TDD — Test-First Execution

Choose the branch before selecting a model. Coordinator work and deterministic commands proceed within invocation authority. Apply this method in the current role. It does not dispatch a worker. For a worker dispatch, use shared/references/model-preview.md and its one approved route snapshot. Nested skills and runners consume it without another selection or worker.

The Iron Law

Establish a failing behavioral case before a requested behavior repair. Reuse a captured failure when it proves the same defect on the same code.

• Preserve existing valid work. Do not delete and recreate code solely to change the order of its history.
• A passing new test can characterize existing behavior. It does not demonstrate a missing behavior or prove that the test is wrong. Use a relevant failure or controlled counterexample to establish what it detects.

Step 0 — whose code is this?

For a risky change to untested legacy code, apply safe-incremental-coding for the missing characterization. Reuse existing behavioral and failure evidence that covers the changed surface. Proceed directly when that protection already exists.

The loop

Run one loop per increment of behavior. Keep each pass small enough that you could throw it away without grief.