```ts
type SystemContentBlock =
  | TextBlock
  | CachePointBlock
  | GuardContentBlock;
```

Defined in: [src/types/messages.ts:811](https://github.com/strands-agents/harness-sdk/blob/e4284b561624d906e361535ef1f1adcd5ce3461b/strands-ts/src/types/messages.ts#L811)