Comfyui Frontend Extensions

ComfyUI v2 Frontend Extension API

The v2 extension API is the published npm package @comfyorg/extension-api. It replaces the legacy app.registerExtension() / nodeType.prototype monkey-patching model with a typed, tree-shakeable, import-based API.

If you are converting an existing v1 extension, read references/migrate-v1-to-v2.md for a pattern-by-pattern mapping.

Mental model

Core principles baked into the API:

• Import, don't reach for globals. import { defineNode } from '@comfyorg/extension-api'. No window.app dependency at module evaluation time.
• Read via getters, write via command-dispatch setters. getValue() reads; setValue() dispatches an undo-able, serializable command. Read-only invariants (set at construction) are readonly accessors (node.type, widget.name).
• Observe via typed on(...) subscriptions. Each returns an Unsubscribe cleanup function. No Vue refs/signals are ever exposed — Vue reactivity is the internal engine only.
• Everything is disposable. Every defineX returns a DisposableHandle with an idempotent, synchronous dispose().

Registration entry points

All imported from @comfyorg/extension-api:

Imperative carve-outs (fire-and-forget, NOT defineX, no handle): toast, notify.

A single extension file typically exports a default defineExtension/defineNode result and calls the shell-UI defineX functions inside setup() (or at module scope — they queue safely before the app boots).

defineNode — the primary entry point

Reacts to node lifecycle. nodeCreated fires once per node instance (typed in, pasted, duplicated, or loaded without an existing workflow). loadedGraphNode fires once when a node is restored from a saved workflow (widget values already populated). Exactly one of them fires per node entity — never both.

import { defineNode, onNodeMounted, onNodeRemoved } from '@comfyorg/extension-api'

export default defineNode({
  name: 'my-org.executed-logger',
  // Filter to specific comfyClass names. Omit to receive every node type.
  nodeTypes: ['KSampler', 'KSamplerAdvanced'],

  // MUST be synchronous. Runs inside a Vue EffectScope; everything registered
  // here (subscriptions, onNodeMounted) auto-disposes when the node is removed.
  nodeCreated(node) {
    // Read-only invariants
    console.log(node.type, node.comfyClass, node.id)

    // Subscribe to backend execution completion (replaces onExecuted patching)
    node.on('executed', (e) => {
      console.log('output:', e.output) // Record<string, unknown>
    })

    // Lifecycle hooks — call SYNCHRONOUSLY (never after an await)
    onNodeMounted(() => {
      // Node fully mounted; DOM/canvas ready.
    })
    onNodeRemoved(() => {
      // Cleanup: abort fetches, close sockets. Does NOT fire on subgraph promotion.
    })
  },

  loadedGraphNode(node) {
    // Node restored from a saved workflow; widget values are already set.
  }
})

NodeHandle surface (Phase A)

Position/size/title/mode getters and slot/connection events are deferred in Phase A (excluded per the project's AXIOMS). Do not rely on getPosition, setSize, getMode, on('connected'), etc. — they are not yet on the surface.

Nodes cannot enumerate or reference their widgets (node.getWidget(name) was removed). To attach per-widget behavior, register a widget type with defineWidget and use the mount context's ctx.widget handle.

defineExtension — app lifecycle + shell UI

Use for app-wide setup and to host shell-UI registrations. setup() runs at the early registration point; use the imported onMounted hook for work that needs the app fully initialized.

import {
  defineExtension,
  onMounted,
  onUnmounted,
  execution,
  toast
} from '@comfyorg/extension-api'

export default defineExtension({
  name: 'my-org.my-extension',
  setup() {
    // Register late-lifecycle work via onMounted (called synchronously here).
    onMounted(() => {
      const off = execution.on('start', () => {
        toast.show({ severity: 'info', summary: 'Run started' })
      })
      onUnmounted(off) // tidy teardown
    })
  }
})

setup() signature note. The source-of-truth surface uses implicit-context hooks: import onMounted/onNodeMounted/etc. and call them synchronously inside setup() (mirrors Vue's Composition API). An early package draft showed a setup(ctx) { ctx.onNodeMounted(...) } context-argument style; prefer the imported-hook form above, which is what the current API exports.

