Leon is an open-source personal AI assistant that uses tools, memory, context, and agent-like execution to understand goals and complete tasks. People use it as a practical assistant that can run locally and work across structured workflows, while the catalogue skills support its operation.
Borrowing it
Nothing to install: this file belongs to leon-ai/leon. 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/leon-ai/leon/develop/AGENTS.mdgit clone --depth 1 https://github.com/leon-ai/leonWrote 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/leon-ai/leon/agents-md)<a href="https://agentmods.dev/instructions/leon-ai/leon/agents-md"><img src="https://agentmods.dev/badge/instructions/leon-ai/leon/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/leon-ai/leon/agents-md"><img src="https://agentmods.dev/badge/instructions/leon-ai/leon/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 | $0.01838 | $0.01838 |
| Opus 5.5 | $0.00735 | $0.00735 |
| Sonnet 5.5 | $0.00368 | $0.00368 |
| Haiku 4.5 | $0.00184 | $0.00184 |
Grade A, and why
leon 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 5d ago.
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 — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Working on Leon AI
Read ARCHITECTURE.md for runtime boundaries and LEON.md for intended behavior. Verify the relevant source before changing a subsystem; these context files are generated summaries.
Workflow
- For a new goal, inspect the existing implementation and confirm the plan with the owner before changing code.
- Use
pnpm, never npm. Keep changes minimal; reuse existing SDK facilities andserver/src/helpers/before adding abstractions. Remove superseded logic rather than maintaining parallel implementations. - Preserve unrelated working-tree changes and profile isolation. Use existing profile/path/runtime utilities instead of hardcoded owner paths, runtime versions, or global mutable owner state.
- Run
pnpm lint, fix warnings/errors, and run checks relevant to the change. - Test current behavior with minimal coverage; extend existing suites. Trivial changes need no new tests.
- Do not create test files or add test cases for SDKs, tools or skills unless the owner explicitly requests them, regardless of where the tests would live. Run existing affected tests and adjust them for compatibility when necessary.
- Review only affected tests. Retain unique runtime contracts regardless of bug-fix origin; remove obsolete or duplicate reproductions.
- Use
pnpm test:unitfor fast feedback andpnpm test:integrationfor real worker, download, capture, and rendering changes;pnpm testincludes both. - Agent e2e tests must use
pnpm test:agent:e2e -- -t openaiunless the owner explicitly requests other providers. - Suggest a commit message matching
scripts/commit-msg.js; do not commit unless asked.
Setup migrations
- Keep migration implementations self-contained under
scripts/setup/migrations/. Do not introduce shared migration helpers or import another migration's implementation. - Name migrations
YYYYMMDDHHmmssSS-description.jsusing UTC, a fixed-width 16-digit timestamp, and a lowercase kebab-case description.SSis hundredths of a second. Generate the timestamp withdate -u +%Y%m%d%H%M%S%2N; never use local time. - The setup runner executes pending migrations from oldest to newest filename timestamp and records completion separately for each profile. Export a default
async migrate(profilePaths)function and make it safe to retry after interruption. - Preserve published migration filenames. If a rename is necessary, export the former filenames in
previousIdsso completed work is recognized without running it again.
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.
- 5d ago Changed · +7 lines · +173 tokens per session ae334be60cd7
- 7d ago Changed · +12 lines · +432 tokens per session 76cb950985b8
- 9d ago Changed · -7 tokens per session 30f4b4586d7d
- 10d ago Changed · -69 tokens per session 63a57bbdb30f
- 12d ago Changed · +1 lines · +65 tokens per session 92824ddafdec
- 15d ago Changed · +2 lines · +100 tokens per session dc47cd5c5414
- 16d ago Changed · +2 lines · +108 tokens per session 7d7c4e0c2fb8
- 29d ago Changed · +1 lines · +40 tokens per session 2d88e14b8879
- 1mo ago First seen · 52 lines · 996 tokens per session scan A 835146c4c36c
leon AGENTS.md is an instructions file published in the GitHub repository leon-ai/leon (17,579 stars, last pushed 4d ago), licensed MIT. It adds 1,838 tokens to every session, about $0.0074 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 2026-09-10.
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.
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.
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).