letta [options] [-p "prompt" ]
Flag Description lettaStart interactive session (resumes last used agent, or creates new) letta --newForce create a new agent letta --from-af <path>Create new agent from an AgentFile (.af) letta --agent <id>Use a specific agent by ID letta --name <name>, -nResume agent by name (matches pinned or recent agents) letta --infoShow project info, skills directory, and pinned agents (without starting session) letta --helpShow help letta --versionShow version
Flag Description --model <model>, -mSpecify model (e.g., sonnet-4.5, gpt-5-codex) --system <preset>Use a system prompt preset (e.g., letta-claude, codex) --system-custom <text>Use a custom system prompt string (for new agents) --system-append <text>Append text to the resolved system prompt (for new agents) --toolset <name>Force toolset: default, codex, or gemini --skills <path>Custom skills directory --sleeptimeEnable sleeptime memory management (only for new agents)
The --model flag can be inconsistent when resuming sessions. Use the /model command instead to change models during an interactive session.
Note: When connecting to an existing agent with --agent <id>, the agent’s existing configuration (model, toolset) is preserved. Use /model or /toolset to change them during the session.
Run Letta Code non-interactively for automation and CI/CD. See Headless mode for detailed usage.
Flag Description -p "prompt"Run a one-off prompt (headless mode) --output-format <fmt>Output format: text, json, or stream-json --input-format <fmt>Input format: stream-json for bidirectional mode --yoloBypass all permission prompts --permission-mode <mode>Set permission mode --tools "Tool1,Tool2"Limit available tools --allowedTools "..."Allow specific tool patterns --disallowedTools "..."Block specific tool patterns
Configure memory blocks when creating new agents.
Flag Description --init-blocks <names>Comma-separated preset block names (e.g., "persona,project") --memory-blocks <json>JSON array of custom memory blocks --block-value <label>=<value>Set value for a preset block (can be specified multiple times)
Flag Description letta updateManually check and install updates
Variable Description LETTA_API_KEYAPI key for authentication (get yours at app.letta.com/api-keys ) LETTA_BASE_URLBase URL for self-hosted Letta server (e.g., http://localhost:8283) LETTA_DEBUGSet to 1 to enable debug logging LETTA_CODE_TELEMSet to 0 to disable anonymous telemetry DISABLE_AUTOUPDATERSet to 1 to disable auto-updates
Set these in your shell profile (~/.bashrc, ~/.zshrc) or .env file:
export LETTA_API_KEY = "your-key-here"
export LETTA_BASE_URL = "http://localhost:8283"
These shortcuts work during interactive sessions.
Shortcut Description /Open command autocomplete @Open file autocomplete !Enter bash mode (run shell commands directly) TabAutocomplete command or file path Shift+EnterInsert newline (multi-line input) ↑ / ↓Navigate history or menu items EscCancel dialog or clear input (double press) Ctrl+CInterrupt operation or exit (double press) Ctrl+VPaste content or image
Bash mode lets you run shell commands directly without involving the agent. Press ! on an empty input line to enter bash mode (prompt changes to !), type your command, and press Enter. Press Backspace on an empty line to exit bash mode.
