ai-sandbox/README.md

# 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 your cwd at the path it
has on the host — `~/Projects/billing-api`, not a generic `/project` — read-write, and
nothing else on your disk, with the internet only where you pointed it.

## Install

```bash
git clone <this repo> && 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 **the path it has on the host**, and that is the working
directory. So `pwd`, an error the agent quotes back, a commit message and the window title
your harness derives from the cwd all name *this* project instead of reading the same as
every sandbox in the session. The mount itself is unchanged by the naming: same directory,
same read-write, nothing else visible except the one exception below.

A bind mount hides whatever was already at that path in the image, so a host path that
would land on something the image or the sandbox owns (`/usr`, `/etc`, `/var`, `/opt`,
`/tmp`, `/run`, `/home/sandbox`, `/`) falls back to `/project` — and says so, because a
working directory you did not choose is worth a line:

```
[aisb] ai-sandbox: cannot mirror /tmp/scratch/billing-api: the sandbox owns /tmp*, so the
project is mounted at /project instead (--workdir DIR to choose)
```

`/tmp` is the one case worth naming: the sandbox mounts a tmpfs there, and podman puts
that tmpfs *over* a bind of the same path, so a project under `/tmp` would come out as an
empty directory that happens to be writable and to have the right name. Measured, not
guessed — see [docs/networking.md](docs/networking.md).

`--workdir DIR` picks the mount point yourself (`auto`, the default, is the mirroring
behaviour above). The table below is everything else, all opt-in:

```bash
--mount ~/.ssh:ro                # if the agent must be able to push
--mount ../docs:/docs:ro         # read-only reference material
--workdir /src                   # mount and cd there instead of mirroring the host path
--no-cwd                         # a scratch sandbox with nothing mounted (lands in /project)
--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).

## An unattended pipeline: `ai-sandbox-autophase`

A phase pipeline (`.agents/phases/todo/…`) is the harshest thing to ask of a sandbox:
hours of unattended work by an agent that installs dependencies, runs the tests and
wants to commit and push. It gets its own driver, and the split inside that driver is
the design:

| in the sandbox | on the host |
|---|---|
| the executor agent of every task, and the phase's final pass | the phase commit |
| `.agents/validate.sh`, the pass/fail gate | the push — and the re-push of anything an earlier run left behind |

The git remote stays unreachable from inside on purpose: an agent that could push could
ship what you are about to review. `git status`, `diff`, `log` and `blame` work in there
(the repository is the mount, git is in the image), and the agent is told in its own
prompt that `push`/`fetch`/`pull` cannot work, so it does not spend attempts discovering
that. Delivery is the driver's job: it pushes when a phase commits, again before the next
phase starts, and again at the end of the run, so nothing sits unpushed between runs. A
push failure stops the run and prints the command that finishes it — the commit is local
and safe, and the next run takes it out.

The gate runs in the sandbox for the same reason the agent does: `.agents/validate.sh`
sits in the writable mount, so running it on the host is running agent-editable bash on
the host. `--validate-in host` exists for a project whose toolchain only exists on the
machine, and says so on every run.

```
[2026-10-28 02:11:03] preflight: one sandboxed shell, to prove the launcher, the image and the policy
  aisb-ok aisb=1 git=2.43.0 user=sandbox cwd=/home/you/Projects/foo
[2026-10-28 02:11:04] checking for commits a previous run left unpushed
  (up to date with origin/main)
[2026-10-28 02:11:04] ━━ 01_one/01_task.md — attempt 1/3 ━━
  (every line prefixed with the time, as the pipeline prints them)
  (committed: 9f1c2ab phase: 01_one)
  (pushed: 9f1c2ab phase: 01_one)
[2026-10-28 02:41:52] ✓ pipeline done — 2 unit(s) delivered this run: 01_one/01_task.md 01_one/00_phase.md
```

### It runs *your* command, not a copy of it

The driver does not know your allowlist and does not try to. It runs your launcher — by
default the `sandbox-pi` shell function you keep in `~/.bashrc.d`:

```bash
sandbox-pi () {
    export AI_API_TOKEN=$(pass aipi/dev-token)
    ai-sandbox --allow aipi.reeseapps.com --allow github.com \
               --allow pi.dev --allow release-assets.githubusercontent.com \
               --env AI_API_TOKEN "$@"
}
```

