@servicenow/sdk/docs/fluent/override-guide.md

ServiceNow SDK

---
sidebar_label: $override
tags: [$override, override, custom fields, unknown properties, x_ properties, u_ properties, extension fields, escape hatch, fluent-language]
---

# `$override` — Setting Properties Not Modeled by the API

`$override` is an escape hatch on Fluent API constructors. Use it to set fields that the typed API does not expose — typically customer-added columns (`x_`/`u_` prefixed), fields added by another application, or out-of-the-box columns that simply aren't in the API surface yet.

## When to Use

- A customer or scoped-application column on the underlying table (e.g. `x_acme_priority`, `u_team`) that the Fluent API doesn't know about.
- A field added by a separate application or plugin on the same table.
- An out-of-the-box column that exists on the platform but isn't surfaced by the API yet.

If the field **is** modeled by the API, set it directly — `$override` skips validation and IntelliSense, so it should be a last resort, not the default.

## Usage

`$override` accepts a flat object of column name → value. Values may be `string`, `boolean`, or `number`.

```typescript fluent
import { BusinessRule, Now } from '@servicenow/sdk/core'

BusinessRule({
    $id: Now.ID['set-priority-on-incident'],
    name: 'Set priority on incident',
    collection: 'incident',
    when: 'before',
    actionInsert: true,
    script: `(function() { current.priority = 1; })()`,
    $override: {
        x_acme_priority: 'high',
        u_audit_enabled: true,
        u_retry_count: 3,
    },
})
```

The keys in `$override` are the **database column names** (snake_case), not Fluent property names. They are written to the record verbatim during build.

## Notes & Gotchas

- **No type checking.** The API doesn't know these columns exist, so typos in column names or wrong value types won't be caught until the record is applied to an instance.
- **Column must exist on the target table.** If the column isn't present on the instance (in the app's own scope or a dependency), install will silently ignore it.
- **Prefer the typed API when available.** If the field is in the API surface, set it through the typed property — you keep IntelliSense, type checking, and refactor safety.
- **Reference fields:** pass the target record's sys_id as a string.

## When Not to Use

- Setting fields that *are* modeled by the API — use the defined API property.
- Setting protected sys fields like `sys_id`, `sys_updated_by`, etc