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

Defined in: [src/types/messages.ts:811](https://github.com/strands-agents/harness-sdk/blob/576da59fdc411b55036a7cf66d4e1659a67d4d0d/strands-ts/src/types/messages.ts#L811)