### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### What happened?

When a Bedrock Converse request includes `guardrailConfig`, any `cache_control` marker on the **trailing user message(s)** is silently lost during request transformation, so no `cachePoint` block is emitted for the latest message.

This affects both ways of placing the marker:

- `cache_control_injection_points` with `{location: message, index: -1}`, and - `cache_control` set directly on the last user message / its content blocks.

Because a typical chat request ends with a user message, every ordinary turn loses its conversation-prefix breakpoint whenever guardrails are enabled. Requests ending in a tool result are unaffected (tool messages are not rewritten), so cache behavior differs between plain turns and tool-loop turns of the same conversation.

**Root cause**

`AmazonConverseConfig._convert_consecutive_user_messages_to_guarded_text` (`litellm/llms/bedrock/chat/converse_transformation.py`) rewrites trailing user messages so the guardrail evaluates only the latest turn:

- list content: `{"type": "text", ...}` → a **new** `…