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Use this when a project already has code, tests, and docs, but intent is unclear.

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Problem

Legacy projects have behavior spread across code, tests, docs, and team memory. AI changes are risky because there is no clear contract.

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Outcome

You get a baseline spec that reflects current behavior, then tighten it over time.

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High-level walkthrough

  1. Pick one critical area first, not the whole repo.
  2. Write a spec that describes current behavior and known constraints.
  3. Link that spec to existing tests and docs in verification.
  4. Run spec check to surface missing coverage and weak spots.
  5. Fix one drift item at a time and keep iterating.

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Codex example prompt

Start with module X only.
Read current code, tests, and docs, then write a spec that matches real behavior.
Do not change runtime behavior yet unless needed for correctness.
Run spec check and list missing coverage.

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Any coding agent prompt

Create a baseline spec for the selected module from existing behavior.
Map spec claims to current tests and docs.
Run spec check and report what is not covered yet.

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Verify

  • Confirm the spec matches current shipped behavior.
  • Confirm each key requirement has at least one verification reference.
  • Track unresolved gaps as explicit follow-up work.