[Release] langchain-ai/langchain langchain-core==1.4.0a2: langchain-core==1.4.0a2

langchain-core version 1.4.0a2 is released with significant improvements to event streaming, tracing, and core functionality. Key updates include unwinding the _AsyncEventsResult hybrid implementation, introducing stream_events(version='v3') protocol, and preserving structured inputs on tool runs in tracers. The release includes numerous bug fixes, performance optimizations, and dependency updates across the LangChain ecosystem.

Key Points

• •Refactored _AsyncEventsResult hybrid for improved async event streaming in astream_events
• •Introduced stream_events(version='v3') protocol for enhanced event streaming capabilities
• •Fixed preservation of structured inputs on tool runs in tracers for better traceability
• •Made 'removal' parameter optional in warn_deprecated function for backward compatibility
• •Validated batch_size in _batch and _abatch methods to prevent infinite loops
• •Marked stream_v2/astream_v2 as beta to indicate stability status
• •Added content-block-centric streaming (v2) for more granular event handling
• •Improved tracer metadata inheritance behavior for special keys
• •Enhanced SSRF (Server-Side Request Forgery) security hardening in cloud metadata
• •Updated tool schema handling to support list of ToolOutputMixin instances in _format_output

Workflow Diagram

Concepts