Borrowing it
Nothing to install: this file belongs to ThirdKeyAI/Symbiont. 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/ThirdKeyAI/Symbiont/main/AGENTS.mdgit clone --depth 1 https://github.com/ThirdKeyAI/SymbiontWrote 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/thirdkeyai/symbiont/agents-md)<a href="https://agentmods.dev/instructions/thirdkeyai/symbiont/agents-md"><img src="https://agentmods.dev/badge/instructions/thirdkeyai/symbiont/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/thirdkeyai/symbiont/agents-md"><img src="https://agentmods.dev/badge/instructions/thirdkeyai/symbiont/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 | $0.06547 | $0.06547 |
| Opus 5.5 | $0.02619 | $0.02619 |
| Sonnet 5.5 | $0.01309 | $0.01309 |
| Haiku 4.5 | $0.00655 | $0.00655 |
Grade A, and why
Symbiont 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 2d 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 — 465 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Symbiont — Agent Instructions
Symbiont (Symbi) is a Rust-native, zero-trust agent framework for building autonomous, policy-aware AI agents. Part of the ThirdKey trust stack: SchemaPin → AgentPin → Symbiont.
- Docs: https://docs.symbiont.dev
- Repo: https://github.com/ThirdKeyAI/Symbiont
- Crate: https://crates.io/crates/symbi
Project Structure
crates/
├── dsl/ # Symbi DSL parser with Tree-sitter integration
├── runtime/ # Agent runtime (scheduling, routing, sandbox, AgentPin)
├── channel-adapter/ # Slack, Teams, Mattermost adapters
├── repl-core/ # Core REPL engine
├── repl-proto/ # JSON-RPC wire protocol types
├── repl-cli/ # Command-line REPL interface
├── repl-lsp/ # Language Server Protocol implementation
src/ # Unified `symbi` CLI binary
Build and Test
cargo build --workspace
cargo test --workspace
cargo clippy --workspace
cargo fmt --check
All four commands must pass before committing. Clippy must produce zero warnings.
Code Style
- Rust edition 2021
- Run
cargo fmtbefore committing - Run
cargo clippy --workspaceand fix all warnings before committing - Inline tests in source files using
#[cfg(test)] mod tests - ES256 (ECDSA P-256) only for AgentPin identity — reject all other algorithms
- Agent files use
.symbi(canonical) —.dslis supported indefinitely for backward compatibility. Usedsl::is_symbi_file/dsl::strip_symbi_extensionfor file discovery instead of inlining extension checks. New scaffolding emits.symbionly.
Commit Guidelines
- Write concise commit messages focused on the "why"
- No mention of AI assistants or co-authoring in commit messages
- Use
datecommand to determine the current date when adding dates to docs
Local models
symbi run and symbi up accept any OpenAI-compatible endpoint, so a local
model works with no cloud key:
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.
- 2d ago Changed · +7 lines · +285 tokens per session 631865b741d1
- 19d ago Changed · +44 lines · +687 tokens per session 33a7f73c6590
- 1mo ago Changed · +100 lines · +1,324 tokens per session 6cafbe51b0de
- 1mo ago Changed · +22 lines · +212 tokens per session 3c8fcd84151e
- 1mo ago First seen · 292 lines · 4,039 tokens per session scan A 7e8b437a9be2
Symbiont AGENTS.md is an instructions file published in the GitHub repository ThirdKeyAI/Symbiont (56 stars, last pushed 2d ago), licensed Apache-2.0. It adds 6,547 tokens to every session, about $0.0262 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).
deno copilot-instructions.md
Copilot instructions for denoland/deno, covering deno development guide for github copilot, network access, high level overview, key directories and key files to understand first.