Issue Review: cloudflare/workers-sdk#7555

Summary

Non-deterministic deploy failures with "no registered event handlers" error when using Workers + Static Assets - reporter self-resolved by using dynamic imports.

Findings

• Created: 2024-12-15
• Updated: 2025-10-30
• Version: 3.95.0 → 4.60.0 (major version upgrade)
• Component: Wrangler, Workers + Assets
• Labels: bug, api, Workers + Assets
• Comments: 3

Key Evidence

1. Reporter self-resolved the issue: The reporter stated they "resolved the issue by moving two packages (braintrust, @babel/core) to be lazily imported (via dynamic imports)."

2. Maintainer explanation: @petebacondarwin clarified this was NOT a race condition with asset uploads. The error The uploaded script has no registered event handlers. [code: 10068] indicates the Worker code itself doesn't have a valid event handler exported. He suggested checking that the Worker has a proper default export with a fetch() handler.

3. Root cause identified by reporter: The reporter hypothesized "there was some sort of non-determinism between the event handler existence check and module initialization side-effects" - the issue was in their own code's top-level imports causing problems, not a bug in Wrangler.

4. No PR fixes this issue: No merged PRs reference issue #7555, and the issue is not mentioned in the changelog.

5. Significant version gap: The issue was reported against wrangler 3.95.0, and the current version is 4.60.0 (major version change with many potential improvements).

Recommendation

Status: CLOSE

Reasoning: This issue was self-resolved by the reporter. The root cause was identified as problematic top-level imports in their Worker code (packages with side effects that interfered with event handler detection), not a bug in Wrangler. The maintainer's explanation confirmed this was user code issue, not an assets upload race condition.

Action: Close with comment acknowledging the resolution and thanking the reporter for following up.

Suggested Comment

Thanks for the follow-up @sleexyz! Since you resolved this by moving to dynamic imports, it sounds like the issue was related to how those packages' top-level side effects interacted with the Worker's event handler registration, rather than a bug in Wrangler's asset upload flow.

As @petebacondarwin noted, the error [code: 10068] indicates the runtime couldn't find registered event handlers in your Worker - using dynamic imports was the right fix to avoid those packages' initialization code from interfering.

I'm going to close this issue as resolved. If anyone else encounters similar non-deterministic deploy failures, try moving heavy dependencies with side effects to dynamic imports.