fix: improve error logging in worker and update defaultLayer evaluation closes #20413

[arafays]

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Running opencode with --conditions=browser shows a blank screen, freezes completely, Ctrl+C doesn't work, terminal must be killed. The error log only shows [object ErrorEvent].

• thread.ts — worker.onerror passed raw ErrorEvent to logger. Used existing errorMessage utility instead.
• agent.ts — defaultLayer eagerly accessed Provider.defaultLayer at module load time, which is undefined under --conditions=browser. Wrapped with Effect.sync + Layer.unwrap following the pattern in src/session/compaction.ts:382-394.

How did you verify your code works?

Before: blank screen, Ctrl+C unresponsive. After: launches cleanly. Ran bun run typecheck and bun run dev.

Screenshots / recordings

Not applied

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

Issue for this PR

Closes #20413

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found one potentially related PR:

PR #12809: fix(opencode): expand Error properties in logs for better diagnostics

• fix(opencode): expand Error properties in logs for better diagnostics #12809
• This PR also addresses error logging improvements, which relates to the worker error logging changes in PR fix: improve error logging in worker and update defaultLayer evaluation closes #20413 #20413. However, it appears to be focused on expanding Error properties in logs, which may be related to the ErrorEvent serialization issue being fixed.

All other searches either returned only the current PR (#20413) or no results, suggesting there are no other open PRs addressing the same issues (worker error logging with ErrorEvent, defaultLayer deferred evaluation for --conditions=browser, or the blank screen problem).

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[arafays]

this pr closes #20413 i dont know why the label is not removed I have tried to edit multiple times