Keep the SDK root out of the frontend bundle

[trotterdylan]

The plugin reached the server image but its frontend bundle would not build, so the install failed and it never appeared in the plugin list:

frontend bundle build for "thread-briefs" failed:
  contract.ts:1:34: ERROR: Could not resolve "@get-bb/plugin-sdk"

app.tsx imported two constants (BRIEFS_CHANGED_CHANNEL, BRIEF_STAGES) from contract.ts, which imports defineRpcContract from the SDK root. That put the SDK into the app bundle's dependency graph — and the server builds that bundle against a production install where the SDK, a devDependency, has been pruned. Only @get-bb/plugin-sdk/app is shimmed for the frontend; the root never is.

Every local check passed because a dev install has the SDK on disk. That is the whole trap.

Fix

shared.ts holds the runtime values the frontend needs and imports nothing at all. app.tsx takes those from there, and its contract.ts import is now type-only so it erases completely. contract.ts builds its zod enum from shared.ts's list, so the stages keep one definition rather than two that can drift.

Verified the way the image does it — prune dev dependencies, then build:

npm ci --omit=dev --legacy-peer-deps   # SDK absent, as in the image
bb plugin build                        # succeeds

and dist/app.meta.json carries neither the SDK nor zod. (Keeping zod out shrinks the bundle too; it is not shimmed and would otherwise be bundled from node_modules.)

Regression guard

bundle.test.ts encodes the invariant: no runtime import of the SDK root, zod, or contract.ts anywhere in the frontend graph, plus shared.ts importing nothing. I checked it earns its keep by reintroducing the original bug — it fails — and it caught one bug in itself along the way (the word "import" inside a comment anchoring a runaway match).

This is the third independent thing standing between a bb.app plugin and this image, after NODE_PATH and plugin-directory ownership. The first two were image problems; this one was mine.

🤖 Generated with Claude Code