diff --git a/litellm/litellm_core_utils/llm_cost_calc/tool_call_cost_tracking.py b/litellm/litellm_core_utils/llm_cost_calc/tool_call_cost_tracking.py
index 3744be5bc79..2863c9c15cb 100644
--- a/litellm/litellm_core_utils/llm_cost_calc/tool_call_cost_tracking.py
+++ b/litellm/litellm_core_utils/llm_cost_calc/tool_call_cost_tracking.py
@@ -2,6 +2,7 @@
 Helper utilities for tracking the cost of built-in tools.
 """
 
+from collections.abc import Mapping
 from typing import Any, Final, Literal
 
 import litellm
@@ -23,6 +24,14 @@ from litellm.types.utils import (
 )
 
 
+def _usage_reports_server_side_web_search_calls(usage: Usage) -> bool:
+    details: Final = getattr(usage, "server_side_tool_usage_details", None)
+    if not isinstance(details, Mapping):
+        return False
+    calls: Final = details.get("web_search_calls")
+    return isinstance(calls, int) and calls > 0
+
+
 class StandardBuiltInToolCostTracking:
     """
     Helper class for tracking the cost of built-in tools
@@ -351,6 +360,10 @@ class StandardBuiltInToolCostTracking:
                 # and _handle_web_search_cost() is never called.
                 if hasattr(usage, "server_tool_use") and _get_web_search_requests(usage.server_tool_use) is not None:
                     return True
+                # xAI reports usage.server_side_tool_usage_details.web_search_calls; a searched
+                # answer with no url_citation annotations has no other chat-path signal
+                if _usage_reports_server_side_web_search_calls(usage):
+                    return True
             return False
         elif isinstance(response_object, ResponsesAPIResponse):
             # response api explicitly includes web_search_call in the output
@@ -370,6 +383,8 @@ class StandardBuiltInToolCostTracking:
                 )
             ):
                 return True
+            if _usage_reports_server_side_web_search_calls(usage):
+                return True
 
         return False
 
@@ -432,7 +447,9 @@ class StandardBuiltInToolCostTracking:
         """
         output: Final = response_object.output
         for output_item in output:
-            _output_type: str | None = getattr(output_item, "type", None)
+            _output_type: str | None = (
+                output_item.get("type") if isinstance(output_item, dict) else getattr(output_item, "type", None)
+            )
             if _output_type == output_type:
                 return True
         return False
diff --git a/litellm/llms/xai/chat/transformation.py b/litellm/llms/xai/chat/transformation.py
index 9d06b609752..ae5849812bf 100644
--- a/litellm/llms/xai/chat/transformation.py
+++ b/litellm/llms/xai/chat/transformation.py
@@ -1,4 +1,4 @@
-from collections.abc import AsyncIterator, Iterator
+from collections.abc import AsyncIterator, Iterator, Mapping
 from typing import Any, Final
 
 import httpx
@@ -12,13 +12,15 @@ from litellm.litellm_core_utils.prompt_templates.common_utils import (
     strip_name_from_messages,
 )
 from litellm.llms.xai.common_utils import XAIModelInfo
+from litellm.llms.xai.cost_calculator import (
+    apply_server_side_tool_usage_details_to_usage,
+)
 from litellm.secret_managers.main import get_secret_str
 from litellm.types.llms.openai import AllMessageValues
 from litellm.types.utils import (
     Choices,
     ModelResponse,
     ModelResponseStream,
-    PromptTokensDetailsWrapper,
     Usage,
 )
 
@@ -248,7 +250,7 @@ class XAIChatConfig(OpenAIGPTConfig):
         XAI API returns empty string for finish_reason when using tools,
         so we need to fix this after the standard OpenAI transformation.
 
-        Also handles X.AI web search usage tracking by extracting num_sources_used.
+        Also handles X.AI web search usage tracking.
         """
 
         # First, let the parent class handle the standard transformation
@@ -351,25 +353,20 @@ class XAIChatConfig(OpenAIGPTConfig):
 
     def _enhance_usage_with_xai_web_search_fields(self, model_response: ModelResponse, raw_response_json: dict) -> None:
         """
-        Extract num_sources_used from X.AI response and map it to web_search_requests.
+        Copy usage.server_side_tool_usage_details from the provider usage block
+        onto model_response.usage for tool cost calculation.
         """
         if not hasattr(model_response, "usage") or model_response.usage is None:
             return
 
         usage: Final[Usage] = model_response.usage
-        num_sources_used = None
-        response_usage: Final = raw_response_json.get("usage", {})
-        if isinstance(response_usage, dict) and "num_sources_used" in response_usage:
-            num_sources_used = response_usage.get("num_sources_used")
-
-        # Map num_sources_used to web_search_requests for cost detection
-        if num_sources_used is not None and num_sources_used > 0:
-            if usage.prompt_tokens_details is None:
-                usage.prompt_tokens_details = PromptTokensDetailsWrapper()
-
-            usage.prompt_tokens_details.web_search_requests = int(num_sources_used)
-            setattr(usage, "num_sources_used", int(num_sources_used))
-            verbose_logger.debug("X.AI web search sources used: %s", num_sources_used)
+        response_usage: Final = raw_response_json.get("usage")
+        if not isinstance(response_usage, dict):
+            return
+        details: Final = response_usage.get("server_side_tool_usage_details")
+        if isinstance(details, Mapping):
+            apply_server_side_tool_usage_details_to_usage(usage, details)
+            verbose_logger.debug("X.AI server_side_tool_usage_details: %s", details)
 
     @staticmethod
     def _normalize_openai_compatible_usage_totals(
diff --git a/litellm/llms/xai/cost_calculator.py b/litellm/llms/xai/cost_calculator.py
index 384388f3300..dd77b8d5d09 100644
--- a/litellm/llms/xai/cost_calculator.py
+++ b/litellm/llms/xai/cost_calculator.py
@@ -4,14 +4,37 @@ Helper util for handling XAI-specific cost calculation
 - Handles XAI-specific reasoning token billing (billed as part of completion tokens)
 """
 
+from collections.abc import Mapping
 from typing import TYPE_CHECKING, Final
 
 from litellm.litellm_core_utils.llm_cost_calc.utils import generic_cost_per_token
-from litellm.types.utils import Usage
+from litellm.types.utils import PromptTokensDetailsWrapper, Usage
 
 if TYPE_CHECKING:
     from litellm.types.utils import ModelInfo
 
+# https://docs.x.ai/developers/pricing#tools-pricing — default when unset in model map
+_DEFAULT_WEB_SEARCH_COST_PER_CALL: Final = 5.0 / 1000.0
+
+
+def apply_server_side_tool_usage_details_to_usage(usage: Usage, details: Mapping[str, object] | None) -> None:
+    """
+    Attach server_side_tool_usage_details and mirror web_search_calls onto
+    prompt_tokens_details.web_search_requests for built-in tool cost gating.
+    """
+    if details is None:
+        return
+    usage.server_side_tool_usage_details = details  # pyright: ignore[reportAttributeAccessIssue]  # extra  # rebind-ok: extras
+    try:
+        web_search_calls: Final = int(details.get("web_search_calls") or 0)
+    except (TypeError, ValueError):
+        return
+    if web_search_calls <= 0:
+        return
+    prompt_tokens_details: Final = usage.prompt_tokens_details or PromptTokensDetailsWrapper()
+    prompt_tokens_details.web_search_requests = web_search_calls
+    usage.prompt_tokens_details = prompt_tokens_details  # rebind-ok: write details onto caller usage
+
 