That last `"$@"` is the whole contract. A function launcher is called *with* the run: the
flags, then `--`, then the command to run inside, and one that ends at `--env AI_API_TOKEN`
drops all of it. It then starts the image's default harness with no prompt — and a `pi`
with no prompt on the other side of a launcher that attached your terminal sits waiting
for keystrokes while its output goes into a pipe nobody is watching. The driver names a
launcher like that in `--status` and refuses to start the pipeline; aliases and whole
command lines do not need it, because the shell appends the words to those by itself.

A script cannot see an interactive shell's functions, so the driver looks the name up in
`~/.bashrc.d/*`, `~/.bashrc`, `~/.bash_aliases` and `~/.profile` (or `AISB_AP_RC_FILES`)
and takes the *definition* — probing never calls it, so a preview cannot fetch a token.
Reading that definition is done in a throwaway session of its own, with no stdin and a
bounded read: an interactive bash started from your terminal takes your terminal, gets
stopped for it, and a stopped process ignores the timeout sent to it, so the probe used to
be able to wedge the whole script before it printed a single line.

Each child then runs exactly what your shell would have, `pass` included, once per unit
so an overnight run is not holding yesterday's token. An alias or a plain program works
too; `--pi-cmd` also accepts a whole command line.

```bash
cd your/project
ai-sandbox-autophase --status     # launcher, pending units, git plan. Runs nothing.
ai-sandbox-autophase --dry-run    # the exact child and gate commands
ai-sandbox-autophase              # every pending task, in pipeline order
```

Every child is started as `<your command> --no-tty --no-interactive -- pi <args> <prompt>`,
with its stdin on `/dev/null`: your flags first, then the two that keep an unattended run
off your terminal (no TTY to corrupt the JSON stream, no stdin for your keystrokes to fall
into), then `--`, after which ai-sandbox reads nothing but the command. Those two are
flags, and a launcher is free to lose them, so the `/dev/null` is what actually guarantees
the second one.

| flag | |
|---|---|
| `--pi-cmd NAME` | the launcher: function, alias, program or whole command line |
| `--rc-files A:B` | which rc files to look in |
| `--sandbox-args ARGS` | flags added to every run (default `--no-tty --no-interactive`) |
| `--validate-in sandbox\|host` | where the gate runs |
| `--no-push` | commit locally, deliver nothing |
| `--no-preflight` | skip the throwaway container that proves the chain works before spending tokens |
| `--trust-git-changes` | deliver even though the sandbox edited `.git/config` or `.git/hooks/` |
| `--unit`, `--phase`, `--max-units` | scope a run |

It does *all* the pushing — including the pipeline library's own — so that one function
answers for every commit that leaves the machine. And because a repository is not
something git merely records but something it **runs**, host-side git is started with an
empty hooks path, no pager, no system config and no `ext::` transport, and the run
refuses to deliver if a sandboxed unit rewrote `.git/config` or planted a hook. A
`pre-commit` written inside the sandbox is the sandbox executing code on the host, and
the phase commit is not worth finding that out the hard way.

`MAX_FIX_ATTEMPTS`, `PHASE_MODEL`, `PHASE_THINKING`, `PI_TRUST`, `FRESH_FIX`, `QUIET`,
`PHASE_NOTIFY` and `PHASE_COMMIT` behave as the phased-execution skill documents them —
the driver reuses that pipeline and replaces only the parts that assume the agent is a
local process.

## Project layout

```
bin/ai-sandbox            the application: one script, ~2.2k lines
bin/ai-sandbox-autophase  the pipeline driver: agent in the sandbox, git on the host
install.sh                symlink both into ~/.local/bin + optional alias
contrib/ai-sandbox.bash   bash completion for both
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/fixtures/phase-lib  contract fixture: the pipeline library's shape, without skill
                          or containers, for the driver's tests
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, rules, pipeline driver
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`).