diff --git a/.castiron.stats.yml b/.castiron.stats.yml
index 9320ad8d4a..a72c5c1efb 100644
--- a/.castiron.stats.yml
+++ b/.castiron.stats.yml
@@ -1,8 +1,8 @@
 schema_version: 1
-generation_id: 894a0870-fe44-47b8-ae0e-d852e0a642a9
-openapi_spec_hash: b2c62b342b04685226037c980f2b5a7a
-openapi_transformed_spec_hash: ba44bf31326f01a1d886b7510dd9da8a
-config_hash: 4fbbbcf377bcc17646cccb9fcfbac14a
-codegen_sha: 29ea2f9fd4247a24ce57aec59ee2b9240745fcdf
-codegen_hash: dcd47732b7809ce7566ec5162d689b5320158e41aebcce2b31eaa9cd97fc4da2
-public_codegen_sha: eb1e776d29014be85225038a072a679387bda999
+generation_id: b67f6675-ad30-42fd-90ec-33d09485b9a0
+openapi_spec_hash: 32e9f9c8096eae027754def9afb89dc0
+openapi_transformed_spec_hash: a5861d7f7b67f6845c9499fdec7324a5
+config_hash: 5c00fe18ea913ed0186f9894adc02a70
+codegen_sha: 9177ce998eec68cf1d241f1efd84f8786eba92cd
+codegen_hash: 9271ebabb8723d763a7a728f3a455fb1ee4ea678e20885f891b50222f68d4def
+public_codegen_sha: 2951af18b699be3114ff5e6a3c7f7a669e7d5a76
diff --git a/api_reference/openapi.transformed.yml b/api_reference/openapi.transformed.yml
index 164fe8c284..556cdd2d9d 100644
--- a/api_reference/openapi.transformed.yml
+++ b/api_reference/openapi.transformed.yml
@@ -37968,7 +37968,6 @@ components:
           - incomplete
       required:
       - type
-      - call_id
       - output
     FunctionToolCallOutputResource:
       allOf:
@@ -63939,10 +63938,12 @@ components:
             example: fc_123
           - type: 'null'
         call_id:
-          type: string
-          maxLength: 64
-          minLength: 1
-          description: The unique ID of the function tool call generated by the model.
+          anyOf:
+          - type: string
+            maxLength: 64
+            minLength: 1
+            description: The unique ID of the function tool call generated by the model.
+          - type: 'null'
         type:
           type: string
           enum:
@@ -63994,7 +63995,6 @@ components:
       type: object
       required:
       - type
-      - call_id
       - output
       title: Function tool call output
       description: The output of a function tool call.
@@ -71251,10 +71251,12 @@ components:
             example: fc_123
           - type: 'null'
         call_id:
-          type: string
-          maxLength: 64
-          minLength: 1
-          description: The unique ID of the function tool call generated by the model.
+          anyOf:
+          - type: string
+            maxLength: 64
+            minLength: 1
+            description: The unique ID of the function tool call generated by the model.
+          - type: 'null'
         type:
           type: string
           enum:
@@ -71306,7 +71308,6 @@ components:
       type: object
       required:
       - type
-      - call_id
       - output
       title: Function tool call output
       description: The output of a function tool call.
@@ -73658,7 +73659,6 @@ components:
           - incomplete
       required:
       - type
-      - call_id
       - output
     BetaFunctionToolCallResource:
       allOf:
diff --git a/src/openai/types/beta/beta_response_function_tool_call_output_item.py b/src/openai/types/beta/beta_response_function_tool_call_output_item.py
index 61b947048f..cfe223de26 100644
--- a/src/openai/types/beta/beta_response_function_tool_call_output_item.py
+++ b/src/openai/types/beta/beta_response_function_tool_call_output_item.py
@@ -50,9 +50,6 @@ class BetaResponseFunctionToolCallOutputItem(BaseModel):
     id: str
     """The unique ID of the function call tool output."""
 
-    call_id: str
-    """The unique ID of the function tool call generated by the model."""
-
     output: Union[str, List[OutputOutputContentList]]
     """
     The output from the function call generated by your code. Can be a string or an
@@ -72,6 +69,9 @@ class BetaResponseFunctionToolCallOutputItem(BaseModel):
     agent: Optional[Agent] = None
     """The agent that produced this item."""
 
+    call_id: Optional[str] = None
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[Caller] = None
     """The execution context that produced this tool call."""
 
diff --git a/src/openai/types/beta/beta_response_input_item.py b/src/openai/types/beta/beta_response_input_item.py
index a481f80c9e..c9d6e0a73b 100644
--- a/src/openai/types/beta/beta_response_input_item.py
+++ b/src/openai/types/beta/beta_response_input_item.py
@@ -227,9 +227,6 @@ class FunctionCallOutputCallerProgram(BaseModel):
 class FunctionCallOutput(BaseModel):
     """The output of a function tool call."""
 
-    call_id: str
-    """The unique ID of the function tool call generated by the model."""
-
     output: Union[str, BetaResponseFunctionCallOutputItemList]
     """Text, image, or file output of the function tool call."""
 
@@ -245,6 +242,9 @@ class FunctionCallOutput(BaseModel):
     agent: Optional[FunctionCallOutputAgent] = None
     """The agent that produced this item."""
 
+    call_id: Optional[str] = None
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[FunctionCallOutputCaller] = None
     """The execution context that produced this tool call."""
 
diff --git a/src/openai/types/beta/beta_response_input_item_param.py b/src/openai/types/beta/beta_response_input_item_param.py
index eb27040f11..89e48c0dfe 100644
--- a/src/openai/types/beta/beta_response_input_item_param.py
+++ b/src/openai/types/beta/beta_response_input_item_param.py
@@ -226,9 +226,6 @@ class FunctionCallOutputCallerProgram(TypedDict, total=False):
 class FunctionCallOutput(TypedDict, total=False):
     """The output of a function tool call."""
 
