[daemon] Add app-server daemon lifecycle management (#20718)

## Why

Desktop and mobile Codex clients need a machine-readable way to
bootstrap and manage `codex app-server` on remote machines reached over
SSH. The same flow is also useful for bringing up app-server with
`remote_control` enabled on a fresh developer machine and keeping that
managed install current without requiring a human session.

## What changed

- add the new experimental `codex-app-server-daemon` crate and wire it
into `codex app-server daemon` lifecycle commands: `start`, `restart`,
`stop`, `version`, and `bootstrap`
- add explicit `enable-remote-control` and `disable-remote-control`
commands that persist the launch setting and restart a running managed
daemon so the change takes effect immediately
- emit JSON success responses for daemon commands so remote callers can
consume them directly
- support a Unix-only pidfile-backed detached backend for lifecycle
management
- assume the standalone `install.sh` layout for daemon-managed binaries
and always launch `CODEX_HOME/packages/standalone/current/codex`
- add bootstrap support for the standalone managed install plus a
detached hourly updater loop
- harden lifecycle management around concurrent operations, pidfile
ownership, stale state cleanup, updater ownership, managed-binary
preflight, Unix-only rejection, forced shutdown after the graceful
window, and updater process-group tracking/cleanup
- document the experimental Unix-only support boundary plus the
standalone bootstrap/update flow in
`codex-rs/app-server-daemon/README.md`

## Verification

- `cargo test -p codex-app-server-daemon -p codex-cli`
- live pid validation on `cb4`: `bootstrap --remote-control`, `restart`,
`version`, `stop`

## Follow-up

- Add updater self-refresh so the long-lived `pid-update-loop` can
replace its own executable image after installing a newer managed Codex
binary.

codex-rs/app-server-daemon/src/backend/mod.rs

@@ -0,0 +1,33 @@
+mod pid;
+
+use std::path::PathBuf;
+
+use serde::Serialize;
+
+pub(crate) use pid::PidBackend;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum BackendKind {
+    Pid,
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct BackendPaths {
+    pub(crate) codex_bin: PathBuf,
+    pub(crate) pid_file: PathBuf,
+    pub(crate) update_pid_file: PathBuf,
+    pub(crate) remote_control_enabled: bool,
+}
+
+pub(crate) fn pid_backend(paths: BackendPaths) -> PidBackend {
+    PidBackend::new(
+        paths.codex_bin,
+        paths.pid_file,
+        paths.remote_control_enabled,
+    )
+}
+
+pub(crate) fn pid_update_loop_backend(paths: BackendPaths) -> PidBackend {
+    PidBackend::new_update_loop(paths.codex_bin, paths.update_pid_file)
+}

