[sarankumar1325]

🎯 Changes

Fixes #8792.

When a child loader throws and the child has no errorComponent (and there is no defaultErrorComponent), the error renders through the nearest ancestor's errorComponent. reduceLane only loaded the failing match's own errorComponent chunk, so with a code-split ancestor boundary router.load() resolved before that chunk was ready and the first render was empty.

After loading the failing match's chunk, the lane now walks up to the first route whose errorComponent ?? defaultErrorComponent is set and loads that route's errorComponent chunk before committing. If the failing route (or the default) already provides one, nothing extra is loaded.

Tests in boundary-component-chunk.test.ts: load() stays pending until the ancestor's errorComponent preload resolves (fails on main), and the ancestor chunk is not requested when a defaultErrorComponent catches the error at the child.

Disclosure: written with AI assistance; I reviewed the change and ran the tests below.

✅ 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, including any code generated with AI assistance.

Tested: router-core test:unit (3653 passed), test:eslint, test:types; react-router, solid-router and vue-router test:unit pass.

🚀 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
  • Child loader errors now wait for the nearest ancestor’s error screen to load before routing completes, so the correct error screen is available when the error is displayed.
  • When a child or router-level default error screen is configured, the ancestor error screen is not loaded unnecessarily.

[changeset-bot]

🦋 Changeset detected

Latest commit: f6c99d9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 23 packages

Name	Type
@tanstack/router-core	Patch
@tanstack/react-router	Patch
@tanstack/react-start-client	Patch
@tanstack/react-start-rsc	Patch
@tanstack/react-start-server	Patch
@tanstack/router-generator	Patch
@tanstack/router-plugin	Patch
@tanstack/solid-router	Patch
@tanstack/solid-start-client	Patch
@tanstack/solid-start-server	Patch
@tanstack/start-client-core	Patch
@tanstack/start-plugin-core	Patch
@tanstack/start-server-core	Patch
@tanstack/start-storage-context	Patch
@tanstack/vue-router	Patch
@tanstack/vue-start-client	Patch
@tanstack/vue-start-server	Patch
@tanstack/react-start	Patch
@tanstack/router-cli	Patch
@tanstack/router-vite-plugin	Patch
@tanstack/solid-start	Patch
@tanstack/start-static-server-functions	Patch
@tanstack/vue-start	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	⚠️ Failed 2026-10-23T03:38:54.191666Z We couldn’t complete this review. Comment @codex review to try again.	f6c99d9	PR opened

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ℹ️ Recent review info

⚙️ Run configuration

• Source mode: Auto
• Repository: TanStack/router
• Branch: main
• File: .coderabbit.yaml
• Commit: 6b9fe6d
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Advanced
• Run ID: 981723fd-1ba1-42b2-886b-e1b1ab971587

📥 Commits

Reviewing files that changed from the base of the PR and between 6b9fe6d and f6c99d9.

📒 Files selected for processing: 3

• .changeset/ancestor-error-boundary-chunk.md
• packages/router-core/src/load-client.ts
• packages/router-core/tests/boundary-component-chunk.test.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

📝 Walkthrough

When a child loader fails without a child or router default error component, the router loads the nearest ancestor’s error-component chunk before router.load() completes. Tests cover pending preloads and the router default case.

Changes: Ancestor error boundary loading

Layer / File(s)	Summary
Load ancestor error boundary chunks packages/router-core/src/load-client.ts, packages/router-core/tests/boundary-component-chunk.test.ts, .changeset/ancestor-error-boundary-chunk.md	Error handling loads the nearest ancestor’s error-component chunk when the failed route has no error component and the router has no default. Tests verify that router.load() waits for the preload and that a router default prevents the ancestor preload. The changeset declares a patch for @tanstack/router-core.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: sheraff

Merge Risk: ⚪ Minimal · up to f6c99

The ancestor error-boundary loading change is ready to merge after normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main fix: loading the ancestor errorComponent chunk for child errors.
Description check		The description explains the change, motivation, tests, AI assistance, release impact, and changeset. The checklist leaves the code-understanding item unchecked, but the author states that they review…
Linked Issues check		Issue #8792 requires router.load() to wait for the code-split ancestor errorComponent that renders a child loader error. reduceLane now loads the failing match chunk and then calls `loadAncestor…
Out of Scope Changes check		The changes stay within issue #8792. The source change implements ancestor boundary preloading. The tests cover the reported regression and the default-boundary case. The changeset documents the publi…

Full details: Description check

Explanation

The description explains the change, motivation, tests, AI assistance, release impact, and changeset. The checklist leaves the code-understanding item unchecked, but the author states that they reviewed the change, so the description is mostly complete.

Full details: Linked Issues check

Explanation

Issue #8792 requires router.load() to wait for the code-split ancestor errorComponent that renders a child loader error. reduceLane now loads the failing match chunk and then calls loadAncestorErrorComponent before the lane commits. The helper finds the nearest applicable ancestor and waits for its errorComponent preload. It skips the ancestor when the failed route or defaultErrorComponent already provides the boundary. The added tests cover both behaviors.

Full details: Out of Scope Changes check

Explanation

The changes stay within issue #8792. The source change implements ancestor boundary preloading. The tests cover the reported regression and the default-boundary case. The changeset documents the published behavior change.

Full details: Docstring Coverage

Explanation

Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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