⚒️ fix: MCP Initialization Flows

[dustinhealy]

Summary

This pull request fixes issues with MCP OAuth flows concerning cancellation handling, polling cleanup, UI state management during server initialization, and most critically resolving a bug introduced in #8718 which broke initial OAuth flows.

Backend Changes:

• api/server/routes/mcp.js:

  • OAuth Cancellation: Changed completeFlow to failFlow for proper cancellation state management, preventing stale client IDs and "Client ID mismatch" errors
  • Reinitialize Success Logic: Fixed success condition to properly handle OAuth-required servers (success: (userConnection && !oauthRequired) || (oauthRequired && oauthUrl))

• api/server/services/MCP.js:

  • Cancellation vs Error Detection: Added logic to differentiate between user-cancelled flows and actual OAuth failures
  • UI Error Prevention: Returns hasFailedFlow: false for cancelled flows to prevent error triangle display in UI

Frontend Changes:

• client/src/hooks/MCP/useMCPServerManager.ts:

  • Polling Cleanup: Added clearInterval(pollInterval) in error conditions and catch blocks to stop infinite polling
  • OAuth Cancellation Flow: Reordered cancellation to call backend first, then cleanup frontend state only on success
  • Server Interaction Guards: Added isInitializing checks to prevent server selection/toggling during initialization
  • Auto-OAuth Parameter: Added autoOpenOAuth parameter to initializeServer for better OAuth URL handling control

• client/src/components/Chat/Input/MCPSelect.tsx:

  • Visual Feedback: Added opacity styling and disabled state for initializing servers
  • Interaction Prevention: Disabled button clicks during server initialization

• client/src/components/Chat/Input/MCPSubMenu.tsx:

  • Consistent Disabled State: Applied same disabled/opacity styling as MCPSelect for initializing servers

• client/src/components/MCP/ServerInitializationSection.tsx:

  • OAuth Parameter Fix: Updated initializeServer call to pass autoOpenOAuth: false for manual initialization

Change Type

• Bug fix (non-breaking change which fixes an issue)

Testing

Manual verification of MCP OAuth flow scenarios:

• OAuth flow initiation and completion
• OAuth flow cancellation at various stages
• OAuth flow reinitialization and completion after cancellation
• Error handling during OAuth failures
• Server selection/deselection during initialization attempts
• Polling behavior after errors and cancellations
• UI state consistency across different cancellation scenarios
• Multiple server initialization attempts

Checklist

• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• I have commented in any complex areas of my code
• My changes do not introduce new warnings
• A pull request for updating the documentation has been submitted.