diff --git a/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.test.tsx b/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.test.tsx
index eefe539..815748a 100644
--- a/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.test.tsx
+++ b/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.test.tsx
@@ -1,18 +1,17 @@
 import { render } from '@testing-library/react'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { CookieCategoryName, type CookieConsent } from '../gdpr/types'
-import {
-  loadGoogleAnalytics,
-  setGoogleConsentDefault,
-  updateAnalyticsConsent,
-} from './consent-mode'
+import { bootstrapGoogleAnalytics } from './bootstrap'
+import { updateAnalyticsConsent } from './consent-mode'
 import { GoogleAnalyticsWithConsent } from './GoogleAnalyticsWithConsent'
 import { useCookieConsent } from '../gdpr/contexts/useCookieConsent'
 import type { CookieConsentContextType } from '../gdpr/contexts/CookieConsentShared'
 
+vi.mock('./bootstrap', () => ({
+  bootstrapGoogleAnalytics: vi.fn(),
+}))
+
 vi.mock('./consent-mode', () => ({
-  setGoogleConsentDefault: vi.fn(),
-  loadGoogleAnalytics: vi.fn(),
   updateAnalyticsConsent: vi.fn(),
 }))
 
@@ -46,18 +45,13 @@ describe('GoogleAnalyticsWithConsent', () => {
     expect(container.childNodes).toHaveLength(0)
   })
 
-  it('sets the denied consent default before loading GA on mount', () => {
+  it('bootstraps GA once on mount', () => {
     mockConsent(false)
 
     render(<GoogleAnalyticsWithConsent gaId={TEST_GA_ID} />)
 
-    expect(setGoogleConsentDefault).toHaveBeenCalledTimes(1)
-    expect(loadGoogleAnalytics).toHaveBeenCalledWith(TEST_GA_ID)
-
-    // The default must be set before GA is configured.
-    const defaultOrder = vi.mocked(setGoogleConsentDefault).mock.invocationCallOrder[0]
-    const loadOrder = vi.mocked(loadGoogleAnalytics).mock.invocationCallOrder[0]
-    expect(defaultOrder).toBeLessThan(loadOrder)
+    expect(bootstrapGoogleAnalytics).toHaveBeenCalledTimes(1)
+    expect(bootstrapGoogleAnalytics).toHaveBeenCalledWith(TEST_GA_ID)
   })
 
   it('keeps analytics denied while the visitor has not consented', () => {
@@ -86,17 +80,15 @@ describe('GoogleAnalyticsWithConsent', () => {
     rerender(<GoogleAnalyticsWithConsent gaId={TEST_GA_ID} />)
 
     expect(updateAnalyticsConsent).toHaveBeenLastCalledWith(true)
-    // GA is loaded once; only the consent signal changes.
-    expect(setGoogleConsentDefault).toHaveBeenCalledTimes(1)
-    expect(loadGoogleAnalytics).toHaveBeenCalledTimes(1)
+    // GA is bootstrapped once; only the consent signal changes afterwards.
+    expect(bootstrapGoogleAnalytics).toHaveBeenCalledTimes(1)
   })
 
-  it('does nothing when no gaId is provided', () => {
+  it('does not bootstrap when no gaId is provided', () => {
     mockConsent(false)
 
     render(<GoogleAnalyticsWithConsent gaId="" />)
 
-    expect(setGoogleConsentDefault).not.toHaveBeenCalled()
-    expect(loadGoogleAnalytics).not.toHaveBeenCalled()
+    expect(bootstrapGoogleAnalytics).not.toHaveBeenCalled()
   })
 })
diff --git a/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.tsx b/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.tsx
index a9c8828..07689c9 100644
--- a/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.tsx
+++ b/documentation-ui/src/custom/docs/components/analytics/GoogleAnalyticsWithConsent.tsx
@@ -3,11 +3,8 @@
 import { useEffect } from 'react'
 import { useCookieConsent } from '../gdpr/contexts/useCookieConsent'
 import { CookieCategoryName } from '../gdpr/types'
-import {
-  loadGoogleAnalytics,
-  setGoogleConsentDefault,
-  updateAnalyticsConsent,
-} from './consent-mode'
+import { bootstrapGoogleAnalytics } from './bootstrap'
+import { updateAnalyticsConsent } from './consent-mode'
 