 def cost_per_token(model: str, usage: Usage) -> tuple[float, float]:
     """
@@ -32,9 +55,11 @@ def cost_per_token(model: str, usage: Usage) -> tuple[float, float]:
     prompt_tokens: Final = int(getattr(usage, "prompt_tokens", 0) or 0)
     completion_tokens: Final = int(getattr(usage, "completion_tokens", 0) or 0)
     total_tokens: Final = int(getattr(usage, "total_tokens", 0) or 0)
-    reasoning_tokens = 0
-    if hasattr(usage, "completion_tokens_details") and usage.completion_tokens_details:
-        reasoning_tokens = int(getattr(usage.completion_tokens_details, "reasoning_tokens", 0) or 0)
+    reasoning_tokens: Final = (
+        int(getattr(usage.completion_tokens_details, "reasoning_tokens", 0) or 0)
+        if hasattr(usage, "completion_tokens_details") and usage.completion_tokens_details
+        else 0
+    )
 
     already_normalised: Final = total_tokens == prompt_tokens + completion_tokens
     total_completion_tokens: Final = completion_tokens if already_normalised else completion_tokens + reasoning_tokens
@@ -52,33 +77,48 @@ def cost_per_token(model: str, usage: Usage) -> tuple[float, float]:
     return prompt_cost, completion_cost
 
 
+def _web_search_cost_per_call_from_model_info(model_info: "ModelInfo") -> float:
+    """
+    Per-invocation web_search price from model_info when configured.
+
+    Prefer ``search_context_cost_per_query`` (same shape as Gemini/Anthropic web
+    search pricing in the model cost map). Fall back to current xAI list pricing.
+    """
+    search_costs: Final = model_info.get("search_context_cost_per_query")
+    if not isinstance(search_costs, Mapping):
+        return _DEFAULT_WEB_SEARCH_COST_PER_CALL
+    for key in (
+        "search_context_size_medium",
+        "search_context_size_low",
+        "search_context_size_high",
+    ):
+        value = search_costs.get(key)
+        if value is None:
+            continue
+        try:
+            cost = float(value)
+        except (TypeError, ValueError):
+            continue
+        if cost > 0:
+            return cost
+    return _DEFAULT_WEB_SEARCH_COST_PER_CALL
+
+
 def cost_per_web_search_request(usage: "Usage", model_info: "ModelInfo") -> float:
     """
     Calculate the cost of web search requests for X.AI models.
 
-    X.AI Live Search costs $25 per 1,000 sources used.
-    Each source costs $0.025.
-
-    The number of sources is stored in prompt_tokens_details.web_search_requests
-    by the transformation layer to be compatible with the existing detection system.
+    Counts invocations from usage.server_side_tool_usage_details.web_search_calls.
+    Per-call rate comes from model_info.search_context_cost_per_query when set,
+    otherwise the default xAI tools rate ($5 / 1k calls).
     """
-    # Cost per source used: $25 per 1,000 sources = $0.025 per source
-    cost_per_source: Final = 25.0 / 1000.0  # $0.025
-
-    num_sources_used = 0
-
-    if (
-        hasattr(usage, "prompt_tokens_details")
-        and usage.prompt_tokens_details is not None
-        and hasattr(usage.prompt_tokens_details, "web_search_requests")
-        and usage.prompt_tokens_details.web_search_requests is not None
-    ):
-        num_sources_used = int(usage.prompt_tokens_details.web_search_requests)
-
-    # Fallback: try to get from num_sources_used if set directly
-    elif hasattr(usage, "num_sources_used") and usage.num_sources_used is not None:
-        num_sources_used = int(usage.num_sources_used)
-
-    total_cost: Final = cost_per_source * num_sources_used
-
-    return total_cost
+    details: Final = getattr(usage, "server_side_tool_usage_details", None)
+    if not isinstance(details, Mapping):
+        return 0.0
+    try:
+        web_search_calls: Final = int(details.get("web_search_calls") or 0)
+    except (TypeError, ValueError):
+        return 0.0
+    if web_search_calls <= 0:
+        return 0.0
+    return _web_search_cost_per_call_from_model_info(model_info) * web_search_calls
diff --git a/litellm/llms/xai/responses/transformation.py b/litellm/llms/xai/responses/transformation.py
index 48fb95d9411..d79e7d4c146 100644
--- a/litellm/llms/xai/responses/transformation.py
+++ b/litellm/llms/xai/responses/transformation.py
@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Any, Final
+from typing import Any, Final
 
 import litellm
 from litellm._logging import verbose_logger
@@ -12,13 +12,6 @@ from litellm.types.llms.xai import XAIWebSearchTool, XAIXSearchTool
 from litellm.types.router import GenericLiteLLMParams
 from litellm.types.utils import LlmProviders
 
-if TYPE_CHECKING:
-    from litellm.litellm_core_utils.litellm_logging import Logging as _LiteLLMLoggingObj
-
-    LiteLLMLoggingObj = _LiteLLMLoggingObj
-else:
-    LiteLLMLoggingObj = Any
-
 
 class XAIResponsesAPIConfig(OpenAIResponsesAPIConfig):
     """
diff --git a/litellm/responses/utils.py b/litellm/responses/utils.py
index db2e515609c..1907b5aa447 100644
--- a/litellm/responses/utils.py
+++ b/litellm/responses/utils.py
@@ -1033,13 +1033,18 @@ class ResponseAPILoggingUtils:
 
     @staticmethod
     def _transform_response_api_usage_to_chat_usage(
-        usage_input: dict | ResponseAPIUsage | None,
+        usage_input: Mapping[str, object] | ResponseAPIUsage | Usage | None,
     ) -> Usage:
         """
         Transforms ResponseAPIUsage or ImageUsage to a Usage object.
 
         Both have the same spec with input_tokens, output_tokens, and
         input_tokens_details (text_tokens, image_tokens).
+
+        Usage inputs are returned as-is so re-running this helper never drops
+        fields. Non-standard provider fields (e.g. xAI's
+        server_side_tool_usage_details) are carried onto the returned Usage so
+        provider cost calculators can read them after normalization.
         """
         if usage_input is None:
             return Usage(
@@ -1047,6 +1052,10 @@ class ResponseAPILoggingUtils:
                 completion_tokens=0,
                 total_tokens=0,
             )
+        if isinstance(usage_input, Usage):
+            return usage_input
+        if isinstance(usage_input, dict) and not ResponseAPILoggingUtils._is_response_api_usage(usage_input):
+            return Usage(**usage_input)
         response_api_usage: ResponseAPIUsage
         if isinstance(usage_input, dict):
             usage_input = dict(usage_input)  # shallow copy; avoid mutating caller
@@ -1055,13 +1064,11 @@ class ResponseAPILoggingUtils:
                 usage_input["input_tokens_details"] = usage_input["input_token_details"]
             if usage_input.get("output_tokens_details") is None and "output_token_details" in usage_input:
                 usage_input["output_tokens_details"] = usage_input["output_token_details"]
-            total_tokens = usage_input.get("total_tokens")
-            if total_tokens is None:
+            if usage_input.get("total_tokens") is None:
                 input_tokens: Final = usage_input.get("input_tokens")
                 output_tokens: Final = usage_input.get("output_tokens")
-                if input_tokens is not None and output_tokens is not None:
-                    total_tokens = input_tokens + output_tokens
-                    usage_input["total_tokens"] = total_tokens
+                if isinstance(input_tokens, int) and isinstance(output_tokens, int):
+                    usage_input["total_tokens"] = input_tokens + output_tokens
             response_api_usage = ResponseAPIUsage(**usage_input)
         else:
             response_api_usage = usage_input
@@ -1089,12 +1096,27 @@ class ResponseAPILoggingUtils:
                 audio_tokens=getattr(output_tokens_details, "audio_tokens", None),
             )
 
