How to specify a dynamic system prompt in create_react_agent()?

[epistoteles]

I want my system prompt to be dynamically constructed each time a new thread is created.

A simple example would be:

system_prompt = """Today's date: {datetime.today().strftime('%Y-%m-%d')}
<rest of the system prompt>"""

I currently construct my graph with:

graph = create_react_agent(
    ...
    state_modifier=self.system_prompt,
)

What is the easiest way to change this achieve my desired behavior?

[vbarda]

@epistoteles state_modifier can be a callable that takes a graph state and produces an input into the LLM, for example:

def state_modifier(state):
    system_prompt = """Today's date: {datetime.today().strftime('%Y-%m-%d')}<rest of the system prompt>"""
    return [{"role": "system", "content": system_prompt}] + state["messages"]

this actually allows passing more state variables into your prompt as well, for example if you have some state keys like user_info etc, you can pass that information to the prompt as well. NOTE: if you need to add extra state keys to create_react_agent, you'd need to also pass state_schema parameter.

hope this helps!