attr]
@@ -165,9 +171,9 @@ def test_empty_clicks_snap_and_create_frame(qtbot) -> None:  # type: ignore[no-u
     tool.on_empty_clicked(0.0, 0.0, 0.0)
     tool.on_empty_clicked(3.0, 4.0, 0.0)
 
-    assert len(vm.project.nodes) == 2       # type: ignore[union-attr]
+    assert len(vm.project.nodes) == 2  # type: ignore[union-attr]
-    assert len(vm.project.elements) == 1    # type: ignore[union-attr]
+    assert len(vm.project.elements) == 1  # type: ignore[union-attr]
-    elem = vm.project.elements[0]           # type: ignore[union-attr]
+    elem = vm.project.elements[0]  # type: ignore[union-attr]
     assert isinstance(elem, ElasticBeamColumn)
     n1 = next(n for n in vm.project.nodes if n.id == elem.nodes[0])  # type: ignore[union-attr]
     n2 = next(n for n in vm.project.nodes if n.id == elem.nodes[1])  # type: ignore[union-attr]
@@ -179,18 +185,21 @@ def test_empty_clicks_snap_and_create_frame(qtbot) -> None:  # type: ignore[no-u
 def test_empty_click_reuses_coincident_node(qtbot) -> None:  # type: ignore[no-untyped-def]
     """An empty click at an existing node's location must not duplicate it."""
     from otko.core import GridSystem
-    vm = _vm_with_two_nodes()   # nodes 1, 2 at (0,0,0) and (3,0,0)
+
+    vm = _vm_with_two_nodes()  # nodes 1, 2 at (0,0,0) and (3,0,0)
     vm.project.grid_system = GridSystem(  # type: ignore[union-attr]
-        x_lines=[0.0, 3.0], y_lines=[0.0], z_lines=[0.0],
+        x_lines=[0.0, 3.0],
+        y_lines=[0.0],
+        z_lines=[0.0],
     )
     tool = DrawFrameTool(_CanvasStub(), vm)  # type: ignore[arg-type]
     tool.activate()
 
-    tool.on_empty_clicked(0.0, 0.0, 0.0)   # existing node 1 at (0,0,0)
+    tool.on_empty_clicked(0.0, 0.0, 0.0)  # existing node 1 at (0,0,0)
-    tool.on_empty_clicked(3.0, 0.0, 0.0)   # existing node 2 at (3,0,0)
+    tool.on_empty_clicked(3.0, 0.0, 0.0)  # existing node 2 at (3,0,0)
 
-    assert len(vm.project.nodes) == 2        # type: ignore[union-attr]  (no new nodes)
+    assert len(vm.project.nodes) == 2  # type: ignore[union-attr]  (no new nodes)
-    elem = vm.project.elements[0]            # type: ignore[union-attr]
+    elem = vm.project.elements[0]  # type: ignore[union-attr]
     assert set(elem.nodes) == {1, 2}
 
 
@@ -198,19 +207,22 @@ def test_empty_click_reuses_coincident_node(qtbot) -> None:  # type: ignore[no-u
 def test_mixed_node_pick_then_empty_click(qtbot) -> None:  # type: ignore[no-untyped-def]
     """First click picks existing node; second click creates new node + frame."""
     from otko.core import GridSystem
+
     vm = _vm_with_two_nodes()
     vm.project.grid_system = GridSystem(  # type: ignore[union-attr]
-        x_lines=[0.0, 3.0, 6.0], y_lines=[0.0], z_lines=[0.0],
+        x_lines=[0.0, 3.0, 6.0],
+        y_lines=[0.0],
+        z_lines=[0.0],
     )
     tool = DrawFrameTool(_CanvasStub(), vm)  # type: ignore[arg-type]
     tool.activate()
 
-    tool.on_node_picked(1)               # start at node 1 = (0,0,0)
+    tool.on_node_picked(1)  # start at node 1 = (0,0,0)
     tool.on_empty_clicked(6.0, 0.0, 0.0)  # canvas emits exact snap
 
-    assert len(vm.project.nodes) == 3    # type: ignore[union-attr]  (new node added)
+    assert len(vm.project.nodes) == 3  # type: ignore[union-attr]  (new node added)
     assert len(vm.project.elements) == 1
-    new_node = vm.project.nodes[-1]      # type: ignore[union-attr]
+    new_node = vm.project.nodes[-1]  # type: ignore[union-attr]
     assert new_node.coords == (6.0, 0.0, 0.0)
     elem = vm.project.elements[0]
     assert set(elem.nodes) == {1, new_node.id}

tests/gui/test_draw_node_tool.py

@@ -46,8 +46,12 @@ def _vm_with_grid() -> ProjectViewModel:
 # ────────────────────────── snap helper ─────────────────────────────
 def test_snap_to_grid_picks_nearest_lines() -> None:
     x, y, z = _snap_to_grid(
-        2.2, 3.7, 0.6,
+        2.2,
-        x_lines=[0.0, 3.0], y_lines=[0.0, 4.0], z_lines=[0.0, 3.0],
+        3.7,
+        0.6,
+        x_lines=[0.0, 3.0],
+        y_lines=[0.0, 4.0],
+        z_lines=[0.0, 3.0],
     )
     assert (x, y, z) == (3.0, 4.0, 0.0)
 
