8aeff95341
Fixes #34517 Supersedes #34557, #34570 Fixes token inflation in `SummarizationMiddleware` that caused context window overflow during summarization. **Root cause:** When formatting messages for the summary prompt, `str(messages)` was implicitly called, which includes all Pydantic metadata fields (`usage_metadata`, `response_metadata`, `additional_kwargs`, etc.). This caused the stringified representation to use ~2.5x more tokens than `count_tokens_approximately` estimates. **Problem:** - Summarization triggers at 85% of context window based on `count_tokens_approximately` - But `str(messages)` in the prompt uses 2.5x more tokens - Results in `ContextLengthExceeded` **Fix:** Use `get_buffer_string()` to format messages, which produces compact output: ``` Human: What's the weather? AI: Let me check...[tool_calls] Tool: 72°F and sunny ``` Instead of verbose Pydantic repr: ```python [HumanMessage(content='What's the weather?', additional_kwargs={}, response_metadata={}), ...] ```
Packages
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.