Analyze a session

Work the steps in order. This skill ends once the retrospective exists on disk and the operator has its path. Acting on what it recommends is separate work. Use the codex-commit skill for any change that comes out of it.

Which session

Use the absolute transcript path from the user's request. A bare session ID also works when it names exactly one file under ~/.codex/sessions/.

If the user gives neither, preflight explains how to find a session. Spawn a fresh delegated agent with fork_turns: "none". Run preflight again with the path it returns. Never load session files into model context merely to locate one because the locator can stream them.

Preflight

Run bash .agents/skills/codex-analyze-session/scripts/preflight.sh <path-or-id> and read its report.

Step 0: open the task list

Create these tasks with update_plan, then move each to in_progress and completed as you go. They're the checklist the rest of this document expands.

1. Read the lines the preflight listed
2. Test the session's own conclusions
3. Verify every figure with three agents
4. Recommend fixes across the five areas
5. Write the retrospective

Stop before any of it where preflight couldn't resolve the transcript, or reports a missing precondition. Say what's wrong and hand back.

The preflight already resolved the transcript and summarized the session. It created the retro directory at <main worktree>/.codex/retros/YYYYMMDD_<session ID>/ and copied the evidence into it. Read that report before forming any hypothesis, because it writes everything it prints to artifacts/ as well, where a later reader can check it.

.agents/skills/codex-analyze-session/references/SESSION_CLI.md documents every subcommand, for when a report needs more detail than the preflight printed.

Step 1: read the lines the preflight listed

The preflight listed the failing lines and the line ranges of each repeated sequence. Open those, and nothing else:

.agents/skills/codex-analyze-session/scripts/session.py grep <transcript> 'pattern' --context 300
.agents/skills/codex-analyze-session/scripts/session.py show <transcript> 361,408,1938

grep searches the decoded content blocks, so what prints matches what the model saw. Add --kind THINK to read what the agent believed at the time, which is often where an error begins. show prints whole records, once a report has given you a specific line number.

Step 2: test the session's own conclusions

A transcript records what an agent believed, which isn't always what was true. Treat every claim in it as a hypothesis with a line number attached, including the agent's own corrections.

Re-run the decisive command wherever that environment still exists.

Check that a test can fail before trusting a result of zero. A test returning nothing may mean the thing is absent, or may mean the test stopped examining anything. Give it a case that must produce output, and treat an empty result as evidence only after that check passes. A test that has stopped examining anything reports nothing whatsoever, where a working one still returns unrelated findings alongside the empty answer.

Step 3: verify every figure with three agents

Readers trust a number more than a description, so a wrong count does more damage than a wrong impression. No figure reaches the operator without independent replication.

Follow .agents/skills/codex-analyze-session/references/VERIFY_FIGURES.md. It gives the claims table format, the prompt each verifier receives, the isolation rule for verifiers that write files, and how to settle a figure they disagree on.

Hold every figure until all three report. A verifier that hasn't answered yet isn't an abstention, and counting it as one discards the report most likely to disagree.

Step 4: recommend fixes across the five areas

Step 3 runs identical prompts, because replication gains nothing from a division of labor. This step does the opposite, giving each agent one area so the recommendations stay distinct.

Follow .agents/skills/codex-analyze-session/references/FIX_SURFACES.md. It names the five areas, the shared prompt, and the block each agent receives.

Synthesize the results yourself. Each agent sees one area, while this session has the verified figures and the full set of findings that no agent had alone.

Step 5: write the retrospective

Fill in the RETRO.md the preflight created, following .agents/skills/codex-analyze-session/references/WRITING_THE_RETRO.md.

Cite a line number for every claim. Rank findings by round trips wasted rather than by how irritating they were. State what each fix costs as well as what it improves, and give the operator the retro path when you report back.

Preconditions

This skill assumes the shared tbhb toolchain:

• uv on PATH, which the session.py shebang uses to select an interpreter
• a git repository, because the retro directory resolves from the main checkout
• a transcript path or session ID naming exactly one file

Preflight checks each. Where one is missing, tell the operator rather than improvising a substitute.