The text content of this block.
Optional cacheWhen true, marks the end of this block as a cache boundary.
Optional cacheCache time-to-live for this breakpoint. Defaults to the provider's
standard 5-minute ephemeral cache. Set '1h' for the 1-hour cache —
worth the higher write premium (2x base input vs 1.25x) on a stable
prefix that is re-sent on a slow, human-paced cadence (per-turn narrator
/ companion calls minutes apart), where the 5-minute cache would expire
between turns and never produce reads. Only meaningful with
cacheBreakpoint: true.
A structured block of system prompt content with optional cache breakpoint. When
cacheBreakpointis true, providers that support prompt caching (e.g., Anthropic) will mark this block's boundary for caching.