codex-rs/app-server-daemon/src/backend/pid.rs

@@ -0,0 +1,600 @@
+use std::path::Path;
+use std::path::PathBuf;
+#[cfg(unix)]
+use std::process::Stdio;
+use std::time::Duration;
+
+use anyhow::Context;
+use anyhow::Result;
+use anyhow::bail;
+use serde::Deserialize;
+use serde::Serialize;
+use tokio::fs;
+#[cfg(unix)]
+use tokio::process::Command;
+use tokio::time::sleep;
+
+const STOP_POLL_INTERVAL: Duration = Duration::from_millis(50);
+const STOP_GRACE_PERIOD: Duration = Duration::from_secs(60);
+const STOP_TIMEOUT: Duration = Duration::from_secs(70);
+const START_TIMEOUT: Duration = Duration::from_secs(10);
+
+#[derive(Debug)]
+#[cfg_attr(not(unix), allow(dead_code))]
+pub(crate) struct PidBackend {
+    codex_bin: PathBuf,
+    pid_file: PathBuf,
+    lock_file: PathBuf,
+    command_kind: PidCommandKind,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct PidRecord {
+    pid: u32,
+    process_start_time: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum PidFileState {
+    Missing,
+    Starting,
+    Running(PidRecord),
+}
+
+#[derive(Debug, Clone, Copy)]
+#[cfg_attr(not(unix), allow(dead_code))]
+enum PidCommandKind {
+    AppServer { remote_control_enabled: bool },
+    UpdateLoop,
+}
+
+impl PidBackend {
+    pub(crate) fn new(codex_bin: PathBuf, pid_file: PathBuf, remote_control_enabled: bool) -> Self {
+        let lock_file = pid_file.with_extension("pid.lock");
+        Self {
+            codex_bin,
+            pid_file,
+            lock_file,
+            command_kind: PidCommandKind::AppServer {
+                remote_control_enabled,
+            },
+        }
+    }
+
+    pub(crate) fn new_update_loop(codex_bin: PathBuf, pid_file: PathBuf) -> Self {
+        let lock_file = pid_file.with_extension("pid.lock");
+        Self {
+            codex_bin,
+            pid_file,
+            lock_file,
+            command_kind: PidCommandKind::UpdateLoop,
+        }
+    }
+
+    pub(crate) async fn is_starting_or_running(&self) -> Result<bool> {
+        loop {
+            match self.read_pid_file_state().await? {
+                PidFileState::Missing => return Ok(false),
+                PidFileState::Starting => return Ok(true),
+                PidFileState::Running(record) => {
+                    if self.record_is_active(&record).await? {
+                        return Ok(true);
+                    }
+                    match self.refresh_after_stale_record(&record).await? {
+                        PidFileState::Missing => return Ok(false),
+                        PidFileState::Starting | PidFileState::Running(_) => continue,
+                    }
+                }
+            }
+        }
+    }
+
+    #[cfg(unix)]
+    pub(crate) async fn start(&self) -> Result<Option<u32>> {
+        if let Some(parent) = self.pid_file.parent() {
+            fs::create_dir_all(parent)
+                .await
+                .with_context(|| format!("failed to create pid directory {}", parent.display()))?;
+        }
+        let reservation_lock = self.acquire_reservation_lock().await?;
+        let _pid_file = loop {
+            match fs::OpenOptions::new()
+                .create_new(true)
+                .write(true)
+                .open(&self.pid_file)
+                .await
+            {
+                Ok(pid_file) => break pid_file,
+                Err(err) if err.kind() == std::io::ErrorKind::AlreadyExists => {
+                    match self.read_pid_file_state_with_lock_held().await? {
+                        PidFileState::Missing => continue,
+                        PidFileState::Running(record) => {
+                            if self.record_is_active(&record).await? {
+                                return Ok(None);
+                            }
+                            let _ = fs::remove_file(&self.pid_file).await;
+                            continue;
+                        }
+                        PidFileState::Starting => {
+                            unreachable!("lock holder cannot observe starting")
+                        }
+                    }
+                }
+                Err(err) => {
+                    return Err(err).with_context(|| {
+                        format!("failed to reserve pid file {}", self.pid_file.display())
+                    });
+                }
+            }
+        };
+        let mut command = Command::new(&self.codex_bin);
+        command
+            .args(self.command_args())
+            .stdin(Stdio::null())
+            .stdout(Stdio::null())
+            .stderr(Stdio::null());
+
+        #[cfg(unix)]
+        {
+            unsafe {
+                command.pre_exec(|| {
+                    if libc::setsid() == -1 {
+                        return Err(std::io::Error::last_os_error());
+                    }
+                    Ok(())
+                });
+            }
+        }
+
+        let child = match command.spawn() {
+            Ok(child) => child,
+            Err(err) => {
+                let _ = fs::remove_file(&self.pid_file).await;
+                return Err(err).with_context(|| {
+                    format!(
+                        "failed to spawn detached app-server process using {}",
+                        self.codex_bin.display()
+                    )
+                });
+            }
+        };
+        let pid = child
+            .id()
+            .context("spawned app-server process has no pid")?;
+        let record = match read_process_start_time(pid).await {
+            Ok(process_start_time) => PidRecord {
+                pid,
+                process_start_time,
+            },
+            Err(err) => {
+                let _ = self.terminate_process(pid);
+                let _ = fs::remove_file(&self.pid_file).await;
+                return Err(err);
+            }
+        };
+        let contents = serde_json::to_vec(&record).context("failed to serialize pid record")?;
+        let temp_pid_file = self.pid_file.with_extension("pid.tmp");
+        if let Err(err) = fs::write(&temp_pid_file, &contents).await {
+            let _ = self.terminate_process(pid);
+            let _ = fs::remove_file(&self.pid_file).await;
+            return Err(err).with_context(|| {
+                format!("failed to write pid temp file {}", temp_pid_file.display())
+            });
+        }
+        if let Err(err) = fs::rename(&temp_pid_file, &self.pid_file).await {
+            let _ = self.terminate_process(pid);
+            let _ = fs::remove_file(&temp_pid_file).await;
+            let _ = fs::remove_file(&self.pid_file).await;
+            return Err(err).with_context(|| {
+                format!("failed to publish pid file {}", self.pid_file.display())
+            });
+        }
+        drop(reservation_lock);
+        Ok(Some(pid))
+    }
+
+    #[cfg(not(unix))]
+    pub(crate) async fn start(&self) -> Result<Option<u32>> {
+        bail!("pid-managed app-server startup is unsupported on this platform")
+    }
+
+    pub(crate) async fn stop(&self) -> Result<()> {
+        loop {
+            let Some(record) = self.wait_for_pid_start().await? else {
+                return Ok(());
+            };
+            if !self.record_is_active(&record).await? {
+                match self.refresh_after_stale_record(&record).await? {
+                    PidFileState::Missing => return Ok(()),
+                    PidFileState::Starting | PidFileState::Running(_) => continue,
+                }
+            }
+
+            let pid = record.pid;
+            self.terminate_process(pid)?;
+            let started_at = tokio::time::Instant::now();
+            let deadline = tokio::time::Instant::now() + STOP_TIMEOUT;
+            let mut forced = false;
+            while tokio::time::Instant::now() < deadline {
+                if !self.record_is_active(&record).await? {
+                    match self.refresh_after_stale_record(&record).await? {
+                        PidFileState::Missing => return Ok(()),
+                        PidFileState::Starting | PidFileState::Running(_) => break,
+                    }
+                }
+                if !forced && started_at.elapsed() >= STOP_GRACE_PERIOD {
+                    self.force_terminate_process(pid)?;
+                    forced = true;
+                }
+                sleep(STOP_POLL_INTERVAL).await;
+            }
+
+            if self.record_is_active(&record).await? {
+                bail!("timed out waiting for pid-managed app server {pid} to stop");
+            }
+        }
+    }
+
+    async fn wait_for_pid_start(&self) -> Result<Option<PidRecord>> {
+        let deadline = tokio::time::Instant::now() + START_TIMEOUT;
+        loop {
+            match self.read_pid_file_state().await? {
+                PidFileState::Missing => return Ok(None),
+                PidFileState::Running(record) => return Ok(Some(record)),
+                PidFileState::Starting if tokio::time::Instant::now() < deadline => {
+                    sleep(STOP_POLL_INTERVAL).await;
+                }
+                PidFileState::Starting => {
+                    bail!(
+                        "timed out waiting for pid reservation in {} to finish initializing",
+                        self.pid_file.display()
+                    );
+                }
+            }
+        }
+    }
+
+    async fn read_pid_file_state(&self) -> Result<PidFileState> {
+        let contents = match fs::read_to_string(&self.pid_file).await {
+            Ok(contents) => contents,
+            Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
+                return if reservation_lock_is_active(&self.lock_file).await? {
+                    Ok(PidFileState::Starting)
+                } else {
+                    Ok(PidFileState::Missing)
+                };
+            }
+            Err(err) => {
+                return Err(err).with_context(|| {
+                    format!("failed to read pid file {}", self.pid_file.display())
+                });
+            }
+        };
+        if contents.trim().is_empty() {
+            match inspect_empty_pid_reservation(&self.pid_file, &self.lock_file).await? {
+                EmptyPidReservation::Active => {
+                    return Ok(PidFileState::Starting);
+                }
+                EmptyPidReservation::Stale => {
+                    return Ok(PidFileState::Missing);
+                }
+                EmptyPidReservation::Record(record) => return Ok(PidFileState::Running(record)),
