Extract hooks into dedicated crate (#11311)

Summary
- move `core/src/hooks` implementation into a new `codex-hooks` crate
with its own manifest
- update `codex-rs` workspace and `codex-core` crate to depend on the
extracted `hooks` crate and wire up the shared APIs
- ensure references, modules, and lockfile reflect the new crate layout

Testing
- Not run (not requested)

codex-rs/hooks/src/lib.rs

@@ -0,0 +1,13 @@
+mod registry;
+mod types;
+mod user_notification;
+
+pub use registry::Hooks;
+pub use registry::command_from_argv;
+pub use types::Hook;
+pub use types::HookEvent;
+pub use types::HookEventAfterAgent;
+pub use types::HookOutcome;
+pub use types::HookPayload;
+pub use user_notification::legacy_notify_json;
+pub use user_notification::notify_hook;

codex-rs/hooks/src/registry.rs

@@ -0,0 +1,298 @@
+use tokio::process::Command;
+
+use crate::types::Hook;
+use crate::types::HookEvent;
+use crate::types::HookOutcome;
+use crate::types::HookPayload;
+
+#[derive(Default, Clone)]
+pub struct Hooks {
+    after_agent: Vec<Hook>,
+}
+
+// Hooks are arbitrary, user-specified functions that are deterministically
+// executed after specific events in the Codex lifecycle.
+impl Hooks {
+    pub fn new(notify: Option<Vec<String>>) -> Self {
+        let after_agent = notify
+            .filter(|argv| !argv.is_empty() && !argv[0].is_empty())
+            .map(crate::notify_hook)
+            .into_iter()
+            .collect();
+        Self { after_agent }
+    }
+
+    fn hooks_for_event(&self, hook_event: &HookEvent) -> &[Hook] {
+        match hook_event {
+            HookEvent::AfterAgent { .. } => &self.after_agent,
+        }
+    }
+
+    pub async fn dispatch(&self, hook_payload: HookPayload) {
+        // TODO(gt): support interrupting program execution by returning a result here.
+        for hook in self.hooks_for_event(&hook_payload.hook_event) {
+            let outcome = hook.execute(&hook_payload).await;
+            if matches!(outcome, HookOutcome::Stop) {
+                break;
+            }
+        }
+    }
+}
+
+pub fn command_from_argv(argv: &[String]) -> Option<Command> {
+    let (program, args) = argv.split_first()?;
+    if program.is_empty() {
+        return None;
+    }
+    let mut command = Command::new(program);
+    command.args(args);
+    Some(command)
+}
+
+#[cfg(test)]
+mod tests {
+    use std::fs;
+    use std::path::PathBuf;
+    use std::process::Stdio;
+    use std::sync::Arc;
+    use std::sync::atomic::AtomicUsize;
+    use std::sync::atomic::Ordering;
+    use std::time::Duration;
+
+    use anyhow::Result;
+    use chrono::TimeZone;
+    use chrono::Utc;
+    use codex_protocol::ThreadId;
+    use pretty_assertions::assert_eq;
+    use serde_json::to_string;
+    use tempfile::tempdir;
+    use tokio::time::timeout;
+
+    use super::*;
+    use crate::types::HookEventAfterAgent;
+
+    const CWD: &str = "/tmp";
+    const INPUT_MESSAGE: &str = "hello";
+
+    fn hook_payload(label: &str) -> HookPayload {
+        HookPayload {
+            session_id: ThreadId::new(),
+            cwd: PathBuf::from(CWD),
+            triggered_at: Utc
+                .with_ymd_and_hms(2025, 1, 1, 0, 0, 0)
+                .single()
+                .expect("valid timestamp"),
+            hook_event: HookEvent::AfterAgent {
+                event: HookEventAfterAgent {
+                    thread_id: ThreadId::new(),
+                    turn_id: format!("turn-{label}"),
+                    input_messages: vec![INPUT_MESSAGE.to_string()],
+                    last_assistant_message: Some("hi".to_string()),
+                },
+            },
+        }
+    }
+
