Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add instructions/radimsem/mithril/claude-mdgit clone --depth 1 https://github.com/radimsem/mithrilWhat 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 | $0.01709 | $0.01709 |
| Opus 5 | $0.00855 | $0.00855 |
| Sonnet 5 | $0.00342 | $0.00342 |
| Haiku 4.5 | $0.00171 | $0.00171 |
Grade A, and why
mithril CLAUDE.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 3d 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 — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mithril
Sandboxed MCP server that replaces the generic shell tool with validated, purpose-built execution tools for AI agents. No shell, no escapes — every command goes through typed arguments, injection guards, path confinement, and OS-level isolation.
Quick Reference
cargo build # Build all crates
cargo build -p mithril # Binary only
cargo test # All non-ignored tests
cargo test -- --ignored # Include sandbox + ecosystem tests
cargo test -p server # Single crate
cargo test -p server cat_reads_file # Single test by name
cargo clippy --workspace # Lint
cargo fmt --all -- --check # Format check
Workspace Structure
crates/
bin/ CLI binary entry point (clap args, config loading, MCP transport)
common/ Shared types: Config, ExecContext, ToolDef/ToolExec traits, errors, validation rules
patterns/ Compiled regex patterns for validation (melody DSL, lazy_static)
tools/ ~160 tool implementations across 10 domains (system, git, docker, go, js, python, rust, gh, glab, run_chain)
server/ MCP ServerHandler, tool/prompt/resource routing, execution pipeline, history buffer
runner/ Process spawning layer: timeouts, stdout streaming, progress notifications
validator/ Argument validation layer: injection guard, path confinement, env blocklist, elicitation
sandbox/ OS isolation layer: BubbleWrap (Linux) / sandbox-exec (macOS) / Noop fallback
proxy/ Optional RTK (Rust Token Killer) prefix layer for token-optimized output
Architecture
Execution Pipeline
Every tool call flows through 4 sequential layers:
MCP Request → Router → build_context() → [ Validate → Proxy → Sandbox → Runner ] → format() → MCP Response
- ValidateLayer — checks argument types, string patterns, injection characters, path confinement, env blocklist, elicitation approval
- ProxyLayer — optionally prepends
rtkbinary for supported commands - SandboxLayer — prepends OS-specific sandbox command prefix (bwrap/sandbox-exec)
- RunnerLayer — spawns process via
tokio::process::Command, streams stdout, enforces timeout
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.
- 3d ago First seen · 135 lines · 1,709 tokens per session scan A 83b6a6245896
mithril CLAUDE.md is an instructions file published in the GitHub repository radimsem/mithril (16 stars, last pushed 4mo ago), licensed Apache-2.0. It adds 1,709 tokens to every session, about $0.0085 per session on Opus 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
dsh-TUI AGENTS.md
AGENTS.md instructions for ccch1mneyyy/dsh-TUI, covering agents.md, 仓库布局, 命令, 上游边界与契约 and 约定与红线.
golembot CLAUDE.md
Instructions for 0xranx/golembot, covering golembot — project conventions for claude code, architecture hard constraints, things you must never do, interface change rules and file responsibility boundaries.
sortie copilot-instructions.md
Instructions for sortie-ai/sortie, covering sortie coding & review standards, 1. layered imports (downward only; violation is critical), 2. concurrency safety, 3. workspace path safety (critical: security boundary) and 4. persistence (sqlite).
copperhead CLAUDE.md
Instructions for copperheadhq/copperhead, covering claude.md, what this repo is, sources of truth, workflow (openspec) and architecture (per spec.md §2).
pi-ask AGENTS.md
Instructions for eko24ive/pi-ask, covering agents.md, project scope, project goals, tech stack and commands.
amp-acp AGENTS.md
Instructions for tao12345666333/amp-acp, covering agents.md, commands, architecture and code style.