Adding MaxTextForCausalLM interface.

Author: NicoGrande

src/MaxText/integration/vllm/__init__.py

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+# Copyright 2023–2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.

src/MaxText/integration/vllm/maxtext_vllm_adapter/__init__.py

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+# Copyright 2023–2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""MaxText vLLM adapter package."""
+
+from tpu_inference.logger import init_logger
+from tpu_inference.models.common.model_loader import register_model
+from .adapter import MaxTextForCausalLM
+
+
+logger = init_logger(__name__)
+
+
+def register():
+  logger.info("Registering MaxTextForCausalLM model with tpu_inference and vllm.")
+  register_model("MaxTextForCausalLM", MaxTextForCausalLM)
+  logger.info("Successfully registered MaxTextForCausalLM model.")

src/MaxText/integration/vllm/maxtext_vllm_adapter/adapter.py

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+# Copyright 2023–2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""vLLM adapter for MaxText models."""
+
+import jax
+import pathlib
+import os
+import jax.numpy as jnp
+
+from flax import nnx
+from jax.sharding import Mesh
+from MaxText import model_creation_utils
+from MaxText import pyconfig
+from MaxText.common_types import MODEL_MODE_AUTOREGRESSIVE
+from MaxText.globals import MAXTEXT_PKG_DIR
+from MaxText.utils import gcs_utils
+
+from tpu_inference.layers.common.attention_metadata import AttentionMetadata
+from vllm.config import VllmConfig
+
+
+def generate_maxtext_config(vllm_config: VllmConfig) -> pyconfig.HyperParameters:
+  """Generates a MaxText configuration from a vLLM configuration.
+
+  This function takes a vLLM configuration object and translates relevant
+  parameters into a MaxText `HyperParameters` object. It handles loading
+  paths and model names from the vLLM config, and applies a base MaxText
+  vLLM configuration file.
+
+  Args:
+    vllm_config: The vLLM configuration object containing model and load
+      parameters.
+
+  Returns:
+    A `pyconfig.HyperParameters` object configured for MaxText.
+
+  Raises:
+    ValueError: If `hf_config_path` is not provided in the vLLM model config.
+  """
+
+  def _path_exists(path: str) -> bool:
+    if not path:
+      return False
+    return os.path.exists(path) or gcs_utils.gcs_path_exists(path)
+
+  if "maxtext_config" in vllm_config.additional_config:
+    overrides = vllm_config.additional_config["maxtext_config"]
+  else:
+    overrides = {}
+    load_path = None
+    if _path_exists(vllm_config.load.download_dir):
+      load_path = vllm_config.load.download_dir
+    elif _path_exists(vllm_config.model.model):
+      load_path = vllm_config.model.model
+
+    if load_path:
+      overrides["load_parameters_path"] = load_path
+    elif vllm_config.model.model:
+      overrides["model_name"] = vllm_config.model.model
+
+  if vllm_config.model_config.hf_config_path is None:
+    raise ValueError("hf_config_path must be provided when using MaxTextForCausalLM.")
+
+    # Add base config path to positional args
+  base_config_path = pathlib.Path(MAXTEXT_PKG_DIR) / "configs" / "vllm.yml"
+  argv_list = ["", str(base_config_path)]
+
+  maxtext_config = pyconfig.initialize(argv_list, **overrides)
+  return maxtext_config
+
+
+class MaxTextDecoderModel(nnx.Module):
+  """A vLLM-compatible decoder model wrapper for MaxText.
+
+  This class adapts a MaxText model for use within the vLLM framework,
+  handling configuration generation, model initialization, and execution
+  of the decoding step.
+  """
+
+  def __init__(self, vllm_config: VllmConfig, rng_key: jax.Array, mesh: Mesh) -> None:
+    """Initializes the MaxTextDecoderModel.
+
+    Args:
+      vllm_config: The vLLM configuration object.
+      rng_key: A JAX random key for model initialization.
+      mesh: The JAX mesh device for model sharding.
+    """
+    self.vllm_config = vllm_config
+    self.maxtext_config = generate_maxtext_config(vllm_config)
+
+    # Model configuration
+    self.mesh = mesh
+    self.model_mode = MODEL_MODE_AUTOREGRESSIVE
+
+    # Model creation
+    self.model: nnx.Module | None = None
+    self.logits: jax.Array | None = None
+
+  def __call__(
+      self,
+      kv_caches: list[jax.Array],
+      input_ids: jax.Array,
+      attention_metadata: AttentionMetadata,
+      *args,
+      **kwargs,
+  ) -> tuple[list[jax.Array], jax.Array]:
+    """Performs a forward pass through the decoder model.
+
+    Args:
+      kv_caches: A list of JAX arrays representing the KV caches.
+      input_ids: A JAX array of input token IDs.
+      attention_metadata: Attention metadata for the decoding process.
+      *args: Variable length argument list.
+      **kwargs: Arbitrary keyword arguments.
+
+    Returns:
+      A tuple containing:
+        - updated_kv_caches: A list of updated KV caches.
+        - hidden: The hidden states (Q, d_model).
+        - aux_hidden_states: A list of auxiliary hidden states.
+
+    Raises:
+      ValueError: If the model is not an instance of `nnx.Module`.
