openlatch-client 0.6.15

//! The OpenCode session window behind `bypass_suspected` (AGT-5 C-5/C-6, Plan D-9/D-10).
//!
//! Two sides meet here, both keyed by OpenCode's own session id:
//!
//! | Side | Fed from | When |
//! | ---- | -------- | ---- |
//! | relay | a request whose `User-Agent` product token is `opencode/` and that carries a C-6 session header | in the relay handler, **before** attribution and before the request is recorded or suppressed, so a `--pure` run's id is seen even with no live session, or with an unrelated one |
//! | plugin | every OpenCode plugin event that names a session | in the hook handler, live events only |
//!
//! A session the relay saw and the plugin never reported is a suspected bypass: OpenCode ran
//! without our plugin (`--pure`, or a load failure). Kept **daemon-side only and in memory**: the
//! `User-Agent` and the session id never reach the relay record, so no schema changes, and the
//! window does not survive a daemon restart — doctor says "since daemon start" while the daemon
//! is younger than the window.
//!
//! A grace period separates the two sides: OpenCode's prompt hook decides before the model call
//! it gates, so the plugin side normally lands first, and the grace covers the capture-only
//! events that race it. Each suspected session is reported once ([`take_new_suspects`]).
//!
//! [`take_new_suspects`]: OpencodeSessionWindow::take_new_suspects

use std::collections::{HashMap, HashSet};
use std::sync::Mutex;
use std::time::{Duration, Instant};

/// How long a session id stays in the window (C-5: "in the last 24 hours").
pub const WINDOW: Duration = Duration::from_secs(24 * 60 * 60);

/// How long a relay-side id waits for its plugin report before it is suspected.
pub const GRACE: Duration = Duration::from_secs(10);

/// The most ids each side holds; the oldest is evicted first. Bounds memory on a host that runs
/// OpenCode all day.
pub const MAX_IDS: usize = 4096;

/// The product token OpenCode puts first in its `User-Agent` (`opencode/<version> ai-sdk/…`).
pub const USER_AGENT_TOKEN: &str = "opencode/";

/// Whether a `User-Agent` value is OpenCode's own (its first product token).
pub fn is_opencode_user_agent(user_agent: &str) -> bool {
    user_agent
        .trim_start()
        .get(..USER_AGENT_TOKEN.len())
        .is_some_and(|p| p.eq_ignore_ascii_case(USER_AGENT_TOKEN))
}

#[derive(Clone, Copy)]
struct RelaySeen {
    first: Instant,
    last: Instant,
}

#[derive(Default)]
struct Inner {
    /// Session id → when the relay first and last saw OpenCode traffic for it. The first sighting
    /// starts the grace; the last keeps an active session in the rolling window.
    relay: HashMap<String, RelaySeen>,
    /// Session id → when the plugin last reported it.
    plugin: HashMap<String, Instant>,
    /// Suspected sessions already reported (tamper event emitted).
    reported: HashSet<String>,
    /// The last OpenCode request the relay saw, session header or not.
    last_traffic: Option<Instant>,
    /// The same moment on the wall clock, in epoch milliseconds, for doctor to compare with the
    /// plugin file's write time.
    last_traffic_ms: Option<i64>,
}

/// The window. One per daemon, shared by the relay listeners and the hook handler.
pub struct OpencodeSessionWindow {
    inner: Mutex<Inner>,
    started: Instant,
}

impl Default for OpencodeSessionWindow {
    fn default() -> Self {
        Self::new(Instant::now())
    }
}

