# ai-sandbox Run an autonomous coding agent against your real project, with the escape routes closed: only the current directory is mounted, no ambient environment variables, no root inside, hard resource caps, and outbound network limited to an explicit allowlist that the agent cannot lift. Single bash script, rootless podman, Ubuntu 24.04. No daemon, no k8s, no config language. ``` $ cd ~/Projects/billing-api $ pi --allow aipi.reeseapps.com --env AI_API_TOKEN [aisb] egress gate aisb-gate-7f3c1a -> 127.0.0.1:18084 (1 domains, 0 ip/cidr entries) [aisb] egress net=allow enforce=nft proxy=[100.64.0.1:18084] direct=0 dns=0 pi ``` `pi` there is an alias for `ai-sandbox`. Inside, the agent sees `/project` (your cwd, read-write), nothing else on your disk, and the internet only where you pointed it. ## Install ```bash git clone && cd ai-sandbox ./install.sh --alias pi # symlinks to ~/.local/bin and adds the alias to ~/.bashrc ai-sandbox doctor # checks podman, rootless, subuid, pasta, SELinux, uid mapping ai-sandbox build # optional: build the image now instead of on first run make test # 390+ assertions (unit needs no containers; --e2e builds and runs) ``` Requirements: podman ≥ 5 running rootless (with a `/etc/subuid` range for your user), and either `pasta` (default in podman 5) or `slirp4netns`. Nothing else — shellcheck, tests and the image build all run through podman. ## The alias, and how arguments are read Sandbox flags are consumed until the first positional argument or unknown flag; those become **arguments to the harness**: ```bash alias pi='ai-sandbox' pi # runs pi inside the sandbox pi --allow aipi.reeseapps.com --env AI_API_TOKEN --model turbo # ^^^^^ sandbox ^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^ for pi pi --shell # a bash shell in the same sandbox pi --net none -- make test # -- replaces the command entirely ``` `--strict-args` turns an unrecognised flag into an error instead of a pass-through, which is what you want in scripts. ## Network policy | mode | what it means | |---|---| | `--net allow` *(default)* | Only the allowlist is reachable. A netfilter ruleset inside the container plus a domain-filtering proxy on the host loopback. If the ruleset cannot be installed, the sandbox **refuses to start** (exit 77). | | `--net none` | No network at all. | | `--net full` | Nothing restricted. Prints a warning. Never the default. | ```bash ai-sandbox --allow aipi.reeseapps.com --allow registry.npmjs.org --env AI_API_TOKEN ai-sandbox --allow 10.20.0.5:5432 # a database: pinned IP and port ai-sandbox --allow files.pythonhosted.org --allow pypi.org ai-sandbox --no-gate --allow example.com # no proxy container: pin resolved IPs instead ai-sandbox --proxy corp-proxy.internal:3128 # route through a proxy you already run ``` Domains match that name and anything below it, and are enforced by the gate at CONNECT time, so CDNs and rotating IPs are not a problem. IP/CIDR entries become direct netfilter rules for non-HTTP destinations (databases, etc.). An allowlist is **required** in `allow` mode: an empty list is a hard error, never a silent free-for-all. Keep it in the repo so the policy is reviewable: ``` # .ai-sandbox/allow (one entry per line, # comments fine) aipi.reeseapps.com registry.npmjs.org ``` If you bridge your pi config (below), ai-sandbox tells you when the model endpoint your own `models.json` points at is not in the allowlist -- pi would otherwise start and sit there unable to answer, which reads like a broken sandbox. ## Environment Nothing is inherited except `TERM LANG LC_ALL LC_CTYPE TZ`. ```bash --env AI_API_TOKEN # from your environment --env FOO=bar # literal (shows up in ps; prefer the two below) --env-file ~/.config/secrets # a 0600 NAME=VALUE file ``` Values are handed to podman through a `0600` file that is removed when the run ends, so they never appear in `ps`, in the printed dry-run, or in the session log. Asking for a variable that is not set fails the run closed. ## Filesystem Your cwd is mounted at `/project` and is the working directory. That is the only *writable* mount, and nothing else on the host is visible except the one exception below. Everything else is opt-in: ```bash --mount ~/.ssh:ro # if the agent must be able to push --mount ../docs:/docs:ro # read-only reference material --no-cwd # a scratch sandbox with nothing mounted --read-only # read-only root filesystem --ephemeral-home # do not persist /home/sandbox (default: persist in a volume) ``` Files the agent writes land on your disk owned by **your** uid, not root (`--userns=keep-id`, verified by `doctor`). ### Your `.agents` is shared, read-only A harness with no skills is a harness you have