+    """
+    if not isinstance(self.model, nnx.Module):
+      raise ValueError("Model must be an instance of type nnx.Module.")
+
+    if input_ids.ndim < 2:
+      input_ids = jnp.expand_dims(input_ids, axis=0)
+
+    input_positions = attention_metadata.input_positions
+    if input_positions.ndim < 2:
+      input_positions = jnp.expand_dims(input_positions, axis=0)
+
+    aux_hidden_states = []
+    logits, hidden, kv_caches = self.model(
+        decoder_input_tokens=input_ids,
+        decoder_positions=input_positions,
+        kv_caches=kv_caches,
+        attention_metadata=attention_metadata,
+        model_mode=self.model_mode,
+        **kwargs,
+    )
+    if hidden.ndim > 1:
+      hidden = jnp.squeeze(hidden, axis=0)
+      logits = jnp.squeeze(logits, axis=0)
+
+    self.logits = logits  # cache logits for compute_logits call
+
+    return kv_caches, hidden, aux_hidden_states
+
+  def compute_logits(self, hidden_states: jax.Array) -> jax.Array:
+    """Computes the logits from the hidden states.
+
+    Args:
+      hidden_states: A JAX array of hidden states.
+
+    Returns:
+      A JAX array of logits (Q, vocab_size).
+    """
+    if self.logits is not None:
+      return self.logits
+
+    embeddings = self.model.token_embedder
+    # pylint: disable=protected-access
+    return self.model.decoder._apply_output_head(embeddings, hidden_states, True, self.model_mode)
+
+  def load_weights(self, rng_key: jax.Array) -> None:
+    """Loads model parameters on the provided mesh.
+
+    Args:
+      rng_key: A JAX random key for model initialization.
+    """
+    self.model, _ = model_creation_utils.create_nnx_model(
+        self.maxtext_config, mesh=self.mesh, model_mode=self.model_mode, rng_key=rng_key
+    )
+
+
+class MaxTextForCausalLM(nnx.Module):
+  """A vLLM-compatible causal language model wrapper for MaxText.
+
+  This class serves as the primary interface for integrating MaxText models
+  into the vLLM serving framework, specifically for causal language modeling
+  tasks. It wraps the `MaxTextDecoderModel` and exposes methods expected
+  by vLLM.
+  """
+
+  def __init__(self, vllm_config: VllmConfig, rng_key: jax.Array, mesh: Mesh):
+    """Initializes the MaxTextForCausalLM model.
+
+    Args:
+      vllm_config: The vLLM configuration object.
+      rng_key: A JAX random key for model initialization.
+      mesh: The JAX mesh device for model sharding.
+    """
+    self.cfg = vllm_config.model_config
+    self.mesh = mesh
+    self.model = MaxTextDecoderModel(vllm_config, rng_key, mesh)
+    self.is_text_generation_model = True
+
+  def __call__(
+      self, kv_caches: list[jax.Array], input_ids: jax.Array, attention_metadata: AttentionMetadata, *args, **kwargs
+  ) -> tuple[list[jax.Array], jax.Array]:
+    """Performs a forward pass through the causal language model.
+
+    Args:
+      kv_caches: A list of JAX arrays representing the KV caches.
+      input_ids: A JAX array of input token IDs.
+      attention_metadata: Attention metadata for the decoding process.
+      *args: Variable length argument list.
+      **kwargs: Arbitrary keyword arguments.
+
+    Returns:
+      A tuple containing:
+        - updated_kv_caches: A list of updated KV caches.
+        - hidden: The hidden states.
+        - aux_hidden_states: A list of auxiliary hidden states.
+    """
+    kv_caches, hidden, aux_hidden_states = self.model(kv_caches, input_ids, attention_metadata, *args, **kwargs)
+    return kv_caches, hidden, aux_hidden_states
+
+  def forward(self, *args, **kwargs):
+    """Alias for __call__ for compatibility.
+
+    Args:
+      *args: Variable length argument list.
+      **kwargs: Arbitrary keyword arguments.
+
+    Returns:
+      The result of the `__call__` method.
+    """
+    return self(*args, **kwargs)
+
+  def get_input_embeddings(self) -> jax.Array:
+    """Returns the input embeddings of the model.
+
+    Returns:
+      A JAX array representing the input embeddings.
+    """
+    return self.model.model.token_embedder.embedding
+
+  def compute_logits(self, hidden_states: jax.Array) -> jax.Array:
+    """Computes the logits from the hidden states using the underlying decoder model.
+
+    Args:
+      hidden_states: A JAX array of hidden states.
+
+    Returns:
+      A JAX array of logits.
+    """
+    return self.model.compute_logits(hidden_states)
+
+  def load_weights(self, rng_key: jax.Array) -> None:
+    """Loads model weights using the underlying decoder model.
+
+    Args:
+      rng_key: A JAX random key for model initialization.
+    """
+    self.model.load_weights(rng_key)

src/MaxText/integration/vllm/setup.py

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+# Copyright 2023–2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Setup for MaxText vLLM adapter package."""
+
+from setuptools import setup
+
+setup(
+    name="maxtext_vllm_adapter",
+    version="0.1.0",
+    packages=["maxtext_vllm_adapter"],
+    entry_points={"vllm.general_plugins": ["register_maxtext_vllm_adapter = maxtext_vllm_adapter:register"]},
+)