# AGENTS.md — The documentation standard

This file is the contract for every Markdown surface in the repo: each tier's job, the writing rules, and the word budgets the `verify-doc-budgets` gate enforces. The audit/apply workflow is the [dsh-doc-standards](../.agents/skills/dsh-doc-standards/SKILL.md) skill; the decision record is [the doc-tiers-and-budgets RFC](rfc/implemented/process/2026-07-04-doc-tiers-and-budgets.md).

## The tier taxonomy: one home per fact

Every fact has exactly one home — the tier whose job it is — and every other place that needs it links there instead of restating it. A rule restated in two files drifts word-by-word until the copies disagree; a link cannot drift, and `verify-md-links` keeps it resolving.

| Tier | Job | Does NOT belong there |
|---|---|---|
| Root `AGENTS.md` | Standing orders: rules an agent needs in context in every session, one to three lines each, linking its home | Stories, worked examples, situational procedures, anything restated from a linked home |
| Subtree `AGENTS.md` (`packages/`, `examples/`, `docs/`) | Orders specific to that subtree | Repo-wide rules the root file already carries |
| [architecture.md](architecture.md) | The system map: services, the loop, extension seams — read before changing `packages/` | Type shapes (→ core-data-structures), per-package detail (→ package READMEs), decision rationale (→ RFCs), implementation-status annotations |
| [core-data-structures/](core-data-structures/core.md) | The type catalog: literal shapes and semantics of the spine and seam vocabulary | Behavior narration (→ architecture.md) |
| [rfc/](rfc/README.md) | Decision records: the why and the what-was-given-up; `implemented/` RFCs describe shipped reality in present tense | Migration plans, test checklists, and spec-speak ("should…") once the decision has shipped |
| [postmortem/](postmortem/README.md) | Incident stories — the only tier where war-story narrative belongs | — |
| [cookbook/](cookbook/adding-a-package.md) | Step-by-step how-tos with numbered verify steps | Design rationale (→ the RFC each guide links) |
| Package README | The per-package contract: config, semantics, limitations, extension points | JSDoc restatement, generated-catalog restatement (event/tool tables), other packages' concerns |
| [development.md](development.md) | Human-facing setup and daily workflow; a bilingual pair under the [i18n contract](i18n/README.md) | Gate-by-gate enumerations that drift from `package.json` scripts |
| Generated catalogs: [cordis events](cordis-catalog/events.md), [cordis services](cordis-catalog/services.md), [tool-catalog](tool-catalog/tools.md), [persistence-catalog](persistence-catalog/log-events.md), [module-graph.md](module-graph.md) | Exhaustive enumerations regenerated from source, freshness-gated | Hand edits of any kind |
| Skills (`.agents/skills/`) | Workflows: how to carry out a recurring task against the contracts | The contracts themselves (→ docs) |

Placement test: a story about a bug → postmortem. Why we chose X → RFC. How to do task Y → cookbook. What type Z looks like → core-data-structures. What package P promises → its README. A rule every agent must always obey → root AGENTS.md, one line, linking the home that holds the why.

## Writing rules

- **Document the current state — never the process or history that produced it.** Prose describes what the code IS and why, as if it had always been so: no "previously/now/no longer/used to/renamed/moved here", and never name a change unit the reader cannot see — a PR, commit, or stack position — in comments, JSDoc, or test names; name the mechanism instead. A genuinely clarifying contrast is framed against the live alternative as a standing fact, not against the past. The change story belongs in the commit message, the PR description, or an RFC.
- **A decision worth re-litigating gets an RFC in the same PR.** The test: would a maintainer six months out ask "why was it done this way?" and find no answer in the code? If yes, write one ([when to write one](rfc/README.md)); mechanical or self-evident changes need none.
- **One physical line per paragraph** (`verify-md-wrap`): the editor soft-wraps; hard breaks make a one-word edit re-diff the whole paragraph. Prose only — code blocks, tables, and list structure stay; code comments stay under the linter's column limit.
- **Fenced `ts` blocks must compile** (`doc-typecheck`); a pasted type definition is fenced ` ```ts type-equiv ` and registered in the manifest so it cannot drift ([mechanics](development.md#documenting-types-verbatim-ts-type-equiv)).
- **Every new event's JSDoc carries an `@mode` tag** (emit | waterfall | parallel | serial); the catalog generator hard-errors without it. Write the JSDoc to stand alone — it becomes the catalog entry ([catalog RFC](rfc/implemented/process/2026-06-20-generated-cordis-catalog.md)).
- **The [core-data-structures catalog](core-data-structures/core.md) updates in the same change** that reshapes a documented type. `verify-type-equiv` catches drifted pastes, not never-documented new types ([what counts as core](core-data-structures/core.md#what-counts-as-core)).
- **Bilingual pairs update together**: editing either side obligates the counterpart and a re-record in the same change ([i18n contract](i18n/README.md)).

