Borrowing it
Nothing to install: this file belongs to radimsem/mithril. 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/radimsem/mithril/main/CLAUDE.mdgit clone --depth 1 https://github.com/radimsem/mithrilWrote 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/radimsem/mithril/claude-md)<a href="https://agentmods.dev/instructions/radimsem/mithril/claude-md"><img src="https://agentmods.dev/badge/instructions/radimsem/mithril/claude-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/radimsem/mithril/claude-md"><img src="https://agentmods.dev/badge/instructions/radimsem/mithril/claude-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 | $0.01709 | $0.01709 |
| Opus 5.5 | $0.00684 | $0.00684 |
| Sonnet 5.5 | $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 2mo 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.
- 2mo 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 (15 stars, last pushed 6mo ago), licensed Apache-2.0. It adds 1,709 tokens to every session, about $0.0068 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.
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