What it means
The ComfyUI web UI talks to the backend over a WebSocket. "Reconnecting…" means that channel dropped. Sometimes the browser simply lost the socket and reconnects on its own; more often the backend itself stopped responding — a crash (frequently an out-of-memory kill), a frozen heavy node, or a proxy/tunnel that timed out on a long request.
The authoritative signal is the server console: if it shows a traceback or the process exited, the UI is reconnecting to a server that is no longer running the job.
Common causes
- The server process crashed mid-run (commonly out of memory).
- A heavy node froze the backend so it stopped answering.
- A reverse proxy or tunnel timed out on a long-running request.
- The browser tab was backgrounded/slept and dropped the socket.
How to fix it
- 1
Check the server console first
Look at the ComfyUI terminal for a crash, traceback, or an out-of-memory kill. That tells you whether the backend died or merely stalled.
- 2
Restart the ComfyUI server
If the process crashed or exited, restart it, then reload the browser so the UI reconnects to a live backend.
- 3
Reduce load if it was resource-driven
If the crash was memory-related, apply the CUDA out-of-memory fixes (lower resolution/batch, tiled VAE, low-VRAM mode) before re-running.
- 4
Raise proxy/tunnel timeouts
When running behind a reverse proxy or tunnel, increase the read/idle timeout so long generations are not cut off.
Frequently asked questions
Frequently Asked Questions
Quick answers to the most common questions.
Related errors
Make every ComfyUI run reproducible
Numonic captures the full workflow behind each ComfyUI generation — models, samplers, seeds, prompts, and custom nodes — so a setup that finally works is one you can find and rebuild, not re-debug.