fix(start): prebundle client RPC dependencies

[tannerlinsley]

🎯 Changes

Prebundle the client RPC dependencies that Start's transforms introduce after Vite's initial scan. A clean first visit to the Form example discovered these dependencies during rendering, reoptimized them, and loaded different React module instances. The page logged invalid-hook-call errors before recovering through a reload.

Add the existing serialization and cookie dependencies to the client optimizer using their framework-owned dependency paths. Server optimization and production bundling are unchanged. No example-specific override is needed.

The companion regression in #8376 forces a cold dependency scan and fails on hook errors logged through React's boundary. It fails against the original framework and passes with this change. That PR must include this fix before merging.

Validation:

• Cold Form browser regression: baseline 1 failed / 1 passed; fixed 2 passed.
• Three fresh browser contexts: no console or page errors after the fix, and no mid-render dependency reoptimization.
• Production build/types and both production browser tests pass.
• All 3 production public assets are byte-for-byte identical, totaling 378,948 bytes before and after.
• Dependency paths resolve for React, Solid, and Vue. Browser reproduction is React, not a claim of full Solid/Vue browser coverage.
• Required repository lint, types and unit checks pass.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested code changes locally with the relevant test commands, or tests do not apply to this pull request.
• I fully understand the code in this pull request.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

• Bug Fixes
  • Improved client startup reliability by pre-bundling required serialization dependencies before the first render.
  • Prevented page reloads caused by mixed React module instances when dependencies are discovered late.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Plan: Advanced

Run ID: db9ffe8a-f03a-4ae2-8281-074fdbc6e319

📥 Commits

Reviewing files that changed from the base of the PR and between 6365b67 and 9763973.

📒 Files selected for processing (1)

• .changeset/quiet-clients-scan.md

🚧 Files skipped from review as they are similar to previous changes (1)

• .changeset/quiet-clients-scan.md

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---

📝 Walkthrough

Walkthrough

The client Vite environment now prebundles cookie-es, seroval, and seroval-plugins/web through the TanStack Start client dependency chain. A patch changeset documents the update.

Changes

Client dependency optimization

Layer / File(s)	Summary
Prebundle RPC dependencies packages/start-plugin-core/src/vite/planning.ts, .changeset/quiet-clients-scan.md	The client dependency plan includes cookie-es, seroval, and seroval-plugins/web. The changeset declares a patch release for @tanstack/start-plugin-core.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 97639

The supplied change introduces no verified merge-blocking risk.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description explains the change, motivation, validation results, release impact, and checklist status. It includes the required changeset and testing information.
Title check	✅ Passed	The title is concise and accurately identifies the primary change: prebundling client RPC dependencies.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (1 skipped: 1 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch taren/start-cold-dependencies

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[github-actions]

🚀 Changeset Version Preview

4 package(s) bumped directly, 20 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
@tanstack/history	1.162.3 → 1.162.4	Changeset
@tanstack/router-core	1.171.29 → 1.171.30	Changeset
@tanstack/start-plugin-core	1.171.42 → 1.171.43	Changeset
@tanstack/start-server-core	1.169.34 → 1.169.35	Changeset
@tanstack/react-router	1.170.35 → 1.170.36	Dependent
@tanstack/react-start	1.168.52 → 1.168.53	Dependent
@tanstack/react-start-client	1.168.33 → 1.168.34	Dependent
@tanstack/react-start-rsc	0.1.51 → 0.1.52	Dependent
@tanstack/react-start-server	1.167.40 → 1.167.41	Dependent
@tanstack/router-cli	1.167.35 → 1.167.36	Dependent
@tanstack/router-generator	1.167.35 → 1.167.36	Dependent
@tanstack/router-plugin	1.168.37 → 1.168.38	Dependent
@tanstack/router-vite-plugin	1.167.37 → 1.167.38	Dependent
@tanstack/solid-router	1.170.33 → 1.170.34	Dependent
@tanstack/solid-start	1.168.50 → 1.168.51	Dependent
@tanstack/solid-start-client	1.168.32 → 1.168.33	Dependent
@tanstack/solid-start-server	1.167.39 → 1.167.40	Dependent
@tanstack/start-client-core	1.170.29 → 1.170.30	Dependent
@tanstack/start-static-server-functions	1.167.34 → 1.167.35	Dependent
@tanstack/start-storage-context	1.167.31 → 1.167.32	Dependent
@tanstack/vue-router	1.170.32 → 1.170.33	Dependent
@tanstack/vue-start	1.168.49 → 1.168.50	Dependent
@tanstack/vue-start-client	1.167.35 → 1.167.36	Dependent
@tanstack/vue-start-server	1.167.39 → 1.167.40	Dependent

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 9763973

Command	Status	Duration	Result
nx affected --targets=test:eslint,test:unit,tes...	✅ Succeeded	17m 55s	View ↗
nx run-many --target=build --exclude=examples/*...	✅ Succeeded	43s	View ↗

---

☁️ Nx Cloud last updated this comment at 2026-09-12 00:22:04 UTC

[github-actions]

Bundle Size Benchmarks

This pull request does not affect bundle size in any measured scenario.

[pkg-pr-new]

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commit: 9763973

[codspeed-hq]

Merging this PR will not alter performance

✅ 180 untouched benchmarks

---

_{Comparing taren/start-cold-dependencies (9763973) with main (dbf0bd9)¹}

Footnotes

1. No successful run was found on main (05422da) during the generation of this report, so dbf0bd9 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