+            }
+        }
+        let record = serde_json::from_str(&contents)
+            .with_context(|| format!("invalid pid file contents in {}", self.pid_file.display()))?;
+        Ok(PidFileState::Running(record))
+    }
+
+    async fn read_pid_file_state_with_lock_held(&self) -> Result<PidFileState> {
+        let contents = match fs::read_to_string(&self.pid_file).await {
+            Ok(contents) => contents,
+            Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
+                return Ok(PidFileState::Missing);
+            }
+            Err(err) => {
+                return Err(err).with_context(|| {
+                    format!("failed to read pid file {}", self.pid_file.display())
+                });
+            }
+        };
+        if contents.trim().is_empty() {
+            let _ = fs::remove_file(&self.pid_file).await;
+            return Ok(PidFileState::Missing);
+        }
+        let record = serde_json::from_str(&contents)
+            .with_context(|| format!("invalid pid file contents in {}", self.pid_file.display()))?;
+        Ok(PidFileState::Running(record))
+    }
+
+    async fn refresh_after_stale_record(&self, expected: &PidRecord) -> Result<PidFileState> {
+        let reservation_lock = self.acquire_reservation_lock().await?;
+        let state = match self.read_pid_file_state_with_lock_held().await? {
+            PidFileState::Running(record) if record == *expected => {
+                let _ = fs::remove_file(&self.pid_file).await;
+                PidFileState::Missing
+            }
+            state => state,
+        };
+        drop(reservation_lock);
+        Ok(state)
+    }
+
+    async fn acquire_reservation_lock(&self) -> Result<fs::File> {
+        let reservation_lock = fs::OpenOptions::new()
+            .create(true)
+            .truncate(false)
+            .write(true)
+            .open(&self.lock_file)
+            .await
+            .with_context(|| {
+                format!("failed to open pid lock file {}", self.lock_file.display())
+            })?;
+        let lock_deadline = tokio::time::Instant::now() + START_TIMEOUT;
+        while !try_lock_file(&reservation_lock)? {
+            if tokio::time::Instant::now() >= lock_deadline {
+                bail!(
+                    "timed out waiting for pid lock {}",
+                    self.lock_file.display()
+                );
+            }
+            sleep(STOP_POLL_INTERVAL).await;
+        }
+        Ok(reservation_lock)
+    }
+
+    #[cfg(unix)]
+    fn command_args(&self) -> Vec<&'static str> {
+        match self.command_kind {
+            PidCommandKind::AppServer {
+                remote_control_enabled: true,
+            } => vec![
+                "--enable",
+                "remote_control",
+                "app-server",
+                "--listen",
+                "unix://",
+            ],
+            PidCommandKind::AppServer {
+                remote_control_enabled: false,
+            } => vec!["app-server", "--listen", "unix://"],
+            PidCommandKind::UpdateLoop => vec!["app-server", "daemon", "pid-update-loop"],
+        }
+    }
+
+    fn terminate_process(&self, pid: u32) -> Result<()> {
+        match self.command_kind {
+            PidCommandKind::AppServer { .. } => terminate_process(pid),
+            PidCommandKind::UpdateLoop => terminate_process(pid),
+        }
+    }
+
+    fn force_terminate_process(&self, pid: u32) -> Result<()> {
+        match self.command_kind {
+            PidCommandKind::AppServer { .. } => force_terminate_process(pid),
+            PidCommandKind::UpdateLoop => force_terminate_process_group(pid),
+        }
+    }
+
+    async fn record_is_active(&self, record: &PidRecord) -> Result<bool> {
+        process_matches_record(record).await
+    }
+}
+
+#[cfg(unix)]
+fn process_exists(pid: u32) -> bool {
+    let Ok(pid) = libc::pid_t::try_from(pid) else {
+        return false;
+    };
+    let result = unsafe { libc::kill(pid, 0) };
+    result == 0 || std::io::Error::last_os_error().raw_os_error() == Some(libc::EPERM)
+}
+
+#[cfg(unix)]
+fn terminate_process(pid: u32) -> Result<()> {
+    let raw_pid = libc::pid_t::try_from(pid)
+        .with_context(|| format!("pid-managed app server pid {pid} is out of range"))?;
+    let result = unsafe { libc::kill(raw_pid, libc::SIGTERM) };
+    if result == 0 {
+        return Ok(());
+    }
+    let err = std::io::Error::last_os_error();
+    if err.raw_os_error() == Some(libc::ESRCH) {
+        return Ok(());
+    }
+    Err(err).with_context(|| format!("failed to terminate pid-managed app server {pid}"))
+}
+
+#[cfg(unix)]
+fn force_terminate_process(pid: u32) -> Result<()> {
+    let raw_pid = libc::pid_t::try_from(pid)
+        .with_context(|| format!("pid-managed app server pid {pid} is out of range"))?;
+    let result = unsafe { libc::kill(raw_pid, libc::SIGKILL) };
+    if result == 0 {
+        return Ok(());
+    }
+    let err = std::io::Error::last_os_error();
+    if err.raw_os_error() == Some(libc::ESRCH) {
+        return Ok(());
+    }
+    Err(err).with_context(|| format!("failed to force terminate pid-managed app server {pid}"))
+}
+
+#[cfg(unix)]
+fn force_terminate_process_group(pid: u32) -> Result<()> {
+    let raw_pid = libc::pid_t::try_from(pid)
+        .with_context(|| format!("pid-managed updater pid {pid} is out of range"))?;
+    let result = unsafe { libc::kill(-raw_pid, libc::SIGKILL) };
+    if result == 0 {
+        return Ok(());
+    }
+    let err = std::io::Error::last_os_error();
+    if err.raw_os_error() == Some(libc::ESRCH) {
+        return Ok(());
+    }
+    Err(err).with_context(|| format!("failed to force terminate pid-managed updater group {pid}"))
+}
+
+#[cfg(not(unix))]
+fn terminate_process(_pid: u32) -> Result<()> {
+    bail!("pid-managed app-server shutdown is unsupported on this platform")
+}
+
+#[cfg(not(unix))]
+fn force_terminate_process(_pid: u32) -> Result<()> {
+    bail!("pid-managed app-server shutdown is unsupported on this platform")
+}
+
+#[cfg(not(unix))]
+fn force_terminate_process_group(_pid: u32) -> Result<()> {
+    bail!("pid-managed updater shutdown is unsupported on this platform")
+}
+
+#[cfg(unix)]
+async fn process_matches_record(record: &PidRecord) -> Result<bool> {
+    if !process_exists(record.pid) {
+        return Ok(false);
+    }
+
+    match read_process_start_time(record.pid).await {
+        Ok(start_time) => Ok(start_time == record.process_start_time),
+        Err(_err) if !process_exists(record.pid) => Ok(false),
+        Err(err) => Err(err),
+    }
+}
+
+#[cfg(not(unix))]
+async fn process_matches_record(_record: &PidRecord) -> Result<bool> {
+    Ok(false)
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[cfg_attr(not(unix), allow(dead_code))]
+enum EmptyPidReservation {
+    Active,
+    Stale,
+    Record(PidRecord),
+}
+
+#[cfg(unix)]
+fn try_lock_file(file: &fs::File) -> Result<bool> {
+    use std::os::fd::AsRawFd;
+
+    let result = unsafe { libc::flock(file.as_raw_fd(), libc::LOCK_EX | libc::LOCK_NB) };
+    if result == 0 {
+        return Ok(true);
+    }
+
+    let err = std::io::Error::last_os_error();
+    if err.raw_os_error() == Some(libc::EWOULDBLOCK) {
+        return Ok(false);
+    }
+    Err(err).context("failed to lock pid reservation")
+}
+
+#[cfg(not(unix))]
+fn try_lock_file(_file: &fs::File) -> Result<bool> {
+    bail!("pid-managed app-server startup is unsupported on this platform")
+}
+
+#[cfg(unix)]
+async fn reservation_lock_is_active(path: &Path) -> Result<bool> {
+    let file = match fs::OpenOptions::new()
+        .write(true)
+        .create(true)
+        .truncate(false)
+        .open(path)
+        .await
+    {
+        Ok(file) => file,
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
+            return Ok(false);
+        }
+        Err(err) => {
+            return Err(err)
+                .with_context(|| format!("failed to inspect pid lock file {}", path.display()));
+        }
+    };
+    Ok(!try_lock_file(&file)?)
+}
+
+#[cfg(not(unix))]
+async fn reservation_lock_is_active(_path: &Path) -> Result<bool> {
+    Ok(false)
+}
+
+#[cfg(unix)]
+async fn inspect_empty_pid_reservation(
+    pid_path: &Path,
+    lock_path: &Path,
+) -> Result<EmptyPidReservation> {
+    let file = match fs::OpenOptions::new()
+        .write(true)
+        .create(true)
+        .truncate(false)
+        .open(lock_path)
+        .await
+    {
+        Ok(file) => file,
+        Err(err) => {
+            return Err(err).with_context(|| {
+                format!("failed to inspect pid lock file {}", lock_path.display())
+            });
+        }
+    };
+    if !try_lock_file(&file)? {
+        return Ok(EmptyPidReservation::Active);
+    }
+
+    let contents = match fs::read_to_string(pid_path).await {
+        Ok(contents) => contents,
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
+            return Ok(EmptyPidReservation::Stale);
+        }
+        Err(err) => {
+            return Err(err)
+                .with_context(|| format!("failed to reread pid file {}", pid_path.display()));
+        }
+    };
+    if contents.trim().is_empty() {
+        let _ = fs::remove_file(pid_path).await;
+        return Ok(EmptyPidReservation::Stale);
+    }
+
+    let record = serde_json::from_str(&contents)
+        .with_context(|| format!("invalid pid file contents in {}", pid_path.display()))?;
+    Ok(EmptyPidReservation::Record(record))
+}
+
+#[cfg(not(unix))]
+async fn inspect_empty_pid_reservation(
+    _pid_path: &Path,
+    _lock_path: &Path,
+) -> Result<EmptyPidReservation> {
+    Ok(EmptyPidReservation::Stale)
+}
+
+#[cfg(unix)]
+async fn read_process_start_time(pid: u32) -> Result<String> {
+    let output = Command::new("ps")
+        .args(["-p", &pid.to_string(), "-o", "lstart="])
+        .output()
+        .await
+        .context("failed to invoke ps for pid-managed app server")?;
+    if !output.status.success() {
+        bail!("failed to read start time for pid-managed app server {pid}");
+    }
+
+    let start_time = String::from_utf8(output.stdout)
+        .context("pid-managed app server start time was not utf-8")?;
+    let start_time = start_time.trim();
+    if start_time.is_empty() {
+        bail!("pid-managed app server {pid} has no recorded start time");
+    }
+    Ok(start_time.to_string())
+}
+
+#[cfg(all(test, unix))]
+#[path = "pid_tests.rs"]
+mod tests;

