diff --git a/AgentCompany-New/src/renderer/src/pages/OfficePage.tsx b/AgentCompany-New/src/renderer/src/pages/OfficePage.tsx
index 6fca585c..2013c35c 100644
--- a/AgentCompany-New/src/renderer/src/pages/OfficePage.tsx
+++ b/AgentCompany-New/src/renderer/src/pages/OfficePage.tsx
@@ -144,7 +144,7 @@ export function OfficePage({ snapshot }: PageProps) {
           carrying: null,
         });
       }
-      renderOffice(ctx, viewW, viewH, sim.plan, camera, people, now);
+      renderOffice(ctx, viewW, viewH, sim.plan, camera, people, now, new Date());
     };
 
     raf = requestAnimationFrame(tick);
diff --git a/AgentCompany-New/src/renderer/src/pages/office/office-renderer.ts b/AgentCompany-New/src/renderer/src/pages/office/office-renderer.ts
index 205477dd..aeff8346 100644
--- a/AgentCompany-New/src/renderer/src/pages/office/office-renderer.ts
+++ b/AgentCompany-New/src/renderer/src/pages/office/office-renderer.ts
@@ -1,5 +1,6 @@
 import type { AgentActivity, Camera, FloorPlan, Rect } from "./office-types";
 import { deskScreenRect, drawWorld } from "./scene-renderer";
+import { skyScene } from "./sky";
 import { drawPerson, type Carrying, type Facing, type SpriteAppearance } from "./sprites";
 
 export interface RenderPerson {
@@ -42,13 +43,14 @@ export function renderOffice(
   camera: Camera,
   people: RenderPerson[],
   timeMs: number,
+  clock: Date,
 ): void {
   ctx.fillStyle = "#14161c";
   ctx.fillRect(0, 0, viewW, viewH);
   ctx.save();
   ctx.translate(-camera.x, -camera.y);
 
-  drawWorld(ctx, plan, { x: camera.x, y: camera.y, w: viewW, h: viewH });
+  drawWorld(ctx, plan, { x: camera.x, y: camera.y, w: viewW, h: viewH }, skyScene(clock));
 
   for (const person of people) {
     if (!person.desk) continue;
diff --git a/AgentCompany-New/src/renderer/src/pages/office/scene-renderer.ts b/AgentCompany-New/src/renderer/src/pages/office/scene-renderer.ts
index 06d1b9d2..c9f1f7a1 100644
--- a/AgentCompany-New/src/renderer/src/pages/office/scene-renderer.ts
+++ b/AgentCompany-New/src/renderer/src/pages/office/scene-renderer.ts
@@ -1,5 +1,6 @@
 import type { FloorPlan, Rect, RoomSpec } from "./office-types";
 import { WALL } from "./floor-plan";
+import { drawWindowSky, type SkyScene } from "./sky";
 
 /**
  * Draws the static office world in a 3/4 top-down pixel style: wood floor,
@@ -34,17 +35,15 @@ const PALETTE = {
   monitorShell: "#4b5058",
   chair: "#3d4148",
   chairDark: "#33373d",
-  glassSky: "#8fc3e8",
-  glassSkyLow: "#c3e0f2",
   frame: "#3f3831",
   signPlate: "#2f2a25",
   signText: "#d8cfc2",
 } as const;
 
-export function drawWorld(ctx: CanvasRenderingContext2D, plan: FloorPlan, view: Rect): void {
+export function drawWorld(ctx: CanvasRenderingContext2D, plan: FloorPlan, view: Rect, sky: SkyScene): void {
   drawFloor(ctx, plan, view);
   for (const room of plan.rooms) drawRoomFloor(ctx, room);
-  drawStructure(ctx, plan);
+  drawStructure(ctx, plan, sky);
   for (const room of plan.rooms) drawRoomFurniture(ctx, plan, room);
   drawCorridorPlants(ctx, plan);
   for (const desk of plan.desks) {
@@ -96,7 +95,7 @@ function drawRoomFloor(ctx: CanvasRenderingContext2D, room: RoomSpec): void {
   }
 }
 
-function drawStructure(ctx: CanvasRenderingContext2D, plan: FloorPlan): void {
+function drawStructure(ctx: CanvasRenderingContext2D, plan: FloorPlan, sky: SkyScene): void {
   const { w, h } = plan.world;
   ctx.fillStyle = PALETTE.wallFill;
   ctx.fillRect(0, 0, w, WALL);
@@ -113,7 +112,7 @@ function drawStructure(ctx: CanvasRenderingContext2D, plan: FloorPlan): void {
     ctx.fillRect(b.x, b.y + WALL_FACE_H - 6, b.w, 6);
     ctx.fillStyle = PALETTE.baseboard;
     ctx.fillRect(b.x, b.y + WALL_FACE_H, b.w, 2);
-    drawRoomWindows(ctx, room);
+    drawRoomWindows(ctx, room, sky);
   }
 
   ctx.fillStyle = PALETTE.wallFill;
@@ -141,8 +140,11 @@ function drawSouthWall(ctx: CanvasRenderingContext2D, room: RoomSpec): void {
   ctx.fillRect(gapR, y, 3, WALL);
 }
 
