Hey @yashksaini-coder, nice work on this! The overall structure is solid and follows existing patterns well. I've got some feedback before this is ready to merge:

Security stuff:

• The credential file permissions (writeFileSync with mode: 0o600) only apply on file creation. If the file already exists with looser permissions, they won't get tightened. Worth adding an explicit chmod on every write.
• The token cache key uses only the first 8 chars of the OAuth token (githubOAuthToken.slice(0, 8)) - two different tokens with the same prefix would share a cache entry. Use the full token or a hash instead.
• Might want to add a clearCopilotTokenCache() export so credentials can actually be invalidated without waiting for expiry.

Naming:

• refreshToken in CopilotCredential actually stores the OAuth access token. Since this is a brand new feature with no existing users, now's the time to rename it to oauthToken or accessToken before it ships and actually creates a backward-compat burden.

Code duplication:

• The "No Copilot credentials" error message is defined identically in both provider-factory.ts and client-factory.ts - extract to a shared constant.
• COPILOT_HEADERS is defined in github-copilot.ts but then re-hardcoded in provider-factory.ts. Import and reuse.
• The CLI login path in cli.tsx reimplements the device flow inline instead of reusing logic from copilot-login.tsx. Would be cleaner to extract the core flow into a shared function both paths can call.

Robustness:

• pollForOAuthToken has a while (true) with no timeout or max iterations. If the user never completes the device flow and the server never returns expired_token, this loops forever. Add a timeout (maybe 15 min?).
• apiKey: 'dummy-key' in the provider factory works because the custom fetch overrides the auth header, but it's fragile - at least drop a comment explaining why it's there.

Tests:

• The cache test doesn't cover the case where the cached token is expired - worth adding one where expires_at is in the past.
• The new provider-factory test manipulates process.env.NANOCODER_CONFIG_DIR without test.serial, which could race with other tests. Mark it serial or isolate it differently.
• test-copilot.sh imports from ./dist/ which couples it to a fresh build. Consider using tsx like the AVA tests do.

Minor:

• A few new files are missing trailing newlines.
• Default models gpt-4o,claude-3-5-sonnet-20241022 are aged - could we choose different model defaults?
• The hardcoded VS Code Copilot OAuth client ID (Iv1.b507a08c87ecfe98) is worth documenting prominently so maintainers know about the external dependency.

Overall the feature design is good - the main blockers are the refreshToken rename, the unbounded polling loop, and the cache key issue. The rest is cleanup. Nice contribution! :D

Hey @yashksaini-coder, just continuing to test and found a few more issues to address:

1. /copilot-login is broken - the component is frozen on render

The CopilotLogin component uses useState, useEffect, useInput, and <Spinner> - but command output goes through addToChatQueue -> chatComponents -> ChatQueue -> Ink's <Static>. <Static> renders items once and freezes them. That means:

• The spinner never animates (which is what I see — it's stuck on ⠋)
• The useEffect that calls startDeviceFlow() fires but state updates never re-render
• The user code / verification URL never appear on screen
• useInput for "Press Enter to continue" never works

This is an architectural mismatch. The component needs to render as a live component (using setLiveComponent / the liveComponent slot) instead of being added to the chat queue, or the login flow needs to be non-interactive (just print static text and open the browser automatically). Other commands that work fine in <Static> are ones that return a single static React element - not stateful interactive components.

2. The CLI path (nanocoder copilot login) has the same underlying issue as my earlier comment - startDeviceFlow() has no fetch timeout, so it can hang forever.