+        extra_usage_fields: Final = {
+            key: value
+            for key, value in (response_api_usage.model_extra or {}).items()
+            if key
+            not in (
+                "input_token_details",
+                "output_token_details",
+                "prompt_tokens",
+                "completion_tokens",
+                "total_tokens",
+                "prompt_tokens_details",
+                "completion_tokens_details",
+            )
+        }
         chat_usage: Final = Usage(
             prompt_tokens=prompt_tokens,
             completion_tokens=completion_tokens,
             total_tokens=prompt_tokens + completion_tokens,
             prompt_tokens_details=prompt_tokens_details,
             completion_tokens_details=completion_tokens_details,
+            **extra_usage_fields,
         )
 
         # Preserve cost attribute if it exists on ResponseAPIUsage
diff --git a/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_tool_call_cost_tracking.py b/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_tool_call_cost_tracking.py
index 24fd3c94ee3..7f735982129 100644
--- a/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_tool_call_cost_tracking.py
+++ b/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_tool_call_cost_tracking.py
@@ -339,7 +339,7 @@ def test_get_cost_for_vertex_ai_gemini_web_search(model, custom_llm_provider):
     for url_citation annotations, not usage.prompt_tokens_details.web_search_requests.
     This causes Vertex AI grounding costs to not be tracked.
     """
-    from litellm.types.utils import PromptTokensDetailsWrapper, Usage, Choices, Message
+    from litellm.types.utils import Choices, Message, PromptTokensDetailsWrapper, Usage
 
     # Create a realistic ModelResponse like what Vertex AI returns
     response = ModelResponse(
@@ -604,3 +604,66 @@ def test_web_search_provider_prefix_fallback_does_not_misprice_non_gemini_model(
 
 # Note: File search integration test removed due to complex annotation detection logic
 # The unit tests in test_azure_assistant_cost_tracking.py provide comprehensive coverage
+
+
+def test_response_includes_output_type_reads_dict_output_items():
+    """
+    Regression: output items that fail OpenAI SDK validation (e.g. xAI web_search_call
+    items without an "action" field) stay plain dicts in the output union. The gate must
+    read their "type" key instead of returning False and skipping the web search fee.
+    """
+    from litellm.types.llms.openai import ResponsesAPIResponse
+
+    response = ResponsesAPIResponse.model_validate(
+        {
+            "id": "resp_1",
+            "created_at": 1754900000,
+            "model": "grok-4",
+            "object": "response",
+            "status": "completed",
+            "output": [{"type": "web_search_call", "id": "ws_1", "status": "completed"}],
+        }
+    )
+
+    assert isinstance(response.output[0], dict)
+    assert StandardBuiltInToolCostTracking.response_includes_output_type(
+        response_object=response, output_type="web_search_call"
+    )
+    assert not StandardBuiltInToolCostTracking.response_includes_output_type(
+        response_object=response, output_type="file_search_call"
+    )
+
+
+def test_web_search_gate_reads_server_side_tool_usage_details_without_citations():
+    """
+    Regression: xAI chat responses bridged from the Responses API only carry
+    usage.server_side_tool_usage_details; a searched answer with no url_citation
+    annotations must still be billed for its web search calls.
+    """
+    from litellm.llms.xai.cost_calculator import _DEFAULT_WEB_SEARCH_COST_PER_CALL
+    from litellm.types.utils import Usage
+
+    usage = Usage(
+        prompt_tokens=10,
+        completion_tokens=20,
+        total_tokens=30,
+        server_side_tool_usage_details={"web_search_calls": 3},
+    )
+    response = ModelResponse(model="xai/grok-4.5")
+
+    assert StandardBuiltInToolCostTracking.response_object_includes_web_search_call(
+        response_object=response, usage=usage
+    )
+    assert not StandardBuiltInToolCostTracking.response_object_includes_web_search_call(
+        response_object=response,
+        usage=Usage(prompt_tokens=10, completion_tokens=20, total_tokens=30),
+    )
+
+    cost = StandardBuiltInToolCostTracking.get_cost_for_built_in_tools(
+        model="xai/grok-4.5",
+        response_object=response,
+        usage=usage,
+        custom_llm_provider="xai",
+        standard_built_in_tools_params=None,
+    )
+    assert cost == 3 * _DEFAULT_WEB_SEARCH_COST_PER_CALL
diff --git a/tests/test_litellm/llms/xai/responses/test_xai_responses_transformation.py b/tests/test_litellm/llms/xai/responses/test_xai_responses_transformation.py
index fb98dc0a917..871613c9c9a 100644
--- a/tests/test_litellm/llms/xai/responses/test_xai_responses_transformation.py
+++ b/tests/test_litellm/llms/xai/responses/test_xai_responses_transformation.py
@@ -9,14 +9,22 @@ Source: litellm/llms/xai/responses/transformation.py
 
 import os
 import sys
+from unittest.mock import MagicMock
 
 sys.path.insert(0, os.path.abspath("../../../../.."))
 
 import pytest
 
+import litellm
 from litellm.llms.xai.responses.transformation import XAIResponsesAPIConfig
-from litellm.types.llms.openai import ResponsesAPIOptionalRequestParams
-from litellm.types.utils import LlmProviders
+from litellm.responses.utils import ResponseAPILoggingUtils
+from litellm.types.llms.openai import (
+    ResponseAPIUsage,
+    ResponseCompletedEvent,
+    ResponsesAPIOptionalRequestParams,
+    ResponsesAPIResponse,
+)
+from litellm.types.utils import LlmProviders, Usage
 from litellm.utils import ProviderConfigManager
 
 
@@ -31,43 +39,29 @@ class TestXAIResponsesAPITransformation:
         )
 
         assert config is not None, "Config should not be None for XAI provider"
-        assert isinstance(
-            config, XAIResponsesAPIConfig
-        ), f"Expected XAIResponsesAPIConfig, got {type(config)}"
-        assert (
-            config.custom_llm_provider == LlmProviders.XAI
-        ), "custom_llm_provider should be XAI"
+        assert isinstance(config, XAIResponsesAPIConfig), f"Expected XAIResponsesAPIConfig, got {type(config)}"
+        assert config.custom_llm_provider == LlmProviders.XAI, "custom_llm_provider should be XAI"
 
     def test_code_interpreter_container_field_removed(self):
         """Test that container field is removed from code_interpreter tools"""
         config = XAIResponsesAPIConfig()
 
