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

# Pin a source

> Pin the recipe a source reuses so one customer's run can't drift the starting point other runs draw from — or unpin to return to "latest working recipe".

```http theme={null}
POST https://app.vern.so/api/v1/sources/{source}/pin
```

By default the [managed agent](/migration-api/concepts#the-managed-agent) reuses
a source's **most-recent working recipe** as the starting point for each new
`generate` run, adapting only what the customer's upload changed. Because every
successful generate writes a fresh recipe, that "latest" naturally **drifts**.

Pinning fixes the starting point to one known-good run's recipe. Pinned runs read
it read-only — they don't promote their adapted recipe back to "latest" — so one
customer's run can't move the baseline other runs build on. See
[Reuse and pinning](/migration-api/concepts#reuse-and-pinning).

`{source}` is the source **name** (URL-encode it if it contains spaces).

## Authentication

Requires an `x-api-key` header. See [Authentication](/migration-api/authentication).

## Request body

<ParamField body="run_id" type="string (uuid) | null" required>
  The run whose recipe to pin as this source's reuse recipe. The run must belong
  to your account and have produced a usable recipe (a `generate` or `update` run
  that reached a preview or executed). Pass **`null`** to unpin and return to
  "latest working recipe" drift.
</ParamField>

## Response

`200 OK`

```json theme={null}
{
  "source": "Salesforce",
  "pinned_recipe_run_id": "d4c3b2a1-9f8e-47d6-b5a4-c3d2e1f0a9b8"
}
```

When you unpin, `pinned_recipe_run_id` comes back `null`.

## Errors

| Status | Meaning                                                                                                             |
| ------ | ------------------------------------------------------------------------------------------------------------------- |
| `400`  | Malformed body.                                                                                                     |
| `401`  | API key missing or invalid.                                                                                         |
| `404`  | The source name isn't in your account, or `run_id` isn't a run in your account.                                     |
| `409`  | The source name is ambiguous (two sources share it — rename one), or the run never produced a usable recipe to pin. |
| `429`  | Rate limit hit — back off and retry.                                                                                |
| `500`  | Server error.                                                                                                       |

## Example

```bash theme={null}
# Pin a known-good run's recipe as the source's baseline
curl -X POST https://app.vern.so/api/v1/sources/Salesforce/pin \
  -H "x-api-key: $VERN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "run_id": "d4c3b2a1-9f8e-47d6-b5a4-c3d2e1f0a9b8" }'

# Unpin — back to latest-working-recipe drift
curl -X POST https://app.vern.so/api/v1/sources/Salesforce/pin \
  -H "x-api-key: $VERN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "run_id": null }'
```

## Next

* [Core concepts → Reuse and pinning](/migration-api/concepts#reuse-and-pinning)
* [Start a run](/migration-api/start-a-run) — what produces a recipe to pin.