PrefixMiddleware Class — langchain Architecture

Architecture documentation for the PrefixMiddleware class in test_wrap_model_call.py from the langchain codebase.

Class python

Entity Profile

Dependency Diagram

graph TD
  b839d145_bd7e_f8f3_8f04_82e22e52c46d["PrefixMiddleware"]
  949c7cf4_56fe_f3b4_cd89_9631a7e9cb1e["AgentMiddleware"]
  b839d145_bd7e_f8f3_8f04_82e22e52c46d -->|extends| 949c7cf4_56fe_f3b4_cd89_9631a7e9cb1e
  573473e5_eb93_a7d7_84ba_c975071c09af["test_wrap_model_call.py"]
  b839d145_bd7e_f8f3_8f04_82e22e52c46d -->|defined in| 573473e5_eb93_a7d7_84ba_c975071c09af
  e843b9ae_bd50_34f9_9423_1a9ed0e30249["__init__()"]
  b839d145_bd7e_f8f3_8f04_82e22e52c46d -->|method| e843b9ae_bd50_34f9_9423_1a9ed0e30249
  f6e2a08e_524d_cddd_7ef8_edc56357f732["wrap_model_call()"]
  b839d145_bd7e_f8f3_8f04_82e22e52c46d -->|method| f6e2a08e_524d_cddd_7ef8_edc56357f732

Relationship Graph

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_model_call.py lines 324–337

        class PrefixMiddleware(AgentMiddleware):
            def __init__(self, prefix: str):
                super().__init__()
                self.prefix = prefix

            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ModelCallResult:
                result = handler(request)
                # result is ModelResponse, extract AIMessage from it
                ai_message = result.result[0]
                return AIMessage(content=f"{self.prefix}{ai_message.content}")