Content blocks are dictionaries at runtime despite type annotations
indicating Pydantic models. Added type: ignore comments to allow
dictionary-style .get() access which works correctly at runtime.
Previously, cache_control was applied to every content block and tool call
in a message, which could exceed Anthropic's limit of 4 cache breakpoints
per request. This fix ensures cache_control is only applied to the last
block in each message type:
- Last text block in UserMessage/AssistantMessage content
- Last tool_use block when AssistantMessage has tool calls
- Only the last overall block when AssistantMessage has both content and tools
This prevents exceeding the cache breakpoint limit while maintaining
correct caching behavior.
Pyry Takala