Remove default values from InitVars so that they're not stored (#29859)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

benchmarks/benchmark_ngram_proposer.py

@@ -108,7 +108,10 @@ def benchmark_batched_propose(args):
         device_config=DeviceConfig(device=current_platform.device_type),
         parallel_config=ParallelConfig(),
         load_config=LoadConfig(),
-        scheduler_config=SchedulerConfig(),
+        scheduler_config=SchedulerConfig(
+            max_model_len=model_config.max_model_len,
+            is_encoder_decoder=model_config.is_encoder_decoder,
+        ),
     )
 
     # monkey patch vllm.v1.worker.gpu_model_runner.get_pp_group

tests/compile/test_fusion_attn.py

@@ -318,13 +318,18 @@ def test_attention_quant_pattern(
     torch.set_default_dtype(dtype)
     torch.manual_seed(42)
 
+    model_config = ModelConfig(
+        model=model_name,
+        max_model_len=2048,
+        dtype=dtype,
+    )
     vllm_config = VllmConfig(
-        model_config=ModelConfig(
+        model_config=model_config,
-            model=model_name,
+        scheduler_config=SchedulerConfig(
-            max_model_len=2048,
+            max_num_seqs=1024,
-            dtype=dtype,
+            max_model_len=model_config.max_model_len,
+            is_encoder_decoder=model_config.is_encoder_decoder,
         ),
-        scheduler_config=SchedulerConfig(max_num_seqs=1024),
         compilation_config=CompilationConfig(
             mode=CompilationMode.VLLM_COMPILE,
             custom_ops=custom_ops_list,

tests/lora/test_worker.py

@@ -33,14 +33,16 @@ def test_worker_apply_lora(qwen3_lora_files):
             lora_requests, lora_mapping
         )
 
+    model_config = ModelConfig(
+        MODEL_PATH,
+        seed=0,
+        dtype="float16",
+        max_model_len=127,
+        enforce_eager=True,
+    )
+
     vllm_config = VllmConfig(
-        model_config=ModelConfig(
+        model_config=model_config,
-            MODEL_PATH,
-            seed=0,
-            dtype="float16",
-            max_model_len=127,
-            enforce_eager=True,
-        ),
         load_config=LoadConfig(
             download_dir=None,
             load_format="dummy",
@@ -50,7 +52,14 @@ def test_worker_apply_lora(qwen3_lora_files):
             tensor_parallel_size=1,
             data_parallel_size=1,
         ),
-        scheduler_config=SchedulerConfig("generate", 32, 32, 32),
+        scheduler_config=SchedulerConfig(
+            max_model_len=model_config.max_model_len,
+            is_encoder_decoder=model_config.is_encoder_decoder,
+            runner_type="generate",
+            max_num_batched_tokens=32,
+            max_num_seqs=32,
+            max_num_partial_prefills=32,
+        ),
         device_config=DeviceConfig("cuda"),
         cache_config=CacheConfig(
             block_size=16,

tests/test_config.py

@@ -6,12 +6,14 @@ from dataclasses import MISSING, Field, asdict, dataclass, field
 from unittest.mock import patch
 
 import pytest
+from pydantic import ValidationError
 
 from vllm.compilation.backends import VllmBackend
 from vllm.config import (
     CompilationConfig,
     ModelConfig,
     PoolerConfig,
+    SchedulerConfig,
     VllmConfig,
     update_config,
 )
@@ -1095,3 +1097,14 @@ def test_vllm_config_explicit_overrides():
     # Other fields should still use defaults
     assert config.compilation_config.mode == CompilationMode.VLLM_COMPILE
     assert config.compilation_config.cudagraph_mode == CUDAGraphMode.FULL_AND_PIECEWISE
+
+
+def test_scheduler_config_init():
+    with pytest.raises(ValidationError):
+        # Positional InitVars missing
+        # (InitVars cannot have defaults otherwise they will become attributes)
+        SchedulerConfig()
+
+    with pytest.raises(AttributeError):
+        # InitVar does not become an attribute
+        print(SchedulerConfig.default_factory().max_model_len)

tests/v1/attention/utils.py

@@ -185,6 +185,8 @@ def create_vllm_config(
         max_num_seqs=max_num_seqs,
         max_num_batched_tokens=max_num_batched_tokens,
         enable_chunked_prefill=enable_chunked_prefill,
+        max_model_len=model_config.max_model_len,
+        is_encoder_decoder=model_config.is_encoder_decoder,
     )
 