codex-rs/app-server-daemon/src/backend/pid_tests.rs

@@ -0,0 +1,158 @@
+use std::time::Duration;
+
+use pretty_assertions::assert_eq;
+use tempfile::TempDir;
+
+use super::PidBackend;
+use super::PidCommandKind;
+use super::PidFileState;
+use super::PidRecord;
+use super::try_lock_file;
+
+#[tokio::test]
+async fn locked_empty_pid_file_is_treated_as_active_reservation() {
+    let temp_dir = TempDir::new().expect("temp dir");
+    let pid_file = temp_dir.path().join("app-server.pid");
+    tokio::fs::write(&pid_file, "")
+        .await
+        .expect("write pid file");
+    let backend = PidBackend::new(
+        temp_dir.path().join("codex"),
+        pid_file.clone(),
+        /*remote_control_enabled*/ false,
+    );
+    let reservation = tokio::fs::OpenOptions::new()
+        .create(true)
+        .truncate(false)
+        .write(true)
+        .open(&backend.lock_file)
+        .await
+        .expect("open pid lock file");
+    assert!(try_lock_file(&reservation).expect("lock reservation"));
+
+    assert_eq!(
+        backend.read_pid_file_state().await.expect("read pid"),
+        PidFileState::Starting
+    );
+    assert!(pid_file.exists());
+}
+
+#[tokio::test]
+async fn unlocked_empty_pid_file_is_treated_as_stale_reservation() {
+    let temp_dir = TempDir::new().expect("temp dir");
+    let pid_file = temp_dir.path().join("app-server.pid");
+    tokio::fs::write(&pid_file, "")
+        .await
+        .expect("write pid file");
+    let backend = PidBackend::new(
+        temp_dir.path().join("codex"),
+        pid_file.clone(),
+        /*remote_control_enabled*/ false,
+    );
+
+    assert_eq!(
+        backend.read_pid_file_state().await.expect("read pid"),
+        PidFileState::Missing
+    );
+    assert!(!pid_file.exists());
+}
+
+#[tokio::test]
+async fn stop_waits_for_live_reservation_to_resolve() {
+    let temp_dir = TempDir::new().expect("temp dir");
+    let pid_file = temp_dir.path().join("app-server.pid");
+    tokio::fs::write(&pid_file, "")
+        .await
+        .expect("write pid file");
+    let backend = PidBackend::new(
+        temp_dir.path().join("codex"),
+        pid_file.clone(),
+        /*remote_control_enabled*/ false,
+    );
+    let reservation = tokio::fs::OpenOptions::new()
+        .create(true)
+        .truncate(false)
+        .write(true)
+        .open(&backend.lock_file)
+        .await
+        .expect("open pid lock file");
+    assert!(try_lock_file(&reservation).expect("lock reservation"));
+    let cleanup = tokio::spawn(async move {
+        tokio::time::sleep(Duration::from_millis(50)).await;
+        drop(reservation);
+        tokio::fs::remove_file(pid_file)
+            .await
+            .expect("remove pid file");
+    });
+
+    backend.stop().await.expect("stop");
+    cleanup.await.expect("cleanup task");
+}
+
+#[tokio::test]
+async fn start_retries_stale_empty_pid_file_under_its_own_lock() {
+    let temp_dir = TempDir::new().expect("temp dir");
+    let pid_file = temp_dir.path().join("app-server.pid");
+    tokio::fs::write(&pid_file, "")
+        .await
+        .expect("write pid file");
+    let backend = PidBackend::new(
+        temp_dir.path().join("missing-codex"),
+        pid_file,
+        /*remote_control_enabled*/ false,
+    );
+
+    let err = backend.start().await.expect_err("start");
+    assert!(
+        err.to_string()
+            .starts_with("failed to spawn detached app-server process using ")
+    );
+}
+
+#[tokio::test]
+async fn stale_record_cleanup_preserves_replacement_record() {
+    let temp_dir = TempDir::new().expect("temp dir");
+    let pid_file = temp_dir.path().join("app-server.pid");
+    let backend = PidBackend::new(
+        temp_dir.path().join("codex"),
+        pid_file.clone(),
+        /*remote_control_enabled*/ false,
+    );
+    let stale = PidRecord {
+        pid: 1,
+        process_start_time: "old".to_string(),
+    };
+    let replacement = PidRecord {
+        pid: 2,
+        process_start_time: "new".to_string(),
+    };
+    tokio::fs::write(
+        &pid_file,
+        serde_json::to_vec(&replacement).expect("serialize replacement"),
+    )
+    .await
+    .expect("write replacement pid file");
+
+    assert_eq!(
+        backend
+            .refresh_after_stale_record(&stale)
+            .await
+            .expect("cleanup"),
+        PidFileState::Running(replacement)
+    );
+}
+
+#[test]
+fn update_loop_uses_hidden_app_server_subcommand() {
+    let backend = PidBackend {
+        codex_bin: "codex".into(),
+        pid_file: "updater.pid".into(),
+        lock_file: "updater.pid.lock".into(),
+        command_kind: PidCommandKind::UpdateLoop,
+    };
+
+    assert_eq!(
+        backend.command_args(),
+        vec!["app-server", "daemon", "pid-update-loop"]
+    );
+}

codex-rs/app-server-daemon/src/client.rs

@@ -0,0 +1,131 @@
+use std::path::Path;
+use std::time::Duration;
+
+use anyhow::Context;
+use anyhow::Result;
+use anyhow::anyhow;
+use codex_app_server_protocol::ClientInfo;
+use codex_app_server_protocol::InitializeParams;
+use codex_app_server_protocol::InitializeResponse;
+use codex_app_server_protocol::JSONRPCMessage;
+use codex_app_server_protocol::JSONRPCNotification;
+use codex_app_server_protocol::JSONRPCRequest;
+use codex_app_server_protocol::RequestId;
+use codex_uds::UnixStream;
+use futures::SinkExt;
+use futures::StreamExt;
+use tokio::time::timeout;
+use tokio_tungstenite::client_async;
+use tokio_tungstenite::tungstenite::Message;
+
+const PROBE_TIMEOUT: Duration = Duration::from_secs(2);
+const CLIENT_NAME: &str = "codex_app_server_daemon";
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) struct ProbeInfo {
+    pub(crate) app_server_version: String,
+}
+
+pub(crate) async fn probe(socket_path: &Path) -> Result<ProbeInfo> {
+    timeout(PROBE_TIMEOUT, probe_inner(socket_path))
+        .await
+        .with_context(|| {
+            format!(
+                "timed out probing app-server control socket {}",
+                socket_path.display()
+            )
+        })?
+}
+
+async fn probe_inner(socket_path: &Path) -> Result<ProbeInfo> {
+    let stream = UnixStream::connect(socket_path)
+        .await
+        .with_context(|| format!("failed to connect to {}", socket_path.display()))?;
+    let (mut websocket, _response) = client_async("ws://localhost/", stream)
+        .await
+        .with_context(|| format!("failed to upgrade {}", socket_path.display()))?;
+
+    let initialize = JSONRPCMessage::Request(JSONRPCRequest {
+        id: RequestId::Integer(1),
+        method: "initialize".to_string(),
+        params: Some(serde_json::to_value(InitializeParams {
+            client_info: ClientInfo {
+                name: CLIENT_NAME.to_string(),
+                title: Some("Codex App Server Daemon".to_string()),
+                version: env!("CARGO_PKG_VERSION").to_string(),
+            },
+            capabilities: None,
+        })?),
+        trace: None,
+    });
+    websocket
+        .send(Message::Text(serde_json::to_string(&initialize)?.into()))
+        .await
+        .context("failed to send initialize request")?;
+
+    let response = loop {
+        let frame = websocket
+            .next()
+            .await
+            .ok_or_else(|| anyhow!("app-server closed before initialize response"))??;
+        let Message::Text(payload) = frame else {
+            continue;
+        };
+        let message = serde_json::from_str::<JSONRPCMessage>(&payload)?;
+        if let JSONRPCMessage::Response(response) = message
+            && response.id == RequestId::Integer(1)
+        {
+            break response;
+        }
+    };
+    let initialize_response = serde_json::from_value::<InitializeResponse>(response.result)?;
+
+    let initialized = JSONRPCMessage::Notification(JSONRPCNotification {
+        method: "initialized".to_string(),
+        params: None,
+    });
+    websocket
+        .send(Message::Text(serde_json::to_string(&initialized)?.into()))
+        .await
+        .context("failed to send initialized notification")?;
+    websocket.close(None).await.ok();
+
+    Ok(ProbeInfo {
+        app_server_version: parse_version_from_user_agent(&initialize_response.user_agent)?,
+    })
+}
+
+fn parse_version_from_user_agent(user_agent: &str) -> Result<String> {
+    let (_originator, rest) = user_agent
+        .split_once('/')
+        .ok_or_else(|| anyhow!("app-server user-agent omitted version separator"))?;
+    let version = rest
+        .split_whitespace()
+        .next()
+        .filter(|version| !version.is_empty())
+        .ok_or_else(|| anyhow!("app-server user-agent omitted version"))?;
+    Ok(version.to_string())
+}
+
+#[cfg(all(test, unix))]
+mod tests {
+    use pretty_assertions::assert_eq;
+
+    use super::parse_version_from_user_agent;
+
+    #[test]
+    fn parses_version_from_codex_user_agent() {
+        assert_eq!(
+            parse_version_from_user_agent(
+                "codex_app_server_daemon/1.2.3 (Linux 6.8.0; x86_64) codex_cli_rs/1.2.3",
+            )
+            .expect("version"),
+            "1.2.3"
+        );
+    }
+
+    #[test]
+    fn rejects_user_agent_without_version() {
+        assert!(parse_version_from_user_agent("codex_app_server_daemon").is_err());
+    }
+}