/// What doctor reads, through the relay's status endpoint.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct WindowSnapshot {
    /// The relay has seen OpenCode model traffic in the window.
    pub traffic: bool,
    /// When it last did, in epoch milliseconds.
    pub last_traffic_ms: Option<i64>,
    /// Sessions the relay saw that the plugin never reported, past the grace.
    pub suspected: usize,
    /// Whether the window is shorter than [`WINDOW`] because the daemon started inside it.
    pub since_daemon_start: bool,
}

impl WindowSnapshot {
    /// The `opencode` object of `GET /admin/model-relay/status`.
    pub fn to_json(&self) -> serde_json::Value {
        serde_json::json!({
            "traffic": self.traffic,
            "last_traffic_ms": self.last_traffic_ms,
            "bypass_suspected": self.suspected > 0,
            "suspected_sessions": self.suspected,
            "since_daemon_start": self.since_daemon_start,
        })
    }
}

fn lock(m: &Mutex<Inner>) -> std::sync::MutexGuard<'_, Inner> {
    m.lock().unwrap_or_else(|poisoned| poisoned.into_inner())
}

/// Insert `id`, or update it in place, evicting the entry `age` ranks oldest once `map` holds
/// [`MAX_IDS`].
fn bounded_upsert<V: Copy>(
    map: &mut HashMap<String, V>,
    id: &str,
    new: V,
    update: impl FnOnce(&mut V),
    age: impl Fn(&V) -> Instant,
) {
    if let Some(seen) = map.get_mut(id) {
        update(seen);
        return;
    }
    if map.len() >= MAX_IDS {
        if let Some(oldest) = map
            .iter()
            .min_by_key(|(_, v)| age(v))
            .map(|(k, _)| k.clone())
        {
            map.remove(&oldest);
        }
    }
    map.insert(id.to_string(), new);
}

impl OpencodeSessionWindow {
    /// A window whose daemon started at `started`.
    pub fn new(started: Instant) -> Self {
        Self {
            inner: Mutex::new(Inner::default()),
            started,
        }
    }

    /// The relay side: one OpenCode model turn naming `session_id` (the first C-6 header's
    /// value). A blank id still counts as traffic, never as a session.
    pub fn note_relay(&self, session_id: &str, now: Instant) {
        let mut inner = lock(&self.inner);
        inner.last_traffic = Some(now);
        inner.last_traffic_ms = Some(chrono::Utc::now().timestamp_millis());
        let id = session_id.trim();
        if !id.is_empty() {
            bounded_upsert(
                &mut inner.relay,
                id,
                RelaySeen {
                    first: now,
                    last: now,
                },
                |seen| seen.last = now,
                |seen| seen.last,
            );
        }
    }

    /// The plugin side: one OpenCode plugin event naming `session_id`.
    pub fn note_plugin(&self, session_id: &str, now: Instant) {
        let id = session_id.trim();
        if id.is_empty() {
            return;
        }
        bounded_upsert(
            &mut lock(&self.inner).plugin,
            id,
            now,
            |seen| *seen = now,
            |seen| *seen,
        );
    }

    fn prune(inner: &mut Inner, now: Instant) {
        let live = |t: &Instant| now.saturating_duration_since(*t) <= WINDOW;
        // An active session stays: the window rolls on its last sighting, so a session that runs
        // across the 24-hour mark is neither dropped nor reported a second time (Plan D-9, D-10).
        inner.relay.retain(|_, seen| live(&seen.last));
        inner.plugin.retain(|_, t| live(t));
        let relay = &inner.relay;
        inner.reported.retain(|id| relay.contains_key(id));
        if inner.last_traffic.is_some_and(|t| !live(&t)) {
            inner.last_traffic = None;
            inner.last_traffic_ms = None;
        }
    }

    fn suspected_in(inner: &Inner, now: Instant) -> Vec<String> {
        let mut out: Vec<String> = inner
            .relay
            .iter()
            .filter(|(id, seen)| {
                now.saturating_duration_since(seen.first) >= GRACE
                    && !inner.plugin.contains_key(*id)
            })
            .map(|(id, _)| id.clone())
            .collect();
        out.sort();
        out
    }

    /// Suspected sessions not reported yet; each is marked reported, so it is returned once.
    pub fn take_new_suspects(&self, now: Instant) -> Vec<String> {
        let mut inner = lock(&self.inner);
        Self::prune(&mut inner, now);
        let fresh: Vec<String> = Self::suspected_in(&inner, now)
            .into_iter()
            .filter(|id| !inner.reported.contains(id))
            .collect();
        inner.reported.extend(fresh.iter().cloned());
        fresh
    }

