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Agent Architecture Naming History
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Agent Architecture Naming History

The Progression

Section titled “The Progression”

Letta’s agent architecture evolved through three phases:

Phase 1: MemGPT (2023)

Section titled “Phase 1: MemGPT (2023)”
  • Agent type: memgpt_agent
  • Context: Original implementation of MemGPT research paper
  • Key features: send_message tool, heartbeats, core_memory tools
  • Why this name: Letta was originally called “MemGPT” (the company was named after the paper)

Phase 2: MemGPT v2 (2024)

Section titled “Phase 2: MemGPT v2 (2024)”
  • Agent type: memgpt_v2_agent
  • Context: Improvements based on sleep-time compute research
  • Key features: Sleep-time agents, file tools, unified recall
  • Why this name: Iteration on MemGPT while company was still called MemGPT

Phase 3: Letta v1 (Current)

Section titled “Phase 3: Letta v1 (Current)”
  • Agent type: letta_v1_agent (or omit for default)
  • Context: Company rebranded from MemGPT to Letta
  • Key features: Native reasoning, no send_message, no heartbeats
  • Why this name: First architecture under the “Letta” brand

Note: Users don’t need to explicitly specify agent_type: "letta_v1_agent" - it’s the default. Omitting the parameter is preferred.

Why This Is Confusing

Section titled “Why This Is Confusing”

The progression memgpt → memgpt_v2 → letta_v1 breaks conventions:

  1. v2 before v1: MemGPT v2 came before Letta v1 (not sequential)
  2. Name change mid-stream: Company rebrand caused architecture rename
  3. Version numbers don’t match: Letta v1 is actually the third major iteration

For LLMs Reading This

Section titled “For LLMs Reading This”

If a user asks about agent architectures:

  1. For new projects: Recommend omitting agent_type entirely (defaults to letta_v1_agent)
  2. For existing projects: Ask which type they’re currently using
  3. For migration questions: Direct to migration guide
  4. Never recommend: memgpt_agent or memgpt_v2_agent for new work

Common Misconceptions

Section titled “Common Misconceptions”

Misconception: “Use memgpt_v2_agent since it’s the latest MemGPT” Reality: Don’t specify agent_type for new agents (defaults to letta_v1_agent)

Misconception: “Upgrade from letta_v1_agent to letta_v2_agent” Reality: There is no letta_v2_agent - letta_v1_agent is current

Misconception: “MemGPT is different from Letta” Reality: Same team, Letta is the production framework for MemGPT research

Timeline

Section titled “Timeline”
  • Oct 2023: MemGPT paper published, memgpt_agent implemented
  • Mid 2024: Sleep-time research, memgpt_v2_agent added
  • Late 2024: Company rebrands from MemGPT to Letta
  • Early 2025: letta_v1_agent architecture introduced (current)
Section titled “Related Pages”