     device_config = DeviceConfig()

tests/v1/core/test_kv_cache_utils.py

@@ -1128,7 +1128,11 @@ def test_estimate_max_model_len(model_id, max_model_len, want_estimated_max_len)
         dtype="float16",
         max_model_len=max_model_len,
     )
-    scheduler_config = SchedulerConfig(max_num_batched_tokens=32768)
+    scheduler_config = SchedulerConfig(
+        max_num_batched_tokens=32768,
+        max_model_len=model_config.max_model_len,
+        is_encoder_decoder=model_config.is_encoder_decoder,
+    )
 
     vllm_config = VllmConfig(
         model_config=model_config,
@@ -1163,7 +1167,10 @@ def test_get_max_concurrency_for_kv_cache_config():
         max_model_len=max_model_len,
     )
     scheduler_config = SchedulerConfig(
-        max_num_batched_tokens=1024, enable_chunked_prefill=True
+        max_num_batched_tokens=1024,
+        enable_chunked_prefill=True,
+        max_model_len=model_config.max_model_len,
+        is_encoder_decoder=model_config.is_encoder_decoder,
     )
 
     vllm_config = VllmConfig(

tests/v1/core/test_scheduler.py

@@ -1508,6 +1508,12 @@ def create_scheduler_with_priority(
     Returns:
       {class}`Scheduler` instance with priority scheduling
     """
+    model_config = ModelConfig(
+        model=model,
+        trust_remote_code=True,
+        dtype="float16",
+        seed=42,
+    )
     if max_model_len is None:
         max_model_len = max_num_batched_tokens
     scheduler_config = SchedulerConfig(
@@ -1517,14 +1523,9 @@ def create_scheduler_with_priority(
         long_prefill_token_threshold=long_prefill_token_threshold,
         disable_chunked_mm_input=disable_chunked_mm_input,
         enable_chunked_prefill=True,
+        is_encoder_decoder=model_config.is_encoder_decoder,
         policy="priority",  # Enable priority scheduling
     )
-    model_config = ModelConfig(
-        model=model,
-        trust_remote_code=True,
-        dtype="float16",
-        seed=42,
-    )
     # Cache config, optionally force APC
     cache_config = CacheConfig(
         block_size=block_size,

tests/v1/core/utils.py

@@ -69,6 +69,13 @@ def create_scheduler(
     Returns:
       {class}`Scheduler` instance
     """
+    model_config = ModelConfig(
+        model=model,
+        trust_remote_code=True,
+        dtype="float16",
+        seed=42,
+        skip_tokenizer_init=skip_tokenizer_init,
+    )
     if max_model_len is None:
         max_model_len = max_num_batched_tokens
     scheduler_config = SchedulerConfig(
@@ -79,13 +86,7 @@ def create_scheduler(
         disable_chunked_mm_input=disable_chunked_mm_input,
         enable_chunked_prefill=enable_chunked_prefill,
         async_scheduling=async_scheduling,
-    )
+        is_encoder_decoder=model_config.is_encoder_decoder,
-    model_config = ModelConfig(
-        model=model,
-        trust_remote_code=True,
-        dtype="float16",
-        seed=42,
-        skip_tokenizer_init=skip_tokenizer_init,
     )
     # Cache config, optionally force APC
     cache_config = CacheConfig(

tests/v1/cudagraph/test_cudagraph_dispatch.py

@@ -40,7 +40,9 @@ def _create_vllm_config(
 ) -> MagicMock:
     mock_config = MagicMock(spec=VllmConfig)
     mock_config.compilation_config = compilation_config
-    mock_config.scheduler_config = SchedulerConfig(max_num_seqs=max_num_seqs)
+    mock_config.scheduler_config = SchedulerConfig.default_factory(
+        max_num_seqs=max_num_seqs,
+    )
     mock_config.parallel_config = ParallelConfig()
     mock_config.speculative_config = None  # No speculative decoding
     if not lora_config:

