diff --git a/client/package.json b/client/package.json
index 06f600acd..e1938a4bb 100644
--- a/client/package.json
+++ b/client/package.json
@@ -18,6 +18,7 @@
     "lint": "eslint .",
     "lint:check": "eslint .",
     "lint:pages": "node scripts/check-page-pattern.mjs",
+    "check:gl-split": "node scripts/check-gl-split.mjs",
     "theme:lint": "node scripts/theme-lint.mjs",
     "theme:lint:strict": "node scripts/theme-lint.mjs --strict",
     "e2e": "playwright test",
diff --git a/client/scripts/check-gl-split.mjs b/client/scripts/check-gl-split.mjs
new file mode 100644
index 000000000..31fa69862
--- /dev/null
+++ b/client/scripts/check-gl-split.mjs
@@ -0,0 +1,47 @@
+import { readdirSync, readFileSync, statSync } from 'node:fs'
+import { join } from 'node:path'
+
+/**
+ * Fails when a built chunk contains both WebGL map engines.
+ *
+ * mapbox-gl and maplibre-gl used to be static imports in the same three
+ * components, so rollup emitted a single 2.8 MB chunk carrying both. Every map
+ * user downloaded 1.8 MB of mapbox plus 1.1 MB of maplibre and ran one of them.
+ * A stray static import anywhere in the map tree brings that straight back, and
+ * nothing else would notice — the build stays green and the app still works.
+ *
+ * The markers are chosen to appear only inside the SDKs themselves, verified in
+ * node_modules. Do NOT test for the bare string "maplibre": the provider value
+ * 'maplibre-gl' and the setting key maplibre_style also appear in app code, so it
+ * matches the shared core chunk too.
+ */
+const DIR = 'dist/assets'
+const MAPBOX = 'events.mapbox.com' // 1 hit in mapbox-gl, 0 in maplibre-gl
+const MAPLIBRE = 'maplibregl-canvas' // 2 hits in maplibre-gl, 0 in mapbox-gl
+
+let mixed = 0
+let found = 0
+
+for (const file of readdirSync(DIR).filter(f => f.endsWith('.js'))) {
+  const path = join(DIR, file)
+  const src = readFileSync(path, 'utf8')
+  const hasMapbox = src.includes(MAPBOX)
+  const hasMaplibre = src.includes(MAPLIBRE)
+  if (!hasMapbox && !hasMaplibre) continue
+
+  found++
+  const size = statSync(path).size
+  if (hasMapbox && hasMaplibre) {
+    console.error(`FAIL  both GL engines in one chunk: ${file} (${size} B)`)
+    mixed++
+  } else {
+    console.log(`${hasMapbox ? 'mapbox  ' : 'maplibre'}  ${file}  ${size} B`)
+  }
+}
+
+if (!found) {
+  console.error('FAIL  no chunk contains either GL engine — did the build run?')
+  process.exit(1)
+}
+
+process.exit(mixed ? 1 : 0)
diff --git a/client/src/components/Files/FileManagerImageLightbox.test.tsx b/client/src/components/Files/FileManagerImageLightbox.test.tsx
index e49ff1f5f..f0c470860 100644
--- a/client/src/components/Files/FileManagerImageLightbox.test.tsx
+++ b/client/src/components/Files/FileManagerImageLightbox.test.tsx
@@ -182,11 +182,12 @@ describe('ImageLightbox', () => {
     expect(screen.getAllByRole('button')).toHaveLength(3)
   })
 
-  it('FE-W4LBX-015: a video plays in the player and never mints a download token', () => {
+  it('FE-W4LBX-015: a video plays in the player and never mints a download token', async () => {
     const video = file({ id: 9, original_name: 'clip.mp4', mime_type: 'video/mp4', url: '/f/clip.mp4' })
     const { container } = render(<ImageLightbox files={[video]} initialIndex={0} onClose={() => {}} />)
 
-    expect(screen.getByTestId('video')).toHaveAttribute('data-src', '/f/clip.mp4')
+    // The player loads on demand now — plyr no longer ships with the file manager.
+    expect(await screen.findByTestId('video')).toHaveAttribute('data-src', '/f/clip.mp4')
     expect(getAuthUrl).not.toHaveBeenCalled()
     expect(container.querySelector('img')).toBeNull()
   })
diff --git a/client/src/components/Files/FileManagerImageLightbox.tsx b/client/src/components/Files/FileManagerImageLightbox.tsx
index 0afaa127a..0b2b53911 100644
--- a/client/src/components/Files/FileManagerImageLightbox.tsx
+++ b/client/src/components/Files/FileManagerImageLightbox.tsx
@@ -5,7 +5,7 @@ import type { TripFile } from '../../types'
 import { getAuthUrl } from '../../api/authUrl'
 import { openFile as openFileUrl } from '../../utils/fileDownload'
 import { triggerDownload, isVideo } from './FileManager.helpers'
-import VideoPlayer from '../Journey/VideoPlayer'
+import VideoPlayer from '../Journey/VideoPlayerLazy'
 
