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

Defined in: [src/types/messages.ts:813](https://github.com/strands-agents/harness-sdk/blob/c3b403c7c41f9fe7b7e704bb8f8d2e6698d3b97e/strands-ts/src/types/messages.ts#L813)