[keegandonley]

Protect against exceptions, parse errors, and timeouts.

Jira: https://kizen.atlassian.net/browse/KZN-18921

[Copilot]

🟡 Changes recommended

Error handling still permits sensitive diagnostic exposure, and nullable failures conflict with public return types and field visibility behavior.

3 open issues

• Align expression failure policy with callers and return types · New
• Cancel worker error events after sanitized handling · New
• Read error name once for validation and reporting · New

What changed in this PR

This PR hardens expression evaluation by handling worker failures and bounding execution time while preserving diagnostic details in debug mode.

Changes:

• Extracts evaluation logic and returns structured errors for parsing, evaluation, and serialization failures.
• Adds a 20-second timeout, worker cleanup, and host-side error handling.
• Adds tests for failure handling, diagnostics, and worker lifecycle behavior.

File	Description
src/​workers/​expression.worker.ts	Delegates messages to the response builder.
src/​workers/​expression.ts	Adds guarded evaluation and error categorization.
src/​workers/​expression.test.ts	Tests evaluation, invalid inputs, serialization, and diagnostics.
src/​run.ts	Adds timeouts, cleanup, and failure handling.
src/​run.test.ts	Tests worker lifecycle and host-side failure behavior.

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

Static review identified no new blocking defects, and the added tests cover the principal failure and cleanup paths.

No open issues 🎉

3 resolved since last review

• Read error name once for validation and reporting
• Cancel worker error events after sanitized handling
• Align expression failure policy with callers and return types

_{Review effort: Balanced}

[mauricebecnel400]

LGTM