 // Image lightbox with gallery navigation
 interface ImageLightboxProps {
diff --git a/client/src/components/Journey/JourneyMapAuto.tsx b/client/src/components/Journey/JourneyMapAuto.tsx
index 3e8c5c1c4..ab9332e1f 100644
--- a/client/src/components/Journey/JourneyMapAuto.tsx
+++ b/client/src/components/Journey/JourneyMapAuto.tsx
@@ -1,12 +1,10 @@
-import { forwardRef, lazy, Suspense, useImperativeHandle, useRef } from 'react'
+import { forwardRef, Suspense, useImperativeHandle, useRef } from 'react'
 import { useSettingsStore } from '../../store/settingsStore'
 import JourneyMap, { type JourneyMapHandle } from './JourneyMap'
 import ErrorBoundary from '../shared/ErrorBoundary'
 import type { JourneyMapGLHandle } from './JourneyMapGL'
 
-// Lazy-load the GL renderer (and its ~230 KB gzip engine) so Leaflet-only
-// installs never download it — it ships only once a GL provider is picked.
-const JourneyMapGL = lazy(() => import('./JourneyMapGL'))
+import { JourneyMapGLMapbox, JourneyMapGLMaplibre } from '../Map/glLazy'
 
 // Unified handle — both providers expose the same three methods.
 export type JourneyMapAutoHandle = JourneyMapHandle
@@ -52,12 +50,14 @@ const JourneyMapAuto = forwardRef<JourneyMapAutoHandle, Props>(function JourneyM
     invalidateSize: () => (useGL ? glRef.current : leafletRef.current)?.invalidateSize(),
   }), [useGL])
 
+  // One chunk per engine — see MapViewAuto.
+  const JourneyMapGL = glProvider === 'maplibre-gl' ? JourneyMapGLMaplibre : JourneyMapGLMapbox
   if (useGL) {
     return (
       // See MapViewAuto: the boundary has to sit outside the Suspense to catch a
       // chunk that never arrives.
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
-      <ErrorBoundary boundaryId="journey-map:gl" fallback={<JourneyMap ref={leafletRef} {...(props as any)} />}>
+      <ErrorBoundary boundaryId="journey-map:gl" resetKeys={[glProvider]} fallback={<JourneyMap ref={leafletRef} {...(props as any)} />}>
         <Suspense fallback={null}>
           {/* eslint-disable-next-line @typescript-eslint/no-explicit-any */}
           <JourneyMapGL ref={glRef} {...(props as any)} glProvider={glProvider} />
diff --git a/client/src/components/Journey/JourneyMapGL.test.tsx b/client/src/components/Journey/JourneyMapGL.test.tsx
index 193462a0b..ce4f473ce 100644
--- a/client/src/components/Journey/JourneyMapGL.test.tsx
+++ b/client/src/components/Journey/JourneyMapGL.test.tsx
@@ -119,9 +119,28 @@ import { render, screen, act } from '../../../tests/helpers/render'
 import { resetAllStores, seedStore } from '../../../tests/helpers/store'
 import { useSettingsStore } from '../../store/settingsStore'
 import { isStandardFamily, supportsCustom3d, wantsTerrain, addCustom3dBuildings, addTerrainAndSky } from '../Map/mapboxSetup'
-import JourneyMapGL from './JourneyMapGL'
+import JourneyMapGLWithEngine from './JourneyMapGL'
 import type { JourneyMapGLHandle } from './JourneyMapGL'
 
+// The engine is a prop now, not a module import — that is what keeps mapbox-gl and
+// maplibre-gl in separate chunks. This shim preserves the suite's existing call
+// shape and makes the same choice glLazy.tsx makes in production, so the vi.mock
+// factories below still stand in for the right SDK.
+const JourneyMapGL = React.forwardRef(function JourneyMapGLShim(
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  props: any,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  ref: any
+) {
+  return (
+    <JourneyMapGLWithEngine
+      ref={ref}
+      {...props}
+      gl={props.glProvider === 'maplibre-gl' ? maplibregl : mapboxgl}
+    />
+  )
+})
+
 const entries = [
   { id: 'e1', lat: 48.8566, lng: 2.3522, title: 'Louvre', location_name: 'Paris, France', entry_date: '2025-06-01', dayColor: '#ff0055', dayLabel: 2 },
   { id: 'e2', lat: 52.52, lng: 13.405, title: 'Museumsinsel', location_name: 'Berlin, Germany', entry_date: '2025-06-02' },
diff --git a/client/src/components/Journey/JourneyMapGL.tsx b/client/src/components/Journey/JourneyMapGL.tsx
index f3e585411..7a1c7c043 100644
--- a/client/src/components/Journey/JourneyMapGL.tsx
+++ b/client/src/components/Journey/JourneyMapGL.tsx
@@ -1,8 +1,5 @@
 import { useEffect, useRef, useImperativeHandle, forwardRef, useCallback } from 'react'
-import mapboxgl from 'mapbox-gl'
-import maplibregl from 'maplibre-gl'
-import 'mapbox-gl/dist/mapbox-gl.css'
-import 'maplibre-gl/dist/maplibre-gl.css'
+import type mapboxgl from 'mapbox-gl'
 import { useSettingsStore } from '../../store/settingsStore'
 import { isStandardFamily, supportsCustom3d, wantsTerrain, addCustom3dBuildings, addTerrainAndSky } from '../Map/mapboxSetup'
 import { MAPBOX_DEFAULT_STYLE, styleForActiveProvider, basemapLanguage, type GlMapProvider } from '../Map/glProviders'
@@ -36,6 +33,13 @@ interface Props {
   fullScreen?: boolean
   paddingBottom?: number
   glProvider?: GlMapProvider
+  /**
+   * The GL engine, injected instead of imported. Both SDKs used to be pulled in
+   * statically here, so a single 2.8 MB chunk carried mapbox-gl and maplibre-gl
+   * together and every map user downloaded both while only one ever ran.
+   */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  gl: any
 }
 
