v2.1.126 signature verification fails on VS Code Insiders only (Stable works)

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?

Updating anthropic.claude-code from 2.1.123 → 2.1.126 fails on VS Code Insiders with a signature verification error. The same update succeeds on VS Code Stable, so this looks like an Insiders-specific compatibility issue with the v2.1.126 signed VSIX.

What Should Happen?

Extension updates cleanly on VS Code Insiders without signature verification errors, just like it does on VS Code Stable.

Error Messages/Logs

Cannot install 'Claude Code for VS Code' extension because Visual Studio Code - Insiders cannot verify the extension signature.

Signature verification failed with 'UnknownError' error.

Dialog offers only Learn More, Report Issue, Install Anyway (Don't Verify Signature), or Cancel.

Steps to Reproduce

1. Open VS Code – Insiders with anthropic.claude-code 2.1.123 installed
2. Extensions pane → click Update to v2.1.126
3. Update fails with the signature verification dialog above

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.123

Claude Code Version

2.1.126

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Environment:

• Editor: Visual Studio Code – Insiders
• Extension: anthropic.claude-code 2.1.123 → 2.1.126
• OS: macOS Tahoe (26)

Workaround:
Install Anyway (Don't Verify Signature) bypasses the check, but obviously isn't ideal for a signed Anthropic extension.

Likely cause:
Insiders typically runs a newer/stricter signature verifier than Stable. The v2.1.126 VSIX signature appears to be valid for Stable's verifier but not Insiders' — possibly a signing-format or certificate-chain detail the newer verifier handles differently. Earlier versions (2.1.123 and prior) installed fine on Insiders, so something changed in how 2.1.126 was signed/packaged.

Expected vs Actual:

| | Expected | Actual |
|---|---|---|
| Stable | Updates cleanly | ✅ Updates cleanly |
| Insiders | Updates cleanly | ❌ Signature verification fails |