fix: subgraph output slot labels not updating in v2 renderer (#9266)

## Summary

Custom names set on subgraph output nodes are ignored in the v2 renderer
— it always shows the data type name (e.g. "texts") instead of the
user-defined label. Works correctly in v1.

## Changes

- **What**: Made `outputs` in `extractVueNodeData` reactive via
`shallowReactive` + `defineProperty` (matching the existing `inputs`
pattern). Added a `node:slot-label:changed` graph trigger that
`SubgraphNode` fires when input/output labels are renamed, so the Vue
layer picks up the change.

## Review Focus

- The `outputs` reactivity mirrors `inputs` exactly — same
`shallowReactive` + setter pattern. The new trigger event forces
`shallowReactive` to detect the deep property change by re-assigning the
array.
- Also handles input label renames for consistency, even though the
current bug report is output-specific.

## Screenshots

**v1 — output correctly shows custom label "output_text":**
<img width="1076" height="628" alt="Screenshot 2026-02-26 at 4 43 00 PM"
src="https://github.com/user-attachments/assets/b4d6ae4c-9970-4d99-a872-4ce1b28522f2"
/>

**v2 before fix — output shows type name "texts" instead of custom
label:**
<img width="808" height="298" alt="Screenshot 2026-02-26 at 4 43 30 PM"
src="https://github.com/user-attachments/assets/cf06aa6c-6d4d-4be9-9bcd-dcc072ed1907"
/>

**v2 after fix — output correctly shows "output_text":**
<img width="1013" height="292" alt="Screenshot 2026-02-26 at 5 14 44 PM"
src="https://github.com/user-attachments/assets/3c43fa9b-0615-4758-bee6-be3481168675"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9266-fix-subgraph-output-slot-labels-not-updating-in-v2-renderer-3146d73d365081979327fd775a6ef62b)
by [Unito](https://www.unito.io)

src/composables/graph/useGraphNodeManager.test.ts

@@ -243,6 +243,78 @@ describe('Widget slotMetadata reactivity on link disconnect', () => {
   })
 })
 
+describe('Subgraph output slot label reactivity', () => {
+  beforeEach(() => {
+    setActivePinia(createTestingPinia({ stubActions: false }))
+  })
+
+  it('updates output slot labels when node:slot-label:changed is triggered', async () => {
+    const graph = new LGraph()
+    const node = new LGraphNode('test')
+    node.addOutput('original_name', 'STRING')
+    node.addOutput('other_name', 'STRING')
+    graph.add(node)
+
+    const { vueNodeData } = useGraphNodeManager(graph)
+    const nodeId = String(node.id)
+    const nodeData = vueNodeData.get(nodeId)
+    if (!nodeData?.outputs) throw new Error('Expected output data to exist')
+
+    expect(nodeData.outputs[0].label).toBeUndefined()
+    expect(nodeData.outputs[1].label).toBeUndefined()
+
+    // Simulate what SubgraphNode does: set the label, then fire the trigger
+    node.outputs[0].label = 'custom_label'
+    graph.trigger('node:slot-label:changed', {
+      nodeId: node.id,
+      slotType: NodeSlotType.OUTPUT
+    })
+
+    await nextTick()
+
+    const updatedData = vueNodeData.get(nodeId)
+    expect(updatedData?.outputs?.[0]?.label).toBe('custom_label')
+    expect(updatedData?.outputs?.[1]?.label).toBeUndefined()
+  })
+
+  it('updates input slot labels when node:slot-label:changed is triggered', async () => {
+    const graph = new LGraph()
+    const node = new LGraphNode('test')
+    node.addInput('original_name', 'STRING')
+    graph.add(node)
+
+    const { vueNodeData } = useGraphNodeManager(graph)
+    const nodeId = String(node.id)
+    const nodeData = vueNodeData.get(nodeId)
+    if (!nodeData?.inputs) throw new Error('Expected input data to exist')
+
+    expect(nodeData.inputs[0].label).toBeUndefined()
+
+    node.inputs[0].label = 'custom_label'
+    graph.trigger('node:slot-label:changed', {
+      nodeId: node.id,
+      slotType: NodeSlotType.INPUT
+    })
+
+    await nextTick()
+
+    const updatedData = vueNodeData.get(nodeId)
+    expect(updatedData?.inputs?.[0]?.label).toBe('custom_label')
+  })
+
+  it('ignores node:slot-label:changed for unknown node ids', () => {
+    const graph = new LGraph()
+    useGraphNodeManager(graph)
+
+    expect(() =>
+      graph.trigger('node:slot-label:changed', {
+        nodeId: 'missing-node',
+        slotType: NodeSlotType.OUTPUT
+      })
+    ).not.toThrow()
+  })
+})
+
 describe('Subgraph Promoted Pseudo Widgets', () => {
   beforeEach(() => {
     setActivePinia(createTestingPinia({ stubActions: false }))

