diff --git a/packages/xai/src/responses/xai-responses-api.ts b/packages/xai/src/responses/xai-responses-api.ts
index e87cc455d028..db7eab4f9e67 100644
--- a/packages/xai/src/responses/xai-responses-api.ts
+++ b/packages/xai/src/responses/xai-responses-api.ts
@@ -347,6 +347,18 @@ export const xaiResponsesChunkSchema = z.union([
     item_id: z.string(),
     output_index: z.number(),
   }),
+  z.object({
+    type: z.literal('response.custom_tool_call_input.delta'),
+    item_id: z.string(),
+    output_index: z.number(),
+    delta: z.string(),
+  }),
+  z.object({
+    type: z.literal('response.custom_tool_call_input.done'),
+    item_id: z.string(),
+    output_index: z.number(),
+    input: z.string(),
+  }),
   z.object({
     type: z.literal('response.done'),
     response: xaiResponsesResponseSchema,