diff --git a/ui/PLAN.md b/ui/PLAN.md
index a42f28a..f9b7a3e 100644
--- a/ui/PLAN.md
+++ b/ui/PLAN.md
@@ -3235,8 +3235,9 @@ Targeted tests:
 - `tests/map-hit-test.test.ts` — `hitTest` honours the
   `hiddenIds` parameter;
 - `tests/e2e/map-toggles.spec.ts` — cascade, fog, wrap-mode
-  camera preservation, reload persistence across the four
-  Playwright projects.
+  camera preservation, reload persistence, plus render-on-demand
+  (an idle map does not repaint; a released drag does not coast)
+  across the four Playwright projects.
 
 Decisions:
 
@@ -3278,6 +3279,23 @@ Decisions:
    `FligthDistance`; the Phase 29 work renamed it to
    `FlightDistance` (and the only TS call site duplicates the
    formula directly, awaiting a future race-level WASM bridge).
+8. **Render-on-demand + no pan inertia (fog perf, stage 1).** The
+   renderer originally kept Pixi's continuous auto-render loop, so
+   the visibility fog's layered overpaint re-rasterised every frame
+   and froze the whole UI on large reports in Safari (Pixi's WebGPU
+   backend) — even while idle. The renderer now stops the auto-render
+   loop (`app.stop()`) and paints on demand: a single `Ticker.shared`
+   flush renders only when `viewport.dirty` (camera moved) or an
+   internal `requestRender()` fires from a content mutation
+   (`setVisibilityFog` / `setHiddenPrimitiveIds` /
+   `setExtraPrimitives` / `applyMode` / `resize` / pick overlay);
+   plain hover paints nothing. The `decelerate` (drag-inertia) plugin
+   is removed so a released drag stops instantly and the viewport
+   goes idle immediately. `RendererHandle.getRenderCount()` (mirrored
+   on `__galaxyDebug` as `getMapRenderCount`) backs the e2e
+   assertions. If Safari pan is still heavy after this, stage 2 cuts
+   the overpaint itself (an inverse stencil mask of the circle union,
+   kept vector so the map stays crisp at any zoom).
 
 ## Phase 30. Calculator Tab
 
diff --git a/ui/docs/renderer.md b/ui/docs/renderer.md
index fca2463..30b60d9 100644
--- a/ui/docs/renderer.md
+++ b/ui/docs/renderer.md
@@ -186,10 +186,12 @@ zoom. The math is symmetric and tested in
   cascades through the array and falls back to whichever backend
   initialises successfully.
 - **`pixi-viewport@^6`** — pan/zoom/pinch plugin layer over a
-  Pixi `Container`. Provides drag inertia, mobile gestures, and
-  the `clamp`/`clampZoom` plugins out of the box. We disable the
+  Pixi `Container`. Provides drag, mobile gestures, and the
+  `clamp`/`clampZoom` plugins out of the box. We disable the
   plugins we do not need (`bounce`, `snap`, `follow`,
-  `mouse-edges`).
+  `mouse-edges`) and deliberately omit `decelerate`: a released
+  drag stops immediately instead of coasting, which also lets
+  render-on-demand (below) go idle the moment the pointer is up.
 
 No additional dependencies are necessary. The deprecated
 `pixi.js`-v7 era `pixi-viewport` v5 contracts have been replaced
@@ -212,13 +214,45 @@ The selected backend is exposed via `[data-backend]` on the
 playground page header so the e2e spec can assert it without
 poking Pixi internals.
 
