diff --git a/litellm/llms/anthropic/cost_calculation.py b/litellm/llms/anthropic/cost_calculation.py
index 3882d8f978c..7cdca3fb00c 100644
--- a/litellm/llms/anthropic/cost_calculation.py
+++ b/litellm/llms/anthropic/cost_calculation.py
@@ -3,7 +3,7 @@ Helper util for handling anthropic-specific cost calculation
 - e.g.: prompt caching
 """
 
-from typing import TYPE_CHECKING, Optional, Tuple
+from typing import TYPE_CHECKING, Any, Optional, Tuple
 
 from litellm.litellm_core_utils.llm_cost_calc.utils import (
     _get_token_base_cost,
@@ -17,6 +17,23 @@ if TYPE_CHECKING:
 import litellm
 
 
+def _get_web_search_requests(server_tool_use: Any) -> Optional[int]:
+    """
+    Tolerantly read ``web_search_requests`` from a ``server_tool_use`` value
+    that may be ``None``, a ``dict``, a ``ServerToolUse`` pydantic instance,
+    or any other object supporting attribute access.
+
+    See https://github.com/BerriAI/litellm/issues/26153 — ``stream_chunk_builder``
+    historically left this as a plain ``dict``, which broke direct attribute
+    access in cost calculation.
+    """
+    if server_tool_use is None:
+        return None
+    if isinstance(server_tool_use, dict):
+        return server_tool_use.get("web_search_requests")
+    return getattr(server_tool_use, "web_search_requests", None)
+
+
 def _compute_cache_only_cost(model_info: "ModelInfo", usage: "Usage") -> float:
     """
     Return only the cache-related portion of the prompt cost (cache read + cache write).
@@ -110,11 +127,12 @@ def get_cost_for_anthropic_web_search(
     if model_info is None:
         return 0.0
 
-    if (
-        usage is None
-        or usage.server_tool_use is None
-        or usage.server_tool_use.web_search_requests is None
-    ):
+    if usage is None:
+        return 0.0
+    web_search_requests = _get_web_search_requests(
+        getattr(usage, "server_tool_use", None)
+    )
+    if web_search_requests is None:
         return 0.0
 
     ## Get the cost per web search request
@@ -128,5 +146,5 @@ def get_cost_for_anthropic_web_search(
         return 0.0
 
     ## Calculate the total cost
-    total_cost = cost_per_web_search_request * usage.server_tool_use.web_search_requests
+    total_cost = cost_per_web_search_request * web_search_requests
     return total_cost