While offline mode is working fine in Copilot CLI it is not working in ACP or LSP mode, even when all necessary env variables are set.
There seem to be hardcoded credential checks f.e. in "session/new".

Example:
$env:COPILOT_OFFLINE="true"
$env:COPILOT_PROVIDER_BASE_URL="http://localhost:10010/v1"
$env:COPILOT_PROVIDER_API_KEY="sk-dummy-key"
$env:COPILOT_MODEL="qwen36"
copilot --acp
{"jsonrpc": "2.0", "id": 2, "method": "session/new", "params": {"cwd": "C:/path/to/some/project", "mcpServers": []}}
{"jsonrpc":"2.0","id":2,"error":{"code":-32000,"message":"Authentication required"}}