diff --git a/test/extract-mcp-json.test.ts b/test/extract-mcp-json.test.ts
new file mode 100644
index 00000000000..d0aca7df2fc
--- /dev/null
+++ b/test/extract-mcp-json.test.ts
@@ -0,0 +1,15 @@
+import { extractMcpJson } from "../app/mcp/utils";
+
+describe("extractMcpJson", () => {
+  test("extracts the client id and parsed mcp payload", () => {
+    const content = '```json:mcp:client-1\n{"tool":"x"}\n```';
+    expect(extractMcpJson(content)).toEqual({
+      clientId: "client-1",
+      mcp: { tool: "x" },
+    });
+  });
+
+  test("returns null when there is no mcp block", () => {
+    expect(extractMcpJson("no mcp here")).toBeNull();
+  });
+});