fix: stagger restored agent startups (#4487)

* fix: stagger restored agent startups

refs #4102

* fix: report startup delay changes requiring restart

refs #4102

1 files changed, 36 insertions, 0 deletions

diff --git a/src/app/mod.rs b/src/app/mod.rs
index 757a7f66..7ff3040b 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -136,6 +136,8 @@ pub struct App {
     pub(crate) loaded_host_cursor: crate::config::HostCursorModeConfig,
     pub(crate) agent_metadata_deadline: Option<Instant>,
     pub(crate) pending_agent_resume_deadline: Option<Instant>,
+    startup_per_agent_delay: Duration,
+    next_agent_resume_at: Option<Instant>,
     pub(crate) session_save_deadline: Option<Instant>,
     pub(crate) session_save_thread: Option<std::thread::JoinHandle<()>>,
     session_writer: Arc<std::sync::Mutex<crate::persist::SessionWriter>>,
@@ -600,6 +602,10 @@ impl App {
             loaded_host_cursor: config.ui.host_cursor,
             agent_metadata_deadline: None,
             pending_agent_resume_deadline: None,
+            startup_per_agent_delay: Duration::from_millis(
+                config.session.startup_per_agent_delay_ms.into(),
+            ),
+            next_agent_resume_at: None,
             session_save_deadline: None,
             session_save_thread: None,
             session_writer,
@@ -857,6 +863,16 @@ impl App {
             }
         }
 
+        if !invalid_section("session")
+            && Duration::from_millis(config.session.startup_per_agent_delay_ms.into())
+                != self.startup_per_agent_delay
+        {
+            diagnostics.push(
+                "session.startup_per_agent_delay_ms changes require restarting Herdr; kept current setting"
+                    .into(),
+            );
+        }
+
         let graphics_config_valid = !invalid_section("terminal")
             && (config.terminal.kitty_graphics.is_some() || !invalid_section("experimental"));
         if graphics_config_valid
@@ -1761,6 +1777,26 @@ mod tests {
     }
 
     #[test]
+    fn reload_config_reports_startup_delay_requires_restart() {
+        let mut app = test_app();
+        let mut config = Config::default();
+        let report = app.apply_live_config(&config, &[], &[], false);
+        assert_eq!(report.status, crate::config::ConfigReloadStatus::Applied);
+
+        config.session.startup_per_agent_delay_ms = 250;
+        let report = app.apply_live_config(&config, &[], &[], false);
+        assert_eq!(report.status, crate::config::ConfigReloadStatus::Partial);
+        assert_eq!(app.startup_per_agent_delay, Duration::from_millis(100));
+        assert_eq!(report.diagnostics, vec![
+            "session.startup_per_agent_delay_ms changes require restarting Herdr; kept current setting"
+        ]);
+
+        let report = app.apply_live_config(&config, &[], &["session".into()], false);
+        assert!(report.diagnostics.is_empty());
+        assert_eq!(app.startup_per_agent_delay, Duration::from_millis(100));
+    }
+
+    #[test]
     fn reload_config_requests_client_reload_for_key_only_change() {
         let _guard = config_env_lock().lock().unwrap();
         let path = temp_config_path("reload-config-key-only");