+## Render-on-demand
+
+Pixi's continuous auto-render loop is stopped right after
+`Application.init` (`app.stop()`). Frames are painted explicitly by
+a single gated flush added to `Ticker.shared` — the same ticker
+pixi-viewport already drives, so no second timer is created:
+
+```ts
+if (viewport.dirty || contentDirty) { app.render(); /* reset both */ }
+```
+
+- `viewport.dirty` is maintained by pixi-viewport's own update and
+  covers every camera change (drag / wheel / pinch, the torus and
+  no-wrap `moved` listeners, programmatic `moveCenter`).
+- `contentDirty` is set by an internal `requestRender()` from every
+  scene-graph mutation that does not move the camera:
+  `setVisibilityFog`, `setHiddenPrimitiveIds`, `setExtraPrimitives`,
+  `applyMode`, `resize`, and the pick-mode overlay redraw.
+- Plain hover mutates no `Graphics`, so moving the cursor over the
+  map paints nothing.
+
+An idle map therefore does zero GPU work per frame. This matters
+for the visibility fog: its layered overpaint is fill-heavy, and a
+continuously re-rendered fog froze the whole UI on large reports in
+Safari (Pixi's WebGPU backend). `RendererHandle.getRenderCount()`
+exposes the painted-frame count; the `map-toggles` e2e spec asserts
+with it that an idle map does not repaint and that a released drag
+does not coast.
+
 ## Performance acceptance
 
 The "60 fps with 1000 primitives" criterion is documented but
 manually verified, not asserted in CI. CI runners vary too much
 in CPU/GPU to make wall-clock fps reliable. Manual gate: open
-`/__debug/map`, drag continuously for 5 seconds, observe Pixi's
-ticker FPS in DevTools (Pixi exposes `app.ticker.FPS`).
+`/__debug/map`, drag continuously for 5 seconds, and watch the
+frame rate in the browser DevTools rendering meter (the app ticker
+is stopped under render-on-demand, so `app.ticker.FPS` no longer
+tracks paints — frames land via the `Ticker.shared` flush only
+while the camera is moving).
 
 If a future regression requires a programmatic perf gate, the
 right place is a Tier 2 (release-line) Playwright trace measuring
@@ -299,34 +333,40 @@ Phase 29 fog overlay used to highlight the player's visible
 hyperspace. Each entry describes a circle around a LOCAL planet
 where the player has scanner / visibility coverage:
 
-- An empty list destroys the existing fog Graphics.
-- A non-empty list creates one fog `Graphics` per torus copy.
-  Each draws a world-sized rectangle filled with `FOG_COLOR` (two
-  shades lighter than the dark theme background), then paints an
-  opaque background-coloured circle on top for every visibility
-  circle. The overpaint order naturally unions overlapping circles
-  — earlier iterations used Pixi v8's `Graphics.cut()` to subtract
-  holes, but `cut()` produces incorrect unions for multiple
-  overlapping holes; layered repainting trades one extra fill per
-  circle for a predictable, geometry-free union.
-- The fog is inserted at the bottom of each copy's z-order so
+- An empty list destroys the existing fog `Graphics`.
+- A non-empty list rebuilds a single viewport-level `fogLayer` (a
+  sibling that sits below the nine torus copies, not a child of
+  them). `fogPaintOps` returns an ordered op list — one world-sized
+  rectangle filled with `FOG_COLOR` (two shades lighter than the
+  dark theme background), then an opaque background-coloured circle
+  for every visibility circle — and the renderer dispatches each op
+  onto its own `Graphics`. The overpaint order naturally unions
+  overlapping circles — earlier iterations used Pixi v8's
+  `Graphics.cut()` to subtract holes, but `cut()` produces incorrect
+  unions for multiple overlapping holes; layered repainting trades
+  one extra fill per circle for a predictable, geometry-free union.
+- The ops carry world-space positions, so wrap mode is baked into
+  the op list rather than into copy visibility: `torus` emits the
+  rectangle and every circle at the nine `{-1,0,1}²` tile offsets;
+  `no-wrap` emits only the central tile. `fogLayer` has no transform.
+- The fog layer sits below every primitive copy in z-order, so
   primitives paint on top.
 - The fog never participates in hit-test. Planet glyphs sit on
   top of fog, so clicks on visible planets work unchanged.
-- Wrap mode is honoured for free — `applyMode` hides every
-  non-origin copy in `no-wrap`, so the fog inherits the same
-  behaviour because the fog Graphics is a child of each copy.
 
