fix: use U2-Net as default model (fast, 2s) with BiRefNet as opt-in

BiRefNet-Lite times out on first load (~60s+ for 973MB model).
U2-Net works in 2 seconds. Users can still select BiRefNet for
higher quality when they're willing to wait. Added timing hints
in model descriptions and increased timeout for BiRefNet models.

apps/web/src/components/tools/remove-bg-settings.tsx

@@ -12,12 +12,12 @@ type BgModel =
   | "u2net";
 
 const MODELS: { value: BgModel; label: string; description: string }[] = [
-  { value: "birefnet-general", label: "BiRefNet", description: "Best quality (recommended)" },
+  { value: "u2net", label: "U2-Net", description: "Fast, good quality (recommended)" },
-  { value: "birefnet-general-lite", label: "BiRefNet Lite", description: "Faster, slightly less accurate" },
-  { value: "birefnet-portrait", label: "BiRefNet Portrait", description: "Optimized for people" },
-  { value: "bria-rmbg", label: "BRIA RMBG", description: "Great for products" },
   { value: "isnet-general-use", label: "IS-Net", description: "Good general purpose" },
-  { value: "u2net", label: "U2-Net", description: "Classic, fast" },
+  { value: "bria-rmbg", label: "BRIA RMBG", description: "Great for products" },
+  { value: "birefnet-general-lite", label: "BiRefNet Lite", description: "Higher quality, slower (~15s)" },
+  { value: "birefnet-portrait", label: "BiRefNet Portrait", description: "Best for people, slower (~15s)" },
+  { value: "birefnet-general", label: "BiRefNet Full", description: "Best quality, very slow (~60s+)" },
 ];
 
 const BG_PRESETS = [
@@ -34,7 +34,7 @@ export function RemoveBgSettings() {
   const { processFiles, processing, error, downloadUrl, originalSize, processedSize } =
     useToolProcessor("remove-background");
 
-  const [model, setModel] = useState<BgModel>("birefnet-general-lite");
+  const [model, setModel] = useState<BgModel>("u2net");
   const [bgColor, setBgColor] = useState("");
   const [elapsed, setElapsed] = useState(0);
   const timerRef = useRef<ReturnType<typeof setInterval> | null>(null);

packages/ai/python/remove_bg.py

@@ -8,7 +8,7 @@ def main():
     output_path = sys.argv[2]
     settings = json.loads(sys.argv[3]) if len(sys.argv) > 3 else {}
 
-    model = settings.get("model", "birefnet-general-lite")
+    model = settings.get("model", "u2net")
     bg_color = settings.get("backgroundColor", "")
 
     try:

packages/ai/src/background-removal.ts

@@ -3,7 +3,8 @@ import { writeFile, readFile } from "node:fs/promises";
 import { join } from "node:path";
 
 export interface RemoveBackgroundOptions {
-  model?: "u2net" | "isnet";
+  model?: string;
+  backgroundColor?: string;
 }
 
 export async function removeBackground(
@@ -15,11 +16,13 @@ export async function removeBackground(
   const outputPath = join(outputDir, "output_bg.png");
 
   await writeFile(inputPath, inputBuffer);
+  // BiRefNet models need longer timeout (up to 10 min for first load)
+  const timeout = options.model?.startsWith("birefnet") ? 600000 : 300000;
   const { stdout } = await runPythonScript("remove_bg.py", [
     inputPath,
     outputPath,
     JSON.stringify(options),
-  ]);
+  ], timeout);
 
   const result = JSON.parse(stdout);
   if (!result.success) {