 interface Item {
@@ -206,7 +210,7 @@ function markerHtml(dayColor: string, dayLabel: number, highlighted: boolean): H
 const EMPTY_TRAIL: { lat: number; lng: number }[] = []
 
 const JourneyMapGL = forwardRef<JourneyMapGLHandle, Props>(function JourneyMapGL(
-  { entries, trail, height = 220, dark, activeMarkerId, onMarkerClick, fullScreen, paddingBottom, glProvider = 'mapbox-gl' },
+  { entries, trail, height = 220, dark, activeMarkerId, onMarkerClick, fullScreen, paddingBottom, glProvider = 'mapbox-gl', gl },
   ref
 ) {
   const stableTrail = trail || EMPTY_TRAIL
@@ -217,7 +221,6 @@ const JourneyMapGL = forwardRef<JourneyMapGLHandle, Props>(function JourneyMapGL
   const mapboxQuality = useSettingsStore(s => s.settings.mapbox_quality_mode === true)
   const mapLang = useSettingsStore(s => s.settings.language)
   const isMapLibre = glProvider === 'maplibre-gl'
-  const gl = (isMapLibre ? maplibregl : mapboxgl) as any
   const glStyle = styleForActiveProvider(glProvider, rawMapboxStyle, rawMaplibreStyle)
   const enableMapbox3d = !isMapLibre && mapbox3d
   const containerRef = useRef<HTMLDivElement>(null)
@@ -344,7 +347,7 @@ const JourneyMapGL = forwardRef<JourneyMapGLHandle, Props>(function JourneyMapGL
   // inside the same effect so they stay in sync with the active style.
   useEffect(() => {
     if (!containerRef.current || (!isMapLibre && !mapboxToken)) return
-    if (!isMapLibre) mapboxgl.accessToken = mapboxToken
+    if (!isMapLibre) gl.accessToken = mapboxToken
 
     const items = buildItems(entries)
     itemsRef.current = items
diff --git a/client/src/components/Journey/PhotoLightbox.test.tsx b/client/src/components/Journey/PhotoLightbox.test.tsx
index a2dceb702..e66f821c1 100644
--- a/client/src/components/Journey/PhotoLightbox.test.tsx
+++ b/client/src/components/Journey/PhotoLightbox.test.tsx
@@ -151,14 +151,15 @@ describe('PhotoLightbox', () => {
     expect(screen.getByText('Mountain trail')).toBeInTheDocument();
   });
 
-  it('FE-COMP-LIGHTBOX-014: renders a video item through the player instead of an image', () => {
+  it('FE-COMP-LIGHTBOX-014: renders a video item through the player instead of an image', async () => {
     render(
       <PhotoLightbox
         photos={[{ id: 'v1', src: '/videos/1.mp4', caption: null, mediaType: 'video' }]}
         onClose={vi.fn()}
       />,
     );
-    expect(screen.getByTestId('video-player')).toHaveAttribute('src', '/videos/1.mp4');
+    // The player loads on demand now — plyr no longer ships with the journal.
+    expect(await screen.findByTestId('video-player')).toHaveAttribute('src', '/videos/1.mp4');
     expect(screen.queryByRole('img')).not.toBeInTheDocument();
   });
 
diff --git a/client/src/components/Journey/PhotoLightbox.tsx b/client/src/components/Journey/PhotoLightbox.tsx
index 8cf3da614..64f9202c6 100644
--- a/client/src/components/Journey/PhotoLightbox.tsx
+++ b/client/src/components/Journey/PhotoLightbox.tsx
@@ -1,6 +1,6 @@
 import { useState, useEffect, useCallback, useRef } from 'react'
 import { ChevronLeft, ChevronRight, X } from 'lucide-react'
-import VideoPlayer from './VideoPlayer'
+import VideoPlayer from './VideoPlayerLazy'
 
