Project conventions

A convention document is the set of decisions a fresh agent would otherwise guess differently every time, as short checkable rules in the repo's AGENTS.md (or CLAUDE.md, whichever the repo uses; AGENTS.md if neither).

What earns a rule

All five hold, or the candidate is dropped, naming the one that fails.

1. Contested: a competent developer could defensibly do it the other way.
2. Recurring: a one-off belongs in a code comment.
3. Consequential: breaking it costs rework or silent drift.
4. Checkable: a reviewer can point at a line and say yes or no.
5. Not tool-enforceable: what a linter, formatter or type checker can enforce is configured there.

Never a rule: formatting, casing, import order, line length; a restated general principle; an aspiration with no test; code that does not exist yet.

Rule shape

N. **MUST <imperative>.** <the cost of not doing it, or where it lives.> <optional: one path or symbol.>

• Two or three sentences, under 50 words. MUST for invariants, SHOULD for strong defaults.
• The real symbol, path or command, never a paraphrase of the idea.
• Every rule states its cost: a rule whose reason is invisible gets rationalised away.

<Good> `2. **MUST derive DB-row types from Drizzle, never hand-write them.** Use `typeof <table>.$inferSelect`, or the aliases exported from the project's db package. Hand-written copies drift from the schema silently.` </Good>

Modes

• bootstrap, a new codebase. Read the stack first: the foundation reference when the project has a roadmap, its boards in aiview, any conventions file present. Ask only what none answers, through the interview skill, on the decision points that stack forces (decision-points.md). Write an ## Architecture (context you must not break) section and the rules the answers produce. Stop at 5 to 8: rules written before the code are guesses.
• harvest, an existing codebase. Read the source and recent history for patterns followed but unwritten, and for places the codebase contradicts itself. Propose each with its evidence: the files that comply and the ones that do not. A pattern with no counter-example may not need writing down. A pattern broken in three places is a rule or a mistake: say which.
• capture, a decision just made. Run the five filters, write it in the shape, place it in its section.

The vendor's own docs

Before rules for a stack not yet codified, read its makers' guidance, official domain only, and note the major version read.

• The docs yield candidates, which still face the five filters.
• Cite the URL in the rule. A rule that departs from official guidance says so and why.
• Where the docs are silent, say so and decide on the merits.
• A framework with a catalogue at references/framework-<name>.md (references/framework-angular.md today): read it after the stack catalogue, when that tier is about to get real. A framework without one gets a catalogue first: per fork, the official URL, the major version read, and two lines that let someone who does not know the framework judge it.

Placement and numbering

• Numbering is append-only: AGENTS EXCEPTION (rule 11) markers in the code point at numbers.
• Run node scripts/rules.mjs before writing a rule and before saying a marker holds: it prints the rules, the next free number and every marker with the rule it cites, exit 1 on a marker citing no rule or on a duplicate number.
• Group under the headings the document already uses; a new heading waits for its third rule.
• Two clauses near the top of every document, once. The escape hatch: a rule may be deviated from at a specific site with a comment beginning AGENTS EXCEPTION (rule N): and the reason; without one, deviation is a review finding, and so is a marker whose reason does not hold. The capture clause: a decision made during a session that would pass the five filters is said in chat before the session ends, and written only on the person's yes.

Output

Show the exact markdown block and where it goes; apply on confirmation. A proposal that contradicts an existing rule names its number, and superseding is the person's decision.