Models

Features

Use any model with Letta Code

Letta Code is model-agnostic. Agents can use Claude, GPT, Gemini, or other supported models. Users can change an agent’s underlying model at any time, even mid-conversation.

Switching models

Use the /model command to switch models during a session:

> /model

This opens a model selector with two categories:

Supported - Pre-configured models with optimized settings
All Available - All models available on your account, including custom BYOK (Bring Your Own Key) models

letta/auto and letta/auto-fast are API-gated and only appear when available from your Letta API account.

Use Tab to switch categories, arrow keys to navigate, and j/k to change pages.

You can also specify a model when starting Letta Code:

letta --model gpt-5-codex
letta --model openai/gpt-5.4-mini
letta --model chatgpt-plus-pro/gpt-5.4-mini
letta --model minimax/MiniMax-M2.7
letta -m haiku

Reasoning tiers

Use /reasoning to control model thinking effort.

Anthropic Sonnet 4.6 and Opus 4.6 support the max (xhigh) tier
Opus 4.5 supports none/low/medium/high tiers
Available tiers vary by model and are filtered automatically in the selector

Toolsets

Different models are trained to work best with different tools. For example, GPT-5 models are trained to use a patch-based editing tool, while Claude models work better with string-based edit tools.

Letta Code handles this automatically with toolsets - optimized tool configurations for each model family. When you switch models with /model, Letta Code automatically switches to the optimal toolset.

Toolset	Optimized for
Default	Claude models (Anthropic)
Codex	GPT models (OpenAI)
Gemini	Google models

Default toolset (Claude)

The default toolset is optimized for Anthropic models (Claude Sonnet, Opus, Haiku).

Category	Tools
File editing	`Edit` (string-replace), `Write`
File reading	`Read`, `Glob`
Shell	`Bash`
Search	`Grep` (ripgrep-based)
Planning	`EnterPlanMode`, `ExitPlanMode`, `TodoWrite`
Agent features	`Task` (subagents), `Skill` (invoke skills), `AskUserQuestion`, `memory`

Codex toolset (OpenAI)

The Codex toolset is optimized for OpenAI models (GPT-5, GPT-5-Codex, GPT-5.4 Mini, GPT-5.4 Nano). Uses patch-based editing instead of string-replace.

Category	Tools
File editing	`ApplyPatch` (unified patch-based edit and write)
File reading	`ReadFile`, `ListDir`, `view_image`
Shell	`ShellCommand`, `Shell`
Search	`GrepFiles`
Planning	`EnterPlanMode`, `ExitPlanMode`, `UpdatePlan`
Agent features	`Task` (subagents), `Skill` (invoke skills), `AskUserQuestion`, `memory`, `memory_apply_patch`

Gemini toolset (Google)

The Gemini toolset is optimized for Google models (Gemini Pro, Flash).

Category	Tools
File editing	`Replace` (string-replace), `WriteFileGemini`
File reading	`ReadFileGemini`, `ReadManyFiles`, `ListDirectory`, `GlobGemini`
Shell	`RunShellCommand`
Search	`SearchFileContent`
Planning	`EnterPlanMode`, `ExitPlanMode`, `WriteTodos`
Agent features	`Task` (subagents), `Skill` (invoke skills), `AskUserQuestion`, `memory`

Memory tools

In addition to the client-side tools above, Letta Code also exposes model-specific memory editing tools for maintaining memory blocks:

Claude and Gemini models: memory - an omni-tool with subcommands like create, view, str_replace, insert, delete, rename, and description updates
OpenAI/Codex models: memory_apply_patch - patch-based memory editing for memory files, alongside memory where supported

When you switch models with /model, Letta Code keeps the memory editing path aligned with the active toolset.

Manual toolset override

If you want to force a specific toolset:

letta --toolset codex

> /toolset