Context-scoped lifecycle hooks are imported and called synchronously inside defineExtension's setup(): onBeforeMount, onMounted, onUnmounted, onActivated, onDeactivated. Note: defineSidebarTab/defineBottomPanelTab take no setup field — don't add one (it's a type error). onActivated/onDeactivated fire when the surrounding tab/panel is shown/hidden.

defineWidget — custom widget types with DOM

Widgets are declared in the Python node's INPUT_TYPES, never created at runtime (node.addWidget is forbidden). defineWidget registers a type and the DOM mount hook the runtime invokes against a host <div> it owns. mount is optional — omit it for value-only widgets that render through the native renderer.

import { defineWidget, type WidgetCleanup } from '@comfyorg/extension-api'

export default defineWidget({
  name: 'my-org.color-picker',
  type: 'COLOR_PICKER', // referenced from Python INPUT_TYPES

  // The SOLE DOM seam. Capture host + constructed DOM via closure — there is
  // no widget.element accessor.
  mount(host, ctx): WidgetCleanup {
    const input = document.createElement('input')
    input.type = 'color'
    input.value = String(ctx.widget.getValue() ?? '#000000')
    input.addEventListener('input', () => ctx.widget.setValue(input.value))
    host.appendChild(input)

    // ctx.widget / ctx.node are the only legal handles here.
    ctx.widget.on('valueChange', (e) => {
      input.value = String(e.newValue ?? '#000000')
    })

    // Optional cleanup — fires once on widget destruction (NOT on host remount).
    return () => input.remove()
  }
})

WidgetMountContext also exposes onUnmount(fn), onBeforeRemount(fn), and onAfterRemount(fn => ...) for host-move scenarios (graph↔app mode, subgraph promotion). The mount body is not re-invoked across a remount — only the remount hooks fire.

WidgetHandle surface

// Serialization override (the SOLE serialization interface in v2):
widget.on('beforeSerialize', (e) => {
  e.setSerializedValue(processDynamicPrompt(widget.getValue()))
})

// Async serialization (e.g. capture a webcam frame before queueing):
widget.on('beforeSerialize', async (e) => {
  e.setSerializedValue(await captureFrame())
})

// Pre-queue validation (replaces app.queuePrompt monkey-patching):
widget.on('beforeQueue', (e) => {
  if (!widget.getValue()) e.reject('Prompt text is required before queueing.')
})

Typed event namespaces

Four module-level singletons replace api.addEventListener('...'). Each on() returns an Unsubscribe. Subscriptions made inside a setup() body auto-dispose on unmount; subscriptions made elsewhere are the caller's responsibility.

import { execution, server } from '@comfyorg/extension-api'

const off = execution.on('progress', (e) => console.log('progress', e))
// Custom-node events ride the `server` namespace with arbitrary names:
server.on('my-org.my-node.update', (e) => console.log(e))
// later:
off()

Payloads default to unknown today. Narrow them with TS module augmentation:

declare module '@comfyorg/extension-api' {
  interface ExecutionEventPayloads {
    start: { promptId: string }
    progress: { value: number; max: number }
  }
  interface ServerEventPayloads {
    'my-org.my-node.update': { nodeId: string; text: string }
  }
}

The augmentable interfaces are GraphEventPayloads, ExecutionEventPayloads, ServerEventPayloads, and WorkbenchEventPayloads.

