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Closes #37042 --- `AnthropicPromptCachingMiddleware` was unconditionally setting top-level `cache_control` in `model_settings` for any `ChatAnthropic` subclass. That field is direct-Anthropic-API only — `ChatAnthropicBedrock` (which subclasses `ChatAnthropic` and passed the existing `isinstance` gate) errored with `cache_control: Extra inputs are not permitted`. Investigating that surfaced a related regression: PR #35967 also deleted the block-level `cache_control` injection in `_get_request_payload`, which silently disabled caching entirely for non-direct subclasses (Bedrock had been falling back to in-block breakpoints). This restores both paths. ## Changes - Add `_is_direct_anthropic_llm_type` predicate that allowlists `_llm_type == "anthropic-chat"`. Both the middleware's `_supports_automatic_caching` and the new branch in `ChatAnthropic._get_request_payload` route through it, so any subclass that overrides `_llm_type` (Bedrock today, future direct-API variants tomorrow) is treated as non-direct by default. Replaces the prior substring-matching denylist on `"bedrock"`/`"vertex"`. - Restore `_collect_code_execution_tool_ids`, `_is_code_execution_related_block`, and a new `_apply_cache_control_to_last_eligible_block` helper in `chat_models`. For non-direct subclasses, `_get_request_payload` now pops `cache_control` from kwargs and walks messages newest-to-oldest, attaching the breakpoint to the last block that isn't `code_execution`-related (Anthropic forbids breakpoints on those). - Emit `UserWarning` when `cache_control` is requested but every candidate block is `code_execution`-related — previously a silent drop. - `AnthropicPromptCachingMiddleware._apply_caching` now sets the top-level `cache_control` only when `_supports_automatic_caching(request.model)`. System-message and tool-definition breakpoints continue to apply for all `ChatAnthropic` subclasses, since those are accepted by every transport. - Note: `ChatAnthropicVertex` does not subclass `ChatAnthropic` (it lives in `langchain-google-vertexai` and ships its own `_get_request_payload`), so the chat-models changes here only affect Bedrock. The middleware-side gate covers Vertex implicitly via the `isinstance(request.model, ChatAnthropic)` check that already excludes it.