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LangChain’s LangGraph project has released version 1.2.12, a developer-focused update that adds a response_schema option to interrupt() and includes fixes for stream typing and subgraph detection. The release was published on September 21, 2026, according to the project’s GitHub release page.
Structured Interrupt Responses
The most visible functional change is support for response_schema in interrupt(). The release notes do not describe the accepted schema format or show an example, so the practical effect depends on how an application currently handles interrupt responses and how the project documents the new option.
Typing And Graph Detection
LangGraph 1.2.12 also fixes typing for undeclared v3 stream projections. That change is relevant to projects consuming streamed graph output, although the release entry does not specify which projection patterns were affected or identify a runtime behavior change.
Another fix changes subgraph detection to use bytecode instead of source code. The release notes identify the implementation change but provide no further detail about the source-code cases that previously caused detection problems.
Dependency Updates
The maintenance portion of the release updates soupsieve from 2.8.4 to 2.9 and tornado from 6.5.7 to 6.5.8. It also updates mistune to 3.3.4, alongside grouped minor, patch and major dependency updates in the LangGraph library.
What Developers Should Check
Teams evaluating the update should pay particular attention to code that calls interrupt(), consumes v3 stream projections or relies on subgraph discovery. The supplied release notes do not state whether the changes require migration work, alter compatibility guarantees or address security issues.
Source: langgraph==1.2.12
SIGNAL TITANS
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