URL: /code/apps/forms-and-waitlists/merge · Id: `page:/code/apps/forms-and-waitlists/merge`

# Visitor.merge

> Joins two Visitor ids that belong to one person and keeps both as aliases.

POST https://api.sb/{your-domain}/visitors/{visitor}/merge

Joins two [Visitor](https://startupbuilder.dev/business/nouns/visitor) ids that belong to one person and keeps both as aliases.

- **Action class:** None
- **Approval:** Runs on its own
- **Emits:** `Visitor.merged`
- **Price:** Free

```text title="Run it · Ask"
Two visitor ids are the same laptop before and after a cookie reset: merge them.
```

```ts title="Run it · SDK"
import { $ } from 'startup-builder'

const result = await $.try.Visitor.merge({ visitor: 'https://api.sb/leaseline.app/visitors/visitor_Qa9zW1xS3e', into: 'https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j' })
```

```json title="Run it · Response"
{
  "api": "https://api.sb/leaseline.app",
  "visitor": {
    "$id": "https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j",
    "$type": "Visitor",
    "firstSeenAt": "2026-10-12T19:40:00Z"
  },
  "action": {
    "operation": "Visitor.merge",
    "mode": "try",
    "status": "done"
  }
}
```

Its Inputs, Outputs, Effects and guards quote [the hub’s `Visitor.merge`](https://startupbuilder.dev/business/nouns/visitor/merge); this page adds what each Venue honors, its limits and a worked call. It is one of the [Verbs](https://startupbuilder.dev/business/nouns/verb) of [Forms and waitlists](/code/apps/forms-and-waitlists#verbs).

## Inputs
| Name | Type | Default | Meaning |
| --- | --- | --- | --- |
| `visitor` | `Visitor` | Required | The Visitor to merge. |
| `into` | `Visitor` | Required | The Visitor that remains. |

## Outputs
| Field | Type | What `null` means |
| --- | --- | --- |
| `visitor` | `Visitor` | Never null: the remaining Visitor. |

## Effects
**Action class**

None: no approval rule names it, so it runs within its seat’s Permissions and Limits

**Modes**

- `try`: Runs every check and returns the record as it would be; nothing is stored.
- `send`: Returns a pending Action at once; `Visitor.merged` fires when it is done.
- `do`: Waits for the Action to finish and returns the record.

**Idempotency**

Only with a key: the same `Idempotency-Key` and input return the first Action, and the same key with other input returns `409`.

**Saved or shared**

Events never move or change; reads follow the alias.

**Emits**

`Visitor.merged` with `{ visitor }`

**Performed by**

[Analyst](https://startupbuilder.dev/agents/marketing/analyst)

**Price**

Free on your own account: the platform charges nothing for the call.

## On each Venue
It acts on your own records and reaches no Venue, so every account answers the same way.

## What try does
Runs every check the call meets and returns the record as it would be; nothing is stored, sent or posted.

## Refuses when
The hub sets no guard of its own on this call: it refuses only on the shared checks every write meets (a missing record, a Permission the seat lacks).

## When it waits
Returns in one response; nothing waits.

## Example
In `send` mode the call returns its pending Action at once, and `Visitor.merged` delivers the result.

**Ask**

```text
Two visitor ids are the same laptop before and after a cookie reset:
merge them.
```

**API**

```bash
curl -X POST "https://api.sb/leaseline.app/visitors/visitor_Qa9zW1xS3e/merge?mode=send" \
  -H "Authorization: Bearer $SB_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "into": "https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j"
}'
```

**CLI**

```bash
npx startup-builder do Visitor.merge --send --data '{
  "into": "https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j"
}'
```

`--send` returns the pending Action at once.

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "mode": "send",
    "code": "return await $.Visitor.merge({ into: 'https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j' })"
  }
}
```

**SDK**

```ts
import { $ } from 'startup-builder'

const result = await $.send.Visitor.merge({
  visitor: 'https://api.sb/leaseline.app/visitors/visitor_Qa9zW1xS3e',
  into: 'https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j',
})
```


```json title="Response, in send mode"
{
  "mode": "send",
  "action": {
    "$id": "https://api.sb/leaseline.app/actions/action_Sd3kQ9vT2w",
    "operation": "Visitor.merge",
    "status": "pending",
    "reason": "running"
  }
}
```

To retry, send the same `Idempotency-Key`: the retry returns the first answer for $0. A new key reads again.

## Used by
None.

## Related
[`Waitlist.join`](/code/apps/forms-and-waitlists/join) · [`Waitlist.admit`](/code/apps/forms-and-waitlists/admit) · [`Visitor.identify`](/code/apps/forms-and-waitlists/identify) · [`Form.create`](/code/apps/forms-and-waitlists/create) · [`Form.update`](/code/apps/forms-and-waitlists/update)