Stateful agents

The definition

Agent runtimes and frameworks that carry state across steps and tool calls within a task. Necessary for continuity but mostly scoped to a task or thread — distinct from state that survives a handoff to another agent, tool, or person.

The same words the glossary hub and the public data mirror carry; this page is the stable address for the term.

Related terms

• Agent

  Software that uses tools to carry out tasks and workflows — not just replying, but acting: calling APIs, running steps, making changes. Distinct from a…

• State

  The current condition of a user, workflow, task, or process — what persists between steps and sessions. Distinct from governed state, which adds provenance…

• Handoff

  The dated account one session, agent, or tenure leaves for the next: current state, decisions, unfinished work, and open questions. The successor verifies it…

Where it shows up on this site

• Letta memory · Letta (formerly MemGPT)A platform for stateful agents with editable memory blocks, archival memory and portable Agent Files, run as Letta Cloud or a self-hosted server. 6.5/8 on the memory systems tests.
• Honcho memory · Plastic LabsAn open-source memory server for stateful agents built around workspaces, peers and sessions, with background reasoning that builds user models; also offered as Honcho Cloud. 6.5/8 on the memory systems tests.
• Mistral AI · ActiveOpen-weight model family — stateful Agents API. Mistral AI publishes downloadable models alongside its hosted ones; its mistral-inference repository (now archived) lists models such as Mistral 7B, Mixtral 8x7B and 8x22B, Mistral Nemo and Mistral Small 3.1, and states that all the listed models support function calling. Licenses vary by model: the repository names custom non-commercial licenses for Codestral 22B and Mistral Large 2. On the hosted side, Mistral's Agents API, announced on 27 May 2025, keeps stateful conversations whose context and history persist across interactions, with built-in connectors for code execution, web search, image generation and MCP tools. That hosted history lives with Mistral, not in the open weights.