+    fn counting_hook(calls: &Arc<AtomicUsize>, outcome: HookOutcome) -> Hook {
+        let calls = Arc::clone(calls);
+        Hook {
+            func: Arc::new(move |_| {
+                let calls = Arc::clone(&calls);
+                Box::pin(async move {
+                    calls.fetch_add(1, Ordering::SeqCst);
+                    outcome
+                })
+            }),
+        }
+    }
+
+    fn hooks_for_after_agent(hooks: Vec<Hook>) -> Hooks {
+        Hooks { after_agent: hooks }
+    }
+
+    #[test]
+    fn command_from_argv_returns_none_for_empty_args() {
+        assert!(command_from_argv(&[]).is_none());
+        assert!(command_from_argv(&["".to_string()]).is_none());
+    }
+
+    #[tokio::test]
+    async fn command_from_argv_builds_command() -> Result<()> {
+        let argv = if cfg!(windows) {
+            vec![
+                "cmd".to_string(),
+                "/C".to_string(),
+                "echo hello world".to_string(),
+            ]
+        } else {
+            vec!["echo".to_string(), "hello".to_string(), "world".to_string()]
+        };
+        let mut command = command_from_argv(&argv).ok_or_else(|| anyhow::anyhow!("command"))?;
+        let output = command.stdout(Stdio::piped()).output().await?;
+
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        let trimmed = stdout.trim_end_matches(['\r', '\n']);
+        assert_eq!(trimmed, "hello world");
+        Ok(())
+    }
+
+    #[test]
+    fn hooks_new_requires_program_name() {
+        assert!(Hooks::new(None).after_agent.is_empty());
+        assert!(Hooks::new(Some(vec![])).after_agent.is_empty());
+        assert!(
+            Hooks::new(Some(vec!["".to_string()]))
+                .after_agent
+                .is_empty()
+        );
+        assert_eq!(
+            Hooks::new(Some(vec!["notify-send".to_string()]))
+                .after_agent
+                .len(),
+            1
+        );
+    }
+
+    #[tokio::test]
+    async fn dispatch_executes_hook() {
+        let calls = Arc::new(AtomicUsize::new(0));
+        let hooks = hooks_for_after_agent(vec![counting_hook(&calls, HookOutcome::Continue)]);
+
+        hooks.dispatch(hook_payload("1")).await;
+        assert_eq!(calls.load(Ordering::SeqCst), 1);
+    }
+
+    #[tokio::test]
+    async fn default_hook_is_noop_and_continues() {
+        let payload = hook_payload("d");
+        let outcome = Hook::default().execute(&payload).await;
+        assert_eq!(outcome, HookOutcome::Continue);
+    }
+
+    #[tokio::test]
+    async fn dispatch_executes_multiple_hooks_for_same_event() {
+        let calls = Arc::new(AtomicUsize::new(0));
+        let hooks = hooks_for_after_agent(vec![
+            counting_hook(&calls, HookOutcome::Continue),
+            counting_hook(&calls, HookOutcome::Continue),
+        ]);
+
+        hooks.dispatch(hook_payload("2")).await;
+        assert_eq!(calls.load(Ordering::SeqCst), 2);
+    }
+
+    #[tokio::test]
+    async fn dispatch_stops_when_hook_returns_stop() {
+        let calls = Arc::new(AtomicUsize::new(0));
+        let hooks = hooks_for_after_agent(vec![
+            counting_hook(&calls, HookOutcome::Stop),
+            counting_hook(&calls, HookOutcome::Continue),
+        ]);
+
+        hooks.dispatch(hook_payload("3")).await;
+        assert_eq!(calls.load(Ordering::SeqCst), 1);
+    }
+
+    #[cfg(not(windows))]
+    #[tokio::test]
+    async fn hook_executes_program_with_payload_argument_unix() -> Result<()> {
+        let temp_dir = tempdir()?;
+        let payload_path = temp_dir.path().join("payload.json");
+        let payload_path_arg = payload_path.to_string_lossy().into_owned();
+        let hook = Hook {
