langgraph 0.3.7

Summary of Changes

• Fixed handling of subgraphs with a single node in Graph.add_edge (#3780)
• Added proper Pydantic model validation for graph inputs, with support for both Pydantic v1 and v2 (#3782)

Detailed Changes

langgraph.graph.graph.Graph

• Modified add_edge method to allow adding edges to subgraphs with a single node, changing the condition from len(subgraph.nodes) > 1 to len(subgraph.nodes) >= 1 (#3780)

langgraph.graph.state.StateGraph and langgraph.graph.state.CompiledStateGraph

• Added support for properly validating input against Pydantic models during state graph execution
• Added specialized handling for both Pydantic v1 and v2 models by using their respective constructor methods (construct vs model_construct)
• Improved state coercion with the new _pick_mapper function that correctly handles different schema types (#3782)

langgraph.pregel.Pregel

• Added input_model support to allow for proper Pydantic model validation of inputs
• Modified get_input_schema to prioritize the input model when available
• Updated both synchronous and asynchronous execution paths to pass the input model for validation (#3782)

langgraph.pregel.loop.PregelLoop

• Added validation logic for input data against provided Pydantic models
• Improved handling of resuming executions by properly setting input status
• Enhanced input processing to ensure validation happens at the appropriate time (#3782)