Fix streaming for z-ai in anthropic provider, add preliminary support for tool call streaming. Only reporting argument string deltas, not partial JSON objects

packages/ai/src/providers/transorm-messages.ts

@@ -0,0 +1,40 @@
+import type { Api, AssistantMessage, Message, Model } from "../types.js";
+
+export function transformMessages<TApi extends Api>(messages: Message[], model: Model<TApi>): Message[] {
+	return messages.map((msg) => {
+		// User and toolResult messages pass through unchanged
+		if (msg.role === "user" || msg.role === "toolResult") {
+			return msg;
+		}
+
+		// Assistant messages need transformation check
+		if (msg.role === "assistant") {
+			const assistantMsg = msg as AssistantMessage;
+
+			// If message is from the same provider and API, keep as is
+			if (assistantMsg.provider === model.provider && assistantMsg.api === model.api) {
+				return msg;
+			}
+
+			// Transform message from different provider/model
+			const transformedContent = assistantMsg.content.map((block) => {
+				if (block.type === "thinking") {
+					// Convert thinking block to text block with <thinking> tags
+					return {
+						type: "text" as const,
+						text: `<thinking>\n${block.thinking}\n</thinking>`,
+					};
+				}
+				// All other blocks (text, toolCall) pass through unchanged
+				return block;
+			});
+
+			// Return transformed assistant message
+			return {
+				...assistantMsg,
+				content: transformedContent,
+			};
+		}
+		return msg;
+	});
+}