[BUG] Claude Code 2.1.263 crashes with Bun segmentation fault on Windows 11 — reproducible on trivial prompts
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 repeatedly crashes with a Bun runtime segmentation fault when running inside the Antigravity IDE (VS Code-based) on Windows 11. The crash is not tied to any specific action — it has occurred on session startup and on the simplest possible prompt ("hi"), with no complex tool calls or file operations involved.
What Should Happen?
Claude Code should respond to prompts and run normally without the underlying Bun runtime crashing.
Error Messages/Logs
panic(main thread): Segmentation fault at address 0x0
oh no: Bun has crashed. This indicates a bug in Bun, not your code.
https://bun.report/1.4.1/w_183c373bmgggkQugogCizu1fuimgeA2AE
panic(main thread): Segmentation fault at address 0xE8
oh no: Bun has crashed. This indicates a bug in Bun, not your code.
https://bun.report/1.4.1/w_183c373bmgggkQugogC8lmgeA2AwO
panic(main thread): Segmentation fault at address 0xFFFFFFFFFFFFFFFF
oh no: Bun has crashed. This indicates a bug in Bun, not your code.
https://bun.report/1.4.1/w_183c373bmgggkQugogCg3v6dw1zn+DA2DD
panic(main thread): Segmentation fault at address 0x2
oh no: Bun has crashed. This indicates a bug in Bun, not your code.
https://bun.report/1.4.1/w_183c373bmgggkQugogCizu1fuimgeA2AE
panic(main thread): Segmentation fault at address 0x0
oh no: Bun has crashed. This indicates a bug in Bun, not your code.
https://bun.report/1.4.1/w_183c373bmgggkQugogCizu1fuimgeA2AASteps to Reproduce
- Open Antigravity IDE (VS Code-based) on Windows 11 with Claude Code 2.1.263 installed.
- Open a standard git project (branch master).
- Send any prompt in the Claude Code chat panel, including trivial ones like "hi".
- Claude Code process exits with code 3; Bun panics with a segmentation fault.
Note: Crash occurs inconsistently at different points — sometimes on session startup before any prompt is sent, sometimes after a simple "hi" prompt. Memory addresses in the crash vary each time (0x0, 0xE8, 0xFFFFFFFFFFFFFFFF, 0x2), suggesting memory corruption rather than one deterministic trigger.
Claude Model
None
Is this a regression?
Yes, this worked in a previous version
Last Working Version
2.1.111
Claude Code Version
2.1.263
Platform
Other
Operating System
Windows
Terminal/Shell
VS Code integrated terminal
Additional Information
Running inside Antigravity IDE (Google's VS Code-based fork), not standard VS Code.
Already ruled out:
- Not caused by git extensions.worktreeConfig setting — removed it, crash persisted.
- Not caused by a specific plugin — disabled claude-mem@thedotmack, crash still occurred on a plain "hi" prompt with no plugin hooks logged before the crash.
- Even Antigravity's built-in feedback/crash-reporter dialog failed to submit, because the same Bun crash interrupted the reporting process itself mid-send.
Note: A closely related issue (#50640, "Claude Code v2.1.112+ crashes with Segmentation Fault (0xc0000005) on Windows 11") was reported in April 2026 for the same v2.1.112+ native-binary regression and closed as "not planned." This report demonstrates the same underlying crash pattern persists 5 months later on v2.1.263, suggesting it was not actually resolved.
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4 Comments
Update: I also filed a companion report on the Bun repo (oven-sh/bun#42099). Their automated triage bot decoded the bun.report crash links and found that the build commit (83c373b) doesn't exist anywhere in the public Bun repository — meaning Claude Code ships its own private/custom build of Bun. The bot explicitly stated it can't investigate further without that build's debug symbols, and recommended reporting here instead, since this team has visibility into the actual build that's crashing.
This confirms the fix needs to happen on the Claude Code side rather than upstream in Bun. Sharing in case it helps narrow down the investigation.
Additional data point: I tested Claude Code (same version) via the Claude Desktop app on the same Windows 11 machine, and it works fine there — no crashes. The issue appears specific to how Antigravity IDE launches/hosts the Claude Code extension, not a universal problem with this Claude Code/Bun build on my system. This may help narrow down the root cause to Antigravity's extension-host integration rather than the Bun runtime itself.
Update: After Antigravity auto-updated the Claude Code extension to 2.1.266 in the background, the crash stopped occurring once I manually triggered "Restart Extensions" in the Extensions panel (rather than just reopening the IDE). Suspecting the extension host was still running the stale 2.1.263 binary in memory even after the newer version had already downloaded — a full app restart hadn't resolved this earlier in my testing, but restarting extensions specifically did.
For anyone hitting the same crash in Antigravity/VS Code-based editors: check your installed extension version in the Extensions panel, and if it's newer than what's shown in the crash log's binary path, try "Restart Extensions" before trying anything more drastic (downgrading, reinstalling, etc.).
Marking this as resolved on my end for now, but leaving the issue open since the underlying Bun crash bug in the 2.1.263 build is still presumably present — this was a workaround, not necessarily a fix to the root cause.
Further update: The "Restart Extensions" fix from my earlier comment did not hold. After an unrelated power outage forced an unclean shutdown/restart of my PC, the crash returned — and is now worse than before:
Current version: 2.1.266 (auto-updated from 2.1.263 partway through my testing). Same crash signature throughout: "Segmentation fault at address 0x0", Bun v1.4.1, same build commit 83c373b referenced in my original report.
This appears to be a persistent, reproducible crash on every single session start in this environment now, not an intermittent one. Happy to provide any additional diagnostics if helpful.