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## Summary
Fixes 100% CPU usage on idle WebSocket servers between bun-v1.2.23 and
bun-v1.3.0.
Many users reported WebSocket server CPU usage jumping to 100% on idle
connections after upgrading to v1.3.0. Investigation revealed a missing
`poll_ref.unref()` call in the WebSocket upgrade path.
## Root Cause
In commit 625e537f5d (#23348), the `OnBeforeOpen` callback mechanism was
removed as part of refactoring the WebSocket upgrade process. However,
this callback contained a critical cleanup step:
```zig
defer ctx.this.poll_ref.unref(ctx.globalObject.bunVM());
```
When a `NodeHTTPResponse` is created, `poll_ref.ref()` is called (line
314) to keep the event loop alive while handling the HTTP request. After
a WebSocket upgrade, the HTTP response object is no longer relevant and
its `poll_ref` must be unref'd to indicate the request processing is
complete.
Without this unref, the event loop maintains an active reference even
after the upgrade completes, causing the CPU to spin at 100% waiting for
events on what should be an idle connection.
## Changes
- Added `poll_ref.unref()` call in `NodeHTTPResponse.upgrade()` after
setting the `upgraded` flag
- Added regression test to verify event loop properly exits after
WebSocket upgrade
## Test Plan
- [x] Code compiles successfully
- [x] Existing WebSocket tests pass
- [x] Manual testing confirms CPU usage returns to normal on idle
WebSocket connections
## Related Issues
Fixes issue reported by users between bun-v1.2.23 and bun-v1.3.0
regarding 100% CPU usage on idle WebSocket servers.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>