Kiro CLI 2.8.0 - Authentication failed on every prompt after login

[LuanaDias]

Checks

• I have searched github.com/aws/amazon-q-developer-cli/issues and there are no duplicates of my issue
• I have run q doctor in the affected terminal session
• I have run q restart and replicated the issue again

Operating system

Linux 7.0.0-22-generic - Ubuntu 26.04 LTS

Expected behaviour

After a successful login, Kiro CLI should answer prompts normally and return model responses.

Actual behaviour

Every prompt returns:

Authentication failed. Your session may have expired. Run kiro-cli login to re-authenticate.

This happens even after:

• logout/login
• removing ~/.kiro
• updating to Kiro CLI 2.8.0
• successful whoami
• successful doctor

Steps to reproduce

1. Run kiro-cli login
2. Verify with kiro-cli whoami
3. Run kiro-cli chat --legacy-ui
4. Ask any question (e.g. "Who discovered Brazil?")
5. CLI shows "Authentication failed. Your session may have expired."

Environment

OS: Ubuntu 26.04 LTS
Kiro CLI: 2.8.0
Plan: KIRO FREE
Authentication: Builder ID

Commands tested:
- kiro-cli login
- kiro-cli logout
- kiro-cli whoami
- kiro-cli doctor
- kiro-cli chat --legacy-ui

Additional details:
- Login succeeds
- whoami succeeds
- doctor reports "Everything looks good"
- MCP server loads successfully
- Model is shown as "claude-sonnet-4"
- Any prompt results in:
  "Authentication failed. Your session may have expired."