AI agent memory

Important

Memory allows AI agents to remember information from earlier in the conversation or from previous conversations. This lets agents provide context-aware responses and build personalized experiences over time. Use Databricks Lakebase, a fully-managed Postgres OLTP database, to manage conversation state and history.

Requirements

A Lakebase instance, see Create and manage a database instance.

Short-term vs. long-term memory

Short-term memory captures context in a single conversation session while long-term memory extracts and stores key information across multiple conversations. You can build your agent with either or both types of memory.

Agents with short-term and long-term memory

Short-term memory	Long-term memory
Capture context in a single conversation session using thread IDs and checkpointing Maintain context for follow-up questions within a session Debug and test conversation flows using time travel	Automatically extract and store key insights across multiple sessions Personalize interactions based on past preferences Build a knowledge base about users that improves responses over time

Notebook examples

Agent with short-term memory

Get notebook

Agent with long-term memory

Get notebook

Query your deployed agent

After you deploy your agent to a Model Serving endpoint, see Query a deployed Mosaic AI agent for query instructions.

To pass in a thread id, use the extra_body param. The following example shows you how to pass in a thread ID to a ResponsesAgent endpoint:

   response1 = client.responses.create(
    model=endpoint,
    input=[{"role": "user", "content": "What are stateful agents?"}],
    extra_body={
        "custom_inputs": {"thread_id": thread_id}
    }
)

If you are using a client that automatically passes ChatContext like the Playground or Review app, the conversation id and user id will automatically be passed in for short-term/long-term memory use cases.

Short-term memory time travel

For agents with short-term memory, use LangGraph time-travel to resume execution from checkpoints. You can either replay the conversation or modify it to explore alternative paths. Each time you resume from a checkpoint, LangGraph creates a new fork in the conversation history, preserving the original while enabling experimentation.

In agent code, create functions that retrieve checkpoint history and update checkpoint state in the LangGraphResponsesAgent class:

from typing import List, Dict
def get_checkpoint_history(self, thread_id: str, limit: int = 10) -> List[Dict[str, Any]]:
    """Retrieve checkpoint history for a thread.

    Args:
        thread_id: The thread identifier
        limit: Maximum number of checkpoints to return

    Returns:
        List of checkpoint information including checkpoint_id, timestamp, and next nodes
    """
    config = {"configurable": {"thread_id": thread_id}}

   with CheckpointSaver(instance_name=LAKEBASE_INSTANCE_NAME) as checkpointer:
        graph = self._create_graph(checkpointer)

        history = []
        for state in graph.get_state_history(config):
            if len(history) >= limit:
                break

            history.append({
                "checkpoint_id": state.config["configurable"]["checkpoint_id"],
                "thread_id": thread_id,
                "timestamp": state.created_at,
                "next_nodes": state.next,
                "message_count": len(state.values.get("messages", [])),
                # Include last message summary for context
                "last_message": self._get_last_message_summary(state.values.get("messages", []))
            })

        return history

def _get_last_message_summary(self, messages: List[Any]) -> Optional[str]:
    """Get a snippet of the last message for checkpoint identification"""
    return getattr(messages[-1], "content", "")[:100] if messages else None

def update_checkpoint_state(self, thread_id: str, checkpoint_id: str,
                        new_messages: Optional[List[Dict]] = None) -> Dict[str, Any]:
    """Update state at a specific checkpoint (used for modifying conversation history).

    Args:
        thread_id: The thread identifier
        checkpoint_id: The checkpoint to update
        new_messages: Optional new messages to set at this checkpoint

    Returns:
        New checkpoint configuration including the new checkpoint_id
    """
    config = {
        "configurable": {
            "thread_id": thread_id,
            "checkpoint_id": checkpoint_id
        }
    }

    with CheckpointSaver(instance_name=LAKEBASE_INSTANCE_NAME) as checkpointer:
        graph = self._create_graph(checkpointer)

        # Prepare the values to update
        values = {}
        if new_messages:
            cc_msgs = self.prep_msgs_for_cc_llm(new_messages)
            values["messages"] = cc_msgs

        # Update the state (creates a new checkpoint)
        new_config = graph.update_state(config, values=values)

        return {
            "thread_id": thread_id,
            "checkpoint_id": new_config["configurable"]["checkpoint_id"],
            "parent_checkpoint_id": checkpoint_id
        }

Update the predict and predict_stream functions to support passing in checkpoints:

