feat: support Bedrock prompt cache TTL

[SharpLu]

Summary

Adds Bedrock prompt cache TTL support to the agents Bedrock runtime path. Bedrock cache checkpoints now allow an optional ttl value (5m or 1h), and callers can pass promptCacheTtl so the generated cachePoint blocks include that TTL.

When promptCacheTtl is omitted, no TTL is sent and Bedrock keeps its default 5-minute prompt cache behavior.

Changes

• Add promptCacheTtl?: "5m" | "1h" to Bedrock Anthropic input/client options
• Pass the TTL into addBedrockCacheControl() from the graph Bedrock options
• Preserve cachePoint.ttl through Bedrock message conversion for user, assistant, and system blocks
• Add tests for default behavior, 5m, 1h, and message conversion

References

• AWS CachePointBlock API reference: https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_CachePointBlock.html
• AWS Bedrock prompt caching guide: https://docs.aws.amazon.com/bedrock/latest/userguide/prompt-caching.html
• AWS announcement for 1-hour prompt caching: https://aws.amazon.com/about-aws/whats-new/2026/01/amazon-bedrock-one-hour-duration-prompt-caching/
• LibreChat config PR: feat: add Bedrock prompt cache TTL config LibreChat#12875

Testing

• npm test -- --runInBand src/messages/cache.test.ts src/llm/bedrock/llm.spec.ts
• npm run build

[SharpLu]

Hey @danny-avila, friendly bump — just rebased onto main (v3.1.79), tests pass.

This is the runtime half of danny-avila/LibreChat#12875: it threads the optional promptCacheTtl from BedrockAnthropicClientOptions through addBedrockCacheControl so the inserted cachePoint blocks carry the TTL. Defaults stay unchanged when no TTL is provided, and we strip 1h for models that don't support it (Nova, non-4.5 Claude) to avoid AWS validation errors.

Both PRs need to land together for the feature to work end-to-end.

Thanks for taking a look!