diff --git a/comfy/text_encoders/llama.py b/comfy/text_encoders/llama.py
index e9f38a9a2..1fe37db7c 100644
--- a/comfy/text_encoders/llama.py
+++ b/comfy/text_encoders/llama.py
@@ -937,15 +937,21 @@ class BaseGenerate:
             return torch.argmax(logits, dim=-1, keepdim=True)
 
         # Sampling mode
-        if repetition_penalty != 1.0:
-            for i in range(logits.shape[0]):
-                for token_id in set(token_history):
-                    logits[i, token_id] *= repetition_penalty if logits[i, token_id] < 0 else 1/repetition_penalty
-
-        if presence_penalty is not None and presence_penalty != 0.0:
-            for i in range(logits.shape[0]):
-                for token_id in set(token_history):
-                    logits[i, token_id] -= presence_penalty
+        apply_repetition_penalty = repetition_penalty != 1.0
+        apply_presence_penalty = presence_penalty is not None and presence_penalty != 0.0
+        if (apply_repetition_penalty or apply_presence_penalty) and token_history:
+            # Vectorized equivalent of looping over set(token_history) for every batch row.
+            # The original nested Python loop scales as O(len(history)) per generated token and
+            # indexes the logits tensor with scalars, which forces a GPU->CPU sync each step.
+            # Gathering the affected columns once and scattering them back keeps the per-element
+            # arithmetic identical while running entirely on-device.
+            unique_tokens = torch.as_tensor(sorted(set(token_history)), device=logits.device, dtype=torch.long)
+            penalized = logits.index_select(1, unique_tokens)
+            if apply_repetition_penalty:
+                penalized = torch.where(penalized < 0, penalized * repetition_penalty, penalized * (1.0 / repetition_penalty))
+            if apply_presence_penalty:
+                penalized = penalized - presence_penalty
+            logits.index_copy_(1, unique_tokens, penalized)
 
         if temperature != 1.0:
             logits = logits / temperature