Conventions: language, commits, comments

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This page is the contract for who reads what, in which language, and for the shape of a commit. It is written in English on purpose: from generation 6 on, everything addressed to a developer is English, and everything addressed to a user is Persian (decision 3.3 in plan-v6/README.md). The rest of docs/reference is migrated page by page (phase 9); until then a Persian page is not “wrong”, it is “not yet migrated”.

Language by audience

Text	Reader	Language	Kept by
Code comments, JSDoc, `eslint-disable` reasons	developer	English	`darzsaz/no-persian-comment` (ESLint), `comment-pattern` (Stylelint)
Commit subject and body	developer	English, Conventional Commits	commitlint on `commit-msg` and in CI
`docs/reference/*`, `CLAUDE.md`	developer	Persian (see below)	`scripts/doc-claims.mjs` keeps its claims true
`CONTRIBUTING.md`, this page	newcomer	English	review
`docs/journal/*` — new entries	developer	English; old entries stay as written	—
Developer tooling output (`scripts/*`, guards, CI logs)	developer	English for new and touched scripts	review
Identifiers, file names, CSS class names	developer	English (as today)	—
UI strings, print sheets, CLI `--help`, error messages	user	Persian source, English via the i18n catalog	`lingui/no-unlocalized-strings`, `i18n:check`
User guide (`apps/site/.../guide`), landing page	user	Persian, with an English site	—
Plan folders (`plan-v*/`)	repository owner	Persian	—

Why English for developer text, with numbers: on 2026-09-15 the repository had 5,938 Persian comment lines out of 8,636, and 292 of the last 324 commit subjects were Persian. The code itself — identifiers, types, library APIs, the technical vocabulary of every dependency — is English, so every Persian comment switches script mid-line, is unreadable to any tool or contributor without Persian, and cannot be searched together with the code it explains. The user never sees a comment or a commit; the user does see the UI, which stays Persian.

Why the reference went the other way in phase 9.1: it had been drifting into two half-written copies, one Persian and one English covering eleven of twenty pages. Nearly half of it (darz-format.md) is generated from the schema’s Persian field descriptions, so translating it means editing the data model’s user-facing strings; the rest is read by the one person who maintains this repository, who reads Persian. One source beats two, and the audience-facing documents — the user guide and the landing page — stay in both languages. rules.en.md is the exception that proves it: it is generated from the en-US catalog and cannot drift.

Persian inside an English comment

A comment may quote Persian as a value: a UI string, a catalog name, a test fixture. The quote is the signal — «…», "…", '…' or `…`:

// The label is «کابینت ۲» in fa-IR and "Cabinet 2" in en-US; the number is user data.

Persian prose outside quotes is a Persian comment and is reported.

Commits

Format (Conventional Commits 1.0):

<type>(<scope>): <subject>

<body>

<footer>

type: feat, fix, refactor, perf, test, docs, build, ci, chore, style, revert — the set of @commitlint/config-conventional.
scope: one of core, geometry, i18n, report, ui, web, cli, site, docs, plan, tooling, deps, deps-dev, release. Several scopes are separated by a comma (fix(core,report): …); a change that touches everything has no scope.
subject: imperative, lower case, no trailing period, Latin script, header ≤ 100 characters. It says what changed, not which files.
body: what and why. If a road was tried and abandoned, it is written here — for the person who walks the same road three months later it is worth more than the fix. Lines ≤ 100 characters. Persian UI text may be quoted.
footer: BREAKING CHANGE: … when a file format, CLI flag or public API changes; Co-Authored-By: …; issue references.

Examples:

fix(geometry): open hinged fronts outward, not into the carcass

The swing sign was inverted in front-instances.ts since 52470cf: the axis was
written by hand as +1/-1 with no convention. The axis is now the cross product
of the up vector and the hinge edge; the angle comes from the hinge catalog
entry instead of a fixed 100°.

Tried first: flipping the sign only. That fixed base units and broke lift-up
doors, which rotate around a horizontal axis — hence the cross product.

chore(deps-dev): bump vitest from 4.1.11 to 4.1.12

Merge commits (Merge branch …) and reverts written by git are accepted as they are.

Enforcement

commit-msg hook: pnpm exec commitlint --edit (lefthook). Bypass for one commit only with LEFTHOOK=0, and only for a fixup that is squashed before push.
CI: every commit of the push or pull request that was made after the contract commit (d4ae1c4) is linted (commits job in ci.yml; the list comes from scripts/commit-range.mjs, by committer date, merges skipped). The pre-contract history — generation 5 and the wave-6 worktree commits merged in phase 0 — stays as written.
scripts/test/commitlint.test.mjs runs the configuration against sample messages so a config change that silently accepts Persian subjects turns the guard tests red.

Comments

Explain why, and what was tried and did not work — not what the code does (rule 4 of CLAUDE.md). Most comments in this repository are the minutes of a mistake.
English, see above. Existing Persian comments are counted in a shrink-only baseline (scripts/lint-baseline.json for ESLint, stylelint-suppressions.json for CSS): a new Persian comment in a file that has none fails lint; fixing one and not updating the baseline also fails (pnpm lint:baseline --update, node scripts/css-lint.mjs --update). The baseline only goes down; phase 8.8 of plan-v6 takes it to zero.
eslint-disable needs a reason after -- (require-description); the reason is English too.

CONTRIBUTING.md — the rules of the repository and who keeps them.
i18n.md — messages, catalogs, and why the core returns messages, not strings.
testing.md — the guard-of-guards tests under scripts/test/.
traps.md — every known trap and the guard that catches it.