fix(loop): preserve domain-gated readiness

loop.go

@@ -167,6 +167,11 @@ func (w *LoopWorker) Start(ctx context.Context) error {
 			return err
 		}
 	}
+	if !w.autoReady {
+		if err := runtime.SetReady(false); err != nil {
+			return err
+		}
+	}
 
 	// Preserve Start context values for telemetry/correlation, but detach from
 	// Start cancellation because the loop outlives the Start call. Stop uses this
@@ -179,7 +184,7 @@ func (w *LoopWorker) Start(ctx context.Context) error {
 	go w.runLoop(loopCtx, runtime, done)
 
 	if !w.autoReady {
-		return runtime.SetReady(false)
+		return nil
 	}
 	if err := runtime.SetReady(true); err != nil {
 		w.markStopping(done)

loop_test.go

@@ -9,6 +9,18 @@ import (
 	"time"
 )
 
+type loopReadyFailRuntime struct {
+	fakeWorkerRuntime
+	readyFailure error
+}
+
+func (r loopReadyFailRuntime) SetReady(ready bool) error {
+	if !ready {
+		return r.readyFailure
+	}
+	return nil
+}
+
 func TestLoopWorkerStartRejectsNilLoop(t *testing.T) {
 	worker := NewLoopWorker(nil)
 	err := worker.Start(withWorkerRuntime(context.Background(), fakeWorkerRuntime{}))
@@ -187,6 +199,35 @@ func TestLoopWorkerLoopCanMarkReadyWhenAutoReadyDisabled(t *testing.T) {
 	}
 }
 
+func TestLoopWorkerAutoReadyDisabledSetsNotReadyBeforeLoop(t *testing.T) {
+	readyFailure := errors.New("ready false failed")
+	worker := NewLoopWorker(
+		func(ctx context.Context, _ WorkerRuntime) error {
+			<-ctx.Done()
+			return ctx.Err()
+		},
+		WithLoopAutoReady(false),
+	)
+
+	err := worker.Start(withWorkerRuntime(context.Background(), loopReadyFailRuntime{
+		readyFailure: readyFailure,
+	}))
+	if !errors.Is(err, readyFailure) {
+		t.Fatalf("Start error = %v, want %v", err, readyFailure)
+	}
+
+	worker.mu.Lock()
+	state := worker.state
+	done := worker.done
+	worker.mu.Unlock()
+	if state != loopIdle {
+		t.Fatalf("loop worker state = %s, want %s", state, loopIdle)
+	}
+	if done != nil {
+		t.Fatal("loop worker done channel is set, want nil")
+	}
+}
+
 func TestLoopWorkerStopCancelsLoopAndRunsStopHookOnce(t *testing.T) {
 	loopDone := make(chan struct{})
 	var stopCalls atomic.Int32