-        params = ResponsesAPIOptionalRequestParams(
-            tools=[{"type": "code_interpreter", "container": {"type": "auto"}}]
-        )
+        params = ResponsesAPIOptionalRequestParams(tools=[{"type": "code_interpreter", "container": {"type": "auto"}}])
 
-        result = config.map_openai_params(
-            response_api_optional_params=params, model="grok-4-fast", drop_params=False
-        )
+        result = config.map_openai_params(response_api_optional_params=params, model="grok-4-fast", drop_params=False)
 
         assert "tools" in result
         assert len(result["tools"]) == 1
         assert result["tools"][0]["type"] == "code_interpreter"
-        assert (
-            "container" not in result["tools"][0]
-        ), "Container field should be removed"
+        assert "container" not in result["tools"][0], "Container field should be removed"
 
     def test_instructions_parameter_dropped(self):
         """Test that instructions parameter is dropped for XAI"""
         config = XAIResponsesAPIConfig()
 
-        params = ResponsesAPIOptionalRequestParams(
-            instructions="You are a helpful assistant.", temperature=0.7
-        )
+        params = ResponsesAPIOptionalRequestParams(instructions="You are a helpful assistant.", temperature=0.7)
 
-        result = config.map_openai_params(
-            response_api_optional_params=params, model="grok-4-fast", drop_params=False
-        )
+        result = config.map_openai_params(response_api_optional_params=params, model="grok-4-fast", drop_params=False)
 
         assert "instructions" not in result, "Instructions should be dropped"
         assert result.get("temperature") == 0.7, "Other params should be preserved"
@@ -88,25 +82,15 @@ class TestXAIResponsesAPITransformation:
 
         # Test with default XAI API base
         url = config.get_complete_url(api_base=None, litellm_params={})
-        assert (
-            url == "https://api.x.ai/v1/responses"
-        ), f"Expected XAI responses endpoint, got {url}"
+        assert url == "https://api.x.ai/v1/responses", f"Expected XAI responses endpoint, got {url}"
 
         # Test with custom api_base
-        custom_url = config.get_complete_url(
-            api_base="https://custom.x.ai/v1", litellm_params={}
-        )
-        assert (
-            custom_url == "https://custom.x.ai/v1/responses"
-        ), f"Expected custom endpoint, got {custom_url}"
+        custom_url = config.get_complete_url(api_base="https://custom.x.ai/v1", litellm_params={})
+        assert custom_url == "https://custom.x.ai/v1/responses", f"Expected custom endpoint, got {custom_url}"
 
         # Test with trailing slash
-        url_with_slash = config.get_complete_url(
-            api_base="https://api.x.ai/v1/", litellm_params={}
-        )
-        assert (
-            url_with_slash == "https://api.x.ai/v1/responses"
-        ), "Should handle trailing slash"
+        url_with_slash = config.get_complete_url(api_base="https://api.x.ai/v1/", litellm_params={})
+        assert url_with_slash == "https://api.x.ai/v1/responses", "Should handle trailing slash"
 
     def test_web_search_tool_transformation(self):
         """Test that web_search tools are transformed to XAI format"""
@@ -167,9 +151,7 @@ class TestXAIResponsesAPITransformation:
         config = XAIResponsesAPIConfig()
 
         params = ResponsesAPIOptionalRequestParams(
-            tools=[
-                {"type": "web_search", "excluded_domains": ["example.com", "test.com"]}
-            ]
+            tools=[{"type": "web_search", "excluded_domains": ["example.com", "test.com"]}]
         )
 
         result = config.map_openai_params(
@@ -309,3 +291,115 @@ class TestXAIResponsesAPITransformation:
         # Verify function tool is unchanged
         assert result["tools"][3]["type"] == "function"
         assert result["tools"][3]["name"] == "get_weather"
+
+
+class TestXAIResponsesWebSearchBilling:
+    """Web search billing must not change the client-visible Responses usage schema."""
+
+    _TOOL_DETAILS = {
+        "web_search_calls": 2,
+        "x_search_calls": 0,
+        "code_interpreter_calls": 0,
+        "file_search_calls": 0,
+        "mcp_calls": 0,
+        "document_search_calls": 0,
+    }
+
+    def _raw_response_json(self, include_web_search: bool) -> dict:
+        web_search_output = (
+            [{
+                "type": "web_search_call",
+                "id": "ws_1",
+                "status": "completed",
+                "action": {"type": "search", "query": "grok"},
+            }] if include_web_search else []
+        )
+        tool_usage = {"server_side_tool_usage_details": self._TOOL_DETAILS} if include_web_search else {}
+        return {
+            "id": "resp_1",
+            "object": "response",
+            "created_at": 1754900000,
+            "model": "grok-4",
+            "status": "completed",
+            "parallel_tool_calls": True,
+            "tool_choice": "auto",
+            "tools": [],
+            "top_p": 1.0,
+            "output": web_search_output
+            + [
+                {
+                    "type": "message",
+                    "id": "msg_1",
+                    "role": "assistant",
+                    "status": "completed",
+                    "content": [{"type": "output_text", "text": "grok says hi", "annotations": []}],
+                }
+            ],
+            "usage": {
+                "input_tokens": 100,
+                "output_tokens": 20,
+                "total_tokens": 120,
+                "input_tokens_details": {"cached_tokens": 0},
+                "output_tokens_details": {"reasoning_tokens": 0},
+                **tool_usage,
+            },
+        }
+
+    def _transform(self, include_web_search: bool) -> ResponsesAPIResponse:
+        raw_response = MagicMock()
+        raw_response.json.return_value = self._raw_response_json(include_web_search)
+        raw_response.text = "raw"
+        raw_response.headers = {}
+        return XAIResponsesAPIConfig().transform_response_api_response(
+            model="grok-4", raw_response=raw_response, logging_obj=MagicMock()
+        )
+
+    def test_response_usage_keeps_responses_api_schema(self):
+        response = self._transform(include_web_search=True)
+
+        assert isinstance(response.usage, ResponseAPIUsage)
+        assert response.usage.input_tokens == 100
+        assert response.usage.output_tokens == 20
+        assert response.usage.model_extra["server_side_tool_usage_details"] == self._TOOL_DETAILS
+
+    def test_bridged_usage_keeps_tool_details_for_billing(self):
+        response = self._transform(include_web_search=True)
+
+        bridged = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(response.usage)
+
+        assert isinstance(bridged, Usage)
+        assert bridged.prompt_tokens == 100
+        assert bridged.completion_tokens == 20
+        assert getattr(bridged, "server_side_tool_usage_details") == self._TOOL_DETAILS
+
+    def test_completion_cost_bills_web_search_calls(self):
+        with_search = litellm.completion_cost(
+            completion_response=self._transform(include_web_search=True),
+            model="xai/grok-4",
+            custom_llm_provider="xai",
+        )
+        without_search = litellm.completion_cost(
+            completion_response=self._transform(include_web_search=False),
+            model="xai/grok-4",
+            custom_llm_provider="xai",
+        )
+
+        assert with_search - without_search == pytest.approx(2 * 5.0 / 1000.0)
+
+    def test_streaming_terminal_event_keeps_schema_and_details(self):
+        parsed_chunk = {
+            "type": "response.completed",
+            "sequence_number": 7,
+            "response": self._raw_response_json(include_web_search=True),
+        }
+
+        event = XAIResponsesAPIConfig().transform_streaming_response(
+            model="grok-4", parsed_chunk=parsed_chunk, logging_obj=MagicMock()
+        )
+
+        assert isinstance(event, ResponseCompletedEvent)
+        assert isinstance(event.response.usage, ResponseAPIUsage)
+        assert event.response.usage.input_tokens == 100
+
+        bridged = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(event.response.usage)
+        assert getattr(bridged, "server_side_tool_usage_details") == self._TOOL_DETAILS
diff --git a/tests/test_litellm/llms/xai/test_xai_chat_transformation.py b/tests/test_litellm/llms/xai/test_xai_chat_transformation.py
index 5c1f0f704d7..eac5b89e4f3 100644
--- a/tests/test_litellm/llms/xai/test_xai_chat_transformation.py
+++ b/tests/test_litellm/llms/xai/test_xai_chat_transformation.py
@@ -5,6 +5,9 @@ sys.path.insert(
     0, os.path.abspath("../../../..")
 )  # Adds the parent directory to the system path
 
