diff --git a/litellm/integrations/anthropic_cache_control_hook.py b/litellm/integrations/anthropic_cache_control_hook.py
index f9b9238b181..036b9d033cd 100644
--- a/litellm/integrations/anthropic_cache_control_hook.py
+++ b/litellm/integrations/anthropic_cache_control_hook.py
@@ -318,26 +318,22 @@ class AnthropicCacheControlHook(CustomPromptManagement):
 
         A tool carries its mark at the top level (Anthropic shape) or under ``function``
         (OpenAI shape). A top-level ``cache_control`` is Anthropic's automatic caching,
-        which places one breakpoint of its own on top of the explicit ones. Marks the
-        client sends through the ``extra_body`` envelope of ``request_kwargs`` reach the
-        wire too and count the same way. Callers pass only the tools whose mark reaches
-        the provider on their path.
+        which places one breakpoint of its own on top of the explicit ones. The
+        ``extra_body`` envelope of ``request_kwargs`` is merged over the request on the
+        wire, so a ``tools`` or ``cache_control`` it carries replaces the direct value
+        and is counted in its place. Callers pass only the tools whose mark reaches the
+        provider on their path.
         """
         extra_body: Final = (
             _validated_object_mapping(AnthropicCacheControlHook._request_value(request_kwargs, "extra_body")) or {}
         )
-        automatic_blocks: Final = sum(
-            1 for control in (cache_control, extra_body.get("cache_control")) if control is not None
-        )
-        tool_blocks: Final = sum(
-            1
-            for tool in (*(tools or ()), *(_validated_object_list(extra_body.get("tools")) or ()))
-            if _tool_carries_cache_breakpoint(tool)
-        )
+        wire_cache_control: Final = extra_body.get("cache_control", cache_control)
+        wire_tools: Final = _validated_object_list(extra_body["tools"]) if "tools" in extra_body else tools
+        tool_blocks: Final = sum(1 for tool in wire_tools or () if _tool_carries_cache_breakpoint(tool))
         envelope_blocks: Final = AnthropicCacheControlHook.count_request_cache_breakpoints(
             _validated_object_list(extra_body.get("messages")) or (), extra_body.get("system")
         )
-        return automatic_blocks + tool_blocks + envelope_blocks
+        return int(wire_cache_control is not None) + tool_blocks + envelope_blocks
 
     @staticmethod
     def _blocks_reserved_outside_messages(
diff --git a/tests/test_litellm/integrations/test_anthropic_cache_control_hook.py b/tests/test_litellm/integrations/test_anthropic_cache_control_hook.py
index 78aee3048ca..041b00c6c70 100644
--- a/tests/test_litellm/integrations/test_anthropic_cache_control_hook.py
+++ b/tests/test_litellm/integrations/test_anthropic_cache_control_hook.py
@@ -2596,6 +2596,42 @@ class TestConfiguredInjectionPointsSurviveClientMarks:
         _, result_sys = self._inject(self._marked_user_turns(3), kwargs)
         assert result_sys == expected_system
 
+    @pytest.mark.parametrize(
+        "params,tools,marked_turns,injected",
+        [
+            ({"extra_body": {"tools": [MARKED_TOOL_TOP_LEVEL]}}, [MARKED_TOOL_TOP_LEVEL], 2, 1),
+            ({"extra_body": {"tools": [UNMARKED_TOOL]}}, [MARKED_TOOL_TOP_LEVEL], 3, 1),
+            ({"extra_body": {"tools": [MARKED_TOOL_TOP_LEVEL]}}, [UNMARKED_TOOL], 3, 0),
+            ({"extra_body": {"cache_control": EPHEMERAL}, "cache_control": EPHEMERAL}, None, 2, 1),
+        ],
+        ids=["same_marked_tool_both_ways", "extra_body_unmarks", "extra_body_marks", "root_cache_control_both_ways"],
+    )
+    def test_chat_cap_counts_extra_body_fields_in_place_of_the_direct_ones(self, params, tools, marked_turns, injected):
+        """``extra_body`` is merged over the request on the wire, so its ``tools`` and
+        ``cache_control`` replace the direct ones rather than adding to them."""
+        messages = [{"role": "system", "content": "sys"}, *self._marked_user_turns(marked_turns)]
+        params = {"cache_control_injection_points": copy.deepcopy(self.CONFIGURED), **copy.deepcopy(params)}
+        self._seed(params, copy.deepcopy(messages), tools=tools)
+        processed = self._chat(params, copy.deepcopy(messages))
+        assert _count_cache_control(processed) == marked_turns + injected
+
+    @pytest.mark.parametrize(
+        "kwargs,tools,marked_turns,expected_system",
+        [
+            ({"extra_body": {"tools": [MARKED_V1_TOOL]}}, [MARKED_V1_TOOL], 2, [{"type": "text", "text": "sys", "cache_control": EPHEMERAL}]),
+            ({"extra_body": {"tools": [UNMARKED_V1_TOOL]}}, [MARKED_V1_TOOL], 3, [{"type": "text", "text": "sys", "cache_control": EPHEMERAL}]),
+            ({"extra_body": {"tools": [MARKED_V1_TOOL]}}, [UNMARKED_V1_TOOL], 3, "sys"),
+            ({"extra_body": {"cache_control": EPHEMERAL}, "cache_control": EPHEMERAL}, None, 2, [{"type": "text", "text": "sys", "cache_control": EPHEMERAL}]),
+        ],
+        ids=["same_marked_tool_both_ways", "extra_body_unmarks", "extra_body_marks", "root_cache_control_both_ways"],
+    )
+    def test_v1_messages_cap_counts_extra_body_fields_in_place_of_the_direct_ones(
+        self, kwargs, tools, marked_turns, expected_system
+    ):
+        kwargs = {"cache_control_injection_points": copy.deepcopy(self.CONFIGURED), **copy.deepcopy(kwargs)}
+        _, result_sys = self._inject(self._marked_user_turns(marked_turns), kwargs, tools=tools)
+        assert result_sys == expected_system
+
     def test_v1_messages_automatic_defaults_stand_down_for_root_cache_control(self, monkeypatch):
         monkeypatch.setattr(litellm, "enable_anthropic_prompt_caching", True)
         root_cache_control = {"type": "ephemeral"}