[BUG] runtime segfault at non-canonical address 0xFFFFFFFFFFFFFFFF kills the CLI mid-session (Windows, v2.1.239)

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?

After roughly 2 hours of an interactive session, claude.exe died with a Bun panic and dropped
back to the PowerShell prompt. The session was lost. Two other concurrent claude processes on
the same machine were unaffected and kept running.

Bun v1.4.0 (fdb5e06cc) Windows x64
Windows v10.26200
CPU: sse42 avx avx2
Args: "C:\Users\<user>\.local\bin\claude.exe" "--dangerously-skip-permissions"

Elapsed: 7147917ms | User: 24812ms | Sys: 21437ms
RSS: 0.34 GB | Peak: 0.62 GB | Commit: 0.72 GB | Faults: 345015 | Machine: 33.58 GB

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

Bun crash report: https://bun.report/1.4.0/w_1fdb5e06mgggkIuhogCijwr3D_os177C________A2DD

What Should Happen?

it doesn't crash ;)

Error Messages/Logs

Steps to Reproduce

No deterministic repro — the crash happened once, mid-session, and has not recurred.
Reporting it for the crash-report URL rather than as a reproducible defect.

Conditions at the time:

1. Run claude --dangerously-skip-permissions in a large repo (Windows, native build).
2. Keep an interactive session alive for ~2 hours (Elapsed: 7147917ms).
3. Two other claude processes were running concurrently against the same working tree;

both survived, only this one died.

1. The crash occurred while the agent wrote a small Markdown file and read a sibling

index file (auto-memory write). Small payload, no unusual tool.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.139

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

<img width="3839" height="665" alt="Image" src="https://github.com/user-attachments/assets/803cf520-81e5-40b0-933f-2b6befb8abf2" />