fix(anthropic): move a prompt_cache_breakpoint under a tool's function to the tool so Converse caches it

Bedrock Converse reads only a tool's top-level cache_control, so a breakpoint written under function was dropped there. It now becomes the tool's top-level mark on every Claude route, unless the client already marked the function

litellm/llms/anthropic/chat/prompt_cache_breakpoints.py

@@ -151,11 +151,25 @@ def _marked_message(index: int, message: object, mark: _Mark) -> object:
     }
 
 
+def _with_function_breakpoint_hoisted(tool: _Fields) -> _Fields:
+    """Converse reads only a tool's top-level mark, so a breakpoint written under ``function`` moves up."""
+    function: Final = _fields(tool.get("function"))
+    marker: Final = None if function is None else function.get("prompt_cache_breakpoint")
+    if function is None or marker is None:
+        return tool
+    keeps_client_mark: Final = function.get("cache_control") is not None or "prompt_cache_breakpoint" in tool
+    return {
+        **tool,
+        "function": {key: value for key, value in function.items() if key != "prompt_cache_breakpoint"},
+        **({} if keeps_client_mark else {"prompt_cache_breakpoint": marker}),
+    }
+
+
 def _marked_tool(index: int, tool: object, mark: _Mark) -> object:
     fields: Final = _fields(tool)
     if fields is None:
         return tool
-    marked: Final = mark(("tools", index), fields)
+    marked: Final = mark(("tools", index), _with_function_breakpoint_hoisted(fields))
     function: Final = _fields(marked.get("function"))
     return marked if function is None else {**marked, "function": mark(("tools", index, "function"), function)}
 

tests/integration/providers/test_claude_chat_prompt_cache_breakpoint_wire.py

@@ -192,6 +192,21 @@ def test_breakpoint_becomes_a_cache_mark_on_the_same_block(gateway: Gateway, pro
     assert _labels(provider, request) == [_expected(provider, site, marker)]
 
 
+@pytest.mark.parametrize("provider", _PROVIDERS)
+def test_breakpoint_under_a_tool_function_marks_the_tool(gateway: Gateway, provider: Provider) -> None:
+    marker: Final = new_marker()
+    function: Final = TOOL["function"]
+    assert isinstance(function, dict), TOOL
+    tool: Final[dict[str, JsonValue]] = {**TOOL, "function": {**function, "prompt_cache_breakpoint": _EXPLICIT}}
+    with wire_server(lambda request: _respond(provider, request)) as wire, gateway.scenario() as scenario:
+        model: Final = _deployment(gateway, scenario, wire, provider)
+        status, _, text = post_chat(gateway, {**_body(model, marker, _marked(())), "tools": [tool]})
+        assert status == 200, text
+        request: Final = _only_request(wire)
+    assert b"prompt_cache_breakpoint" not in request.body, request.body
+    assert _labels(provider, request) == [_expected(provider, "tool", marker)]
+
+
 def test_breakpoint_ttl_claude_supports_is_kept(gateway: Gateway) -> None:
     marker: Final = new_marker()
     marks: Final = _marked(("user_part",), {"prompt_cache_breakpoint": {"mode": "explicit", "ttl": "1h"}})

tests/unit/llms/anthropic/chat/test_prompt_cache_breakpoints.py

@@ -78,7 +78,7 @@ def test_breakpoints_become_cache_control_on_every_block_that_carries_one():
     ]
     assert list(result.tools or ()) == [
         {"type": "function", "function": {"name": "a"}, "cache_control": _EPHEMERAL},
-        {"type": "function", "function": {"name": "b", "cache_control": _EPHEMERAL}},
+        {"type": "function", "function": {"name": "b"}, "cache_control": _EPHEMERAL},
     ]