diff --git a/extensions/qa-lab/src/suite-runtime-agent-tools.test.ts b/extensions/qa-lab/src/suite-runtime-agent-tools.test.ts
index beefb15ba5ee..b8d43f90a6aa 100644
--- a/extensions/qa-lab/src/suite-runtime-agent-tools.test.ts
+++ b/extensions/qa-lab/src/suite-runtime-agent-tools.test.ts
@@ -124,7 +124,7 @@ describe("qa suite runtime agent tools helpers", () => {
     ).resolves.toEqual("done");
   });
 
-  it("calls plugin-tools MCP through the resolved node executable", async () => {
+  it("falls back to the source plugin-tools MCP entry", async () => {
     listToolsMock.mockResolvedValueOnce({
       tools: [{ name: "plugin.echo" }] as never[],
     });
@@ -180,6 +180,35 @@ describe("qa suite runtime agent tools helpers", () => {
     expect(closeMock).toHaveBeenCalled();
   });
 
+  it("prefers the built plugin-tools MCP entry", async () => {
+    const builtRepoRoot = await makeTempDir("qa-built-repo-");
+    const distEntry = path.join(builtRepoRoot, "dist", "mcp", "plugin-tools-serve.js");
+    await fs.mkdir(path.dirname(distEntry), { recursive: true });
+    await fs.writeFile(distEntry, "// built MCP entry\n", "utf8");
+    listToolsMock.mockResolvedValueOnce({
+      tools: [{ name: "plugin.echo" }] as never[],
+    });
+
+    await callPluginToolsMcp({
+      env: {
+        gateway: {
+          tempRoot: gatewayTempRoot,
+          runtimeEnv: { PATH: "/usr/bin" },
+        },
+        repoRoot: builtRepoRoot,
+      } as never,
+      toolName: "plugin.echo",
+      args: {},
+    });
+
+    expect(stdioTransportMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        command: "/usr/bin/node",
+        args: [distEntry],
+      }),
+    );
+  });
+
   it("reports available plugin-tools MCP names when the requested tool is missing", async () => {
     listToolsMock.mockResolvedValueOnce({
       tools: [{ name: "plugin.beta" }, { name: "plugin.alpha" }] as never[],
diff --git a/extensions/qa-lab/src/suite-runtime-agent-tools.ts b/extensions/qa-lab/src/suite-runtime-agent-tools.ts
index 91b9b0a2b0c6..5a38d89dd9f3 100644
--- a/extensions/qa-lab/src/suite-runtime-agent-tools.ts
+++ b/extensions/qa-lab/src/suite-runtime-agent-tools.ts
@@ -22,6 +22,20 @@ const requireFromHere = createRequire(import.meta.url);
 const MCP_STDERR_TAIL_LIMIT = 8_192;
 const MCP_REQUEST_TIMEOUT_MS = 180_000;
 
+async function resolvePluginToolsMcpArgs(repoRoot: string) {
+  const distEntry = path.join(repoRoot, "dist", "mcp", "plugin-tools-serve.js");
+  try {
+    await fs.access(distEntry);
+    return [distEntry];
+  } catch {
+    return [
+      "--import",
+      requireFromHere.resolve("tsx"),
+      path.join(repoRoot, "src", "mcp", "plugin-tools-serve.ts"),
+    ];
+  }
+}
+
 function findSkill(skills: QaSkillStatusEntry[], name: string) {
   return skills.find((skill) => skill.name === name);
 }
@@ -73,11 +87,7 @@ async function callPluginToolsMcp(params: {
   const nodeExecPath = await resolveQaNodeExecPath();
   const transport = new StdioClientTransport({
     command: nodeExecPath,
-    args: [
-      "--import",
-      requireFromHere.resolve("tsx"),
-      path.join(params.env.repoRoot, "src/mcp/plugin-tools-serve.ts"),
-    ],
+    args: await resolvePluginToolsMcpArgs(params.env.repoRoot),
     stderr: "pipe",
     cwd: params.env.repoRoot,
     env: transportEnv,