codex-rs/app-server-daemon/src/lib.rs

@@ -0,0 +1,630 @@
+mod backend;
+mod client;
+mod managed_install;
+mod settings;
+mod update_loop;
+
+use std::path::PathBuf;
+use std::time::Duration;
+
+use anyhow::Context;
+use anyhow::Result;
+use anyhow::anyhow;
+pub use backend::BackendKind;
+use backend::BackendPaths;
+use codex_app_server_transport::app_server_control_socket_path;
+use codex_core::config::find_codex_home;
+use managed_install::managed_codex_bin;
+#[cfg(unix)]
+use managed_install::managed_codex_version;
+use serde::Serialize;
+use settings::DaemonSettings;
+use tokio::time::sleep;
+
+const START_POLL_INTERVAL: Duration = Duration::from_millis(50);
+const START_TIMEOUT: Duration = Duration::from_secs(10);
+const OPERATION_LOCK_TIMEOUT: Duration = Duration::from_secs(75);
+const PID_FILE_NAME: &str = "app-server.pid";
+const UPDATE_PID_FILE_NAME: &str = "app-server-updater.pid";
+const OPERATION_LOCK_FILE_NAME: &str = "daemon.lock";
+const SETTINGS_FILE_NAME: &str = "settings.json";
+const STATE_DIR_NAME: &str = "app-server-daemon";
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LifecycleCommand {
+    Start,
+    Restart,
+    Stop,
+    Version,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum LifecycleStatus {
+    AlreadyRunning,
+    Started,
+    Restarted,
+    Stopped,
+    NotRunning,
+    Running,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct LifecycleOutput {
+    pub status: LifecycleStatus,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub backend: Option<BackendKind>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub pid: Option<u32>,
+    pub socket_path: PathBuf,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub cli_version: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub app_server_version: Option<String>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct BootstrapOptions {
+    pub remote_control_enabled: bool,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum BootstrapStatus {
+    Bootstrapped,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct BootstrapOutput {
+    pub status: BootstrapStatus,
+    pub backend: BackendKind,
+    pub auto_update_enabled: bool,
+    pub remote_control_enabled: bool,
+    pub managed_codex_path: PathBuf,
+    pub socket_path: PathBuf,
+    pub cli_version: String,
+    pub app_server_version: String,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum RemoteControlMode {
+    Enabled,
+    Disabled,
+}
+
+impl RemoteControlMode {
+    fn is_enabled(self) -> bool {
+        matches!(self, Self::Enabled)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum RemoteControlStatus {
+    Enabled,
+    Disabled,
+    AlreadyEnabled,
+    AlreadyDisabled,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct RemoteControlOutput {
+    pub status: RemoteControlStatus,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub backend: Option<BackendKind>,
+    pub remote_control_enabled: bool,
+    pub socket_path: PathBuf,
+    pub cli_version: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub app_server_version: Option<String>,
+}
+
+#[cfg(unix)]
+pub(crate) enum RestartIfRunningOutcome {
+    Completed,
+    Busy,
+}
+
+pub async fn run(command: LifecycleCommand) -> Result<LifecycleOutput> {
+    ensure_supported_platform()?;
+    Daemon::from_environment()?.run(command).await
+}
+
+pub async fn bootstrap(options: BootstrapOptions) -> Result<BootstrapOutput> {
+    ensure_supported_platform()?;
+    Daemon::from_environment()?.bootstrap(options).await
+}
+
+pub async fn set_remote_control(mode: RemoteControlMode) -> Result<RemoteControlOutput> {
+    ensure_supported_platform()?;
+    Daemon::from_environment()?.set_remote_control(mode).await
+}
+
+pub async fn run_pid_update_loop() -> Result<()> {
+    ensure_supported_platform()?;
+    update_loop::run().await
+}
+
+#[cfg(unix)]
+fn ensure_supported_platform() -> Result<()> {
+    Ok(())
+}
+
+#[cfg(not(unix))]
+fn ensure_supported_platform() -> Result<()> {
+    Err(anyhow!(
+        "codex app-server daemon lifecycle is only supported on Unix platforms"
+    ))
+}
+
+struct Daemon {
+    socket_path: PathBuf,
+    pid_file: PathBuf,
+    update_pid_file: PathBuf,
+    operation_lock_file: PathBuf,
+    settings_file: PathBuf,
+    managed_codex_bin: PathBuf,
+}
+
+impl Daemon {
+    fn from_environment() -> Result<Self> {
+        let codex_home = find_codex_home().context("failed to resolve CODEX_HOME")?;
+        let socket_path = app_server_control_socket_path(codex_home.as_path())?
+            .as_path()
+            .to_path_buf();
+        let state_dir = codex_home.as_path().join(STATE_DIR_NAME);
+        Ok(Self {
+            socket_path,
+            pid_file: state_dir.join(PID_FILE_NAME),
+            update_pid_file: state_dir.join(UPDATE_PID_FILE_NAME),
+            operation_lock_file: state_dir.join(OPERATION_LOCK_FILE_NAME),
+            settings_file: state_dir.join(SETTINGS_FILE_NAME),
+            managed_codex_bin: managed_codex_bin(codex_home.as_path()),
+        })
+    }
+
+    async fn run(&self, command: LifecycleCommand) -> Result<LifecycleOutput> {
+        match command {
+            LifecycleCommand::Start => {
+                let _operation_lock = self.acquire_operation_lock().await?;
+                self.start().await
+            }
+            LifecycleCommand::Restart => {
+                let _operation_lock = self.acquire_operation_lock().await?;
+                self.restart().await
+            }
+            LifecycleCommand::Stop => {
+                let _operation_lock = self.acquire_operation_lock().await?;
+                self.stop().await
+            }
+            LifecycleCommand::Version => self.version().await,
+        }
+    }
+
+    async fn start(&self) -> Result<LifecycleOutput> {
+        let settings = self.load_settings().await?;
+        if let Ok(info) = client::probe(&self.socket_path).await {
+            return Ok(self.output(
+                LifecycleStatus::AlreadyRunning,
+                self.running_backend(&settings).await?,
+                /*pid*/ None,
+                Some(info.app_server_version),
+            ));
+        }
+
+        if self.running_backend_instance(&settings).await?.is_some() {
+            let info = self.wait_until_ready().await?;
+            return Ok(self.output(
+                LifecycleStatus::AlreadyRunning,
+                Some(BackendKind::Pid),
+                /*pid*/ None,
+                Some(info.app_server_version),
+            ));
+        }
+
+        self.ensure_managed_codex_bin()?;
+        let pid = self.start_managed_backend(&settings).await?;
+        let info = self.wait_until_ready().await?;
+        Ok(self.output(
+            LifecycleStatus::Started,
+            Some(BackendKind::Pid),
+            pid,
+            Some(info.app_server_version),
+        ))
+    }
+
+    async fn restart(&self) -> Result<LifecycleOutput> {
+        let settings = self.load_settings().await?;
+        if client::probe(&self.socket_path).await.is_ok()
+            && self.running_backend(&settings).await?.is_none()
+        {
+            return Err(anyhow!(
+                "app server is running but is not managed by codex app-server daemon"
+            ));
+        }
+
+        self.ensure_managed_codex_bin()?;
+        if let Some(backend) = self.running_backend_instance(&settings).await? {
+            backend.stop().await?;
+        }
+
+        let pid = self.start_managed_backend(&settings).await?;
+        let info = self.wait_until_ready().await?;
+        Ok(self.output(
+            LifecycleStatus::Restarted,
+            Some(BackendKind::Pid),
+            pid,
+            Some(info.app_server_version),
+        ))
+    }
+
+    #[cfg(unix)]
+    pub(crate) async fn try_restart_if_running(&self) -> Result<RestartIfRunningOutcome> {
+        let operation_lock = self.open_operation_lock_file().await?;
+        if !try_lock_file(&operation_lock)? {
+            return Ok(RestartIfRunningOutcome::Busy);
+        }
+        let settings = self.load_settings().await?;
+        if let Some(backend) = self.running_backend_instance(&settings).await? {
+            let Ok(info) = client::probe(&self.socket_path).await else {
+                return Ok(RestartIfRunningOutcome::Completed);
+            };
+            let managed_version = managed_codex_version(&self.managed_codex_bin).await?;
+            if info.app_server_version == managed_version {
+                return Ok(RestartIfRunningOutcome::Completed);
+            }
+            backend.stop().await?;
+            let _ = self.start_managed_backend(&settings).await?;
+            self.wait_until_ready().await?;
+            return Ok(RestartIfRunningOutcome::Completed);
+        }
+
+        if client::probe(&self.socket_path).await.is_ok() {
+            return Err(anyhow!(
+                "app server is running but is not managed by codex app-server daemon"
+            ));
+        }
+
+        Ok(RestartIfRunningOutcome::Completed)
+    }
+
+    async fn stop(&self) -> Result<LifecycleOutput> {
+        let settings = self.load_settings().await?;
+        if let Some(backend) = self.running_backend_instance(&settings).await? {
+            backend.stop().await?;
+            return Ok(self.output(
+                LifecycleStatus::Stopped,
+                Some(BackendKind::Pid),
+                /*pid*/ None,
+                /*app_server_version*/ None,
+            ));
+        }
+
+        if client::probe(&self.socket_path).await.is_ok() {
+            return Err(anyhow!(
+                "app server is running but is not managed by codex app-server daemon"
+            ));
+        }
+
+        Ok(self.output(
+            LifecycleStatus::NotRunning,
+            /*backend*/ None,
+            /*pid*/ None,
+            /*app_server_version*/ None,
+        ))
+    }
+
+    async fn version(&self) -> Result<LifecycleOutput> {
+        let settings = self.load_settings().await?;
+        let info = client::probe(&self.socket_path).await?;
+        Ok(self.output(
+            LifecycleStatus::Running,
+            self.running_backend(&settings).await?,
+            /*pid*/ None,
+            Some(info.app_server_version),
+        ))
+    }
+
+    async fn wait_until_ready(&self) -> Result<client::ProbeInfo> {
