4cdd47b253
## Summary Fixes #33709. When `AnthropicPromptCachingMiddleware` runs before `ModelFallbackMiddleware`, Anthropic-specific `cache_control` markers can leak into fallback attempts targeting non-Anthropic models. This change makes fallback retries sanitize those markers only on non-primary attempts, preserving primary-call behavior and avoiding API changes. Related: langchain-ai/deepagentsjs#551. ## Changes ### libs/langchain_v1 - Added a private fallback sanitizer in `model_fallback.py` to remove Anthropic `cache_control` markers from fallback requests. - Sanitization covers `model_settings`, system/content message blocks, and tool payloads (`BaseTool.extras` plus dict-style tools/extras). - Applied sanitization in both sync and async fallback retry paths (`wrap_model_call` and `awrap_model_call`) while leaving the primary attempt unchanged. ### libs/langchain_v1 tests - Added sync and async regression tests in `test_model_fallback.py` that simulate primary failure and assert fallback calls only succeed when cache markers are stripped. - Verified non-cache settings (for example `temperature` and `top_p`) are preserved on fallback. - Preserved existing fallback behavior coverage (ordering, exhaustion, and error propagation). ## Compatibility with `BedrockPromptCachingMiddleware` The sanitizer also covers `BedrockPromptCachingMiddleware`, which injects `cache_control` into `model_settings` only. Bedrock-specific markers (`cachePoint` blocks, content-block `cache_control`) are applied by the chat model classes at API-call time and never appear in the `ModelRequest`, so no additional handling is needed. --------- Co-authored-by: Mason Daugherty <mason@langchain.dev> Co-authored-by: Mason Daugherty <github@mdrxy.com>
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.