`components/AGENTS.md` is the reference: what to use for a given need,
where a new component goes, and the style / i18n / a11y / test rules.
`desktop/AGENTS.md` now routes here — the line it replaces ("reuse the
existing desktop design system") named nothing to look up and so was not
an executable instruction for a person or a model.
`docs/component-library-plan.md` keeps the audit evidence and a record of
what actually shipped, including where the plan was wrong.
Two rules earned their own sections because the library broke them
itself:
- Overriding a component's utility with `className` does not reliably
win. Tailwind sorts same-utility arbitrary values by value and takes
the last, regardless of the order they were passed. `hoverTone="danger"`
was a no-op with exactly the two tones it was built for, and its test
passed because it only asserted the red class was *present*, never that
the neutral one was gone. Assert that a class prefix appears exactly
once, and prove it by reverting the fix.
- The library must not compose user-visible English. `SearchField` built
`Clear ${label}`, which made adopting it an i18n regression for every
caller that had already translated its clear button. The first repair —
falling back to `label` — was worse: the input and its clear button
then shared an accessible name and `getByLabelText` matched both.
Reuse went from 22% to 75% (524 component uses against 179 remaining
native buttons). The remainder are elements that should not be
components: `role="tab"`, `menuitem`, `option`, `treeitem`, `gridcell`,
whole-row and whole-card click targets, drag handles, and the OS
titlebar.
Route required checks by changed surface, add offline provider and chat contracts, and keep fork PRs independent of live credentials. Layer agent guidance by subtree and enforce a compact instruction budget.
Tested: bun run check:policy
Confidence: high
Scope-risk: broad
