configuring-the-jail

configuring-the-jail is a skill for Codex from mschulkind-oss/yolo-jail. It costs 68 tokens per session (3,020 once invoked), scanned B, original, Apache-2.0.

A guide for making changes to yolo-jail's persistent configuration file, yolo-jail.jsonc. It covers packages, resource limits, ports, mounts, MCP or LSP connections, environment settings and host-capability exceptions.

In plain words
What is it for?
Use it when a project always needs a tool, more CPU or memory, a port or mount, an MCP or LSP server, an environment source, or another persistent jail setting.
Why use it?
It clarifies which changes survive a restart and which are only temporary. It also explains the checks required before asking someone to restart the jail.

Skill for Codex

Written for Codex: reads ~/.codex or $CODEX_HOME. Also seen: reads .claude/ paths; mentions Codex.

Not installable: its command points at a path on the author’s own machine, so it runs nowhere else. The line is /home/agent/code/sysadmin.

Good fit Use it when a project always needs a tool, more CPU or memory, a port or mount, an MCP or LSP server, an environment source, or another persistent jail setting.

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Install

Getting it into your agent

There is no command for this one: it runs only inside a plugin, and the catalogue could not identify which plugin ships it. The source is linked below.

Made for: Codex.

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.

agentmods badge for configuring-the-jail

README.md
[![agentmods](https://agentmods.dev/badge/skills/mschulkind-oss/yolo-jail/configuring-the-jail/github.svg)](https://agentmods.dev/skills/mschulkind-oss/yolo-jail/configuring-the-jail)
Your own site
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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 configuring-the-jail

Your own site · 80×15
<a href="https://agentmods.dev/skills/mschulkind-oss/yolo-jail/configuring-the-jail"><img src="https://agentmods.dev/badge/skills/mschulkind-oss/yolo-jail/configuring-the-jail.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,020 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. 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 $0.00068 $0.03020
Opus 5 $0.00034 $0.01510
Sonnet 5 $0.00014 $0.00604
Haiku 4.5 $0.00007 $0.00302

Measured 2d ago against content hash f11f887f6592, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade B, and why

configuring-the-jail scanned grade B with 1 finding 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.

Reads agent configuration directoriesmediumAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

Your own agent config — `~/.claude/settings.json`, `~/.codex/config.toml`,
internal/jailcontent/builtinskills/configuring-the-jail/SKILL.md · 231 lines

How it starts

The opening of the file, as written. The whole thing — 231 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Configuring the Jail

Use this when a change must be baked into how the jail is built so it survives a restart: a package/runtime the project always needs, a resource limit, a published port or mount, an MCP/LSP server, an env source, or enabling a host-capability loophole.

Do NOT use this for one-off installs. The jail has internet and you can npm i -g, pip install, uv pip install, or mise use a tool right now with no config change and no restart. Only reach for yolo-jail.jsonc when the tool must persist across restarts or be present for every future session.

You already know the loop — here's what it leaves out

The always-on briefing already states the rule: edit → yolo check --no-build → fix any [FAIL] → then STOP and ask the human to restart (you cannot restart this jail from inside it). Assume that. This skill covers the parts that rule leaves out.

Rebuild vs. restart — which changes are slow

Most changes take effect on the next restart (config is re-read at launch). Only changes to the image package set force a slower image rebuild first, and there are exactly two ways to change that set:

  • packages — nix packages baked into the image.
  • gpu.vaapi: true — but only when gpu.enabled: true and gpu.vendor: "amd", which pulls mesa + libva-utils into the package set.

Everything else — mise_tools, resources, network, mounts, mcp_servers, lsp_servers, env_sources, loopholes, packs — is restart-only, no rebuild. Prefer mise_tools over packages for CLIs and runtimes: it avoids the rebuild entirely. When you touch packages (or trigger vaapi), say so in your handoff — on the yolo-jail dev repo a rebuild also needs a host just load.

Which file — and how the layers merge

Three layers merge, later wins:

  • ~/.config/yolo-jail/config.jsonc — user/machine defaults.
  • <workspace>/yolo-jail.jsonc — the committed per-project config. Edit this one unless told otherwise.
  • <workspace>/yolo-jail.local.jsonc — gitignored per-machine tweaks (auto-merged when present).

Read the full file on GitHub · 231 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. 2d ago Changed · +13 lines f11f887f6592
  2. 11d ago First seen · 218 lines · 68 tokens per session scan B 5fd7e2d53382

Subscribe to this mod's changes

configuring-the-jail is a skill published in the GitHub repository mschulkind-oss/yolo-jail (2 stars, last pushed today), licensed Apache-2.0. It adds 68 tokens to every session and 3,020 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it B with 1 finding (reads agent configuration directories). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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