fix: WaveSpeed video generation saves as .mp4 instead of .bin

Derive provider capabilities from mediaType instead of hardcoding
text-to-image, so isVideoModel is correct for video generations.
Treat application/octet-stream as unhelpful content-type and fall back
to video/mp4 or image/png based on model type. Add safety net in
save-generation to override .bin extension when media type is known.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/api/generate/route.ts

@@ -2199,9 +2199,11 @@ async function generateWithWaveSpeed(
   const outputArrayBuffer = await outputResponse.arrayBuffer();
   const outputSizeMB = outputArrayBuffer.byteLength / (1024 * 1024);
 
+  const rawContentType = outputResponse.headers.get("content-type");
   const contentType =
-    outputResponse.headers.get("content-type") ||
+    (rawContentType && rawContentType !== "application/octet-stream")
-    (isVideoModel ? "video/mp4" : "image/png");
+      ? rawContentType
+      : (isVideoModel ? "video/mp4" : "image/png");
 
   console.log(`[API:${requestId}] Output: ${contentType}, ${outputSizeMB.toFixed(2)}MB`);
 
@@ -2323,7 +2325,7 @@ export async function POST(request: NextRequest) {
           id: selectedModel!.modelId,
           name: selectedModel!.displayName,
           provider: "replicate",
-          capabilities: ["text-to-image"],
+          capabilities: mediaType === "video" ? ["text-to-video"] : ["text-to-image"],
           description: null,
         },
         prompt: prompt || "",
@@ -2411,7 +2413,7 @@ export async function POST(request: NextRequest) {
           id: selectedModel!.modelId,
           name: selectedModel!.displayName,
           provider: "fal",
-          capabilities: ["text-to-image"],
+          capabilities: mediaType === "video" ? ["text-to-video"] : ["text-to-image"],
           description: null,
         },
         prompt: prompt || "",
@@ -2502,7 +2504,7 @@ export async function POST(request: NextRequest) {
           id: selectedModel!.modelId,
           name: selectedModel!.displayName,
           provider: "kie",
-          capabilities: ["text-to-image"],
+          capabilities: mediaType === "video" ? ["text-to-video"] : ["text-to-image"],
           description: null,
         },
         prompt: prompt || "",
@@ -2593,7 +2595,7 @@ export async function POST(request: NextRequest) {
           id: selectedModel!.modelId,
           name: selectedModel!.displayName,
           provider: "wavespeed",
-          capabilities: ["text-to-image"],
+          capabilities: mediaType === "video" ? ["text-to-video"] : ["text-to-image"],
           description: null,
         },
         prompt: prompt || "",

src/app/api/save-generation/route.ts

@@ -165,7 +165,10 @@ export async function POST(request: NextRequest) {
           }
         }
 
-        const contentType = response.headers.get("content-type") || (isVideo ? "video/mp4" : "image/png");
+        const rawSaveContentType = response.headers.get("content-type");
+        const contentType = (rawSaveContentType && rawSaveContentType !== "application/octet-stream")
+          ? rawSaveContentType
+          : (isVideo ? "video/mp4" : "image/png");
         extension = getExtensionFromMime(contentType);
 
         const arrayBuffer = await response.arrayBuffer();
@@ -198,6 +201,11 @@ export async function POST(request: NextRequest) {
       }
     }
 
+    // Safety net: if extension resolved to "bin" but we know the media type, use correct extension
+    if (extension === "bin") {
+      extension = isVideo ? "mp4" : "png";
+    }
+
     // Compute content hash for deduplication
     const contentHash = computeContentHash(buffer);