Extension host becomes unresponsive during Claude Code startup on VS Code 1.129.1 (Node.js 24.18.0) — consistent 60s timeout despite subprocess initializing normally

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?

Environment:

VS Code: 1.129.1 (user setup)
Claude Code extension: 2.1.216
Node.js (VS Code bundled): 24.18.0
Electron: 42.6.0 / Chromium: 148.0.7778.280
OS: Windows 10 (10.0.19045), x64

What's happening:

Every attempt to launch Claude Code from the VS Code extension fails with:

Error: Subprocess initialization did not complete within 60000ms — check authentication and network connectivity

This happens consistently, on every launch, regardless of whether it's a new session or resuming an existing one.

Key evidence this is not a network/auth/AV issue:

The claude.exe subprocess itself completes its full internal initialization in under 2 seconds every time. Logs consistently show LSP notification handlers registered successfully for all 0 server(s) completing quickly, followed by total silence until the 60s timeout fires — no further log output, no errors.
Running claude -p "ping" directly from a terminal (outside VS Code) works and returns a response, confirming the CLI, auth, and network path are all functional independent of the extension.
VS Code's own DevTools console shows the extension host itself going unresponsive during this window:
INFO Extension host (LocalProcess pid: 14376) is unresponsive.
INFO UNRESPONSIVE extension host: starting to profile NOW
INFO Extension host (LocalProcess pid: 14376) is responsive.

This repeats multiple times around each failed launch attempt.

Ruled out (extensively tested):

Norton Antivirus — fully disabled and excluded, issue persisted
Windows Defender — checked, not the cause
Proxy configuration — HTTP_PROXY/HTTPS_PROXY/ALL_PROXY env vars confirmed empty; netsh winhttp show proxy confirmed no proxy
IPv6 routing — disabled IPv6 entirely on the network adapter and rebooted; confirmed via a standalone Node.js DNS/HTTPS test script that resolution and connection now complete in under 1 second
NODE_OPTIONS=--dns-result-order=ipv4first — set and confirmed active, no change
Workspace trust — confirmed trusted, not a factor
Extension version — reproduced on 2.1.215 and 2.1.216; attempted downgrade to an older extension version did not resolve it (auto-update re-installed latest)

Conclusion:
Given the subprocess completes initialization quickly and independently of VS Code, but the extension host itself becomes unresponsive during the same window, this points to a compatibility issue between the Claude Code extension and the Node.js 24 runtime now bundled with recent VS Code versions — likely related to how the extension handles the subprocess's ready/stdout signal during extension host activation.

Suggested reference: This matches the pattern described in #65440 (PendingMigrationError / navigator global under Node.js 24), though I did not confirm that specific error string in my own DevTools output.

Logs: Happy to attach full extension output logs on request (contain machine-specific paths, trimming before posting).

What Should Happen?

Error should not come

Error Messages/Logs

VS Code Console log:

INFO Extension host (LocalProcess pid: 14376) is unresponsive.
localProcessExtensionHost.ts:334 Extension Host
localProcessExtensionHost.ts:335 Debugger attached.
log.ts:117  INFO Extension host (LocalProcess pid: 14376) is responsive.
log.ts:117  INFO UNRESPONSIVE extension host: received responsive event and cancelling profiling session
log.ts:117  INFO UNRESPONSIVE extension host: starting to profile NOW
log.ts:117  INFO Extension host (LocalProcess pid: 14376) is unresponsive.
log.ts:117  INFO Extension host (LocalProcess pid: 14376) is responsive.
console.ts:139 [Extension Host] Skipping Python env activation for environment type: (none)
log.ts:117  INFO Extension host (LocalProcess pid: 14376) is unresponsive.
localProcessExtensionHost.ts:334 Extension Host
localProcessExtensionHost.ts:335 Debugger attached.
log.ts:117  INFO UNRESPONSIVE extension host: starting to profile NOW
log.ts:117  INFO Extension host (LocalProcess pid: 14376) is responsive.
log.ts:117  INFO UNRESPONSIVE extension host: received responsive event and cancelling profiling session

Claude extension output log:

2026-07-21 23:24:42.697 [info] From claude: 2026-07-21T17:54:42.696Z [DEBUG] LSP notification handlers registered successfully for all 0 server(s)

2026-07-21 23:24:53.416 [error] Failed to load config cache: Error: Subprocess initialization did not complete within 60000ms — check authentication and network connectivity
2026-07-21 23:24:53.441 [info] Getting authentication status
2026-07-21 23:24:53.441 [info] OAuth tokens found in secure storage
2026-07-21 23:24:53.441 [info] Getting authentication status
2026-07-21 23:24:53.441 [info] OAuth tokens found in secure storage
2026-07-21 23:24:53.442 [error] Error processing client request: Error: Subprocess initialization did not complete within 60000ms — check authentication and network connectivity
2026-07-21 23:24:54.098 [info] Received message from webview: {"type":"interrupt_claude","channelId":"ueiqa9p2do"}
2026-07-21 23:24:54.104 [warning] Channel not found: ueiqa9p2do
2026-07-21 23:25:25.438 [info] Closing Claude on channel: 2ekw3gfduwc
2026-07-21 23:25:25.438 [error] Error spawning Claude (on channel 2ekw3gfduwc): Error: Subprocess initialization did not complete within 60000ms — check authentication and network connectivity
2026-07-21 23:25:25.439 [info] OAuth tokens found in secure storage
2026-07-21 23:25:25.445 [info] Received message from webview: {"type":"request","channelId":"2ekw3gfduwc","requestId":"chmgod04zdk","request":{"type":"log_event","eventName":"sdk_stream_ended_no_result","eventData":{"had_error":true,"subagent_count":0,"message_count":6}}}
2026-07-21 23:25:25.451 [warning] Channel not found for logEvent: 2ekw3gfduwc
2026-07-21 23:25:25.452 [info] Received message from webview: {"type":"request","requestId":"vx2201kc53f","request":{"type":"update_session_state","sessionId":"9673860e-ce23-4810-83e7-ae99273cd0ca","state":"idle","title":"Check agent availability"}}
2026-07-21 23:25:33.520 [info] Received message from webview: {"type":"request","requestId":"1yz2a9y11y5","request":{"type":"open_output_panel"}}

Steps to Reproduce

1. Open VS Code
2. In claude extension, write any message and post.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

VS Code 1.116

Claude Code Version

2.1.216

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_