Shell UI registrations

Each returns a DisposableHandle. Safe to call at module scope (they queue until the app boots) or inside setup().

import {
  defineCommand,
  defineHotkey,
  defineToolbarButton,
  defineSetting,
  defineAboutBadge
} from '@comfyorg/extension-api'

// Command — id, function, optional label/icon/tooltip.
const cmd = defineCommand({
  id: 'my-org.do-the-thing',
  label: 'Do The Thing',
  function: () => { /* ... */ }
})

// Hotkey — binds a key combo to an already-registered command id.
// `mod` = cmd on macOS, ctrl elsewhere.
defineHotkey({ keys: 'mod+shift+k', commandId: 'my-org.do-the-thing' })

// Action-bar button — id (for dispose), icon, onClick.
defineToolbarButton({
  id: 'my-org.help',
  icon: 'pi-question-circle',
  tooltip: 'Get help',
  onClick: () => openHelp()
})

// Setting — widen the id when not augmenting the Settings keymap.
defineSetting({
  id: 'my-org.enabled' as never,
  name: 'Enable my extension',
  type: 'boolean',
  defaultValue: false
})

// About-page badge.
defineAboutBadge({
  label: 'GitHub',
  url: 'https://github.com/me/my-ext',
  icon: 'pi-github'
})

// Tear down any registration:
cmd.dispose() // idempotent + synchronous

CommandDefinition fields: id (required), function: (metadata?) => void | Promise<void> (required), optional label / icon / tooltip (each string | (() => string)), menubarLabel, versionAdded.

defineSidebarTab — embedded panels (e.g. a chat panel)

A sidebar tab is the substrate for a rich embedded UI such as a chat panel. Two flavors: type: 'vue' (mount a Vue component) or type: 'custom' (imperative render(container) / destroy()). Both share the base fields id, title, optional icon, iconBadge, tooltip, label.

Vue component tab

import { defineSidebarTab } from '@comfyorg/extension-api'
import ChatPanel from './ChatPanel.vue'

const chatTab = defineSidebarTab({
  id: 'my-org.chat',
  title: 'Chat',
  type: 'vue',
  icon: 'pi-comments',
  component: ChatPanel
})
// chatTab.dispose() removes the tab.

Custom (framework-free) chat panel

When you don't want a Vue dependency, use type: 'custom' and build the DOM yourself. render receives the container; destroy is your teardown.

import {
  defineExtension,
  defineSidebarTab,
  execution,
  server,
  type Unsubscribe
} from '@comfyorg/extension-api'

export default defineExtension({
  name: 'my-org.chat-panel',
  setup() {
    const subscriptions: Unsubscribe[] = []

    defineSidebarTab({
      id: 'my-org.chat',
      title: 'Chat',
      type: 'custom',
      icon: 'pi-comments',

      render(container: HTMLElement) {
        const log = document.createElement('div')
        log.className = 'chat-log'

        const form = document.createElement('form')
        const input = document.createElement('input')
        input.placeholder = 'Ask something…'
        const send = document.createElement('button')
        send.type = 'submit'
        send.textContent = 'Send'
        form.append(input, send)

        const append = (who: string, text: string) => {
          const line = document.createElement('p')
          line.textContent = `${who}: ${text}`
          log.appendChild(line)
          log.scrollTop = log.scrollHeight
        }

        form.addEventListener('submit', (ev) => {
          ev.preventDefault()
          const text = input.value.trim()
          if (!text) return
          append('You', text)
          input.value = ''
          // Forward to a backend node/server event, stream the reply, etc.
        })

        container.append(log, form)

        // Stream backend replies via the server namespace (custom-node event).
        subscriptions.push(
          server.on('my-org.chat.reply', (e) => append('Assistant', String(e)))
        )
        // React to runs to show status in the panel.
        subscriptions.push(
          execution.on('start', () => append('System', 'Run started…'))
        )
      },

      destroy() {
        for (const off of subscriptions) off()
        subscriptions.length = 0
      }
    })
  }
})

defineBottomPanelTab has the same vue / custom shapes (base fields id, optional title/titleKey, optional targetPanel: 'terminal' | 'shortcuts').

Toasts

toast and notify are inline imperative (no defineX, no handle). Call from any setup() body or hook closure.

import { toast } from '@comfyorg/extension-api'

toast.show({ severity: 'error', summary: 'Workflow failed', detail: err.message, life: 4000 })
toast.removeAll()

notify({ kind, message, detail, life }) is a deprecated 1:1 wrapper over toast.show — prefer toast.show directly.

