Prevent a repeat mistake

Turn a mistake that must not come back into a fix that stops it, placed at the strongest level that works. The mistake may have repeated already, or a retro (diagnose-session, review-recent-work) may have found it once and routed it here: either way, one occurrence quoted from evidence is enough to start. The files can be anything: code, a knowledge base of notes, plans, a roadmap, a business strategy. Done means each mistake has a fix that is either in place and proven, or drafted and waiting for the user's approval.

Procedure

1. Pick up pending drafts. Read *-repeat-mistake.md in product/retros/ and .agents_workspace/retros/ and list every fix still awaiting approval before taking a new mistake, so a draft from an earlier session is not lost.

2. Name the mistake from evidence. Quote what went wrong: the tool call, the file and line, the wrong output, and the correction that preceded it. "Was sloppy" is not a mistake, "wrote dates as 10/09/2026 in roadmap.md:14 after being told ISO dates" is. If you cannot quote it, stop: there is nothing to fix yet. To find the mistakes in a whole session rather than one, ceh-session-diagnosis:diagnose-session reads its transcript and routes each one here.

3. Climb the ladder, strongest first. Stop at the first rung that would have caught this exact mistake:

   Rung	In code	In notes, plans, or documents
   1. Remove the cause	Delete the second code path, merge the duplicate	One source note instead of copies, a template, rename what misleads
   2. Claude Code setting	A permissions.deny rule in settings.json	The same: deny writes to a folder that must not change
   3. Check at write time	A type, a lint rule, a hook	A frontmatter schema, a link or date-format check, a hook
   4. Check before landing	A test, a CI job	A validator script, a CI job, a checklist the file itself carries
   5. Written guidance	CLAUDE.md, a skill, a code comment at the trap	CLAUDE.md, memory, a style note in the folder

   Rung 5 is for judgment calls nothing mechanical can check. Choosing it for a mistake that a pattern match would catch is choosing the rung that already failed.

4. Build or draft the fix. Build rungs 3 and 4 when they live in the current repository and touch nothing else: they are checks that prove work, and the contract allows them. Draft, do not apply, anything that changes how later sessions behave or rewrites the user's content: rung 1, rung 2, a hook, and every rung 5 edit (CLAUDE.md, memory, a skill, a plugin). Show the draft and wait for approval.

5. Prove it. Replay the real mistake against the fix and show it fails, then show the correct version passes. Keep the failing case as a test or fixture where the repo has a place for one. A rung 5 fix cannot be proven this way: say so, and say why no higher rung fit.

6. Save and report in the format under Output.

Rules

• One mistake per fix. A fix aimed at two mistakes usually stops neither.
• Fix the class, not the instance: the check catches every future 10/09/2026, not only the one in roadmap.md.
• A new check must not fail on correct existing files. Run it over what is already there before calling it done, and fix or exempt real violations only with the user's approval.
• Correcting the file the mistake landed in is part of the fix, but it is not the fix.

Output

Save by where each fix lands, appending when the file exists and creating the directory if needed. Fixes that land in the current repository go to product/retros/<YYYY-MM-DD>-repeat-mistake.md, committed with the first fix applied, because a later session working in the repo reads it. Mask secrets in its quotes as <secret>: a committed file leaves the machine on the next push. Fixes outside it (user settings, the global CLAUDE.md, memory, an installed plugin) go to .agents_workspace/retros/<YYYY-MM-DD>-repeat-mistake.md, local, because only the user acts on them. When both files exist, each links the other through other_file. Reply with the same table. Each fix awaiting approval carries its full draft below the table, so a later session can apply it from the file alone. When a draft is applied or rejected, update its Status in the file it was saved in.

Each file fills references/repeat-mistake.template.md: the table, then for each rung chosen one line on why the rungs above it did not fit, then each pending draft in full. Appending to an existing file adds rows and drafts, and leaves its frontmatter as it is.