vocabulary: "0.1" name: letta-vocabulary title: Letta Vocabulary description: >- Domain vocabulary for Letta — the stateful AI agents platform (formerly MemGPT). Captures the canonical nouns, verbs, classifications, and operational dimensions used across the Letta API, ADE (Agent Development Environment), Letta Code, and the open-source Letta server. source: openapi: openapi/letta-openapi.json docs: https://docs.letta.com/ github: https://github.com/letta-ai/letta modified: "2026-05-22" # --- Core nouns (Letta domain entities) --- entities: - id: agent label: Agent definition: >- A stateful AI agent with persistent memory, tools, and a deterministic step-loop. Every conversation, tool call, and memory edit is anchored to a specific agent record. schema: json-schema/letta-agent-schema.json synonyms: [MemGPT agent, stateful agent] - id: block label: Memory Block definition: >- A labeled, character-limited chunk of in-context "core" memory (e.g., `persona`, `human`). Blocks are first-class objects and can be shared across agents to coordinate multi-agent state. schema: json-schema/letta-block-schema.json - id: archive label: Archive definition: >- A long-term archival memory store. Agents read/write Passages here when core memory is too small. Powers RAG-style recall over historical conversations and ingested Sources. schema: json-schema/letta-archive-schema.json - id: passage label: Passage definition: >- An individual chunk of archival memory — a vector-indexed snippet retrievable by semantic search. schema: json-schema/letta-passage-schema.json - id: source label: Source definition: >- A document ingestion surface (file, URL, dataset). Uploaded files are chunked into Passages and attached to agent archives for RAG. schema: json-schema/letta-source-schema.json - id: tool label: Tool definition: >- A callable function an agent can invoke. Three execution modes — `sandboxed` (Letta-hosted Python), `client-side` (your app executes), and `MCP` (delegated to a registered MCP server). schema: json-schema/letta-tool-schema.json - id: mcp_server label: MCP Server definition: >- A registered external Model Context Protocol server. Letta consumes its tools and lets agents invoke them as first-class tools without owning the execution. transports: [streamable_http, sse, stdio] - id: group label: Group definition: >- A multi-agent collective. Manager configs include `supervisor`, `round_robin`, `dynamic`, and `sleep_time`. Groups can share memory blocks for collective state. schema: json-schema/letta-group-schema.json - id: identity label: Identity definition: >- A mapping between an external end-user and per-user agents and memory contexts. Lets one Letta deployment serve many distinct users with isolated state. schema: json-schema/letta-identity-schema.json - id: run label: Run definition: >- One agent execution — the trace from a user message through tool calls, memory edits, and the final assistant reply. Bounded by step count and token usage. schema: json-schema/letta-run-schema.json - id: job label: Job definition: >- A long-running background task (e.g., source file ingestion, agent export). schema: json-schema/letta-job-schema.json - id: message label: Message definition: >- A single utterance — user, assistant, system, reasoning, tool_call, or tool_return — inside a run or conversation history. schema: json-schema/letta-message-schema.json message_types: [user_message, assistant_message, reasoning_message, tool_call_message, tool_return_message, system_message] - id: scheduled_message label: Scheduled Message definition: >- A one-time or cron-recurring message that drives an agent at a future time without a human in the loop. - id: llm_config label: LLM Config definition: >- Per-agent language model selection — endpoint type, model name, context window, temperature, max tokens. schema: json-schema/letta-llm-config-schema.json - id: embedding_config label: Embedding Config definition: >- Per-agent embedding model selection — dimensionality and endpoint. schema: json-schema/letta-embedding-config-schema.json - id: provider label: Provider definition: >- An LLM provider credential record — OpenAI, Anthropic, Azure, Google AI, Ollama, vLLM, etc. Letta routes model calls through these. schema: json-schema/letta-provider-schema.json # --- Concepts (Letta-specific patterns) --- concepts: - id: stateful_agent label: Stateful Agent definition: >- An agent whose identity persists across runs — its memory, tools, and configuration outlive any single LLM context window. Differentiator vs. stateless agent frameworks. - id: sleep_time_agent label: Sleep-Time Agent definition: >- A background agent that shares memory with primary agents and runs asynchronously to clean, consolidate, and rewrite their memory. Enabled via `enable_sleeptime: true`. - id: memgpt label: MemGPT definition: >- The original 2023 academic paper / project that introduced virtual-context-management for LLM agents. Letta is the production framework that grew out of MemGPT. - id: agent_file label: Agent File (.af) definition: >- Open file format for serializing a stateful agent (memory + tools + config) for export, sharing, version control, and migration between self-hosted and cloud. Repo: github.com/letta-ai/agent-file. - id: ade label: Agent Development Environment (ADE) definition: >- Letta's web UI for inspecting an agent's context window, memory blocks, archival memory, tool calls, and run history — "the ADE bridges the gap between development and deployment, providing complete transparency, state control, rapid prototyping, and robust debugging." - id: letta_code label: Letta Code definition: >- Letta's memory-first coding agent (CLI + desktop app) — analogous to Claude Code but with persistent agent memory and skill learning. - id: continual_learning label: Continual Learning definition: >- Letta's framing for agents that improve over time by rewriting their own memory and adding learned skills, rather than being fine-tuned. - id: context_constitution label: Context Constitution definition: >- A Letta primitive (Apr 2026) defining invariants and policies the agent must respect when editing its own memory and context. - id: skills label: Skills definition: >- Reusable agent capabilities packaged for sharing across Letta Code, Claude Code, Codex CLI, and other agents. Repo: github.com/letta-ai/skills. # --- Operational dimensions --- dimensions: deployment: - cloud - self_hosted pricing_meters: - per_active_agent_per_month - per_second_tool_execution - llm_passthrough_tokens manager_types: - supervisor - round_robin - dynamic - sleep_time agent_types: - memgpt_agent - split_thread_agent - sleeptime_agent - workflow_agent mcp_transports: - streamable_http - sse - stdio run_statuses: - queued - running - completed - failed - cancelled # --- Cross-reference vocabularies --- crossReferences: - vocab: schema.org mappings: Agent: schema:SoftwareApplication Tool: schema:Action Source: schema:DataDownload Message: schema:Message - vocab: Naftiko mappings: capability: capabilities/letta-*.yaml mcpServer: letta:MCPServer