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

[TweedBeetle]

Preflight Checklist

• I have searched existing issues and this hasn't been reported for Claude Code Web
• This is a single bug report
• 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:

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:

• Invalid API key · Fix external API key #9694 (similar error but in CLI)
• [BUG] Invalid API Key - Fix external API key when running headless mode with -p #5666 (CLI headless mode)
• [BUG] Missing API key · Run /login - Invalid API key · Please run /login #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.

[github-actions]

Found 3 possible duplicate issues:

1. Invalid API key · Fix external API key #9694
2. Invalid API key · Fix external API key #2356
3. [BUG] macOS OAuth authentication succeeds but auth token not persisted - shows 'Missing API key' after successful login #5244

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
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🤖 Generated with Claude Code

[github-actions]

This issue has been automatically closed as a duplicate of #9694.

If this is incorrect, please re-open this issue or create a new one.

🤖 Generated with Claude Code

[RobinJayaswal]

@TweedBeetle this happens if you set a custom ANTHROPIC_API_KEY environment variable that is invalid. This is true both when running CC locally and in Claude Code on the Web.

https://support.claude.com/en/articles/12304248-managing-api-key-environment-variables-in-claude-code

[github-actions]

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.