tests/v1/engine/test_engine_core.py

@@ -484,12 +484,6 @@ def test_encoder_instance_zero_kv_cache(
     vision encoder, so they don't need KV cache for text generation.
     """
     # Form vllm config
-    scheduler_config = SchedulerConfig(
-        max_num_seqs=10,
-        max_num_batched_tokens=512,
-        max_model_len=512,
-        disable_hybrid_kv_cache_manager=True,
-    )
     model_config = ModelConfig(
         model="llava-hf/llava-1.5-7b-hf",  # Multimodal model
         enforce_eager=True,
@@ -497,6 +491,13 @@ def test_encoder_instance_zero_kv_cache(
         dtype="float16",
         seed=42,
     )
+    scheduler_config = SchedulerConfig(
+        max_num_seqs=10,
+        max_num_batched_tokens=512,
+        max_model_len=512,
+        disable_hybrid_kv_cache_manager=True,
+        is_encoder_decoder=model_config.is_encoder_decoder,
+    )
     cache_config = CacheConfig(
         block_size=16,
         gpu_memory_utilization=gpu_memory_utilization,

tests/v1/kv_connector/unit/utils.py

@@ -92,18 +92,19 @@ def create_vllm_config(
     enable_permute_local_kv: bool = False,
 ) -> VllmConfig:
     """Initialize VllmConfig For Testing."""
-    scheduler_config = SchedulerConfig(
-        max_num_seqs=max_num_seqs,
-        max_num_batched_tokens=max_num_batched_tokens,
-        max_model_len=max_model_len,
-        enable_chunked_prefill=enable_chunked_prefill,
-    )
     model_config = ModelConfig(
         model=model,
         trust_remote_code=True,
         dtype="float16",
         seed=42,
     )
+    scheduler_config = SchedulerConfig(
+        max_num_seqs=max_num_seqs,
+        max_num_batched_tokens=max_num_batched_tokens,
+        max_model_len=max_model_len,
+        enable_chunked_prefill=enable_chunked_prefill,
+        is_encoder_decoder=model_config.is_encoder_decoder,
+    )
     # Cache config, optionally force APC
     cache_config = CacheConfig(
         block_size=block_size,

tests/v1/spec_decode/test_eagle.py

@@ -66,7 +66,10 @@ def _create_proposer(
         device_config=DeviceConfig(device=current_platform.device_type),
         parallel_config=ParallelConfig(),
         load_config=LoadConfig(),
-        scheduler_config=SchedulerConfig(),
+        scheduler_config=SchedulerConfig(
+            max_model_len=model_config.max_model_len,
+            is_encoder_decoder=model_config.is_encoder_decoder,
+        ),
     )
 
     return EagleProposer(vllm_config=vllm_config, device=current_platform.device_type)

tests/v1/spec_decode/test_mtp.py

@@ -51,7 +51,10 @@ def _create_mtp_proposer(num_speculative_tokens: int) -> EagleProposer:
         device_config=DeviceConfig(device=current_platform.device_type),
         parallel_config=ParallelConfig(),
         load_config=LoadConfig(),
-        scheduler_config=SchedulerConfig(),
+        scheduler_config=SchedulerConfig(
+            max_model_len=model_config.max_model_len,
+            is_encoder_decoder=model_config.is_encoder_decoder,
+        ),
     )
 
     return EagleProposer(vllm_config=vllm_config, device=current_platform.device_type)

tests/v1/tpu/worker/test_tpu_model_runner.py

@@ -26,16 +26,17 @@ from vllm.v1.worker.tpu_model_runner import (
 
 
 def get_vllm_config():
-    scheduler_config = SchedulerConfig(
-        max_num_seqs=10,
-        max_num_batched_tokens=512,
-        max_model_len=512,
-    )
     model_config = ModelConfig(
         model="facebook/opt-125m",
         dtype="bfloat16",  # TPUs typically use bfloat16
         seed=42,
     )
+    scheduler_config = SchedulerConfig(
+        max_num_seqs=10,
+        max_num_batched_tokens=512,
+        max_model_len=512,
+        is_encoder_decoder=model_config.is_encoder_decoder,
+    )
     cache_config = CacheConfig(
         block_size=16,
         gpu_memory_utilization=0.9,

tests/v1/worker/test_gpu_model_runner.py

@@ -79,16 +79,17 @@ def initialize_kv_cache(runner: GPUModelRunner):
 
 
 def get_vllm_config():
-    scheduler_config = SchedulerConfig(
-        max_num_seqs=10,
-        max_num_batched_tokens=512,
-        max_model_len=512,
-    )
     model_config = ModelConfig(
         model="facebook/opt-125m",
         dtype="float16",
         seed=42,
     )
+    scheduler_config = SchedulerConfig(
+        max_num_seqs=10,
+        max_num_batched_tokens=512,
+        max_model_len=512,
+        is_encoder_decoder=model_config.is_encoder_decoder,
+    )
     cache_config = CacheConfig(
         block_size=BLOCK_SIZE,
         gpu_memory_utilization=0.9,
@@ -784,14 +785,15 @@ def test_hybrid_attention_mamba_tensor_shapes(monkeypatch):
     initialize_model_parallel(tensor_model_parallel_size=1)
     torch.set_default_dtype(torch.float16)
 