 export type GoogleAnalyticsWithConsentProps = {
   gaId: string
@@ -16,10 +13,18 @@ export type GoogleAnalyticsWithConsentProps = {
 /**
  * Loads Google Analytics (GA4) and drives it with Google Consent Mode v2.
  *
- * GA is always loaded, but consent defaults to `denied`, so GA sends anonymous
- * cookieless pings (aggregate pageview counts, no tracking cookies) until the
- * visitor grants the Analytics cookie category. When consent changes, a
- * `consent update` upgrades or downgrades GA accordingly.
+ * GA is always loaded. Bootstrapping is delegated to `bootstrapGoogleAnalytics`,
+ * which seeds the consent *default* from the visitor's stored decision: a
+ * first-time or declining visitor defaults to `denied` (anonymous cookieless
+ * pings, no tracking cookies), while a returning, already-consented visitor
+ * defaults to `granted` so their very first `page_view` is measured with
+ * consent. When consent changes during the session, a `consent update`
+ * upgrades or downgrades GA accordingly.
+ *
+ * The bootstrap is idempotent: in the sphinx injection it is invoked
+ * synchronously before React mounts (avoiding post-hydration delay), so this
+ * effect becomes a no-op there; in contexts without that injection (e.g.
+ * Next.js) this effect performs the bootstrap itself.
  *
  * This is framework-agnostic (no `next/script`), so it works in Next.js apps
  * and in the plain-React sphinx injection alike. Render it inside a
@@ -34,9 +39,7 @@ export function GoogleAnalyticsWithConsent({ gaId }: GoogleAnalyticsWithConsentP
       return
     }
 
-    // The consent default must be set before GA's config call.
-    setGoogleConsentDefault()
-    loadGoogleAnalytics(gaId)
+    bootstrapGoogleAnalytics(gaId)
   }, [gaId])
 