Node identity helpers

For referencing nodes across subgraph boundaries or execution runs, use the branded identity primitives rather than raw integer node IDs:

import {
  createNodeLocatorId, parseNodeLocatorId, isNodeLocatorId,
  createNodeExecutionId, parseNodeExecutionId, isNodeExecutionId,
  type NodeLocatorId, type NodeExecutionId
} from '@comfyorg/extension-api'

const locator: NodeLocatorId = createNodeLocatorId(subgraphUuid, localNodeId)
// NodeExecutionId encodes a node's path through nested subgraphs as an array of node ids
// (joined with ':'). Pass the array, not positional args:
const execId: NodeExecutionId = createNodeExecutionId([localNodeId])

if (isNodeLocatorId(maybe)) {
  // parseNodeLocatorId returns { subgraphUuid: string | null; localNodeId: NodeId }
  const { subgraphUuid, localNodeId } = parseNodeLocatorId(maybe)
}

NodeLocatorId arrives from workflow JSON; NodeExecutionId arrives from websocket frames. You receive these from event payloads — that's why they're public (unlike the internal *EntityId brands, which are not exported).

Disposal contract

Every defineX returns DisposableHandle { dispose(): void }:

• Idempotent — calling dispose() again is a safe no-op.
• Synchronous — teardown happens synchronously inside dispose().
• Independent — disposing handle A does not affect B or C. Sequence calls explicitly when teardown order matters (e.g. drop a hotkey before its command).
• Pre-mount safe — disposing before the app boots removes the spec from the pending queue so it never mounts.

const handles = [
  defineCommand({ id: 'my.cmd', function: () => {} }),
  defineHotkey({ keys: 'mod+k', commandId: 'my.cmd' }),
  defineSidebarTab({ id: 'my.tab', title: 'Tab', type: 'vue', component: MyTab })
]
// Full teardown:
for (const h of handles.reverse()) h.dispose()

Common mistakes

1. Calling lifecycle hooks after await. onNodeMounted / onMounted / onUnmounted rely on implicit scope context and must be called synchronously inside the setup()/nodeCreated body. After an await the scope is gone — throws in dev, silent no-op in prod. Kick off async work in the body, but register hooks first.
2. Reaching for window.app or app.*. v2 has no window.app dependency at module-eval time. Import everything from @comfyorg/extension-api.
3. Patching nodeType.prototype. Replaced by defineNode + node.on(...). Prototype patching does not interoperate with the v2 handle model.
4. Mutating reads. node.getInputs(), widget.options, and Point/Size tuples are frozen/Readonly — assignment raises TS errors. Use the setter methods (widget.setOption, widget.setValue).
5. Assigning widget.value / widget.callback / widget.serializeValue. Use setValue(), on('valueChange'), and on('beforeSerialize'). serializeValue is read-only on the v2 surface.
6. Trying to disable widget serialization. There is no serialize: false and no skip() in v2. If a widget should not contribute to the payload, it should not be a widget. The only serialization interface is widget.on('beforeSerialize', fn) + e.setSerializedValue(v).
7. Creating widgets at runtime. node.addWidget(...) / node.addDOMWidget(...) are removed. Declare widgets in the Python INPUT_TYPES; render custom DOM via defineWidget({ mount }).
8. Enumerating widgets from a node. node.getWidget(name) / node.getWidgets() were removed (nodes cannot reference widgets). Use a defineWidget mount context's ctx.widget, or share state via the server event bus.
9. Using node-level beforeSerialize. Deprecated (ADR-0010). Store extension state in a widget and use widget-level beforeSerialize.
10. Forgetting to dispose. Long-lived subscriptions made outside a setup() context, and every defineX handle, leak unless you call the returned Unsubscribe / dispose(). Inside setup() they auto-dispose on unmount.
11. Relying on deferred Phase A surface. Position/size/title/mode getters and slot/connection events are not yet exported. Don't write code against them.

Source: artokun/comfyui-mcp — distributed by TomeVault.