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

Defined in: [src/types/messages.ts:813](https://github.com/strands-agents/harness-sdk/blob/3bbfb60ae79b3941305737c1c5ca1e7ef639361f/strands-ts/src/types/messages.ts#L813)