fix(media): send ElevenLabs TTS text under the field fal requires

apps/sim/lib/media/falai-audio.ts

@@ -55,8 +55,9 @@ function buildInput(
 ): Record<string, unknown> {
   const input: Record<string, unknown> = {}
   if (type === 'speech') {
-    // Gemini 3.1 Flash TTS takes the text (with optional inline tags) in `prompt`.
-    input.prompt = params.prompt
+    // ElevenLabs TTS requires `text`; Gemini 3.1 Flash TTS takes the text (with optional inline tags) in `prompt`.
+    if (model.includes('elevenlabs/tts')) input.text = params.prompt
+    else input.prompt = params.prompt
     if (params.voice) input.voice = params.voice
   } else if (type === 'sfx') {
     // ElevenLabs sound-effects take `text`.

apps/sim/lib/media/falai.test.ts

@@ -399,3 +399,41 @@ describe('billing a fal generation', () => {
     expect(onCost).not.toHaveBeenCalled()
   })
 })
+
+describe('the speech request fal receives', () => {
+  beforeEach(() => {
+    vi.stubEnv('FALAI_API_KEY', 'key')
+  })
+
+  /** fal validates the submit body and rejects it; the stub records what was submitted. */
+  function stubRejectingFalSubmit() {
+    const submitted: Array<{ url: string; body: unknown }> = []
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(async (url: string, init: RequestInit = {}) => {
+        submitted.push({ url, body: JSON.parse(String(init.body)) })
+        return jsonResponse({ detail: 'rejected by stub' }, 422)
+      })
+    )
+    return submitted
+  }
+
+  it.each([
+    ['fal-ai/elevenlabs/tts/eleven-v3', { text: 'Hello there', voice: 'Aria' }],
+    ['fal-ai/elevenlabs/tts/multilingual-v2', { text: 'Hello there', voice: 'Aria' }],
+    [undefined, { prompt: 'Hello there', voice: 'Aria' }],
+  ])('submits the text %s requires', async (model, expectedBody) => {
+    const submitted = stubRejectingFalSubmit()
+
+    await expect(
+      generateFalAudio({ prompt: 'Hello there', voice: 'Aria', model, onCost: vi.fn() })
+    ).rejects.toThrow()
+
+    expect(submitted).toEqual([
+      {
+        url: `https://queue.fal.run/${model ?? 'fal-ai/gemini-3.1-flash-tts'}`,
+        body: expectedBody,
+      },
+    ])
+  })
+})