+        let deadline = tokio::time::Instant::now() + START_TIMEOUT;
+        loop {
+            match client::probe(&self.socket_path).await {
+                Ok(info) => return Ok(info),
+                Err(err) if tokio::time::Instant::now() < deadline => {
+                    let _ = err;
+                    sleep(START_POLL_INTERVAL).await;
+                }
+                Err(err) => {
+                    return Err(err).with_context(|| {
+                        format!(
+                            "app server did not become ready on {}",
+                            self.socket_path.display()
+                        )
+                    });
+                }
+            }
+        }
+    }
+
+    async fn bootstrap(&self, options: BootstrapOptions) -> Result<BootstrapOutput> {
+        let _operation_lock = self.acquire_operation_lock().await?;
+        self.bootstrap_locked(options).await
+    }
+
+    async fn set_remote_control(&self, mode: RemoteControlMode) -> Result<RemoteControlOutput> {
+        let _operation_lock = self.acquire_operation_lock().await?;
+        let previous_settings = self.load_settings().await?;
+        let mut settings = previous_settings.clone();
+        let remote_control_enabled = mode.is_enabled();
+        let backend = self.running_backend_instance(&previous_settings).await?;
+
+        if backend.is_none() && client::probe(&self.socket_path).await.is_ok() {
+            return Err(anyhow!(
+                "app server is running but is not managed by codex app-server daemon"
+            ));
+        }
+
+        if settings.remote_control_enabled == remote_control_enabled {
+            let info = if backend.is_some() {
+                Some(self.wait_until_ready().await?)
+            } else {
+                None
+            };
+            return Ok(self.remote_control_output(
+                already_remote_control_status(mode),
+                backend.map(|_| BackendKind::Pid),
+                remote_control_enabled,
+                info.map(|info| info.app_server_version),
+            ));
+        }
+
+        settings.remote_control_enabled = remote_control_enabled;
+        settings.save(&self.settings_file).await?;
+
+        let app_server_version = if let Some(backend) = backend {
+            self.ensure_managed_codex_bin()?;
+            backend.stop().await?;
+            let _ = self.start_managed_backend(&settings).await?;
+            Some(self.wait_until_ready().await?.app_server_version)
+        } else {
+            None
+        };
+
+        Ok(self.remote_control_output(
+            remote_control_status(mode),
+            app_server_version.as_ref().map(|_| BackendKind::Pid),
+            remote_control_enabled,
+            app_server_version,
+        ))
+    }
+
+    async fn bootstrap_locked(&self, options: BootstrapOptions) -> Result<BootstrapOutput> {
+        self.ensure_managed_codex_bin()?;
+
+        let settings = DaemonSettings {
+            remote_control_enabled: options.remote_control_enabled,
+        };
+        if client::probe(&self.socket_path).await.is_ok()
+            && self.running_backend(&settings).await?.is_none()
+        {
+            return Err(anyhow!(
+                "app server is running but is not managed by codex app-server daemon"
+            ));
+        }
+        settings.save(&self.settings_file).await?;
+
+        if let Some(backend) = self.running_backend_instance(&settings).await? {
+            backend.stop().await?;
+        }
+
+        let backend = backend::pid_backend(self.backend_paths(&settings));
+        backend.start().await?;
+        let updater = backend::pid_update_loop_backend(self.backend_paths(&settings));
+        if updater.is_starting_or_running().await? {
+            updater.stop().await?;
+        }
+        updater.start().await?;
+
+        let info = self.wait_until_ready().await?;
+        Ok(BootstrapOutput {
+            status: BootstrapStatus::Bootstrapped,
+            backend: BackendKind::Pid,
+            auto_update_enabled: true,
+            remote_control_enabled: settings.remote_control_enabled,
+            managed_codex_path: self.managed_codex_bin.clone(),
+            socket_path: self.socket_path.clone(),
+            cli_version: env!("CARGO_PKG_VERSION").to_string(),
+            app_server_version: info.app_server_version,
+        })
+    }
+
+    async fn running_backend(&self, settings: &DaemonSettings) -> Result<Option<BackendKind>> {
+        Ok(self
+            .running_backend_instance(settings)
+            .await?
+            .map(|_| BackendKind::Pid))
+    }
+
+    async fn running_backend_instance(
+        &self,
+        settings: &DaemonSettings,
+    ) -> Result<Option<backend::PidBackend>> {
+        let backend = backend::pid_backend(self.backend_paths(settings));
+        if backend.is_starting_or_running().await? {
+            return Ok(Some(backend));
+        }
+        Ok(None)
+    }
+
+    async fn start_managed_backend(&self, settings: &DaemonSettings) -> Result<Option<u32>> {
+        let backend = backend::pid_backend(self.backend_paths(settings));
+        backend.start().await
+    }
+
+    fn ensure_managed_codex_bin(&self) -> Result<()> {
+        if self.managed_codex_bin.is_file() {
+            return Ok(());
+        }
+
+        Err(anyhow!(
+            "managed standalone Codex install not found at {}; install Codex first",
+            self.managed_codex_bin.display()
+        ))
+    }
+
+    fn backend_paths(&self, settings: &DaemonSettings) -> BackendPaths {
+        BackendPaths {
+            codex_bin: self.managed_codex_bin.clone(),
+            pid_file: self.pid_file.clone(),
+            update_pid_file: self.update_pid_file.clone(),
+            remote_control_enabled: settings.remote_control_enabled,
+        }
+    }
+
+    async fn load_settings(&self) -> Result<DaemonSettings> {
+        DaemonSettings::load(&self.settings_file).await
+    }
+
+    async fn acquire_operation_lock(&self) -> Result<tokio::fs::File> {
+        let operation_lock = self.open_operation_lock_file().await?;
+        let deadline = tokio::time::Instant::now() + OPERATION_LOCK_TIMEOUT;
+        while !try_lock_file(&operation_lock)? {
+            if tokio::time::Instant::now() >= deadline {
+                return Err(anyhow!(
+                    "timed out waiting for daemon operation lock {}",
+                    self.operation_lock_file.display()
+                ));
+            }
+            sleep(START_POLL_INTERVAL).await;
+        }
+        Ok(operation_lock)
+    }
+
+    async fn open_operation_lock_file(&self) -> Result<tokio::fs::File> {
+        if let Some(parent) = self.operation_lock_file.parent() {
+            tokio::fs::create_dir_all(parent).await.with_context(|| {
+                format!(
+                    "failed to create daemon state directory {}",
+                    parent.display()
+                )
+            })?;
+        }
+        tokio::fs::OpenOptions::new()
+            .create(true)
+            .truncate(false)
+            .write(true)
+            .open(&self.operation_lock_file)
+            .await
+            .with_context(|| {
+                format!(
+                    "failed to open daemon operation lock {}",
+                    self.operation_lock_file.display()
+                )
+            })
+    }
+
+    fn output(
+        &self,
+        status: LifecycleStatus,
+        backend: Option<BackendKind>,
+        pid: Option<u32>,
+        app_server_version: Option<String>,
+    ) -> LifecycleOutput {
+        LifecycleOutput {
+            status,
+            backend,
+            pid,
+            socket_path: self.socket_path.clone(),
+            cli_version: Some(env!("CARGO_PKG_VERSION").to_string()),
+            app_server_version,
+        }
+    }
+
+    fn remote_control_output(
+        &self,
+        status: RemoteControlStatus,
+        backend: Option<BackendKind>,
+        remote_control_enabled: bool,
+        app_server_version: Option<String>,
+    ) -> RemoteControlOutput {
+        RemoteControlOutput {
+            status,
+            backend,
+            remote_control_enabled,
+            socket_path: self.socket_path.clone(),
+            cli_version: env!("CARGO_PKG_VERSION").to_string(),
+            app_server_version,
+        }
+    }
+}
+
+fn remote_control_status(mode: RemoteControlMode) -> RemoteControlStatus {
+    match mode {
+        RemoteControlMode::Enabled => RemoteControlStatus::Enabled,
+        RemoteControlMode::Disabled => RemoteControlStatus::Disabled,
+    }
+}
+
+fn already_remote_control_status(mode: RemoteControlMode) -> RemoteControlStatus {
+    match mode {
+        RemoteControlMode::Enabled => RemoteControlStatus::AlreadyEnabled,
+        RemoteControlMode::Disabled => RemoteControlStatus::AlreadyDisabled,
+    }
+}
+
+#[cfg(unix)]
+fn try_lock_file(file: &tokio::fs::File) -> Result<bool> {
+    use std::os::fd::AsRawFd;
+
+    let result = unsafe { libc::flock(file.as_raw_fd(), libc::LOCK_EX | libc::LOCK_NB) };
+    if result == 0 {
+        return Ok(true);
+    }
+
+    let err = std::io::Error::last_os_error();
+    if err.raw_os_error() == Some(libc::EWOULDBLOCK) {
+        return Ok(false);
+    }
+    Err(err).context("failed to lock daemon operation")
+}
+
+#[cfg(not(unix))]
+fn try_lock_file(_file: &tokio::fs::File) -> Result<bool> {
+    Ok(true)
+}
+
+#[cfg(all(test, unix))]
+mod tests {
+    use pretty_assertions::assert_eq;
+
+    use super::BootstrapStatus;
+    use super::LifecycleStatus;
+    use super::RemoteControlStatus;
+
+    #[test]
+    fn lifecycle_status_uses_camel_case_json() {
+        assert_eq!(
+            serde_json::to_string(&LifecycleStatus::AlreadyRunning).expect("serialize"),
+            "\"alreadyRunning\""
+        );
+    }
+
+    #[test]
+    fn bootstrap_status_uses_camel_case_json() {
+        assert_eq!(
+            serde_json::to_string(&BootstrapStatus::Bootstrapped).expect("serialize"),
+            "\"bootstrapped\""
+        );
+    }
+
+    #[test]
+    fn remote_control_status_uses_camel_case_json() {
+        assert_eq!(
+            serde_json::to_string(&RemoteControlStatus::AlreadyEnabled).expect("serialize"),
+            "\"alreadyEnabled\""
+        );
+    }
+}