 interface LightboxPhoto {
   id: string
diff --git a/client/src/components/Journey/VideoPlayerLazy.tsx b/client/src/components/Journey/VideoPlayerLazy.tsx
new file mode 100644
index 000000000..2af91c8ea
--- /dev/null
+++ b/client/src/components/Journey/VideoPlayerLazy.tsx
@@ -0,0 +1,42 @@
+import { Suspense } from 'react'
+import type React from 'react'
+import { lazyWithRetry } from '../../utils/lazyWithRetry'
+import ErrorBoundary from '../shared/ErrorBoundary'
+
+/**
+ * Plyr (112 kB raw / 33 kB gzip of JS plus 32 kB / 5 kB of CSS) hung statically off
+ * three lightboxes, and through them off the FileManager, JournalBody and MTripShell
+ * chunks — downloaded with the route, whether or not a lightbox was ever opened and
+ * whether or not it held a video.
+ *
+ * The lightboxes only render the player on their video branch anyway, so the split
+ * costs one frame of placeholder and nothing else.
+ */
+const VideoPlayer = lazyWithRetry(() => import('./VideoPlayer'))
+
+export default function VideoPlayerLazy(props: React.ComponentProps<typeof VideoPlayer>) {
+  // A black rectangle in the target geometry rather than null, so the lightbox does
+  // not jump once the chunk lands.
+  const placeholder = (
+    <div
+      style={{
+        width: 'min(92vw, 1100px)',
+        aspectRatio: '16 / 9',
+        maxHeight: '92vh',
+        borderRadius: 4,
+        background: '#000',
+        ...props.style,
+      }}
+    />
+  )
+  return (
+    // Boundary outside the Suspense, as in MapViewAuto: Suspense owns the pending
+    // promise, a rejected one flies past it and would otherwise take the whole
+    // lightbox down with it.
+    <ErrorBoundary boundaryId="lightbox:video" level="panel" fallback={placeholder}>
+      <Suspense fallback={placeholder}>
+        <VideoPlayer {...props} />
+      </Suspense>
+    </ErrorBoundary>
+  )
+}
diff --git a/client/src/components/Map/MapViewAuto.tsx b/client/src/components/Map/MapViewAuto.tsx
index fba1d69c2..d9a5024ec 100644
--- a/client/src/components/Map/MapViewAuto.tsx
+++ b/client/src/components/Map/MapViewAuto.tsx
@@ -1,11 +1,8 @@
-import { lazy, Suspense } from 'react'
+import { Suspense } from 'react'
 import { useSettingsStore } from '../../store/settingsStore'
 import { MapView } from './MapView'
 import ErrorBoundary from '../shared/ErrorBoundary'
-
-// MapLibre/Mapbox pull in a ~230 KB (gzip) GL engine. Lazy-load the GL renderer so
-// Leaflet-only installs never download it — it ships only once a GL provider is picked.
-const MapViewGL = lazy(() => import('./MapViewGL').then(m => ({ default: m.MapViewGL })))
+import { MapViewGLMapbox, MapViewGLMaplibre } from './glLazy'
 
 // Auto-selects the map renderer based on user settings. Keeps the existing
 // Leaflet MapView untouched so the Mapbox GL variant can mature iteratively
@@ -24,6 +21,9 @@ export function MapViewAuto(props: any) {
   const glProvider = provider === 'maplibre-gl' ? 'maplibre-gl'
     : provider === 'mapbox-gl' && token ? 'mapbox-gl'
     : null
+  // One chunk per engine: picking the binding here is what keeps mapbox-gl and
+  // maplibre-gl out of each other's downloads.
+  const MapViewGL = glProvider === 'maplibre-gl' ? MapViewGLMaplibre : MapViewGLMapbox
   if (glProvider) {
     // Render the previous Leaflet map as the fallback so there's no blank flash
     // while the GL chunk loads on first use.
@@ -31,7 +31,9 @@ export function MapViewAuto(props: any) {
       // Outside the Suspense on purpose: Suspense handles the pending promise,
       // a rejected one (chunk gone after a deploy) throws past it. Falling back
       // to Leaflet keeps a usable map instead of an error card.
-      <ErrorBoundary boundaryId="map:gl" fallback={<MapView {...props} />}>
+      // resetKeys: with two engine chunks, a failure under one provider must not
+      // keep showing Leaflet after the user switches to the other.
+      <ErrorBoundary boundaryId="map:gl" resetKeys={[glProvider]} fallback={<MapView {...props} />}>
         <Suspense fallback={<MapView {...props} />}>
           <MapViewGL {...props} glProvider={glProvider} />
         </Suspense>
diff --git a/client/src/components/Map/MapViewGL.test.tsx b/client/src/components/Map/MapViewGL.test.tsx
index 86a1d5111..a8262dc4d 100644
--- a/client/src/components/Map/MapViewGL.test.tsx
+++ b/client/src/components/Map/MapViewGL.test.tsx
@@ -208,7 +208,17 @@ vi.mock('../../services/photoService', () => ({
   getAllThumbs: vi.fn(() => ({})),
 }))
 
