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sheena: Instructions file for Claude Code

CLAUDE.md

sheena CLAUDE.md is an instructions file for Claude Code from goccy/sheena. It costs 900 tokens per session, scanned A, original, MIT.

Repository instructions for Sheena, a lightweight sandbox that safely runs AI-agent tool calls on the same computer. They define Go coding, testing, coverage, and benchmark rules.

In plain words
What is it for?
Use them when developing or reviewing the Sheena repository, especially when running tests, coverage checks, or benchmarks.
Why use it?
They give an agent clear project rules, including the required Go version and minimum test coverage, before it changes code.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md.

This is goccy/sheena's own configuration. It tells Claude Code how to work on sheena itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything sheena configures →

not rated 44repo 1mo ago A scan 900 tokens original MIT
View source ↗ goccy/sheena
Reuse

Borrowing it

Nothing to install: this file belongs to goccy/sheena. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/goccy/sheena/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/goccy/sheena

Made for: Claude Code.

Wrote 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.

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README.md
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Your own site
<a href="https://agentmods.dev/instructions/goccy/sheena/claude-md"><img src="https://agentmods.dev/badge/instructions/goccy/sheena/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.

agentmods 80×15 button for sheena CLAUDE.md

Your own site · 80×15
<a href="https://agentmods.dev/instructions/goccy/sheena/claude-md"><img src="https://agentmods.dev/badge/instructions/goccy/sheena/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 900 This file is loaded in full into every session.
When invoked 900 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00900 $0.00900
Opus 5.5 $0.00360 $0.00360
Sonnet 5.5 $0.00180 $0.00180
Haiku 4.5 $0.00090 $0.00090

Measured 2mo ago against content hash e39f1385de14, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

sheena 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.

CLAUDE.md · 74 lines

How it starts

The opening of the file, as written. The whole thing — 74 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sheena — Project Rules for Claude

Sheena is a lightweight, in-process sandbox for safely executing AI-agent tool calls on the same host as the agent. See DESIGN.md for the full design.

Development rules

These rules are mandatory for every change in this repository.

Go version & idioms

  • Target Go 1.25.0 as the base. Any feature available up to and including Go 1.25 may be used freely (generics, io/fs.ReadLinkFS, etc.).
  • Prefer modern idioms. Use any, never the legacy interface{} spelling. Use generics where they remove duplication or improve type safety instead of falling back to any + type assertions.
  • go.mod declares go 1.25.0; keep the golangci-lint run.go in sync.

Testing & coverage

  • Every package MUST maintain ≥90% statement coverage. Add unit tests until the threshold is met; do not lower the bar.
  • make test (runs go test -race ./...) and make cover (per-package ≥90% gate) MUST pass before a change is considered done. Both run in CI (see .github/workflows/ci.yml), alongside a separate make lint job.
  • Access-control behavior MUST be verified with Go example tests (Example… with // Output: blocks) — e.g. path traversal blocked, network denied by default, overlay never writes to the host. These both document the API and assert the security guarantees.
  • Keep dedicated security tests for escape attempts (../, symlink escape, absolute paths, SSRF to loopback/link-local, redirect crossing, memory bomb, command-count overflow, timeout).

Benchmarks

  • Sheena claims to be a lightweight sandbox: many instances, low per-call overhead. That claim MUST stay measured, not asserted.
  • Keep Benchmark… tests for: sandbox construction / mass startup (report allocs/op and B/op, not just ns/op), per-call ExecBash overhead on a trivial command, and parallel throughput (b.RunParallel).
  • Run with make bench (go test -run '^$' -bench . -benchmem ./...). When a change may affect hot paths, compare before/after with benchstat and do not regress startup time or allocations without a stated reason.

Read the full file on GitHub · 74 lines

Changes

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.

  1. 2mo ago First seen · 74 lines · 900 tokens per session scan A e39f1385de14

Subscribe to this mod's changes

sheena CLAUDE.md is an instructions file published in the GitHub repository goccy/sheena (44 stars, last pushed 1mo ago), licensed MIT. It adds 900 tokens to every session, about $0.0036 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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