Fix hunyuan resolve stop token ids (#3896)

Signed-off-by: zzh <943967662@qq.com>

tests/diffusion/models/hunyuan_image3/test_prompt_utils.py

@@ -124,6 +124,58 @@ def test_resolve_stop_token_ids_image_tasks_stop_on_ratio_range():
     assert resolve_stop_token_ids(task="i2t", bot_task=None, tokenizer=tok) == [answer_id]
     assert resolve_stop_token_ids(task="t2t", bot_task=None, tokenizer=tok) == [answer_id]
 
+    # image_size="auto" is equivalent to None (need_ratio=True).
+    for bot in ("think", "recaption", "think_recaption", "vanilla"):
+        assert resolve_stop_token_ids(task="t2i", bot_task=bot, tokenizer=tok, image_size="auto") == expected
+        assert resolve_stop_token_ids(task="it2i", bot_task=bot, tokenizer=tok, image_size="auto") == expected
+
+
+def test_resolve_stop_token_ids_explicit_image_size_stops_on_terminator():
+    """When image_size is an explicit "WxH" string, need_ratio=False: AR
+    already knows the size and stops at the cot terminator instead of the
+    ratio range.
+
+    Mirrors upstream logic where ``need_ratio`` is false when the user
+    supplies a target size, so ``final_stop_tokens`` is set to the
+    recaption/think terminator (not the ratio tokens).
+    """
+    tok = FakeTokenizer()
+
+    end_of_think_id = HUNYUAN_IMAGE3_SPECIAL_TOKEN_IDS["</think>"]
+    end_of_recaption_id = HUNYUAN_IMAGE3_SPECIAL_TOKEN_IDS["</recaption>"]
+
+    # think_recaption / recaption -> [end_of_recaption]
+    for bot in ("think_recaption", "recaption"):
+        for task in ("t2i", "it2i"):
+            result = resolve_stop_token_ids(task=task, bot_task=bot, tokenizer=tok, image_size="1024x1024")
+            assert result == [end_of_recaption_id], (
+                f"task={task}, bot_task={bot}, image_size='1024x1024': expected [{end_of_recaption_id}], got {result}"
+            )
+
+    # think -> [end_of_think, end_of_recaption]
+    for task in ("t2i", "it2i"):
+        result = resolve_stop_token_ids(task=task, bot_task="think", tokenizer=tok, image_size="1024x1024")
+        assert result == [end_of_think_id, end_of_recaption_id], (
+            f"task={task}, bot_task='think', image_size='1024x1024': "
+            f"expected [{end_of_think_id}, {end_of_recaption_id}], got {result}"
+        )
+
+    # vanilla -> no early return, falls through to ratio range
+    start = HUNYUAN_IMAGE3_SPECIAL_TOKEN_IDS["<img_ratio_0>"]
+    end = HUNYUAN_IMAGE3_SPECIAL_TOKEN_IDS["<img_ratio_32>"]
+    other_start = HUNYUAN_IMAGE3_SPECIAL_TOKEN_IDS["<img_ratio_33>"]
+    other_end = HUNYUAN_IMAGE3_SPECIAL_TOKEN_IDS["<img_ratio_36>"]
+    expected_ratio = list(range(start, end + 1)) + list(range(other_start, other_end + 1))
+    for task in ("t2i", "it2i"):
+        result = resolve_stop_token_ids(task=task, bot_task="vanilla", tokenizer=tok, image_size="1024x1024")
+        assert result == expected_ratio, (
+            f"task={task}, bot_task='vanilla', image_size='1024x1024': expected ratio range, got {result}"
+        )
+
+    # Text tasks are unaffected by image_size.
+    answer_id = HUNYUAN_IMAGE3_SPECIAL_TOKEN_IDS["<answer>"]
+    assert resolve_stop_token_ids(task="i2t", bot_task=None, tokenizer=tok, image_size="1024x1024") == [answer_id]
+
 
 @pytest.mark.parametrize(
     "task,bot_task",