   useEffect(() => {
diff --git a/documentation-ui/src/custom/docs/components/analytics/bootstrap.test.ts b/documentation-ui/src/custom/docs/components/analytics/bootstrap.test.ts
new file mode 100644
index 0000000..f13b79c
--- /dev/null
+++ b/documentation-ui/src/custom/docs/components/analytics/bootstrap.test.ts
@@ -0,0 +1,90 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { CookieCategoryName, type CookieConsent } from '../gdpr/types'
+import { retrieveConsentCategoriesFromCookies } from '../gdpr/service/cookie-consent-service'
+import {
+  hasGoogleAnalyticsScript,
+  loadGoogleAnalytics,
+  setGoogleConsentDefault,
+} from './consent-mode'
+import { bootstrapGoogleAnalytics } from './bootstrap'
+
+vi.mock('./consent-mode', () => ({
+  hasGoogleAnalyticsScript: vi.fn(() => false),
+  loadGoogleAnalytics: vi.fn(),
+  setGoogleConsentDefault: vi.fn(),
+}))
+
+vi.mock('../gdpr/service/cookie-consent-service', () => ({
+  retrieveConsentCategoriesFromCookies: vi.fn(),
+}))
+
+const TEST_GA_ID = 'G-TEST12345'
+
+const buildConsent = (analyticsGranted: boolean): CookieConsent => ({
+  [CookieCategoryName.Essential]: true,
+  [CookieCategoryName.Analytics]: analyticsGranted,
+})
+
+beforeEach(() => {
+  vi.mocked(hasGoogleAnalyticsScript).mockReturnValue(false)
+  vi.mocked(retrieveConsentCategoriesFromCookies).mockReturnValue(buildConsent(false))
+})
+
+afterEach(() => {
+  vi.clearAllMocks()
+})
+
+describe('bootstrapGoogleAnalytics', () => {
+  it('seeds a granted default before loading GA for an already-consented visitor', () => {
+    vi.mocked(retrieveConsentCategoriesFromCookies).mockReturnValue(buildConsent(true))
+
+    bootstrapGoogleAnalytics(TEST_GA_ID)
+
+    expect(setGoogleConsentDefault).toHaveBeenCalledWith({ analytics_storage: 'granted' })
+    expect(loadGoogleAnalytics).toHaveBeenCalledWith(TEST_GA_ID)
+
+    const defaultOrder = vi.mocked(setGoogleConsentDefault).mock.invocationCallOrder[0]
+    const loadOrder = vi.mocked(loadGoogleAnalytics).mock.invocationCallOrder[0]
+    expect(defaultOrder).toBeLessThan(loadOrder)
+  })
+
+  it('seeds a denied default for a first-time or declining visitor', () => {
+    vi.mocked(retrieveConsentCategoriesFromCookies).mockReturnValue(buildConsent(false))
+
+    bootstrapGoogleAnalytics(TEST_GA_ID)
+
+    expect(setGoogleConsentDefault).toHaveBeenCalledWith({ analytics_storage: 'denied' })
+    expect(loadGoogleAnalytics).toHaveBeenCalledWith(TEST_GA_ID)
+  })
+
+  it('does nothing when no gaId is provided', () => {
+    bootstrapGoogleAnalytics('')
+
+    expect(retrieveConsentCategoriesFromCookies).not.toHaveBeenCalled()
+    expect(setGoogleConsentDefault).not.toHaveBeenCalled()
+    expect(loadGoogleAnalytics).not.toHaveBeenCalled()
+  })
+
+  it('is idempotent: does nothing when GA for the same gaId is already injected', () => {
+    vi.mocked(hasGoogleAnalyticsScript).mockReturnValue(true)
+
+    bootstrapGoogleAnalytics(TEST_GA_ID)
+
+    expect(hasGoogleAnalyticsScript).toHaveBeenCalledWith(TEST_GA_ID)
+    expect(retrieveConsentCategoriesFromCookies).not.toHaveBeenCalled()
+    expect(setGoogleConsentDefault).not.toHaveBeenCalled()
+    expect(loadGoogleAnalytics).not.toHaveBeenCalled()
+  })
+
+  it('re-initialises when only a script for a different gaId is present', () => {
+    // hasGoogleAnalyticsScript(gaId) reports false when the injected script
+    // targets a different measurement ID, so the bootstrap should proceed and
+    // let loadGoogleAnalytics update it.
+    vi.mocked(hasGoogleAnalyticsScript).mockReturnValue(false)
+
+    bootstrapGoogleAnalytics(TEST_GA_ID)
+
+    expect(hasGoogleAnalyticsScript).toHaveBeenCalledWith(TEST_GA_ID)
+    expect(loadGoogleAnalytics).toHaveBeenCalledWith(TEST_GA_ID)
+  })
+})
diff --git a/documentation-ui/src/custom/docs/components/analytics/bootstrap.ts b/documentation-ui/src/custom/docs/components/analytics/bootstrap.ts
new file mode 100644
index 0000000..8338698
--- /dev/null
+++ b/documentation-ui/src/custom/docs/components/analytics/bootstrap.ts
@@ -0,0 +1,43 @@
+/**
+ * One-time bootstrap for GA4 + Google Consent Mode v2, deliberately decoupled
+ * from React.
+ *
+ * Running the bootstrap from a React `useEffect` means GA is not initialised
+ * until after the tree has rendered, committed and flushed its passive effects,
+ * which on a heavy page delays the first `page_view` by hundreds of
+ * milliseconds. Because this helper (and the primitives it composes) have no
+ * React dependency, it can instead be invoked synchronously from a plain-JS
+ * entry point — e.g. the sphinx injection script, before the React root is
+ * mounted — so GA starts as early as the page's JavaScript can run.
+ */
+
+import { retrieveConsentCategoriesFromCookies } from '../gdpr/service/cookie-consent-service'
+import { CookieCategoryName } from '../gdpr/types'
+import {
+  hasGoogleAnalyticsScript,
+  loadGoogleAnalytics,
+  setGoogleConsentDefault,
+} from './consent-mode'
+
+/**
+ * Initialises GA once, seeding the consent default from the visitor's stored
+ * decision so a returning, already-consented visitor's first `page_view` is
+ * sent with consent granted (rather than going out cookieless and relying on a
+ * later `consent update`).
+ *
+ * Idempotent and safe to call from multiple entry points: the sphinx injection
+ * can call it synchronously before mounting React, and `GoogleAnalyticsWithConsent`
+ * calls it from an effect as a fallback for contexts without that injection
+ * (e.g. Next.js). Whichever runs first wins; subsequent calls are no-ops.
+ */
+export function bootstrapGoogleAnalytics(gaId: string): void {
+  if (!gaId || typeof document === 'undefined' || hasGoogleAnalyticsScript(gaId)) {
+    return
+  }
+
+  const analyticsGranted = retrieveConsentCategoriesFromCookies()[CookieCategoryName.Analytics]
+
+  // The consent default must be set before GA's config call.
+  setGoogleConsentDefault({ analytics_storage: analyticsGranted ? 'granted' : 'denied' })
+  loadGoogleAnalytics(gaId)
+}
diff --git a/documentation-ui/src/custom/docs/components/analytics/consent-mode.test.ts b/documentation-ui/src/custom/docs/components/analytics/consent-mode.test.ts
index 49937b6..52a99d7 100644
--- a/documentation-ui/src/custom/docs/components/analytics/consent-mode.test.ts
+++ b/documentation-ui/src/custom/docs/components/analytics/consent-mode.test.ts
@@ -2,6 +2,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import {
   DEFAULT_GOOGLE_CONSENT,
   ensureGtag,
+  hasGoogleAnalyticsScript,
   loadGoogleAnalytics,
   setGoogleConsentDefault,
   updateAnalyticsConsent,
@@ -75,7 +76,7 @@ describe('setGoogleConsentDefault', () => {
       ad_user_data: 'denied',
       ad_personalization: 'denied',
       analytics_storage: 'denied',
-      wait_for_update: 500,
+      wait_for_update: 100,
     })
   })
 