to re-brief on every run, so `~/.agents` — skills, prompt templates, your standing `AGENTS.md` — is bind-mounted at `/home/sandbox/.agents`, which is where pi looks for user-level skills. Nothing is copied; it is one mount, and it is **read-only**: ```bash pi # your skills are there pi --no-agents # a run where the harness sees none of them pi --agents-dir ~/work/.agents # a different set, e.g. per-team ``` Read-only is not a convenience limit. A skill is an instruction the model follows *later*, on the host, outside the sandbox — so a sandbox that could edit `~/.agents` had a persistence path out of itself, planted as a helpful-looking `SKILL.md`. There is no flag to make it writable, and the `ro` holds even with `--insecure-keep-root`. A project's own `.agents/` needs no setting at all: it is inside the project mount, and harnesses that read both (`pi` reads `~/.agents/skills` and `.agents/skills`) see the project's next to yours. What that costs in exposure is spelled out in [`docs/threat-model.md`](docs/threat-model.md): whatever is in those files — including any token someone pasted into a skill — is now readable by the agent you are sandboxing. Run `--no-agents` if a set of skills is not one you would hand to a stranger. ## Pi inside the sandbox The image has `pi` baked in, and its home is a volume, so out of the box the sandboxed pi has no provider and no preferences. Rather than making you configure it twice, `ai-sandbox` **bridges** your host `~/.pi/agent/{models,settings}.json` -- rewriting them, because copying them would ship your credential into a container whose entire purpose is to be unable to use it: | your host config | what the sandbox gets | |---|---| | `apiKey: "sk-..."` or `apiKey: "!pass show ..."` | `apiKey: "$AI_API_TOKEN"` -- pi resolves it itself, no value is written to disk | | a header like `X-Trace: "!date +%s"` | dropped, and reported: a host command is not run in the sandbox | | `baseUrl: "https://aipi.reeseapps.com/v1"` | unchanged, along with every model, limit and thinking level | | settings: provider, model, theme, thinking budgets, telemetry | unchanged, merged per key | | a settings value pointing into `~` | dropped, and reported: that path is not mounted | | `auth.json`, `models-store.json`, sessions, extensions | never touched | The rewritten pair is seeded into `/home/sandbox/.pi/agent` at container start, owned by your uid, mode `600`. The two files are managed differently, because they are different kinds of thing: | file | rule | why | |---|---|---| | `models.json` | replaced when missing or unchanged, left alone once you edit it in the sandbox | it is a catalog; a partial merge of a provider list is worse than either choice | | `settings.json` | **merged per key** | pi rewrites its own settings — a theme change, "seen the changelog" — and managing the file whole meant that one write froze *every* host preference out of the sandbox permanently | So in `settings.json`: a key you change inside the sandbox stays yours, a key you never touched follows the host again, a key the host drops disappears unless you had changed it, and a key pi added (`lastChangelogVersion`) survives. ### Thinking is xhigh, and it is policy `defaultThinkingLevel` is the one setting `ai-sandbox` insists on, because pi's own default is `medium` and a sandbox run is usually the kind of work you want reasoned about hard: ```bash pi --allow aipi.reeseapps.com # xhigh, whatever your host settings.json says pi --thinking max ... # this run only pi --thinking off ... # no reasoning, e.g. a mechanical refactor at scale pi --thinking host ... # stop forcing it; your settings.json decides ``` `--thinking` is a policy, not a preference: it is written over the merged settings on every run, so a run cannot set its own thinking level down for the runs after it. It is `pi`-only — codex, claude and anything you put after `--` read their own config, and ai-sandbox leaves that alone. `--no-pi-config` declines the policy too, since "pi starts with its own defaults" is what that flag is for. The token itself follows the normal rule -- it is the one variable the bridged config names, so it is passed by name (never by value, and never into `ps`): ```bash pi --allow aipi.reeseapps.com # AI_API_TOKEN is picked up and announced pi --no-pi-token-env ... # don't pass it; the run then fails closed pi --pi-token-env GW_TOKEN ... # a different variable name pi --no-pi-config --shell # no bridge at all ``` Refusing rather than launching a pi with no credential is deliberate -- the alternative is an agent that silently cannot reach its model. ## Image Both images come from one base, `docker.io/library/ubuntu:24.04` — including