Implement the fix

Input: an approved FIX.md. Output: one commit containing the fix, its regression test, and any fixture updates FIX.md authorized — nothing else.

Procedure

1. Touch only FIX.md's change sites. If implementation reveals a needed site FIX.md missed, STOP: amend FIX.md first (one commit), then continue. Silent scope growth is the failure mode this workflow exists to prevent.

2. Write the regression test first, converting the REPRO artifact: it fails before your change, passes after. Its docstring names the live run/record that motivated it (e.g. "Regression (selfstudy run-9175f0ec): ..."), so the next reader can find the evidence. Build it to dr-execute-step's "Durable tests, checks, and probes" rules — committed evidence only, meaning over form, mutation-proved, wall-clock scrubbed recursively, absence-tolerant — so it survives repo changes and fails only when the defect returns.

3. Apply the code change. Comments state the constraint the code cannot show ("compare by handle index, not mapping order: canonical JSON sorts keys"), never the change's history or your reasoning.

4. Run outward rings, stop at first failure:

    pytest <regression test> -x -q
    pytest <the changed subsystem's test files> -q
    pytest tests/ -q -n 4          # full gate, ~8 min
   

   The full gate must report 0 failed. A pre-existing failure you did not cause: stop, report, do not "fix it while you're there." If FIX.md's change sites touch the packaging surface (pyproject entry points, CLI commands, MCP tools/schema, wheel layout), one more ring the gate does not run: python scripts/wheel_smoke.py, with its pinned expectations updated in this same commit.

5. A gate failure caused by your change is information: if a fixture depended on the defective behavior (FIX.md predicted it), update the fixture minimally so it exercises what the test actually guards; if the failure is NOT predicted by FIX.md, your fix is wrong — revert to the last green state and return to the orchestrator for re-diagnosis. Never weaken an assertion to green.

6. If a live run root is needed for the next phase and the identity is occupied: retire it — procedure canonical in dr-drive-harness §3 (retire by rename, commit the rename FIRST as its own commit).

7. Update the map in THIS commit — see "Map obligations" below.

8. Before committing, run the mechanized budget gate against FIX.md's Estimated-diff ceiling — the same instrument dr-execute-step uses for Family-2 steps, so this check can no longer be an eyeballed git diff --stat compare:

    python tools/diff_budget.py <tranche-base> --ceiling <FIX.md's
      Estimated-diff ceiling> --paths <FIX.md's change sites>
   

   Read DIFF_BUDGET_RESULT_V1.verdict. WITHIN/NO_CEILING: continue. EXCEEDED is a STOP in the standard format (decision, priced options, recommendation), not a footnote — the by-eye version of this check missed an over-budget diff before this gate existed (V1 tranche 2026-08-05: 193 insertions landed against a <=150 ceiling with no stop). Then commit once, push with retry:

    git add <exact files> <map files> && git commit -m "<what and
      why, with the live evidence and 'Full gate: N passed, 0
      failed'>"
    git push -u origin <branch>   # retry x4, backoff 2s 4s 8s 16s
   

Map obligations (docs/map/)

Same procedure dr-execute-step uses for Family-2 steps (same commit not a follow-up; SEAM before subsystem docs; new invariant needs a new check; advance Verified-at: only if re-run; docs_verify full + --audit must pass before commit) — canonical there, not restated here. One Family-1-specific addition: every fix earns a Traps entry in the SUB-/CON-/SEAM- document covering the changed code. A defect that reached the record is exactly the memory the map exists to keep. Name the run id or the tranche. Never delete an old Traps entry — rewrite it to say it was fixed and when.

Prohibitions

• No drive-by refactors, renames, TODO cleanups, or formatting churn.
• No new dependencies, no config default changes, unless FIX.md lists them as change sites.
• Never edit committed run roots; never commit env files — both procedures canonical in dr-drive-harness §1/§3.

Exit criteria

• One pushed commit (plus at most one root-retirement commit).
• Full gate output pasted into the tranche log: N passed, 0 failed.
• python tools/docs_verify.py passes, and the map documents covering the changed code carry a Traps entry for this defect.
• Return to the orchestrator.