-import { MapViewGL } from './MapViewGL'
+import mapboxgl from 'mapbox-gl'
+import { MapViewGL as MapViewGLWithEngine } from './MapViewGL'
+
+// The engine is a prop now, not a module import — that is what keeps mapbox-gl and
+// maplibre-gl in separate chunks. This shim preserves the suite's existing call
+// shape and makes the same choice glLazy.tsx makes in production, so the vi.mock
+// factories below still stand in for the right SDK.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function MapViewGL(props: any) {
+  return <MapViewGLWithEngine {...props} gl={props.glProvider === 'maplibre-gl' ? maplibregl : mapboxgl} />
+}
 import * as mapboxSetup from './mapboxSetup'
 import * as photoService from '../../services/photoService'
 import { ReservationMapboxOverlay } from './reservationsMapbox'
diff --git a/client/src/components/Map/MapViewGL.tsx b/client/src/components/Map/MapViewGL.tsx
index 6e95c306c..9482f9dab 100644
--- a/client/src/components/Map/MapViewGL.tsx
+++ b/client/src/components/Map/MapViewGL.tsx
@@ -1,9 +1,6 @@
 import { useEffect, useRef, useMemo, useState, createElement } from 'react'
 import { renderToStaticMarkup } from 'react-dom/server'
-import mapboxgl from 'mapbox-gl'
-import maplibregl from 'maplibre-gl'
-import 'mapbox-gl/dist/mapbox-gl.css'
-import 'maplibre-gl/dist/maplibre-gl.css'
+import type mapboxgl from 'mapbox-gl'
 import { useSettingsStore } from '../../store/settingsStore'
 import { useAuthStore } from '../../store/authStore'
 import { getCached, isLoading, fetchPhoto, onThumbReady, getAllThumbs } from '../../services/photoService'
@@ -120,6 +117,13 @@ interface Props {
   onPoiClick?: (poi: Poi) => void
   onViewportChange?: (bbox: { south: number; west: number; north: number; east: number }) => void
   glProvider?: GlMapProvider
+  /**
+   * The GL engine, injected instead of imported. Both SDKs used to be pulled in
+   * statically here, so a single 2.8 MB chunk carried mapbox-gl and maplibre-gl
+   * together and every map user downloaded both while only one ever ran.
+   */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  gl: any
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   onMapReady?: (map: any | null) => void
 }
@@ -357,6 +361,7 @@ export function MapViewGL({
   onPoiClick,
   onViewportChange,
   glProvider = 'mapbox-gl',
+  gl,
   onMapReady,
 }: Props) {
   const rawMapboxStyle = useSettingsStore(s => s.settings.mapbox_style || MAPBOX_DEFAULT_STYLE)
@@ -367,7 +372,6 @@ export function MapViewGL({
   const showEndpointLabels = useSettingsStore(s => s.settings.map_booking_labels) === true
   const mapLang = useSettingsStore(s => s.settings.language)
   const isMapLibre = glProvider === 'maplibre-gl'
-  const gl = (isMapLibre ? maplibregl : mapboxgl) as any
   const glStyle = styleForActiveProvider(glProvider, rawMapboxStyle, rawMaplibreStyle)
   const enableMapbox3d = !isMapLibre && mapbox3d
   const placesPhotosEnabled = useAuthStore(s => s.placesPhotosEnabled)
@@ -444,7 +448,7 @@ export function MapViewGL({
   // Build/rebuild the map on provider/style/token/3d change
   useEffect(() => {
     if (!containerRef.current || (!isMapLibre && !mapboxToken)) return
-    if (!isMapLibre) mapboxgl.accessToken = mapboxToken
+    if (!isMapLibre) gl.accessToken = mapboxToken
 