@@ -99,10 +103,11 @@ def test_grid_less_canvas_never_emits_to_tool(qtbot) -> None:  # type: ignore[no
     target. For a grid-less project, the canvas never emits, so the
     tool is never invoked. We therefore don't test rejection here.
     """
-    vm = ProjectViewModel(); vm.new_project()
+    vm = ProjectViewModel()
+    vm.new_project()
     tool = DrawNodeTool(_CanvasStub(), vm)  # type: ignore[arg-type]
     tool.activate()
-    assert vm.project.nodes == []     # type: ignore[union-attr]
+    assert vm.project.nodes == []  # type: ignore[union-attr]
 
 
 @pytest.mark.gui

tests/gui/test_draw_truss_tool.py

@@ -34,10 +34,12 @@ class _CanvasStub:
 def _vm_with_grid_and_nodes() -> ProjectViewModel:
     vm = ProjectViewModel()
     vm.new_project()
-    vm.project.nodes.extend([
+    vm.project.nodes.extend(
-        Node(id=1, coords=(0, 0, 0)),
+        [
-        Node(id=2, coords=(3, 0, 0)),
+            Node(id=1, coords=(0, 0, 0)),
-    ])
+            Node(id=2, coords=(3, 0, 0)),
+        ]
+    )
     vm.project.coord_systems = [
         CoordinateGridSystem(
             name="Global",
@@ -60,13 +62,13 @@ def test_two_clicks_create_truss(qtbot) -> None:  # type: ignore[no-untyped-def]
     tool.on_node_picked(1)
     tool.on_node_picked(2)
 
-    assert len(vm.project.elements) == 1     # type: ignore[union-attr]
+    assert len(vm.project.elements) == 1  # type: ignore[union-attr]
-    el = vm.project.elements[0]              # type: ignore[union-attr]
+    el = vm.project.elements[0]  # type: ignore[union-attr]
     assert isinstance(el, TrussElement)
     assert el.nodes == (1, 2)
     assert el.area > 0
     # A default ElasticUniaxial must have been created for the material.
-    assert len(vm.project.materials) == 1    # type: ignore[union-attr]
+    assert len(vm.project.materials) == 1  # type: ignore[union-attr]
     assert isinstance(vm.project.materials[0], ElasticUniaxial)
 
 
@@ -78,9 +80,9 @@ def test_draw_truss_reuses_existing_material(qtbot) -> None:  # type: ignore[no-
     tool.activate()
     tool.on_node_picked(1)
     tool.on_node_picked(2)
-    el = vm.project.elements[0]              # type: ignore[union-attr]
+    el = vm.project.elements[0]  # type: ignore[union-attr]
     assert el.material_id == 1
-    assert len(vm.project.materials) == 1    # type: ignore[union-attr]  (no new material)
+    assert len(vm.project.materials) == 1  # type: ignore[union-attr]  (no new material)
 
 
 @pytest.mark.gui
@@ -104,8 +106,8 @@ def test_empty_click_creates_node_then_truss(qtbot) -> None:  # type: ignore[no-
     tool.on_empty_clicked(3.0, 0.0, 0.0)
 
     # Two nodes created + one truss element.
-    assert len(vm.project.nodes) == 2        # type: ignore[union-attr]
+    assert len(vm.project.nodes) == 2  # type: ignore[union-attr]
-    assert len(vm.project.elements) == 1     # type: ignore[union-attr]
+    assert len(vm.project.elements) == 1  # type: ignore[union-attr]
     assert isinstance(vm.project.elements[0], TrussElement)
 