codex-rs/app-server-daemon/src/managed_install.rs

@@ -0,0 +1,66 @@
+use std::path::Path;
+use std::path::PathBuf;
+
+#[cfg(unix)]
+use anyhow::Context;
+#[cfg(unix)]
+use anyhow::Result;
+#[cfg(unix)]
+use anyhow::anyhow;
+#[cfg(unix)]
+use tokio::process::Command;
+
+pub(crate) fn managed_codex_bin(codex_home: &Path) -> PathBuf {
+    codex_home
+        .join("packages")
+        .join("standalone")
+        .join("current")
+        .join(managed_codex_file_name())
+}
+
+#[cfg(unix)]
+pub(crate) async fn managed_codex_version(codex_bin: &Path) -> Result<String> {
+    let output = Command::new(codex_bin)
+        .arg("--version")
+        .output()
+        .await
+        .with_context(|| {
+            format!(
+                "failed to invoke managed Codex binary {}",
+                codex_bin.display()
+            )
+        })?;
+    if !output.status.success() {
+        return Err(anyhow!(
+            "managed Codex binary {} exited with status {}",
+            codex_bin.display(),
+            output.status
+        ));
+    }
+
+    let stdout = String::from_utf8(output.stdout).with_context(|| {
+        format!(
+            "managed Codex version was not utf-8: {}",
+            codex_bin.display()
+        )
+    })?;
+    parse_codex_version(&stdout)
+}
+
+fn managed_codex_file_name() -> &'static str {
+    if cfg!(windows) { "codex.exe" } else { "codex" }
+}
+
+#[cfg(unix)]
+fn parse_codex_version(output: &str) -> Result<String> {
+    let version = output
+        .split_whitespace()
+        .nth(1)
+        .filter(|version| !version.is_empty())
+        .ok_or_else(|| anyhow!("managed Codex version output was malformed"))?;
+    Ok(version.to_string())
+}
+
+#[cfg(all(test, unix))]
+#[path = "managed_install_tests.rs"]
+mod tests;

