copilot.sim.ai returns 404 — Copilot backend unreachable

[fractional-pm]

Description

Self-hosted SimStudio instance cannot reach the copilot backend at copilot.sim.ai. All copilot chat requests fail with:

Copilot backend error (404): 404 page not found

Steps to Reproduce

1. Deploy SimStudio via Docker (ghcr.io/simstudioai/simstudio:latest)
2. Set COPILOT_API_KEY=sk-sim-copilot-... (valid key from sim.ai dashboard)
3. Open any workspace and try to use the Copilot chat
4. Error appears: "Copilot backend error (404): 404 page not found"

Investigation

• curl -L https://copilot.sim.ai/ → 301 redirect to https://www.copilot.sim.ai/ → 404
• The SIM_AGENT_API_URL defaults to https://copilot.sim.ai in lib/copilot/constants.ts
• API key is correctly passed as x-api-key header
• The issue is server-side — the domain redirects to a www subdomain that returns 404

Environment

• SimStudio image: ghcr.io/simstudioai/simstudio:latest
• SIM_AGENT_VERSION: 3.0.0
• Deployment: Docker Compose on Ubuntu 24.x

Expected Behavior

Copilot backend should be reachable and respond to authenticated requests.

Question

Is there a different endpoint URL we should be using? Or is copilot.sim.ai currently down?