Run the merge queue on a state-driven coordinator

internal/agents/compact.go

@@ -69,9 +69,13 @@ func isContinuation(actor, text string) bool {
 func (m *Manager) continueFromHandoff(sessionID, handoff string) {
 	ctx := context.Background()
 	err := m.handoff(ctx, sessionID, handoff)
-	if err != nil {
-		slog.Error("continue from handoff", "session", sessionID, "err", err)
-		m.advanceSessionMergeClaim(ctx, sessionID)
+	if err == nil {
+		return
+	}
+	slog.Error("continue from handoff", "session", sessionID, "err", err)
+	err = m.store.TransitionSession(ctx, sessionID, api.AgentSessionStateRunning, api.AgentSessionStateIdle, "byre")
+	if err != nil && !errors.Is(err, store.ErrStateChanged) {
+		slog.Error("end failed handoff", "session", sessionID, "err", err)
 	}
 }
 
@@ -95,28 +99,28 @@ func (m *Manager) handoff(ctx context.Context, sessionID, handoff string) error
 		return err
 	}
 
-	discard, err := m.store.GetDiscard(ctx, sess.TaskId)
-	if err != nil {
-		return err
+	if creator.GitName == "" || creator.GitEmail == "" {
+		return ErrNoGitIdentity
 	}
-	if discard.State != store.DiscardNone {
-		m.startDiscard(sess.TaskId)
-		return nil
-	}
-	err = transition(ctx, m.store, sess.Id, api.AgentSessionStateIdle, api.AgentSessionStateCompleted, "byre")
-	if err != nil {
-		return err
-	}
-	m.stopLive(sess.Id)
-
 	task, err := m.store.GetTask(ctx, sess.TaskId)
 	if err != nil {
 		return err
 	}
-	_, err = m.create(ctx, task, creator, sess.Member, handoffPreamble+handoff, model, "byre", "", "", nil)
-	if errors.Is(err, ErrConflict) {
+	next := sessionFor(task, creator, sess.Member, model)
+	next.State = api.AgentSessionStateRunning
+	err = m.store.ReplaceSession(ctx, sess.Id, next, task.ProjectId, "byre")
+	if errors.Is(err, store.ErrStateChanged) {
+		err = transition(ctx, m.store, sess.Id, api.AgentSessionStateRunning, api.AgentSessionStateIdle, "byre")
+		if err != nil {
+			return err
+		}
 		m.startDiscard(task.Id)
 		return nil
 	}
+	if err != nil {
+		return err
+	}
+	m.stopLive(sess.Id)
+	_, err = m.launch(ctx, next, task, "byre", handoffPreamble+handoff, "", "", nil)
 	return err
 }