langchain-ai/langchainjs @langchain/anthropic@1.5.12 on GitHub

#11707 4109812 Thanks @richardscarrott! - feat(anthropic): support mid-conversation tool changes. A SystemMessage can now carry Anthropic's tool_addition and tool_removal blocks, either bare in content or wrapped in a non_standard block, and they reach the provider verbatim. The required beta is added automatically: mid-conversation-tool-changes-2026-07-01 for tools named by reference, or inline-tools-2026-09-15 when a tool_addition defines a tool by value (tool: { type: "tool_definition", definition }).
System content is now narrowed to what Anthropic accepts there. text, tool_addition and tool_removal are sent; any other block is dropped instead of being forwarded for the provider to reject. A system message left with no content is omitted.