Azure Swa Functions Stack

Azure SWA + Functions Full-Stack

Ship a React admin/tool UI on Azure Static Web Apps (free plan) that calls a standalone Azure Functions backend. Captures the patterns and gotchas from a production deployment.

When to use

• User wants a full-stack app on Azure with a React frontend and C#/TypeScript Functions backend
• User mentions "Static Web Apps + Functions", "SWA free plan", or needs cheap Azure hosting
• User needs the standalone Functions app (not SWA's built-in managed Functions) because they're using Flex Consumption or non-Consumption plans

Architecture

┌─────────────────────────────────┐         ┌────────────────────────────┐
│ Azure Static Web Apps (free)    │         │ Azure Functions (Flex)     │
│ ─────────────────────────────── │  CORS   │ ────────────────────────── │
│ React + Vite SPA                │ ──────▶ │ REST API (/api/*)          │
│ dist/ served from CDN           │         │ MCP tools (optional)       │
│ staticwebapp.config.json        │         │ Azure Storage backed       │
└─────────────────────────────────┘         └────────────────────────────┘

Why standalone Functions instead of SWA's built-in API:

• SWA managed Functions only support Consumption plan (no Flex, no Premium)
• You can't add the MCP extension to managed Functions
• You need more than 60s execution time

Project layout

my-app/
├── frontend/                    # React SPA → Azure Static Web Apps
│   ├── src/
│   ├── index.html
│   ├── vite.config.ts
│   ├── tsconfig.json
│   ├── staticwebapp.config.json
│   └── package.json
├── functions/                   # Azure Functions → standalone deploy
│   ├── host.json
│   ├── local.settings.json
│   └── (.NET or TypeScript project)
├── swa-cli.config.json          # Optional local orchestration
└── .gitignore

Frontend scaffold

npm create vite@latest frontend -- --template react-ts
cd frontend
npm install
npm install react-router-dom @tanstack/react-query lucide-react
npm install -D tailwindcss @tailwindcss/vite

vite.config.ts (CRITICAL for local dev)

import { defineConfig } from 'vite'
import react from '@vitejs/plugin-react'
import tailwindcss from '@tailwindcss/vite'

export default defineConfig({
  plugins: [react(), tailwindcss()],
  server: {
    proxy: {
      '/api': {
        target: 'http://localhost:7071',
        changeOrigin: true
      }
    }
  }
})

The /api proxy is essential — it forwards frontend calls at localhost:5173/api/* to the Functions app at localhost:7071/api/*, eliminating CORS issues during local dev.

staticwebapp.config.json

{
  "navigationFallback": {
    "rewrite": "/index.html",
    "exclude": ["/assets/*", "/api/*"]
  }
}

This makes client-side routing work — any URL that isn't a static asset or API call gets served index.html so React Router can handle it.

src/main.css

@import "tailwindcss";

API client pattern

src/services/api.ts:

const API_BASE = import.meta.env.VITE_API_BASE_URL || '/api';

function authHeaders(): Record<string, string> {
  const token = sessionStorage.getItem('auth');
  return token ? { 'X-Auth-Token': token } : {};
}

async function request<T>(path: string, options?: RequestInit): Promise<T> {
  const res = await fetch(`${API_BASE}${path}`, {
    ...options,
    headers: { 'Content-Type': 'application/json', ...authHeaders(), ...options?.headers },
  });
  if (res.status === 401) {
    sessionStorage.removeItem('auth');
    window.location.href = '/login';
    throw new Error('Unauthorized');
  }
  if (!res.ok) throw new Error(`API ${res.status}: ${await res.text()}`);
  return res.json();
}

Key pattern: VITE_API_BASE_URL defaults to /api for local dev (uses the Vite proxy). In production, it's overridden at build time to point to the Functions app directly:

VITE_API_BASE_URL="https://<func-app>.azurewebsites.net/api" npx vite build

Functions backend (see also: azure-functions-mcp skill)

functions/local.settings.json:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated"
  },
  "Host": {
    "LocalHttpPort": 7071,
    "CORS": "http://localhost:5173",
    "CORSCredentials": false
  }
}

CORS configuration (PRODUCTION — CRITICAL)

SWA free plan has NO built-in API proxy. The frontend is served from *.azurestaticapps.net and makes cross-origin calls to the Functions app. You MUST configure CORS on the Functions app:

az functionapp cors add \
  --name <function-app-name> \
  --resource-group <rg> \
  --allowed-origins "https://<swa-name>.azurestaticapps.net"

Verify:

az functionapp cors show --name <app> --resource-group <rg>

Should list your SWA origin. If you add a custom domain to the SWA later, add that origin too.