 The map view recomputes the fog input only when the report or the
-`visibleHyperspace` toggle changes — per-frame cost stays at zero.
+`visibleHyperspace` toggle changes, and under render-on-demand a
+static fog paints no frames at all — the layered overpaint cost is
+only paid on the frames where the camera is actually moving.
 
 ## Debug surface
 
 The DEV-only `__galaxyDebug` object (defined in
 `routes/__debug/store/+page.svelte`) exposes
-`getMapPrimitives()`, `getMapPickState()`, `getMapCamera()`, and
-`getMapFog()` so e2e specs can assert the renderer's current
-state without scraping pixels:
+`getMapPrimitives()`, `getMapPickState()`, `getMapCamera()`,
+`getMapFog()`, `getMapMode()`, and `getMapRenderCount()` so e2e
+specs can assert the renderer's current state without scraping
+pixels:
 
 - `getMapPrimitives()` returns a snapshot of every primitive in
   the active world: id, kind, priority, current alpha
@@ -342,10 +382,18 @@ state without scraping pixels:
 - `getMapFog()` returns the most recent fog input
   (the list of circles last passed to `setVisibilityFog`).
   Empty when the `visibleHyperspace` toggle is off.
+- `getMapMode()` returns the renderer's current `WrapMode`
+  (`'torus'` or `'no-wrap'`), used to await the remount after a
+  wrap-mode flip.
+- `getMapRenderCount()` returns the painted-frame count. Under
+  render-on-demand it stays flat while the map is idle and advances
+  only on camera moves or content mutations, so e2e specs can prove
+  the idle map is not repainting.
 
 The active map view registers providers on mount via
 `registerMapPrimitivesProvider` / `registerMapPickStateProvider`
-/ `registerMapCameraProvider` / `registerMapFogProvider` in
+/ `registerMapCameraProvider` / `registerMapFogProvider` /
+`registerMapModeProvider` / `registerMapRenderCountProvider` in
 `src/lib/debug-surface.svelte.ts`, deregisters on dispose, and
 the surface invokes them lazily on every read.
 
diff --git a/ui/frontend/src/lib/active-view/map.svelte b/ui/frontend/src/lib/active-view/map.svelte
index 914415d..6b0ec37 100644
--- a/ui/frontend/src/lib/active-view/map.svelte
+++ b/ui/frontend/src/lib/active-view/map.svelte
@@ -72,6 +72,7 @@ preference the store already manages.
 		registerMapModeProvider,
 		registerMapPickStateProvider,
 		registerMapPrimitivesProvider,
+		registerMapRenderCountProvider,
 		type MapCameraSnapshot,
 		type MapFogSnapshot,
 		type MapPickStateSnapshot,
@@ -536,12 +537,16 @@ preference the store already manages.
 			const detachMode = registerMapModeProvider(() =>
 				handle === null ? null : handle.getMode(),
 			);
+			const detachRenderCount = registerMapRenderCountProvider(() =>
+				handle === null ? null : handle.getRenderCount(),
+			);
 			detachDebugProviders = (): void => {
 				detachPrim();
 				detachPick();
 				detachCamera();
 				detachFog();
 				detachMode();
+				detachRenderCount();
 			};
 			mountedTurn = report.turn;
 			mountedGameId = targetGameId;
diff --git a/ui/frontend/src/lib/debug-surface.svelte.ts b/ui/frontend/src/lib/debug-surface.svelte.ts
index 41b4afb..1c0d0c4 100644
--- a/ui/frontend/src/lib/debug-surface.svelte.ts
+++ b/ui/frontend/src/lib/debug-surface.svelte.ts
@@ -74,12 +74,14 @@ type PickStateProvider = () => MapPickStateSnapshot;
 type CameraProvider = () => MapCameraSnapshot | null;
 type FogProvider = () => MapFogSnapshot;
 type ModeProvider = () => WrapMode | null;
+type RenderCountProvider = () => number | null;
 
 let primitivesProvider: PrimitivesProvider | null = null;
 let pickStateProvider: PickStateProvider | null = null;
 let cameraProvider: CameraProvider | null = null;
 let fogProvider: FogProvider | null = null;
 let modeProvider: ModeProvider | null = null;
+let renderCountProvider: RenderCountProvider | null = null;
 