+    model_config = ModelConfig(
+        model="ibm-granite/granite-4.0-tiny-preview",
+        dtype="float16",
+    )
     scheduler_config = SchedulerConfig(
         max_num_seqs=10,
         max_num_batched_tokens=512,
         max_model_len=512,
-    )
+        is_encoder_decoder=model_config.is_encoder_decoder,
-    model_config = ModelConfig(
-        model="ibm-granite/granite-4.0-tiny-preview",
-        dtype="float16",
     )
     cache_config = CacheConfig(
         block_size=BLOCK_SIZE,

vllm/config/scheduler.py

@@ -28,6 +28,19 @@ SchedulerPolicy = Literal["fcfs", "priority"]
 class SchedulerConfig:
     """Scheduler configuration."""
 
+    max_model_len: InitVar[int]
+    """Maximum length of a sequence (including prompt and generated text).
+
+    Note: This is stored in the ModelConfig, and is used only here to
+    provide fallbacks and validate other attributes."""
+
+    is_encoder_decoder: InitVar[bool]
+    """True if the model is an encoder-decoder model.
+
+    Note: This is stored in the ModelConfig, and is used only here to
+    disable chunked prefill and prefix caching for encoder-decoder models.
+    """
+
     DEFAULT_MAX_NUM_BATCHED_TOKENS: ClassVar[int] = 2048
     DEFAULT_MAX_NUM_SEQS: ClassVar[int] = 128
 
@@ -73,19 +86,6 @@ class SchedulerConfig:
     is_multimodal_model: bool = False
     """True if the model is multimodal."""
 
-    max_model_len: InitVar[int] = 8192
-    """Maximum length of a sequence (including prompt and generated text).
-
-    Note: This is stored in the ModelConfig, and is used only here to
-    provide fallbacks and validate other attributes."""
-
-    is_encoder_decoder: InitVar[bool] = False
-    """True if the model is an encoder-decoder model.
-
-    Note: This is stored in the ModelConfig, and is used only here to
-    disable chunked prefill and prefix caching for encoder-decoder models.
-    """
-
     # TODO (ywang96): Make this configurable.
     max_num_encoder_input_tokens: int = Field(init=False)
     """Multimodal encoder compute budget, only used in V1.
@@ -141,6 +141,17 @@ class SchedulerConfig:
     while a larger value (e.g., 10) reduces host overhead and may increase throughput
     by batching multiple tokens before sending."""
 
+    @staticmethod
+    def default_factory(**kwargs):
+        """
+        Factory method to create `SchedulerConfig` with default values for `InitVar`s.
+        """
+        if "max_model_len" not in kwargs:
+            kwargs["max_model_len"] = 8192
+        if "is_encoder_decoder" not in kwargs:
+            kwargs["is_encoder_decoder"] = False
+        return SchedulerConfig(**kwargs)
+
     def get_scheduler_cls(self) -> type["SchedulerInterface"]:
         if self.scheduler_cls is None:
             if self.async_scheduling:
@@ -284,8 +295,3 @@ class SchedulerConfig:
             )
 
         return self
-
-    def __getattribute__(self, name: str) -> Any:
-        if name == "max_model_len" or name == "is_encoder_decoder":
-            raise AttributeError(f"{name} is an init-only parameter. ")
-        return object.__getattribute__(self, name)

vllm/config/vllm.py

@@ -170,7 +170,9 @@ class VllmConfig:
     """Cache configuration."""
     parallel_config: ParallelConfig = Field(default_factory=ParallelConfig)
     """Parallel configuration."""
-    scheduler_config: SchedulerConfig = Field(default_factory=SchedulerConfig)
+    scheduler_config: SchedulerConfig = Field(
+        default_factory=SchedulerConfig.default_factory,
+    )
     """Scheduler configuration."""
     device_config: DeviceConfig = Field(default_factory=DeviceConfig)
     """Device configuration."""