+            func: Arc::new(move |payload: &HookPayload| {
+                let payload_path_arg = payload_path_arg.clone();
+                Box::pin(async move {
+                    let json = to_string(payload).expect("serialize hook payload");
+                    let mut command = command_from_argv(&[
+                        "/bin/sh".to_string(),
+                        "-c".to_string(),
+                        "printf '%s' \"$2\" > \"$1\"".to_string(),
+                        "sh".to_string(),
+                        payload_path_arg,
+                        json,
+                    ])
+                    .expect("build command");
+                    command.status().await.expect("run hook command");
+                    HookOutcome::Continue
+                })
+            }),
+        };
+
+        let payload = hook_payload("4");
+        let expected = to_string(&payload)?;
+
+        let hooks = hooks_for_after_agent(vec![hook]);
+        hooks.dispatch(payload).await;
+
+        let contents = timeout(Duration::from_secs(2), async {
+            loop {
+                if let Ok(contents) = fs::read_to_string(&payload_path)
+                    && !contents.is_empty()
+                {
+                    return contents;
+                }
+                tokio::time::sleep(Duration::from_millis(10)).await;
+            }
+        })
+        .await?;
+
+        assert_eq!(contents, expected);
+        Ok(())
+    }
+
+    #[cfg(windows)]
+    #[tokio::test]
+    async fn hook_executes_program_with_payload_argument_windows() -> Result<()> {
+        let temp_dir = tempdir()?;
+        let payload_path = temp_dir.path().join("payload.json");
+        let payload_path_arg = payload_path.to_string_lossy().into_owned();
+        let script_path = temp_dir.path().join("write_payload.ps1");
+        fs::write(&script_path, "[IO.File]::WriteAllText($args[0], $args[1])")?;
+        let script_path_arg = script_path.to_string_lossy().into_owned();
+        let hook = Hook {
+            func: Arc::new(move |payload: &HookPayload| {
+                let payload_path_arg = payload_path_arg.clone();
+                let script_path_arg = script_path_arg.clone();
+                Box::pin(async move {
+                    let json = to_string(payload).expect("serialize hook payload");
+                    let mut command = command_from_argv(&[
+                        "powershell.exe".to_string(),
+                        "-NoLogo".to_string(),
+                        "-NoProfile".to_string(),
+                        "-ExecutionPolicy".to_string(),
+                        "Bypass".to_string(),
+                        "-File".to_string(),
+                        script_path_arg,
+                        payload_path_arg,
+                        json,
+                    ])
+                    .expect("build command");
+                    command.status().await.expect("run hook command");
+                    HookOutcome::Continue
+                })
+            }),
+        };
+
+        let payload = hook_payload("4");
+        let expected = to_string(&payload)?;
+
+        let hooks = hooks_for_after_agent(vec![hook]);
+        hooks.dispatch(payload).await;
+
+        let contents = timeout(Duration::from_secs(2), async {
+            loop {
+                if let Ok(contents) = fs::read_to_string(&payload_path)
+                    && !contents.is_empty()
+                {
+                    return contents;
+                }
+                tokio::time::sleep(Duration::from_millis(10)).await;
+            }
+        })
+        .await?;
+
+        assert_eq!(contents, expected);
+        Ok(())
+    }
+}