+import pytest
+
+import litellm
 from litellm.llms.xai.chat.transformation import XAIChatConfig
 from litellm.types.utils import (
     CompletionTokensDetailsWrapper,
@@ -135,3 +138,65 @@ class TestXAIUsageNormalization:
         XAIChatConfig._normalize_openai_compatible_usage_totals(usage)
 
         assert usage["total_tokens"] == 200
+
+
+class TestXAIChatWebSearchBilling:
+    _TOOL_DETAILS = {
+        "web_search_calls": 3,
+        "x_search_calls": 0,
+        "code_interpreter_calls": 0,
+        "file_search_calls": 0,
+        "mcp_calls": 0,
+        "document_search_calls": 0,
+    }
+
+    @staticmethod
+    def _response_with_usage() -> ModelResponse:
+        response = ModelResponse(model="grok-4")
+        setattr(
+            response,
+            "usage",
+            Usage(prompt_tokens=100, completion_tokens=20, total_tokens=120),
+        )
+        return response
+
+    def test_enhance_copies_details_and_mirrors_web_search_requests(self):
+        response = self._response_with_usage()
+
+        XAIChatConfig()._enhance_usage_with_xai_web_search_fields(
+            response,
+            {"usage": {"server_side_tool_usage_details": self._TOOL_DETAILS}},
+        )
+
+        usage = response.usage
+        assert getattr(usage, "server_side_tool_usage_details") == self._TOOL_DETAILS
+        assert usage.prompt_tokens_details is not None
+        assert usage.prompt_tokens_details.web_search_requests == 3
+
+    def test_enhance_noop_without_details(self):
+        response = self._response_with_usage()
+
+        XAIChatConfig()._enhance_usage_with_xai_web_search_fields(
+            response, {"usage": {"prompt_tokens": 100}}
+        )
+
+        assert response.usage.prompt_tokens_details is None
+        assert getattr(response.usage, "server_side_tool_usage_details", None) is None
+
+    def test_completion_cost_bills_chat_web_search_calls(self):
+        billed = self._response_with_usage()
+        XAIChatConfig()._enhance_usage_with_xai_web_search_fields(
+            billed,
+            {"usage": {"server_side_tool_usage_details": self._TOOL_DETAILS}},
+        )
+
+        with_search = litellm.completion_cost(
+            completion_response=billed, model="xai/grok-4", custom_llm_provider="xai"
+        )
+        without_search = litellm.completion_cost(
+            completion_response=self._response_with_usage(),
+            model="xai/grok-4",
+            custom_llm_provider="xai",
+        )
+
+        assert with_search - without_search == pytest.approx(3 * 5.0 / 1000.0)
diff --git a/tests/test_litellm/llms/xai/test_xai_cost_calculator.py b/tests/test_litellm/llms/xai/test_xai_cost_calculator.py
index 32141bead0e..df6f4d3edd8 100644
--- a/tests/test_litellm/llms/xai/test_xai_cost_calculator.py
+++ b/tests/test_litellm/llms/xai/test_xai_cost_calculator.py
@@ -17,7 +17,16 @@ sys.path.insert(
     0, os.path.abspath("../../..")
 )  # Adds the parent directory to the system path
 
-from litellm.llms.xai.cost_calculator import cost_per_token, cost_per_web_search_request
+from litellm.litellm_core_utils.llm_cost_calc.tool_call_cost_tracking import (
+    StandardBuiltInToolCostTracking,
+)
+from litellm.llms.xai.cost_calculator import (
+    _DEFAULT_WEB_SEARCH_COST_PER_CALL,
+    _web_search_cost_per_call_from_model_info,
+    apply_server_side_tool_usage_details_to_usage,
+    cost_per_token,
+    cost_per_web_search_request,
+)
 
 
 class TestXAICostCalculator:
@@ -354,76 +363,53 @@ class TestXAICostCalculator:
         assert math.isclose(prompt_cost, expected_prompt_cost, rel_tol=1e-10)
         assert math.isclose(completion_cost, expected_completion_cost, rel_tol=1e-10)
 
-    def test_web_search_cost_calculation(self):
-        """Test web search cost calculation for X.AI models."""
-        # Test with web_search_requests in prompt_tokens_details (primary path)
-        usage = Usage(
-            prompt_tokens=100,
-            completion_tokens=50,
-            total_tokens=150,
-            prompt_tokens_details=PromptTokensDetailsWrapper(
-                text_tokens=100,
-                web_search_requests=3,  # 3 sources used
-            ),
+    def test_web_search_cost_via_server_side_tool_usage_details(self):
+        """usage.server_side_tool_usage_details.web_search_calls at default $5/1k."""
+        usage = Usage(prompt_tokens=100, completion_tokens=50, total_tokens=150)
+        setattr(
+            usage,
+            "server_side_tool_usage_details",
+            {
+                "web_search_calls": 3,
+                "x_search_calls": 0,
+                "code_interpreter_calls": 0,
+                "file_search_calls": 0,
+                "mcp_calls": 0,
+                "document_search_calls": 0,
+            },
         )
 
         web_search_cost = cost_per_web_search_request(usage=usage, model_info={})
+        assert math.isclose(web_search_cost, 3 * (5.0 / 1000.0), rel_tol=1e-10)
 
