feat: make systemPrompt sync and optional

Author: mdjastrzebski

docs/src/docs/core/context.md

@@ -24,7 +24,7 @@ export type RequestContext = {
   resolvedEntities: EntityInfo;
 
   /** Function for generating a system prompt */
-  systemPrompt: () => Promise<string> | string;
+  systemPrompt: () => string | null;
 
   /** 
    * Received partial response update with response streaming.

examples/bare/src/index.ts

@@ -17,7 +17,7 @@ const chatModel = new VercelChatModelAdapter({
   languageModel: openAiModel,
 });
 
-const SYSTEM_PROMPT = 'Your name is Byorg. You are an AI Assistant.';
+const SYSTEM_PROMPT = 'Your name is Byorg. You are a helpful AI Assistant.';
 
 const app = createApp({
   chatModel,

examples/slack/src/index.ts

@@ -18,7 +18,7 @@ const chatModel = new VercelChatModelAdapter({
   languageModel: openAiProvider.languageModel(LANGUAGE_MODEL),
 });
 
-const SYSTEM_PROMPT = 'Your name is Byorg. You are an AI Assistant.';
+const SYSTEM_PROMPT = 'Your name is Byorg. You are a helpful AI Assistant.';
 
 const app = createApp({
   chatModel,

packages/core/src/ai/vercel.ts

@@ -57,17 +57,18 @@ export class VercelChatModelAdapter implements ChatModel {
   constructor(private readonly _options: VercelChatModelAdapterOptions) {}
 
   async generateResponse(context: RequestContext): Promise<AssistantResponse> {
-    const messages = context.messages;
-
-    const systemPrompt = await context.systemPrompt();
+    let systemPrompt = context.systemPrompt();
     const entitiesPrompt = formatResolvedEntities(context.resolvedEntities);
-    const finalSystemPrompt = [systemPrompt, entitiesPrompt].join('\n\n');
+    if (systemPrompt && entitiesPrompt) {
+      systemPrompt += '\n\n' + entitiesPrompt;
+    }
+
+    const messages: CoreMessage[] = [];
+    if (systemPrompt) {
+      messages.push({ role: 'system', content: systemPrompt });
+    }
 
-    // TODO: Use userId in anonymous case
-    const resolvedMessages: CoreMessage[] = [
-      { role: 'system' as const, content: finalSystemPrompt },
-      ...messages.map(toMessageParam),
-    ];
+    messages.push(...context.messages.map(toMessageParam));
 
     const getRunToolFunction =
       <TParams extends z.ZodSchema, TOutput>(
@@ -94,7 +95,7 @@ export class VercelChatModelAdapter implements ChatModel {
 
     const executionContext: AiExecutionContext = {
       tools,
-      messages: resolvedMessages,
+      messages: messages,
     };
 
     const executionResult = context.onPartialResponse
@@ -229,14 +230,14 @@ function toNumberOrZero(n: number): number {
   return Number.isNaN(n) ? 0 : n;
 }
 
-function formatResolvedEntities(entities: Record<string, unknown>): string {
+function formatResolvedEntities(entities: Record<string, unknown>): string | null {
   if (Object.keys(entities).length === 0) {
-    return '';
+    return null;
   }
 
-  return `ENTITY DICTIONARY: \n
-    ${Object.entries(entities)
-      .map(([key, value]) => `'${key}' is '${JSON.stringify(value)}'`)
-      .join('\n')}
-      `;
+  return `### ENTITY DICTIONARY ###\n
+${Object.entries(entities)
+  .map(([key, value]) => `'${key}' is '${JSON.stringify(value)}'`)
+  .join('\n')}
+  `;
 }

packages/core/src/application.ts

@@ -33,7 +33,7 @@ export type ErrorHandler = (
 
 export type ApplicationConfig = {
   chatModel: ChatModel;
-  systemPrompt: (context: RequestContext) => Promise<string> | string;
+  systemPrompt?: ((context: RequestContext) => string | null) | string;
   plugins?: ApplicationPlugin[];
   errorHandler?: ErrorHandler;
 };
@@ -89,7 +89,6 @@ export function createApp(config: ApplicationConfig): Application {
       const performance = new PerformanceTimeline();
       performance.markStart(PerformanceMarks.processMessages);
 
-      const onPartialResponse = options?.onPartialResponse;
       const context: RequestContext = {
         messages,
         get lastMessage() {
@@ -101,14 +100,16 @@ export function createApp(config: ApplicationConfig): Application {
 
           return lastMessage;
         },
-
+        systemPrompt: () =>
+          typeof config.systemPrompt === 'function'
+            ? config.systemPrompt(context)
+            : (config.systemPrompt ?? null),
+        onPartialResponse: options?.onPartialResponse,
         tools,
         references: getReferenceStorage(),
         resolvedEntities: {},
-        onPartialResponse,
         extras: options?.extras ?? {},
         performance,
-        systemPrompt: () => config.systemPrompt(context),
       };
 
       const handler = async () => {

packages/core/src/domain.ts

@@ -30,7 +30,7 @@ export type RequestContext = {
   tools: ApplicationTool[];
   references: ReferenceStorage;
   resolvedEntities: EntityInfo;
-  systemPrompt: () => Promise<string> | string;
+  systemPrompt: () => string | null;
   onPartialResponse?: (text: string) => void;
   extras: MessageRequestExtras;
   performance: PerformanceTimeline;