[BUG] Claude Code VS Code crashes on Windows ARM64: Bun incorrect alignment panic + exit code 3

Summary

Claude Code VS Code extension on Windows ARM64 crashes repeatedly during normal startup/replay of conversation. Process exits with code 3, with Bun panic incorrect alignment in logs. This appears to be a runtime-layer issue of built-in Bun, not user code.

Environment

• OS: Microsoft Windows 11 Professional
• OS version: 10.0.26200.0 (Windows 11)
• Architecture: ARM64 (ARMv8 64-bit)
• VS Code: 1.109.5 (commit 072586267e68ece9a47aa43f8c108e0dcbf44622)
• Claude Code VS Code extension: anthropic.claude-code@2.1.49 (win32-arm64)
• Installed CLI package: @anthropic-ai/claude-code@2.1.49
• Node: v24.13.0
• npm: 11.6.2
• claude --version: 2.1.49 (Claude Code)
• node.exe in PATH via AppData Local Programs
• VS Code setting: claudeCode.useTerminal: false, claudeCode.preferredLocation: panel
• RAM: 16.0 GB total, crash seen around 0.44-0.51GB RSS for the Bun process.

Reproduction Steps

1. Open Claude Code in VS Code extension (default native UI path)
2. Start conversation / normal operations
3. After a short time, the Claude process exits with code 3
4. UI logs show Bun panic lines and process closes
5. Reopening/retrying can reproduce similar crash pattern

Expected Result

Claude Code process should stay running and keep conversation session alive.

Actual Result

Extension reports:

• Error: Claude Code process exited with code 3
• Logs repeatedly contain Bun crash output:
• panic(thread XXXX): incorrect alignment
• oh no: Bun has crashed. This indicates a bug in Bun, not your code.
• No user-level fix available in extension settings to avoid this in default path on ARM64 in this build.

Evidence (from logs)

Log files:

• C:\Users\OseasyVM\AppData\Roaming\Code\logs\20260220T144158\window1\exthost\Anthropic.claude-code\Claude VSCode.log
• C:\Users\OseasyVM\AppData\Roaming\Code\logs\20260220T142657\window1\exthost\Anthropic.claude-code\Claude VSCode.log

Key excerpts:

Bun v1.3.10 (1423d3c8) Windows arm64
Args: c:\Users\OseasyVM\.vscode\extensions\anthropic.claude-code-2.1.49-win32-arm64\resources\native-binary\claude.exe ...
Elapsed: 85024ms ... RSS: 0.46GB | Peak: 0.48GB
panic(thread 1300): incorrect alignment
oh no: Bun has crashed. This indicates a bug in Bun, not your code.
...
Error from Claude (on channel ...): Error: Claude Code process exited with code 3

Bun v1.3.10 ... panic(thread 9820): incorrect alignment
...
Error from Claude (on channel ...): Error: Claude Code process exited with code 3

This included Bun self-generated report links, e.g.

• https://bun.report/1.3.10/W_11423d3c...

Additional Notes

• In this environment this happens consistently enough to block work.
• As an immediate workaround I had to switch toward terminal/external CLI usage.
• This appears to be ARM64 compatibility issue with bundled Bun runtime in this extension version.