codex-rs/hooks/src/types.rs

@@ -0,0 +1,126 @@
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use chrono::DateTime;
+use chrono::SecondsFormat;
+use chrono::Utc;
+use codex_protocol::ThreadId;
+use futures::future::BoxFuture;
+use serde::Serialize;
+use serde::Serializer;
+
+pub type HookFn = Arc<dyn for<'a> Fn(&'a HookPayload) -> BoxFuture<'a, HookOutcome> + Send + Sync>;
+
+#[derive(Clone)]
+pub struct Hook {
+    pub func: HookFn,
+}
+
+impl Default for Hook {
+    fn default() -> Self {
+        Self {
+            func: Arc::new(|_| Box::pin(async { HookOutcome::Continue })),
+        }
+    }
+}
+
+impl Hook {
+    pub async fn execute(&self, payload: &HookPayload) -> HookOutcome {
+        (self.func)(payload).await
+    }
+}
+
+#[derive(Debug, Serialize, Clone)]
+#[serde(rename_all = "snake_case")]
+pub struct HookPayload {
+    pub session_id: ThreadId,
+    pub cwd: PathBuf,
+    #[serde(serialize_with = "serialize_triggered_at")]
+    pub triggered_at: DateTime<Utc>,
+    pub hook_event: HookEvent,
+}
+
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub struct HookEventAfterAgent {
+    pub thread_id: ThreadId,
+    pub turn_id: String,
+    pub input_messages: Vec<String>,
+    pub last_assistant_message: Option<String>,
+}
+
+fn serialize_triggered_at<S>(value: &DateTime<Utc>, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    serializer.serialize_str(&value.to_rfc3339_opts(SecondsFormat::Secs, true))
+}
+
+#[derive(Debug, Clone, Serialize)]
+#[serde(tag = "event_type", rename_all = "snake_case")]
+pub enum HookEvent {
+    AfterAgent {
+        #[serde(flatten)]
+        event: HookEventAfterAgent,
+    },
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum HookOutcome {
+    Continue,
+    #[allow(dead_code)]
+    Stop,
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::PathBuf;
+
+    use chrono::TimeZone;
+    use chrono::Utc;
+    use codex_protocol::ThreadId;
+    use pretty_assertions::assert_eq;
+    use serde_json::json;
+
+    use super::HookEvent;
+    use super::HookEventAfterAgent;
+    use super::HookPayload;
+
+    #[test]
+    fn hook_payload_serializes_stable_wire_shape() {
+        let session_id = ThreadId::new();
+        let thread_id = ThreadId::new();
+        let payload = HookPayload {
+            session_id,
+            cwd: PathBuf::from("tmp"),
+            triggered_at: Utc
+                .with_ymd_and_hms(2025, 1, 1, 0, 0, 0)
+                .single()
+                .expect("valid timestamp"),
+            hook_event: HookEvent::AfterAgent {
+                event: HookEventAfterAgent {
+                    thread_id,
+                    turn_id: "turn-1".to_string(),
+                    input_messages: vec!["hello".to_string()],
+                    last_assistant_message: Some("hi".to_string()),
+                },
+            },
+        };
+
+        let actual = serde_json::to_value(payload).expect("serialize hook payload");
+        let expected = json!({
+            "session_id": session_id.to_string(),
+            "cwd": "tmp",
+            "triggered_at": "2025-01-01T00:00:00Z",
+            "hook_event": {
+                "event_type": "after_agent",
+                "thread_id": thread_id.to_string(),
+                "turn_id": "turn-1",
+                "input_messages": ["hello"],
+                "last_assistant_message": "hi",
+            },
+        });
+
+        assert_eq!(actual, expected);
+    }
+}