## Budgets and the ceiling gate

Standing docs accrete: every PR has a lesson it wants to append, and without displacement pressure nothing ever leaves. The gate is that pressure. [scripts/doc-budgets.manifest.json](../scripts/doc-budgets.manifest.json) lists the accretion-prone standing docs with a word ceiling each; `pnpm run verify-doc-budgets` (part of `doc-sync`, so CI and pre-push run it) fails when a doc exceeds its ceiling, and fails when a budgeted file is missing so a rename cannot orphan its budget.

- Ceilings are an enforcement frontier with working headroom: a ceiling sits at least 5% above the doc's current size — routine edits pass, real growth trips the gate — and ratchets down, keeping the margin, as the doc reaches target. Target budgets: root `AGENTS.md` ≤ 1,500 words; `architecture.md` ≤ 1,800; each subtree `AGENTS.md` ≤ 600, except this file (which carries the standard) ≤ 1,250; `packages/README.md` ≤ 600.
- When the gate goes red, the fix is to relocate or condense per the taxonomy above. Raising a ceiling is the last resort: the PR must justify it; the manifest diff is the reviewable act.
- Unbudgeted tiers (package READMEs, RFCs, reference matrices) have no ceiling — length is legitimate there when every row is a fact. Review and the slop checklist govern them instead.

## The slop checklist

Hunt these in any doc; the [dsh-doc-standards](../.agents/skills/dsh-doc-standards/SKILL.md) skill runs this list as an audit:

- The same rule stated in more than one home. Grep a distinctive phrase; keep one home, convert the rest to links.
- Narrated history: "previously", "now", "no longer", "used to", "renamed", "was moved", references to PRs or commits. State the current fact; the why belongs in an RFC, the story in a postmortem or git.
- A war story told inline where a one-line rule plus a postmortem/RFC link would do.
- Implementation-status annotations in prose or diagrams ("implemented!", "future: …"). Status rots; the repo layout and package manifests carry it.
- Hand-restating a generated catalog or JSDoc: event tables, tool arg tables, method signatures. Link instead.
- Paragraph walls: one paragraph carrying several rules and parenthetical asides. Split it, or demote the detail to the linked home.
- Emphasis inflation: bold, CAPS, or "critically" everywhere means nothing stands out. Reserve emphasis for the clause that changes behavior.
- Spec-speak in `implemented/` RFCs: "should", migration plans, acceptance checklists. An implemented RFC describes what is, per [rfc/implemented/AGENTS.md](rfc/implemented/AGENTS.md).

## Cross-reference with machine-checkable links, never free prose

When one doc refers to another doc, an RFC, a package README, or any file in the repo, link it with a relative Markdown link to the actual path — never bare prose or a number ("see RFC 005"), which is uncheckable and rots on rename. `pnpm run verify-md-links` (part of `doc-sync`; see [the cross-link lint RFC](rfc/implemented/process/2026-06-18-markdown-cross-link-lint.md)) fails when a relative target does not exist, so a rename that orphans a link is caught before review. This is also why RFC files carry dates and topics instead of stable numbers: they survive moves between lifecycle and class folders without dangling references.

The gate checks file existence, not `#anchor` validity — verify anchors yourself when linking to one.