Simple password auth pattern (optional)

For admin/demo tools where you just need a gate (not full user accounts):

Backend (AuthApi.cs):

public class AuthApi
{
    private readonly string _password;
    public AuthApi(IConfiguration config) { _password = config["ADMIN_PASSWORD"] ?? "demo"; }

    [Function("Login")]
    public async Task<IActionResult> Login(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "auth/login")] HttpRequest req)
    {
        var body = await JsonSerializer.DeserializeAsync<LoginRequest>(req.Body, new() { PropertyNameCaseInsensitive = true });
        if (body?.Password != _password) return new UnauthorizedObjectResult(new { error = "Invalid password." });
        return new OkObjectResult(new { ok = true });
    }

    private record LoginRequest(string Password);
}

Set the password as an app setting (don't commit to repo):

az functionapp config appsettings set --name <app> --resource-group <rg> \
  --settings 'ADMIN_PASSWORD=<your-password>'

Frontend: store the password itself as the "token" in sessionStorage.setItem('auth', password) after successful login, and send as X-Auth-Token header. All protected endpoints check the header against the same env var.

Wrap routes with a guard component:

function RequireAuth({ children }: { children: ReactNode }) {
  if (!sessionStorage.getItem('auth')) return <Navigate to="/login" replace />;
  return <>{children}</>;
}

<Routes>
  <Route path="/login" element={<Login />} />
  <Route path="/*" element={<RequireAuth><Layout>...</Layout></RequireAuth>} />
</Routes>

This is session-only — closing the tab logs you out. Good enough for demo tools. NOT suitable for multi-user production apps.

Local dev workflow

# Terminal 1: storage emulator (if backend needs it)
azurite --silent --location .azurite

# Terminal 2: backend
cd functions && func start     # → http://localhost:7071

# Terminal 3: frontend
cd frontend && npm run dev     # → http://localhost:5173

Vite proxy forwards /api/* to 7071, so everything "just works" cross-origin-free.

Production deployment

1. Deploy Functions

cd functions
func azure functionapp publish <function-app-name> --dotnet-isolated

2. Build frontend with production URLs

cd frontend
VITE_API_BASE_URL="https://<func-app>.azurewebsites.net/api" \
  npx vite build

3. Deploy to Static Web Apps

Get the deployment token from the Azure portal (SWA → Overview → Manage deployment token), then:

npx @azure/static-web-apps-cli deploy dist \
  --deployment-token "<token>" \
  --env production

Always use --env production — omitting it deploys to a preview environment that isn't visible at the main URL.

4. Configure CORS (one-time)

az functionapp cors add --name <func-app> --resource-group <rg> \
  --allowed-origins "https://<swa>.azurestaticapps.net"

Gotchas

1. Flex Consumption + SWA managed API don't mix

If you want Flex Consumption (better cold start, more memory), you MUST use a standalone Functions app — SWA's built-in API is Consumption-only. That's why this skill uses the standalone pattern.

2. Environment variables at build time vs runtime

VITE_* env vars are INLINED into the JS bundle at build time, not runtime. Changing VITE_API_BASE_URL after deploy requires a rebuild. If you need runtime config, fetch a /config.json from the public folder instead.

3. Preview vs production deploy

swa deploy without --env production creates a preview environment at a different URL (e.g., https://<swa>-preview.azurestaticapps.net). Your main URL stays on the old build. Always pass --env production for real deployments.

4. CORS + custom domain

If you add a custom domain to your SWA, you must add that origin to the Functions CORS list separately — the *.azurestaticapps.net origin does not cover it.

5. Trailing slashes on API paths

Azure Functions HTTP triggers are picky about trailing slashes. GET /api/modules and GET /api/modules/ may behave differently. Be consistent in your API client.

When to pair with other skills

• Pair with azure-functions-mcp if the backend also exposes MCP tools. The same Functions app can serve both the REST API (for the frontend) and MCP endpoints (for Claude/Copilot) — just make sure function names are unique across the two.