 /**
  * registerMapPrimitivesProvider attaches a provider that yields the
@@ -152,6 +154,23 @@ export function registerMapModeProvider(provider: ModeProvider): () => void {
 	};
 }
 
+/**
+ * registerMapRenderCountProvider attaches a provider that yields the
+ * renderer's actual painted-frame count. Because the renderer runs
+ * render-on-demand, the count stays flat while the map is idle and
+ * only advances on camera moves or content mutations. e2e specs use
+ * it to assert the idle map does not keep repainting. Same idempotent
+ * semantics as the other providers.
+ */
+export function registerMapRenderCountProvider(
+	provider: RenderCountProvider,
+): () => void {
+	renderCountProvider = provider;
+	return () => {
+		if (renderCountProvider === provider) renderCountProvider = null;
+	};
+}
+
 const EMPTY_PICK_STATE: MapPickStateSnapshot = {
 	active: false,
 	sourcePlanetNumber: null,
@@ -191,6 +210,13 @@ export function getMapMode(): WrapMode | null {
 	return modeProvider?.() ?? null;
 }
 
+/** Pulls the renderer's painted-frame count. Returns `null` when no
+ * map view is mounted. Stays constant on idle frames (render-on-demand)
+ * and advances only on camera moves or content mutations. */
+export function getMapRenderCount(): number | null {
+	return renderCountProvider?.() ?? null;
+}
+
 interface RendererDebugWindow {
 	__galaxyDebug?: {
 		getMapPrimitives?: () => readonly MapPrimitiveSnapshot[];
@@ -198,6 +224,7 @@ interface RendererDebugWindow {
 		getMapCamera?: () => MapCameraSnapshot | null;
 		getMapFog?: () => MapFogSnapshot;
 		getMapMode?: () => WrapMode | null;
+		getMapRenderCount?: () => number | null;
 		[key: string]: unknown;
 	};
 }
@@ -222,6 +249,7 @@ export function installRendererDebugSurface(): () => void {
 		getMapCamera,
 		getMapFog,
 		getMapMode,
+		getMapRenderCount,
 	};
 	win.__galaxyDebug = surface;
 	return (): void => {
@@ -245,5 +273,8 @@ export function installRendererDebugSurface(): () => void {
 		if (current.getMapMode === getMapMode) {
 			delete current.getMapMode;
 		}
+		if (current.getMapRenderCount === getMapRenderCount) {
+			delete current.getMapRenderCount;
+		}
 	};
 }
diff --git a/ui/frontend/src/map/render.ts b/ui/frontend/src/map/render.ts
index 5320ad8..efe6b0d 100644
--- a/ui/frontend/src/map/render.ts
+++ b/ui/frontend/src/map/render.ts
@@ -17,7 +17,15 @@
 // Hit-test is owned by ./hit-test.ts; this file only exposes the
 // current camera and viewport so callers can run hits.
 