-    call_id: Required[str]
-    """The unique ID of the function tool call generated by the model."""
-
     output: Required[Union[str, BetaResponseFunctionCallOutputItemListParam]]
     """Text, image, or file output of the function tool call."""
 
@@ -244,6 +241,9 @@ class FunctionCallOutput(TypedDict, total=False):
     agent: Optional[FunctionCallOutputAgent]
     """The agent that produced this item."""
 
+    call_id: Optional[str]
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[FunctionCallOutputCaller]
     """The execution context that produced this tool call."""
 
diff --git a/src/openai/types/beta/beta_response_input_param.py b/src/openai/types/beta/beta_response_input_param.py
index 4f81e3505f..b6bb0fe17c 100644
--- a/src/openai/types/beta/beta_response_input_param.py
+++ b/src/openai/types/beta/beta_response_input_param.py
@@ -227,9 +227,6 @@ class FunctionCallOutputCallerProgram(TypedDict, total=False):
 class FunctionCallOutput(TypedDict, total=False):
     """The output of a function tool call."""
 
-    call_id: Required[str]
-    """The unique ID of the function tool call generated by the model."""
-
     output: Required[Union[str, BetaResponseFunctionCallOutputItemListParam]]
     """Text, image, or file output of the function tool call."""
 
@@ -245,6 +242,9 @@ class FunctionCallOutput(TypedDict, total=False):
     agent: Optional[FunctionCallOutputAgent]
     """The agent that produced this item."""
 
+    call_id: Optional[str]
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[FunctionCallOutputCaller]
     """The execution context that produced this tool call."""
 
diff --git a/src/openai/types/responses/response_function_tool_call_output_item.py b/src/openai/types/responses/response_function_tool_call_output_item.py
index 3b19d3ec9b..0c1c78553a 100644
--- a/src/openai/types/responses/response_function_tool_call_output_item.py
+++ b/src/openai/types/responses/response_function_tool_call_output_item.py
@@ -36,9 +36,6 @@ class ResponseFunctionToolCallOutputItem(BaseModel):
     id: str
     """The unique ID of the function call tool output."""
 
-    call_id: str
-    """The unique ID of the function tool call generated by the model."""
-
     output: Union[str, List[OutputOutputContentList]]
     """
     The output from the function call generated by your code. Can be a string or an
@@ -55,6 +52,9 @@ class ResponseFunctionToolCallOutputItem(BaseModel):
     type: Literal["function_call_output"]
     """The type of the function tool call output. Always `function_call_output`."""
 
+    call_id: Optional[str] = None
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[Caller] = None
     """The execution context that produced this tool call."""
 
diff --git a/src/openai/types/responses/response_input_item.py b/src/openai/types/responses/response_input_item.py
index e37ea507af..1d1e06b95c 100644
--- a/src/openai/types/responses/response_input_item.py
+++ b/src/openai/types/responses/response_input_item.py
@@ -165,9 +165,6 @@ class FunctionCallOutputCallerProgram(BaseModel):
 class FunctionCallOutput(BaseModel):
     """The output of a function tool call."""
 
-    call_id: str
-    """The unique ID of the function tool call generated by the model."""
-
     output: Union[str, ResponseFunctionCallOutputItemList]
     """Text, image, or file output of the function tool call."""
 
@@ -180,6 +177,9 @@ class FunctionCallOutput(BaseModel):
     Populated when this item is returned via API.
     """
 
+    call_id: Optional[str] = None
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[FunctionCallOutputCaller] = None
     """The execution context that produced this tool call."""
 
diff --git a/src/openai/types/responses/response_input_item_param.py b/src/openai/types/responses/response_input_item_param.py
index d6192ae496..9a97f86eda 100644
--- a/src/openai/types/responses/response_input_item_param.py
+++ b/src/openai/types/responses/response_input_item_param.py
@@ -164,9 +164,6 @@ class FunctionCallOutputCallerProgram(TypedDict, total=False):
 class FunctionCallOutput(TypedDict, total=False):
     """The output of a function tool call."""
 
-    call_id: Required[str]
-    """The unique ID of the function tool call generated by the model."""
-
     output: Required[Union[str, ResponseFunctionCallOutputItemListParam]]
     """Text, image, or file output of the function tool call."""
 
@@ -179,6 +176,9 @@ class FunctionCallOutput(TypedDict, total=False):
     Populated when this item is returned via API.
     """
 
+    call_id: Optional[str]
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[FunctionCallOutputCaller]
     """The execution context that produced this tool call."""
 
diff --git a/src/openai/types/responses/response_input_param.py b/src/openai/types/responses/response_input_param.py
index c303eb9f6a..90704ed0ce 100644
--- a/src/openai/types/responses/response_input_param.py
+++ b/src/openai/types/responses/response_input_param.py
@@ -165,9 +165,6 @@ class FunctionCallOutputCallerProgram(TypedDict, total=False):
 class FunctionCallOutput(TypedDict, total=False):
     """The output of a function tool call."""
 
-    call_id: Required[str]
-    """The unique ID of the function tool call generated by the model."""
-
     output: Required[Union[str, ResponseFunctionCallOutputItemListParam]]
     """Text, image, or file output of the function tool call."""
 
@@ -180,6 +177,9 @@ class FunctionCallOutput(TypedDict, total=False):
     Populated when this item is returned via API.
     """
 
+    call_id: Optional[str]
+    """The unique ID of the function tool call generated by the model."""
+
     caller: Optional[FunctionCallOutputCaller]
     """The execution context that produced this tool call."""