Compose from existing Imitations and Synthetics — importing named components here is expected and fine, unlike in Imitations.
Still carry data-rebar-component/data-rebar-part, forward data-*/aria-*, and style only through --rebar-* tokens.
If you're building a block instead of a component: add its shape to the Construct union in packages/placement/src/schema.ts, with a doc comment noting it's unmeasured until it's been through real repeated benchmarking (see the existing blocks' comments for the convention), plus a render case in BlockRenderer.tsx.
Do not give a Synthetic block a source or an on<Verb>-named field unless it is genuinely wired to live data or a handler inside that BlockRenderer.tsx case — packages/placement/src/opinions.ts mechanically promotes any block declaring one to Opinion, checked at compile time (tsc --noEmit fails if the tier table disagrees), so an unwired field name that merely looks live is a real bug, not a stylistic choice.
Write tests covering the rendered DOM output, and — for a block — that DOM order matches visual order.
Contribute it
Open an issue first for anything bigger than a small fix — the placement layer's shape is deliberate, and a quick check avoids building something that's already been tried and rejected (see ref/PLAN.md/ref/ASSESSMENT.md). No write access to this repo is required to start: fork it, build the construct there, then open an issue linking your fork or branch asking for it to be adopted into the main project.
Once you're building a component:
Add it under packages/core/src/components/Name.tsx, export it from packages/core/src/index.ts, and add its filename to apps/docs/scripts/generate-props.mjs's scan list.
Classify it "synthetic" in apps/docs/src/data/constructTier.ts's CONSTRUCT_TIER.component map.
Add a reference page under apps/docs/src/app/synthetics/<kebab-name>/page.tsx with a real, live-rendered example.
For a block instead:
Add the shape to Construct in packages/placement/src/schema.ts and a render case in BlockRenderer.tsx.
Classify its type "synthetic" in apps/docs/src/data/constructTier.ts's CONSTRUCT_TIER.block map — this is checked against the schema at compile time, so a missing entry fails tsc --noEmit immediately.
Update the block table in packages/placement's own README.md.
Add a reference page under its tier route with a real live example (apps/docs/src/app/synthetics/<block-type>/page.tsx).
Run pnpm run lint, test, build, and typecheck at the repo root before opening the PR — the same four checks CI runs, in that order.