Predict

def predict(self, request: ResponsesAgentRequest) -> ResponsesAgentResponse:
    """Non-streaming prediction"""
    # The same thread_id is used by BOTH predict() and predict_stream()
    ci = dict(request.custom_inputs or {})
    if "thread_id" not in ci:
        ci["thread_id"] = str(uuid.uuid4())
    request.custom_inputs = ci

    outputs = [
        event.item
        for event in self.predict_stream(request)
        if event.type == "response.output_item.done"
    ]

    # Include thread_id and checkpoint_id in custom outputs
    custom_outputs = {
        "thread_id": ci["thread_id"]
    }
    if "checkpoint_id" in ci:
        custom_outputs["parent_checkpoint_id"] = ci["checkpoint_id"]

    try:
        history = self.get_checkpoint_history(ci["thread_id"], limit=1)
        if history:
            custom_outputs["checkpoint_id"] = history[0]["checkpoint_id"]
    except Exception as e:
        logger.warning(f"Could not retrieve new checkpoint_id: {e}")

    return ResponsesAgentResponse(output=outputs, custom_outputs=custom_outputs)

Predict_stream

def predict_stream(
    self,
    request: ResponsesAgentRequest,
) -> Generator[ResponsesAgentStreamEvent, None, None]:
    """Streaming prediction with PostgreSQL checkpoint branching support.

    Accepts in custom_inputs:
    - thread_id: Conversation thread identifier for session
    - checkpoint_id (optional): Checkpoint to resume from (for branching)
    """
    # Get thread ID and checkpoint ID from custom inputs
    custom_inputs = request.custom_inputs or {}
    thread_id = custom_inputs.get("thread_id", str(uuid.uuid4()))  # generate new thread ID if one is not passed in
    checkpoint_id = custom_inputs.get("checkpoint_id")  # Optional for branching

    # Convert incoming Responses messages to LangChain format
    langchain_msgs = self.prep_msgs_for_cc_llm([i.model_dump() for i in request.input])

    # Build checkpoint configuration
    checkpoint_config = {"configurable": {"thread_id": thread_id}}
    # If checkpoint_id is provided, we're branching from that checkpoint
    if checkpoint_id:
        checkpoint_config["configurable"]["checkpoint_id"] = checkpoint_id
        logger.info(f"Branching from checkpoint: {checkpoint_id} in thread: {thread_id}")

    # DATABASE CONNECTION POOLING LOGIC FOLLOWS
    # Use connection from pool

Then, test your checkpoint branching:

Start a conversational thread and add a few messages:

from agent import AGENT
# Initial conversation - starts a new thread
response1 = AGENT.predict({
    "input": [{"role": "user", "content": "I'm planning for an upcoming trip!"}],
})
print(response1.model_dump(exclude_none=True))
thread_id = response1.custom_outputs["thread_id"]

# Within the same thread, ask a follow-up question - short-term memory will remember previous messages in the same thread/conversation session
response2 = AGENT.predict({
    "input": [{"role": "user", "content": "I'm headed to SF!"}],
    "custom_inputs": {"thread_id": thread_id}
})
print(response2.model_dump(exclude_none=True))

# Within the same thread, ask a follow-up question - short-term memory will remember previous messages in the same thread/conversation session
response3 = AGENT.predict({
    "input": [{"role": "user", "content": "Where did I say I'm going?"}],
    "custom_inputs": {"thread_id": thread_id}
})
print(response3.model_dump(exclude_none=True))

Retrieve checkpoint history and fork the conversation with a different message:

# Get checkpoint history to find branching point
history = AGENT.get_checkpoint_history(thread_id, 20)
# Retrieve checkpoint at index - indices count backward from most recent checkpoint
index = max(1, len(history) - 4)
branch_checkpoint = history[index]["checkpoint_id"]

# Branch from node with next_node = `('__start__',)` to re-input message to agent at certain part of conversation
# I want to update the information of which city I am going to
# Within the same thread, branch from a checkpoint and override it with different context to continue the conversation in a new fork
response4 = AGENT.predict({
    "input": [{"role": "user", "content": "I'm headed to New York!"}],
    "custom_inputs": {
        "thread_id": thread_id,
        "checkpoint_id": branch_checkpoint # Branch from this checkpoint!
    }
})
print(response4.model_dump(exclude_none=True))

# Thread ID stays the same even though it branched from a checkpoint:
branched_thread_id = response4.custom_outputs["thread_id"]
print(f"original thread id was {thread_id}")
print(f"new thread id after branching is the same as original: {branched_thread_id}")

# Continue the conversation in the same thread and it will pick up from the information you tell it in your branch
response5 = AGENT.predict({
    "input": [{"role": "user", "content": "Where am I going?"}],
    "custom_inputs": {
        "thread_id": thread_id,
    }
})
print(response5.model_dump(exclude_none=True))

Next steps

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Last updated on 2025-12-19