Lesson 384 of 2116
Writing Codex Task Briefs That Produce Small Diffs
The quality of a Codex run mostly depends on the brief. Learn the five fields that turn a fuzzy request into a reviewable patch.
Lesson map
What this lesson covers
Learning path
The main moves in order
- 1A Brief Is a Guardrail
- 2task brief
- 3acceptance criteria
- 4file scope
Concept cluster
Terms to connect while reading
Section 1
A Brief Is a Guardrail
Codex is good at exploring. Production engineering is usually about exploring only as far as the task requires. A brief narrows the search space so the resulting diff is easy to understand, test, and review.
- 1Goal: the user-visible change or question to answer.
- 2Scope: files, modules, routes, or packages Codex may touch.
- 3Constraints: style, performance, privacy, compatibility, and what must not change.
- 4Acceptance checks: commands, smoke tests, screenshots, or manual cases.
- 5Output format: patch, PR, audit notes, or a recommendation without edits.
A Codex-ready brief keeps the agent inside a reviewable lane.
Goal: Fix the dashboard filter reset bug.
Scope: src/components/dashboard-filter.tsx and tests only.
Constraints: keep URL query params backward-compatible; do not touch styling.
Acceptance checks: npm run lint, npm run typecheck, dashboard reset test passes.
Output: explain the bug, the fix, and any test coverage added.Compare the options
| Weak prompt | Codex-ready brief |
|---|---|
| Make search better | Add keyboard focus retention to search results after pagination in src/components/search-browser.tsx |
| Fix auth | Find why expired session cookies still show the dashboard; do not change signup flow |
| Audit models | Compare model IDs in content JSON against OpenAI docs and report stale entries without editing |
Key terms in this lesson
The big idea: Codex does not need a long prompt. It needs a bounded prompt with a definition of done.
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