Recall Reasoning Skill for Codex

Recall Reasoning

Recover the reasoning behind a change. Prefer Codex session history when it can be found; otherwise derive the explanation from git history and current code.

Inputs

Accept any of:

• A commit SHA
• A file path, optionally with a line number (<path>:<line>)
• A reviewer question plus surrounding context

If only a file is given, use git blame to resolve the commit that last touched the line.

Step 1: Resolve the Commit

Resolve the target commit:

git rev-parse <sha>
git blame -L <line>,<line> -- <path>

Collect the commit subject, changed files, and relevant diff:

git show --stat --oneline <sha>
git show -- <path>

Step 2: Search Codex Session History

If Codex session files are available, search them for the commit SHA, touched file paths, branch name, and distinctive user request text:

Write the patterns to a file with apply_patch, one per line, then match them literally:

rg -F -f <pattern-file> ~/.codex/sessions

-F is required, not just safer: an unescaped $ inside request text is a regex anchor and silently drops the match.

Read only the smallest relevant transcript excerpts. Prefer sessions close to the commit time and sessions that mention both the file and the task.

If no matching session is found, continue with the fallback path.

Step 3: Synthesize

If session reasoning was found:

• Lead with the why. The diff already shows the what.
• Quote or paraphrase only the relevant reasoning.
• Keep the explanation to one or two paragraphs.

If no session reasoning was found:

• Read the commit diff and surrounding current code.
• Infer the most likely rationale from the code, tests, plan/spec artifacts, and PR context.
• Mark the output as fallback-derived.

Step 4: Output

When session reasoning was found:

**Commit:** <short-sha> — <subject>
**Session:** <session reference>

<one or two paragraphs of reasoning>

When no session reasoning was found:

**Commit:** <short-sha> — <subject>
**Session:** none found

<fallback explanation derived from git history and current code>

Then call update_plan to mark this step completed and continue with the next step of the active workflow.

Rules

• Treat session excerpts as evidence, not ground truth.
• Do not read full transcript files unless excerpts are insufficient.
• If current code contradicts a remembered rationale, note the discrepancy.