[sbysb]

Git worktrees are a great isolation boundary for _changes_ (especially making changes in parallel on a single machine), but not behavior. If you are trying to actually run autonomous agents securely you need something that lives outside the harness that actually blocks actions in a way that can't be prompted around.

We use nono [1] for this internally, essentially blocking any actions we don't want agents to be able to do without human approval. Our developers can just run `task claude` or whatever their harness is) and it pre-wraps it with our profile that enforces:

- Filesystem: read/write only the worktree plus dev-tooling dirs (Go, Doppler, Graphite caches, git common dir); explicitly no Docker socket and it can't edit its own Claude settings files (so it can't loosen its own permissions).

- Network: outbound only to an allowlist - Anthropic, Doppler, Go module proxies, our dev environments while still allowing binding local dev-server ports.

- GitHub: read anything in the org, and create/edit PRs and push branches - but it cannot merge, close, review, or comment on PRs, delete branches, touch repo settings/secrets, manage auth, or use raw gh api. Those are all "human-only". GitHub tokens are never exposed to the agent; they're injected by a proxy so it can't read or exfiltrate them.

This is great because it is harness agnostic - any developer can use whatever harness they want as long as they port the nono profile to it, as it will enforce all of the above in a way that is not tied to a specific harness implementation

[1] https://github.com/nolabs-ai/nono

[madarco]

nono is great but you'll still won't be able to run multiple dev servers, dbs or test in the browser...

the better alternative is using sandboxes, for TRUE isolation.

but most people skip them because it's harder to set up a dev environment in a sandbox, for this I built agentbox [1], a tool to teleport your files, skills, settings, claude/codex subscriptions etc in any of the popular sandboxes. eg:

agentbox e2b claude

or:

agentbox hetzner codex

each session is persistent, with a full VM, with a browser, webVNC screen sharing and local https tunnel for easy preview on *.localhost domains.

Also git credentials never leave your pc: when a box needs access it passes through the agentbox service running on your machine, which allows PR creations, comments but only on the box branch, no deletion etc.

[1] https://github.com/madarco/agentbox

[sbysb]

> nono is great but you'll still won't be able to run multiple dev servers, dbs or test in the browser...

With our profile setup you can do all three of those things - there is a fresh chrome profile that is blocked against the same network firewall. Claude and Playwright can navigate to the dev stack and screenshot/test it (and non-allowlisted websites are blocked at the network level).

As long as the developer runs the `task start` command outside the sandbox (because docker is blocked), the agent can then interact with it all that they want, and our devs can run 2-3 of these per machine and work on concurrent projects. (based on memory usage / cpu usage)

> a tool to teleport your files, skills, settings, claude/codex subscriptions etc in any of the popular sandboxes

FWIW this is _explicitly_ the opposite of our threat model - everything other than your git credentials that you 'teleport' in (code, settings, Claude/Codex subscription tokens) now lives inside the blast radius, on third-party infra, and a prompt-injected agent in the box can send it anywhere unless you're also egress-filtering. A VM isolates the machine - it doesn't protect the data.

Much easier to keep it all local and refuse any network or file access to anything you don't explicitly approve

[alchaplinsky]

"read/write only the worktree", but git requires .git dir writable for common commands to work in a worktree. And that's where .git/hooks live. So agent inside that profile can still write a pre-commit hook that runs on your machine whenever you commit outside the sandbox. Or am I missing something?

[sbysb]

All git config and hooks are not writable inside the sandbox. This can be somewhat frustrating as you have to run git config commands outside, but the tradeoff is worth it imo. Nono allows for directory level permissioning, so the entire `.git/hooks` directory and `.git/config` / `.git/worktrees/*/config.worktree` are write blocked.

Worth calling out that this doesn't close all of these types of attacks, just the ones that are invisible (claude could very well write ./hack.sh and tie that in to your main.go, but at least it would be a diffable change, instead of invisible like a git hook)