 
@@ -115,5 +117,5 @@ def test_self_pick_is_ignored(qtbot) -> None:  # type: ignore[no-untyped-def]
     tool = DrawTrussTool(_CanvasStub(), vm)  # type: ignore[arg-type]
     tool.activate()
     tool.on_node_picked(1)
-    tool.on_node_picked(1)    # same node — must not create a zero-length truss
+    tool.on_node_picked(1)  # same node — must not create a zero-length truss
-    assert vm.project.elements == []         # type: ignore[union-attr]
+    assert vm.project.elements == []  # type: ignore[union-attr]

tests/gui/test_grid_dialog.py

@@ -19,11 +19,18 @@ from otko.core import (  # noqa: E402
 @pytest.mark.gui
 def test_quick_grid_lines_produces_ordinates(qtbot) -> None:  # type: ignore[no-untyped-def]
     from otko.views.dialogs.quick_grid_lines import QuickGridLinesDialog
+
     dlg = QuickGridLinesDialog()
     qtbot.addWidget(dlg)
-    dlg._x_n.setValue(4); dlg._x_s.setValue(3.0); dlg._x_f.setValue(0.0)
+    dlg._x_n.setValue(4)
-    dlg._y_n.setValue(2); dlg._y_s.setValue(4.0); dlg._y_f.setValue(0.0)
+    dlg._x_s.setValue(3.0)
-    dlg._z_n.setValue(3); dlg._z_s.setValue(3.0); dlg._z_f.setValue(-3.0)
+    dlg._x_f.setValue(0.0)
+    dlg._y_n.setValue(2)
+    dlg._y_s.setValue(4.0)
+    dlg._y_f.setValue(0.0)
+    dlg._z_n.setValue(3)
+    dlg._z_s.setValue(3.0)
+    dlg._z_f.setValue(-3.0)
     xs, ys, zs = dlg.ordinates()
     assert xs == [0.0, 3.0, 6.0, 9.0]
     assert ys == [0.0, 4.0]
@@ -33,6 +40,7 @@ def test_quick_grid_lines_produces_ordinates(qtbot) -> None:  # type: ignore[no-
 @pytest.mark.gui
 def test_quick_grid_zero_lines_produces_empty(qtbot) -> None:  # type: ignore[no-untyped-def]
     from otko.views.dialogs.quick_grid_lines import QuickGridLinesDialog
+
     dlg = QuickGridLinesDialog()
     qtbot.addWidget(dlg)
     dlg._x_n.setValue(0)
@@ -48,6 +56,7 @@ def test_locate_origin_round_trip(qtbot) -> None:  # type: ignore[no-untyped-def
     from otko.views.dialogs.locate_origin import (
         CoordSystemLocationOrientationDialog,
     )
+
     dlg = CoordSystemLocationOrientationDialog(
         origin=(1.5, -2.0, 3.0),
         rotation_deg=(0.0, 0.0, 45.0),
@@ -65,6 +74,7 @@ def test_define_grid_data_round_trip(qtbot) -> None:  # type: ignore[no-untyped-
     from otko.views.dialogs.define_grid_data import (
         DefineGridSystemDataDialog,
     )
+
     cs = CoordinateGridSystem(
         name="Floor2",
         coord=CoordinateSystem(origin=(0, 0, 3.5)),
@@ -96,6 +106,7 @@ def test_define_grid_data_spacing_mode_conversion(qtbot) -> None:  # type: ignor
     from otko.views.dialogs.define_grid_data import (
         DefineGridSystemDataDialog,
     )
+
     cs = CoordinateGridSystem(
         name="Test",
         grid=GridSystem(x_grid_lines=make_grid_lines("X", [0.0, 3.0, 6.0, 10.0])),
@@ -117,6 +128,7 @@ def test_define_grid_data_global_name_locked(qtbot) -> None:  # type: ignore[no-
     from otko.views.dialogs.define_grid_data import (
         DefineGridSystemDataDialog,
     )
+
     dlg = DefineGridSystemDataDialog(is_global=True)
     qtbot.addWidget(dlg)
     assert dlg._name_edit.text() == "Global"
@@ -130,6 +142,7 @@ def test_define_grid_data_add_and_delete_row(qtbot) -> None:  # type: ignore[no-
     from otko.views.dialogs.define_grid_data import (
         DefineGridSystemDataDialog,
     )
+
     dlg = DefineGridSystemDataDialog()
     qtbot.addWidget(dlg)
     # Start with empty X table.

tests/gui/test_main_window.py

@@ -20,3 +20,22 @@ def test_main_window_opens(qtbot) -> None:  # type: ignore[no-untyped-def]
     window.show()
     assert window.isVisible()
     assert window.windowTitle() == "OTKO"
+
+
+@pytest.mark.gui
+def test_close_dirty_hidden_window_does_not_block(qtbot) -> None:  # type: ignore[no-untyped-def]
+    """Closing a dirty but hidden window must not raise a modal prompt.
+
+    Qt closes hidden widgets during teardown (as ``pytest-qt`` does); a
+    modal "unsaved changes" dialog there would block forever with no user
+    to answer it. The prompt is therefore gated on visibility.
+    """
+    from otko.views.main_window import MainWindow
+
+    window = MainWindow()
+    qtbot.addWidget(window)
+    window._vm.new_project()
+    window._vm.mark_dirty()
+    assert not window.isVisible()
+    assert window.close() is True
+    assert window._vm.is_dirty  # unchanged: the prompt was skipped