[BUG] N-API addon lifecycle crash — same segfault on both Bun and Node.js runtimes #27356

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report
• I am using the latest version of Claude Code

What's Wrong?

Claude Code appears to crash through the same N-API code path on both Bun and Node.js runtimes. This suggests the root cause may be in Claude Code's native addon lifecycle rather than in Bun specifically.

Crash signatures across runtimes (from public issue data):

The shared fault sentinel (0xFFFFFFFFFFFFFFFF) across two different JS engines (JSC and V8) is notable. If confirmed, this would rule out a runtime-specific bug and point to Claude Code's native .node addon.

Hypothesis (not independently verified)

Based on dump analysis published in #21875 (27 full memory dumps analyzed via WinDbg by @balandari):

1. Main thread calls napi_remove_async_cleanup_hook — begins freeing async resources
2. Worker threads are simultaneously inside napi_unref_threadsafe_function — still using those resources
3. Cleanup frees/corrupts a function pointer while workers hold references -> ACCESS_VIOLATION

We have not independently reproduced this. This hypothesis is based on cross-referencing public crash data across issues. The dump analysis and cross-runtime findings were produced by @balandari in #21875.

Why this matters now

#21875 requested a Bun version bump as the fix. That happened (v1.3.5 -> v1.3.10). New crash reports on v1.3.10 with identical signatures suggest the bump was insufficient:

• [BUG] Segmentation fault in Bun v1.3.10 (Windows) during long sessions — pipe write crash #27320: 0xFFFFFFFFFFFFFFFF (same sentinel), Bun v1.3.10, 3.5 min session
• [BUG] Bun segfault crash after ~2h session on Windows x64 (Bun v1.3.10) #26984: 0x4B750B20520 (heap address), Bun v1.3.10, 2h session

If the root cause is in the addon's cleanup ordering rather than the runtime, version bumps alone won't resolve this.

What Should Happen?

Investigation into whether the native addon's threadsafe_function cleanup is properly synchronized with worker thread lifecycle.

Related Issues

• Repeated Bun v1.3.5 segfaults -- 78 crashes, root cause identified (Windows + WSL) #21875 — 78 crashes, 27 dumps, full root cause analysis (originally framed as Bun-specific)
• [BUG] Segmentation fault in Bun v1.3.10 (Windows) during long sessions — pipe write crash #27320 — Bun v1.3.10 still crashing, same signature
• [BUG] Bun segfault crash after ~2h session on Windows x64 (Bun v1.3.10) #26984 — Bun v1.3.10, 2h session crash
• [BUG] SyntaxError: Too many arguments (65535 limit) on restart after session crash - Node.js v22.22.0 #24874 — Node.js 65535 args limit crash after session crash at ~80% context
• SIGABRT crash: native .node addon deleted from /tmp during runtime (v2.1.42) #26057 — Native .node addon deleted from /tmp

Claude Code Version

2.1.50

Platform

Anthropic API

Operating System

Windows + WSL2 (cross-platform confirmed per #21875)