fix(dev): treat lock file as stale when PID matches current process (#17744) (#17754)

In Docker containers, PID namespaces reset on restart, so the new
`astro dev` process often inherits the same PID the old one had. The
lock file from the previous run persists, and the process detects
itself as the "already running" server.

Add a self-PID guard to `isLockFileProcessAlive()`: if the lock file's
PID matches `process.pid`, treat it as stale immediately. The current
process cannot be the server recorded in the lock file because it
hasn't started one yet.

Co-authored-by: factory[bot] <factory[bot]@users.noreply.github.com>

Author: astro-factory[bot]

.changeset/wicked-zebras-sip.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes the dev server refusing to start in Docker containers after a restart due to PID reuse in the lock file check

packages/astro/src/core/dev/lockfile.ts

@@ -124,6 +124,14 @@ export async function isLockFileProcessAlive(
 	data: LockFileData,
 	find: ProcessLookup = findProcess,
 ): Promise<boolean> {
+	// The current process cannot be the server recorded in the lock file — it hasn't
+	// started one yet. In Docker containers the PID namespace resets on restart, so the
+	// new `astro dev` process often inherits the same PID the old one had. Without this
+	// guard, the process detects itself as the "already running" server. (#17744)
+	if (data.pid === process.pid) {
+		return false;
+	}
+
 	if (!isProcessAlive(data.pid)) {
 		return false;
 	}

packages/astro/test/units/dev/lockfile.test.ts

@@ -220,7 +220,22 @@ describe('isAstroCommand', () => {
 });
 
 describe('isLockFileProcessAlive', () => {
-	it('returns true when the recorded process command is Astro', async () => {
+	/** A long-lived child process whose PID is alive but is not the current process. */
+	let child: ReturnType<typeof spawn>;
+	let childPid: number;
+
+	before(() => {
+		child = spawn(process.execPath, ['-e', 'setInterval(() => {}, 60_000)'], {
+			stdio: 'ignore',
+		});
+		childPid = child.pid!;
+	});
+
+	after(() => {
+		child.kill('SIGKILL');
+	});
+
+	it('returns false when the lock file PID matches the current process', async () => {
 		const data = { ...validData, pid: process.pid };
 		const findProcess = async () => [
 			{
@@ -231,15 +246,29 @@ describe('isLockFileProcessAlive', () => {
 			},
 		];
 
+		assert.equal(await isLockFileProcessAlive(data, findProcess), false);
+	});
+
+	it('returns true when the recorded process command is Astro', async () => {
+		const data = { ...validData, pid: childPid };
+		const findProcess = async () => [
+			{
+				pid: childPid,
+				ppid: process.pid,
+				name: 'node',
+				cmd: 'node /workspace/node_modules/astro/bin/astro.mjs dev',
+			},
+		];
+
 		assert.equal(await isLockFileProcessAlive(data, findProcess), true);
 	});
 
 	it('returns false when the PID belongs to another command', async () => {
-		const data = { ...validData, pid: process.pid };
+		const data = { ...validData, pid: childPid };
 		const findProcess = async () => [
 			{
-				pid: process.pid,
-				ppid: process.ppid,
+				pid: childPid,
+				ppid: process.pid,
 				name: 'node',
 				cmd: 'node /app/server.mjs',
 			},
@@ -249,7 +278,7 @@ describe('isLockFileProcessAlive', () => {
 	});
 
 	it('keeps the PID-only result when the command cannot be inspected', async () => {
-		const data = { ...validData, pid: process.pid };
+		const data = { ...validData, pid: childPid };
 
 		assert.equal(await isLockFileProcessAlive(data, async () => []), true);
 		assert.equal(