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

Defined in: [src/types/messages.ts:813](https://github.com/strands-agents/harness-sdk/blob/e5b6b6dd62a46604b7c30b1f508f575018a3c443/strands-ts/src/types/messages.ts#L813)