simstudioai · waleedlatif1 · Aug 3, 2026 · Aug 3, 2026
diff --git a/apps/sim/app/_shell/public-env-script.test.tsx b/apps/sim/app/_shell/public-env-script.test.tsx
@@ -0,0 +1,35 @@
+/**
+ * @vitest-environment node
+ */
+import { EnvScript } from 'next-runtime-env'
+import { describe, expect, it } from 'vitest'
+import { PublicEnvScript } from '@/app/_shell/public-env-script'
+
+/**
+ * Guards the loading strategy, not the markup. A plain `<script>` rendered from
+ * the root layout lands after the `<script async>` chunk tags Next emits at the
+ * top of the document, so a chunk can execute - and hydration can begin - before
+ * `window.__ENV` is populated. Delegating to `<EnvScript>` keeps the
+ * `beforeInteractive` guarantee that `next-runtime-env` applies by default.
+ */
+describe('PublicEnvScript', () => {
+  it('delegates to next-runtime-env EnvScript rather than emitting a raw script tag', () => {
+    const element = PublicEnvScript()
+
+    expect(element.type).toBe(EnvScript)
+    expect(element.type).not.toBe('script')
+  })
+
+  it('does not opt out of the beforeInteractive strategy', () => {
+    const { disableNextScript, nextScriptProps } = PublicEnvScript().props
+
+    expect(disableNextScript).toBeUndefined()
+    expect(nextScriptProps?.strategy ?? 'beforeInteractive').toBe('beforeInteractive')
+  })
+
+  it('passes only NEXT_PUBLIC_ variables through to the browser', () => {
+    const keys = Object.keys(PublicEnvScript().props.env)
+
+    expect(keys.every((key) => /^NEXT_PUBLIC_/i.test(key))).toBe(true)
+  })
+})
diff --git a/apps/sim/app/_shell/public-env-script.tsx b/apps/sim/app/_shell/public-env-script.tsx
@@ -1,36 +1,38 @@
-import { PUBLIC_ENV_KEY } from 'next-runtime-env'
+import { EnvScript } from 'next-runtime-env'
 
 /**
- * `NEXT_PUBLIC_*` values, captured once at module load (build time / server
- * start) rather than read per-request - correct on the hosted deployment,
- * where a build's env never changes between requests. Filter matches
- * `next-runtime-env`'s own `getPublicEnv()` exactly.
+ * `NEXT_PUBLIC_*` values, captured once when this module is first loaded - i.e.
+ * at server start on the hosted deployment, where a build's env never changes
+ * between requests. Filter matches `next-runtime-env`'s own `getPublicEnv()`
+ * exactly.
+ *
+ * These are deliberately NOT the values Next inlines into the client bundle:
+ * the image is built with placeholder `NEXT_PUBLIC_*` values and the real ones
+ * are supplied to the container at start, so `window.__ENV` is the only source
+ * of truth in the browser.
  */
 const HOSTED_PUBLIC_ENV = Object.fromEntries(
   Object.entries(process.env).filter(([key]) => /^NEXT_PUBLIC_/i.test(key))
 )
 
