[Misc] Fix skipped max-model-len validation when deriving max model length from tokenizer config (#19660)

Signed-off-by: Ye (Charlotte) Qi <yeq@meta.com>

Author: yeqcharlotte

tests/test_config.py

@@ -438,3 +438,31 @@ def test_load_config_pt_load_map_location(pt_load_map_location):
     config = VllmConfig(load_config=load_config)
 
     assert config.load_config.pt_load_map_location == pt_load_map_location
+
+
+@pytest.mark.parametrize(
+    ("model_id", "max_model_len", "expected_max_len", "should_raise"), [
+        ("BAAI/bge-reranker-base", None, 512, False),
+        ("BAAI/bge-reranker-base", 256, 256, False),
+        ("BAAI/bge-reranker-base", 513, 512, True),
+    ])
+def test_get_and_verify_max_len(model_id, max_model_len, expected_max_len,
+                                should_raise):
+    """Test get_and_verify_max_len with different configurations."""
+    model_config = ModelConfig(
+        model_id,
+        task="auto",
+        tokenizer=model_id,
+        tokenizer_mode="auto",
+        trust_remote_code=False,
+        seed=0,
+        dtype="float16",
+        revision=None,
+    )
+
+    if should_raise:
+        with pytest.raises(ValueError):
+            model_config.get_and_verify_max_len(max_model_len)
+    else:
+        actual_max_len = model_config.get_and_verify_max_len(max_model_len)
+        assert actual_max_len == expected_max_len

vllm/config.py

@@ -1429,25 +1429,19 @@ def matryoshka_dimensions(self):
         return getattr(self.hf_config, "matryoshka_dimensions", None)
 
     def get_and_verify_max_len(self, max_model_len: int):
+        tokenizer_config = try_get_tokenizer_config(
+            self.tokenizer,
+            trust_remote_code=self.trust_remote_code,
+            revision=self.tokenizer_revision)
         max_model_len = _get_and_verify_max_len(
             hf_config=self.hf_text_config,
+            tokenizer_config=tokenizer_config,
             max_model_len=max_model_len,
             disable_sliding_window=self.disable_sliding_window,
             sliding_window_len=self.get_hf_config_sliding_window(),
             spec_target_max_model_len=self.spec_target_max_model_len,
             encoder_config=self.encoder_config)
-
-        tokenizer_config = try_get_tokenizer_config(
-            self.tokenizer,
-            trust_remote_code=self.trust_remote_code,
-            revision=self.tokenizer_revision)
-
-        if tokenizer_config is None:
-            return max_model_len
-
-        model_max_length = tokenizer_config.get("model_max_length",
-                                                max_model_len)
-        max_model_len = min(max_model_len, model_max_length)
+        logger.info("Using max model len %s", max_model_len)
         return max_model_len
 
 
@@ -3283,6 +3277,7 @@ def _get_and_verify_dtype(
 
 def _get_and_verify_max_len(
     hf_config: PretrainedConfig,
+    tokenizer_config: Optional[dict],
     max_model_len: Optional[int],
     disable_sliding_window: bool,
     sliding_window_len: Optional[Union[int, list[Optional[int]]]],
@@ -3309,7 +3304,7 @@ def _get_and_verify_max_len(
         "max_seq_length",
         "seq_len",
     ]
-    # Choose the smallest "max_length" from the possible keys.
+    # Choose the smallest "max_length" from the possible keys
     max_len_key = None
     for key in possible_keys:
         max_len = getattr(hf_config, key, None)
@@ -3332,6 +3327,13 @@ def _get_and_verify_max_len(
         derived_max_model_len = min(derived_max_model_len,
                                     sliding_window_len_min)
 
+    # Consider model_max_length in tokenizer_config
+    if tokenizer_config:
+        tokenizer_model_max_length = tokenizer_config.get(
+            "model_max_length", derived_max_model_len)
+        derived_max_model_len = min(derived_max_model_len,
+                                    tokenizer_model_max_length)
+
     # If none of the keys were found in the config, use a default and
     # log a warning.
     if derived_max_model_len == float("inf"):