ai-note — save what it cost you to find out

What it produces

A block in the repository's DECISIONS.md. One decision, one ## D-NNN block, with the sections below. Or, when the finding belongs in the docs, prose handed to ai-write. This skill creates no file of its own.

Steps

1. The bar is thirty minutes. If it took less than that to work out, it will take less than that again, and a note about it is noise that hides the ones that matter.

2. Append one block. Do not rewrite an older block. The heading is the id the git floor counts:

   ## D-NNN: <what we do, in one line>
   
   Status: Accepted · Date: YYYY-MM-DD
   
   ### Context
   
   What forced the choice. Include `found`, `commit`, the files it describes, and `still_true_when`, so a later reader can tell if it rotted.
   
   ### Decision
   
   What we do, specific enough to check in the code.
   
   ### Consequences
   
   - What this makes easy
   - What this rules out
   
   ### Alternatives considered
   
   - **<Option>:** why not

3. The Decision is the value. Context is why anybody will believe it.
4. Point at the evidence. The command you ran, its output, the line in the vendor's source. A note whose claim cannot be re-checked becomes folklore within a quarter.
5. If the note is a workaround, say what would remove the need for it, and where that fix would live — upstream, in our code, or in a decision somebody has to make.
6. Searching: git grep over DECISIONS.md is the whole query engine, and it is enough at this size. Read the header of anything you find and check still_true_when before you act on it.
7. When a note stops being true, delete it in a commit that says why. A wrong note is worse than no note, because it is trusted.
8. Persistence beyond this repository is not this skill's work and not this framework's. The note is committed markdown in the user's own repository, which is where it can be reviewed, dated and deleted; whatever memory system the host provides keeps its own copy on its own terms. A learning store inside the framework would be a second source of truth for something git already versions, and the second one is always the stale one.

What this is not

• "It was quick but painful, so it deserves a note" — the bar is thirty minutes: a note about something that took less is noise that hides the ones that matter.

Done when

• The header names a commit and the files the note describes.
• Somebody who was not here could re-run your evidence and reach the same conclusion.
• It reads like a warning to a colleague, not like documentation.

Routing

In scope — routes here:

• "save this" — the shortest form of the trigger, and the thirty-minute bar decides whether it is worth a note at all.
• "write down what we learned, that cost us the whole afternoon" — exactly the bar: a finding that will cost the same again if nobody writes it down.
• "note that the settings writer merges instead of replacing, we lost an hour to that" — a non-obvious behaviour, written as what you expected, what happened, and what to do about it.
• "remember this workaround and why we still need it" — a workaround also records what would remove the need for it and where that fix would live.
• "do we have notes on the plugin loader" — searching the notes is part of this skill, and git grep over DECISIONS.md is the whole query engine.
• "what did we find about the hook timeout last time" — the same search, and the answer starts by checking the note's still_true_when before anybody acts on it.
• "the log is huge, keep the note small" — quote the head and the tail, mark the elided middle, and never drop a failure line.
• "turn this session into a skill" — the session has a generalisable process: write the contract-clean SKILL.md skeleton naming the steps, never the chat; the craft gate judges it.

Not for:

• "and turn that into a section of the handbook" — use /ai-write, because the note stays a finding and the handbook gets a document written against the tree.
• "write down the decision and the options we turned down" — use /ai-brainstorm, because a decision needs its evidence, its two real options and its authority, and a note is a finding, not a decision.
• "onboard me on this module" — use /ai-explore, because that is a tour read out of the repository for somebody who has just arrived, not a warning saved from a lost afternoon.
• "check whether the vendor fixed this in the new release" — use /ai-research, because that answer is outside this repository and has to come back cited; a note only records what we already found here.
• "this is failing again, work out why" — use /ai-debug, because a symptom needs a cause at file:line and a check that fails for it, not a note.
• "open the PR with this note in it and close the ticket" — not here: the pull request and the closing keyword are not this skill's work; it writes and commits the note and nothing else.
• "look over the diff that came out of this investigation" — use /ai-verify, because judging a change is a separate pass from recording what we learned making it.

The ai-engineering seam

1. Writes a block in DECISIONS.md or hands the prose to ai-write — it does NOT create a file of its own: the method travels intact, but the output lives where somebody will re-read it, not in a notes folder nobody opens twice. A finding with no home in DECISIONS/docs is a finding nobody re-reads.

Lifecycle

Lane: any Writes: DECISIONS.md Read by: the agent, which reads DECISIONS.md whole Dies: never — it deliberately owns no file of its own Next: none

Source: ai-engineering (own), Apache-2.0.