Overview
Forge exposes a REST API for the web UI and an MCP server for AI agent integration. This guide helps troubleshoot API connection and communication issues.Connection Errors
Cannot Connect to Backend
Problem: Frontend shows “Failed to connect to API” or network errors Symptoms:- Tasks don’t load
- Empty project list
- Console errors:
net::ERR_CONNECTION_REFUSED
Check Backend is Running
Check Backend is Running
Check Port Configuration
Check Port Configuration
Check Firewall
Check Firewall
Check for Port Conflicts
Check for Port Conflicts
CORS Errors
Problem:Access to fetch has been blocked by CORS policy
Cause: Backend and frontend on different origins
Solution:
Timeout Errors
Problem: Requests timeout with no response Solutions:Authentication Errors
Unauthorized (401)
Problem: API returns 401 Unauthorized Cause: Missing or invalid auth token (GitHub OAuth) Solution:Forbidden (403)
Problem: API returns 403 Forbidden Cause: Insufficient permissions for requested resource Solution:Request Errors
Bad Request (400)
Problem: API returns 400 Bad Request Causes:- Invalid JSON
- Missing Required Fields
- Invalid Field Values
Not Found (404)
Problem: API returns 404 Not Found Solutions:Internal Server Error (500)
Problem: API returns 500 Internal Server Error Solution:MCP Server Errors
MCP Server Not Responding
Problem: AI agent can’t connect to Forge via MCP Symptoms:- MCP tools not available in AI agent
- Connection timeoutErrors in AI agent logs
Verify MCP Mode
Verify MCP Mode
Check MCP Configuration
Check MCP Configuration
Claude Code (Cursor (settings.json):
.claude/mcp.json):Get Project ID
Get Project ID
Check MCP Logs
Check MCP Logs
MCP Tools Not Available
Problem:list_tasks, create_task, etc. not showing up in AI agent
Solution:
1
Verify MCP Server Started
2
Check Tool Mode
3
Restart AI Agent
MCP Tool Execution Failed
Problem: MCP tool returns error when executed Common Errors:- Project Not Found
- Task Not Found
- Invalid Arguments
SSE (Server-Sent Events) Issues
Real-time Logs Not Streaming
Problem: Task execution logs don’t appear in real-time Causes & Solutions:Corporate Proxy Blocking SSE
Corporate Proxy Blocking SSE
Browser Limiting Connections
Browser Limiting Connections
Backend Not Sending Events
Backend Not Sending Events
Database Errors
SQLite Errors
Problem: API returns database-related errors- Database Locked
- Database Corrupted
- Migration Failed

