> ## 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.

# Local-only mode

> Run Stack locally without a Synth signup, then connect only when you want hosted features.

<Note>
  Documents the Stack **`0.2.0-dev.20260702.3`** local-only contract. See
  [Stack Changelog](/stack/changelog) for the current release state.
</Note>

Stack is local-first. You can install, launch, run a Codex worker, use goal mode,
inspect local threads, and run local optimizer workflows without a Synth account
or `SYNTH_API_KEY`.

## What works signed out

```bash theme={null}
stack
stack doctor
stack demo
```

Signed out local use includes:

| Surface        | Signed-out behavior                                     |
| -------------- | ------------------------------------------------------- |
| Cockpit        | Agent pane, sessions, local threads, and local receipts |
| Worker         | Codex/BYOK by default                                   |
| Goal mode      | Sidecar events, monitor status, and `/goal`             |
| Local research | Local GEPA when `synth-optimizers` is installed         |
| stackd         | Local state, thread events, exports, telemetry choices  |

Hosted panels may show connect prompts while signed out. Those prompts are not a
boot gate and do not disable local work.

## Verify the contract

Run:

```bash theme={null}
env -u SYNTH_API_KEY -u SYNTH_STAGING_API_KEY stack doctor --json
```

Look for:

```text theme={null}
local_ready=true
synth_sign_in_optional=true
worker=codex_byok
synth_worker=explicit_profile_only
```

## Telemetry

Stack telemetry uses a pseudonymous local install id. Basic DAU can be turned
off; advanced product telemetry stays off until you approve it in the TUI.
Telemetry does not include code, prompts, paths, commands, or secrets.

```bash theme={null}
stack telemetry digest
```

Use `/settings telemetry` in the cockpit to change choices.

## When to connect

Connect only when you want hosted Synth features:

* hosted SMR runs and run messages;
* Research Factories and Factory levers;
* hosted optimizer jobs and artifacts;
* Synth inference catalog, usage, and billed GLM;
* remote sync receipts and remote gardener narration for cloud work.

Next: [Connect Synth](/stack/connect-synth).