[BUG] Claude Code Web: "Invalid API key · Fix external API key" error on session start

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported for Claude Code Web
• [x] This is a single bug report
• [x] I am using Claude Code Web (not CLI)

What's Wrong?

When starting a new session in Claude Code Web, receiving the error: "Invalid API key · Fix external API key"

This prevents the session from starting.

What Should Happen?

Claude Code Web should authenticate properly and allow sessions to start without API key errors.

Error Messages/Logs

Invalid API key · Fix external API key

Screenshot showing the error in Claude Code Web interface:
<img width="905" height="165" alt="Image" src="https://github.com/user-attachments/assets/16b9d279-ee61-4d70-9ea1-dfc8381d8540" />

Steps to Reproduce

1. Navigate to Claude Code Web
2. Attempt to start a new session
3. Error appears: "Invalid API key · Fix external API key"
4. Session fails to start

Claude Model

N/A - Session fails to start

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Code Web (latest)

Platform

Claude Code Web

Operating System

macOS

Terminal/Shell

N/A (Web interface)

Additional Information

Related Issues:

• #9694 (similar error but in CLI)
• #5666 (CLI headless mode)
• #5235 (CLI missing API key)

Differences from CLI issues:

• This occurs in Claude Code Web, not the CLI
• Error appears immediately on session initialization

Related closed issues mentioned by user: There was a previously closed issue with similar symptoms but this appears to be a separate/recurring problem in the web interface.