# Step 1: node-model-class

## Read First

Read these files before editing:

- `/AGENTS.md`
- `/docs/AGENT_RULES.md`
- `/docs/ARCHITECTURE.md`
- `/docs/implementation-plans/analysis-model-objects-implementation-plan.md`
- `/include/fesa/core/Node.hpp`
- `/tests/core/node_test.cpp`

## Task

Refine the existing `Node` model class contract without adding solver state.

Allowed files:

- Modify `/include/fesa/core/Node.hpp`
- Modify `/src/core/Domain.cpp` only if constructor/accessor definitions move or change
- Modify `/tests/core/node_test.cpp`

Required behavior:

- `Node` exposes `id()`, `coordinates()`, `x()`, `y()`, `z()`.
- `Node` exposes `static constexpr std::size_t dofCount()` or equivalent compile-time DOF count of 6.
- `Node` does not store equation ids, displacements, residuals, reactions, or constraints.

## Tests To Write First

Extend `/tests/core/node_test.cpp` before production changes:

- Verify `Node::dofCount() == 6`.
- Verify coordinate order is preserved.
- Verify the returned coordinate data is const from a const `Node`.

Run the targeted build and confirm RED before implementation.

## Acceptance Criteria

Run:

```powershell
python scripts/validate_workspace.py
ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R domain
```

Update `/phases/analysis-model-objects/index.json` step 1 with status and summary.

## Do Not

- Do not add equation ids or solver state to `Node`.