fix(browser): forward uncaught worker errors with their stack - #24210
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d2anamaria wants to merge 2 commits into
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fix(browser): forward uncaught worker errors with their stack#24210d2anamaria wants to merge 2 commits into
d2anamaria wants to merge 2 commits into
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- Add an `error` listener in `registerWebWorker` that posts `event.error` (falling back to `event.message`) over the existing `_sentryWorkerError` channel - Add optional `kind` discriminator to `SerializedWorkerError`; a missing `kind` means rejection, so workers registered by an older SDK keep working - Rename `handleForwardedWorkerRejection` to `handleForwardedWorkerError` and branch on `kind` for both the mechanism and `eventFromUnknownInput`'s `isUnhandledRejection` argument - Report forwarded throws under the `auto.browser.web_worker.onerror` mechanism - Restrict `_eventFromRejectionWithPrimitive` to rejections so a thrown primitive is not labelled "Non-Error promise rejection" - Set `Error.stackTraceLimit = 50` in the worker, matching globalHandlersIntegration, since V8's default of 10 truncates stacks before they are forwarded - Wrap the forwarding `postMessage` so a non-cloneable reason is described instead of raising DataCloneError out of the worker's error handler - Correct the doc comment claiming globalHandlers already captures sync worker errors
d2anamaria
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andreiborza,
logaretm and
msonnb
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September 8, 2026 14:45
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Uncaught errors thrown inside a web worker reach Sentry without a usable stack.
They bubble to the page, so an event is still created, but the propagated
ErrorEventcarries no error object — only a message string. The result is anevent with a single synthetic frame pointing at the worker bundle and a value
prefixed with
Uncaught.For plain JavaScript that degrades acceptably: one frame plus a sourcemap still
locates the throw. For WebAssembly it fails outright. No frame carries a wasm
URL, so the wasm integration finds nothing to match and the event ships with no
debug images, even though the worker's images already reached the page. An
uncaught wasm trap in a worker is unsymbolicatable today, while the identical
trap wrapped in try/catch symbolicates fine.
Root cause
registerWebWorkeronly forwarded unhandled rejections, on the assumption thatsynchronous errors were already covered by the global handlers. They are
captured, but only from the message string, because an error that crosses a
worker boundary loses its error object by design.
Solution
Uncaught worker errors are now forwarded to the page over the same channel that
already carries rejections. Structured clone preserves
message,stackandcause, so the page receives a real error and parses a real stack — the sameoutcome the caught path already produced. Wasm frames then match their debug
images and symbolicate normally. Forwarded errors are distinguishable from
rejections by their mechanism, and the worker's stack trace limit now matches
the page's so deep stacks are no longer truncated before being sent.
Limitations
The error still bubbles to the page after being forwarded, so a second,
frameless event is emitted for the same throw. Deduplication does not merge the
two, because one has a stack and the other does not. Cancelling the error inside
the worker would collapse them, but would also stop the browser printing its own
uncaught report in DevTools — a real debugging regression. This is left open
deliberately and is the main thing worth a second opinion.
Errors whose value cannot be structured-cloned are forwarded as a description
rather than the original value.
Workers registered by an older SDK version are still treated as rejection-only,
so mixed-version setups keep working.