Environment:

• SandboxGroup RUNTIME_TYPE=e2b
• Server [runtime] type=flux
• K8s single node (node1)

Repro:

1. osb command run <sandbox_id> -- bash -c "echo hi"
   → 502 Bad Gateway

2. Server log shows:
   POST /sandboxes//proxy/44772/command 502

3. Check endpoints API:
   GET /v1/sandboxes//endpoints/44772?use_server_proxy=true
   → {"endpoint":":44772"}
   But agent pod only listens on 5758; microVM envd listens on 49983.

Root cause:

• SDK hardcodes port 44772 (opensandbox/sync/adapters/command_adapter.py)
• Server /endpoints/{port} returns the same port verbatim, no runtime check
• In E2B mode, execd-style 44772 does not exist; the correct path is:
  Server → Agent:5758 → cri-multiplex → envd:49983

Expected:

• Server should detect runtime=e2b (from SandboxGroup or Agent metadata)
  and map 44772 → Agent:5758 (or return 49983 for direct access)

Workaround in use:

• Direct exec via envd Connect RPC at 169.254.x.x:49983 from firecracker netns