fix(video): use a real Veo model id (was 404ing on a fabricated id)

Generation 404'd: POST …/models/{model}:predictLongRunning returned Not Found
because the default model id `veo-3.1-fast-generate-001` does not exist. It was
introduced based on a review note to "migrate 3.0-fast → 3.1-fast", but the real
Gemini Veo ids (per the @ai-sdk/google VideoModelId union) are
veo-3.0-fast-generate-001 (stable) and veo-3.1-fast-generate-preview (preview) —
there is no `-3.1-fast-…-001`.

- Default back to the stable `veo-3.0-fast-generate-001`; register
  `veo-3.1-fast-generate-preview` as the newer option (both real ids).
- Surface a specific error on a 404 ("Video model X is unavailable for this API
  key") instead of the generic "request failed", and log the model id.
- Add a test asserting the default id is actually registered as video-capable,
  so a fabricated/typo'd id can't regress silently.

Gate green: tsc/eslint/prettier, 1247 vitest, build.

Author: komod0

.env.example

@@ -43,7 +43,8 @@ ELEVENLABS_API_KEY=
 # AI_IMAGE_MODEL=
 # Where generated images are written on disk (default: .data/images/):
 # A2UI_IMAGE_DIR=
-# Pin the on-demand video model (default veo-3.1-fast-generate-001). Video uses
+# Pin the on-demand video model (default veo-3.0-fast-generate-001; the 3.1 fast
+# model is preview-suffixed: veo-3.1-fast-generate-preview). Video uses
 # the same GOOGLE_GENERATIVE_AI_API_KEY / GEMINI_API_KEY as images; it is ONLY
 # generated on demand (Video Lab + explicit per-component button), never bundled
 # into UI generation, because each Veo clip is comparatively expensive:

src/lib/ai/model-registry.ts

@@ -316,12 +316,13 @@ export const MODEL_REGISTRY: Record<string, ModelInfo> = {
   },
   // Veo Fast — long-running text→video. On-demand ONLY (Video Lab + explicit
   // per-component button); deliberately never invoked during UI/chat generation
-  // the way images are, because each clip is comparatively expensive. 3.1-fast
-  // is the current default; 3.0-fast is kept registered for back-compat but is
-  // discontinued by Google on 2026-06-30, so the default points at 3.1.
-  "veo-3.1-fast-generate-001": {
-    id: "veo-3.1-fast-generate-001",
-    name: "Veo 3.1 Fast",
+  // the way images are, because each clip is comparatively expensive. Model ids
+  // here MUST match Google's actual Veo ids (the @ai-sdk/google VideoModelId
+  // union): the stable fast id is `veo-3.0-fast-generate-001` (the default); the
+  // 3.1 fast model is preview-suffixed (`veo-3.1-fast-generate-preview`).
+  "veo-3.0-fast-generate-001": {
+    id: "veo-3.0-fast-generate-001",
+    name: "Veo 3 Fast",
     provider: "google",
     capabilities: {
       chat: false,
@@ -332,9 +333,9 @@ export const MODEL_REGISTRY: Record<string, ModelInfo> = {
       tools: false,
     },
   },
-  "veo-3.0-fast-generate-001": {
-    id: "veo-3.0-fast-generate-001",
-    name: "Veo 3 Fast (legacy)",
+  "veo-3.1-fast-generate-preview": {
+    id: "veo-3.1-fast-generate-preview",
+    name: "Veo 3.1 Fast (preview)",
     provider: "google",
     capabilities: {
       chat: false,

src/lib/ai/video.test.ts

@@ -13,6 +13,7 @@ import {
   pollVideoOperation,
   downloadVideo,
 } from "./video";
+import { getModelInfo } from "./model-registry";
 
 describe("buildVideoPrompt", () => {
   it("folds the aesthetic's cinematic style into the prompt", () => {
@@ -32,16 +33,24 @@ describe("resolveVideoModel", () => {
     delete process.env.AI_VIDEO_MODEL;
   });
 
-  it("defaults to veo-3.1-fast-generate-001", () => {
-    expect(resolveVideoModel()).toBe("veo-3.1-fast-generate-001");
+  it("defaults to the stable veo-3.0-fast-generate-001 id", () => {
+    expect(resolveVideoModel()).toBe("veo-3.0-fast-generate-001");
+  });
+
+  it("defaults to a model that is actually registered as video-capable", () => {
+    // Guards against a fabricated/typo'd default id (a wrong id 404s on Veo).
+    const id = resolveVideoModel();
+    expect(getModelInfo(id)?.capabilities.videoGen).toBe(true);
   });
 
   it("honors an explicit video-capable model", () => {
-    expect(resolveVideoModel("veo-3.1-fast-generate-001")).toBe("veo-3.1-fast-generate-001");
+    expect(resolveVideoModel("veo-3.1-fast-generate-preview")).toBe(
+      "veo-3.1-fast-generate-preview"
+    );
   });
 
   it("ignores a non-video model id and falls back to the default", () => {
-    expect(resolveVideoModel("imagen-4.0-generate-001")).toBe("veo-3.1-fast-generate-001");
+    expect(resolveVideoModel("imagen-4.0-generate-001")).toBe("veo-3.0-fast-generate-001");
   });
 });
 
@@ -83,7 +92,7 @@ describe("video generation REST integration", () => {
     expect(result.ok).toBe(true);
     expect(result.operationName).toBe("operations/abc-123");
     const [url, init] = mockFetch.mock.calls[0];
-    expect(url).toContain("veo-3.1-fast-generate-001:predictLongRunning");
+    expect(url).toContain("veo-3.0-fast-generate-001:predictLongRunning");
     expect(init.headers["x-goog-api-key"]).toBe("k");
     const sent = JSON.parse(init.body);
     expect(sent.instances[0].prompt).toMatch(/neon alley/);

src/lib/ai/video.ts

@@ -27,9 +27,11 @@ import type { AestheticId } from "@/lib/aesthetic/types";
  */
 
 const BASE_URL = "https://generativelanguage.googleapis.com/v1beta";
-// Default to Veo 3.1 Fast: the 3.0-fast generation is discontinued by Google on
-// 2026-06-30, and 3.1-fast is its drop-in successor. Override with AI_VIDEO_MODEL.
-const DEFAULT_VIDEO_MODEL = "veo-3.1-fast-generate-001";
+// Default to Veo 3 Fast — the current stable fast model id on the Gemini API.
+// (The 3.1 fast model is preview-suffixed: `veo-3.1-fast-generate-preview`.)
+// Override with AI_VIDEO_MODEL. The id MUST be a real Gemini Veo id or the
+// predictLongRunning endpoint 404s.
+const DEFAULT_VIDEO_MODEL = "veo-3.0-fast-generate-001";
 
 /** Aspect ratios Veo accepts; anything else is dropped to the provider default. */
 const VEO_ASPECTS = new Set(["16:9", "9:16"]);
@@ -142,8 +144,15 @@ export async function startVideoGeneration(opts: {
 
     if (!res.ok) {
       const detail = await res.text().catch(() => "");
-      console.error("[Veo] start failed:", res.status, detail);
-      return { ok: false, status: res.status, error: "Video generation request failed" };
+      console.error("[Veo] start failed:", res.status, model, detail);
+      // 404 from predictLongRunning means the model id is wrong or video
+      // generation isn't enabled for this key — call that out specifically so
+      // it isn't mistaken for a transient failure.
+      const error =
+        res.status === 404
+          ? `Video model "${model}" is unavailable for this API key`
+          : "Video generation request failed";
+      return { ok: false, status: res.status, error };
     }
 
     const data = (await res.json()) as { name?: string };