*Description**: My previous
[PR](https://github.com/langchain-ai/langchain/pull/18521) was
mistakenly closed, so I am reopening this one. Context: AWS released two
Mistral models on Bedrock last Friday (March 1, 2024). This PR includes
some code adjustments to ensure their compatibility with the Bedrock
class.
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Co-authored-by: Anis ZAKARI <anis.zakari@hymaia.com>
Co-authored-by: Erick Friis <erick@langchain.dev>
Fixes#18513.
## Description
This PR attempts to fix the support for Anthropic Claude v3 models in
BedrockChat LLM. The changes here has updated the payload to use the
`messages` format instead of the formatted text prompt for all models;
`messages` API is backwards compatible with all models in Anthropic, so
this should not break the experience for any models.
## Notes
The PR in the current form does not support the v3 models for the
non-chat Bedrock LLM. This means, that with these changes, users won't
be able to able to use the v3 models with the Bedrock LLM. I can open a
separate PR to tackle this use-case, the intent here was to get this out
quickly, so users can start using and test the chat LLM. The Bedrock LLM
classes have also grown complex with a lot of conditions to support
various providers and models, and is ripe for a refactor to make future
changes more palatable. This refactor is likely to take longer, and
requires more thorough testing from the community. Credit to PRs
[18579](https://github.com/langchain-ai/langchain/pull/18579) and
[18548](https://github.com/langchain-ai/langchain/pull/18548) for some
of the code here.
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Co-authored-by: Erick Friis <erick@langchain.dev>
Titan Express model was not supported as a chat model because LangChain
messages were not "translated" to a text prompt.
Co-authored-by: Guillem Orellana Trullols <guillem.orellana_trullols@siemens.com>
