diff --git a/scripts/rea.mjs b/scripts/rea.mjs
index 6d7433910..2ad29c8e0 100755
--- a/scripts/rea.mjs
+++ b/scripts/rea.mjs
@@ -8,7 +8,7 @@ const { default: packageJson } = await import("../package.json", {
 });
 process.env.REA_PACKAGE_VERSION = packageJson.version;
 const isMcpMode =
-  args[0] === "--mcp" || (args.length === 1 && args[0] === "mcp");
+  args.length === 1 && (args[0] === "--mcp" || args[0] === "mcp");
 
 if (isMcpMode) {
   const { runEntrypoint } = await import("../dist/main.js");
diff --git a/tests/dispatcher.test.ts b/tests/dispatcher.test.ts
new file mode 100644
index 000000000..2d082f989
--- /dev/null
+++ b/tests/dispatcher.test.ts
@@ -0,0 +1,64 @@
+import { execFile } from "node:child_process";
+import { copyFile, mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { promisify } from "node:util";
+
+import { afterEach, describe, expect, it } from "vitest";
+
+const execFileAsync = promisify(execFile);
+let fixtureRoot: string | undefined;
+
+afterEach(async () => {
+  if (fixtureRoot !== undefined) {
+    await rm(fixtureRoot, { recursive: true, force: true });
+    fixtureRoot = undefined;
+  }
+});
+
+describe("executable dispatcher", () => {
+  it("reserves production MCP routing for bare mode arguments", async () => {
+    fixtureRoot = await mkdtemp(join(tmpdir(), "rea-dispatcher-"));
+    const scripts = join(fixtureRoot, "scripts");
+    const dist = join(fixtureRoot, "dist");
+    await Promise.all([mkdir(scripts), mkdir(dist)]);
+    await Promise.all([
+      copyFile("scripts/rea.mjs", join(scripts, "rea.mjs")),
+      writeFile(
+        join(fixtureRoot, "package.json"),
+        JSON.stringify({ type: "module", version: "1.0.0" }),
+      ),
+      writeFile(
+        join(dist, "main.js"),
+        'export const runEntrypoint = () => process.stdout.write(JSON.stringify({ adapter: "mcp" }));\n',
+      ),
+      writeFile(
+        join(dist, "cli.js"),
+        'export const createCli = () => ({ serve: (args) => process.stdout.write(JSON.stringify({ adapter: "cli", args })) });\n',
+      ),
+      writeFile(
+        join(dist, "cliOutput.js"),
+        "export const sanitizeCliOutput = (output) => output;\n",
+      ),
+    ]);
+
+    const invoke = async (args: readonly string[]): Promise<unknown> => {
+      const { stdout } = await execFileAsync(process.execPath, [
+        join(scripts, "rea.mjs"),
+        ...args,
+      ]);
+      return JSON.parse(stdout) as unknown;
+    };
+
+    await expect(invoke(["mcp"])).resolves.toEqual({ adapter: "mcp" });
+    await expect(invoke(["--mcp"])).resolves.toEqual({ adapter: "mcp" });
+    await expect(invoke(["mcp", "add"])).resolves.toEqual({
+      adapter: "cli",
+      args: ["mcp", "add"],
+    });
+    await expect(invoke(["--mcp", "extra"])).resolves.toEqual({
+      adapter: "cli",
+      args: ["--mcp", "extra"],
+    });
+  });
+});