When calling a RunnableLambda A returning a chain B with ainvoke, we would expect the new chain B to be called with ainvoke; However, if the function provided to RunnableLambda A is not async, then ...

The issue you're experiencing is due to the fact that the RunnableLambda class does not have a run method defined. Instead, it has several other methods like invoke, ainvoke, batch, abatch, stream, ...