fix(start-plugin-core): write prerendered binary responses as bytes by mixelburg · Pull Request #8752 · TanStack/router

mixelburg · 2026-10-17T22:17:40Z

🎯 Changes

Prerendering read every response with res.text(), so a server route that answers with an image (or any other binary payload) was decoded as UTF-8 before being written and the prerendered file came out corrupted (#8746).

Non-HTML responses are now read with res.arrayBuffer() and written unchanged; HTML responses keep going through text() and everything else in the pipeline (link crawling, onSuccess) is unchanged for them.

tests/prerender-response-body.test.ts covers both paths: a JPEG body round-trips byte-for-byte, an HTML page is still written as a string.

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Summary by CodeRabbit

Bug Fixes
- Prerendered non-HTML responses now preserve their original bytes, preventing corruption of binary files. HTML responses continue to be written as text, and content type matching is case-insensitive.

changeset-bot · 2026-10-17T22:17:45Z

🦋 Changeset detected

Latest commit: 3f06fc6

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

This PR includes changesets to release 5 packages

Name	Type
@tanstack/start-plugin-core	Patch
@tanstack/react-start-rsc	Patch
@tanstack/react-start	Patch
@tanstack/solid-start	Patch
@tanstack/vue-start	Patch

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coderabbitai · 2026-10-17T22:18:32Z

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📒 Files selected for processing: 2

packages/start-plugin-core/src/prerender.ts
packages/start-plugin-core/tests/prerender-response-body.test.ts

🚧 Files skipped from review as they are similar to previous changes: 2

packages/start-plugin-core/tests/prerender-response-body.test.ts
packages/start-plugin-core/src/prerender.ts

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📝 Walkthrough

Prerendering now reads HTML responses as text and non-HTML responses as bytes. It writes binary bodies without text decoding. Tests cover JPEG byte preservation and standard and case-insensitive HTML content types.

Changes: Prerendered response bodies

Layer / File(s)	Summary
Read and write response bodies `packages/start-plugin-core/src/prerender.ts`, `packages/start-plugin-core/tests/prerender-response-body.test.ts`, `.changeset/prerender-binary-responses.md`	HTML response bodies remain strings. Other response bodies are read as bytes and written without text decoding. `onSuccess` and link crawling receive an empty string for binary responses. Tests check JPEG bytes and HTML output. The changeset records the patch.

Priority: ⬇️ Low

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

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: schiller-manuel

Merge Risk: ⚪ Minimal · up to 3f06f

No outstanding issue identified that should prevent merging after normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		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 4 functions across 2 files.	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 change: writing prerendered binary responses as bytes.
Description check		The description includes the required Changes, Checklist, and Release Impact sections. It explains the corruption issue, the implementation, test coverage, AI assistance, and changeset status.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Inline comments:
Review comments at @packages/start-plugin-core/src/prerender.ts:
- Line 195: Normalize contentType to a consistent case before both HTML
media-type checks in the prerender response handling, so values such as
TEXT/HTML follow the HTML response path and preserve the received content for
onSuccess and link crawling.

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.changeset/prerender-binary-responses.md
packages/start-plugin-core/src/prerender.ts
packages/start-plugin-core/tests/prerender-response-body.test.ts

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Content-Type media types are case-insensitive (RFC 9110), so a response declaring 'TEXT/HTML' was written through the binary branch and handed an empty string to onSuccess and link crawling. Normalize the header once and cover it with a test.

fix(start-plugin-core): write prerendered binary responses as bytes

3c48d1a

coderabbitai Bot reviewed Oct 17, 2026

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Comment thread packages/start-plugin-core/src/prerender.ts

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fix(start-plugin-core): write prerendered binary responses as bytes - #8752

fix(start-plugin-core): write prerendered binary responses as bytes#8752
mixelburg wants to merge 2 commits into
TanStack:mainfrom
mixelburg:fix/prerender-binary-server-routes

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