     // Open framed on the places rather than on the caller's default: a trip in Japan should
     // show Japan straight away, not the world view followed by a flight across the planet.
diff --git a/client/src/components/Map/engines/mapbox.ts b/client/src/components/Map/engines/mapbox.ts
new file mode 100644
index 000000000..f1e114494
--- /dev/null
+++ b/client/src/components/Map/engines/mapbox.ts
@@ -0,0 +1,11 @@
+import mapboxgl from 'mapbox-gl'
+import 'mapbox-gl/dist/mapbox-gl.css'
+
+/**
+ * The only module in the client that pulls mapbox-gl in at runtime.
+ *
+ * It has to stay reachable through `import('./engines/mapbox')` and nothing else:
+ * a static import from anywhere in the tree drags 1.8 MB into the parent chunk and
+ * quietly undoes the split. `npm run check:gl-split` fails on that.
+ */
+export default mapboxgl
diff --git a/client/src/components/Map/engines/maplibre.ts b/client/src/components/Map/engines/maplibre.ts
new file mode 100644
index 000000000..662c13994
--- /dev/null
+++ b/client/src/components/Map/engines/maplibre.ts
@@ -0,0 +1,13 @@
+import maplibregl from 'maplibre-gl'
+import 'maplibre-gl/dist/maplibre-gl.css'
+
+/**
+ * The only module in the client that pulls maplibre-gl in at runtime. Same rule as
+ * its mapbox sibling: reachable through a dynamic import and no other way.
+ *
+ * The two engines share their API surface for everything TREK uses — Map, Marker,
+ * Popup, LngLatBounds — which is why the components take the engine as a prop and
+ * stay engine-agnostic. Where the two genuinely differ, the caller already guards
+ * on the provider (projection, accessToken, aroundCenter).
+ */
+export default maplibregl
diff --git a/client/src/components/Map/glLazy.tsx b/client/src/components/Map/glLazy.tsx
new file mode 100644
index 000000000..870095475
--- /dev/null
+++ b/client/src/components/Map/glLazy.tsx
@@ -0,0 +1,86 @@
+import { forwardRef } from 'react'
+import { lazyWithRetry } from '../../utils/lazyWithRetry'
+
+/**
+ * The six ways into a GL map, one chunk per engine.
+ *
+ * mapbox-gl and maplibre-gl used to be static imports inside MapViewGL,
+ * JourneyMapGL and the settings preview, so rollup put both SDKs into a single
+ * 2.8 MB chunk. Every map user downloaded 1.8 MB of mapbox plus 1.1 MB of
+ * maplibre and then ran exactly one of them.
+ *
+ * Pairing the component with its engine behind the lazy boundary is what
+ * separates them: no module reaches both SDKs statically any more, so rolldown
+ * emits one shared core chunk and two engine chunks. The engine arrives as a
+ * prop — see the `gl` prop on each component.
+ *
+ * Both imports start together rather than in sequence: the engine is by far the
+ * larger of the two, and waiting for the component first would add its round
+ * trip in front of the download that actually costs time.
+ */
+
+export const MapViewGLMapbox = lazyWithRetry(async () => {
+  const [component, engine] = await Promise.all([import('./MapViewGL'), import('./engines/mapbox')])
+  const MapViewGL = component.MapViewGL
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  return { default: (props: any) => <MapViewGL {...props} gl={engine.default} /> }
+})
+
+export const MapViewGLMaplibre = lazyWithRetry(async () => {
+  const [component, engine] = await Promise.all([import('./MapViewGL'), import('./engines/maplibre')])
+  const MapViewGL = component.MapViewGL
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  return { default: (props: any) => <MapViewGL {...props} gl={engine.default} /> }
+})
+
+export const JourneyMapGLMapbox = lazyWithRetry(async () => {
+  const [component, engine] = await Promise.all([
+    import('../Journey/JourneyMapGL'),
+    import('./engines/mapbox'),
+  ])
+  const JourneyMapGL = component.default
+  return {
+    // forwardRef because the journey map exposes an imperative handle
+    // (highlightMarker / focusMarker / invalidateSize) that has to survive the wrapper.
+    /* eslint-disable @typescript-eslint/no-explicit-any */
+    default: forwardRef(function JourneyMapGLMapboxBinding(props: any, ref: any) {
+      return <JourneyMapGL ref={ref} {...props} gl={engine.default} />
+    }),
+    /* eslint-enable @typescript-eslint/no-explicit-any */
+  }
+})
+
+export const JourneyMapGLMaplibre = lazyWithRetry(async () => {
+  const [component, engine] = await Promise.all([
+    import('../Journey/JourneyMapGL'),
+    import('./engines/maplibre'),
+  ])
+  const JourneyMapGL = component.default
+  return {
+    /* eslint-disable @typescript-eslint/no-explicit-any */
+    default: forwardRef(function JourneyMapGLMaplibreBinding(props: any, ref: any) {
+      return <JourneyMapGL ref={ref} {...props} gl={engine.default} />
+    }),
+    /* eslint-enable @typescript-eslint/no-explicit-any */
+  }
+})
+
+export const GlMapPreviewMapbox = lazyWithRetry(async () => {
+  const [component, engine] = await Promise.all([
+    import('../Settings/MapboxPreview'),
+    import('./engines/mapbox'),
+  ])
+  const GlMapPreview = component.default
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  return { default: (props: any) => <GlMapPreview {...props} gl={engine.default} /> }
+})
+
+export const GlMapPreviewMaplibre = lazyWithRetry(async () => {
+  const [component, engine] = await Promise.all([
+    import('../Settings/MapboxPreview'),
+    import('./engines/maplibre'),
+  ])
+  const GlMapPreview = component.default
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  return { default: (props: any) => <GlMapPreview {...props} gl={engine.default} /> }
+})
diff --git a/client/src/components/Settings/MapSettingsTab.tsx b/client/src/components/Settings/MapSettingsTab.tsx
index b7ae3fd23..b6dfaf58d 100644
--- a/client/src/components/Settings/MapSettingsTab.tsx
+++ b/client/src/components/Settings/MapSettingsTab.tsx
@@ -1,14 +1,14 @@
-import React, { useState, useEffect, useMemo, useRef, lazy, Suspense } from 'react'
+import React, { useState, useEffect, useMemo, useRef, Suspense } from 'react'
 import { Map, Save, Layers, Box, ChevronDown, Check, Globe2 } from 'lucide-react'
 import { useTranslation } from '../../i18n'
 import { useSettingsStore } from '../../store/settingsStore'
 import { useToast } from '../shared/Toast'
 import CustomSelect from '../shared/CustomSelect'
 import { MapView } from '../Map/MapView'
-// The preview is the only place that imports both GL engines eagerly, which put
-// them in the entry chunk and cancelled out the lazy split in MapViewAuto. Load
-// it on demand so a Leaflet-only install never pays for them.
-const GlMapPreview = lazy(() => import('./MapboxPreview'))
+// The preview loads on demand, and paired with a single engine — a Leaflet-only
+// install pays for neither, and a GL install pays for one instead of both.
+import ErrorBoundary from '../shared/ErrorBoundary'
+import { GlMapPreviewMapbox, GlMapPreviewMaplibre } from '../Map/glLazy'
 import Section from './Section'
 import ToggleSwitch from './ToggleSwitch'
 import type { Place } from '../../types'
@@ -165,6 +165,8 @@ export default function MapSettingsTab(): React.ReactElement {
   const [mapboxStyle, setMapboxStyle] = useState<string>(styleForProvider(initialProvider, slotStyle(initialProvider, settings)))
   const [mapbox3d, setMapbox3d] = useState<boolean>(settings.mapbox_3d_enabled !== false)
   const [mapboxQuality, setMapboxQuality] = useState<boolean>(settings.mapbox_quality_mode === true)
+  // One chunk per engine — see components/Map/glLazy.tsx.
+  const GlMapPreview = provider === 'maplibre-gl' ? GlMapPreviewMaplibre : GlMapPreviewMapbox
 
