Enable tool streaming for newer Z.ai models (#2732)

packages/ai/src/providers/openai-completions.ts

@@ -395,6 +395,9 @@ function buildParams(model: Model<"openai-completions">, context: Context, optio
 
 	if (context.tools) {
 		params.tools = convertTools(context.tools, compat);
+		if (compat.zaiToolStream) {
+			(params as any).tool_stream = true;
+		}
 	} else if (hasToolHistory(context.messages)) {
 		// Anthropic (via LiteLLM/proxy) requires tools param when conversation has tool_calls/tool_results
 		params.tools = [];
@@ -835,6 +838,7 @@ function detectCompat(model: Model<"openai-completions">): Required<OpenAIComple
 				: "openai",
 		openRouterRouting: {},
 		vercelGatewayRouting: {},
+		zaiToolStream: false,
 		supportsStrictMode: true,
 	};
 }
@@ -861,6 +865,7 @@ function getCompat(model: Model<"openai-completions">): Required<OpenAICompletio
 		thinkingFormat: model.compat.thinkingFormat ?? detected.thinkingFormat,
 		openRouterRouting: model.compat.openRouterRouting ?? {},
 		vercelGatewayRouting: model.compat.vercelGatewayRouting ?? detected.vercelGatewayRouting,
+		zaiToolStream: model.compat.zaiToolStream ?? detected.zaiToolStream,
 		supportsStrictMode: model.compat.supportsStrictMode ?? detected.supportsStrictMode,
 	};
 }

packages/ai/src/types.ts

@@ -277,6 +277,8 @@ export interface OpenAICompletionsCompat {
 	openRouterRouting?: OpenRouterRouting;
 	/** Vercel AI Gateway routing preferences. Only used when baseUrl points to Vercel AI Gateway. */
 	vercelGatewayRouting?: VercelGatewayRouting;
+	/** Whether z.ai supports top-level `tool_stream: true` for streaming tool call deltas. Default: false. */
+	zaiToolStream?: boolean;
 	/** Whether the provider supports the `strict` field in tool definitions. Default: true. */
 	supportsStrictMode?: boolean;
 }