fix: remove stream_options from xAI provider to fix Grok 4 API errors

- Removed stream_options: { include_usage: true } from XAIHandler
- Grok models do not support the stream_options parameter
- This fixes API errors when using Grok 4 model
- Updated tests to reflect the change

Fixes #6211

src/api/providers/__tests__/xai.spec.ts

@@ -276,7 +276,6 @@ describe("XAIHandler", () => {
 				temperature: 0,
 				messages: expect.arrayContaining([{ role: "system", content: systemPrompt }]),
 				stream: true,
-				stream_options: { include_usage: true },
 			}),
 		)
 	})

src/api/providers/xai.ts

@@ -48,13 +48,13 @@ export class XAIHandler extends BaseProvider implements SingleCompletionHandler
 		const { id: modelId, info: modelInfo, reasoning } = this.getModel()
 
 		// Use the OpenAI-compatible API.
+		// Note: Grok models don't support stream_options parameter
 		const stream = await this.client.chat.completions.create({
 			model: modelId,
 			max_tokens: modelInfo.maxTokens,
 			temperature: this.options.modelTemperature ?? XAI_DEFAULT_TEMPERATURE,
 			messages: [{ role: "system", content: systemPrompt }, ...convertToOpenAiMessages(messages)],
 			stream: true,
-			stream_options: { include_usage: true },
 			...(reasoning && reasoning),
 		})
 
@@ -78,12 +78,15 @@ export class XAIHandler extends BaseProvider implements SingleCompletionHandler
 			if (chunk.usage) {
 				// Extract detailed token information if available
 				// First check for prompt_tokens_details structure (real API response)
-				const promptDetails = "prompt_tokens_details" in chunk.usage ? chunk.usage.prompt_tokens_details : null;
-				const cachedTokens = promptDetails && "cached_tokens" in promptDetails ? promptDetails.cached_tokens : 0;
+				const promptDetails = "prompt_tokens_details" in chunk.usage ? chunk.usage.prompt_tokens_details : null
+				const cachedTokens = promptDetails && "cached_tokens" in promptDetails ? promptDetails.cached_tokens : 0
 
 				// Fall back to direct fields in usage (used in test mocks)
-				const readTokens = cachedTokens || ("cache_read_input_tokens" in chunk.usage ? (chunk.usage as any).cache_read_input_tokens : 0);
-				const writeTokens = "cache_creation_input_tokens" in chunk.usage ? (chunk.usage as any).cache_creation_input_tokens : 0;
+				const readTokens =
+					cachedTokens ||
+					("cache_read_input_tokens" in chunk.usage ? (chunk.usage as any).cache_read_input_tokens : 0)
+				const writeTokens =
+					"cache_creation_input_tokens" in chunk.usage ? (chunk.usage as any).cache_creation_input_tokens : 0
 
 				yield {
 					type: "usage",