diff --git a/src/agents/tools/browser-tool.test.ts b/src/agents/tools/browser-tool.test.ts
index 97bb3b026..eaac9561a 100644
--- a/src/agents/tools/browser-tool.test.ts
+++ b/src/agents/tools/browser-tool.test.ts
@@ -134,6 +134,18 @@ describe("browser tool snapshot maxChars", () => {
       }),
     );
   });
+
+  it("defaults to host when using profile=chrome (even in sandboxed sessions)", async () => {
+    const tool = createBrowserTool({ defaultControlUrl: "http://127.0.0.1:9999" });
+    await tool.execute?.(null, { action: "snapshot", profile: "chrome", format: "ai" });
+
+    expect(browserClientMocks.browserSnapshot).toHaveBeenCalledWith(
+      "http://127.0.0.1:18791",
+      expect.objectContaining({
+        profile: "chrome",
+      }),
+    );
+  });
 });
 
 describe("browser tool snapshot labels", () => {
diff --git a/src/agents/tools/browser-tool.ts b/src/agents/tools/browser-tool.ts
index 782201693..5e6669dc6 100644
--- a/src/agents/tools/browser-tool.ts
+++ b/src/agents/tools/browser-tool.ts
@@ -141,8 +141,12 @@ export function createBrowserTool(opts?: {
       const params = args as Record<string, unknown>;
       const action = readStringParam(params, "action", { required: true });
       const controlUrl = readStringParam(params, "controlUrl");
-      const target = readStringParam(params, "target") as "sandbox" | "host" | "custom" | undefined;
       const profile = readStringParam(params, "profile");
+      let target = readStringParam(params, "target") as "sandbox" | "host" | "custom" | undefined;
+      if (profile === "chrome" && !target && !controlUrl?.trim()) {
+        // Chrome extension relay takeover is a host Chrome feature; default to host even in sandboxed sessions.
+        target = "host";
+      }
       const baseUrl = resolveBrowserBaseUrl({
         target,
         controlUrl,
@@ -345,10 +349,30 @@ export function createBrowserTool(opts?: {
           if (!request || typeof request !== "object") {
             throw new Error("request required");
           }
-          const result = await browserAct(baseUrl, request as Parameters<typeof browserAct>[1], {
-            profile,
-          });
-          return jsonResult(result);
+          try {
+            const result = await browserAct(
+              baseUrl,
+              request as Parameters<typeof browserAct>[1],
+              {
+                profile,
+              },
+            );
+            return jsonResult(result);
+          } catch (err) {
+            const msg = String(err);
+            if (msg.includes("404:") && msg.includes("tab not found") && profile === "chrome") {
+              const tabs = await browserTabs(baseUrl, { profile }).catch(() => []);
+              if (!tabs.length) {
+                throw new Error(
+                  'No Chrome tabs are attached via the Clawdbot Browser Relay extension. Click the toolbar icon on the tab you want to control (badge ON), then retry.',
+                );
+              }
+              throw new Error(
+                `Chrome tab not found (stale targetId?). Run action=tabs profile="chrome" and use one of the returned targetIds.`,
+              );
+            }
+            throw err;
+          }
         }
         default:
           throw new Error(`Unknown action: ${action}`);