What is the difference between stateful and stateless agents?

A stateful agent keeps relevant information from earlier steps or interactions and uses it later.

A stateless agent treats each request or execution independently unless the required context is provided again.

The key difference is whether the agent itself carries forward task context.

Stateful agent

A stateful agent maintains information as a task progresses.

For example, suppose an agent is investigating a delayed order.

After several steps, its state might contain:

• payment confirmed
• inventory unavailable
• restock date found
• final explanation still pending

The next step can use this information directly.

The agent does not need to repeat earlier checks because the results are already available in state.

Stateless agent

A stateless agent does not automatically retain information from a previous request or execution.

Each request must contain the information needed to complete that request.

For example, if a stateless service receives:

> Check order status for A1045.

it processes that request and returns the result.

If another request arrives later, the service does not automatically know what happened before unless the required context is supplied again.

Example

Imagine a multi-step support task.

A stateful agent may work like this:

Step 1: Check payment → store result Step 2: Check inventory → use payment result plus new result Step 3: Check shipping → use all relevant previous results Step 4: Return final explanation

A stateless agent would need the necessary earlier context to be passed into each new request.

For example:

Request: Using payment=confirmed and inventory=out-of-stock, determine the next action.

The agent can still make the correct decision, but the state is being supplied externally rather than maintained by the agent itself.

Stateful does not necessarily mean long-term memory

A stateful agent may keep information only for the duration of one task.

For example, it might remember several tool results during a single execution and then discard them when the task ends.

Long-term memory is a separate capability.

State usually describes the information needed to continue the current execution.

Stateless does not mean context-free

A stateless agent can still receive a large amount of context.

The difference is that the context must be provided as part of the current request.

For example, an application could store task state in a database and send the relevant information to a stateless agent every time it is invoked.

In that architecture, the agent call is stateless even though the overall application maintains state.

Advantages of stateful agents

Stateful agents are useful for:

• multi-step tasks
• long-running workflows
• tasks with dependencies
• avoiding repeated work
• recovering from interruptions
• tracking task progress

They can naturally build on earlier results.

Advantages of stateless agents

Stateless designs can be useful because they are often:

• simpler to scale
• easier to retry
• easier to reproduce
• less dependent on local execution history

They work well when each request is self-contained or when state is managed by another system.

Which approach should be used?

It depends on the task and architecture.

Use stateful behavior when later decisions depend strongly on earlier results.

Use stateless behavior when each request can be handled independently or when another component is responsible for storing and supplying all required context.

Many production systems combine both approaches:

• persistent state is stored externally
• individual model or worker calls remain stateless
• the orchestration layer reconstructs the necessary context for each step

In short

A stateful agent carries relevant task context across steps or interactions, while a stateless agent processes each request independently unless earlier context is supplied again.

The difference is not simply whether information exists, but where that information is maintained and how it is made available to the next step.