CAPIError: 400 400 Bad Request

### Describe the bug

● Request failed (transient_bad_request). Retrying...

● Request failed (transient_bad_request). Retrying...

✗ Execution failed: CAPIError: 400 400 Bad Request

### Affected version

_No response_

### Steps to reproduce the behavior

write something at normal powershell and nothing happens but error:

╭──────────────────────────────────────────────────────────────────────────────────────────────────╮
│ ╭─╮╭─╮ │
│ ╰─╯╰─╯ GitHub Copilot v1.0.34 │
│ █ ▘▝ █ Describe a task to get started. │
│ ▔▔▔▔ │
│ Tip: /init Initialize Copilot instructions for this repository. │
│ Copilot uses AI. Check for mistakes. │
╰──────────────────────────────────────────────────────────────────────────────────────────────────╯

● 💡 No copilot instructions found. Run /init to generate a copilot-instructions.md file for this project.

● Environment loaded: 1 extension, 10 MCP servers, 57 skills, 19 agents

❯ hola

● agent-alias-router loaded

● Request failed (transient_bad_request). Retrying...

● Request failed (transient_bad_request). Retrying...

✗ Execution failed: CAPIError: 400 400 Bad Request
(Request ID: D3C6:2FE361:9351D2:A31075:69E67EDB)

### Expected behavior

normal GOOOOODWORKING chat... it's became imposible to work with... IMPOSSIBLE... I have a proffessional account and ITS NOT WORKING... is there a refound?

### Additional context

_No response_

No source file or test is identified in the report. Start by reproducing the failure in PowerShell with Copilot CLI v1.0.34 using the prompt "hola", then trace the transient_bad_request response and compare it with a working chat request. Done means normal chat works without repeated retries or a CAPIError 400.

Written by the indexing model from the issue text.