My pleasure @Huimin-station 
Sleep well!
- Could this be the reason why my parallel calls failed?
imho, very likely yes - at least one major reason. Check it.
The combination of:
- full-state return from
blank_node, and - raw list concatenation (
operator.add)
can corrupt message history quickly under branching/parallel flow, which then causes downstream tool-call logic to behave incorrectly
No need to apologize. This is exactly how good debugging happens: you shared a minimal reproducible project, asked precise follow-ups, and iterated quickly. That is excellent engineering behavior.