Order the session list by when each agent was turned on

A running session no longer moves: the ones with a process come first,
oldest start first, so starting one appends it to the bottom of that
group and nothing it goes on to do -- beginning a turn, finishing one,
asking a question -- can shift it. Sorting by activity with the
awaiting-answer ones floated to the top is what this replaces; the
status word and its colour already say which session wants something
without the row having to move to say it. Stopped sessions are a group
below, most recently active first.

The order is the server's: `SessionConfig::started` is written each time
a process is started for a session and reported as `started`, so it is
the same on every device and survives a backend restart -- which adopts
processes rather than starting them, and so could not work the times out
for itself. Applied on the phone, because presentation order is a
display decision.

`LiveSession::info` takes the session's config entry rather than a
parameter per field read from it, which is what `AutoResumeView` existed
to bundle; that goes.

Verified on the emulator against the sandbox: three echo sessions kept
their order while the newest-active one was messaged; a stopped and
restarted session moved below one started after it; a stopped session
dropped below every running one; and after a backend restart the
recorded times came back unchanged.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/src/session/mod.rs

@@ -139,29 +139,6 @@ pub enum NotificationKind {
     Finished,
 }
 
-/// What a session's auto-resume setting looks like from outside: on or off,
-/// what it would say, and when it next intends to check.
-///
-/// One struct rather than three parameters on [`LiveSession::info`], and read
-/// from the config rather than from the launch snapshot beside it, for the
-/// reason `cwd` is: all three change under a running session.
-#[derive(Debug, Clone)]
-pub struct AutoResumeView {
-    pub on: bool,
-    pub message: String,
-    pub at: Option<f64>,
-}
-
-impl AutoResumeView {
-    fn of(meta: &SessionConfig) -> Self {
-        Self {
-            on: meta.auto_resume,
-            message: resume_message(meta),
-            at: meta.resume.map(|scheduled| scheduled.at),
-        }
-    }
-}
-
 /// A session with a message owed to it once its account has quota again --
 /// see [`SessionManager::owed_resumes`].
 ///
@@ -272,6 +249,10 @@ pub struct SessionInfo {
     pub status: SessionStatus,
     pub last_activity: f64,
     pub created: f64,
+    /// Epoch seconds this session's agent was last turned on, which the
+    /// session list orders the running ones by -- see
+    /// [`SessionConfig::started`], whose fallback this resolves.
+    pub started: f64,
     /// The provider's latest measured number of live background tasks.
     /// Absent until it reports one; absence is not a measured zero.
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -566,11 +547,12 @@ impl LiveSession {
         Ok((name, path))
     }
 
-    /// `machine_name` and `cwd` are passed in rather than read from the
-    /// snapshot this session launched with: only the manager holds the
-    /// config, and both can change under a running session. Passed rather
-    /// than mirrored into `Shared`, so there is one answer, read where the
-    /// row is built.
+    /// `machine_name` and the session's own config entry are passed in
+    /// rather than read from the snapshot this session launched with: only
+    /// the manager holds the config, and a setting, a working directory or
+    /// the time of the latest start can all change under a running session.
+    /// Passed rather than mirrored into `Shared`, so there is one answer,
+    /// read where the row is built.
     ///
     /// `kind` rather than the facts derived from it, or every caller
     /// derives each one separately. `None` where the provider has been
@@ -579,11 +561,9 @@ impl LiveSession {
     fn info(
         &self,
         machine_name: &str,
-        cwd: Option<&Path>,
-        effort: Option<&str>,
+        current: &SessionConfig,
         imported: bool,
         kind: Option<DriverKind>,
-        resume: AutoResumeView,
     ) -> SessionInfo {
         SessionInfo {
             id: self.meta.id.clone(),
@@ -596,22 +576,23 @@ impl LiveSession {
             // From the config rather than from `shared`, like the cwd beside
             // it: neither can change under a running process, so there is no
             // live value for one to disagree with.
-            effort: effort.map(str::to_string),
+            effort: current.effort.clone(),
             takes_effort: kind.is_some_and(DriverKind::takes_effort),
             context_tokens: *self.shared.context_tokens.lock().unwrap(),
             notify: *self.shared.notify.lock().unwrap(),
-            auto_resume: resume.on,
-            auto_resume_message: resume.message,
-            resume_at: resume.at,
+            auto_resume: current.auto_resume,
+            auto_resume_message: resume_message(current),
+            resume_at: current.resume.map(|scheduled| scheduled.at),
             max_image_edge: kind.and_then(DriverKind::max_image_edge),
             usage_provider: kind.and_then(DriverKind::usage_provider),
             imported,
             keeps_own_transcript: kind.is_some_and(DriverKind::keeps_own_transcript),
             own_transcript_name: kind.and_then(DriverKind::own_transcript_name),
-            cwd: cwd.map(Path::to_path_buf),
+            cwd: current.cwd.clone(),
             status: *self.shared.status.lock().unwrap(),
             last_activity: *self.shared.last_activity.lock().unwrap(),
             created: self.meta.created,
+            started: current.started_at(),
             background_tasks: self.driver().and_then(|driver| driver.background_tasks()),
             subagents: subagent::count(self.dir()),
         }
@@ -1107,11 +1088,9 @@ impl SessionManager {
             .map(|meta| match inner.live.get(&meta.id) {
                 Some(session) => session.info(
                     label_of(&inner.config, &meta.machine),
-                    meta.cwd.as_deref(),
-                    meta.effort.as_deref(),
+                    meta,
                     import::read_cursor(&self.data_dir.join(&meta.id)).is_some(),
                     kind_of(&inner.config, &meta.machine, &meta.provider),
-                    AutoResumeView::of(meta),
                 ),
                 None => SessionInfo {
                     id: meta.id.clone(),
@@ -1145,6 +1124,7 @@ impl SessionManager {
                     status: status_of_unlaunched(&self.data_dir.join(&meta.id)),
                     last_activity: meta.created,
                     created: meta.created,
+                    started: meta.started_at(),
                     background_tasks: None,
                     subagents: subagent::count(&self.data_dir.join(&meta.id)),
                 },
@@ -1223,6 +1203,7 @@ impl SessionManager {
             })?
             .clone();
         let id = unique_id(&inner.config);
+        let created = now();
         let title = spec
             .title
             .filter(|title| !title.trim().is_empty())
@@ -1268,7 +1249,10 @@ impl SessionManager {
             // whichever server is running when the time comes knows what to
             // do with it -- see `SessionConfig::throwaway`.
             throwaway: self.spawn_throwaway,
-            created: now(),
+            created,
+            // The spawn starts a process, so this session is turned on from
+            // the moment it exists.
+            started: Some(created),
         };
 
