fix(react-start-rsc): avoid pulling the router entry into the RSC bundle via start-server-core barrel import

[FrancoKaddour]

Closes #7934

renderServerComponent and createCompositeComponent imported getRequest from the @tanstack/start-server-core root barrel. That barrel re-exports createStartHandler, which contains import('#tanstack-router-entry') / import('#tanstack-start-entry'). When either RSC helper enters the rsc environment graph (e.g. a server-fn file importing it — even unused, since @tanstack/react-start-rsc has no sideEffects: false), the dynamic router-entry import survives into the RSC build. Because the rsc environment gets the unpruned route tree, this emits a router-*.js chunk containing every route file — including server-only API routes and their heavy imports — duplicated from the SSR bundle (79 MB in the linked reproduction; exceeds Cloudflare Workers size limits).

Fix: import getRequest from the self-contained @tanstack/start-server-core/request-response subpath (the same subpath react-start/src/server.rsc.ts already re-exports for the RSC context), so createStartHandler and its router-entry dynamic import never enter the RSC module graph.

Verification

Verified against the issue reproduction (https://github.com/jeremy-code/tanstack-rsc-api-routes): a baseline build emits dist/server/rsc/assets/router-*.js at 76 MB (153 MB total dist). Applying this same two-import change to the installed @tanstack/react-start-rsc dist and rebuilding, the router chunk is no longer emitted and total dist drops to 78 MB. Unit tests (61) and the package build pass locally.

Summary by CodeRabbit

• Bug Fixes

  • Improved React Server Component bundle generation by preventing unnecessary server-route dependencies from being included.
  • Reduced the risk of duplicated dependencies in generated RSC bundles.

• Chores

  • Updated internal request handling imports without changing runtime behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 496a56be-0b3a-4489-a0b0-6002547c20f9

📥 Commits

Reviewing files that changed from the base of the PR and between 2cb221c and 0d54160.

📒 Files selected for processing (3)

• .changeset/fix-rsc-barrel-import-leak.md
• packages/react-start-rsc/src/createCompositeComponent.ts
• packages/react-start-rsc/src/renderServerComponent.ts

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📝 Walkthrough

Walkthrough

The RSC helper modules now import getRequest from @tanstack/start-server-core/request-response. A patch changeset documents the import-path correction for @tanstack/react-start-rsc.

Changes

RSC import isolation

Layer / File(s)	Summary
Request-response subpath imports packages/react-start-rsc/src/createCompositeComponent.ts, packages/react-start-rsc/src/renderServerComponent.ts, .changeset/fix-rsc-barrel-import-leak.md	Both RSC helpers use the dedicated request-response import path. The changeset records the patch release.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the import change and its purpose of preventing router code from entering the RSC bundle.
Linked Issues check	✅ Passed	The import changes directly address issue #7934 by preventing server-route dependencies from entering the RSC bundle.
Out of Scope Changes check	✅ Passed	The changeset and two import updates are limited to the linked issue's scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[FrancoKaddour]

Thanks @schiller-manuel — #7944 is the comprehensive version of this: same two-import change at the core, plus the focused server entrypoints, the emitted-build regression coverage and the eslint guard that this PR didn't have. Glad the analysis was useful, and nice touch keeping the boundary enforced going forward.