-        # Expected cost: 3 sources * $0.025 per source = $0.075
-        expected_cost = 3 * (25.0 / 1000.0)  # 3 * $0.025
-
-        assert math.isclose(web_search_cost, expected_cost, rel_tol=1e-10)
-        assert math.isclose(web_search_cost, 0.075, rel_tol=1e-10)
-
-    def test_web_search_cost_fallback_calculation(self):
-        """Test web search cost calculation using fallback num_sources_used."""
-        # Test fallback: num_sources_used on usage object
-        usage = Usage(
-            prompt_tokens=100,
-            completion_tokens=50,
-            total_tokens=150,
+    def test_web_search_cost_uses_model_info_search_context_pricing(self):
+        usage = Usage(prompt_tokens=10, completion_tokens=5, total_tokens=15)
+        setattr(usage, "server_side_tool_usage_details", {"web_search_calls": 2})
+        model_info = {
+            "search_context_cost_per_query": {
+                "search_context_size_medium": 0.01,
+            }
+        }
+        web_search_cost = cost_per_web_search_request(
+            usage=usage, model_info=model_info
         )
-        # Manually set num_sources_used (as done by transformation layer)
-        setattr(usage, "num_sources_used", 5)
+        assert math.isclose(web_search_cost, 0.02, rel_tol=1e-10)
 
-        web_search_cost = cost_per_web_search_request(usage=usage, model_info={})
+    def test_web_search_cost_zero_without_details(self):
+        usage = Usage(prompt_tokens=100, completion_tokens=50, total_tokens=150)
+        assert cost_per_web_search_request(usage=usage, model_info={}) == 0.0
 
-        # Expected cost: 5 sources * $0.025 per source = $0.125
-        expected_cost = 5 * (25.0 / 1000.0)  # 5 * $0.025
-
-        assert math.isclose(web_search_cost, expected_cost, rel_tol=1e-10)
-        assert math.isclose(web_search_cost, 0.125, rel_tol=1e-10)
-
-    def test_web_search_no_sources_used(self):
-        """Test web search cost calculation when no sources are used."""
-        usage = Usage(
-            prompt_tokens=100,
-            completion_tokens=50,
-            total_tokens=150,
-            prompt_tokens_details=PromptTokensDetailsWrapper(
-                text_tokens=100,
-                web_search_requests=0,  # No web search
-            ),
+    def test_apply_details_sets_web_search_requests_for_cost_gate(self):
+        usage = Usage(prompt_tokens=10, completion_tokens=5, total_tokens=15)
+        apply_server_side_tool_usage_details_to_usage(
+            usage, {"web_search_calls": 2, "x_search_calls": 0}
         )
-
-        web_search_cost = cost_per_web_search_request(usage=usage, model_info={})
-
-        # Expected cost: 0 sources * $0.025 per source = $0.0
-        assert web_search_cost == 0.0
-
-    def test_web_search_cost_without_prompt_tokens_details(self):
-        """Test web search cost calculation when prompt_tokens_details is None."""
-        usage = Usage(
-            prompt_tokens=100,
-            completion_tokens=50,
-            total_tokens=150,
+        assert usage.prompt_tokens_details is not None
+        assert usage.prompt_tokens_details.web_search_requests == 2
+        assert StandardBuiltInToolCostTracking.response_object_includes_web_search_call(
+            response_object=object(), usage=usage
         )
 
-        web_search_cost = cost_per_web_search_request(usage=usage, model_info={})
-
-        # Expected cost: No web search data = $0.0
-        assert web_search_cost == 0.0
-
     def test_grok_4_20_beta_reasoning_cost_calculation(self):
         """Test cost calculation for grok-4.20-beta-0309-reasoning model."""
         usage = Usage(prompt_tokens=100, completion_tokens=200, total_tokens=300)
@@ -499,3 +485,112 @@ class TestXAICostCalculator:
 
         assert math.isclose(prompt_cost, expected_prompt_cost, rel_tol=1e-10)
         assert math.isclose(completion_cost, expected_completion_cost, rel_tol=1e-10)
+
+
+class TestXAIWebSearchCostHelpers:
+    """Focused coverage for web_search / tool-usage helpers in cost_calculator.py."""
+
+    def test_apply_details_noop_when_details_none(self):
+        usage = Usage(prompt_tokens=1, completion_tokens=1, total_tokens=2)
+        apply_server_side_tool_usage_details_to_usage(usage, None)
+        assert getattr(usage, "server_side_tool_usage_details", None) is None
+
+    def test_apply_details_sets_attr_but_skips_mirror_when_web_search_zero(self):
+        usage = Usage(prompt_tokens=1, completion_tokens=1, total_tokens=2)
+        details = {"web_search_calls": 0, "x_search_calls": 3}
+        apply_server_side_tool_usage_details_to_usage(usage, details)
+        assert getattr(usage, "server_side_tool_usage_details") == details
+        assert (
+            usage.prompt_tokens_details is None
+            or usage.prompt_tokens_details.web_search_requests is None
+        )
+
+    def test_apply_details_skips_mirror_when_web_search_calls_invalid(self):
+        usage = Usage(prompt_tokens=1, completion_tokens=1, total_tokens=2)
+        details = {"web_search_calls": "not-a-number"}
+        apply_server_side_tool_usage_details_to_usage(usage, details)
+        assert getattr(usage, "server_side_tool_usage_details") == details
+        assert usage.prompt_tokens_details is None
+
+    def test_apply_details_updates_existing_prompt_tokens_details(self):
+        usage = Usage(
+            prompt_tokens=1,
+            completion_tokens=1,
+            total_tokens=2,
+            prompt_tokens_details=PromptTokensDetailsWrapper(cached_tokens=7),
+        )
+        apply_server_side_tool_usage_details_to_usage(usage, {"web_search_calls": 4})
+        assert usage.prompt_tokens_details is not None
+        assert usage.prompt_tokens_details.cached_tokens == 7
+        assert usage.prompt_tokens_details.web_search_requests == 4
+
+    def test_web_search_cost_per_call_default_when_model_info_empty(self):
+        assert (
+            _web_search_cost_per_call_from_model_info({})
+            == _DEFAULT_WEB_SEARCH_COST_PER_CALL
+        )
+
+    def test_web_search_cost_per_call_prefers_medium_over_low(self):
+        model_info = {
+            "search_context_cost_per_query": {
+                "search_context_size_low": 0.001,
+                "search_context_size_medium": 0.009,
+            }
+        }
+        assert _web_search_cost_per_call_from_model_info(model_info) == 0.009
+
+    def test_web_search_cost_per_call_falls_back_to_low_then_high(self):
+        assert (
+            _web_search_cost_per_call_from_model_info(
+                {"search_context_cost_per_query": {"search_context_size_low": 0.003}}
+            )
+            == 0.003
+        )
+        assert (
+            _web_search_cost_per_call_from_model_info(
+                {"search_context_cost_per_query": {"search_context_size_high": 0.007}}
+            )
+            == 0.007
+        )
+
+    def test_web_search_cost_per_call_ignores_zero_and_invalid_values(self):
+        assert (
+            _web_search_cost_per_call_from_model_info(
+                {
+                    "search_context_cost_per_query": {
+                        "search_context_size_medium": 0,
+                        "search_context_size_low": "bad",
+                    }
+                }
+            )
+            == _DEFAULT_WEB_SEARCH_COST_PER_CALL
+        )
+
+    def test_cost_per_web_search_request_zero_when_details_not_mapping(self):
+        usage = Usage(prompt_tokens=1, completion_tokens=1, total_tokens=2)
+        setattr(usage, "server_side_tool_usage_details", "invalid")
+        assert cost_per_web_search_request(usage=usage, model_info={}) == 0.0
+
+    def test_cost_per_web_search_request_zero_when_web_search_calls_invalid(self):
+        usage = Usage(prompt_tokens=1, completion_tokens=1, total_tokens=2)
+        setattr(
+            usage,
+            "server_side_tool_usage_details",
+            {"web_search_calls": object()},
+        )
+        assert cost_per_web_search_request(usage=usage, model_info={}) == 0.0
+
+    def test_cost_per_web_search_request_zero_when_web_search_calls_zero(self):
+        usage = Usage(prompt_tokens=1, completion_tokens=1, total_tokens=2)
+        setattr(
+            usage,
+            "server_side_tool_usage_details",
+            {"web_search_calls": 0, "x_search_calls": 5},
+        )
+        assert cost_per_web_search_request(usage=usage, model_info={}) == 0.0
+
+    def test_cost_per_web_search_request_uses_default_rate_without_model_pricing(self):
+        usage = Usage(prompt_tokens=1, completion_tokens=1, total_tokens=2)
+        setattr(usage, "server_side_tool_usage_details", {"web_search_calls": 4})
+        cost = cost_per_web_search_request(usage=usage, model_info={})
+        assert math.isclose(cost, 4 * _DEFAULT_WEB_SEARCH_COST_PER_CALL, rel_tol=1e-10)
diff --git a/tests/test_litellm/responses/test_responses_utils.py b/tests/test_litellm/responses/test_responses_utils.py
index 0141cf5d96a..2b9e6d34828 100644
--- a/tests/test_litellm/responses/test_responses_utils.py
+++ b/tests/test_litellm/responses/test_responses_utils.py
@@ -1,21 +1,16 @@
 import base64
-import json
 import os
 import sys
 from unittest.mock import MagicMock, patch
 
