Reverse Proxy with Caddy returns 502 — FastAPI backend reachable, but routes like /test fail

[ChristophNeudorf]

🧩 Critical Connectivity Issues with OpenManus (Docker + Caddy Setup)

Hi team,

I'm encountering major issues getting OpenManus to work behind Caddy on a dedicated server. Below is a structured overview of all tests, observations, and current limitations. I’ve spent over 20 hours debugging and would greatly appreciate your support.

---

🧭 Deployment Context

• Hosting: Hetzner VPS (Ubuntu 22.04)
• Reverse Proxy: Caddy (running via Docker)
• Domain: https://assistent.agentaiplusblue.de
• Caddyfile:

  assistent.agentaiplusblue.de {
      reverse_proxy openmanus_unified_1:8000
  }

❗️Main Problem

Despite working /openapi.json, calling /test through the public domain fails with HTTP 502 Bad Gateway.
All paths seem correctly routed. Backend confirms FastAPI is running, yet Caddy returns 502.

❗️Main Problem

🔍 Observations & Tests

✅ Backend Works Internally:

curl http://172.20.0.3:8000/openapi.json ✅
curl http://172.20.0.3:8000/test ❌ {"detail": "Not Found"}

curl https://assistent.agentaiplusblue.de/test → ❌ HTTP 502

❌ Public Access via Domain
curl https://assistent.agentaiplusblue.de/test → ❌ HTTP 502

🔁 Docker & Network
• openmanus_unified_1 runs with correct port mapping to 0.0.0.0:8000
• caddy container reverse proxy targets that IP:PORT
• curl inside container now works (after manual install of curl)

📄 FastAPI Definition in src/server.py
@app.get("/test")
def test():
return JSONResponse(content={"message": "Caddy works!"})

❌ Frontend Container
• openmanus_frontend_1 exits with code 1 — unknown cause.
• The issue persists even without frontend container.

⸻

✅ What Works
• TLS and routing with Caddy are operational
• Backend responds on /openapi.json
• Internal docker network (172.20.0.X) correctly forwards

⸻

❓ Key Questions
1. Does OpenManus require the frontend container for /test or /docs to respond?
2. Are there known conflicts with FastAPI/Caddy routing in the unified setup?
3. Is there a preferred method to test OpenManus standalone (e.g. uvicorn manually)?
4. Should /test return the expected message even if frontend is missing?

⸻

🧪 System Details

Docker: v24+
Python: 3.11
Uvicorn: installed inside container
OS: Ubuntu 22.04
Caddy: latest Docker image

Thanks in advance for your time and support 🙏
This looks like a very promising project — I’d love to contribute once it’s up and running.