diff --git a/litellm/llms/anthropic/chat/transformation.py b/litellm/llms/anthropic/chat/transformation.py
index 2f11a3fccb5..46497f23410 100644
--- a/litellm/llms/anthropic/chat/transformation.py
+++ b/litellm/llms/anthropic/chat/transformation.py
@@ -653,6 +653,16 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
                 },
             )
 
+            # Extract `strict` so it can be placed at the tool top level.
+            # Anthropic only enforces `strict` when set as a sibling of
+            # `name`/`input_schema`; nested inside `input_schema` it is
+            # silently ignored. Accept it from the canonical OpenAI location
+            # (`tool.function.strict`) and, as a fallback, from the legacy
+            # nested location (`tool.function.parameters.strict`).
+            _strict: Optional[bool] = tool["function"].get("strict")
+            if _strict is None and isinstance(_input_schema, dict):
+                _strict = _input_schema.get("strict")
+
             # Anthropic requires input_schema.type to be "object". Normalize
             # schemas from external sources (MCP servers, OpenAI callers) that
             # may omit the type field or use a non-object type.
@@ -686,6 +696,9 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
             if _description is not None:
                 _tool["description"] = _description
 
+            if _strict is not None:
+                _tool["strict"] = _strict
+
             returned_tool = _tool
 
         elif tool["type"].startswith("computer_"):
diff --git a/litellm/types/llms/anthropic.py b/litellm/types/llms/anthropic.py
index 1c4d31d21ad..5d9abf65305 100644
--- a/litellm/types/llms/anthropic.py
+++ b/litellm/types/llms/anthropic.py
@@ -25,7 +25,6 @@ AnthropicInputSchema = TypedDict(
         "additionalProperties": Optional[bool],
         "required": Optional[List[str]],
         "$defs": Optional[Dict],
-        "strict": Optional[bool],
     },
     total=False,
 )
@@ -47,6 +46,7 @@ class AnthropicMessagesTool(TypedDict, total=False):
     description: str
     input_schema: Optional[AnthropicInputSchema]
     type: Literal["custom"]
+    strict: Optional[bool]
     cache_control: Optional[Union[dict, ChatCompletionCachedContent]]
     defer_loading: bool
     allowed_callers: Optional[List[str]]
@@ -686,4 +686,4 @@ ANTHROPIC_EFFORT_BETA_HEADER = "effort-2025-11-24"
 ANTHROPIC_OAUTH_TOKEN_PREFIX = "sk-ant-oat"
 ANTHROPIC_OAUTH_BETA_HEADER = "oauth-2025-04-20"
 
-ANTHROPIC_PROMPT_CACHING_SCOPE_BETA_HEADER = "prompt-caching-scope-2026-01-05"
+ANTHROPIC_PROMPT_CACHING_SCOPE_BETA_HEADER = "prompt-caching-scope-2026-01-05"
\ No newline at end of file
diff --git a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
index e38698c9100..003bdbc6c8f 100644
--- a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
+++ b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
@@ -3692,6 +3692,99 @@ def test_map_tool_helper_empty_parameters_get_default():
     assert result["input_schema"].get("properties") == {}
 
 
+def test_map_tool_helper_lifts_strict_from_function_to_tool_top_level():
+    """
+    Anthropic only enforces `strict` when set as a sibling of name/input_schema
+    on the tool object; nested inside `input_schema` it is silently ignored.
+
+    When a caller passes `strict: true` at the canonical OpenAI location
+    (`tool.function.strict`), `_map_tool_helper` must place it on the tool
+    top level and NOT inside `input_schema`.
+
+    Regression test for: tools[i].function.strict ending up nested under
+    input_schema, causing Anthropic to silently drop strict-mode enforcement.
+    """
+    config = AnthropicConfig()
+
+    tool = {
+        "type": "function",
+        "function": {
+            "name": "get_weather",
+            "description": "Get weather",
+            "parameters": {
+                "type": "object",
+                "properties": {"city": {"type": "string"}},
+                "required": ["city"],
+                "additionalProperties": False,
+            },
+            "strict": True,
+        },
+    }
+
+    result, _ = config._map_tool_helper(tool)
+    assert result is not None
+    assert result.get("strict") is True, (
+        "strict should be lifted to the tool top level so Anthropic enforces it"
+    )
+    assert "strict" not in result["input_schema"], (
+        "strict must not be nested inside input_schema (Anthropic ignores it there)"
+    )
+
+
+def test_map_tool_helper_lifts_strict_from_legacy_nested_parameters():
+    """
+    Legacy fallback: some callers and earlier code paths placed `strict` inside
+    `tool.function.parameters` (the raw input_schema). Anthropic silently
+    ignores `strict` in that location, so `_map_tool_helper` must also lift it
+    to the tool top level when found there, and strip it from input_schema.
+    """
+    config = AnthropicConfig()
+
+    tool = {
+        "type": "function",
+        "function": {
+            "name": "search",
+            "parameters": {
+                "type": "object",
+                "properties": {"q": {"type": "string"}},
+                "required": ["q"],
+                "additionalProperties": False,
+                "strict": True,
+            },
+        },
+    }
+
+    result, _ = config._map_tool_helper(tool)
+    assert result is not None
+    assert result.get("strict") is True
+    assert "strict" not in result["input_schema"]
+
+
+def test_map_tool_helper_omits_strict_when_caller_did_not_set_it():
+    """
+    When no caller-supplied `strict` is present (neither at function level nor
+    nested in parameters), the resulting tool must NOT have a strict key — we
+    don't want to inject `strict: false`/`null` and silently change behavior
+    for callers who never asked for strict mode.
+    """
+    config = AnthropicConfig()
+
+    tool = {
+        "type": "function",
+        "function": {
+            "name": "ping",
+            "parameters": {"type": "object", "properties": {}},
+        },
+    }
+
+    result, _ = config._map_tool_helper(tool)
+    assert result is not None
+    assert "strict" not in result, (
+        "strict key should be absent unless the caller opted in"
+    )
+    assert "strict" not in result["input_schema"]
+
+
 def test_extract_response_content_thinking_block_null_thinking():
     """
     Test that thinking blocks are not dropped when the 'thinking' field is null