Keep latest session selection tied to real session recency

The next repo-local sweep target was ROADMAP #72: the `latest`
managed-session alias could depend on filesystem mtime before the
session's own persisted recency markers, which made the selection
path vulnerable to coarse or misleading file timestamps. The fix
promotes `updated_at_ms` into the summary/order path, keeps CLI
wrappers in sync, and locks the mtime-vs-session-recency case with
regression coverage.

Constraint: Preserve existing managed-session storage layout while changing only the ordering signal
Rejected: Keep sorting by filesystem mtime and just sleep longer in tests | hides the semantic ordering bug instead of fixing it
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Any future managed-session ordering change must keep runtime and CLI summary structs aligned on the same recency fields
Tested: cargo fmt --all --check; cargo clippy --workspace --all-targets -- -D warnings; cargo test --workspace; architect review APPROVE
Not-tested: Cross-filesystem behavior where persisted session JSON cannot be read and fallback ordering uses mtime only

rust/crates/runtime/src/session_control.rs

@@ -144,12 +144,7 @@ impl SessionStore {
         if let Some(legacy_root) = self.legacy_sessions_root() {
             self.collect_sessions_from_dir(&legacy_root, &mut sessions)?;
         }
-        sessions.sort_by(|left, right| {
-            right
-                .modified_epoch_millis
-                .cmp(&left.modified_epoch_millis)
-                .then_with(|| right.id.cmp(&left.id))
-        });
+        sort_managed_sessions(&mut sessions);
         Ok(sessions)
     }
 
@@ -260,6 +255,7 @@ impl SessionStore {
                     ManagedSessionSummary {
                         id: session.session_id,
                         path,
+                        updated_at_ms: session.updated_at_ms,
                         modified_epoch_millis,
                         message_count: session.messages.len(),
                         parent_session_id: session
@@ -279,6 +275,7 @@ impl SessionStore {
                         .unwrap_or("unknown")
                         .to_string(),
                     path,
+                    updated_at_ms: 0,
                     modified_epoch_millis,
                     message_count: 0,
                     parent_session_id: None,
@@ -322,12 +319,23 @@ pub struct SessionHandle {
 pub struct ManagedSessionSummary {
     pub id: String,
     pub path: PathBuf,
+    pub updated_at_ms: u64,
     pub modified_epoch_millis: u128,
     pub message_count: usize,
     pub parent_session_id: Option<String>,
     pub branch_name: Option<String>,
 }
 
+fn sort_managed_sessions(sessions: &mut [ManagedSessionSummary]) {
+    sessions.sort_by(|left, right| {
+        right
+            .updated_at_ms
+            .cmp(&left.updated_at_ms)
+            .then_with(|| right.modified_epoch_millis.cmp(&left.modified_epoch_millis))
+            .then_with(|| right.id.cmp(&left.id))
+    });
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct LoadedManagedSession {
     pub handle: SessionHandle,
@@ -598,6 +606,35 @@ mod tests {
             .expect("session summary should exist")
     }
 
+    #[test]
+    fn latest_session_prefers_semantic_updated_at_over_file_mtime() {
+        let mut sessions = vec![
+            ManagedSessionSummary {
+                id: "older-file-newer-session".to_string(),
+                path: PathBuf::from("/tmp/older"),
+                updated_at_ms: 200,
+                modified_epoch_millis: 100,
+                message_count: 2,
+                parent_session_id: None,
+                branch_name: None,
+            },
+            ManagedSessionSummary {
+                id: "newer-file-older-session".to_string(),
+                path: PathBuf::from("/tmp/newer"),
+                updated_at_ms: 100,
+                modified_epoch_millis: 200,
+                message_count: 1,
+                parent_session_id: None,
+                branch_name: None,
+            },
+        ];
+
+        crate::session_control::sort_managed_sessions(&mut sessions);
+
+        assert_eq!(sessions[0].id, "older-file-newer-session");
+        assert_eq!(sessions[1].id, "newer-file-older-session");
+    }
+
     #[test]
     fn creates_and_lists_managed_sessions() {
         // given

rust/crates/rusty-claude-cli/src/main.rs

@@ -3122,6 +3122,7 @@ struct SessionHandle {
 struct ManagedSessionSummary {
     id: String,
     path: PathBuf,
+    updated_at_ms: u64,
     modified_epoch_millis: u128,
     message_count: usize,
     parent_session_id: Option<String>,
@@ -4711,6 +4712,7 @@ fn list_managed_sessions() -> Result<Vec<ManagedSessionSummary>, Box<dyn std::er
         .map(|session| ManagedSessionSummary {
             id: session.id,
             path: session.path,
+            updated_at_ms: session.updated_at_ms,
             modified_epoch_millis: session.modified_epoch_millis,
             message_count: session.message_count,
             parent_session_id: session.parent_session_id,
@@ -4726,6 +4728,7 @@ fn latest_managed_session() -> Result<ManagedSessionSummary, Box<dyn std::error:
     Ok(ManagedSessionSummary {
         id: session.id,
         path: session.path,
+        updated_at_ms: session.updated_at_ms,
         modified_epoch_millis: session.modified_epoch_millis,
         message_count: session.message_count,
         parent_session_id: session.parent_session_id,