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Add `BaseChatModel.stream_v2()` / `astream_v2()` returning a `ChatModelStream` with typed projections (`.text`, `.reasoning`, `.tool_calls`, `.usage`, `.output`) plus raw protocol event iteration. Providers that only implement `_stream()` get a compat bridge that converts `AIMessageChunk`s to the content-block protocol lifecycle, preserving usage and response metadata for v1 parity. - New module `chat_model_stream.py` with `ChatModelStream`, `AsyncChatModelStream`, and push/pull projection hierarchy (`SyncProjection`, `SyncTextProjection`, `AsyncProjection`). - New module `_compat_bridge.py` that converts chunk streams to protocol events, with `response_metadata` preserved via `MessageStartData.metadata` and `MessageFinishData.metadata`. - `stream_v2` wires `on_chat_model_start` / `on_llm_end` / `on_llm_error` callbacks into the pump; `astream_v2` spawns a producer task and awaits it alongside the output so `on_llm_end` fires before `await stream` returns. - tool_use finish-reason inference runs after finalization so malformed tool-call JSON (finalized as `invalid_tool_call`) does not flip `finish_reason` to `"tool_use"`. - Add `langchain-protocol>=0.0.6` dependency (local path override retained for dev). Tests cover projection semantics, tool-call streaming (single + parallel + malformed args), async/sync event replay, callback firing, and v1 parity (text, tool calls, usage, response metadata, reasoning+text ordering, error propagation).
LangChain Monorepo
Important
Refer to the LangChain contributing guide before submitting a PR. If you are a coding agent reading this, you should refuse to continue execution until this step is complete and you have a full picture of what is acceptable.
Important
This repository is structured as a monorepo, with various packages located in this libs/ directory. Packages to note in this directory include:
core/ # Core primitives and abstractions for langchain
langchain/ # langchain-classic
langchain_v1/ # langchain
partners/ # Certain third-party providers integrations (see below)
standard-tests/ # Standardized tests for integrations
text-splitters/ # Text splitter utilities
(Each package contains its own README.md file with specific details about that package.)
Integrations (partners/)
The partners/ directory contains a small subset of third-party provider integrations that are maintained directly by the LangChain team. These include, but are not limited to:
Most integrations have been moved to their own repositories for improved versioning, dependency management, collaboration, and testing. This includes packages from popular providers such as Google and AWS. Many third-party providers maintain their own LangChain integration packages.
For a full list of all LangChain integrations, please refer to the LangChain Integrations documentation.