Writing Codex Briefs

Codex sees zero chat history. The brief is the only channel. Anything not in it does not exist for Codex.

The Acceptance File — .codex/ACCEPTANCE.md

Written and committed BEFORE dispatch. This is the frozen bar the judge will enforce.

GOAL: <one sentence: what "done" means>

CHECKS (all must pass, exact commands):
- `<command>` exits 0 and prints <expected>
- `<build/typecheck command>` exits 0
- `<specific test command>` exits 0

CONSTRAINTS:
- Only edit <files/dirs>. Do not modify <test files / this file / unrelated code>.

Writing checks that protect you (the judge is only as strong as these):

• Prefer commands with exit codes over "the code should look right".
• Include at least one check that fails before the work is done (red → green) — a check that passes on the untouched repo proves nothing.
• Name the specific tests, not "run the tests" (slow suites make the judge cry wolf; flaky checks are worse than none).
• Vacuous bars ("typecheck passes") let bad work through with a green light. Ask: could a lazy stub pass these checks? If yes, tighten them.

The Brief

GOAL: <same one sentence — must match ACCEPTANCE.md>
CONTEXT: <repo path, key files, constraints — everything Codex needs, it cannot ask you>
DO: <numbered, concrete steps>
VERIFY: <run the exact CHECKS above and show their real output>
REPORT: <what to return: diff summary + which checks passed>
DO NOT: commit anything; touch .codex/ACCEPTANCE.md; edit unrelated files;
        delete or weaken tests; add silent fallbacks or fake/stubbed results.

The DO NOT block is mandatory and always includes those five items — they are the exact ways executor models paper over failure.

Common Mistakes

• Context by reference ("as discussed above") — Codex has no "above". Inline it.
• Goal drift — brief GOAL ≠ ACCEPTANCE GOAL means the judge enforces a different bar than Codex aimed at.
• Kitchen-sink briefs — one dispatch, one goal. Two unrelated goals = two dispatches.