# Step 9: legacy-definition-compatibility

## 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/Domain.hpp`
- `/tests/core/domain_storage_test.cpp`
- `/tests/core/domain_model_object_test.cpp`

## Task

Preserve and document compatibility between existing `*Definition` value objects and new model-object base classes.

Allowed files:

- Modify `/docs/implementation-plans/analysis-model-objects-implementation-plan.md`
- Modify tests only if compatibility gaps are found
- Modify production code only for narrow compatibility fixes

Required behavior:

- Existing Domain definition-storage tests still pass.
- New model-object ownership tests still pass.
- The implementation plan clearly states that `*Definition` objects remain parser/factory DTOs until the parser phase decides whether to map or replace them.

## Tests To Write First

If production code must change, write or extend a failing C++ test before the change. If this is documentation-only, do not add production code.

## Acceptance Criteria

Run:

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

Update step 9 status.

## Do Not

- Do not delete existing `*Definition` headers or tests.
- Do not rewrite parser or factory behavior.