ComfyUI API Skill

Connect to ComfyUI's REST API to execute workflows, monitor progress, and retrieve outputs.

Configuration

• Default URL: http://127.0.0.1:8188
• Custom URL: Set in project manifest or pass as parameter
• Timeout: 30s for API calls, no timeout for generation polling

Two Modes

Online Mode (ComfyUI Running)

Full API access. Preferred mode for interactive work.

1. Test connection: GET /system_stats
2. Discover capabilities: Use comfyui-inventory skill
3. Queue workflow: POST /prompt
4. Poll for results: GET /history/{prompt_id} every 5 seconds
5. Retrieve outputs: GET /view?filename=...

Offline Mode (No Server)

Export workflow JSON for manual loading in ComfyUI.

1. Generate workflow JSON following ComfyUI's format
2. Save to projects/{project}/workflows/{name}.json
3. Instruct user to drag-drop into ComfyUI

API Operations

Check Server Status

curl http://127.0.0.1:8188/system_stats

Response fields:

• system.os: Operating system
• system.comfyui_version: Version string
• devices[0].name: GPU name
• devices[0].vram_total: Total VRAM bytes
• devices[0].vram_free: Free VRAM bytes

Queue a Workflow

curl -X POST http://127.0.0.1:8188/prompt \
  -H "Content-Type: application/json" \
  -d '{"prompt": WORKFLOW_JSON, "client_id": "video-agent"}'

WORKFLOW_JSON format:

{
  "1": {
    "class_type": "LoadCheckpoint",
    "inputs": {
      "ckpt_name": "flux1-dev.safetensors"
    }
  },
  "2": {
    "class_type": "CLIPTextEncode",
    "inputs": {
      "text": "photorealistic portrait...",
      "clip": ["1", 1]
    }
  }
}

Each node is keyed by a string ID. Inputs reference other nodes as ["{node_id}", {output_index}].

Response:

{"prompt_id": "abc-123-def", "number": 1}

Poll for Completion

curl http://127.0.0.1:8188/history/abc-123-def

Incomplete: Returns {} (empty object) Complete: Returns execution data with outputs:

{
  "abc-123-def": {
    "outputs": {
      "9": {
        "images": [{"filename": "ComfyUI_00001.png", "subfolder": "", "type": "output"}]
      }
    },
    "status": {"completed": true}
  }
}

Retrieve Output Image

curl "http://127.0.0.1:8188/view?filename=ComfyUI_00001.png&subfolder=&type=output" -o output.png

Upload Reference Image

curl -X POST http://127.0.0.1:8188/upload/image \
  -F "image=@reference.png" \
  -F "subfolder=input" \
  -F "type=input"

Cancel Current Generation

curl -X POST http://127.0.0.1:8188/interrupt

Free VRAM

curl -X POST http://127.0.0.1:8188/free \
  -H "Content-Type: application/json" \
  -d '{"unload_models": true}'

Polling Strategy

ComfyUI doesn't support WebSocket in CLI context. Use REST polling:

1. Queue workflow via POST /prompt → get prompt_id
2. Poll GET /history/{prompt_id} every 5 seconds
3. On empty response: generation in progress, continue polling
4. On populated response: check status.completed
5. If completed: true, extract outputs
6. If error in status, route to comfyui-troubleshooter

Timeout: Warn user after 10 minutes of polling. Video generation (Wan 14B) can take 15-30 minutes.

Workflow Validation

Before queuing any workflow:

1. Read state/inventory.json (via comfyui-inventory)
2. For each node in workflow: verify class_type exists in installed nodes
3. For each model reference: verify file exists in installed models
4. Flag missing items with:
   • Node: suggest ComfyUI-Manager install command
   • Model: provide download link from references/models.md
   • Version mismatch: suggest update

Error Handling

| Error | Cause | Action | |-------|-------|--------| | Connection refused | ComfyUI not running | Switch to offline mode, save JSON | | 400 Bad Request | Invalid workflow JSON | Validate node connections | | 500 Internal Error | ComfyUI crash | Suggest restart, check logs | | Timeout (no response) | Server overloaded | Wait and retry once |

Reference

Full API documentation: foundation/api-quick-ref.md