session persistence: SIGHUP, bus disconnect, checkpointing, chat log restore

- Add SIGHUP to signal handler for non-systemd session teardown
- Detect D-Bus session bus disconnection via conn.Context().Done()
- Checkpoint individual sessions to disk on every idle transition
- Remove checkpoint files when sessions are killed
- Rebuild visible chat log from last 8 messages on restore

main.go

@@ -197,6 +197,7 @@ func (m *SessionManager) CreateSession(cwd, backendName, modelName, agentName st
 			// Send notification when a turn completes
 			if current == "idle" {
 				m.sendNotification("Ollie", "Session "+sess.id+" finished")
+				m.persistSession(sess.id)
 			}
 		}
 	}()
@@ -234,6 +235,7 @@ func (m *SessionManager) KillSession(sessionID string) (bool, *dbus.Error) {
 	sess.core.Interrupt(agent.ErrInterrupted)
 	sess.core.Close()
 	sess.cancel()
+	m.removePersistedSession(sessionID)
 
 	m.conn.Emit(busPath, busIface+".SessionKilled", sessionID)
 	return true, nil
@@ -532,6 +534,81 @@ func activeSessionsDir() string {
 	return filepath.Join(paths.DataDir(), "active-sessions")
 }
 
+// persistSession saves a single session to the active-sessions directory.
+// Called on every idle transition for crash resilience.
+func (m *SessionManager) persistSession(id string) {
+	if strings.HasSuffix(id, "-copilot") {
+		return
+	}
+	dir := activeSessionsDir()
+	os.MkdirAll(dir, 0700)
+
+	m.mu.RLock()
+	sess, ok := m.sessions[id]
+	m.mu.RUnlock()
+	if !ok {
+		return
+	}
+
+	path := filepath.Join(dir, id+".json")
+	if err := sess.core.SaveSession(path); err != nil {
+		fmt.Fprintf(os.Stderr, "checkpoint session %s: %v\n", id, err)
+	}
+}
+
+// removePersistedSession deletes the checkpoint file for a killed session.
+func (m *SessionManager) removePersistedSession(id string) {
+	path := filepath.Join(activeSessionsDir(), id+".json")
+	os.Remove(path)
+}
+
+// rebuildChatLog reconstructs a human-readable chat log from the tail of the
+// persisted message list. This gives restored sessions visible history.
+func rebuildChatLog(messages []backend.Message) []byte {
+	// Show up to the last hotTailSize messages (matches the verbatim context window).
+	const tailSize = 8
+	start := 0
+	if len(messages) > tailSize {
+		start = len(messages) - tailSize
+	}
+	tail := messages[start:]
+
+	var buf strings.Builder
+	if start > 0 {
+		buf.WriteString(fmt.Sprintf("[info] session restored (%d earlier messages compacted)\n\n", start))
+	}
+	for _, msg := range tail {
+		switch msg.Role {
+		case "system":
+			continue // don't show system messages in chat log
+		case "user":
+			buf.WriteString("[user]\n" + msg.Content + "\n\n")
+		case "assistant":
+			if msg.Reasoning != "" {
+				buf.WriteString("[reasoning]\n" + msg.Reasoning + "\n\n")
+			}
+			if msg.Content != "" {
+				buf.WriteString("[assistant]\n" + msg.Content + "\n\n")
+			}
+			for _, tc := range msg.ToolCalls {
+				buf.WriteString("[call:" + tc.Name + "]\n" + string(tc.Arguments) + "\n\n")
+			}
+		case "tool":
+			name := "result"
+			if msg.ToolCallID != "" {
+				name = msg.ToolCallID
+			}
+			// Truncate long tool results in the log
+			content := msg.Content
+			if len(content) > 2000 {
+				content = content[:2000] + "\n... (truncated)"
+			}
+			buf.WriteString("[tool:" + name + "]\n" + content + "\n\n")
+		}
+	}
+	return []byte(buf.String())
+}
+
 // saveAllSessions persists every active session to disk so they can be restored on restart.
 func (m *SessionManager) saveAllSessions() {
 	dir := activeSessionsDir()
@@ -668,6 +745,7 @@ func (m *SessionManager) restoreSession(ps *agent.PersistedSession) error {
 		cancel: cancel,
 		id:     sessID,
 		agent:  agentName,
+		log:    rebuildChatLog(ps.Messages),
 	}
 
 	// Subscribe to events for the chat log + signal dispatch
@@ -732,6 +810,7 @@ func (m *SessionManager) restoreSession(ps *agent.PersistedSession) error {
 
 			if current == "idle" {
 				m.sendNotification("Ollie", "Session "+sess.id+" finished")
+				m.persistSession(sess.id)
 			}
 		}
 	}()
@@ -1110,8 +1189,13 @@ func main() {
 
 	// Wait for signal
 	sigCh := make(chan os.Signal, 1)
-	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
-	<-sigCh
+	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
+
+	// Shutdown on signal or D-Bus disconnection (session bus gone).
+	select {
+	case <-sigCh:
+	case <-conn.Context().Done():
+	}
 
 	fmt.Println("ollie-dbus daemon shutting down")
 	mgr.Shutdown()