feat(handoff): prepare the idle handoff after four minutes

crates/code_assistant_core/src/session/idle_handoff.rs

@@ -1,5 +1,5 @@
 //! Prepared handoffs (see `docs/handoff.md`): when a long session goes
-//! idle, a timer gives the user two minutes; if they stay away, the core has
+//! idle, a timer gives the user four minutes; if they stay away, the core has
 //! the agent write a handoff prompt while the prompt cache is still warm and
 //! offers it in the composer as `/new <prompt>`.
 //!
@@ -18,7 +18,7 @@ use std::time::{Duration, Instant};
 use tracing::warn;
 
 /// How long a session must stay without user activity.
-pub const IDLE_DELAY: Duration = Duration::from_secs(120);
+pub const IDLE_DELAY: Duration = Duration::from_secs(240);
 
 /// Configuration persisted at `<config_dir>/handoff.json`.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]

crates/ui_gpui/src/main_screen/mod.rs

@@ -1265,7 +1265,7 @@ impl MainScreen {
     }
 
     /// Tell the core the user is typing in the session (throttled); it
-    /// postpones preparing a handoff (two minutes idle).
+    /// postpones preparing a handoff (four minutes idle).
     fn report_user_activity(&mut self, session_id: String, cx: &mut Context<Self>) {
         if !self
             .activity_reports

crates/ui_gpui/src/settings_screen/general_section.rs

@@ -230,7 +230,7 @@ impl Render for GeneralSection {
                             .text_color(cx.theme().muted_foreground)
                             .child(
                                 "When a session whose last request had at least this many \
-                                 input tokens stays idle for two minutes, the agent prepares \
+                                 input tokens stays idle for four minutes, the agent prepares \
                                  a /new prompt for a follow-up session while the prompt cache \
                                  is still warm. 0 turns this off.",
                             ),

docs/handoff.md

@@ -104,7 +104,7 @@ so it never starts with consecutive user messages.
 ## Prepared handoff (idle)
 
 - **Arming**: when a run ends in which the agent answered in the session,
-  the core arms a per-session deadline of 2 minutes. A `/new` that only
+  the core arms a per-session deadline of 4 minutes. A `/new` that only
   opened an empty context or moved to a new session does not arm it.
 - **User activity**: frontends report typing in the viewed session via
   `SessionService::note_user_activity(session_id)`, throttled per session