   useEffect(() => {
     const nextProvider = normalizeProvider(settings.map_provider)
@@ -402,6 +404,10 @@ export default function MapSettingsTab(): React.ReactElement {
       <div>
         <div style={{ position: 'relative', inset: 0, height: '200px', width: '100%' }}>
           {provider !== 'leaflet' ? (
+            /* A net of its own: the preview is the one place a user flips providers
+               live, so it is the likeliest chunk to fail — and a broken preview must
+               not take the rest of the settings tab with it. */
+            <ErrorBoundary boundaryId="settings:map-preview" resetKeys={[provider]} fallback={<div className="h-full w-full bg-surface-secondary" />}>
             <Suspense fallback={<div className="h-full w-full bg-surface-secondary animate-pulse" />}>
               <GlMapPreview
                 provider={provider}
@@ -416,6 +422,7 @@ export default function MapSettingsTab(): React.ReactElement {
                 quality={provider === 'mapbox-gl' && mapboxQuality}
               />
             </Suspense>
+            </ErrorBoundary>
           ) : (
             // eslint-disable-next-line @typescript-eslint/no-explicit-any
             React.createElement(MapView as any, {
diff --git a/client/src/components/Settings/MapboxPreview.test.tsx b/client/src/components/Settings/MapboxPreview.test.tsx
index 882303667..b028225e6 100644
--- a/client/src/components/Settings/MapboxPreview.test.tsx
+++ b/client/src/components/Settings/MapboxPreview.test.tsx
@@ -44,7 +44,18 @@ vi.mock('../Map/mapboxSetup', () => ({
 
 import { isStandardFamily, supportsCustom3d, addCustom3dBuildings, addTerrainAndSky } from '../Map/mapboxSetup';
 import { MAPBOX_DEFAULT_STYLE, OPENFREEMAP_DEFAULT_STYLE } from '../Map/glProviders';
-import GlMapPreview from './MapboxPreview';
+import mapboxgl from 'mapbox-gl';
+import maplibregl from 'maplibre-gl';
+import GlMapPreviewWithEngine from './MapboxPreview';
+
+// The engine is a prop now, not a module import — that is what keeps mapbox-gl and
+// maplibre-gl in separate chunks. This shim preserves the suite's existing call
+// shape and makes the same choice glLazy.tsx makes in production, so the vi.mock
+// factories below still stand in for the right SDK.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function GlMapPreview(props: any) {
+  return <GlMapPreviewWithEngine {...props} gl={props.provider === 'maplibre-gl' ? maplibregl : mapboxgl} />;
+}
 
 const STREETS = 'mapbox://styles/mapbox/streets-v12';
 
diff --git a/client/src/components/Settings/MapboxPreview.tsx b/client/src/components/Settings/MapboxPreview.tsx
index d3f0a33f3..e5606e719 100644
--- a/client/src/components/Settings/MapboxPreview.tsx
+++ b/client/src/components/Settings/MapboxPreview.tsx
@@ -1,8 +1,4 @@
 import { useEffect, useRef } from 'react'
-import mapboxgl from 'mapbox-gl'
-import maplibregl from 'maplibre-gl'
-import 'mapbox-gl/dist/mapbox-gl.css'
-import 'maplibre-gl/dist/maplibre-gl.css'
 import { isStandardFamily, supportsCustom3d, addCustom3dBuildings, addTerrainAndSky } from '../Map/mapboxSetup'
 import { MAPBOX_DEFAULT_STYLE, normalizeStyleForProvider, type GlMapProvider } from '../Map/glProviders'
 
@@ -16,22 +12,28 @@ interface Props {
   enable3d: boolean
   quality?: boolean
   onClick?: (latlng: { lat: number; lng: number }) => void
+  /**
+   * The GL engine, injected instead of imported. Both SDKs used to be pulled in
+   * statically here, so a single 2.8 MB chunk carried mapbox-gl and maplibre-gl
+   * together and every map user downloaded both while only one ever ran.
+   */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  gl: any
 }
 
-export default function GlMapPreview({ provider = 'mapbox-gl', token = '', style, lat, lng, zoom, enable3d, quality = false, onClick }: Props) {
+export default function GlMapPreview({ provider = 'mapbox-gl', token = '', style, lat, lng, zoom, enable3d, quality = false, onClick, gl }: Props) {
   const containerRef = useRef<HTMLDivElement>(null)
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   const mapRef = useRef<any | null>(null)
   const onClickRef = useRef(onClick)
   onClickRef.current = onClick
   const isMapLibre = provider === 'maplibre-gl'
-  const gl = (isMapLibre ? maplibregl : mapboxgl) as any
   const glStyle = normalizeStyleForProvider(provider, style)
   const enableMapbox3d = !isMapLibre && enable3d
 
   useEffect(() => {
     if (!containerRef.current || (!isMapLibre && !token)) return
-    if (!isMapLibre) mapboxgl.accessToken = token
+    if (!isMapLibre) gl.accessToken = token
 
     const mapOptions: Record<string, unknown> = {
       container: containerRef.current,
diff --git a/client/src/components/Vacay/holidayRegions.ts b/client/src/components/Vacay/holidayRegions.ts
index 46d85f1bb..7ca5e9c5a 100644
--- a/client/src/components/Vacay/holidayRegions.ts
+++ b/client/src/components/Vacay/holidayRegions.ts
@@ -1,5 +1,4 @@
 import apiClient from '../../api/client'
-import iso31662 from 'iso-3166-2'
 import { SCHOOL_HOLIDAY_COUNTRY_CONFIG } from '../../vacay/schoolHolidayCountries'
 
