diff --git a/src/cli/commands/server.ts b/src/cli/commands/server.ts
index aaec43d..345f480 100644
--- a/src/cli/commands/server.ts
+++ b/src/cli/commands/server.ts
@@ -1,6 +1,23 @@
 import type { Command } from "commander";
 import { ensureHome, getConfig } from "../../core/config.ts";
 
+// Test-only watchdog: when KNOTES_E2E_WATCH_STDIN=1 is set, exit as soon
+// as stdin closes. The e2e harness wires its own pipe to our stdin and
+// keeps the write end open for the server's lifetime; the kernel closes
+// it the moment the harness process dies (including SIGKILL/OOM), so
+// reading EOF here is a parent-death signal that can't be missed.
+function installStdinWatchdog(): void {
+  if (process.env["KNOTES_E2E_WATCH_STDIN"] !== "1") return;
+  const exitOnParentGone = () => {
+    console.error("E2E watchdog: stdin closed, parent gone, exiting");
+    process.exit(0);
+  };
+  process.stdin.on("data", () => {});
+  process.stdin.on("end", exitOnParentGone);
+  process.stdin.on("close", exitOnParentGone);
+  process.stdin.resume();
+}
+
 export function registerServerCommand(program: Command): void {
   program
     .command("server")
@@ -11,6 +28,8 @@ export function registerServerCommand(program: Command): void {
       const config = getConfig();
       const port = opts.port ? parseInt(opts.port, 10) : config.webPort;
 
+      installStdinWatchdog();
+
       const { createWebServer } = await import("../../web/server.ts");
       const server = createWebServer(port);
       console.log(`Knotes server running at http://localhost:${port}`);
diff --git a/test/e2e/globalSetup.ts b/test/e2e/globalSetup.ts
index 8234685..f72aada 100644
--- a/test/e2e/globalSetup.ts
+++ b/test/e2e/globalSetup.ts
@@ -54,10 +54,22 @@ export async function setup() {
   await prepareHome(serverHome, false);
 
   const port = await getFreePort();
-  const serverProcess = spawn("npx", ["tsx", "src/main.ts", "server", "--port", String(port)], {
-    env: { ...process.env, KNOTES_HOME: serverHome },
+  const tsxBin = join(PROJECT_ROOT, "node_modules/.bin/tsx");
+  // stdio[0] is a real pipe (not "ignore") so the server can detect our death
+  // via EOF on stdin — see installStdinWatchdog in src/cli/commands/server.ts.
+  // The kernel closes the write end the moment this process exits for any
+  // reason (clean teardown, SIGKILL, OOM), so the server can never miss it.
+  // detached:true puts the server in its own process group so we can tear
+  // the whole subtree (tsx wrapper + server) down in one signal on teardown.
+  const serverProcess = spawn(tsxBin, ["src/main.ts", "server", "--port", String(port)], {
+    env: {
+      ...process.env,
+      KNOTES_HOME: serverHome,
+      KNOTES_E2E_WATCH_STDIN: "1",
+    },
     cwd: PROJECT_ROOT,
-    stdio: ["ignore", "pipe", "pipe"],
+    stdio: ["pipe", "pipe", "pipe"],
+    detached: true,
   });
   serverProcess.stdout?.on("data", () => {});
   serverProcess.stderr?.on("data", () => {});
@@ -81,12 +93,20 @@ export async function setup() {
   process.env["E2E_SERVER_PORT"] = String(port);
 
   return async () => {
-    if (!serverProcess.killed) serverProcess.kill("SIGTERM");
+    const pgid = serverProcess.pid;
+    const killGroup = (sig: NodeJS.Signals) => {
+      if (pgid == null) return;
+      try { process.kill(-pgid, sig); } catch {}
+    };
+    // Closing stdin triggers the server's EOF watchdog (clean exit path).
+    // The SIGTERM/SIGKILL fallbacks below cover anything that wasn't
+    // listening on stdin (e.g. the tsx wrapper between us and the server).
+    serverProcess.stdin?.end();
+    killGroup("SIGTERM");
     await new Promise<void>((resolve) => {
-      const onExit = () => resolve();
-      serverProcess.once("exit", onExit);
+      serverProcess.once("exit", () => resolve());
       setTimeout(() => {
-        if (!serverProcess.killed) serverProcess.kill("SIGKILL");
+        killGroup("SIGKILL");
         setTimeout(resolve, 500);
       }, 2000);
     });