letta-ai/letta-code is an agent harness for building assistants that retain memory, identity, and experience across interactions instead of treating each task as isolated. Developers use it through local, desktop, browser, or messaging interfaces for interactive or continuously running agents, and its catalogue entries configure the agents' skills, instructions, rules, and behavior.
Borrowing it
Nothing to install: this file belongs to letta-ai/letta-code. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/letta-ai/letta-code/main/AGENTS.mdgit clone --depth 1 https://github.com/letta-ai/letta-codeWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/instructions/letta-ai/letta-code/agents-md)<a href="https://agentmods.dev/instructions/letta-ai/letta-code/agents-md"><img src="https://agentmods.dev/badge/instructions/letta-ai/letta-code/agents-md/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/letta-ai/letta-code/agents-md"><img src="https://agentmods.dev/badge/instructions/letta-ai/letta-code/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.11308 | $0.11308 |
| Opus 5.5 | $0.04523 | $0.04523 |
| Sonnet 5.5 | $0.02262 | $0.02262 |
| Haiku 4.5 | $0.01131 | $0.01131 |
Grade A, and why
letta-code AGENTS.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 974 lines — stays where its author put it; the contents beside it link to each section on GitHub.
letta-code — Agent Guide
This file explains how to work effectively in this repo. It covers the rules enforced by CI, why each rule exists, and the workflow conventions that keep the codebase healthy and agent-navigable.
Workflow
- Create a worktree for any non-trivial change — especially if another agent may be working concurrently.
- Make your change, then run
bun run checkand fix all failures before opening a PR. - One PR per logical change. Don't bundle unrelated changes — harder to revert if something breaks.
- Never amend commits. Always create a new commit.
- Check the current branch before editing files. If in doubt, ask.
Runtime Validation
Automated notifications use user-role reminders
Never inject role: "system" messages into conversation history for harness
notifications, recovery, teleport, onboarding, or mod instructions. Use
role: "user" with <system-reminder>...</system-reminder> content instead.
The tags identify automated context without requiring API-level system priority;
the existing transcript echo strips reminder-only content from user bubbles.
Anthropic can reject a system-role notification after an ordinary assistant
message, including when a later user message follows it. Keep tool results before
the reminder and preserve message IDs. This rule does not change the compiled
system prompt or explicit user-supplied provider/API message roles.
Development and distribution use different runtimes. bun run dev runs the
TypeScript source with Bun, while the published package exposes a Node-targeted
letta.js bundle and requires Node ^22.23.4, ^24.22.1, or ^26.12.1. When behavior depends on the
runtime, test both the Bun source path and the built Node artifact.
The interactive TUI, headless mode, and websocket listener also have separate
orchestration paths. Changes to shared turn, tool, approval, permission, or
transcript behavior must identify and run the focused tests for every affected
path. bun run check is always required, but it does not replace those behavior
tests.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- today Changed · +4 lines · +129 tokens per session 6a91aa51eea6
- 5d ago Changed · +30 tokens per session 6ccd79e2af07
- 13d ago Changed · +1 lines · +64 tokens per session b7798c979c88
- 1mo ago Changed · -1 tokens per session f634f199a029
- 1mo ago Changed · -1 lines · -22 tokens per session 7837a7a920f5
- 1mo ago Changed · +12 lines · +138 tokens per session 2e0a3ac12e94
- 1mo ago Changed · +10 lines · +138 tokens per session 73ce8de1902b
- 2mo ago First seen · 948 lines · 10,832 tokens per session scan A f1db6b58e260
letta-code AGENTS.md is an instructions file published in the GitHub repository letta-ai/letta-code (3,730 stars, last pushed today), licensed Apache-2.0. It adds 11,308 tokens to every session, about $0.0452 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deepseek-harness AGENTS.md
AGENTS.md instructions for deepseek-ai/deepseek-harness, covering agents.md, pre-stable apis and released session data, repository layout, commands and host sandbox failures.