 // Loads the subdivision (state/region) options for a holiday-calendar country.
@@ -17,6 +16,13 @@ export async function fetchRegionOptions(country: string): Promise<{ value: stri
     const hasRegions = r.data.some(h => h.counties && h.counties.length > 0)
     if (!hasRegions) return []
 
+    // Loaded here, after the hasRegions check: the package is a single 238 kB data
+    // blob (64 kB gzip, no tree-shaking to be had) and is only needed for countries
+    // that get a region picker at all. Deliberately inside the try — if the chunk
+    // fails, the result is the same empty array as a failed request, rather than an
+    // unhandled rejection in the two callers that only do .then(setRegions).
+    const iso31662 = (await import('iso-3166-2')).default
+
     const opts = new Map<string, string>() // ISO code -> display name
     const sub = iso31662.country(country)?.sub || {}
     for (const [code, info] of Object.entries(sub)) opts.set(code, info.name)
diff --git a/client/src/mobile/screens/settings/MSettingsMap.tsx b/client/src/mobile/screens/settings/MSettingsMap.tsx
index e8bf5bda8..0a8682056 100644
--- a/client/src/mobile/screens/settings/MSettingsMap.tsx
+++ b/client/src/mobile/screens/settings/MSettingsMap.tsx
@@ -1,12 +1,12 @@
-import React, { useEffect, useMemo, useState, lazy, Suspense } from 'react'
+import React, { useEffect, useMemo, useState, Suspense } from 'react'
 import { Box, Check, ChevronDown, Globe2, Layers, Map, Save } from 'lucide-react'
 import { useTranslation } from '../../../i18n'
 import { useSettingsStore } from '../../../store/settingsStore'
 import { useToast } from '../../../components/shared/Toast'
 import { MapView } from '../../../components/Map/MapView'
-// Lazy for the same reason as the desktop map settings tab: this import is what
-// dragged both GL engines into the entry chunk.
-const GlMapPreview = lazy(() => import('../../../components/Settings/MapboxPreview'))
+// Same as the desktop map settings tab: on demand, and paired with one engine.
+import ErrorBoundary from '../../../components/shared/ErrorBoundary'
+import { GlMapPreviewMapbox, GlMapPreviewMaplibre } from '../../../components/Map/glLazy'
 import type { Place } from '../../../types'
 import {
   MAPBOX_DEFAULT_STYLE,
@@ -145,6 +145,9 @@ export default function MSettingsMap() {
   const selectedPreset = presets.find((p) => p.url === mapboxStyle)
   const chevron = <ChevronDown size={13} strokeWidth={2} className="flex-none text-m-faint" />
 
+  // One chunk per engine — see components/Map/glLazy.tsx.
+  const GlMapPreview = provider === 'maplibre-gl' ? GlMapPreviewMaplibre : GlMapPreviewMapbox
+
   return (
     <MSetCard title={t('settings.map')} icon={Map}>
       <MSetEyebrow className="mb-[6px]">{t('settings.mapProvider')}</MSetEyebrow>
@@ -251,6 +254,8 @@ export default function MSettingsMap() {
 
       <div className="relative mt-3 h-[200px] w-full overflow-hidden rounded-xl">
         {provider !== 'leaflet' ? (
+          /* See MapSettingsTab: the preview gets its own net. */
+          <ErrorBoundary boundaryId="settings:map-preview" resetKeys={[provider]} fallback={<div className="h-full w-full bg-m-card" />}>
           <Suspense fallback={<div className="h-full w-full bg-m-card animate-pulse" />}>
             <GlMapPreview
               provider={provider}
@@ -263,6 +268,7 @@ export default function MSettingsMap() {
               quality={provider === 'mapbox-gl' && mapboxQuality}
             />
           </Suspense>
+          </ErrorBoundary>
         ) : (
           // eslint-disable-next-line @typescript-eslint/no-explicit-any
           React.createElement(MapView as any, {
diff --git a/client/src/mobile/screens/trip/tabs/MFileLightbox.tsx b/client/src/mobile/screens/trip/tabs/MFileLightbox.tsx
index 78e940420..9b3c6829f 100644
--- a/client/src/mobile/screens/trip/tabs/MFileLightbox.tsx
+++ b/client/src/mobile/screens/trip/tabs/MFileLightbox.tsx
@@ -4,7 +4,7 @@ import { ChevronLeft, ChevronRight, Download, ExternalLink, X } from 'lucide-rea
 import { getAuthUrl } from '../../../../api/authUrl'
 import { downloadFile, openFile } from '../../../../utils/fileDownload'
 import { isVideo } from '../../../../components/Files/FileManager.helpers'
-import VideoPlayer from '../../../../components/Journey/VideoPlayer'
+import VideoPlayer from '../../../../components/Journey/VideoPlayerLazy'
 import type { TranslationFn, TripFile } from '../../../../types'
 
 interface MFileLightboxProps {