Duplicate Item Errors

### Describe the bug

After initial prompt during processing, I receive errors of this format:
Execution failed: CAPIError: 400 {"error":{"code":"bad_request","type":"websocket_error","message":"Duplicate item found with id fc_call_3L6mbkYELCQh2XxmHQlVommW. Remove duplicate items from your input and try again."}} (Request ID: 00000-63415e69-425e-45d5-8f8b-23bcb99c727d)

With a subsequent prompt, I see this output:
● Request failed (transient_bad_request). Retrying...

● Request failed (session_token_refresh). Retrying...

● Request failed (session_token_refresh). Retrying...
✗ Execution failed: CAPIError: 400 Duplicate item found with id fc_call_3L6mbkYELCQh2XxmHQlVommW. Remove duplicate items from your input and try again. (Request ID: 5CA2:F9304:7D0A:8E64:6A189465)

I have quit the session and resumed, cleared the session, and quit and started fresh. I have switched between GPT-5.4, Sonnet 4.6 and auto and still receive errors.

### Affected version

GitHub Copilot CLI 1.0.54

### Steps to reproduce the behavior

1. copilot cli in interactive mode
2. use an agent defined at user-level
3. run prompt

### Expected behavior

No duplicate request errors

### Additional context

macOS Tahoe 26.5
zsh shell
gh installed via homebrew

No se indican archivos fuente ni pruebas. Empieza reproduciendo el fallo en el modo interactivo de Copilot CLI con un agente a nivel de usuario en macOS usando zsh y, después, compara los prompts iniciales y posteriores; se considerará terminado cuando esos prompts ya no produzcan errores de elementos duplicados ni bucles de reintento.

Escrito por el modelo de indexación a partir del texto del issue.