cmux-freestyle

cmux Freestyle

Use this skill when a user wants a Freestyle VM snapshot that the cmux backend can boot Cloud VMs from. It lives in its own public repo, manaflow-ai/cmux-freestyle, so anyone with a Freestyle API key can run one shell script and get back a FREESTYLE_SANDBOX_SNAPSHOT id.

Freestyle snapshots are scoped to the account that created them. A snapshot id from manaflow's account, or from any other user, will not work for a different Freestyle account. Every user has to run the setup script against their own FREESTYLE_API_KEY. There is no shortcut.

When to use

• User asks how to point their own cmux at Freestyle.
• User self-hosts the cmux web backend and needs a snapshot pinned to a known cmux release.
• User wants to rebuild the cmux Cloud VM image on their own Freestyle account.
• User wants to iterate on the standalone repo (cmux-freestyle) instead of the in-repo builder at repo/web/scripts/build-cloud-vm-images.ts.

For internal cmux development that pushes a new snapshot to manaflow's Freestyle account and updates repo/web/services/vms/images/manifest.json, keep using repo/web/scripts/build-cloud-vm-images.ts. This skill is the external-user path.

What it builds

A Freestyle snapshot from a Dockerfile that mirrors freestyleBaseDockerfileContent in the in-repo builder:

• ubuntu:24.04, C.UTF-8, the same shell package set, the Python/OpenSSL shim required by the cmux browser proxy.
• cmuxd-remote Linux/amd64 downloaded from a pinned manaflow-ai/cmux GitHub release, SHA-256 verified during the image build against cmuxd-remote-checksums.txt.
• /usr/local/bin/cmux symlinked to cmuxd-remote.
• Node.js, Bun, plus pinned coding agent CLIs (Claude Code, OpenCode, Codex, Pi).
• Linux user cmux with passwordless sudo.
• Systemd unit cmuxd-ws.service running cmuxd-remote serve --ws --listen 0.0.0.0:7777 --auth-lease-file ... --rpc-auth-lease-file ... on Freestyle port 443 -> 7777.

The image runs the same smoke tests as the in-repo builder, so failures show up at snapshot build time, not later inside a live VM.

How to use it

The repo is self-contained; no cmux checkout required.

git clone https://github.com/manaflow-ai/cmux-freestyle.git
cd cmux-freestyle
export FREESTYLE_API_KEY=fk_...
./setup.sh

Or the one-liner:

FREESTYLE_API_KEY=

Useful flags / env on ./setup.sh snapshot (the default subcommand):

• --release <tag> or CMUX_RELEASE_TAG=<tag> pins the cmuxd-remote release. Default is the latest stable manaflow-ai/cmux release.
• --name <name> or CMUX_FREESTYLE_SNAPSHOT_NAME sets the Freestyle snapshot name.
• --skip-cache or CMUX_FREESTYLE_SKIP_CACHE=1 forces a clean Freestyle rebuild.
• --codex-spec none, --claude-spec none, etc. drop individual agent CLIs.
• --json emits a machine-readable result; the human path prints FREESTYLE_SANDBOX_SNAPSHOT=sh-... at the end.

The build takes 5 to 15 minutes depending on Freestyle's layer cache.

Full self-host bundle

./setup.sh is a dispatcher with four subcommands. Use them together when a user wants more than just the snapshot id:

web is the Next.js dev env bootstrap: it clones manaflow-ai/cmux to ~/cmux-freestyle-cmux, writes the Freestyle + Cloud VM env keys into web/.env.local, runs bun install, and brings up the per-worktree Docker Postgres unless --no-postgres is set. Stack Auth keys (STACK_SECRET_SERVER_KEY, NEXT_PUBLIC_STACK_PROJECT_ID, NEXT_PUBLIC_STACK_PUBLISHABLE_CLIENT_KEY) are honoured if exported but optional. The script only needs git and bun (plus docker for Postgres).

home is the "headquarters view": it installs and prepares the Ink/TypeScript port of cmux-home at ~/cmux-freestyle-home/ink. The TUI connects to the local cmux app's Unix socket and gives end users a Node-only dashboard of every workspace plus a Codex/Claude composer. The Ink port currently lives on the feat-ink-rewrite branch; switch the default --ref once it merges to main. The Rust crate at the cmux-home repo root remains the full-featured upstream.

If FREESTYLE_API_KEY is set in the env when bun dev runs (the home script exports it from the user's ~/.secrets/cmux.env and the shell), cmux-home renders a second panel under the workspace list titled Freestyle VMs (N). Each row shows the VM id, state, snapshot id (the one from ./setup.sh snapshot), and age. This makes the TUI a single dashboard for both local cmux workspaces and the user's Freestyle Cloud VMs, with the same selection cursor walking both panels.

