fix(cli): exit the server when the MCP client closes stdin (#68)

* fix(cli): exit the server when the MCP client closes stdin

* fix(security): refresh fast-uri lockfile entry to 3.1.5

* fix(cli): route stdio entrypoints through lifecycle wrapper

---------

Co-authored-by: George Tsiolis <tsiolis.g@gmail.com>

Author: HarshCasper

Dockerfile

@@ -77,11 +77,12 @@ RUN set -eux; \
     command -v samlocal; \
     cdklocal --version; \
     snow --version; \
+    node dist/cli.js version; \
     node -e "require('dockerode'); console.log('dockerode ok')"
 
 LABEL org.opencontainers.image.title="LocalStack MCP Server" \
       org.opencontainers.image.description="Self-contained MCP server for managing LocalStack" \
       org.opencontainers.image.source="https://github.com/localstack/localstack-mcp-server" \
       org.opencontainers.image.licenses="Apache-2.0"
 
-ENTRYPOINT ["node", "dist/stdio.js"]
+ENTRYPOINT ["node", "dist/cli.js"]

README.md

@@ -156,7 +156,7 @@ If you installed from source, change `command` and `args` to point to your local
   "mcpServers": {
     "localstack": {
       "command": "node",
-      "args": ["/path/to/your/localstack-mcp-server/dist/stdio.js"],
+      "args": ["/path/to/your/localstack-mcp-server/dist/cli.js"],
       "env": {
         "LOCALSTACK_AUTH_TOKEN": "<YOUR_TOKEN>"
       }
@@ -269,7 +269,7 @@ This repository includes [MCP Server Tester](https://github.com/gleanwork/mcp-se
 
 Notes:
 
-- MCP tests target the local STDIO server command `node dist/stdio.js` by default.
+- MCP tests target the lifecycle-aware local server command `node dist/cli.js` by default.
 - `LOCALSTACK_AUTH_TOKEN` is required for all MCP tool usage and test suites.
 - You can override the target command with:
   - `MCP_TEST_COMMAND`

docs/DOCKER.md

@@ -128,13 +128,14 @@ alias covers bootstrap asset uploads.
 
 ## Troubleshooting
 
-| Symptom                                                                                                     | Cause / fix                                                                                                                                    |
-| ----------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
-| Tools report `LocalStack Not Running` after `start`                                                         | Check `LOCALSTACK_HOSTNAME=host.docker.internal` is set and `--add-host` is present (Linux).                                                   |
-| `Auth Token Required`                                                                                       | `LOCALSTACK_AUTH_TOKEN` must be passed through (every tool requires it).                                                                       |
-| `Docker Not Available` / daemon unreachable                                                                 | Ensure `/var/run/docker.sock` is mounted (or pass `DOCKER_HOST` for a non-default daemon).                                                     |
-| `LocalStack container not found` or `Could not find a running LocalStack container named "localstack-main"` | Set `MAIN_CONTAINER_NAME` if you use a custom LocalStack container name.                                                                       |
-| State disappeared after upgrading the image                                                                 | Old configs stored state under `$XDG_CACHE_HOME/localstack/volume` — keep that env var, or point `LOCALSTACK_VOLUME_DIR` at the old directory. |
+| Symptom                                                                                                     | Cause / fix                                                                                                                                                                                      |
+| ----------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
+| Tools report `LocalStack Not Running` after `start`                                                         | Check `LOCALSTACK_HOSTNAME=host.docker.internal` is set and `--add-host` is present (Linux).                                                                                                     |
+| `Auth Token Required`                                                                                       | `LOCALSTACK_AUTH_TOKEN` must be passed through (every tool requires it).                                                                                                                         |
+| `Docker Not Available` / daemon unreachable                                                                 | Ensure `/var/run/docker.sock` is mounted (or pass `DOCKER_HOST` for a non-default daemon).                                                                                                       |
+| `LocalStack container not found` or `Could not find a running LocalStack container named "localstack-main"` | Set `MAIN_CONTAINER_NAME` if you use a custom LocalStack container name.                                                                                                                         |
+| State disappeared after upgrading the image                                                                 | Old configs stored state under `$XDG_CACHE_HOME/localstack/volume` — keep that env var, or point `LOCALSTACK_VOLUME_DIR` at the old directory.                                                   |
+| MCP server containers pile up over time                                                                     | Older images did not exit when the client disconnected. Pull the latest image, then remove strays with `docker ps -aq --filter ancestor=localstack/localstack-mcp-server \| xargs docker rm -f`. |
 
 ## Validating an image yourself
 

manifest.json

@@ -15,10 +15,10 @@
   "icon": "icon.png",
   "server": {
     "type": "node",
-    "entry_point": "./dist/stdio.js",
+    "entry_point": "./dist/cli.js",
     "mcp_config": {
       "command": "node",
-      "args": ["${__dirname}/./dist/stdio.js"],
+      "args": ["${__dirname}/./dist/cli.js"],
       "env": {}
     }
   },

