Fix Claude Code Agent Teams Non-ASCII Name API Header Error

What this error means

Header has invalid value (x-claude-code-agent-id with non-ASCII characters) is a Claude Code failure pattern reported for developers trying to fix ‘header has invalid value’ error when using non-ascii names in claude code agent teams. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Claude Code Agent Teams feature rejects non-ASCII characters in team_name or name parameters. The x-claude-code-agent-id header only accepts ASCII, causing ‘Header has invalid value’ API error.

Common causes

• Using non-ASCII characters (CJK, emoji, accented Latin) in team_name or teammate name causes API rejection. The x-claude-code-agent-id header cannot handle UTF-8 characters, breaking international teams.
• Claude Code Agent Teams feature rejects non-ASCII characters in team_name or name parameters. The x-claude-code-agent-id header only accepts ASCII, causing ‘Header has invalid value’ API error.

Quick fixes

1. Confirm the exact error signature matches Header has invalid value (x-claude-code-agent-id with non-ASCII characters).
2. Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/anthropics/claude-code/issues/58434

Evidence note: Claude Code Agent Teams feature rejects non-ASCII characters in team_name or name parameters. The x-claude-code-agent-id header only accepts ASCII, causing ‘Header has invalid value’ API error.

Related errors

• Claude Code agent team creation fails
• x-claude-code-agent-id invalid characters

FAQ

What should I check first?

Start with the exact Header has invalid value (x-claude-code-agent-id with non-ASCII characters) text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Claude Code workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without Header has invalid value (x-claude-code-agent-id with non-ASCII characters).