Capture exception message in browser telemetry

[archandatta]

Summary

Runtime.exceptionThrown telemetry events set console_error.data.text to CDP's generic "Uncaught" / "Uncaught (in promise)" prefix and dropped the actual error message. The message lives on the exception RemoteObject (exceptionDetails.exception), which was already parsed into the struct but never read — so consumers could see that an exception fired and where (line/column/source_url/stack), but not what it said. console.error() messages were unaffected.

Changes

• Add message to BrowserConsoleErrorEventData (openapi.yaml + regenerated oapi).
• Decode a minimal RemoteObject (description, value) and derive the message: first line of description (e.g. Error: boom) → thrown value for non-Error throws → fall back to the generic text. The full stack stays in stack_trace, so message is just the name+message line.
• message is present only on exceptionThrown-sourced events; text is left unchanged so the uncaught-vs-in-promise signal is preserved.
• Unit tests for the derivation (Error, primitive throws, fallbacks).

Test plan

• go build ./...
• go test ./lib/cdpmonitor/ -run TestExceptionMessage
• e2e: assert an injected throw new Error("...") yields console_error.data.message containing the message (needs Docker + image)
• Verify the field propagates through the public API / SDK telemetry path (kernel/kernel) — additive/back-compat; add there if it re-serializes through a typed schema

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Note

Low Risk
Additive optional telemetry field with localized parsing logic and tests; no auth or breaking API changes.

Overview
Runtime.exceptionThrown console_error events previously exposed only CDP’s generic text ("Uncaught" / "Uncaught (in promise)"), so consumers could not see the real error text. This PR adds an optional message on BrowserConsoleErrorEventData (OpenAPI + regenerated oapi) and fills it in the CDP monitor when handling exceptions.

exceptionMessage reads the exception RemoteObject: first line of description for Error throws, thrown primitives via value, Symbol/BigInt via unserializableValue, with fallbacks to the existing text. text is unchanged so uncaught vs in-promise signaling stays the same; full stacks remain in stack_trace. message is set only for exceptionThrown-sourced events, not console.error. Unit tests cover the derivation paths.

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Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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Leading newline yields empty message

Medium Severity

The exceptionMessage function returns an empty string when a CDP exception's description begins with a newline. This occurs because the first-line extraction logic misinterprets a leading newline, resulting in a blank message field in telemetry despite the generic text fallback.

 

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