@@ -85,7 +86,7 @@ describe('setGoogleConsentDefault', () => {
     const settings = findCommand('consent', 'default')?.[2] as Record<string, unknown>
     expect(settings).toEqual({
       ...DEFAULT_GOOGLE_CONSENT,
-      wait_for_update: 500,
+      wait_for_update: 100,
     })
   })
 
@@ -170,3 +171,25 @@ describe('loadGoogleAnalytics', () => {
     expect(script?.src).toBe(`https://www.googletagmanager.com/gtag/js?id=${otherGaId}`)
   })
 })
+
+describe('hasGoogleAnalyticsScript', () => {
+  it('is false before any script is injected', () => {
+    expect(hasGoogleAnalyticsScript()).toBe(false)
+    expect(hasGoogleAnalyticsScript(TEST_GA_ID)).toBe(false)
+  })
+
+  it('is true once a script is present when no gaId is supplied', () => {
+    loadGoogleAnalytics(TEST_GA_ID)
+
+    expect(hasGoogleAnalyticsScript()).toBe(true)
+  })
+
+  it('matches only the gaId the injected script targets', () => {
+    loadGoogleAnalytics(TEST_GA_ID)
+
+    expect(hasGoogleAnalyticsScript(TEST_GA_ID)).toBe(true)
+    // A script left over from a different ID must not count as present, so the
+    // bootstrap re-runs and updates it.
+    expect(hasGoogleAnalyticsScript('G-OTHER67890')).toBe(false)
+  })
+})
diff --git a/documentation-ui/src/custom/docs/components/analytics/consent-mode.ts b/documentation-ui/src/custom/docs/components/analytics/consent-mode.ts
index 9281240..53e2de5 100644
--- a/documentation-ui/src/custom/docs/components/analytics/consent-mode.ts
+++ b/documentation-ui/src/custom/docs/components/analytics/consent-mode.ts
@@ -37,6 +37,32 @@ export const DEFAULT_GOOGLE_CONSENT: Required<Omit<GoogleConsentSettings, 'wait_
   analytics_storage: 'denied',
 }
 