 /**
- * Static, build-time equivalent of `next-runtime-env`'s `<PublicEnvScript>`
- * for the hosted deployment. It populates `window[PUBLIC_ENV_KEY]` with the
- * exact same shape `getEnv()` (`lib/core/config/env.ts`) reads client-side,
- * but without `next-runtime-env`'s unconditional `unstable_noStore()` call -
- * that call opts the entire app into dynamic rendering, which only pays off
- * for self-hosted Docker images that re-inject env per deploy without a
- * rebuild. On hosted, env is fixed per build, so this is safe to render
- * statically alongside the marketing pages' `revalidate`.
+ * Static equivalent of `next-runtime-env`'s `<PublicEnvScript>` for the hosted
+ * deployment. It renders the library's own `<EnvScript>`, so the emitted markup
+ * and its `beforeInteractive` loading strategy are identical to the self-hosted
+ * path - only the env read differs. `<PublicEnvScript>` additionally calls
+ * `unstable_noStore()`, which opts the entire app into dynamic rendering; that
+ * only pays off for self-hosted Docker images that re-inject env per deploy
+ * without a rebuild, so hosted reads the env once here and stays static.
  *
- * Escapes `<` in the serialized JSON so an env value containing `</script>`
- * can't close this tag early and inject markup into every hosted page.
+ * `beforeInteractive` is load-bearing, not an optimization. A plain `<script>`
+ * rendered from the root layout lands at the end of `<head>`, after the ~40
+ * `<script async>` chunk tags Next emits at the top of the document; an `async`
+ * script runs as soon as its fetch resolves, so on a warm cache a Next chunk
+ * can execute - and hydration can begin - before the parser reaches the env
+ * tag, leaving `window.__ENV` undefined for the first render.
+ * `beforeInteractive` instead queues the script into `self.__next_s`, which
+ * Next's `appBootstrap` drains to completion before calling `hydrate()`.
  */
 export function PublicEnvScript() {
-  const serialized = JSON.stringify(HOSTED_PUBLIC_ENV).replace(/</g, '\\u003c')
-  return (
-    <script
-      id='public-env'
-      dangerouslySetInnerHTML={{
-        __html: `window['${PUBLIC_ENV_KEY}'] = ${serialized}`,
-      }}
-    />
-  )
+  return <EnvScript env={HOSTED_PUBLIC_ENV} />
 }
diff --git a/apps/sim/ee/sso/components/sso-form.tsx b/apps/sim/ee/sso/components/sso-form.tsx
@@ -6,7 +6,7 @@ import { createLogger } from '@sim/logger'
 import Link from 'next/link'
 import { useRouter, useSearchParams } from 'next/navigation'
 import { client } from '@/lib/auth/auth-client'
-import { env, isFalsy } from '@/lib/core/config/env'
+import { getEnv, isFalsy } from '@/lib/core/config/env'
 import { validateCallbackUrl } from '@/lib/core/security/input-validation'
 import { quickValidateEmail } from '@/lib/messaging/email/validation'
 import { AuthSubmitButton } from '@/app/(auth)/components'
@@ -38,6 +38,8 @@ export default function SSOForm() {
   const [showEmailValidationError, setShowEmailValidationError] = useState(false)
   const [callbackUrl, setCallbackUrl] = useState('/workspace')
 
+  const emailEnabled = !isFalsy(getEnv('NEXT_PUBLIC_EMAIL_PASSWORD_SIGNUP_ENABLED'))
+
   useEffect(() => {
     if (searchParams) {
       const callback = searchParams.get('callbackUrl')
@@ -184,8 +186,7 @@ export default function SSOForm() {
         </AuthSubmitButton>
       </form>
 
-      {/* Only show divider and email signin button if email/password is enabled */}
-      {!isFalsy(env.NEXT_PUBLIC_EMAIL_PASSWORD_SIGNUP_ENABLED) && (
+      {emailEnabled && (
         <>
           <div className='relative my-6 font-light'>
             <div className='absolute inset-0 flex items-center'>
@@ -208,8 +209,7 @@ export default function SSOForm() {
         </>
       )}
 
-      {/* Only show signup link if email/password signup is enabled */}
-      {!isFalsy(env.NEXT_PUBLIC_EMAIL_PASSWORD_SIGNUP_ENABLED) && (
+      {emailEnabled && (
         <div className='pt-6 text-center font-light text-base'>
           <span className='font-normal'>Don't have an account? </span>
           <Link

diff --git a/apps/sim/lib/core/utils/urls.test.ts b/apps/sim/lib/core/utils/urls.test.ts
@@ -14,6 +14,7 @@ vi.mock('@/lib/core/config/env', () => ({
 }))
 
 import {
+  getBaseUrl,
   getBrowserOrigin,
   getSocketUrl,
   isLocalhostUrl,
@@ -37,6 +38,36 @@ describe('getBrowserOrigin', () => {
   })
 })
 
