Address all review comments: validate array content shape, validate systemPrompt type, forward all AIRequestOptions to Vercel adapter

- validateMessage: structural validation for array content elements (non-null objects with string type, text property for type:text)
- systemPrompt: runtime string validation, returns 400 for non-string values
- VercelLLMAdapter: buildVercelOptions helper forwards stop, tools, toolChoice to chat/complete/streamChat

Agent-Logs-Url: https://github.com/objectstack-ai/spec/sessions/ac262d54-6f0d-47a1-967b-c1f4b7636378

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/services/service-ai/src/adapters/vercel-adapter.ts

@@ -8,8 +8,42 @@ import type {
   ToolSet,
 } from '@objectstack/spec/contracts';
 import type { LLMAdapter } from '@objectstack/spec/contracts';
+import type { AIToolDefinition } from '@objectstack/spec/contracts';
 import type { LanguageModelV3 } from '@ai-sdk/provider';
-import { generateText, streamText } from 'ai';
+import { generateText, streamText, tool as vercelTool, jsonSchema } from 'ai';
+
+/**
+ * Convert ObjectStack `AIRequestOptions` into the subset of Vercel AI SDK
+ * options supported by `generateText` / `streamText`.
+ *
+ * Forwards: temperature, maxTokens, stop (→ stopSequences), tools, toolChoice.
+ */
+function buildVercelOptions(options?: AIRequestOptions): Record<string, unknown> {
+  if (!options) return {};
+
+  const opts: Record<string, unknown> = {};
+
+  if (options.temperature != null) opts.temperature = options.temperature;
+  if (options.maxTokens != null) opts.maxTokens = options.maxTokens;
+  if (options.stop?.length) opts.stopSequences = options.stop;
+
+  if (options.tools?.length) {
+    const tools: Record<string, unknown> = {};
+    for (const t of options.tools as AIToolDefinition[]) {
+      tools[t.name] = vercelTool({
+        description: t.description,
+        inputSchema: jsonSchema(t.parameters as any),
+      });
+    }
+    opts.tools = tools;
+  }
+
+  if (options.toolChoice != null) {
+    opts.toolChoice = options.toolChoice;
+  }
+
+  return opts;
+}
 
 /**
  * VercelLLMAdapter — Production LLM adapter powered by the Vercel AI SDK.
@@ -39,8 +73,7 @@ export class VercelLLMAdapter implements LLMAdapter {
     const result = await generateText({
       model: this.model,
       messages,
-      temperature: options?.temperature,
-      maxTokens: options?.maxTokens,
+      ...buildVercelOptions(options),
     });
 
     return {
@@ -59,8 +92,7 @@ export class VercelLLMAdapter implements LLMAdapter {
     const result = await generateText({
       model: this.model,
       prompt,
-      temperature: options?.temperature,
-      maxTokens: options?.maxTokens,
+      ...buildVercelOptions(options),
     });
 
     return {
@@ -81,8 +113,7 @@ export class VercelLLMAdapter implements LLMAdapter {
     const result = streamText({
       model: this.model,
       messages,
-      temperature: options?.temperature,
-      maxTokens: options?.maxTokens,
+      ...buildVercelOptions(options),
     });
 
     for await (const part of result.fullStream) {

packages/services/service-ai/src/routes/ai-routes.ts

@@ -91,11 +91,27 @@ function validateMessage(raw: unknown): string | null {
   if (typeof msg.role !== 'string' || !VALID_ROLES.has(msg.role)) {
     return `message.role must be one of ${[...VALID_ROLES].map(r => `"${r}"`).join(', ')}`;
   }
-  // Accept string content (legacy) or array content (Vercel multi-part)
-  if (typeof msg.content !== 'string' && !Array.isArray(msg.content)) {
-    return 'message.content must be a string or an array';
+  const content = msg.content;
+  if (typeof content === 'string') {
+    return null;
   }
-  return null;
+  if (Array.isArray(content)) {
+    const parts = content as unknown[];
+    for (const part of parts) {
+      if (typeof part !== 'object' || part === null) {
+        return 'message.content array elements must be non-null objects';
+      }
+      const partObj = part as Record<string, unknown>;
+      if (typeof partObj.type !== 'string') {
+        return 'each message.content array element must have a string "type" property';
+      }
+      if (partObj.type === 'text' && typeof partObj.text !== 'string') {
+        return 'message.content elements with type "text" must have a string "text" property';
+      }
+    }
+    return null;
+  }
+  return 'message.content must be a string or an array';
 }
 
 /**
@@ -167,7 +183,11 @@ export function buildAIRoutes(
         // ── Prepend system prompt ────────────────────────────
         // Vercel useChat sends `system` (or the deprecated `systemPrompt`)
         // as a top-level field.  We prepend it as a system message.
-        const systemPrompt = (body.system ?? body.systemPrompt) as string | undefined;
+        const rawSystemPrompt = body.system ?? body.systemPrompt;
+        if (rawSystemPrompt != null && typeof rawSystemPrompt !== 'string') {
+          return { status: 400, body: { error: 'system/systemPrompt must be a string' } };
+        }
+        const systemPrompt = rawSystemPrompt as string | undefined;
         const finalMessages: ModelMessage[] = [
           ...(systemPrompt
             ? [{ role: 'system' as const, content: systemPrompt }]