    /// Return sessions [`Self::take_new_suspects`] handed out whose report could not be delivered,
    /// so the next sweep hands them out again. A session that has left the window stays gone.
    pub fn requeue(&self, sessions: &[String]) {
        let mut inner = lock(&self.inner);
        for id in sessions {
            inner.reported.remove(id);
        }
    }

    /// The state doctor reads.
    pub fn snapshot(&self, now: Instant) -> WindowSnapshot {
        let mut inner = lock(&self.inner);
        Self::prune(&mut inner, now);
        WindowSnapshot {
            traffic: inner.last_traffic.is_some(),
            last_traffic_ms: inner.last_traffic_ms,
            suspected: Self::suspected_in(&inner, now).len(),
            since_daemon_start: now.saturating_duration_since(self.started) < WINDOW,
        }
    }
}

/// The `tamper_detected` event for one suspected session (Plan D-10): a host fact on
/// `hook_entry`, never healable, deduplicated by the window. The session id rides in `entry_id`,
/// as a hook registration's id does: the event carries no subject.
pub fn bypass_event(session_id: &str) -> crate::cloud::tamper::TamperEvent {
    use crate::cloud::tamper::{TamperEvent, DETECTION_PLUGIN_BYPASS_SUSPECTED};
    TamperEvent::new(
        format!("opencode:session:{session_id}"),
        crate::hooks::bindings::opencode::OpencodeBinding::AGENT_TYPE.to_string(),
        String::new(),
        "plugin_loaded".to_string(),
        DETECTION_PLUGIN_BYPASS_SUSPECTED.to_string(),
    )
    .with_heal("not_healable", 0, "closed")
}

#[cfg(test)]
mod tests {
    use super::*;

    fn at(base: Instant, secs: u64) -> Instant {
        base + Duration::from_secs(secs)
    }

    #[test]
    fn the_user_agent_token_is_the_first_product_only() {
        assert!(is_opencode_user_agent(
            "opencode/1.18.35 ai-sdk/provider-utils/4.0.23 runtime/bun/1.3.14"
        ));
        assert!(is_opencode_user_agent("OpenCode/1.0"));
        assert!(!is_opencode_user_agent("ai-sdk/4 opencode/1.18.35"));
        assert!(!is_opencode_user_agent("cline/3.0"));
        assert!(!is_opencode_user_agent("opencode"));
        assert!(!is_opencode_user_agent(""));
    }

    /// A `--pure` run: the relay sees the session, the plugin never does. Suspected once the
    /// grace has passed, reported exactly once.
    #[test]
    fn a_session_the_plugin_never_reported_is_suspected_once() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        w.note_relay("ses_pure", t0);
        assert!(
            w.take_new_suspects(at(t0, 1)).is_empty(),
            "inside the grace"
        );
        assert_eq!(w.snapshot(at(t0, 1)).suspected, 0);
        assert_eq!(
            w.take_new_suspects(at(t0, 11)),
            vec!["ses_pure".to_string()]
        );
        assert!(w.take_new_suspects(at(t0, 12)).is_empty(), "reported once");
        let snap = w.snapshot(at(t0, 12));
        assert!(snap.traffic);
        assert_eq!(snap.suspected, 1, "still suspected, only not re-reported");
        assert!(snap.since_daemon_start);
    }

    /// A normal run: the plugin's prompt report lands first, or inside the grace.
    #[test]
    fn a_session_the_plugin_reported_is_never_suspected() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        w.note_plugin("ses_a", t0);
        w.note_relay("ses_a", at(t0, 1));
        w.note_relay("ses_b", at(t0, 1));
        w.note_plugin("ses_b", at(t0, 5));
        assert!(w.take_new_suspects(at(t0, 60)).is_empty());
        assert_eq!(w.snapshot(at(t0, 60)).suspected, 0);
    }