-import { Application, Container, Graphics, type Renderer, type RendererType } from "pixi.js";
+import {
+	Application,
+	Container,
+	Graphics,
+	Ticker,
+	UPDATE_PRIORITY,
+	type Renderer,
+	type RendererType,
+} from "pixi.js";
 import { Viewport as PixiViewport } from "pixi-viewport";
 
 import { hitTest, type Hit } from "./hit-test";
@@ -66,6 +74,15 @@ export interface RendererHandle {
 	getCamera(): Camera;
 	getViewport(): Viewport;
 	getBackend(): "webgl" | "webgpu" | "canvas";
+	/**
+	 * getRenderCount returns how many frames the renderer has actually
+	 * painted since creation. The renderer runs render-on-demand (the
+	 * Pixi auto-render loop is stopped), so this counter only advances
+	 * when the camera moved or a content mutation requested a repaint —
+	 * never on idle frames. Exposed for the debug surface so e2e specs
+	 * can assert that an idle map does not keep repainting.
+	 */
+	getRenderCount(): number;
 	hitAt(cursorPx: { x: number; y: number }): Hit | null;
 	/**
 	 * setExtraPrimitives replaces the current overlay primitive layer
@@ -329,6 +346,12 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 		autoDensity: true,
 		resolution,
 	});
+	// Render-on-demand: stop Pixi's continuous auto-render loop. Frames
+	// are painted explicitly by `renderFlush` below, only when the
+	// camera moved or a content mutation requested a repaint. This is
+	// what stops the heavy visibility-fog overlay from re-rasterising
+	// every frame and freezing the whole UI on large reports.
+	app.stop();
 
 	const viewport = new PixiViewport({
 		screenWidth: widthPx,
@@ -337,7 +360,35 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 		worldHeight: opts.world.height,
 		events: app.renderer.events,
 	});
-	viewport.drag().wheel({ smooth: 5 }).pinch().decelerate();
+	// No `.decelerate()`: panning stops the instant the drag is
+	// released instead of coasting. Besides matching the requested feel,
+	// it means the viewport stops mutating its transform as soon as the
+	// pointer is up, so render-on-demand goes idle immediately after a
+	// drag rather than repainting through an inertia tail.
+	viewport.drag().wheel({ smooth: 5 }).pinch();
+
+	// Render-on-demand wiring. `viewport.dirty` is maintained by
+	// pixi-viewport's own `Ticker.shared` update and flips true on any
+	// camera move (drag / wheel / pinch / programmatic `moveCenter` /
+	// the torus + no-wrap `moved` listeners). `contentDirty` is flipped
+	// by `requestRender` from every scene-graph mutation that does not
+	// move the camera (fog, hide-set, extras, wrap mode, resize, pick
+	// overlay). The flush runs at LOW priority so it observes the
+	// viewport's freshly updated `dirty` flag within the same shared
+	// tick. Plain hover mutates no Graphics, so it never repaints.
+	let contentDirty = true; // force the first paint after mount
+	let renderCount = 0;
+	const requestRender = (): void => {
+		contentDirty = true;
+	};
+	const renderFlush = (): void => {
+		if (!viewport.dirty && !contentDirty) return;
+		app.render();
+		viewport.dirty = false;
+		contentDirty = false;
+		renderCount++;
+	};
+	Ticker.shared.add(renderFlush, undefined, UPDATE_PRIORITY.LOW);
 
 	app.stage.addChild(viewport);
 
@@ -484,6 +535,10 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 			viewport.on("moved", wrapTorusCamera);
 			wrapTorusCamera();
 		}
+		// Toggling `copy.visible` does not move the camera, so request a
+		// repaint explicitly; any camera change above also sets
+		// `viewport.dirty`, which is harmless to request twice.
+		requestRender();
 	};
 
