# Step 0: runtime-storage-contract

## Read First

Read these files before editing:

- `/AGENTS.md`
- `/docs/PLAN.md`
- `/docs/PROGRESS.md`
- `/docs/WORKNOTE.md`
- `/docs/AGENT_RULES.md`
- `/docs/ARCHITECTURE.md`
- `/docs/ADR.md`
- `/docs/implementation-plans/domain-model-foundation-implementation-plan.md`
- `/docs/implementation-plans/analysis-model-objects-implementation-plan.md`
- `/include/fesa/core/Domain.hpp`
- `/src/core/Domain.cpp`

## Task

Create `/docs/implementation-plans/domain-runtime-storage-implementation-plan.md`.

The plan must state that `Domain` owns runtime model objects as its canonical storage:

- nodes remain value objects under `fesa::core::Node`;
- elements are stored as `fesa::element::Element` objects;
- materials are stored as `fesa::material::Material` objects;
- shell properties are stored as `fesa::property::ShellProperty` runtime objects;
- loads are stored as `fesa::load::Load` objects;
- boundary conditions are stored as `fesa::boundary::BoundaryCondition` objects;
- steps may remain `LinearStaticStepDefinition` until an analysis-step object is introduced, but step indices must reference runtime load and boundary containers;
- `core::*Definition` classes may remain as parser/factory-local records, but `Domain` must not persist them.

The plan must also list the migration order and identify the C++ tests that will be rewritten or added.

## Tests To Write First

- Documentation-only step. No C++ test is required in this step.

## Acceptance Criteria

```powershell
python -m unittest discover -s scripts -p "test_*.py"
```

## Verification Notes

1. Confirm the plan does not introduce parser implementation work.
2. Confirm the plan does not change MITC4 formulation, reference artifacts, or tolerance policy.
3. Update `phases/domain-runtime-storage/index.json` for this step result.