fix(video): reject a reference file that is not an image before submitting

An agent can pass any file as the start frame or Runway reference, and
nothing checked its type before the paid request. Validation now returns
a 400 for a non-image `visualReference` before the file is downloaded.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: myxamediyar

apps/sim/lib/internal/video/client.test.ts

@@ -513,6 +513,32 @@ describe('Video provider client', () => {
     )
   })
 
+  it.each([
+    { provider: 'falai' as const, model: 'kling-v3-pro' },
+    { provider: 'runway' as const, model: 'gen4_turbo' },
+  ])(
+    'rejects a non-image reference file for $provider before submitting',
+    ({ provider, model }) => {
+      const pdf = {
+        id: 'f',
+        name: 'brief.pdf',
+        url: '',
+        size: 3,
+        type: 'application/pdf',
+        key: 'k',
+      }
+      expect(
+        getVideoInputValidationError({
+          provider,
+          apiKey: 'key',
+          model,
+          prompt: 'Pan left',
+          visualReference: pdf,
+        })
+      ).toBe('Reference image must be an image file, not application/pdf')
+    }
+  )
+
   it('rejects a start frame for a fal model without an image-to-video endpoint', () => {
     const frame = { id: 'f', name: 'frame.png', url: '', size: 3, type: 'image/png', key: 'k' }
     expect(

apps/sim/lib/internal/video/client.ts

@@ -94,6 +94,8 @@ async function waitForProvider(context: VideoGenerationContext): Promise<void> {
 }
 
 export function getVideoInputValidationError(input: VideoGenerationInput): string | undefined {
+  if (input.visualReference && !input.visualReference.type.toLowerCase().startsWith('image/'))
+    return `Reference image must be an image file, not ${input.visualReference.type || 'an unknown type'}`
   if (input.provider === 'falai') {
     if (input.prompt.length < 3 || input.prompt.length > 2000)
       return 'Prompt must be between 3 and 2000 characters'