+/** Builds the gtag.js script URL for a given measurement ID. */
+function gtagScriptUrl(gaId: string): string {
+  const scriptUrl = new URL('https://www.googletagmanager.com/gtag/js')
+  scriptUrl.searchParams.set('id', gaId)
+  return scriptUrl.toString()
+}
+
+/**
+ * Returns whether the gtag.js script has already been injected. When a `gaId`
+ * is supplied it is only considered present if the injected script targets that
+ * same ID, so callers can detect a script left over from a different ID and
+ * re-run initialisation to update it (see `loadGoogleAnalytics`).
+ */
+export function hasGoogleAnalyticsScript(gaId?: string): boolean {
+  if (typeof document === 'undefined') {
+    return false
+  }
+
+  const existingScript = document.getElementById(GA_SCRIPT_ID) as HTMLScriptElement | null
+  if (!existingScript) {
+    return false
+  }
+
+  return gaId === undefined || existingScript.src === gtagScriptUrl(gaId)
+}
+
 /** Ensures `window.dataLayer` / `window.gtag` exist and returns the gtag function. */
 export function ensureGtag(): GtagFn | undefined {
   if (typeof window === 'undefined') {
@@ -71,7 +97,7 @@ export function setGoogleConsentDefault(overrides: GoogleConsentSettings = {}):
 
   gtag('consent', 'default', {
     ...DEFAULT_GOOGLE_CONSENT,
-    wait_for_update: 500,
+    wait_for_update: 100,
     ...overrides,
   })
 }
@@ -105,13 +131,12 @@ export function loadGoogleAnalytics(gaId: string): void {
   gtag('js', new Date())
   gtag('config', gaId)
 
-  const scriptUrl = new URL('https://www.googletagmanager.com/gtag/js')
-  scriptUrl.searchParams.set('id', gaId)
+  const src = gtagScriptUrl(gaId)
 
   const existingScript = document.getElementById(GA_SCRIPT_ID) as HTMLScriptElement | null
   if (existingScript) {
-    if (existingScript.src !== scriptUrl.toString()) {
-      existingScript.src = scriptUrl.toString()
+    if (existingScript.src !== src) {
+      existingScript.src = src
     }
     return
   }
@@ -119,6 +144,6 @@ export function loadGoogleAnalytics(gaId: string): void {
   const script = document.createElement('script')
   script.id = GA_SCRIPT_ID
   script.async = true
-  script.src = scriptUrl.toString()
+  script.src = src
   document.head.appendChild(script)
 }
diff --git a/documentation-ui/src/custom/docs/components/analytics/index.ts b/documentation-ui/src/custom/docs/components/analytics/index.ts
index eea0996..d10a1ce 100644
--- a/documentation-ui/src/custom/docs/components/analytics/index.ts
+++ b/documentation-ui/src/custom/docs/components/analytics/index.ts
@@ -1,2 +1,3 @@
+export * from './bootstrap'
 export * from './consent-mode'
 export * from './GoogleAnalyticsWithConsent'
diff --git a/sphinx-ui/react/src/injectNav.tsx b/sphinx-ui/react/src/injectNav.tsx
index 3d2cfa9..625a61b 100644
--- a/sphinx-ui/react/src/injectNav.tsx
+++ b/sphinx-ui/react/src/injectNav.tsx
@@ -1,5 +1,5 @@
 
-import { CookieConsentManager, CookieConsentProvider, DocsNavBar, GoogleAnalyticsWithConsent } from "@quantinuum/documentation-ui";
+import { bootstrapGoogleAnalytics, CookieConsentManager, CookieConsentProvider, DocsNavBar, GoogleAnalyticsWithConsent } from "@quantinuum/documentation-ui";
 import { createRoot } from "react-dom/client";
 
 const GA_ID = __NEXT_PUBLIC_GA_ID__;
@@ -53,6 +53,15 @@ const observeTailwindDialogPortalElements = () => {
 
   const analyticsEnabled = mountElement.getAttribute('data-analytics-enabled') === 'true'
 
+  // Bootstrap GA synchronously, before React mounts, so the first `page_view`
+  // is dispatched without waiting for hydration and passive-effect scheduling.
+  // The render below still includes GoogleAnalyticsWithConsent, whose bootstrap
+  // is idempotent (a no-op once this call has run) and which handles subsequent
+  // live consent changes.
+  if (analyticsEnabled && GA_ID) {
+    bootstrapGoogleAnalytics(GA_ID)
+  }
+
   observeTailwindDialogPortalElements()
 
   const renderIn = document.createElement('div')