Passing None as input parameter with Short-Term Memory

[ayeletharcz]

Hi everyone,

I'm currently using LangGraph with short-term memory backed by SQLite, and I've run into some unexpected behavior regarding input parameters and state persistence.

Here's the scenario:

On the first invocation of the graph (using a specific thread_id), I pass an input parameter B with an initial non-None value.

On the second invocation (using the same thread_id), I pass B=None. This is intentional, as B is defined as an optional parameter, and None is a valid input in my use case.

If I provide any non-None value, the graph proceeds correctly with the new value. This behavior seems to occur only when B is explicitly set to None.

I’m trying to understand:

Why does this behavior occur? Is None being treated as an absence of update rather than an explicit value?

Is there a recommended way to ensure that None is properly handled and used to overwrite prior state?

Any insight or guidance would be much appreciated. Thanks!