+describe('getBaseUrl', () => {
+  beforeEach(() => {
+    mockGetEnv.mockReset()
+    mockGetEnv.mockReturnValue(undefined)
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it('uses NEXT_PUBLIC_APP_URL when set', () => {
+    mockGetEnv.mockImplementation((key) =>
+      key === 'NEXT_PUBLIC_APP_URL' ? 'https://app.example.com' : undefined
+    )
+    setLocation('https://other.example.com/workspace/w/1')
+    expect(getBaseUrl()).toBe('https://app.example.com')
+  })
+
+  it('falls back to the page origin instead of throwing when the injected env is missing', () => {
+    setLocation('https://www.sim.ai/workspace/ws-1/w/wf-1')
+    expect(getBaseUrl()).toBe('https://www.sim.ai')
+  })
+
+  it('treats a whitespace-only NEXT_PUBLIC_APP_URL as unset', () => {
+    mockGetEnv.mockImplementation((key) => (key === 'NEXT_PUBLIC_APP_URL' ? '   ' : undefined))
+    setLocation('https://www.sim.ai/')
+    expect(getBaseUrl()).toBe('https://www.sim.ai')
+  })
+})
+
 describe('getSocketUrl', () => {
   beforeEach(() => {
     mockGetEnv.mockReset()

diff --git a/apps/sim/lib/core/utils/urls.ts b/apps/sim/lib/core/utils/urls.ts
@@ -24,19 +24,32 @@ function normalizeBaseUrl(url: string): string {
 /**
  * Returns the base URL of the application from NEXT_PUBLIC_APP_URL
  * This ensures webhooks, callbacks, and other integrations always use the correct public URL
+ *
+ * In the browser, falls back to the page's own origin when the injected env is
+ * unavailable. Client-side callers only ever want a URL back to the app they are
+ * already served from, so the origin is a correct answer — and a throw here
+ * during render tears down the whole page through the error boundary. Server-side
+ * callers (webhooks, callbacks, emails) have no origin to fall back to and must
+ * still fail loudly on a misconfigured deployment.
+ *
  * @returns The base URL string (e.g., 'http://localhost:3000' or 'https://example.com')
- * @throws Error if NEXT_PUBLIC_APP_URL is not configured
+ * @throws Error if NEXT_PUBLIC_APP_URL is not configured and no browser origin exists
  */
 export function getBaseUrl(): string {
   const baseUrl = getEnv('NEXT_PUBLIC_APP_URL')?.trim()
 
-  if (!baseUrl) {
-    throw new Error(
-      'NEXT_PUBLIC_APP_URL must be configured for webhooks and callbacks to work correctly'
-    )
+  if (baseUrl) {
+    return normalizeBaseUrl(baseUrl)
+  }
+
+  const browserOrigin = getBrowserOrigin()
+  if (browserOrigin) {
+    return browserOrigin
   }
 
-  return normalizeBaseUrl(baseUrl)
+  throw new Error(
+    'NEXT_PUBLIC_APP_URL must be configured for webhooks and callbacks to work correctly'
+  )
 }
 
 /**

diff --git a/packages/testing/src/mocks/urls.mock.ts b/packages/testing/src/mocks/urls.mock.ts
@@ -26,14 +26,18 @@ function hasHttpProtocol(url: string): boolean {
 
 function getBaseUrlImpl(): string {
   const baseUrl = readEnv('NEXT_PUBLIC_APP_URL')?.trim()
-  if (!baseUrl) {
-    throw new Error(
-      'NEXT_PUBLIC_APP_URL must be configured for webhooks and callbacks to work correctly'
-    )
+  if (baseUrl) {
+    // Mirrors the real module: protocol-less values get https:// under isProd.
+    const protocol = envFlagsMock.isProd ? 'https://' : 'http://'
+    return hasHttpProtocol(baseUrl) ? baseUrl : `${protocol}${baseUrl}`
   }
-  // Mirrors the real module: protocol-less values get https:// under isProd.
-  const protocol = envFlagsMock.isProd ? 'https://' : 'http://'
-  return hasHttpProtocol(baseUrl) ? baseUrl : `${protocol}${baseUrl}`
+  // Mirrors the real module: the browser falls back to its own origin, only
+  // server-side (no `window`) callers throw.
+  const browserOrigin = getBrowserOriginImpl()
+  if (browserOrigin) return browserOrigin
+  throw new Error(
+    'NEXT_PUBLIC_APP_URL must be configured for webhooks and callbacks to work correctly'
+  )
 }
 
 function getInternalApiBaseUrlImpl(): string {