sbx/t3code-kit repository overview

⁠t3code

A mixin kit that prepares a sandbox for T3 Code⁠'s SSH integration: it installs the t3 npm package, and the libatomic1 its binaries need, so the first T3 Code connection starts a server that is already there instead of fetching it from the npm registry on the spot. Pair it with any agent kit.

⁠Usage

sbx run claude --kit "docker.io/sbx/t3code-kit:latest" .

Or straight from this repository over git:

sbx run --kit "git+https://github.com/docker/sbx-kits-contrib.git#dir=t3code" claude

Or with a local clone of this repo:

sbx run claude --kit ./t3code/ .

Prerequisites:

• A base image with Node.js ≥ 18 and npm. All standard agent templates ship both. The install fails loudly with a clear message if npm is missing.

Inside the sandbox:

t3 --version

Then connect the sandbox to T3 Code over SSH as usual, see Connect T3 Code to a sandbox⁠.

⁠Arguments

⁠Telemetry

Telemetry is off by default. The sandbox proxy does not allow the telemetry host unless told to, and a server that cannot reach it keeps retrying and logging the failure. To opt in, allow the host and pass the argument:

sbx policy allow network us.i.posthog.com
sbx run claude --kit "docker.io/sbx/t3code-kit:latest" --kit-arg t3code.telemetry=true .

The kit sets T3CODE_TELEMETRY_ENABLED in the sandbox environment, which the t3 server reads at startup.

⁠How it works

⁠Why libatomic1

t3 installs a platform package, @t3code/t3-linux-<arch>, carrying prebuilt native modules including node-pty. Nothing compiles at install time, so the base image needs no toolchain, but those binaries do link against libatomic1. Without it npm install still succeeds and the binary it installed does not run:

t3: error while loading shared libraries: libatomic.so.1: cannot open shared
object file: No such file or directory

T3 Code reports nothing more specific than a connection timeout when that happens, so the kit installs libatomic1 itself rather than counting on the base image to carry it. The check is ldconfig -p, so a base that already has it runs no apt-get at all.

⁠Why t3 is installed at build time

T3 Code's own remote bootstrap resolves t3 by falling back to npx --package t3@latest when it isn't already on PATH. That works, but it means every first connection depends on npm registry access, and pays the download during the connection attempt. Installing t3 globally at kit-install time does that work once, up front, so connecting is just SSH plus starting a binary that is already there.

⁠Why these domains

permissions.network.allow is the kit's complete outbound contract. CI runs e2e under a deny-all policy.

⁠Cleanup

Everything is sandbox-local: the global t3 npm package and libatomic1 disappear with the sandbox (sbx rm <name>). Nothing touches the host.