fix(engine): scope WebGPU flag to hardware mode

packages/engine/src/services/browserManager.test.ts

@@ -20,6 +20,7 @@ describe("buildChromeArgs browser GPU mode", () => {
   it("uses SwiftShader software GL by default for reproducible local renders", () => {
     const args = buildChromeArgs(base);
     expect(args).toContain("--enable-features=CanvasDrawElement");
+    expect(args).not.toContain("--enable-unsafe-webgpu");
     expect(args).toContain("--use-gl=angle");
     expect(args).toContain("--use-angle=swiftshader");
     expect(args).toContain("--enable-unsafe-swiftshader");
@@ -28,6 +29,7 @@ describe("buildChromeArgs browser GPU mode", () => {
 
   it("uses Metal-backed ANGLE for hardware browser GPU mode on macOS", () => {
     const args = buildChromeArgs({ ...base, platform: "darwin" }, { browserGpuMode: "hardware" });
+    expect(args).toContain("--enable-unsafe-webgpu");
     expect(args).toContain("--use-gl=angle");
     expect(args).toContain("--use-angle=metal");
     expect(args).toContain("--enable-gpu-rasterization");

packages/engine/src/services/browserManager.ts

@@ -504,7 +504,6 @@ export function buildChromeArgs(
     "--disable-setuid-sandbox",
     "--disable-dev-shm-usage",
     CANVAS_DRAW_ELEMENT_FEATURE_FLAG,
-    WEBGPU_FLAG,
     "--enable-webgl",
     "--ignore-gpu-blocklist",
     ...getBrowserGpuArgs(browserGpuMode, platform),
@@ -538,6 +537,10 @@ export function buildChromeArgs(
     "--disable-features=AudioServiceOutOfProcess,IsolateOrigins,site-per-process,Translate,BackForwardCache,IntensiveWakeUpThrottling",
   ];
 
+  if (browserGpuMode !== "software") {
+    chromeArgs.push(WEBGPU_FLAG);
+  }
+
   // BeginFrame flags — only when using chrome-headless-shell on Linux
   if (options.captureMode !== "screenshot") {
     chromeArgs.push(