Fix crash when calling text() on consumed ReadableStream body

[robobun]

What: ByteBlobLoader.toBufferedValue returned .zero (null JSValue) without throwing a JS exception when the blob store had already been detached, violating the host function contract and triggering an assertion failure.

How to reproduce:

const resp = new Response("Hello");
const body = resp.body;
resp.bytes();
body.text(); // crash: "Expected an exception to be thrown"

When Response.bytes() is called, it detaches the underlying blob store from the ByteBlobLoader. A subsequent body.text() call on the already-obtained ReadableStream reference reaches toBufferedValue where toAnyBlob() returns null. The function then returned .zero — but the toJSHostCall wrapper asserts that .zero means a JS exception was set, which it wasn't.

Fix: Throw a proper JS error ("Body already consumed") instead of returning .zero, matching the pattern used by ByteStream.toBufferedValue for similar error cases.

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Crash fingerprint: 8528c32f3d75dc9f

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[robobun]

^{Updated 1:27 AM PT - Apr 1st, 2026}

❌ @autofix-ci[bot], your commit 3eca4ae has 4 failures in Build #43083 (All Failures):

• test/js/bun/s3/s3.test.ts - code 1 on 🍎 14 x64
• test/js/bun/webview/webview.test.ts - timeout on 🍎 13 aarch64
• test/js/bun/webview/webview.test.ts - timeout on 🍎 14 aarch64
• test/js/bun/webview/webview.test.ts - timeout on 🍎 13 x64
• test/js/third_party/@azure/service-bus/azure-service-bus.test.ts - SIGILL on 🐧 13 x64-asan
• test/js/bun/webview/webview-chrome.test.ts - code 1 on 🍎 13 aarch64

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[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 3ed4186 and 3eca4ae.

📒 Files selected for processing (2)

• src/bun.js/webcore/ByteBlobLoader.zig
• test/js/web/streams/body-already-consumed.test.ts

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Walkthrough

Modifies ByteBlobLoader.zig to throw a JavaScript error "Body already consumed" when attempting to access an already-consumed Response body, replacing previous behavior of returning an empty value. Adds a test verifying this error is thrown correctly.

Changes

Cohort / File(s)	Summary
Body Consumption Error Handling src/bun.js/webcore/ByteBlobLoader.zig	Modified toBufferedValue() to throw JavaScript error "Body already consumed" via explicit error path instead of returning .zero when body has been consumed.
Body Consumption Test test/js/web/streams/body-already-consumed.test.ts	New test verifying that calling body.text() on a consumed Response stream throws error with message "Body already consumed".

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely describes the main fix: preventing a crash when calling text() on a consumed ReadableStream body.
Description check	✅ Passed	The description covers both required template sections: clearly explains what the PR does (the bug and fix) and how to reproduce/verify the issue with a concrete code example.

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