ai-sandbox/.agents/skills/doc-sandbox/SKILL.md

---
name: doc-sandbox
description: Answers questions about ai-sandbox and ai-sandbox-autophase — what a flag or config key does, why a run refused to start (exit 77/78), how the egress allowlist, the squid gate and the in-container nftables ruleset work together, how the ~/.agents share or the pi config bridge or the base-image digest pinning behaves, what the image contains, how to run a given harness or language, what the sandbox does and does not protect against, and how the phase driver splits sandbox work from host git. Use when the user asks what something in ai-sandbox means, is about to, or just did, run ai-sandbox and wants an explanation, hits a sandbox error, or asks about the tool's design, security model or limitations. Answers from the installed program's own text plus the repo docs and tests, never from memory; runs only side-effect-free preview commands and never a build, container, or network call.
---

# doc-sandbox

ai-sandbox is one bash script that generates its own Containerfile, container entrypoint, squid
config and netfilter rules. That is what makes it answerable: the text of the program *is* the
documentation of the installed version, and three of its flags print the artifacts it generates.
Read those; do not recall.

## Ground truth, in this order

1. **The installed program** — `ai-sandbox --help`, and its source: `readlink -f "$(command -v
   ai-sandbox)"`. If they disagree, the installed program is what the user will run.
2. **The repository**, if present: `README.md` (what and why), `docs/networking.md` (the
   *measurements* behind the enforcement model), `docs/threat-model.md` (what is **not** protected),
   `docs/recipes.md` (invocations per harness/ecosystem/pipeline), `AGENTS.md` (design rules).
3. **The tests** — the executable spec. `tests/unit/*` needs no containers and states exact shapes;
   `tests/e2e/*` proves behaviour in a real container (e.g. `11_net.sh` for "can the agent lift the
   ruleset"). When behaviour is subtle, the test answers better than prose.
4. **This skill's fact sheet** — fast, but if it conflicts with the above, the above wins and this
   file is a bug to fix.

```bash
bash scripts/locate.sh      # where each of those lives on this machine, and the version
```

## Working a question

1. Classify it: a **flag/key**, a **failure**, a **mechanism** ("how is egress enforced"), a
   **security boundary** ("can it read my ssh keys"), or a **pipeline** question. Then read
   `references/source-map.md` — it maps each to the function, doc and test that hold the answer.
2. Read that source. Grep, don't skim: `grep -n 'print-policy' bin/ai-sandbox`.
3. Check the version you read (`ai-sandbox version`) and say which one you read when it matters —
   behaviour that changed recently includes the working-directory mirroring, the `settings.json`
   per-key merge, the `xhigh` thinking policy and the base digest pinning.
4. If the question is about *this machine's* behaviour, prefer a preview command over an opinion
   (§safe commands) and quote its output.
5. Answer in the format below. If the source does not contain it, say **it does not exist** and
   name the closest real thing — a plausible invented flag is the worst failure mode available here.

## Answer format

* **The answer, one or two sentences**, in the user's terms.
* **The command** to run, copy-pasteable, with real flag spellings.
* **Where it comes from**: `bin/ai-sandbox` (`build_argv()`), or `docs/networking.md`, or
  `tests/e2e/11_net.sh`. So they can check you.
* **What it does *not* do**, whenever the question touched security — e.g. "the allowlist limits
  *where*, not *what*: an allowlisted remote plus a token can ship your code."
* A pointer to `docs/threat-model.md` when the honest answer is "this is out of scope" (kernel
  escapes, anything allowlisted, anything you mounted).

## Safe to run while answering

```
ai-sandbox --help                 ai-sandbox version
ai-sandbox --dry-run              the effective invocation, env values redacted
ai-sandbox --print-entrypoint     the enforcement script baked into the image
ai-sandbox --print-containerfile  the generated Containerfile
ai-sandbox --print-policy         effective policy as key=value -- with one caveat, below
```

These build nothing, start no container, write no session state and reach no registry — that is a
deliberate property of the tool (preview modes are what make it scriptable), so use them freely.
They read config files, so they show the *effective* policy where you are. Two honest exceptions:
`--print-policy` also ensures the home-cache volume exists, so it fails without podman (a deviation
from the repo's own "preview must not write state" rule, worth reporting rather than repeating);
and with `--no-gate`, resolving domain entries does hit DNS.

Not for an explanation, unless the user asked about the machine and agrees:

* `inspect` — prints the same policy but resolves the base digest **now**, so it may contact the
  registry.
* `doctor [--deep]` — host checks; `--deep` runs a real container and probes egress.
* `build`, `update`, `gate up`, `clean`, and any real run — these change the machine.
* `cat`ing `~/.pi/agent/models.json` to answer a question about the bridge: read the *code*
  (`pi_config_bridge()`), not the file with a live key in it. Never echo a credential, an
  `auth.json`, or anything from a `--env-file`.

