Improve WebGPU model load fallback

app.py

@@ -67,6 +67,17 @@ custom_html = f"""
 const warning = document.getElementById("webgpu-warning");
 const loadButton = document.getElementById("load-btn");
 
+function formatBrowserError(error) {{
+    if (!error) return "unknown error";
+    if (error.message) return error.message;
+    if (typeof error === "string") return error;
+    try {{
+        return JSON.stringify(error);
+    }} catch (_err) {{
+        return String(error);
+    }}
+}}
+
 function findGradioInput(id) {{
     const root = document.getElementById(id);
     if (!root) return null;
@@ -92,19 +103,24 @@ window.initEngine = async function() {{
     document.getElementById("load-status").textContent = "Loading model weights...";
     try {{
         await loadModel((progress) => {{
+            if (progress.status === "attempt") {{
+                document.getElementById("load-status").textContent = `Trying ${{progress.dtype}} WebGPU weights...`;
+                return;
+            }}
             const value = progress.progress ? Math.round(progress.progress) : 0;
             document.getElementById("load-progress").style.width = `${{value}}%`;
             if (progress.file) {{
-                document.getElementById("load-status").textContent = `${{progress.file}} - ${{value}}%`;
+                document.getElementById("load-status").textContent = `${{progress.file}} (${{progress.dtype || "auto"}}) - ${{value}}%`;
             }}
         }});
         document.getElementById("load-progress").style.width = "100%";
-        document.getElementById("load-status").textContent = "Model ready - WebGPU active";
+        document.getElementById("load-status").textContent = `Model ready - WebGPU active (${{getActiveDtype() || "auto"}})`;
         document.getElementById("load-section").classList.add("loaded");
         setStatus("Ready", "success");
     }} catch (error) {{
+        console.error("Model load failed", error);
         loadButton.disabled = false;
-        setStatus(`Model load failed: ${{error.message}}`, "warning");
+        setStatus(`Model load failed: ${{formatBrowserError(error)}}`, "warning");
         document.getElementById("load-status").textContent = "Load failed";
     }}
 }};

static/engine.js

@@ -1,19 +1,34 @@
 import { pipeline, TextStreamer } from "https://cdn.jsdelivr.net/npm/@huggingface/transformers@3.5.0/dist/transformers.min.js";
 
 const MODEL_ID = "onnx-community/Qwen2.5-Coder-1.5B-Instruct";
+const DTYPE_CANDIDATES = ["q4f16", "q4", "fp16"];
 
 let generator = null;
 let isLoaded = false;
+let activeDtype = null;
 
 export async function loadModel(onProgress) {
     if (isLoaded) return;
 
-    generator = await pipeline("text-generation", MODEL_ID, {
-        dtype: "q4",
-        device: "webgpu",
-        progress_callback: onProgress,
-    });
-    isLoaded = true;
+    const errors = [];
+    for (const dtype of DTYPE_CANDIDATES) {
+        try {
+            onProgress?.({ status: "attempt", dtype });
+            generator = await pipeline("text-generation", MODEL_ID, {
+                dtype,
+                device: "webgpu",
+                progress_callback: (progress) => onProgress?.({ ...progress, dtype }),
+            });
+            activeDtype = dtype;
+            isLoaded = true;
+            return;
+        } catch (error) {
+            console.error(`Model load failed for dtype=${dtype}`, error);
+            errors.push(`${dtype}: ${formatError(error)}`);
+        }
+    }
+
+    throw new Error(`All WebGPU dtype attempts failed. ${errors.join(" | ")}`);
 }
 
 export async function generateCode(prompt, language, onToken, onComplete) {
@@ -51,8 +66,24 @@ export function isWebGPUSupported() {
     return Boolean(navigator.gpu);
 }
 
+export function getActiveDtype() {
+    return activeDtype;
+}
+
+function formatError(error) {
+    if (!error) return "unknown error";
+    if (error.message) return error.message;
+    if (typeof error === "string") return error;
+    try {
+        return JSON.stringify(error);
+    } catch {
+        return String(error);
+    }
+}
+
 Object.assign(window, {
     loadModel,
     generateCode,
     isWebGPUSupported,
+    getActiveDtype,
 });