[BUG] [Windows] Claude Code crashes with segfault after ~9 min — canary Bun embedded in auto-updated claude.exe

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code crashes after ~9 minutes with a segmentation fault originating from Bun v1.3.9-canary.62, which is bundled inside the auto-updated claude.exe — not the system-level Bun installation.

Important: Setting release_channel = "stable" in .bunfig.toml does not prevent this crash. That config only governs the system-level Bun CLI. It has no effect on the Bun runtime embedded in claude.exe itself. Users cannot self-protect through .bunfig.toml.

What Should Happen?

Claude Code should remain stable indefinitely. If auto-updates are enabled, they should only pull builds containing a stable (non-canary) embedded Bun runtime.

Error Messages/Logs

panic(main thread): Segmentation fault at address 0x18


**Resource state at crash:**
- Elapsed: 523 seconds (~9 min)
- RAM: 0.75 GB (peak: 0.76 GB)
- Total committed: 1.03 GB
- Page faults: 827,052 (critically high — indicates memory thrashing)

**Additional MCP error contributing to instability (secondary):**

JSON Parse error: Single quotes (') are not allowed in JSON  [repeated 150+ times]
JSON Parse error: Expected ']'
JSON Parse error: Unexpected identifier "toolName"

These came from n8n MCP v2.30.2 (known bug, separate issue) and contributed to cascade failures.

Steps to Reproduce

1. Allow Claude Code to auto-update on Windows (auto-updater pulls canary Bun)
2. Start a session with MCP servers configured
3. Run the session for 9–15 minutes

Result: panic(main thread): Segmentation fault at address 0x18

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Prior to the auto-update that bundled Bun v1.3.9-canary.62

Claude Code Version

2.1.x

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

System Information

• Claude Code version at crash: 2.1.x (auto-updated; current stable is 2.1.45, no canary detected)
• Embedded Bun version at crash: v1.3.9-canary.62
• Last working version: Prior to the auto-update that bundled Bun v1.3.9-canary.62
• OS: Windows 11 Home, Build 26100
• RAM: 14.88 GB
• Shell: bash (Claude Code embedded)
• API platform: Anthropic

Current Workaround

Added DISABLE_AUTOUPDATER=1 to ~/.claude/settings.json to prevent further auto-updates from pulling canary builds. This is temporary — the permanent fix requires pinning the embedded runtime to stable Bun releases in the build pipeline.

Additional Context

0x18 is a near-null pointer dereference, consistent with a use-after-free or uninitialized struct access in Bun's memory allocator — a known category of issue in canary/experimental Bun builds on Windows.

Request:

1. Pin the embedded Bun runtime to stable releases in the claude.exe build pipeline
2. Clarify in docs that .bunfig.toml does not govern the embedded runtime (to prevent user confusion)
3. Communicate in release notes when a stable embedded Bun version ships, so users with DISABLE_AUTOUPDATER=1 know it's safe to re-enable