OpenUI lang for structured outputs

examples/invoices-structured-output/.gitignore

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+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/versions
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.pnpm-debug.log*
+
+# env files (can opt-in for committing if needed)
+.env*
+
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts

examples/invoices-structured-output/README.md

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+# Invoice Structured Output Example
+
+A Next.js app demonstrating `@openuidev/structured-output` — the standalone OpenUI Lang library for schema-driven structured output from LLMs.
+
+## What it does
+
+1. **Select an invoice format** — Standard, Freelance, or International
+2. **Describe the invoice** — or use the provided sample prompt
+3. **Watch the LLM stream** — the raw OpenUI Lang appears on the left as tokens arrive
+4. **See parsed JSON** — the streaming parser progressively builds the validated JSON on the right
+
+The backend generates a system prompt from the Zod schema using `schema.prompt()`, sends it to the LLM, and streams back the raw OpenUI Lang. The frontend uses `schema.streamingParser()` to parse and validate the output in real time.
+
+## Setup
+
+```bash
+# From the monorepo root
+pnpm install
+
+# Add your OpenRouter API key
+cp examples/invoices-structured-output/.env.example examples/invoices-structured-output/.env.local
+# Edit .env.local with your key
+
+# Run the dev server
+pnpm --filter invoices-structured-output dev
+```
+
+## Invoice Formats
+
+| Format | Description |
+| --- | --- |
+| **Standard** | Simple business invoice with line items, tax rate, and totals |
+| **Freelance** | Consulting invoice with hourly time entries and project details |
+| **International** | Multi-currency invoice with addresses, tax breakdown, and shipping |
+
+## Key files
+
+- `src/app/schemas.ts` — Invoice type definitions using `defineType` and `createSchema`
+- `src/app/api/generate/route.ts` — API route that generates the prompt and streams LLM output
+- `src/app/page.tsx` — Frontend with format picker, streaming display, and parsed JSON view

examples/invoices-structured-output/eslint.config.mjs

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+import { defineConfig, globalIgnores } from "eslint/config";
+import nextVitals from "eslint-config-next/core-web-vitals";
+import nextTs from "eslint-config-next/typescript";
+
+const eslintConfig = defineConfig([
+  ...nextVitals,
+  ...nextTs,
+  // Override default ignores of eslint-config-next.
+  globalIgnores([
+    // Default ignores of eslint-config-next:
+    ".next/**",
+    "out/**",
+    "build/**",
+    "next-env.d.ts",
+  ]),
+]);
+
+export default eslintConfig;

examples/invoices-structured-output/next.config.ts

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+import type { NextConfig } from "next";
+
+const nextConfig: NextConfig = {
+  transpilePackages: ["@openuidev/structured-output"],
+  serverExternalPackages: ["openai"],
+};
+
+export default nextConfig;

examples/invoices-structured-output/package.json

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+{
+  "name": "invoices-structured-output",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev",
+    "build": "next build",
+    "start": "next start",
+    "lint": "eslint"
+  },
+  "dependencies": {
+    "@openuidev/structured-output": "workspace:^",
+    "next": "16.1.6",
+    "openai": "^6.27.0",
+    "react": "19.2.3",
+    "react-dom": "19.2.3",
+    "zod": "^4.3.6"
+  },
+  "devDependencies": {
+    "@tailwindcss/postcss": "^4",
+    "@types/node": "^20",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "eslint": "^9",
+    "eslint-config-next": "16.1.6",
+    "tailwindcss": "^4",
+    "typescript": "^5"
+  }
+}

examples/invoices-structured-output/postcss.config.mjs

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+const config = {
+  plugins: {
+    "@tailwindcss/postcss": {},
+  },
+};
+
+export default config;

examples/invoices-structured-output/src/app/api/generate/route.ts

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+import { NextRequest } from "next/server";
+import OpenAI from "openai";
+import { invoiceSchemaMap } from "../../schemas";
+
+let _client: OpenAI | null = null;
+function getClient() {
+  if (!_client) {
+    _client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
+  }
+  return _client;
+}
+
+const BUSINESS_PREAMBLE = `You are an expert accounting assistant that generates structured invoice data.
+Given a description of an invoice, extract or generate all relevant fields with realistic data.
+Use plausible business names, dates, amounts, and tax calculations.
+All monetary amounts should be numbers (not strings). Dates should be in YYYY-MM-DD format.
+Ensure line item amounts equal quantity × unitPrice. Ensure totals are arithmetically correct.`;
+
+export async function POST(req: NextRequest) {
+  const { userPrompt } = (await req.json()) as {
+    userPrompt: string;
+  };
+
+  const systemPrompt = invoiceSchemaMap.prompt({
+    preamble: BUSINESS_PREAMBLE,
+    additionalRules: [
+      "All dates must be YYYY-MM-DD format",
+      "Monetary amounts must be numbers with up to 2 decimal places",
+      "NEVER use arithmetic expressions like 8*125 or 10+20 — always write the pre-computed numeric result (e.g. 1000, 30)",
+      "Ensure mathematical consistency: subtotal = sum of item amounts, total = subtotal + tax + shipping",
+    ],
+  });
+
+  console.log(systemPrompt);
+
+  const stream = await getClient().chat.completions.create({
+    model: "gpt-5",
+    stream: true,
+    messages: [
+      { role: "system", content: systemPrompt },
+      { role: "user", content: userPrompt },
+    ],
+    reasoning_effort: "minimal",
+  });
+
+  const encoder = new TextEncoder();
+
+  const readable = new ReadableStream({
+    async start(controller) {
+      const send = (type: string, content: string) =>
+        controller.enqueue(encoder.encode(JSON.stringify({ type, content }) + "\n"));
+
+      try {
+        for await (const chunk of stream) {
+          const delta = chunk.choices?.[0]?.delta as Record<string, unknown> | undefined;
+          if (!delta) continue;
+
+          const thinking =
+            (delta.reasoning as string | undefined) ??
+            (delta.reasoning_content as string | undefined);
+          if (thinking) send("thinking", thinking);
+
+          const content = delta.content as string | undefined;
+          if (content) send("content", content);
+        }
+      } catch (err) {
+        const message = err instanceof Error ? err.message : "Stream error";
+        send("error", message);
+      } finally {
+        controller.close();
+      }
+    },
+  });
+
+  return new Response(readable, {
+    headers: {
+      "Content-Type": "application/x-ndjson; charset=utf-8",
+      "Transfer-Encoding": "chunked",
+      "Cache-Control": "no-cache",
+    },
+  });
+}

examples/invoices-structured-output/src/app/globals.css

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+@import "tailwindcss";
+
+html {
+  font-size: 150%;
+}

examples/invoices-structured-output/src/app/layout.tsx

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+import type { Metadata } from "next";
+import "./globals.css";
+
+export const metadata: Metadata = {
+  title: "Invoice Structured Output",
+  description: "Generate structured invoice data using OpenUI Lang and streaming LLM output",
+};
+
+export default function RootLayout({
+  children,
+}: Readonly<{
+  children: React.ReactNode;
+}>) {
+  return (
+    <html lang="en" className="dark">
+      <body className="antialiased">{children}</body>
+    </html>
+  );
+}