 import pytest
-from fastapi.testclient import TestClient
 
-sys.path.insert(
-    0, os.path.abspath("../../..")
-)  # Adds the parent directory to the system path
+sys.path.insert(0, os.path.abspath("../../.."))  # Adds the parent directory to the system path
 
 import litellm
-from litellm.llms.base_llm.responses.transformation import BaseResponsesAPIConfig
 from litellm.llms.openai.responses.transformation import OpenAIResponsesAPIConfig
 from litellm.responses.utils import ResponseAPILoggingUtils, ResponsesAPIRequestUtils
-from litellm.types.llms.openai import ResponsesAPIOptionalRequestParams
+from litellm.types.llms.openai import ResponseAPIUsage, ResponsesAPIOptionalRequestParams
 from litellm.types.utils import Usage
 
 
@@ -54,9 +49,7 @@ class TestResponsesAPIRequestUtils:
         # Setup
         model = "gpt-4o"
         config = OpenAIResponsesAPIConfig()
-        optional_params = ResponsesAPIOptionalRequestParams(
-            {"temperature": 0.7, "unsupported_param": "value"}
-        )
+        optional_params = ResponsesAPIOptionalRequestParams({"temperature": 0.7, "unsupported_param": "value"})
 
         # Execute and Assert
         with pytest.raises(litellm.UnsupportedParamsError) as excinfo:
@@ -90,9 +83,7 @@ class TestResponsesAPIRequestUtils:
         assert result == {"temperature": 0.7}
 
     @pytest.mark.parametrize("request_drop_params", [None, False])
-    def test_get_optional_params_responses_api_still_raises_without_drop(
-        self, monkeypatch, request_drop_params
-    ):
+    def test_get_optional_params_responses_api_still_raises_without_drop(self, monkeypatch, request_drop_params):
         """Absent or False request-level drop_params must not suppress the unsupported-param error"""
         monkeypatch.setattr(litellm, "drop_params", False)
         config = OpenAIResponsesAPIConfig()
@@ -119,9 +110,7 @@ class TestResponsesAPIRequestUtils:
         }
 
         # Execute
-        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(
-            params
-        )
+        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(params)
 
         # Assert
         assert "temperature" in result
@@ -147,40 +136,31 @@ class TestResponsesAPIRequestUtils:
         )
 
         # Execute
-        result = ResponsesAPIRequestUtils.decode_previous_response_id_to_original_previous_response_id(
-            encoded_id
-        )
+        result = ResponsesAPIRequestUtils.decode_previous_response_id_to_original_previous_response_id(encoded_id)
 
         # Assert
         assert result == original_response_id
 
         # Test with a non-encoded ID
         plain_id = "resp_xyz789"
-        result_plain = ResponsesAPIRequestUtils.decode_previous_response_id_to_original_previous_response_id(
-            plain_id
-        )
+        result_plain = ResponsesAPIRequestUtils.decode_previous_response_id_to_original_previous_response_id(plain_id)
         assert result_plain == plain_id
 
     def test_update_responses_api_response_id_with_model_id_handles_dict(self):
         """Ensure _update_responses_api_response_id_with_model_id works with dict input"""
         responses_api_response = {"id": "resp_abc123"}
         litellm_metadata = {"model_info": {"id": "gpt-4o"}}
-        updated = (
-            ResponsesAPIRequestUtils._update_responses_api_response_id_with_model_id(
-                responses_api_response=responses_api_response,
-                custom_llm_provider="openai",
-                litellm_metadata=litellm_metadata,
-            )
+        updated = ResponsesAPIRequestUtils._update_responses_api_response_id_with_model_id(
+            responses_api_response=responses_api_response,
+            custom_llm_provider="openai",
+            litellm_metadata=litellm_metadata,
         )
         assert updated["id"] != "resp_abc123"
-        decoded = ResponsesAPIRequestUtils._decode_responses_api_response_id(
-            updated["id"]
-        )
+        decoded = ResponsesAPIRequestUtils._decode_responses_api_response_id(updated["id"])
         assert decoded.get("response_id") == "resp_abc123"
         assert decoded.get("model_id") == "gpt-4o"
         assert decoded.get("custom_llm_provider") == "openai"
 
-
     def test_update_responses_api_response_id_with_model_id_is_idempotent_for_litellm_ids(self):
         raw = "resp_" + "a" * 48
         litellm_metadata = {"model_info": {"id": "model-123"}}
@@ -207,9 +187,7 @@ class TestResponsesAPIRequestUtils:
             model_id=None,
             container_id="cntr_upstream_abc",
         )
-        assert "None" not in base64.b64decode(
-            encoded.replace("cntr_", "").encode("utf-8")
-        ).decode("utf-8")
+        assert "None" not in base64.b64decode(encoded.replace("cntr_", "").encode("utf-8")).decode("utf-8")
         decoded = ResponsesAPIRequestUtils._decode_container_id(encoded)
         assert decoded.get("custom_llm_provider") == "azure"
         assert decoded.get("model_id") is None
@@ -217,12 +195,8 @@ class TestResponsesAPIRequestUtils:
 
     def test_decode_container_id_legacy_literal_none_model_id(self):
         """IDs encoded before the None fix should decode without a bogus model_id."""
-        legacy_inner = (
-            "litellm:custom_llm_provider:azure;model_id:None;container_id:cntr_x"
-        )
-        legacy_id = "cntr_" + base64.b64encode(legacy_inner.encode("utf-8")).decode(
-            "utf-8"
-        )
+        legacy_inner = "litellm:custom_llm_provider:azure;model_id:None;container_id:cntr_x"
+        legacy_id = "cntr_" + base64.b64encode(legacy_inner.encode("utf-8")).decode("utf-8")
         decoded = ResponsesAPIRequestUtils._decode_container_id(legacy_id)
         assert decoded.get("model_id") is None
         assert decoded.get("custom_llm_provider") == "azure"
@@ -264,19 +238,14 @@ class TestResponseAPILoggingUtils:
         }
 