 	applyMode(mode);
@@ -621,6 +676,7 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 				width: PICK_OVERLAY_STYLE.hover.width,
 			});
 		}
+		requestRender();
 	};
 	const teardownPickMode = (): void => {
 		if (!pickModeActive) return;
@@ -636,6 +692,9 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 			pickOverlay = null;
 		}
 		pickOptions = null;
+		// Un-dimming primitives and removing the overlay are scene
+		// changes that do not move the camera.
+		requestRender();
 	};
 	const openPickMode = (options: PickModeOptions): PickModeHandle => {
 		// An existing session is cancelled first so the previous
@@ -711,6 +770,7 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 			heightPx: viewport.screenHeight,
 		}),
 		getBackend: () => rendererBackendName(app.renderer),
+		getRenderCount: () => renderCount,
 		hitAt: (cursorPx) =>
 			hitTest(
 				currentWorld,
@@ -748,6 +808,7 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 				...opts.world.primitives,
 				...prims,
 			]);
+			requestRender();
 		},
 		getPrimitives: () => currentWorld.primitives,
 		onClick: (cb) => {
@@ -803,6 +864,7 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 			for (const [id, list] of primitiveGraphics) {
 				applyHiddenStateTo(id, list);
 			}
+			requestRender();
 		},
 		isPrimitiveHidden: (id) => hiddenIds.has(id),
 		setVisibilityFog: (circles) => {
@@ -813,6 +875,9 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 			for (const old of fogLayer.removeChildren()) {
 				old.destroy({ children: true });
 			}
+			// Repaint whether or not new fog is added: clearing the layer
+			// (toggling the fog off) is itself a scene change.
+			requestRender();
 			const ops = fogPaintOps(
 				opts.world,
 				circles,
@@ -848,8 +913,13 @@ export async function createRenderer(opts: RendererOptions): Promise<RendererHan
 			if (mode === "no-wrap") {
 				enforceCentreWhenLarger();
 			}
+			// The drawing buffer was resized; repaint at the new size.
+			requestRender();
 		},
 		dispose: () => {
+			// Detach the render-on-demand flush first so nothing tries
+			// to paint a half-destroyed scene on the next shared tick.
+			Ticker.shared.remove(renderFlush);
 			// Tear down any open pick session before destroying the
 			// app — the resolution callback might reference Svelte
 			// stores that disappear next tick on dispose, but
diff --git a/ui/frontend/tests/e2e/map-toggles.spec.ts b/ui/frontend/tests/e2e/map-toggles.spec.ts
index c4ea0f3..cf88cc2 100644
--- a/ui/frontend/tests/e2e/map-toggles.spec.ts
+++ b/ui/frontend/tests/e2e/map-toggles.spec.ts
@@ -11,6 +11,10 @@
 //   * `getMapFog()` — the current visibility-fog circle list.
 //   * `getMapCamera()` — the wrap-mode test reads the centre before
 //     and after the flip to confirm camera preservation.
+//   * `getMapRenderCount()` — painted-frame counter used by the
+//     render-on-demand specs at the bottom of this file: an idle map
+//     must not keep repainting, and a released drag must not coast
+//     (the `decelerate` plugin was removed).
 
