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Engine Arguments

Engine arguments control the behavior of the vLLM engine.

The engine argument classes, EngineArgs and AsyncEngineArgs, are a combination of the configuration classes defined in vllm.config. Therefore, if you are interested in developer documentation, we recommend looking at these configuration classes as they are the source of truth for types, defaults and docstrings.

When passing JSON CLI arguments, the following sets of arguments are equivalent:

  • --json-arg '{"key1": "value1", "key2": {"key3": "value2"}}'
  • --json-arg.key1 value1 --json-arg.key2.key3 value2

Additionally, list elements can be passed individually using +:

  • --json-arg '{"key4": ["value3", "value4", "value5"]}'
  • --json-arg.key4+ value3 --json-arg.key4+='value4,value5'

EngineArgs

AsyncEngineArgs