[BUG] Segmentation fault (exit code 3) on Windows 11 - Bun v1.3.6 crash at 0xCC/0xD0 during startup

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?

Description

Claude Code v2.1.15 consistently crashes with a segmentation fault during startup on Windows 11. The crash occurs every
time after "[STARTUP] Loading commands and agents..." with exit code 3.

Environment

• OS: Windows 11 (win11_ge)
• Claude Code Version: 2.1.15
• Bun Version: v1.3.6 (d530ed99) Windows x64 (baseline)
• CPU: x64 with sse42, avx, avx2
• VS Code: Running on Windows (not WSL)
• Node.js: v24.13.0 (installed in WSL2)
• Git Bash: Installed at C:\Program Files\Git\bin\bash.exe

Steps to Reproduce

1. Install Claude Code v2.1.15 extension in VS Code on Windows 11
2. Configure API key
3. Open any folder in VS Code
4. Launch Claude Code
5. Crash occurs immediately during startup

Expected Behavior

Claude Code should launch successfully and be ready for interaction.

Actual Behavior

The extension crashes with:
panic(thread XXXXX): Segmentation fault at address 0xCC
panic: Segmentation fault at address 0xD0
panicked during a panic. Aborting.

Process exits with code 3.

Error Log

2026-01-22 13:15:55.607 [info] Claude code extension is now active?
2026-01-22 13:15:55.607 [info] MCP Server running on port 59115 (localhost only)
2026-01-22 13:15:55.607 [info] AuthManager initialized
2026-01-22 13:15:56.426 [info] Received message from webview:
{"type":"request","requestId":"krcirqcubgg","request":{"type":"init"}}
2026-01-22 13:15:56.428 [info] Getting authentication status
2026-01-22 13:15:56.428 [info] API key found in config file
2026-01-22 13:15:56.428 [info] Auth status: method=api-key
2026-01-22 13:15:56.465 [info] Received message from webview:
{"type":"request","requestId":"zipti835luc","request":{"type":"rename_tab","title":"Claude
Code","hasPendingPermissions":false,"hasUnseenCompletion":false}}
2026-01-22 13:15:56.466 [info] Received message from webview:
{"type":"request","requestId":"zoptf772vzj","request":{"type":"get_claude_state"}}
2026-01-22 13:15:56.615 [info] Loading config cache by launching Claude...
2026-01-22 13:15:56.615 [info] Spawning Claude with SDK query function - cwd: c:\ate\UUT\TRA-100B\TRA-100B_UUT, permission
mode: default, version: 2.1.15,
c:\Users\abe82683\.vscode\extensions\anthropic.claude-code-2.1.15-win32-x64\resources\native-binary\claude.exe, resume:
undefined
2026-01-22 13:15:57.252 [info] From claude: 2026-01-22T19:15:57.232Z [DEBUG] [init] configureGlobalMTLS starting
2026-01-22T19:15:57.232Z [DEBUG] [init] configureGlobalMTLS complete
2026-01-22T19:15:57.233Z [DEBUG] [init] configureGlobalAgents starting
2026-01-22T19:15:57.233Z [DEBUG] [init] configureGlobalAgents complete

2026-01-22 13:15:57.425 [info] From claude: 2026-01-22T19:15:57.375Z [DEBUG] Using bash path: "C:\Program
Files\Git\bin\bash.exe"
2026-01-22T19:15:57.391Z [DEBUG] [STARTUP] Loading MCP configs...
2026-01-22T19:15:57.393Z [DEBUG] Found 0 plugins (0 enabled, 0 disabled)
2026-01-22T19:15:57.393Z [DEBUG] [claudeai-mcp] Checking gate (cached)...
2026-01-22T19:15:57.393Z [DEBUG] [claudeai-mcp] Gate returned: false
2026-01-22T19:15:57.393Z [DEBUG] [claudeai-mcp] Disabled via gate
2026-01-22T19:15:57.393Z [DEBUG] [STARTUP] MCP configs loaded in 2ms
2026-01-22T19:15:57.394Z [DEBUG] [ToolSearch:optimistic] mode=tst-auto, ENABLE_TOOL_SEARCH=undefined, result=true
2026-01-22T19:15:57.395Z [DEBUG] [ToolSearch:optimistic] mode=tst-auto, ENABLE_TOOL_SEARCH=undefined, result=true
2026-01-22T19:15:57.395Z [DEBUG] [STARTUP] Running setup()...
2026-01-22T19:15:57.416Z [DEBUG] Loading skills from: managed=C:\ProgramData\ClaudeCode\.claude\skills,
user=C:\Users\abe82683\.claude\skills, project=[]

2026-01-22 13:15:57.477 [info] From claude: 2026-01-22T19:15:57.465Z [DEBUG] installed_plugins.json doesn't exist,
returning empty V2 object