         # Execute
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         # Assert
         assert isinstance(result, Usage)
         assert result.prompt_tokens == 10
         assert result.completion_tokens == 20
         assert result.total_tokens == 30
-        assert (
-            result.prompt_tokens_details
-            and result.prompt_tokens_details.cached_tokens == 2
-        )
+        assert result.prompt_tokens_details and result.prompt_tokens_details.cached_tokens == 2
 
     def test_transform_response_api_usage_with_none_values(self):
         """Test transformation handles None values properly"""
@@ -289,9 +258,7 @@ class TestResponseAPILoggingUtils:
         }
 
         # Execute
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         # Assert
         assert result.prompt_tokens == 0
@@ -310,9 +277,7 @@ class TestResponseAPILoggingUtils:
         }
 
         # Execute
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         # Assert
         assert result.prompt_tokens == 15
@@ -349,9 +314,7 @@ class TestResponseAPILoggingUtils:
         }
 
         # Execute
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         # Assert - verify basic token counts
         assert isinstance(result, Usage)
@@ -386,9 +349,7 @@ class TestResponseAPILoggingUtils:
             },
         }
 
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         assert result.prompt_tokens_details is not None
         assert result.prompt_tokens_details.cache_write_tokens == 10059
@@ -417,9 +378,7 @@ class TestResponseAPILoggingUtils:
         }
 
         # Execute
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         # Assert - all token detail types should be preserved
         assert result.prompt_tokens_details is not None
@@ -451,9 +410,7 @@ class TestResponseAPILoggingUtils:
             },
         }
 
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         assert result.prompt_tokens_details is not None
         assert result.prompt_tokens_details.text_tokens == 8
@@ -475,9 +432,7 @@ class TestResponseAPILoggingUtils:
             "output_token_details": {"text_tokens": 2, "audio_tokens": 98},
         }
 
-        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(
-            usage
-        )
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
 
         assert result.prompt_tokens_details is not None
         assert result.prompt_tokens_details.text_tokens == 10
@@ -487,6 +442,93 @@ class TestResponseAPILoggingUtils:
         assert result.completion_tokens_details.text_tokens == 20
         assert result.completion_tokens_details.audio_tokens is None
 
+    def test_transform_response_api_usage_carries_extra_provider_fields(self):
+        """Non-standard usage fields (e.g. xAI tool details) must survive chat normalization."""
+        details = {"web_search_calls": 2, "x_search_calls": 0}
+        usage = ResponseAPIUsage(
+            input_tokens=100,
+            output_tokens=20,
+            total_tokens=120,
+            server_side_tool_usage_details=details,
+        )
+
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
+
+        assert isinstance(result, Usage)
+        assert result.prompt_tokens == 100
+        assert result.completion_tokens == 20
+        assert getattr(result, "server_side_tool_usage_details") == details
+
+    def test_transform_response_api_usage_ignores_chat_shaped_extras(self):
+        """Gemini image usage carries chat-shaped keys as extras; they must not collide with explicit kwargs."""
+        usage = ResponseAPIUsage(
+            input_tokens=35,
+            output_tokens=1716,
+            total_tokens=1751,
+            prompt_tokens=35,
+            prompt_tokens_details={"image_tokens": 5, "text_tokens": 30},
+            completion_tokens=1716,
+            completion_tokens_details={"image_tokens": 1120, "text_tokens": 596},
+            server_side_tool_usage_details={"web_search_calls": 1},
+        )
+
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
+
+        assert result.prompt_tokens == 35
+        assert result.completion_tokens == 1716
+        assert getattr(result, "server_side_tool_usage_details") == {"web_search_calls": 1}
+
+    def test_transform_already_chat_usage_passthrough_keeps_tool_details(self):
+        """Re-running the bridge on an already-converted chat Usage must not drop fields."""
+        details = {"web_search_calls": 2, "x_search_calls": 0}
+        usage = Usage(
+            prompt_tokens=100,
+            completion_tokens=20,
+            total_tokens=120,
+            prompt_tokens_details={"web_search_requests": 2},
+        )
+        setattr(usage, "server_side_tool_usage_details", details)
+
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
+
+        assert result is usage
+        assert getattr(result, "server_side_tool_usage_details") == details
+        assert result.prompt_tokens_details is not None
+        assert result.prompt_tokens_details.web_search_requests == 2
+
+    def test_transform_chat_shaped_usage_dict_keeps_tool_details(self):
+        """Streaming chat bridge dumps already-converted Usage as a prompt_tokens dict."""
+        details = {
+            "web_search_calls": 3,
+            "x_search_calls": 0,
+            "code_interpreter_calls": 0,
+            "file_search_calls": 0,
+            "mcp_calls": 0,
+            "document_search_calls": 0,
+            "image_generation_calls": 0,
+        }
+        usage = {
+            "prompt_tokens": 50,
+            "completion_tokens": 10,
+            "total_tokens": 60,
+            "prompt_tokens_details": {"web_search_requests": 3, "cached_tokens": 8},
+            "completion_tokens_details": {"reasoning_tokens": 4},
+            "server_side_tool_usage_details": details,
+        }
+
+        result = ResponseAPILoggingUtils._transform_response_api_usage_to_chat_usage(usage)
+
+        assert isinstance(result, Usage)
+        assert result.prompt_tokens == 50
+        assert result.completion_tokens == 10
+        assert result.total_tokens == 60
+        assert getattr(result, "server_side_tool_usage_details") == details
+        assert result.prompt_tokens_details is not None
+        assert result.prompt_tokens_details.web_search_requests == 3
+        assert result.prompt_tokens_details.cached_tokens == 8
+        assert result.completion_tokens_details is not None
+        assert result.completion_tokens_details.reasoning_tokens == 4
+
 
 class TestResponsesAPIProviderSpecificParams:
     """
@@ -503,9 +545,7 @@ class TestResponsesAPIProviderSpecificParams:
         }
 
         # Should not raise any exception
-        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(
-            params
-        )
+        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(params)
         assert "temperature" in result
 
     def test_provider_specific_params_no_crash_with_openai(self):
@@ -517,9 +557,7 @@ class TestResponsesAPIProviderSpecificParams:
         }
 
         # Should not raise any exception
-        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(
-            params
-        )
+        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(params)
         assert "temperature" in result
 
     def test_provider_specific_params_no_crash_with_vertex_ai(self):
@@ -531,9 +569,7 @@ class TestResponsesAPIProviderSpecificParams:
         }
 
         # Should not raise any exception
-        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(
-            params
-        )
+        result = ResponsesAPIRequestUtils.get_requested_response_api_optional_param(params)
         assert "temperature" in result