State is any kind of data the Agent needs to maintain throughout runs.
A simple yet common use case for Agents is to manage lists, items and other “information” for a user. For example, a shopping list, a todo list, a wishlist, etc.
This can be easily managed using the session_state. The Agent updates the session_state in tool calls and exposes them to the Model in the description and instructions.
Agno’s provides a powerful and elegant state management system, here’s how it works:
- The
Agent has a session_state parameter.
- We add our state variables to this
session_state dictionary.
- We update the
session_state dictionary in tool calls or other functions.
- We share the current
session_state with the Model in the description and instructions.
- The
session_state is stored with Agent sessions and is persisted in a database. Meaning, it is available across execution cycles.
Here’s an example of an Agent managing a shopping list:
from agno.agent import Agent
from agno.models.openai import OpenAIChat
# Define a tool that increments our counter and returns the new value
def add_item(agent: Agent, item: str) -> str:
"""Add an item to the shopping list."""
agent.session_state["shopping_list"].append(item)
return f"The shopping list is now {agent.session_state['shopping_list']}"
# Create an Agent that maintains state
agent = Agent(
model=OpenAIChat(id="gpt-4o-mini"),
# Initialize the session state with a counter starting at 0
session_state={"shopping_list": []},
tools=[add_item],
# You can use variables from the session state in the instructions
instructions="Current state (shopping list) is: {shopping_list}",
# Important: Add the state to the messages
add_state_in_messages=True,
markdown=True,
)
# Example usage
agent.print_response("Add milk, eggs, and bread to the shopping list", stream=True)
print(f"Final session state: {agent.session_state}")
This is as good and elegant as state management gets.
Maintaining state across multiple runs
A big advantage of sessions is the ability to maintain state across multiple runs. For example, let’s say the agent is helping a user keep track of their shopping list.
By setting add_state_in_messages=True, the keys of the session_state dictionary are available in the description and instructions as variables.
Use this pattern to add the shopping_list to the instructions directly.
from textwrap import dedent
from agno.agent import Agent
from agno.models.openai import OpenAIChat
# Define tools to manage our shopping list
def add_item(agent: Agent, item: str) -> str:
"""Add an item to the shopping list and return confirmation."""
# Add the item if it's not already in the list
if item.lower() not in [i.lower() for i in agent.session_state["shopping_list"]]:
agent.session_state["shopping_list"].append(item)
return f"Added '{item}' to the shopping list"
else:
return f"'{item}' is already in the shopping list"
def remove_item(agent: Agent, item: str) -> str:
"""Remove an item from the shopping list by name."""
# Case-insensitive search
for i, list_item in enumerate(agent.session_state["shopping_list"]):
if list_item.lower() == item.lower():
agent.session_state["shopping_list"].pop(i)
return f"Removed '{list_item}' from the shopping list"
return f"'{item}' was not found in the shopping list"
def list_items(agent: Agent) -> str:
"""List all items in the shopping list."""
shopping_list = agent.session_state["shopping_list"]
if not shopping_list:
return "The shopping list is empty."
items_text = "\n".join([f"- {item}" for item in shopping_list])
return f"Current shopping list:\n{items_text}"
# Create a Shopping List Manager Agent that maintains state
agent = Agent(
model=OpenAIChat(id="gpt-4o-mini"),
# Initialize the session state with an empty shopping list
session_state={"shopping_list": []},
tools=[add_item, remove_item, list_items],
# You can use variables from the session state in the instructions
instructions=dedent("""\
Your job is to manage a shopping list.
The shopping list starts empty. You can add items, remove items by name, and list all items.
Current shopping list: {shopping_list}
"""),
show_tool_calls=True,
add_state_in_messages=True,
markdown=True,
)
# Example usage
agent.print_response("Add milk, eggs, and bread to the shopping list", stream=True)
print(f"Session state: {agent.session_state}")
agent.print_response("I got bread", stream=True)
print(f"Session state: {agent.session_state}")
agent.print_response("I need apples and oranges", stream=True)
print(f"Session state: {agent.session_state}")
agent.print_response("whats on my list?", stream=True)
print(f"Session state: {agent.session_state}")
agent.print_response("Clear everything from my list and start over with just bananas and yogurt", stream=True)
print(f"Session state: {agent.session_state}")
We love how elegantly we can maintain and pass on state across multiple runs.
Using state in instructions
You can use variables from the session state in the instructions by setting add_state_in_messages=True.
Don’t use the f-string syntax in the instructions. Directly use the {key} syntax, Agno substitutes the values for you.
from textwrap import dedent
from agno.agent import Agent
from agno.models.openai import OpenAIChat
agent = Agent(
model=OpenAIChat(id="gpt-4o-mini"),
# Initialize the session state with a variable
session_state={"user_name": "John"},
# You can use variables from the session state in the instructions
instructions="Users name is {user_name}",
show_tool_calls=True,
add_state_in_messages=True,
markdown=True,
)
agent.print_response("What is my name?", stream=True)
Persisting state in database
session_state is part of the Agent session and is saved to the database after each run if a storage driver is provided.
Here’s an example of an Agent that maintains a shopping list and persists the state in a database. Run this script multiple times to see the state being persisted.
"""Run `pip install agno openai sqlalchemy` to install dependencies."""
from agno.agent import Agent
from agno.models.openai import OpenAIChat
from agno.storage.sqlite import SqliteStorage
# Define a tool that adds an item to the shopping list
def add_item(agent: Agent, item: str) -> str:
"""Add an item to the shopping list."""
if item not in agent.session_state["shopping_list"]:
agent.session_state["shopping_list"].append(item)
return f"The shopping list is now {agent.session_state['shopping_list']}"
agent = Agent(
model=OpenAIChat(id="gpt-4o-mini"),
# Fix the session id to continue the same session across execution cycles
session_id="fixed_id_for_demo",
# Initialize the session state with an empty shopping list
session_state={"shopping_list": []},
# Add a tool that adds an item to the shopping list
tools=[add_item],
# Store the session state in a SQLite database
storage=SqliteStorage(table_name="agent_sessions", db_file="tmp/data.db"),
# Add the current shopping list from the state in the instructions
instructions="Current shopping list is: {shopping_list}",
# Important: Set `add_state_in_messages=True`
# to make `{shopping_list}` available in the instructions
add_state_in_messages=True,
markdown=True,
)
# Example usage
agent.print_response("What's on my shopping list?", stream=True)
print(f"Session state: {agent.session_state}")
agent.print_response("Add milk, eggs, and bread", stream=True)
print(f"Session state: {agent.session_state}")
