diff --git a/src/agents/tools/browser-tool.test.ts b/src/agents/tools/browser-tool.test.ts
index 7248a7a2f..f6d0f8e75 100644
--- a/src/agents/tools/browser-tool.test.ts
+++ b/src/agents/tools/browser-tool.test.ts
@@ -289,3 +289,35 @@ describe("browser tool snapshot labels", () => {
     expect(result?.content?.[1]).toMatchObject({ type: "image" });
   });
 });
+
+describe("browser tool tab open and close behaviors", () => {
+  afterEach(() => {
+    vi.clearAllMocks();
+    configMocks.loadConfig.mockReturnValue({ browser: {} });
+  });
+
+  it("close a tab by targetId should be allowed in profile = 'clawd'", async () => {
+    const tool = createBrowserTool({ sandboxBridgeUrl: "http://127.0.0.1:9999" });
+    await tool.execute?.("", { action: "close", targetId: "a real target id", profile: "clawd" });
+    expect(browserClientMocks.browserCloseTab).toHaveBeenCalledWith(
+      "http://127.0.0.1:9999",
+      "a real target id",
+      { profile: "clawd" },
+    );
+  });
+
+  it("close a tab by targetId should be allowed in profile = 'chrome'", async () => {
+    const tool = createBrowserTool({ sandboxBridgeUrl: "http://127.0.0.1:9999" });
+    await tool.execute?.("", { action: "close", targetId: "a real target id", profile: "clawd" });
+    expect(browserClientMocks.browserCloseTab).toHaveBeenCalledWith(
+      "http://127.0.0.1:9999",
+      "a real target id",
+      { profile: "clawd" },
+    );
+  });
+
+  it("close a tab without targetId should throw error", async () => {
+    const tool = createBrowserTool({ sandboxBridgeUrl: "http://127.0.0.1:9999" });
+    await expect(tool.execute?.("", { action: "close" })).rejects.toThrow();
+  });
+});
diff --git a/src/agents/tools/browser-tool.ts b/src/agents/tools/browser-tool.ts
index ccdfd7c0f..8aed5d918 100644
--- a/src/agents/tools/browser-tool.ts
+++ b/src/agents/tools/browser-tool.ts
@@ -407,7 +407,13 @@ export function createBrowserTool(opts?: {
             return jsonResult(result);
           }
           if (targetId) await browserCloseTab(baseUrl, targetId, { profile });
-          else await browserAct(baseUrl, { kind: "close" }, { profile });
+          else {
+            // Known issue: The 'close' action does not verify the ownership of the current tab before atempting to close it, leading to potential action conflicts in concurrent scenarios. For now, enforce a strict close action with targetId for proxyRequest: path = "/act". The following line is commented out to prevent accidental usage. Instead, we throw an error to inform the user.
+            // await browserAct(baseUrl, { kind: "close" }, { profile });
+            throw new Error(
+              `Closing a tab without providing a targetId is not allowed. (But it was somehow allowed to do so in a previous version!). To avoid closing a tab not belonging to you, ensure you maintain a set of tabs by their targetId and provide a targetId when closing.`,
+            );
+          }
           return jsonResult({ ok: true });
         }
         case "snapshot": {