LangGraph Studio + LangSmith: Support for Pydantic-based State in LangGraph

[jaroslav-bellus]

I'm using Pydantic models to define the state in LangGraph (instead of TypedDict). While this works fine generally, I'm running into an issue when using interrupts in LangGraph Studio (integrated with LangSmith).

It seems that when an interrupt occurs, the state is deserialized back into a dictionary, and the Pydantic structure is lost. This causes problems when the graph resumes, since it's expecting a Pydantic model, not a plain dict.

Specifically:

• Is this expected behavior when using interrupts with Pydantic-based state?
• Does LangGraph Studio (integrated with LangSmith) support working with Pydantic models in this context?
• Are there workarounds or best practices for preserving Pydantic state across interruptions?

Any insights or pointers to documentation would be appreciated!

[mingle-stripe]

Also ran into this and was very surprised. I believe it has to be a bug.

[nirmal-joji]

I have a similar issue, not only with interrupts but with the regular run as well.

Are you able to use LangGraph Studio when using nested Pydantic models as the state?