> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usesynth.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Quickstart

> Download Stack, run the local loop, and configure it with the Codex coding agent.

<Note>
  Documents Stack **`0.2.0-dev.20260701.1`** (dev/nightly). See
  [Stack Changelog](/stack/changelog) for install and goal-mode updates.
</Note>

Stack runs locally without a Synth signup. This gets you from download to a working
cockpit, then connects it to the Codex coding agent.

## Install

**Nightly (macOS, Apple Silicon):**

```bash theme={null}
curl -fsSL https://stack.usesynth.ai/install.sh | sh
```

Or download the tarball from the
[releases page](https://github.com/synth-laboratories/stack/releases) and run the
bundled installer.

**From source** (requires [Bun](https://bun.sh)):

```bash theme={null}
git clone https://github.com/synth-laboratories/stack
cd stack && bun install
bun run src/main.ts
```

## The signed-out loop

No account required:

```bash theme={null}
stack            # launch the cockpit
stack demo       # run a local demo and write a receipt
stack doctor     # check your environment
stack update     # check for a newer nightly
```

`stack demo` writes a local, reproducible receipt — that is the whole first-win loop,
offline.

## Configure with Codex

Stack drives a coding agent as its harness. The default harness is Codex:

```bash theme={null}
export STACK_HARNESS=codex
export STACK_CODEX_COMMAND=codex     # path to your codex binary, if not on PATH
stack
```

Stack ships Codex skills that teach the agent how to operate inside the cockpit —
install them once:

* `stack-local-setup` — local environment + first-run wiring
* `synth-via-stack` — how to reach hosted Synth features from Stack
* `stack-agent-bridge` — the typed stackd surfaces the agent uses

Run `stack doctor` to confirm the harness, Codex command, and stackd health are all
green before starting a session.

## Goal mode (sidecar monitor)

For long Codex runs, read [Goal mode & monitor](/stack/goal-mode) — Sidecar events
(`e`), sidecar thread (`t`), and agent tape (`a`).

## Telemetry

Stack sends anonymous usage telemetry, on by default, to improve the product. It
never includes your code, prompts, paths, commands, or secrets.

```bash theme={null}
stack telemetry status     # see what's on and why
stack telemetry off        # disable (also STACK_TELEMETRY=0 or DO_NOT_TRACK=1)
```

## Next

* [Goal mode & monitor](/stack/goal-mode) — sidecar feed for long runs
* [Cockpit controls](/stack/cockpit) — full keyboard reference
* [Hosted inference](/stack/inference) — sign in and call Nemotron 3 Ultra.
* [Optimizers](/stack/optimizers) — run GEPA on your tasks from the cockpit.