comfy-mcp-fixes

# comfy-mcp fixes Gotchas collected while building a custom ComfyUI node with a web UI and driving it from an agent. Tested on ComfyUI Desktop, frontend 1.53, ComfyUI 0.37. Examples assume the server is on `http://127.0.0.1:8188`; substitute your port. ## 1. Custom node JS never loads: check WEB_DIRECTORY A pack's `web/` folder is served ONLY if its `__init__.py` exports it: ```python WEB_DIRECTORY = "./web" __all__ = ['NODE_CLASS_MAPPINGS', 'NODE_DISPLAY_NAME_MAPPINGS', 'WEB_DIRECTORY'] ``` Verify: `GET /api/extensions` must list the pack's JS. Adding or changing `WEB_DIRECTORY` needs a **backend restart**. Editing an already-served JS file only needs a **page reload**. ## 2. DOM widget renders empty: use node.addDOMWidget On this frontend, `window.comfyAPI.domWidget.addWidget(node, name, el, opts)` does NOT throw but returns a widget named `"undefined#1"` with `element: null`. try/catch fallbacks never fire. Always call: ```js this.addDOMWidget("name", "custom", container, { serialize: false }); ``` Data that must persist goes in a normal hidden/STRING widget (e.g. `lora_stack_json`), not in the DOM widget. ## 3. restart_comfyui says no_background_server comfy-cli can only stop/restart servers IT launched. A ComfyUI started by something else (the Desktop shell, a launcher) is untracked. 1. `server_info`, then `job`/`system_stats`: confirm the queue is empty and nothing is generating. Never kill a server mid-generation. 2. Find the python PID (`main.py --listen 127.0.0.1 --port 8188`) and kill it (`taskkill /PID <pid> /T /F` on Windows; in Git Bash first `export MSYS2_ARG_CONV_EXCL='*'` so `/PID` is not mangled into a path). 3. `launch_comfyui` with the same args. It is tracked from then on, so later `restart_comfyui` works. 4. Confirm with `server_info` and `/api/extensions`. ## 4. Verify UI in a browser pane, not with screen automation Desktop-automation access is often denied for the ComfyUI Desktop window. Use a browser tool pointed at `http://127.0.0.1:8188` instead: - Reload after JS edits. If the page stalls at the splash, reload again. - Create a test node: `LiteGraph.createNode("ClassName")`, `app.graph.add(n)`. Wait until the workflow restore has settled or the node is dropped. - Inspect: `app.extensions`, `LiteGraph.registered_node_types`, `node.widgets.map(w=>[w.name,w.type,!!w.element])`. - Screenshot `zoom` may not crop; resize the viewport instead and reset it when done. - Remove test nodes afterward and never save the user's workflow. ## 5. Keep the repo source and the installed pack in sync Install a pack under development as a directory junction/symlink to the repo folder so there is one copy: JS edits then need only a page reload, Python edits a restart. On Windows, `python -c "import _winapi; _winapi.CreateJunction(src, dst)"` works where `mklink` through Git Bash does not. If you must copy instead, diff the two afterward. ## 6. Do not leave a comfy-cli server running (Desktop update loop) A server started with `launch_comfyui` runs from the same env as ComfyUI Desktop and blocks its updater ("can't update, loop"). Before updating or opening Desktop: `stop_comfyui`, then kill stragglers (`taskkill /F /IM "Comfy Desktop.exe" /T`), then launch Desktop and let it update. Afterwards verify with `/object_info` and a real workflow, and prefer the Desktop's own server over a second one. Desktop may show a newer version string (e.g. a master build) than `comfyui_version.py`. ## 7. Model browser shows few items / no previews, or Desktop is slow to open That is the duplicate-model-root bug class. See the companion skill `comfy-duplicate-model-roots`. ## More gotchas - Do not call `launch_comfyui` and file operations in the same parallel batch; the server starts before the swap finishes. Run `stop_comfyui` first. - Python `urllib` inside the ComfyUI venv can fail CivitAI with `certificate has expired`; build the SSL context from `certifi.where()`. - Ollama "thinking" models burn `num_predict` on reasoning and return empty content; send `"think": false`. - LoRA file headers are identical for same-rank LoRAs, so duplicate detection must sample file content, not just the header. - Several packs register similarly named DOM (e.g. `.card-grid`); find a node's own widget element via `node.widgets.find(w => w.name === "...").element`, not `document.querySelector`. - Do not copy another pack's code into yours without checking its licence; a GPL pack's code makes your pack GPL.