Add federation worker and canonical handoffs

internal/store/store.go

@@ -145,6 +145,7 @@ func (s *Store) apply(e domain.Event) error {
 	case "TaskReleased":
 		t.State = domain.StateQueued
 		t.Lease = nil
+		t.HandoffRef, _ = p["handoff_ref"].(string)
 	case "TaskCompleted":
 		t.State = domain.StateCompleted
 		t.Lease = nil
@@ -398,7 +399,11 @@ func (s *Store) Lease(id, harness string, ttl time.Duration) (domain.Event, erro
 	if t.State != domain.StateQueued {
 		return domain.Event{}, domain.ErrConflict
 	}
-	p, _ := json.Marshal(map[string]any{"harness_id": harness, "ttl": ttl.Seconds(), "until_ns": time.Now().Add(ttl).UnixNano(), "expected_version": t.Version})
+	payload := map[string]any{"harness_id": harness, "ttl": ttl.Seconds(), "until_ns": time.Now().Add(ttl).UnixNano(), "expected_version": t.Version}
+	if t.HandoffRef != "" {
+		payload["handoff_ref"] = t.HandoffRef
+	}
+	p, _ := json.Marshal(payload)
 	e := domain.Event{ID: domain.NewID(), Type: "TaskLeased", TaskID: id, Version: t.Version + 1, Payload: p, Surface: string(authz.System)}
 	return e, s.Append(e)
 }

internal/store/store_test.go

@@ -17,6 +17,40 @@ func created(id string) domain.Event {
 	return domain.Event{ID: id, Type: "TaskCreated", TaskID: "task-1", Version: 1, Payload: b, Surface: string(authz.System)}
 }
 
+func TestLeaseCarriesReleasedHandoffRef(t *testing.T) {
+	s, err := Open(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	b := []byte(`{"source":"s","external_id":"x","project":"p"}`)
+	if err := s.Append(domain.Event{ID: "create", Type: "TaskCreated", TaskID: "t", Version: 1, Payload: b, Surface: string(authz.System)}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.Lease("t", "h", time.Minute); err != nil {
+		t.Fatal(err)
+	}
+	ref, err := s.PutArtifact([]byte("handoff"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	task, _ := s.Task("t")
+	p, _ := json.Marshal(map[string]string{"handoff_ref": ref, "anchor_sha": "0123456789012345678901234567890123456789"})
+	if err := s.Append(domain.Event{ID: "release", Type: "TaskReleased", TaskID: "t", Version: task.Version + 1, Payload: p, Surface: string(authz.System)}); err != nil {
+		t.Fatal(err)
+	}
+	e, err := s.Lease("t", "h", time.Minute)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var got map[string]any
+	if err := json.Unmarshal(e.Payload, &got); err != nil {
+		t.Fatal(err)
+	}
+	if got["handoff_ref"] != ref {
+		t.Fatalf("handoff_ref=%v want %s", got["handoff_ref"], ref)
+	}
+}
+
 func TestAppendReplayAndDeduplicate(t *testing.T) {
 	dir := t.TempDir()
 	s, err := Open(dir)