langchain

a9aa3f23 - feat(langchain_v1): Add retry_model_request middleware hook, add ModelFallbackMiddleware (#33275)

feat(langchain_v1): Add retry_model_request middleware hook, add ModelFallbackMiddleware (#33275) - retry_model_request hook lets a middleware decide to retry a failed model request, with full ability to modify as much or as little of the request before doing so - ModelFallbackMiddleware tries each fallback model in order, until one is successful, or fallback list is exhausted Co-authored-by: Sydney Runkle <54324534+sydney-runkle@users.noreply.github.com>