Start a new task from a closed task

internal/agents/fork.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"math"
 	"strings"
 	"time"
 
@@ -19,6 +20,13 @@ func (m *Manager) Fork(ctx context.Context, src api.Task, project api.Project, n
 	return t, err
 }
 
+func forkOrigin(t api.Task, from string) string {
+	if t.ForkedAt == nil {
+		return "continued from " + from
+	}
+	return fmt.Sprintf("forked from %s at snapshot %d", from, *t.ForkedAt)
+}
+
 func forkTitle(src api.Task, n int) string {
 	return fmt.Sprintf("%s (fork of #%d)", src.Title, n)
 }
@@ -172,7 +180,7 @@ func (m *Manager) fork(ctx context.Context, src api.Task, project api.Project, n
 		return api.Task{}, "", fmt.Errorf("%w: snapshot %d of task %s has no recorded agent message at or before it to fork the conversation from", ErrConflict, n, src.Id)
 	}
 
-	t, err := m.createTask(ctx, project, api.Task{
+	return m.forkSession(ctx, project, api.Task{
 		Title:         title,
 		MergeTitle:    src.MergeTitle,
 		CreatedBy:     creator.Login,
@@ -181,7 +189,61 @@ func (m *Manager) fork(ctx context.Context, src api.Task, project api.Project, n
 		ForkedAt:      &n,
 		WorkflowStage: src.WorkflowStage,
 		ParentTaskId:  src.ParentTaskId,
-	}, snap.CommitSha, creator.Login)
+	}, snap.CommitSha, creator, srcSess, at)
+}
+
+func (m *Manager) Continue(ctx context.Context, srcSess api.AgentSession, src api.Task, project api.Project, creator api.User, text, model, sendID, client string, images ...string) (api.Task, error) {
+	if creator.GitName == "" || creator.GitEmail == "" {
+		return api.Task{}, ErrNoGitIdentity
+	}
+	if src.Status == api.TaskStatusActive {
+		return api.Task{}, fmt.Errorf("%w: task %s is still active", ErrConflict, src.Id)
+	}
+	if srcSess.Role != api.Implementer {
+		return api.Task{}, fmt.Errorf("%w: session %s is a %s, not a task's agent", ErrConflict, srcSess.Id, srcSess.Role)
+	}
+	if srcSess.Vendor == api.Antigravity {
+		return api.Task{}, fmt.Errorf("%w: session %s ran on Antigravity, and agy can't fork a conversation", ErrConflict, srcSess.Id)
+	}
+
+	unlock := m.lockDelivery("continue:" + srcSess.Id)
+	defer unlock()
+	ctx = context.WithoutCancel(ctx)
+	prior, sent, err := m.priorSend(ctx, sendID)
+	if err != nil {
+		return api.Task{}, err
+	}
+	if sent {
+		return m.store.GetTask(ctx, prior.TaskId)
+	}
+
+	events, err := m.store.TaskEvents(ctx, src.Id, 0, -1)
+	if err != nil {
+		return api.Task{}, err
+	}
+	at := forkPoint(events, srcSess.Id, math.MaxInt64)
+	if at == "" {
+		return api.Task{}, fmt.Errorf("%w: session %s has no recorded agent message to continue the conversation from", ErrConflict, srcSess.Id)
+	}
+
+	t, sessionID, err := m.forkSession(ctx, project, api.Task{
+		Title:      src.Title + " (continued)",
+		MergeTitle: src.MergeTitle,
+		CreatedBy:  creator.Login,
+		ForkedFrom: &src.Id,
+	}, project.DefaultBranch, creator, srcSess, at)
+	if err != nil {
+		return api.Task{}, err
+	}
+	_, _, err = m.Message(ctx, sessionID, creator.Login, text, model, sendID, client, images...)
+	if err != nil {
+		return api.Task{}, fmt.Errorf("task %s created, but its agent did not start: %w", t.Id, err)
+	}
+	return t, nil
+}
+
+func (m *Manager) forkSession(ctx context.Context, project api.Project, task api.Task, base string, creator api.User, srcSess api.AgentSession, at string) (api.Task, string, error) {
+	t, err := m.createTask(ctx, project, task, base, creator.Login)
 	if err != nil {
 		return api.Task{}, "", err
 	}