diff --git a/src/types/apiTypes.ts b/src/types/apiTypes.ts
index 5ca51c9be..4246f5b2f 100644
--- a/src/types/apiTypes.ts
+++ b/src/types/apiTypes.ts
@@ -1,8 +1,7 @@
 import { ZodType, z } from 'zod'
-import { zComfyWorkflow } from './comfyWorkflow'
+import { zComfyWorkflow, zNodeId } from './comfyWorkflow'
 import { fromZodError } from 'zod-validation-error'
 
-const zNodeId = z.union([z.number(), z.string()])
 const zNodeType = z.string()
 const zQueueIndex = z.number()
 const zPromptId = z.string()
diff --git a/src/types/comfyWorkflow.ts b/src/types/comfyWorkflow.ts
index 519a1c69d..6e3b6453f 100644
--- a/src/types/comfyWorkflow.ts
+++ b/src/types/comfyWorkflow.ts
@@ -1,6 +1,20 @@
 import { z } from 'zod'
 import { fromZodError } from 'zod-validation-error'
 
+// GroupNode is hacking node id to be a string, so we need to allow that.
+// innerNode.id = `${this.node.id}:${i}`
+// Remove it after GroupNode is redesigned.
+export const zNodeId = z.union([z.number().int(), z.string()])
+export const zSlotIndex = z.union([
+  z.number().int(),
+  z
+    .string()
+    .transform((val) => parseInt(val))
+    .refine((val) => !isNaN(val), {
+      message: 'Invalid number'
+    })
+])
+
 // Definition of an AI model file used in the workflow.
 const zModelFile = z.object({
   name: z.string(),
@@ -12,10 +26,10 @@ const zModelFile = z.object({
 
 const zComfyLink = z.tuple([
   z.number(), // Link id
-  z.number(), // Node id of source node
-  z.number(), // Output slot# of source node
-  z.number(), // Node id of destination node
-  z.number(), // Input slot# of destination node
+  zNodeId, // Node id of source node
+  zSlotIndex, // Output slot# of source node
+  zNodeId, // Node id of destination node
+  zSlotIndex, // Input slot# of destination node
   z.string() // Data type
 ])
 
@@ -24,7 +38,7 @@ const zNodeOutput = z
     name: z.string(),
     type: z.string(),
     links: z.array(z.number()).nullable(),
-    slot_index: z.number().optional()
+    slot_index: zSlotIndex.optional()
   })
   .passthrough()
 
@@ -33,7 +47,7 @@ const zNodeInput = z
     name: z.string(),
     type: z.string(),
     link: z.number().nullable(),
-    slot_index: z.number().optional()
+    slot_index: zSlotIndex.optional()
   })
   .passthrough()
 
@@ -62,7 +76,7 @@ const zWidgetValues = z.union([z.array(z.any()), z.record(z.any())])
 
 const zComfyNode = z
   .object({
-    id: z.number(),
+    id: zNodeId,
     type: z.string(),
     pos: zVector2,
     size: zVector2,
@@ -123,7 +137,7 @@ const zExtra = z
 
 export const zComfyWorkflow = z
   .object({
-    last_node_id: z.number(),
+    last_node_id: zNodeId,
     last_link_id: z.number(),
     nodes: z.array(zComfyNode),
     links: z.array(zComfyLink),
diff --git a/tests-ui/tests/comfyWorkflow.test.ts b/tests-ui/tests/comfyWorkflow.test.ts
index 597ff1374..bcb729d33 100644
--- a/tests-ui/tests/comfyWorkflow.test.ts
+++ b/tests-ui/tests/comfyWorkflow.test.ts
@@ -88,4 +88,20 @@ describe('parseComfyWorkflow', () => {
     const validatedWorkflow = await validateComfyWorkflow(workflow)
     expect(validatedWorkflow.nodes[0].widgets_values).toEqual({ foo: 'bar' })
   })
+
+  it('workflow.links', async () => {
+    const workflow = JSON.parse(JSON.stringify(defaultGraph))
+
+    workflow.links = [
+      [
+        1, // Link id
+        '100:1', // Node id of source node
+        '12', // Output slot# of source node
+        '100:2', // Node id of destination node
+        15, // Input slot# of destination node
+        'INT' // Data type
+      ]
+    ]
+    expect(await validateComfyWorkflow(workflow)).not.toBeNull()
+  })
 })