Add title regeneration and improve thread titles

crates/client/src/lib.rs

@@ -1220,6 +1220,7 @@ mod tests {
                         request_id: None,
                         topic: Topic::Index,
                         event: ServerEvent::IndexSnapshot(IndexSnapshot {
+                            title_generating: Default::default(),
                             activity: Default::default(),
                             sessions: Vec::new(),
                             projects: Vec::new(),

crates/core/src/settings.rs

@@ -675,8 +675,8 @@ impl OrchestrateSettings {
 }
 
 /// Provider and model used for the isolated, background request that names a
-/// newly-started thread. Reasoning effort is intentionally fixed to `low` by
-/// the runtime: title generation is a small, latency-sensitive task.
+/// thread, initially or on request. Reasoning effort is intentionally fixed to
+/// `low` by the runtime: title generation is a small, latency-sensitive task.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct TitleGenerationSettings {
     #[serde(default = "default_title_provider")]

crates/protocol/src/command.rs

@@ -239,6 +239,9 @@ pub enum Command {
         session_id: String,
         title: String,
     },
+    RegenerateSessionTitle {
+        session_id: String,
+    },
     ForkThread {
         id: String,
     },
@@ -416,6 +419,7 @@ impl Command {
             | Self::ArchiveSession { session_id, .. }
             | Self::UnarchiveSession { session_id, .. }
             | Self::RenameSession { session_id, .. }
+            | Self::RegenerateSessionTitle { session_id }
             | Self::DeleteSession { session_id, .. }
             | Self::MergeWorktree { session_id, .. }
             | Self::MarkSessionUnread { session_id, .. }

crates/protocol/src/event.rs

@@ -314,6 +314,9 @@ pub struct IndexSnapshot {
     /// Working, approval, user-input and background-only flags for sidebar rows.
     #[serde(default)]
     pub activity: HashMap<String, (bool, bool, bool, bool)>,
+    /// Background title requests, including threads with no live provider.
+    #[serde(default)]
+    pub title_generating: HashSet<String>,
     pub sessions: Vec<SessionMeta>,
     pub projects: Vec<Project>,
 }
@@ -415,6 +418,8 @@ pub enum RuntimeError {
     PersistEvent { error: String },
     WorktreeAdd { error: String },
     PersistSession { error: String },
+    TitleGenerationFailed,
+    TitleGenerationEmpty,
     ProcessGone,
     SteerUnsupported { agent: String },
     DirtyTree,

crates/runtime/src/app/command_validation.rs

@@ -106,6 +106,7 @@ impl AppState {
                 | Command::ArchiveSession { .. }
                 | Command::UnarchiveSession { .. }
                 | Command::RenameSession { .. }
+                | Command::RegenerateSessionTitle { .. }
                 | Command::DeleteSession { .. }
                 | Command::MarkSessionUnread { .. }
                 | Command::ForkThread { .. }