[BUG] VS Code extension 2.1.211: renderer crash (SIGBUS, code 135) opening projects with large session-transcript dirs

This was generated by claude fable 5 xhigh:

Summary

The Claude Code VS Code extension v2.1.211 reliably crashes the VS Code renderer process (SIGBUS, exit code 135) within ~15–25 seconds of opening a workspace folder that has a large Claude Code session-transcript directory (295 MB / 149 .jsonl files under ~/.claude/projects/<project>). The window dies with:

The window terminated unexpectedly (reason: 'crashed', code: '135')

Crash happened on every open of the affected project. Projects with smaller session dirs (≤82 MB) open fine on the same machine.

After updating the extension to v2.1.212 the crash no longer reproduces, so this may already be fixed — filing for awareness/confirmation, and in case others hit it on 2.1.211.

Environment

• VS Code: 1.129.0 (125df4672b8a6a34975303c6b0baa124e560a4f7), x64
• Extension: anthropic.claude-code 2.1.211 (crashes) → 2.1.212 (appears fixed)
• OS: Linux, kernel 7.0.0-27-generic, GNOME on Wayland
• Affected project session dir: 295 MB, 149 transcript .jsonl files (heavy recent usage, none older than 30 days)

Repro (on 2.1.211)

1. Have a project whose ~/.claude/projects/<project-hash>/ contains hundreds of MB of session transcripts.
2. Open that folder in VS Code with the Claude Code extension enabled.
3. Renderer process crashes with code 135 (SIGBUS) within ~15–25 s, every time.

Isolation evidence

| Configuration | Result |
|---|---|
| Normal open (all extensions, claude-code 2.1.211) | crash ≤25 s, 6+ times over 2 days |
| code --disable-extensions | no crash |
| Only anthropic.claude-code disabled (100+ other extensions on, incl. Copilot) | no crash |
| All extensions on, claude-code updated to 2.1.212 | no crash |

Also ruled out: cleared the workspace's workspaceStorage (203 MB, incl. 71 MB state.vscdb and 35 MB chatSessions) — crash persisted, so not stale editor/chat UI state. Disk space, RAM, and GPU logs clean. Other workspaces unaffected.

Log signature (sanitized)

main.log:

[info] Extension host with pid <old> exited with code: 0, signal: unknown.
[info] Extension host with pid <new> exited with code: 0, signal: unknown.
[error] CodeWindow: renderer process gone (reason: crashed, code: 135)
[error] Extension host with pid <old> still exists, forcefully killing it...

renderer.log, seconds before each crash — chat-session-type warnings followed by extension-host restart and then repeated IPC deserialization failures:

[warning] Attempted to report in-progress status for unknown chat session type 'copilot-cloud-agent'
[warning] Attempted to report in-progress status for unknown chat session type 'copilotcli'
[warning] Attempted to report in-progress status for unknown chat session type 'claude-code'
[info] Started local extension host with pid <new>.
[error] Cannot read properties of undefined (reading '0'): TypeError: Cannot read properties of undefined (reading '0')
    at GHt.onBuffer (vscode-file://vscode-app/usr/share/code/resources/app/out/vs/workbench/workbench.desktop.main.js:1076:1523)
    ...
    at MessagePort.we (vscode-file://vscode-app/usr/share/code/resources/app/out/vs/workbench/workbench.desktop.main.js:431:15546)
[error] Cannot read properties of undefined (reading '0'): TypeError: Cannot read properties of undefined (reading '0')
    at cLi.onRawMessage (vscode-file://vscode-app/usr/share/code/resources/app/out/vs/workbench/workbench.desktop.main.js:1074:6161)
    ...

A Crashpad minidump of the renderer crash exists; happy to share it privately if useful (not attaching raw dumps/transcripts publicly).

Hypothesis

Extension's chat-session enumeration/sync on window open chokes on very large session-transcript directories, triggers an extension-host restart mid-handshake, and the renderer dies (SIGBUS) while deserializing the resulting IPC buffers.