    /// Plan D-9: the relay side does not depend on any live session — a pure run beside an
    /// unrelated live plugin session is still suspected.
    #[test]
    fn an_unrelated_plugin_session_does_not_hide_a_pure_run() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        w.note_plugin("ses_live", t0);
        w.note_relay("ses_pure", t0);
        assert_eq!(
            w.take_new_suspects(at(t0, 30)),
            vec!["ses_pure".to_string()]
        );
    }

    #[test]
    fn traffic_with_a_blank_session_is_traffic_but_no_session() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        assert!(!w.snapshot(t0).traffic);
        w.note_relay("  ", t0);
        let snap = w.snapshot(at(t0, 60));
        assert!(snap.traffic);
        assert_eq!(snap.suspected, 0);
    }

    #[test]
    fn entries_age_out_of_the_window() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        w.note_relay("ses_old", t0);
        let later = t0 + WINDOW + Duration::from_secs(1);
        let snap = w.snapshot(later);
        assert!(!snap.traffic);
        assert_eq!(snap.suspected, 0);
        assert!(!snap.since_daemon_start);
    }

    /// Plan D-9/D-10: the window rolls on the last sighting. A `--pure` session still active past
    /// the 24-hour mark keeps `bypass_suspected` and is never reported a second time.
    #[test]
    fn an_active_session_survives_the_window_and_is_reported_once() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        w.note_relay("ses_long", t0);
        assert_eq!(
            w.take_new_suspects(at(t0, 11)),
            vec!["ses_long".to_string()]
        );
        let near_end = t0 + WINDOW - Duration::from_secs(60);
        w.note_relay("ses_long", near_end);
        let past = t0 + WINDOW + Duration::from_secs(60);
        assert!(w.take_new_suspects(past).is_empty(), "never twice");
        let snap = w.snapshot(past);
        assert!(snap.traffic);
        assert_eq!(snap.suspected, 1, "still suspected past the 24h mark");
    }

    /// A report that could not be delivered is handed out again, once.
    #[test]
    fn a_requeued_suspect_is_handed_out_again() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        w.note_relay("ses_pure", t0);
        let got = w.take_new_suspects(at(t0, 11));
        assert_eq!(got, vec!["ses_pure".to_string()]);
        w.requeue(&got);
        assert_eq!(w.take_new_suspects(at(t0, 16)), got);
        assert!(w.take_new_suspects(at(t0, 21)).is_empty());
    }

    #[test]
    fn each_side_is_bounded() {
        let t0 = Instant::now();
        let w = OpencodeSessionWindow::new(t0);
        for i in 0..(MAX_IDS + 10) {
            w.note_relay(&format!("ses_{i}"), at(t0, i as u64 % 3));
        }
        assert!(lock(&w.inner).relay.len() <= MAX_IDS);
    }

    #[test]
    fn the_bypass_event_is_a_high_unhealable_hook_entry_fact() {
        let e = bypass_event("ses_x");
        assert_eq!(e.tamper.agent_type, "opencode");
        assert_eq!(
            e.tamper.component,
            crate::cloud::tamper::COMPONENT_HOOK_ENTRY
        );
        assert_eq!(e.tamper.detection_method, "plugin_bypass_suspected");
        assert_eq!(e.ocsf.severity_id, 4);
        assert_eq!(e.tamper.heal.outcome, "not_healable");
        assert_eq!(e.tamper.entry_id, "opencode:session:ses_x");
    }

    #[test]
    fn the_snapshot_json_names_its_fields() {
        let snap = WindowSnapshot {
            traffic: true,
            last_traffic_ms: Some(7),
            suspected: 2,
            since_daemon_start: true,
        };
        assert_eq!(
            snap.to_json(),
            serde_json::json!({
                "traffic": true,
                "last_traffic_ms": 7,
                "bypass_suspected": true,
                "suspected_sessions": 2,
                "since_daemon_start": true,
            })
        );
    }
}