Selecting a VM enables the following actions on the row:

• enter opens the sandbox workflow: creates a new cmux workspace running freestyle-vm-ssh <vmId>. The helper script mints a short-lived Freestyle SSH identity, opens an SSH session through vm-ssh.freestyle.sh with -R 31415:127.0.0.1:31415 (reverse-forward to the local Subrouter AI gateway on 127.0.0.1:31415) plus -L forwards for common dev ports (3000, 5173, 8000, 8080), writes a ~/.codex/config.toml inside the VM that points openai_base_url at the forwarded subrouter, then drops into a login shell. Codex launched inside the VM in that shell routes through Subrouter on the user's mac. Also opens a browser pane on the right at http://127.0.0.1:3000.
• ctrl+o opens the local-codex workflow: a normal cmux workspace at the TUI's --cwd, no SSH, plus a browser pane on the right at https://<vmId>.vm.freestyle.sh. Codex/Claude run on the mac against the local checkout; the VM is treated as a remote dev server.
• ctrl+x destroys the VM through the Freestyle SDK.
• ctrl+n on the Freestyle VMs (N) header creates a new VM from FREESTYLE_SANDBOX_SNAPSHOT.

Freestyle gateway constraint. The Freestyle SSH gateway at vm-ssh.freestyle.sh rejects -R remote port forwarding (remote port forwarding failed for listen port 31415). The --reverse-subrouter flag is therefore opt-in and works only for ordinary Linux/macOS sshd hosts.

Default path for codex inside a Freestyle VM (works today): freestyle-vm-ssh mints an ephemeral preauth Tailscale key via tsadmin api POST /tailnet/-/keys (tag tag:server, expires in 1h), runs tailscale up inside the VM under userspace networking (--tun=userspace-networking), enables tailscaled's HTTP proxy + SOCKS5 server on 127.0.0.1:1055, writes /etc/profile.d/cmux-tailnet-proxy.sh so every login shell exports HTTP_PROXY/HTTPS_PROXY/NO_PROXY, and writes ~/.codex/config.toml with openai_base_url = "http://subrouter-team.tail41290.ts.net:31415/v1". Codex inside the VM then connects to the existing subrouter-team host on the tailnet through the local proxy, so all OpenAI traffic is routed through Subrouter's account scheduling. The cmux-freestyle snapshot already ships the apt tailscale package, so first-time bring-up is ~6 s end-to-end; subsequent sessions reuse the existing state.

Disable per-call with --no-tailscale, override the subrouter URL with --subrouter-url <url> or SUBROUTER_REMOTE_URL, override the auth-key with --tailscale-authkey <key> or TAILSCALE_AUTHKEY. Today Subrouter only routes Codex, so use Codex inside the VM until Subrouter adds Claude/OpenCode support.

Helper requires sshpass on the mac (brew install hudochenkov/sshpass/sshpass) and tsadmin on PATH (skills/tsadmin/scripts/tsadmin).

GitHub auth

The snapshot builder talks only to public GitHub endpoints (/repos/manaflow-ai/cmux/releases/latest and the release-asset cmuxd-remote-checksums.txt). The unauthenticated GitHub API allows 60 requests per hour, which is fine in normal use. If a user hits a 403/429 (shared IP, CI loops, repeated rebuilds), they should set GITHUB_TOKEN (or GH_TOKEN) and the script forwards it on both the API call and the checksums download. Mention this when guiding a CI integration.

The Freestyle SDK only needs FREESTYLE_API_KEY; no GitHub credentials are required for snapshot creation. setup.sh web clones manaflow-ai/cmux anonymously, so no auth is required there either; only suggest gh auth login if a user explicitly wants git push against their own fork.

Plugging the snapshot into cmux

After the script prints the snapshot id, hand the user the env block for their cmux backend:

The FREESTYLE_API_KEY and FREESTYLE_SANDBOX_SNAPSHOT must come from the same Freestyle account. Snapshot ids from other accounts will fail to boot.

For ad-hoc smoke testing:

Inside the VM, confirm everything baked correctly:

Iterating on the repo

The whole builder is one TypeScript file at scripts/build-snapshot.ts. When updating it, keep it in lockstep with the source of truth in repo/web/scripts/build-cloud-vm-images.ts:

• Pinned agent CLI versions (CLOUD_AGENT_TOOLS).
• Default Node major and Bun version.
• Dockerfile body (freestyleBaseDockerfileContent, pythonOpenSSLCommands, toolInstallCommands, rootSetupCommands, imageSmokeTestCommands).
• Snapshot create call shape and recovery behavior (waitForFreestyleSnapshotByName).

When cmux changes any of those, bump the matching constant in cmux-freestyle, ship a release, and update the cmux release tag the script defaults to if anything in the URL/checksum contract changes.

The Freestyle CLI (npx -y freestyle vm ...) covers VM create / list / ssh / exec / delete but does not expose snapshot create. That's why this script uses the freestyle SDK directly. Do not try to replace it with a CLI-only shell script.

Rules

• Do not promise users that a shared snapshot id will work for them. It will not. Every user runs ./setup.sh once with their own Freestyle API key.
• Do not bake provider API keys, R2 credentials, or anything user-specific into the snapshot. The Dockerfile must stay reproducible from public inputs only.
• Do not point the snapshot at an unreleased cmuxd-remote. Use a published manaflow-ai/cmux release tag so SHA-256 verification has something to anchor on.
• Do not loosen the agent CLI version policy. Specs must be exact semver pins; ranges and latest are rejected on purpose so each rebuild is reproducible.
• Do not run this against the manaflow Freestyle account when iterating. Use a personal Freestyle account; manaflow's snapshot lifecycle is managed by the in-repo builder and the cmux image manifest.