 import { fromJson, type JsonValue } from "@bufbuild/protobuf";
 import { expect, test, type Page } from "@playwright/test";
@@ -400,3 +404,105 @@ test("toggle state persists across a page reload", async ({ page }) => {
 	expect(await visibleHighBitCount(page, 0xa0000000)).toBe(0);
 	expect(await visibleHighBitCount(page, 0xc0000000)).toBe(0);
 });
+
+// settledRenderCount waits out the mount/resize paint burst and returns
+// the painted-frame count once it stops advancing. The renderer runs
+// render-on-demand, so the count goes flat as soon as the scene is
+// static; the loop bails after a fixed number of samples so a renderer
+// that never settles fails the spec instead of hanging.
+async function settledRenderCount(page: Page): Promise<number> {
+	await page.waitForFunction(
+		() => (window.__galaxyDebug?.getMapRenderCount?.() ?? 0) > 0,
+	);
+	return await page.evaluate(async () => {
+		const read = (): number =>
+			window.__galaxyDebug!.getMapRenderCount!() ?? 0;
+		let prev = read();
+		for (let i = 0; i < 20; i++) {
+			await new Promise((r) => setTimeout(r, 150));
+			const cur = read();
+			if (cur === prev) return cur;
+			prev = cur;
+		}
+		return prev;
+	});
+}
+
+test("render-on-demand: an idle map does not repaint, a content mutation does", async ({
+	page,
+}) => {
+	await mockGateway(page, { currentTurn: 1 });
+	await bootSession(page);
+	await openGame(page);
+
+	const settled = await settledRenderCount(page);
+
+	// Idle window: no pointer interaction, no toggle. A continuous
+	// auto-render loop would add ~40 frames over 700ms at 60fps; render
+	// -on-demand adds none. The +2 slack tolerates a lone stray frame
+	// (e.g. a late layout settle) while still failing hard if the
+	// always-on loop ever comes back.
+	await page.waitForTimeout(700);
+	const afterIdle = await page.evaluate(
+		() => window.__galaxyDebug!.getMapRenderCount!(),
+	);
+	expect(afterIdle).toBeLessThanOrEqual(settled + 2);
+
+	// Toggling the fog mutates the scene graph and must repaint.
+	await page.getByTestId("map-toggles-trigger").click();
+	await page.getByTestId("map-toggles-visible-hyperspace").click();
+	await page.waitForFunction(
+		() => window.__galaxyDebug!.getMapFog!().circles.length === 0,
+	);
+	// The repaint lands on the next shared-ticker frame after the fog
+	// input changed, so poll for the counter to advance rather than
+	// reading it synchronously (the timing of that frame is racy).
+	await page.waitForFunction(
+		(baseline) => window.__galaxyDebug!.getMapRenderCount!() > baseline,
+		afterIdle,
+	);
+});
+
+test("pan stops immediately on release: no inertia tail after a drag", async ({
+	page,
+}) => {
+	await mockGateway(page, { currentTurn: 1 });
+	await bootSession(page);
+	await openGame(page);
+
+	await settledRenderCount(page);
+
+	const canvas = page.getByTestId("active-view-map").locator("canvas");
+	const box = await canvas.boundingBox();
+	expect(box).not.toBeNull();
+	if (box === null) return;
+	const cx = box.x + box.width / 2;
+	const cy = box.y + box.height / 2;
+
+	// Decisive drag with intermediate steps so pixi-viewport's drag
+	// plugin clears its movement threshold.
+	await page.mouse.move(cx, cy);
+	await page.mouse.down();
+	for (let step = 1; step <= 16; step++) {
+		await page.mouse.move(cx - (160 * step) / 16, cy - (120 * step) / 16);
+	}
+	await page.mouse.up();
+
+	// Let the final drag frame flush, then snapshot the camera centre
+	// and confirm it does not drift over the next ~500ms. Without the
+	// `decelerate` plugin the viewport freezes the instant the drag
+	// ends, so the centre is identical; a re-introduced inertia tail
+	// would coast it by many world units. (If the synthetic drag never
+	// registered the centre is also static, so the spec never
+	// false-fails — it only catches a returning inertia tail.)
+	await page.waitForTimeout(120);
+	const atRelease = await page.evaluate(
+		() => window.__galaxyDebug!.getMapCamera!()!.camera,
+	);
+	await page.waitForTimeout(500);
+	const later = await page.evaluate(
+		() => window.__galaxyDebug!.getMapCamera!()!.camera,
+	);
+	expect(Math.abs(later.centerX - atRelease.centerX)).toBeLessThan(1);
+	expect(Math.abs(later.centerY - atRelease.centerY)).toBeLessThan(1);
+});
diff --git a/ui/frontend/tests/e2e/storage-keypair-persistence.spec.ts b/ui/frontend/tests/e2e/storage-keypair-persistence.spec.ts
index e7fce43..b835897 100644
--- a/ui/frontend/tests/e2e/storage-keypair-persistence.spec.ts
+++ b/ui/frontend/tests/e2e/storage-keypair-persistence.spec.ts
@@ -50,6 +50,7 @@ interface DebugSurface {
 	getMapCamera(): MapCameraSnapshot | null;
 	getMapFog(): MapFogSnapshot;
 	getMapMode(): WrapMode | null;
+	getMapRenderCount(): number;
 }
 
 declare global {