diff --git a/cmd/orchestra/main.go b/cmd/orchestra/main.go
index 33724a5..62893d6 100644
--- a/cmd/orchestra/main.go
+++ b/cmd/orchestra/main.go
@@ -221,27 +221,21 @@ func main() {
 			}
 			types := map[string]string{"release": "TaskReleased", "complete": "TaskCompleted", "block": "TaskBlocked"}
 			var p map[string]any
-			if r.Body != nil {
-				if json.NewDecoder(r.Body).Decode(&p) != nil {
-					p = map[string]any{}
-				}
-			}
-			if p == nil {
-				p = map[string]any{}
+			if r.Body == nil || json.NewDecoder(r.Body).Decode(&p) != nil || p == nil {
+				http.Error(w, "invalid lifecycle payload", http.StatusBadRequest)
+				return
 			}
 			if action == "release" && p["reason"] == nil && p["handoff_ref"] == nil {
-				p["reason"] = "released_by_api"
+				http.Error(w, "reason or handoff_ref required", http.StatusBadRequest)
+				return
 			}
 			if action == "block" && p["blocker"] == nil {
-				p["blocker"] = "blocked_by_api"
+				http.Error(w, "blocker required", http.StatusBadRequest)
+				return
 			}
 			if action == "complete" && p["report_ref"] == nil {
-				ref, putErr := s.PutArtifact([]byte("completed without an attached report\n"))
-				if putErr != nil {
-					http.Error(w, putErr.Error(), 500)
-					return
-				}
-				p["report_ref"] = ref
+				http.Error(w, "report_ref required", http.StatusBadRequest)
+				return
 			}
 			ePayload, _ := json.Marshal(p)
 			e = domain.Event{ID: id(), Type: types[action], TaskID: taskID, Version: t.Version + 1, Payload: ePayload}
diff --git a/internal/store/store_test.go b/internal/store/store_test.go
index 3e6e777..4ddaf6c 100644
--- a/internal/store/store_test.go
+++ b/internal/store/store_test.go
@@ -72,3 +72,23 @@ func TestArtifactIsContentAddressed(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestLifecycleEventsRequireEvidence(t *testing.T) {
+	cases := []struct {
+		name string
+		typ  string
+		body string
+	}{
+		{"release", "TaskReleased", `{}`},
+		{"complete", "TaskCompleted", `{}`},
+		{"block", "TaskBlocked", `{}`},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			err := domain.ValidateEvent(domain.Event{Type: tc.typ, TaskID: "task-1", Version: 1, Payload: json.RawMessage(tc.body)})
+			if err == nil {
+				t.Fatal("expected lifecycle evidence validation error")
+			}
+		})
+	}
+}
diff --git a/progress.md b/progress.md
index c74a45e..f3b7391 100644
--- a/progress.md
+++ b/progress.md
@@ -51,6 +51,8 @@ The first pass closed the store/API defects (lifecycle defaults, CAS content ver
 
 The latest pass now applies `AuthorizeEvent` to lifecycle and approval writes and adds `/readyz` with router/provider configuration checks. Readiness is configuration-level only; it does not yet probe herdr/provider health.
 
+The lifecycle API contract pass now requires callers to provide explicit release evidence (`reason` or `handoff_ref`), a block `blocker`, and a completion `report_ref`. The server no longer creates generated placeholder completion artifacts or converts malformed/empty lifecycle bodies into defaults. Regression coverage validates that release, completion, and block events reject missing evidence.
+
 Recommended order:
 
 1. Add the orchestration coordinator: lease → worktree → harness session → bootstrap → lifecycle events.