codex-rs/hooks/src/user_notification.rs

@@ -0,0 +1,128 @@
+use std::path::Path;
+use std::process::Stdio;
+use std::sync::Arc;
+
+use serde::Serialize;
+
+use crate::Hook;
+use crate::HookEvent;
+use crate::HookOutcome;
+use crate::HookPayload;
+use crate::command_from_argv;
+
+/// Legacy notify payload appended as the final argv argument for backward compatibility.
+#[derive(Debug, Clone, PartialEq, Serialize)]
+#[serde(tag = "type", rename_all = "kebab-case")]
+enum UserNotification {
+    #[serde(rename_all = "kebab-case")]
+    AgentTurnComplete {
+        thread_id: String,
+        turn_id: String,
+        cwd: String,
+
+        /// Messages that the user sent to the agent to initiate the turn.
+        input_messages: Vec<String>,
+
+        /// The last message sent by the assistant in the turn.
+        last_assistant_message: Option<String>,
+    },
+}
+
+pub fn legacy_notify_json(hook_event: &HookEvent, cwd: &Path) -> Result<String, serde_json::Error> {
+    serde_json::to_string(&match hook_event {
+        HookEvent::AfterAgent { event } => UserNotification::AgentTurnComplete {
+            thread_id: event.thread_id.to_string(),
+            turn_id: event.turn_id.clone(),
+            cwd: cwd.display().to_string(),
+            input_messages: event.input_messages.clone(),
+            last_assistant_message: event.last_assistant_message.clone(),
+        },
+    })
+}
+
+pub fn notify_hook(argv: Vec<String>) -> Hook {
+    let argv = Arc::new(argv);
+    Hook {
+        func: Arc::new(move |payload: &HookPayload| {
+            let argv = Arc::clone(&argv);
+            Box::pin(async move {
+                let mut command = match command_from_argv(&argv) {
+                    Some(command) => command,
+                    None => return HookOutcome::Continue,
+                };
+                if let Ok(notify_payload) = legacy_notify_json(&payload.hook_event, &payload.cwd) {
+                    command.arg(notify_payload);
+                }
+
+                // Backwards-compat: match legacy notify behavior (argv + JSON arg, fire-and-forget).
+                command
+                    .stdin(Stdio::null())
+                    .stdout(Stdio::null())
+                    .stderr(Stdio::null());
+
+                let _ = command.spawn();
+                HookOutcome::Continue
+            })
+        }),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use anyhow::Result;
+    use codex_protocol::ThreadId;
+    use pretty_assertions::assert_eq;
+    use serde_json::Value;
+    use serde_json::json;
+
+    use super::*;
+
+    fn expected_notification_json() -> Value {
+        json!({
+            "type": "agent-turn-complete",
+            "thread-id": "b5f6c1c2-1111-2222-3333-444455556666",
+            "turn-id": "12345",
+            "cwd": "/Users/example/project",
+            "input-messages": ["Rename `foo` to `bar` and update the callsites."],
+            "last-assistant-message": "Rename complete and verified `cargo build` succeeds.",
+        })
+    }
+
+    #[test]
+    fn test_user_notification() -> Result<()> {
+        let notification = UserNotification::AgentTurnComplete {
+            thread_id: "b5f6c1c2-1111-2222-3333-444455556666".to_string(),
+            turn_id: "12345".to_string(),
+            cwd: "/Users/example/project".to_string(),
+            input_messages: vec!["Rename `foo` to `bar` and update the callsites.".to_string()],
+            last_assistant_message: Some(
+                "Rename complete and verified `cargo build` succeeds.".to_string(),
+            ),
+        };
+        let serialized = serde_json::to_string(&notification)?;
+        let actual: Value = serde_json::from_str(&serialized)?;
+        assert_eq!(actual, expected_notification_json());
+        Ok(())
+    }
+
+    #[test]
+    fn legacy_notify_json_matches_historical_wire_shape() -> Result<()> {
+        let hook_event = HookEvent::AfterAgent {
+            event: crate::HookEventAfterAgent {
+                thread_id: ThreadId::from_string("b5f6c1c2-1111-2222-3333-444455556666")
+                    .expect("valid thread id"),
+                turn_id: "12345".to_string(),
+                input_messages: vec!["Rename `foo` to `bar` and update the callsites.".to_string()],
+                last_assistant_message: Some(
+                    "Rename complete and verified `cargo build` succeeds.".to_string(),
+                ),
+            },
+        };
+
+        let serialized = legacy_notify_json(&hook_event, Path::new("/Users/example/project"))?;
+        let actual: Value = serde_json::from_str(&serialized)?;
+        assert_eq!(actual, expected_notification_json());
+
+        Ok(())
+    }
+}