1 files changed, 40 insertions, 0 deletions
diff --git a/src/domains/viewport.ts b/src/domains/viewport.ts
new file mode 100644
index 0000000..015ac68
--- /dev/null
+++ b/src/domains/viewport.ts
@@ -0,0 +1,40 @@
+import { Type } from "typebox";
+import { type Result, err, ok } from "../util/result";
+import { defineBrowserTool, type ToolErr, type ToolOk } from "../util/tool";
+
+const ViewportArgs = Type.Object({
+  width: Type.Integer({ minimum: 100, maximum: 8000, description: "Viewport CSS pixel width" }),
+  height: Type.Integer({ minimum: 100, maximum: 8000, description: "Viewport CSS pixel height" }),
+  deviceScaleFactor: Type.Optional(
+    Type.Number({ minimum: 0.5, maximum: 4, default: 1, description: "Device pixel ratio" }),
+  ),
+});
+
+export const viewportResizeTool = defineBrowserTool({
+  name: "browser_viewport_resize",
+  label: "Browser Viewport Resize",
+  description: "Override the viewport size and device pixel ratio for responsive testing.",
+  promptSnippet: "Resize the viewport (responsive testing)",
+  promptGuidelines: [
+    "Width/height in CSS pixels (e.g., 375x667 for iPhone SE).",
+    "Pass deviceScaleFactor=2 to simulate retina displays.",
+  ],
+  parameters: ViewportArgs,
+  async handler(args, { client }): Promise<Result<ToolOk, ToolErr>> {
+    const r = await client.session().call("Emulation.setDeviceMetricsOverride", {
+      width: args.width,
+      height: args.height,
+      deviceScaleFactor: args.deviceScaleFactor ?? 1,
+      mobile: false,
+    });
+    if (!r.success) return err({ kind: "cdp_error", message: r.error.message });
+    return ok({
+      text: `Viewport set to ${args.width}x${args.height} @${args.deviceScaleFactor ?? 1}x`,
+      details: {
+        width: args.width,
+        height: args.height,
+        deviceScaleFactor: args.deviceScaleFactor ?? 1,
+      },
+    });
+  },
+});