feat(langchain): MiddlewareTransformer for agent streams#36898
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Nick Hollon (nick-hollon-lc) wants to merge 3 commits intonh/agent-streamerfrom
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feat(langchain): MiddlewareTransformer for agent streams#36898Nick Hollon (nick-hollon-lc) wants to merge 3 commits intonh/agent-streamerfrom
MiddlewareTransformer for agent streams#36898Nick Hollon (nick-hollon-lc) wants to merge 3 commits intonh/agent-streamerfrom
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Adds a native `MiddlewareTransformer` and typed `MiddlewareEvent`
dataclass, pre-registered on `AgentStreamer.builtin_factories` so
every `create_agent` run exposes `run.middleware` alongside
`run.tool_calls` without the caller opting in.
The transformer consumes the graph's existing `updates` stream mode,
filters by the `"{name}.{phase}"` node-naming convention
`create_agent` already uses, and re-emits typed events. Middleware
implementations do not need to change; the node-name convention is
the contract. `run.middleware` is an in-process-only projection.
Lives in langchain (not langgraph prebuilt) because middleware is a
langchain-specific concept — langgraph has no middleware primitive.
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# Conflicts: # libs/langchain_v1/langchain/agents/__init__.py # libs/langchain_v1/langchain/agents/_streaming.py
# Conflicts: # libs/langchain_v1/langchain/agents/factory.py
Nick Hollon (nick-hollon-lc)
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ccurme (ccurme),
Eugene Yurtsev (eyurtsev) and
Mason Daugherty (mdrxy)
as code owners
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Let's consider if we need this.
Mason Daugherty (mdrxy)
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MiddlewareTransformer for agent streams
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Summary
MiddlewareTransformer+ typedMiddlewareEventdataclass, pre-registered onAgentStreamer.builtin_factoriesso everycreate_agentrun exposesrun.middlewarewithout opting in.updatesstream mode and filters by the"{name}.{phase}"node-naming conventioncreate_agentalready uses (before_agent/before_model/after_model/after_agent).run.middlewareis an in-process-only projection; it's not routed anywhere outside the caller's process.ToolCallTransformerlives next toToolNodein langgraph prebuilt.Targeted at
nh/agent-streamer— builds on top ofAgentStreamer.