src/composables/graph/useGraphNodeManager.ts

@@ -396,7 +396,9 @@ export function extractVueNodeData(node: LGraphNode): VueNodeData {
       },
       set(v) {
         reactiveWidgets.splice(0, reactiveWidgets.length, ...v)
-      }
+      },
+      configurable: true,
+      enumerable: true
     })
   }
   const reactiveInputs = shallowReactive<INodeInputSlot[]>(node.inputs ?? [])
@@ -406,7 +408,20 @@ export function extractVueNodeData(node: LGraphNode): VueNodeData {
     },
     set(v) {
       reactiveInputs.splice(0, reactiveInputs.length, ...v)
-    }
+    },
+    configurable: true,
+    enumerable: true
+  })
+  const reactiveOutputs = shallowReactive<INodeOutputSlot[]>(node.outputs ?? [])
+  Object.defineProperty(node, 'outputs', {
+    get() {
+      return reactiveOutputs
+    },
+    set(v) {
+      reactiveOutputs.splice(0, reactiveOutputs.length, ...v)
+    },
+    configurable: true,
+    enumerable: true
   })
 
   const safeWidgets = reactiveComputed<SafeWidgetData[]>(() => {
@@ -448,7 +463,7 @@ export function extractVueNodeData(node: LGraphNode): VueNodeData {
     hasErrors: !!node.has_errors,
     widgets: safeWidgets,
     inputs: reactiveInputs,
-    outputs: node.outputs ? [...node.outputs] : undefined,
+    outputs: reactiveOutputs,
     flags: node.flags ? { ...node.flags } : undefined,
     color: node.color || undefined,
     bgcolor: node.bgcolor || undefined,
@@ -746,6 +761,20 @@ export function useGraphNodeManager(graph: LGraph): GraphNodeManager {
         if (slotLinksEvent.slotType === NodeSlotType.INPUT) {
           refreshNodeSlots(String(slotLinksEvent.nodeId))
         }
+      },
+      'node:slot-label:changed': (slotLabelEvent) => {
+        const nodeId = String(slotLabelEvent.nodeId)
+        const nodeRef = nodeRefs.get(nodeId)
+        if (!nodeRef) return
+
+        // Force shallowReactive to detect the deep property change
+        // by re-assigning the affected array through the defineProperty setter.
+        if (slotLabelEvent.slotType !== NodeSlotType.OUTPUT && nodeRef.inputs) {
+          nodeRef.inputs = [...nodeRef.inputs]
+        }
+        if (slotLabelEvent.slotType !== NodeSlotType.INPUT && nodeRef.outputs) {
+          nodeRef.outputs = [...nodeRef.outputs]
+        }
       }
     }
 
@@ -760,6 +789,9 @@ export function useGraphNodeManager(graph: LGraph): GraphNodeManager {
         case 'node:slot-links:changed':
           triggerHandlers['node:slot-links:changed'](event)
           break
+        case 'node:slot-label:changed':
+          triggerHandlers['node:slot-label:changed'](event)
+          break
       }
 
       // Chain to original handler

src/lib/litegraph/src/LGraph.ts

@@ -1336,7 +1336,8 @@ export class LGraph
     const validEventTypes = new Set([
       'node:slot-links:changed',
       'node:slot-errors:changed',
-      'node:property:changed'
+      'node:property:changed',
+      'node:slot-label:changed'
     ])
 
     if (validEventTypes.has(action) && param && typeof param === 'object') {

src/lib/litegraph/src/subgraph/SubgraphNode.ts

@@ -27,6 +27,7 @@ import type {
   ExportedSubgraphInstance,
   ISerialisedNode
 } from '@/lib/litegraph/src/types/serialisation'
+import { NodeSlotType } from '@/lib/litegraph/src/types/globalEnums'
 import type { IBaseWidget } from '@/lib/litegraph/src/types/widgets'
 import type { UUID } from '@/lib/litegraph/src/utils/uuid'
 import {
@@ -441,6 +442,10 @@ export class SubgraphNode extends LGraphNode implements BaseLGraph {
         if (input._widget) {
           input._widget.label = newName
         }
+        this.graph?.trigger('node:slot-label:changed', {
+          nodeId: this.id,
+          slotType: NodeSlotType.INPUT
+        })
       },
       { signal }
     )
@@ -453,6 +458,10 @@ export class SubgraphNode extends LGraphNode implements BaseLGraph {
         if (!output) throw new Error('Subgraph output not found')
 
         output.label = newName
+        this.graph?.trigger('node:slot-label:changed', {
+          nodeId: this.id,
+          slotType: NodeSlotType.OUTPUT
+        })
       },
       { signal }
     )

src/lib/litegraph/src/types/graphTriggers.ts

@@ -23,10 +23,17 @@ interface NodeSlotLinksChangedEvent {
   linkId: number
 }
 
+interface NodeSlotLabelChangedEvent {
+  type: 'node:slot-label:changed'
+  nodeId: NodeId
+  slotType?: NodeSlotType
+}
+
 export type LGraphTriggerEvent =
   | NodePropertyChangedEvent
   | NodeSlotErrorsChangedEvent
   | NodeSlotLinksChangedEvent
+  | NodeSlotLabelChangedEvent
 
 export type LGraphTriggerAction = LGraphTriggerEvent['type']