codex-rs/app-server-daemon/src/managed_install_tests.rs

@@ -0,0 +1,16 @@
+use pretty_assertions::assert_eq;
+
+use super::parse_codex_version;
+
+#[test]
+fn parses_codex_cli_version_output() {
+    assert_eq!(
+        parse_codex_version("codex 1.2.3\n").expect("version"),
+        "1.2.3"
+    );
+}
+
+#[test]
+fn rejects_malformed_codex_cli_version_output() {
+    assert!(parse_codex_version("codex\n").is_err());
+}

codex-rs/app-server-daemon/src/settings.rs

@@ -0,0 +1,63 @@
+use std::path::Path;
+
+use anyhow::Context;
+use anyhow::Result;
+use serde::Deserialize;
+use serde::Serialize;
+use tokio::fs;
+
+#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub(crate) struct DaemonSettings {
+    pub(crate) remote_control_enabled: bool,
+}
+
+impl DaemonSettings {
+    pub(crate) async fn load(path: &Path) -> Result<Self> {
+        let contents = match fs::read_to_string(path).await {
+            Ok(contents) => contents,
+            Err(err) if err.kind() == std::io::ErrorKind::NotFound => return Ok(Self::default()),
+            Err(err) => {
+                return Err(err)
+                    .with_context(|| format!("failed to read daemon settings {}", path.display()));
+            }
+        };
+
+        serde_json::from_str(&contents)
+            .with_context(|| format!("failed to parse daemon settings {}", path.display()))
+    }
+
+    pub(crate) async fn save(&self, path: &Path) -> Result<()> {
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent).await.with_context(|| {
+                format!(
+                    "failed to create daemon settings directory {}",
+                    parent.display()
+                )
+            })?;
+        }
+
+        let contents = serde_json::to_vec_pretty(self).context("failed to serialize settings")?;
+        fs::write(path, contents)
+            .await
+            .with_context(|| format!("failed to write daemon settings {}", path.display()))
+    }
+}
+
+#[cfg(all(test, unix))]
+mod tests {
+    use pretty_assertions::assert_eq;
+
+    use super::DaemonSettings;
+
+    #[test]
+    fn daemon_settings_use_camel_case_json() {
+        assert_eq!(
+            serde_json::to_string(&DaemonSettings {
+                remote_control_enabled: true,
+            })
+            .expect("serialize"),
+            r#"{"remoteControlEnabled":true}"#
+        );
+    }
+}

codex-rs/app-server-daemon/src/update_loop.rs

@@ -0,0 +1,132 @@
+#[cfg(unix)]
+use std::process::Stdio;
+#[cfg(unix)]
+use std::time::Duration;
+
+#[cfg(unix)]
+use anyhow::Context;
+use anyhow::Result;
+#[cfg(not(unix))]
+use anyhow::bail;
+#[cfg(unix)]
+use futures::FutureExt;
+#[cfg(unix)]
+use tokio::io::AsyncWriteExt;
+#[cfg(unix)]
+use tokio::process::Command;
+#[cfg(unix)]
+use tokio::signal::unix::Signal;
+#[cfg(unix)]
+use tokio::signal::unix::SignalKind;
+#[cfg(unix)]
+use tokio::signal::unix::signal;
+#[cfg(unix)]
+use tokio::time::sleep;
+
+#[cfg(unix)]
+use crate::Daemon;
+#[cfg(unix)]
+use crate::RestartIfRunningOutcome;
+
+#[cfg(unix)]
+const INITIAL_UPDATE_DELAY: Duration = Duration::from_secs(5 * 60);
+#[cfg(unix)]
+const RESTART_RETRY_INTERVAL: Duration = Duration::from_millis(50);
+#[cfg(unix)]
+const UPDATE_INTERVAL: Duration = Duration::from_secs(60 * 60);
+
+#[cfg(unix)]
+pub(crate) async fn run() -> Result<()> {
+    let mut terminate =
+        signal(SignalKind::terminate()).context("failed to install updater shutdown handler")?;
+    if sleep_or_terminate(INITIAL_UPDATE_DELAY, &mut terminate).await {
+        return Ok(());
+    }
+    loop {
+        match update_once(&mut terminate).await {
+            Ok(UpdateLoopControl::Continue) | Err(_) => {}
+            Ok(UpdateLoopControl::Stop) => return Ok(()),
+        }
+        if sleep_or_terminate(UPDATE_INTERVAL, &mut terminate).await {
+            return Ok(());
+        }
+    }
+}
+
+#[cfg(not(unix))]
+pub(crate) async fn run() -> Result<()> {
+    bail!("pid-managed updater loop is unsupported on this platform")
+}
+
+#[cfg(unix)]
+async fn sleep_or_terminate(duration: Duration, terminate: &mut Signal) -> bool {
+    tokio::select! {
+        _ = sleep(duration) => false,
+        _ = terminate.recv() => true,
+    }
+}
+
+#[cfg(unix)]
+enum UpdateLoopControl {
+    Continue,
+    Stop,
+}
+
+#[cfg(unix)]
+async fn update_once(terminate: &mut Signal) -> Result<UpdateLoopControl> {
+    install_latest_standalone().await?;
+
+    let daemon = Daemon::from_environment()?;
+    loop {
+        if terminate.recv().now_or_never().flatten().is_some() {
+            return Ok(UpdateLoopControl::Stop);
+        }
+        match daemon.try_restart_if_running().await? {
+            RestartIfRunningOutcome::Completed => return Ok(UpdateLoopControl::Continue),
+            RestartIfRunningOutcome::Busy => {
+                if sleep_or_terminate(RESTART_RETRY_INTERVAL, terminate).await {
+                    return Ok(UpdateLoopControl::Stop);
+                }
+            }
+        }
+    }
+}
+
+#[cfg(unix)]
+async fn install_latest_standalone() -> Result<()> {
+    let script = reqwest::get("https://chatgpt.com/codex/install.sh")
+        .await
+        .context("failed to fetch standalone Codex updater")?
+        .error_for_status()
+        .context("standalone Codex updater request failed")?
+        .bytes()
+        .await
+        .context("failed to read standalone Codex updater")?;
+
+    let mut child = Command::new("/bin/sh")
+        .arg("-s")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::null())
+        .stderr(Stdio::null())
+        .spawn()
+        .context("failed to invoke standalone Codex updater")?;
+    let mut stdin = child
+        .stdin
+        .take()
+        .context("standalone Codex updater stdin was unavailable")?;
+    stdin
+        .write_all(&script)
+        .await
+        .context("failed to pass standalone Codex updater to shell")?;
+    drop(stdin);
+    let status = child
+        .wait()
+        .await
+        .context("failed to wait for standalone Codex updater")?;
+
+    if status.success() {
+        Ok(())
+    } else {
+        anyhow::bail!("standalone Codex updater exited with status {status}")
+    }
+}