the gate, which is squid from Ubuntu's apt rather than a third-party image. Built once per distinct policy and tagged by content hash: git, curl, jq, build tools, python3, Node 22 (tarball verified against nodejs.org `SHASUMS256.txt`) and the `pi` CLI. `--install PKG` adds packages and produces a different tag, so variants coexist, and `--base-image` swaps the base. ### The base is pinned by digest A tag is a moving pointer: `FROM ubuntu:24.04` means "whatever Canonical points at this week", which makes a build unreproducible and a security patch invisible. So the tag is resolved to a digest, recorded under `~/.cache/ai-sandbox/base/`, and the digest goes into the `FROM` line *and* into the content hash — refreshing the base produces a new image instead of mutating one a sandbox may be running right now. ```bash ai-sandbox update --check # what upstream has, what you are pinned to, nothing built ai-sandbox update # re-resolve, rebuild sandbox + gate, keep the old image ai-sandbox build --refresh-base ``` Freshness is a TTL: every `AISB_BASE_TTL_DAYS` (default 7) the digest is re-resolved, which is a manifest read (`skopeo`), not a download. Offline, or with `AISB_BASE_AUTO_UPDATE=0`, the recorded digest is kept — a stale pin beats a mutable one, and `AISB_BASE_TTL_DAYS=-1` pins until you say otherwise. A build with no digest is announced as `UNPINNED`, labelled that way, and warned about by `doctor`. Preview modes (`--dry-run`, `--print-*`) never touch the network, so they stay scriptable and report the pin you already have; `inspect` is the one that asks the machine now. ### What an image admits to being `podman image inspect` on any ai-sandbox image shows `aisb.base-digest`, `aisb.node`, `aisb.pi-package`, `aisb.pi-version` (plus `aisb.role=gate` for the gate), and `/etc/aisb/manifest.txt` inside it lists every resolved apt package version — the answer to "which squid was doing the filtering" once the build log is long gone. The previous image is always kept after an update, so rollback is a tag away. ## Inspecting a run ```bash ai-sandbox --dry-run --allow example.com --env KEY # exact podman invocation, secrets redacted ai-sandbox --print-policy # effective policy as key=value lines ai-sandbox --print-entrypoint # the enforcement script baked into the image ai-sandbox doctor [--deep] # host checks; --deep tests egress for real ai-sandbox ps | clean [--all] [--volumes[=GLOB]] | inspect | gate up|status|logs|down ``` State lives under `~/.local/state/ai-sandbox` (session dirs, `log` of every run with no secret values, build logs). Config in `~/.config/ai-sandbox`. `/home/sandbox` is a named volume (`aisb-home`) so npm and tool caches survive between runs. It outlives the image, so after changing the image you may be looking at a stale home: `ai-sandbox clean --volumes` reclaims unused ones. It only deletes volumes in the `aisb-` namespace that no container references, and `--volumes=GLOB` narrows it to one name. ## Why it is hard to undo from inside The container starts as root with `CAP_NET_ADMIN`, the entrypoint installs the egress ruleset, and then it execs your command through ``` setpriv --reuid=1000 --regid=1000 --clear-groups --inh-caps=-all --bounding-set=-all --no-new-privs ``` No root, no capabilities, `no-new-privileges`. Flushing the ruleset needs `CAP_NET_ADMIN`; `unshare -n` needs `CAP_SYS_ADMIN`; setuid helpers cannot hand either back. Both are asserted against a real container in [`tests/e2e/11_net.sh`](tests/e2e/11_net.sh). Details and the measurements behind the design: [docs/networking.md](docs/networking.md). **Read [docs/threat-model.md](docs/threat-model.md)** — it says plainly what this does not protect you from (allowlisted destinations, container escapes, anything you explicitly mounted). ## Project layout ``` bin/ai-sandbox the application: one script, ~1.3k lines install.sh symlink into ~/.local/bin + optional alias config/ example config, allowlist and env file docs/ networking.md, threat-model.md, recipes.md tests/run.sh runner; tests/unit/* (no containers) tests/e2e/* (real ones) tests/spike_network.sh re-measure podman's behaviour on a new host Makefile make test | e2e | lint | check | doctor | build ``` ## Development ```bash make test # unit: args, config, argv construction, env handling, rule generation make e2e # + real containers: build cache, egress blocking, capability drop, lifecycle make lint # shellcheck in a container make style # bash -n ``` The Containerfile, the container entrypoint and the squid config are all generated from `bin/ai-sandbox`, so the script remains the single source of truth (`--print-containerfile`, `--print-entrypoint`).