Agent File (.af)

Agent File (.af) is an open standard file format for serializing stateful agents. It provides a portable way to share agents with persistent memory and behavior across different environments.

You can import and export agents to and from any Letta Server (including both self-hosted servers and Letta Cloud) using the .af file format.

What is Agent File?

Agent Files package all components of a stateful agent:

• System prompts
• Editable memory (personality and user information)
• Tool configurations (code and schemas)
• LLM settings

By standardizing these elements in a single format, Agent File enables seamless transfer between compatible frameworks, while allowing for easy checkpointing and version control of agent state.

Why Use Agent File?

The AI ecosystem is experiencing rapid growth in agent development, with each framework implementing its own storage mechanisms. Agent File addresses the need for a standard that enables:

• Portability: Move agents between systems or deploy them to new environments
• Collaboration: Share your agents with other developers and the community
• Preservation: Archive agent configurations to preserve your work
• Versioning: Track changes to agents over time through a standardized format

What State Does .af Include?

A .af file contains all the state required to re-create the exact same agent:

Using Agent File with Letta

Importing Agents

You can import .af files using the Agent Development Environment (ADE), REST APIs, or developer SDKs.

Using ADE

Upload downloaded .af files directly through the ADE interface to easily re-create your agent.

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// Install SDK with `npm install @letta-ai/letta-client`
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import { LettaClient } from '@letta-ai/letta-client'
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import { readFileSync } from 'fs';
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import { Blob } from 'buffer';
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// Assuming a Letta Server is running at http://localhost:8283
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const client = new LettaClient({ baseUrl: "http://localhost:8283" });
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// Import your .af file from any location
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const file = new Blob([readFileSync('/path/to/agent/file.af')])
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const agentState = await client.agents.importAgentSerialized(file, {})
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console.log(`Imported agent: ${agentState.id}`);

Exporting Agents

You can export your own .af files to share by selecting “Export Agent” in the ADE.

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// Install SDK with `npm install @letta-ai/letta-client`
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import { LettaClient } from '@letta-ai/letta-client'
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// Assuming a Letta Server is running at http://localhost:8283
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const client = new LettaClient({ baseUrl: "http://localhost:8283" });
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// Export your agent into a serialized schema object (which you can write to a file)
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const schema = await client.agents.exportAgentSerialized("<AGENT_ID>");

FAQ

Does .af work with frameworks other than Letta?

Theoretically, other frameworks could also load in .af files if they convert the state into their own representations. Some concepts, such as context window “blocks” which can be edited or shared between agents, are not implemented in other frameworks, so may need to be adapted per-framework.

How does .af handle secrets?

Agents have associated secrets for tool execution in Letta. When you export agents with secrets, the secrets are set to null for security reasons.

Contributing to Agent File

The Agent File format is a community-driven standard that welcomes contributions:

• Share Example Agents: Contribute your own .af files to the community
• Join the Discussion: Connect with other agent developers in our Discord server
• Provide Feedback: Offer suggestions and feature requests to help refine the format

For more information on Agent File, including example agents and the complete schema specification, visit the Agent File repository.