         let session = launch(
@@ -1293,11 +1277,9 @@ impl SessionManager {
         // of the directory a moment later.
         let info = session.info(
             &machine.name,
-            session.meta.cwd.as_deref(),
-            session.meta.effort.as_deref(),
+            &session.meta,
             import::read_cursor(&self.data_dir.join(&id)).is_some(),
             Some(provider.kind),
-            AutoResumeView::of(&session.meta),
         );
         inner.live.insert(id, session);
         Ok(info)
@@ -1931,6 +1913,18 @@ impl SessionManager {
                 inner.live.insert(id.to_string(), session);
             }
         }
+        // Turned on now, so it takes its place at the bottom of the running
+        // group -- see `SessionConfig::started`. Best effort: a config that
+        // cannot be written is not a reason to fail a start that has already
+        // happened, and the cost is one row in the wrong place.
+        let mut candidate = inner.config.clone();
+        if let Some(meta) = candidate.sessions.iter_mut().find(|meta| meta.id == id) {
+            meta.started = Some(now());
+            match candidate.save(&self.config_path) {
+                Ok(()) => inner.config = candidate,
+                Err(err) => tracing::warn!("couldn't record that session {id} started: {err:#}"),
+            }
+        }
         // Nothing is announced from here. A driver that starts a process
         // reports the session idle itself, in order with everything else it
         // says about that process. Saying it here too would be a second
@@ -3219,20 +3213,7 @@ mod tests {
         // open to look one up on.
         assert_eq!(
             first.title,
-            session
-                .info(
-                    "m",
-                    None,
-                    None,
-                    false,
-                    None,
-                    AutoResumeView {
-                        on: false,
-                        message: DEFAULT_RESUME_MESSAGE.to_string(),
-                        at: None,
-                    },
-                )
-                .title
+            session.info("m", &session.meta, false, None).title
         );
 
         manager.set_session_notify(&info.id, false).expect("off");
@@ -4278,6 +4259,67 @@ mod tests {
         .await;
     }
 
+    /// The session list keeps the running sessions in the order their agents
+    /// were turned on, so what that order is made of has to outlive both the
+    /// process and the backend: a session started again belongs at the bottom
+    /// of the group, and a restart adopts processes rather than starting them,
+    /// so nothing in the new run could work the time out for itself.
+    #[tokio::test]
+    async fn starting_a_session_again_records_when_it_was_turned_on() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let config_path = dir.path().join("config.ron");
+        let data_dir = dir.path().join("sessions");
+        seed_echo_only(&config_path);
+        let manager = SessionManager::new(
+            config_path.clone(),
+            data_dir.clone(),
+            data_dir.join("models"),
+        )
+        .expect("manager");
+        let info = manager.spawn_session(echo_spec()).expect("spawn");
+        let spawned = info.started;
+        assert!(
+            (spawned - info.created).abs() < 1.0,
+            "a spawned session was turned on at {spawned} rather than when it was created",
+        );
+
+        let session = manager.session(&info.id).expect("live session");
+        let mut rx = session.subscribe();
+        let _ = session.sink.send(Event::Status {
+            state: SessionStatus::Exited,
+        });
+        collect_until(&mut rx, |event| {
+            matches!(
+                event,
+                Event::Status {
+                    state: SessionStatus::Exited
+                }
+            )
+        })
+        .await;
+        // Otherwise the two starts can land in the same instant and the test
+        // cannot tell a recorded time from a kept one.
+        tokio::time::sleep(Duration::from_millis(20)).await;
+        manager.start_session(&info.id).expect("start again");
+        collect_until(&mut rx, is_idle).await;
+
+        let restarted = manager.sessions()[0].started;
+        assert!(
+            restarted > spawned,
+            "starting the session again left it reporting {restarted}, the {spawned} of the \
+             process that had already ended",
+        );
+        drop(manager);
+
+        let manager = SessionManager::new(config_path, data_dir.clone(), data_dir.join("models"))
+            .expect("manager restart");
+        assert_eq!(
+            manager.sessions()[0].started,
+            restarted,
+            "the backend restart lost when this session's agent was turned on",
+        );
+    }
+
     /// Stopping and starting a session is about its *process*, and the two
     /// refusals are what keeps starting one from becoming a second one on the
     /// same conversation. Echo has no process, which makes it the right