package.json

@@ -10,7 +10,7 @@
     "build": "xmcp build && yarn build:cli",
     "build:cli": "esbuild src/cli/index.ts --bundle --platform=node --format=cjs --target=node22 --tsconfig=tsconfig.cli.json --alias:jsonc-parser=jsonc-parser/lib/esm/main.js --outfile=dist/cli.js --external:./stdio.js \"--banner:js=#!/usr/bin/env node\" --log-level=warning",
     "dev": "xmcp dev",
-    "start": "node dist/stdio.js",
+    "start": "node dist/cli.js",
     "prepack": "yarn build",
     "format": "prettier --write .",
     "test": "jest",
@@ -46,7 +46,7 @@
     "@hono/node-server": "^2.0.5",
     "ip-address": "^10.1.1"
   },
-  "main": "./dist/stdio.js",
+  "main": "./dist/cli.js",
   "files": [
     "dist"
   ],

playwright.config.mjs

@@ -3,7 +3,7 @@ import { defineConfig } from "@playwright/test";
 const mcpCommand = process.env.MCP_TEST_COMMAND || "node";
 const mcpArgs = process.env.MCP_TEST_ARGS
   ? process.env.MCP_TEST_ARGS.split(" ").filter(Boolean)
-  : ["dist/stdio.js"];
+  : ["dist/cli.js"];
 
 export default defineConfig({
   testDir: "./tests/mcp",

src/cli/index.ts

@@ -6,6 +6,8 @@
 import * as fs from "fs";
 import * as path from "path";
 
+import { exitWhenClientDisconnects } from "./lifecycle";
+
 function getVersion(): string {
   try {
     const packageJson = JSON.parse(
@@ -55,6 +57,7 @@ async function main(): Promise<void> {
           `Unknown command "${command}" — starting the MCP server. Did you mean "init"? See --help for setup commands.`
         );
       }
+      exitWhenClientDisconnects();
       require("./stdio.js");
   }
 }

src/cli/lifecycle.test.ts

@@ -0,0 +1,48 @@
+import { EventEmitter } from "events";
+
+import { exitWhenClientDisconnects } from "./lifecycle";
+
+describe("exitWhenClientDisconnects", () => {
+  let exitSpy: jest.SpyInstance;
+
+  beforeEach(() => {
+    jest.useFakeTimers();
+    exitSpy = jest.spyOn(process, "exit").mockImplementation((() => undefined) as never);
+  });
+
+  afterEach(() => {
+    exitSpy.mockRestore();
+    jest.useRealTimers();
+  });
+
+  it("exits with code 0 after stdin ends", () => {
+    const stdin = new EventEmitter();
+    exitWhenClientDisconnects(stdin);
+
+    stdin.emit("end");
+
+    expect(exitSpy).not.toHaveBeenCalled();
+    jest.runAllTimers();
+    expect(exitSpy).toHaveBeenCalledWith(0);
+  });
+
+  it("exits once when both end and close fire", () => {
+    const stdin = new EventEmitter();
+    exitWhenClientDisconnects(stdin);
+
+    stdin.emit("end");
+    stdin.emit("close");
+    jest.runAllTimers();
+
+    expect(exitSpy).toHaveBeenCalledTimes(1);
+  });
+
+  it("stays alive while the client is connected", () => {
+    const stdin = new EventEmitter();
+    exitWhenClientDisconnects(stdin);
+
+    jest.runAllTimers();
+
+    expect(exitSpy).not.toHaveBeenCalled();
+  });
+});

src/cli/lifecycle.ts

@@ -0,0 +1,23 @@
+/**
+ * MCP clients signal shutdown over stdio by closing the server's stdin.
+ * The bundled transport only listens for "data", so without this watcher
+ * the process outlives its client: `docker run --rm` never removes the
+ * container and npx-launched processes linger on the host.
+ */
+
+// Must exceed the PostHog flushInterval in core/analytics.ts (1000 ms) so
+// telemetry from the final tool call is sent before the process exits.
+const TELEMETRY_FLUSH_GRACE_MS = 1250;
+
+export function exitWhenClientDisconnects(stdin: NodeJS.EventEmitter = process.stdin): void {
+  let exitScheduled = false;
+
+  const scheduleExit = () => {
+    if (exitScheduled) return;
+    exitScheduled = true;
+    setTimeout(() => process.exit(0), TELEMETRY_FLUSH_GRACE_MS);
+  };
+
+  stdin.once("end", scheduleExit);
+  stdin.once("close", scheduleExit);
+}

tests/mcp/direct.spec.mjs

@@ -1,5 +1,6 @@
 import { expect, test } from "@gleanwork/mcp-server-tester/fixtures/mcp";
 import { execFileSync, spawn } from "node:child_process";
+import { once } from "node:events";
 import { mkdirSync, mkdtempSync, readFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
@@ -141,3 +142,28 @@ test("wizard: no-arg dist/cli.js still serves MCP over stdio", async () => {
     child.kill();
   }
 });
+
+test("dist/cli.js exits when the client closes stdin", async () => {
+  const child = spawn("node", ["-e", 'setInterval(() => {}, 1000); require("./dist/cli.js")'], {
+    stdio: ["pipe", "pipe", "pipe"],
+  });
+
+  try {
+    const exited = once(child, "exit");
+    child.stdin.end();
+
+    const [code, signal] = await Promise.race([
+      exited,
+      new Promise((_, reject) =>
+        setTimeout(() => reject(new Error("server did not exit after stdin closed")), 5000)
+      ),
+    ]);
+
+    expect(code).toBe(0);
+    expect(signal).toBeNull();
+  } finally {
+    if (child.exitCode === null && child.signalCode === null) {
+      child.kill("SIGKILL");
+    }
+  }
+});