When someone sends a DM to the bot and isn't on the allowlist — whether it's a new user or an existing user on a new channel — nanobot automatically replies with a **pairing code** (like `ABCD-EFGH`) that expires in 10 minutes. To grant them access:
```text
/pairing approve ABCD-EFGH
```
To see who's waiting, use `/pairing`. To remove someone later, use `/pairing revoke <user_id>` — you can find user IDs in the `/pairing list` output.
See [Configuration: Pairing](./configuration.md#pairing) for the full setup guide.
The response shows the current session's model and preset, plus the available preset names. Named presets come from the top-level `modelPresets` config and are the recommended way to configure model choices. `default` is always available and represents the model settings from direct `agents.defaults.*` fields.
Preset names come from the top-level `modelPresets` config. Switching affects only the current session and persists the selection in that session, so later turns keep using it across process restarts. It does not rewrite `config.json`, does not change other sessions, and does not alter an in-progress turn's captured model. Sessions without a saved selection follow `agents.defaults.modelPreset` (or the implicit `default` preset when it is omitted). See [Configuration: Model presets](./configuration.md#model-presets) for setup details.
Periodic background checks are driven by `HEARTBEAT.md` in your workspace (`~/.nanobot/workspace/HEARTBEAT.md`). When `nanobot gateway` starts, it registers a protected heartbeat cron job by default. Every 30 minutes, that job checks the file; if it finds tasks under `## Active Tasks`, the agent executes them and delivers only results that pass the notification gate to your most recently active chat channel. If there are no active tasks, or the result is routine with nothing useful to report, the heartbeat is skipped silently.
Use heartbeat for recurring checks that should usually stay quiet. User-created cron jobs are different: they run as scheduled turns in the chat/session where they were created and normally deliver the result back to that channel.
The agent can also manage this file itself - ask it to "add a periodic background check" or "check this periodically but only notify me if something changes" and it will update `HEARTBEAT.md` for you. Completed tasks should be deleted from the file, not moved to another section.
You can change the interval or disable the built-in heartbeat in `~/.nanobot/config.json`:
```json
{
"gateway":{
"heartbeat":{
"enabled":true,
"intervalS":1800
}
}
}
```
The heartbeat job is visible in `cron(action="list")` as `heartbeat`, but it is system-managed and cannot be removed with the `cron` tool. To stop it, set `gateway.heartbeat.enabled` to `false` and restart the gateway.
> **Note:** The gateway must be running (`nanobot gateway`) and you must have chatted with the bot at least once so it knows which channel to deliver to.
