fix: bound preview query context

apps/nextjs/src/app/api/assistant/chat/assistant-message-conversion.ts

@@ -1,8 +1,32 @@
 import { convertToModelMessages } from "ai";
 import type { UIMessage } from "ai";
 
+import { customWidgetPreviewQueryOutputMaxCharacters, toAssistantToolOutput } from "./assistant-tool-output";
+
+const isRecord = (value: unknown): value is Record<string, unknown> =>
+  typeof value === "object" && value !== null && !Array.isArray(value);
+
+const compactPreviewQueryOutputs = (messages: UIMessage[]): UIMessage[] =>
+  messages.map((message) => ({
+    ...message,
+    parts: message.parts.map((part) => {
+      if (!isRecord(part) || typeof part.type !== "string") return part;
+      const record: Record<string, unknown> = part;
+      const toolName =
+        part.type === "dynamic-tool" ? record.toolName : part.type.startsWith("tool-") ? part.type.slice(5) : undefined;
+      if (toolName !== "customWidget_previewQuery" || record.state !== "output-available") return part;
+
+      return {
+        ...part,
+        output: toAssistantToolOutput(record.output, {
+          maxCharacters: customWidgetPreviewQueryOutputMaxCharacters,
+        }),
+      } as unknown as typeof part;
+    }),
+  }));
+
 export const convertAssistantMessagesToModelMessages = (messages: UIMessage[]) =>
-  convertToModelMessages(messages, {
+  convertToModelMessages(compactPreviewQueryOutputs(messages), {
     // An aborted response can leave a streamed tool call in conversation history without a
     // result. Replaying it makes several OpenAI-compatible providers reject the whole prompt.
     ignoreIncompleteToolCalls: true,