## Facts you may state without reading (still: state the version)

| topic | fact |
|---|---|
| precedence | built-in default < `~/.config/ai-sandbox/{config,allow}` < `./.ai-sandbox/{config,allow}` < `AISB_*` < CLI. `allow/env/mount/install/label` accumulate; other keys replace |
| arg parsing | stops at the first positional or unknown flag; the rest goes **to the harness**. `--` replaces the command. `--strict-args` makes an unknown flag an error |
| default net | `allow`, and an empty allowlist in `allow` mode is a hard error, never a silent free-for-all |
| enforcement | two stacked controls: an in-container `inet aisb` nft table with `policy drop` on output, installed by the entrypoint as root before it `setpriv`s to uid 1000 with no capabilities, plus a squid gate on the host loopback that filters by domain at CONNECT |
| refusals | exit **77** ruleset could not be installed; **78** policy file missing in the container. Both are the sandbox working; `--allow-unenforced` is the named escape hatch |
| gate ports | squid relays only **80, 443, 8443**; `--allow domain:8080` is not what it looks like. IP/CIDR entries are direct netfilter rules instead (default ports 80,443) |
| host services | `100.64.0.1` (config: `gate_addr`) inside the container *is* the host's loopback; only the gate's port is reachable through it unless you `--allow 100.64.0.1:<port>` |
| inbound | there is no publish flag, and in `--net allow` the generated ruleset's input chain is `policy drop` too, so a `-p` pushed through `extra_args` is dropped inside. That last half is a reading of `gen_rules()`, not a measurement — probe it (right-sandbox's `references/port-and-loopback.md`) before promising a preview URL |
| filesystem | cwd mounted rw **at its host path** (falls back to `/project` with a message when the host path would bury `/tmp`, `/usr`, `/etc`, `/var`, `/opt`, `/run`, the container home, or `/`); nothing else is mounted except the `.agents` share and the read-only policy mount at `/run/aisb` |
| the container user | uid/gid 1000, the image's own `sandbox` account, `$HOME` = its home (`--userns=keep-id`, so files the agent writes are owned by *you* on the host). Skills land at `~/.agents` on both sides and they are different directories |
| skills | host `~/.agents` → the container's `~/.agents` (`agents_dest`) **read-only**, no flag makes it writable; `--no-agents` to withhold it, `--agents-dir` for another directory. Its contents are readable by whatever runs in there |
| env | nothing inherited but `TERM LANG LC_ALL LC_CTYPE TZ` (plus `HOME`, `AISB`, `AISB_SESSION`); values travel in a `0600` file, never argv; `--env NAME` where NAME is unset **fails the run** |
| pi bridge | host `~/.pi/agent/{models,settings}.json` rewritten, not copied: `apiKey` → `"$AI_API_TOKEN"`, `!command` values dropped, `auth.json` never touched; `settings.json` merged per key; `defaultThinkingLevel` is policy (`xhigh`) re-applied every run unless `--thinking host` |
| image | one base (`ubuntu:24.04`) pinned to a **registry digest** that is part of the image tag; Node pinned + sha256-verified; `pi` version-pinned; `--install PKG` → a different tag; a build with no digest is labelled `UNPINNED` and `doctor` warns |
| limits | `cpus 4`, `memory 4g`, `pids 512`, `tmpfs 1g`; the container home is a named volume (`aisb-home`) that outlives the image, `--ephemeral-home` swaps it for a tmpfs |
| state | logs/config/cache under `~/.local/state/ai-sandbox`, `~/.config/ai-sandbox`, `~/.cache/ai-sandbox`; `~/.local/state/ai-sandbox/log` records every run **without secret values** |
| autophase | the agent *and* `.agents/validate.sh` run in the sandbox; the commits and every push happen on the host, and the git remote is deliberately unreachable from inside. Host git runs with an empty hooks path and refuses to deliver if a sandboxed unit changed `.git/config` or `.git/hooks/` |

## When the answer is "no"

Say it plainly, then give the closest real thing:

* "publish a port" → no; run the server on the host (the mount is your disk), or one named
  `--net full` preview run with `AISB_EXTRA_ARGS=-p …` and an explicit warning that that run has no
  egress policy.
* "make the sandbox able to write my skills" → no, by design: a skill is an instruction you follow
  later on the host. Author it in the project and move it yourself.
* "let the pipeline push from inside the sandbox" → no: an agent that can push can ship what you are
  about to review. `ai-sandbox-autophase` delivers on the host.
* "inherit my environment, it's annoying" → no; that ambient environment is exactly the exfil target.
  Name what you need with `--env`.
* "silently fall back to no network policy when the ruleset fails" → no: exit 77.

If the user wants the missing thing, that is a change to `bin/ai-sandbox` — say which function
would carry it (`gen_rules()`, `build_argv()`, `parse_args()`), that it needs an entry in
`tests/e2e/`, and that per the repo's own rules it must fail closed and print no values.

## References

* `references/source-map.md` — question topic → function / doc / test, plus the FAQ and the
  vocabulary (`split_target`, `classify_allows`, gate vs `--no-gate` vs `--proxy`, `POL[]`/`P_*`/`OPT_*`).
* `scripts/locate.sh` — find the installed script, the version, the repo docs, the state dirs.