Letta Code is an open-source coding-agent harness from the Letta team. It has a real local CLI, stores agent state locally by default, supports headless runs, and exposes a richer programmatic stream-json control mode for permissions and automation.
Key capabilities
Local CLI - Install with npm install -g @letta-ai/letta-code and run letta. Default local mode stores agent state on your machine and does not require login.
Headless mode - letta -p "..." supports text, JSON, stream-json output, and bidirectional stream-json control.
MCP and extensions - Letta Code includes /mcp, hooks, skills, subagents, and trusted local code extensions called mods under ~/.letta/mods/.
Memory-oriented design - Persistent agent state and memory are the core differentiators versus fresh-session coding CLIs.
Autonomy level
Level 3 (supervised agent): local coding workflow with richer programmatic control available for automation.
Strengths
- Open-source coding harness
- Runs without login using your own API keys or local models
- Persistent local state is useful for long-lived agent expertise
- MCP, hooks, skills, subagents, and mods give it a serious extension surface
Limitations
- Current CLI docs require Node.js 22.19+
- Older Node may silently install an older compatible Letta Code version
- One-shot headless excludes tools that need direct user responses; bidirectional mode is the control surface for those cases