vllm/docs/contributing/model/registration.md

title
Registering a Model to vLLM

{ #new-model-registration }

vLLM relies on a model registry to determine how to run each model. A list of pre-registered architectures can be found [here][supported-models].

If your model is not on this list, you must register it to vLLM. This page provides detailed instructions on how to do so.

Built-in models

To add a model directly to the vLLM library, start by forking our GitHub repository and then [build it from source][build-from-source]. This gives you the ability to modify the codebase and test your model.

After you have implemented your model (see [tutorial][new-model-basic]), put it into the gh-dir:vllm/model_executor/models directory. Then, add your model class to _VLLM_MODELS in gh-file:vllm/model_executor/models/registry.py so that it is automatically registered upon importing vLLM. Finally, update our [list of supported models][supported-models] to promote your model!

!!! warning The list of models in each section should be maintained in alphabetical order.

Out-of-tree models

You can load an external model using a plugin without modifying the vLLM codebase.

!!! info [vLLM's Plugin System][plugin-system]

To register the model, use the following code:

from vllm import ModelRegistry
from your_code import YourModelForCausalLM
ModelRegistry.register_model("YourModelForCausalLM", YourModelForCausalLM)

If your model imports modules that initialize CUDA, consider lazy-importing it to avoid errors like RuntimeError: Cannot re-initialize CUDA in forked subprocess:

from vllm import ModelRegistry

ModelRegistry.register_model(
    "YourModelForCausalLM",
    "your_code:YourModelForCausalLM"
)

!!! warning If your model is a multimodal model, ensure the model class implements the [SupportsMultiModal][vllm.model_executor.models.interfaces.SupportsMultiModal] interface. Read more about that [here][supports-multimodal].

!!! note Although you can directly put these code snippets in your script using vllm.LLM, the recommended way is to place these snippets in a vLLM plugin. This ensures compatibility with various vLLM features like distributed inference and the API server.