> ## 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.20260703.2`** local-first, hosted-connect, and nightly install behavior.
  See [Stack Changelog](/stack/changelog) for release state.
</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 -s -- --channel nightly
```

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.

The local worker remains Codex/BYOK by default. Missing Synth auth should show a
hosted-feature connect prompt, not a boot blocker. See [Local-only mode](/stack/local-only).

## 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.

## Connect hosted Synth when needed

Hosted SMR, Research Factories, hosted optimizers, remote sync, and Synth
inference require a Synth key:

```bash theme={null}
stack auth open signin
stack auth verify --json
```

See [Connect Synth](/stack/connect-synth) and [Hosted ops](/stack/hosted-ops).

## 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 has two local telemetry tiers. Basic DAU is on by default and can be
turned off. Advanced feature usage and session length stay off until you accept
the prompt. Telemetry never includes your code, prompts, paths, commands, or
secrets.

```bash theme={null}
stack telemetry digest     # see local counts and upload cursor state
```

In the TUI, use `/settings telemetry` to change choices.

## Next

* [Goal mode & monitor](/stack/goal-mode) — sidecar feed for long runs
* [Local-only mode](/stack/local-only) — what works without a Synth account
* [Connect Synth](/stack/connect-synth) — optional hosted auth
* [Hosted ops](/stack/hosted-ops) — SMR, Factories, and remote sync
* [Cockpit controls](/stack/cockpit) — full keyboard reference
* [Hosted inference](/stack/inference) — free aux and billed GLM.
* [Optimizers](/stack/optimizers) — run GEPA on your tasks from the cockpit.