sandbox SKILL.md skillA
This file is byte-identical to the first copy the registry indexed, one of 4 indexed copies. Same content hash, so the same checks give both the same grade.
sandbox from jakeselby/agent-harness is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add jakeselby/agent-harness/sandbox@git:20261009.a4aa40bPins git:20261009.a4aa40b in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- jakeselby/agent-harness
- Path
directory/model-citizen/primitives/skills/sandbox/SKILL.md- Versions recorded
- 3
- Latest version
- git:20261009.a4aa40b, committed Oct 9, 2026
- First version recorded
- Sep 28, 2026
- Size
- 4,454 bytes
- Repository stars
- 24
- License
- MIT
Fence an autonomous or long-running agent loop with the built-in sandbox and network off, or a container with the worktree mounted. Use before any unattended loop, before `execute` autonomy on an unfamiliar repo, and whenever a task pulls untrusted input.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Fence the loop A permission mode decides whether a call runs. A sandbox decides what a command can reach once it is running, and the OS enforces that on every child process. An unattended loop needs the second kind: nobody is at the prompt to answer for the first. ## Runtime scope The configuration and container example below are Claude Code-specific. Do not copy those settings into Codex. For Codex, use its native sandbox and approval controls as documented in [the configuration reference](https://learn.chatgpt.com/docs/config-file/config-reference). A read-only sandbox constrains filesystem writes; approval policy is a separate control. Native hooks are not a replacement for OS confinement. Custom Codex role defaults can be superseded by the parent turn's permissions; see `docs/runtime-controls.md` before delegating work that requires a hard boundary. Client qualification remains in the compatibility catalog. ## The Claude Code sandbox It "runs on macOS, Linux, and WSL2. Native Windows is not supported"; Linux and WSL2 need `bubblewrap` and `socat` installed first. Merge [claude-settings.json](claude-settings.json) into …
Read the whole file at its exact version.
How to install
mdr add jakeselby/agent-harness/sandbox@sha256:cad29b2b44b06160The line at the top of this page pins the label git:20261009.a4aa40b, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_uwkbjh242nnsy73j)
4 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 3 versions of this file, between Sep 28, 2026 and Oct 9, 2026, about one every 5 days. Its first recorded version is graded B and its latest A.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20261009.a4aa40b latest | 2026-10-09 | a4aa40b | 4,454 B | A | view · diff |
| git:20261006.39b4172 | 2026-10-06 | 39b4172 | 4,143 B | A | view · diff |
| git:20260928.ca93e6d | 2026-09-28 | ca93e6d | 4,187 B | B | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (4454 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
jakeselby/agent-harness · 24 stars · license MIT · pushed 2026-10-15 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_uwkbjh242nnsy73j GET https://markdownregistry.com/api/v1/resolve?ref=jakeselby/agent-harness/sandbox GET https://markdownregistry.com/api/v1/blob/cad29b2b44b061606b21a892edbe07c4ae1108845d4a50387d22cfe6a6625345
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.
More from jakeselby/agent-harness
Every file in jakeselby/agent-harness