2026-01-22 13:15:57.879 [info] From claude: 2026-01-22T19:15:57.506Z [ERROR] Error: Error: ENOENT: no such file or
directory, scandir 'C:\Users\abe82683\.claude\skills'
at readdirSync (unknown)
at <anonymous> (B:/~BUN/root/claude.exe:12:1903)
at LX (B:/~BUN/root/claude.exe:11:34882)
at readdirSync (B:/~BUN/root/claude.exe:12:1864)
at WU$ (B:/~BUN/root/claude.exe:1480:380)
at WU$ (B:/~BUN/root/claude.exe:1480:1350)
at <anonymous> (B:/~BUN/root/claude.exe:1480:4483)
at <anonymous> (B:/~BUN/root/claude.exe:1480:5171)
at A (B:/~BUN/root/claude.exe:11:7245)
at lWE (B:/~BUN/root/claude.exe:4123:4342)
at async <anonymous> (B:/~BUN/root/claude.exe:5410:2332)
2026-01-22T19:15:57.506Z [DEBUG] Error log sink initialized
2026-01-22T19:15:57.515Z [DEBUG] Writing to temp file: C:\Users\abe82683\.claude\todos\fe9fea53-80f0-4e72-9d86-2106c803eb8f
-agent-fe9fea53-80f0-4e72-9d86-2106c803eb8f.json.tmp.74704.1769109357515
2026-01-22T19:15:57.519Z [DEBUG] Temp file written successfully, size: 2 bytes
2026-01-22T19:15:57.519Z [DEBUG] Renaming C:\Users\abe82683\.claude\todos\fe9fea53-80f0-4e72-9d86-2106c803eb8f-agent-fe9fea
53-80f0-4e72-9d86-2106c803eb8f.json.tmp.74704.1769109357515 to
C:\Users\abe82683\.claude\todos\fe9fea53-80f0-4e72-9d86-2106c803eb8f-agent-fe9fea53-80f0-4e72-9d86-2106c803eb8f.json
2026-01-22T19:15:57.522Z [DEBUG] File
C:\Users\abe82683\.claude\todos\fe9fea53-80f0-4e72-9d86-2106c803eb8f-agent-fe9fea53-80f0-4e72-9d86-2106c803eb8f.json
written atomically
2026-01-22T19:15:57.596Z [DEBUG] getPluginSkills: Processing 0 enabled plugins
2026-01-22T19:15:57.596Z [DEBUG] Total plugin skills loaded: 0
2026-01-22T19:15:57.596Z [DEBUG] Total plugin commands loaded: 0
2026-01-22T19:15:57.596Z [DEBUG] Registered 0 hooks from 0 plugins
2026-01-22T19:15:57.601Z [DEBUG] [STARTUP] setup() completed in 206ms
2026-01-22T19:15:57.601Z [DEBUG] [STARTUP] Loading commands and agents...
============================================================
Bun v1.3.6 (d530ed99) Windows x64 (baseline)
Windows v.win11_ge
CPU: sse42 avx avx2
Args: "c:\Users\abe82683\.vscode\extensions\anthropic.claude-code-2.1.15-win32-x64\resources\native-binary\claude.exe"
"--output-format" "stream-json" "--verbose" "--input-format" "stream-json" "--max-thinking-tokens" "0" "--mo"...
Features: Bun.stderr(2) Bun.stdin(2) Bun.stdout(2) fetch(3) jsc spawn(6) standalone_executable
Builtins: "bun:main" "node:assert" "node:async_hooks" "node:buffer" "node:child_process" "node:constants" "node:crypto"
"node:domain" "node:events" "node:fs" "node:fs/promises" "node:http" "node:https" "node:module" "node:net" "node:os"
"node:path" "node:path/posix" "node:path/win32" "node:perf_hooks" "node:process" "node:querystring" "node:stream"
"node:timers/promises" "node:tls" "node:tty" "node:url" "node:util" "node:zlib" "node:worker_threads" "undici" "ws"
"node-fetch" "node:inspector" "node:http2" "node:diagnostics_channel"
Elapsed: 912ms | User: 171ms | Sys: 31ms
RSS: 0.64GB | Peak: 0.64GB | Commit: 0.70GB | Faults: 157409 | Machine: 68.39GB

panic(thread 69500): Segmentation fault at address 0xCC

panic: Segmentation fault at address 0xD0
panicked during a panic. Aborting.

2026-01-22 13:16:05.650 [info] Claude spawned on channel ovi4w8esau with PID: 22312
2026-01-22 13:16:05.650 [info] Closing Claude on channel: ovi4w8esau
2026-01-22 13:16:05.650 [error] Error from Claude (on channel ovi4w8esau): Error: Claude Code process exited with code 3

Analysis

The crash occurs consistently at the same point during startup:

1. Setup completes successfully (206ms)
2. "[STARTUP] Loading commands and agents..." begins
3. Segmentation fault occurs immediately at memory address 0xCC/0xD0
4. Process aborts with exit code 3

The error also shows an ENOENT error for C:\Users\abe82683\.claude\skills directory, which may be related to the crash.

Troubleshooting Steps Attempted

All of these failed to resolve the issue:

1. ✗ Cleared all Claude Code cache and temporary files
2. ✗ Removed and reinstalled Claude Code binary
3. ✗ Uninstalled and reinstalled VS Code extension
4. ✗ Created missing directories (C:\ProgramData\ClaudeCode\.claude\skills and C:\Users\abe82683\.claude\skills)
5. ✗ Cleared Windows Defender exclusions
6. ✗ Restarted VS Code multiple times
7. ✗ Installed Node.js (v24.13.0)

Potential Root Cause

This appears to be a bug in the Bun v1.3.6 runtime bundled with Claude Code v2.1.15 on Windows. The segmentation fault at
addresses 0xCC and 0xD0 suggests a memory access violation in the Bun runtime during the command/agent loading phase.

Workaround

Currently testing: Using VS Code in WSL2 mode instead of native Windows mode.

Impact

High - Extension is completely unusable on Windows 11 native environment.

What Should Happen?

claude should not error

Error Messages/Logs

see "what's wrong"

Steps to Reproduce

see "what's wrong"

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.15

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

_No response_