When using the Bedrock model provider with Anthropic prompt caching enabled (CacheConfig(strategy="anthropic")), cross-request caching fails (Cache Read = 0) for single-cycle agents that receive dynamic user inputs (such as upstream JSON payloads).
Upon enabling debug logging, the SDK trace reveals:
DEBUG:strands.models.bedrock:msg_idx=<0> | added cache point to last user message
EnvironmentSDK Version: Latest (strands-agents)
Model: global anthropic claude sonnet 4.5 via Amazon Bedrock
Configuration: CacheConfig(strategy="anthropic")
Expected Behavior
Developers should be able to cache large, static system prompts or tool schemas independently of ephemeral user turns, or have an explicit mechanism via cache_config to target the system array for caching. (Note: cache_prompt is currently documented as deprecated, but moving to cache_config removed the ability to pin cache markers to system instructions).
Proposed Solution / Feature Request
Provide an option or update the Bedrock adapter logic to allow placing cache breakpoints on the system prompt array or give finer-grained control over cachePoint placement for Anthropic prompt caching on Bedrock.
When using the Bedrock model provider with Anthropic prompt caching enabled (CacheConfig(strategy="anthropic")), cross-request caching fails (Cache Read = 0) for single-cycle agents that receive dynamic user inputs (such as upstream JSON payloads).
Upon enabling debug logging, the SDK trace reveals:
DEBUG:strands.models.bedrock:msg_idx=<0> | added cache point to last user message
EnvironmentSDK Version: Latest (strands-agents)
Model: global anthropic claude sonnet 4.5 via Amazon Bedrock
Configuration: CacheConfig(strategy="anthropic")
Expected Behavior
Developers should be able to cache large, static system prompts or tool schemas independently of ephemeral user turns, or have an explicit mechanism via cache_config to target the system array for caching. (Note: cache_prompt is currently documented as deprecated, but moving to cache_config removed the ability to pin cache markers to system instructions).
Proposed Solution / Feature Request
Provide an option or update the Bedrock adapter logic to allow placing cache breakpoints on the system prompt array or give finer-grained control over cachePoint placement for Anthropic prompt caching on Bedrock.