diff --git a/agentchatbus-ts/scripts/build-bundle.mjs b/agentchatbus-ts/scripts/build-bundle.mjs
index 0198f23e..341cade1 100644
--- a/agentchatbus-ts/scripts/build-bundle.mjs
+++ b/agentchatbus-ts/scripts/build-bundle.mjs
@@ -22,6 +22,7 @@ async function prepareDistDir() {
 async function copyWorkerAssets() {
   const workers = [
     ['src/core/services/adapters/workers/interactivePtyWorker.mjs', 'dist/workers/interactivePtyWorker.mjs'],
+    ['src/transports/stdio/mcpProxy.mjs', 'dist/workers/mcpProxy.mjs'],
   ];
   for (const [source, target] of workers) {
     await copyFile(path.join(projectRoot, source), path.join(projectRoot, target));
diff --git a/agentchatbus-ts/src/core/services/acpAdapter.ts b/agentchatbus-ts/src/core/services/acpAdapter.ts
index 0da77c24..05ee949f 100644
--- a/agentchatbus-ts/src/core/services/acpAdapter.ts
+++ b/agentchatbus-ts/src/core/services/acpAdapter.ts
@@ -26,6 +26,7 @@ import {
   getAcpAgent,
   type AcpAgentConfig,
 } from "./acpRegistry.js";
+import { resolveAcpMcpProxyScript } from "./acpMcpProxyPath.js";
 import type {
   CliAdapterActivityEvent,
   CliAdapterNativeRuntimeEvent,
@@ -406,7 +407,7 @@ export class AcpAdapter implements CliSessionAdapter {
             // Try stdio MCP proxy as a fallback for agents that don't have
             // pre-configured MCP servers. Agents with pre-configured MCP will
             // use their own config.
-            const proxyScript = new URL("../../transports/stdio/mcpProxy.mjs", import.meta.url).pathname;
+            const proxyScript = resolveAcpMcpProxyScript();
             const envVars: acp.EnvVariable[] = [
               { name: "AGENTCHATBUS_BASE_URL", value: baseUrl },
             ];
diff --git a/agentchatbus-ts/src/core/services/acpMcpProxyPath.ts b/agentchatbus-ts/src/core/services/acpMcpProxyPath.ts
new file mode 100644
index 00000000..0277beaf
--- /dev/null
+++ b/agentchatbus-ts/src/core/services/acpMcpProxyPath.ts
@@ -0,0 +1,35 @@
+import { existsSync } from "node:fs";
+import path from "node:path";
+
+const PROXY_FILE_NAME = "mcpProxy.mjs";
+
+/**
+ * Resolve the standalone ACP stdio MCP proxy script.
+ *
+ * The CLI is bundled as CJS (`dist/cli/index.js`), where `import.meta.url` is
+ * empty. The proxy stays an ESM `.mjs` asset spawned as a child process, copied
+ * next to the bundle as `dist/workers/mcpProxy.mjs` (same pattern as
+ * `resolveWorkerPath` in interactivePtyChildBridge).
+ */
+export function resolveAcpMcpProxyScript(): string {
+  const entryFile = path.resolve(process.argv[1] || process.cwd());
+  const entryDir = path.dirname(entryFile);
+  const candidates = [
+    path.resolve(entryDir, "../workers", PROXY_FILE_NAME),
+    path.resolve(entryDir, "../../transports/stdio", PROXY_FILE_NAME),
+    path.resolve(entryDir, "../../src/transports/stdio", PROXY_FILE_NAME),
+    path.resolve(process.cwd(), "dist/workers", PROXY_FILE_NAME),
+    path.resolve(process.cwd(), "src/transports/stdio", PROXY_FILE_NAME),
+  ];
+
+  for (const candidate of candidates) {
+    if (existsSync(candidate)) {
+      return candidate;
+    }
+  }
+
+  throw new Error(
+    `Unable to locate ACP stdio MCP proxy '${PROXY_FILE_NAME}'. ` +
+      `Checked: ${candidates.join(", ")}`,
+  );
+}
diff --git a/agentchatbus-ts/tests/unit/test_acp_mcp_proxy_path.test.ts b/agentchatbus-ts/tests/unit/test_acp_mcp_proxy_path.test.ts
new file mode 100644
index 00000000..6c366191
--- /dev/null
+++ b/agentchatbus-ts/tests/unit/test_acp_mcp_proxy_path.test.ts
@@ -0,0 +1,30 @@
+import { existsSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { describe, expect, it } from "vitest";
+import { resolveAcpMcpProxyScript } from "../../src/core/services/acpMcpProxyPath.js";
+
+const SOURCE_PROXY = path.resolve(
+  path.dirname(fileURLToPath(import.meta.url)),
+  "../../src/transports/stdio/mcpProxy.mjs",
+);
+
+describe("ACP stdio MCP proxy path", () => {
+  it("resolves an existing mcpProxy.mjs", () => {
+    const resolved = resolveAcpMcpProxyScript();
+    expect(existsSync(resolved)).toBe(true);
+    expect(path.basename(resolved)).toBe("mcpProxy.mjs");
+    expect(resolved).not.toMatch(/^\/[A-Za-z]:/);
+  });
+
+  it("finds the source script when the bundled worker copy is absent", () => {
+    const originalArgv1 = process.argv[1];
+    process.argv[1] = path.join(path.dirname(SOURCE_PROXY), "not-the-cli.js");
+    try {
+      const resolved = resolveAcpMcpProxyScript();
+      expect(path.normalize(resolved)).toBe(path.normalize(SOURCE_PROXY));
+    } finally {
+      process.argv[1] = originalArgv1;
+    }
+  });
+});