diff --git a/client.go b/client.go
index cf9c91a..f2aec7d 100644
--- a/client.go
+++ b/client.go
@@ -51,7 +51,7 @@ type Client[T any] struct {
 type testHooks struct {
 	beforeSingleflightStart func(ctx context.Context, key string)
 	afterSingleflightStart  func(ctx context.Context, key string)
-	afterMarkRecentWrite    func(ctx context.Context, key string)
+	afterSingleflightEnd    func(ctx context.Context, key string)
 }
 
 // NewClient creates a new client that manages the backend cache and fetches from upstream.
@@ -332,6 +332,9 @@ func (c *Client[T]) fetchFromUpstreamWithSFKey(ctx context.Context, key string,
 	case <-ctx.Done():
 		return zero, errors.Wrapf(ctx.Err(), "context cancelled during fetch for key: %s", key)
 	case res := <-resChan:
+		if c.testHooks != nil && c.testHooks.afterSingleflightEnd != nil {
+			c.testHooks.afterSingleflightEnd(ctx, key)
+		}
 		if res.Err != nil {
 			return zero, res.Err
 		}
@@ -394,10 +397,6 @@ func (c *Client[T]) markRecentWrite(ctx context.Context, key string) {
 	if err != nil {
 		c.logger.WarnContext(ctx, "failed to mark recent write", "key", key, "error", err)
 	}
-
-	if c.testHooks != nil && c.testHooks.afterMarkRecentWrite != nil {
-		c.testHooks.afterMarkRecentWrite(ctx, key)
-	}
 }
 
 // wasRecentlyWritten checks if a key was written (Set or Del) recently
diff --git a/double_check_test.go b/double_check_test.go
index e3fcb00..bbd02ed 100644
--- a/double_check_test.go
+++ b/double_check_test.go
@@ -272,8 +272,8 @@ func TestDoubleCheck(t *testing.T) {
 						<-aCanContinue
 					}
 				},
-				// Hook 2: Confirm A completed marking recent write
-				afterMarkRecentWrite: func(ctx context.Context, key string) {
+				// Hook 2: Confirm A's singleflight completely finished
+				afterSingleflightEnd: func(ctx context.Context, key string) {
 					if key == "key1" && ctx.Value(ctxKeyRequestA) != nil {
 						close(aCompleted)
 					}
@@ -312,7 +312,7 @@ func TestDoubleCheck(t *testing.T) {
 				valueB, errB = client.Get(ctxB, "key1")
 			}()
 
-			// Wait for A to complete marking recent write
+			// Wait for A to complete singleflight (including cleanup)
 			<-aCompleted
 
 			// Advance time if needed (for beyond-window test)
diff --git a/ristretto.go b/ristretto.go
index b670cc4..43d56ff 100644
--- a/ristretto.go
+++ b/ristretto.go
@@ -57,14 +57,20 @@ func (r *RistrettoCache[T]) Set(_ context.Context, key string, value T) error {
 	// 1. Cost exceeds MaxCost (unlikely with cost=1)
 	// 2. Rejected by admission policy (W-TinyLFU)
 	//
+	// When false is returned, the item is dropped and not added to the cache.
+	// When true is returned, the item enters the buffer and will be processed.
+	//
 	// We don't treat rejection as an error because:
 	// - Admission policy rejection is a feature, not a bug
 	// - It prevents cache pollution by low-value entries
 	// - The cache remains consistent and functional
+	// - Callers can still retrieve data from upstream on cache miss
 	success := r.cache.SetWithTTL(key, value, 1, r.ttl)
 	if success {
+		// Wait ensures all buffered writes are applied before returning
 		r.cache.Wait()
 	}
+	// Note: When success is false, there are no buffered writes to wait for
 	return nil
 }