-function drawRoomWindows(ctx: CanvasRenderingContext2D, room: RoomSpec): void {
-  for (const rect of windowRects(room)) drawWindowFrame(ctx, rect);
+function drawRoomWindows(ctx: CanvasRenderingContext2D, room: RoomSpec, sky: SkyScene): void {
+  const rects = windowRects(room);
+  for (let i = 0; i < rects.length; i++) {
+    drawWindowFrame(ctx, rects[i], sky, Math.round(room.bounds.x) + i * 53);
+  }
 }
 
 /** Window glass rects on each room's north wall face (world coordinates). */
@@ -163,14 +165,10 @@ export function windowRects(room: RoomSpec): Rect[] {
   ];
 }
 
-function drawWindowFrame(ctx: CanvasRenderingContext2D, rect: Rect): void {
+function drawWindowFrame(ctx: CanvasRenderingContext2D, rect: Rect, sky: SkyScene, seed: number): void {
   ctx.fillStyle = PALETTE.frame;
   ctx.fillRect(rect.x - 3, rect.y - 3, rect.w + 6, rect.h + 6);
-  const grad = ctx.createLinearGradient(0, rect.y, 0, rect.y + rect.h);
-  grad.addColorStop(0, PALETTE.glassSky);
-  grad.addColorStop(1, PALETTE.glassSkyLow);
-  ctx.fillStyle = grad;
-  ctx.fillRect(rect.x, rect.y, rect.w, rect.h);
+  drawWindowSky(ctx, rect, sky, seed);
   ctx.fillStyle = PALETTE.frame;
   ctx.fillRect(rect.x + rect.w / 2 - 1, rect.y, 2, rect.h);
 }
diff --git a/AgentCompany-New/src/renderer/src/pages/office/sky.ts b/AgentCompany-New/src/renderer/src/pages/office/sky.ts
new file mode 100644
index 00000000..9d7e3e9e
--- /dev/null
+++ b/AgentCompany-New/src/renderer/src/pages/office/sky.ts
@@ -0,0 +1,176 @@
+import type { Rect } from "./office-types";
+
+/**
+ * The world outside the office windows, driven by real local time: night
+ * with stars and a moon, a warm sunrise, blue day, and an orange sunset,
+ * over a city skyline whose windows light up after dark. All color math is
+ * pure so the phase timeline is unit-testable.
+ */
+
+export type SkyPhaseKey = "night" | "dawn" | "day" | "dusk";
+
+export interface SkyScene {
+  phase: SkyPhaseKey;
+  top: Rgb;
+  bottom: Rgb;
+  /** Sun position in unit space, null when below the horizon. */
+  sun: { x: number; elevation: number } | null;
+  /** Moon position in unit space, null during daylight. */
+  moon: { x: number; elevation: number } | null;
+  /** 0 (invisible) to 1 (full night sky). */
+  starIntensity: number;
+  /** City windows glow from dusk through dawn. */
+  cityLights: boolean;
+}
+
+export interface Rgb {
+  r: number;
+  g: number;
+  b: number;
+}
+
+interface SkyPalette {
+  top: Rgb;
+  bottom: Rgb;
+}
+
+const NIGHT: SkyPalette = { top: rgb(11, 16, 38), bottom: rgb(30, 41, 73) };
+const DAWN: SkyPalette = { top: rgb(84, 100, 150), bottom: rgb(242, 160, 107) };
+const DAY: SkyPalette = { top: rgb(96, 166, 222), bottom: rgb(199, 228, 245) };
+const DUSK: SkyPalette = { top: rgb(74, 66, 110), bottom: rgb(232, 118, 79) };
+
+/** (hour, palette) anchors across a day; linearly interpolated between. */
+const TIMELINE: Array<[number, SkyPalette]> = [
+  [0, NIGHT],
+  [5.5, NIGHT],
+  [6.5, DAWN],
+  [7.5, DAY],
+  [17.5, DAY],
+  [18.5, DUSK],
+  [19.5, NIGHT],
+  [24, NIGHT],
+];
+
+const SUNRISE_H = 6;
+const SUNSET_H = 19;
+
+export function phaseAt(date: Date): SkyPhaseKey {
+  const hour = date.getHours() + date.getMinutes() / 60;
+  if (hour < 5.5 || hour >= 19.5) return "night";
+  if (hour < 7.5) return "dawn";
+  if (hour < 17.5) return "day";
+  return "dusk";
+}
+
+export function skyScene(date: Date): SkyScene {
+  const hour = date.getHours() + date.getMinutes() / 60 + date.getSeconds() / 3600;
+  const palette = paletteAt(hour);
+  const dayProgress = (hour - SUNRISE_H) / (SUNSET_H - SUNRISE_H);
+  const sunUp = dayProgress > 0 && dayProgress < 1;
+  const nightProgress = hour >= SUNSET_H ? (hour - SUNSET_H) / (24 - SUNSET_H + SUNRISE_H) : (hour + 24 - SUNSET_H) / (24 - SUNSET_H + SUNRISE_H);
+  const starIntensity = clamp01(hour < 12 ? (5.75 - hour) / 0.75 : (hour - 19.25) / 0.75);
+  return {
+    phase: phaseAt(date),
+    top: palette.top,
+    bottom: palette.bottom,
+    sun: sunUp ? { x: dayProgress, elevation: Math.sin(dayProgress * Math.PI) } : null,
+    moon: sunUp ? null : { x: nightProgress, elevation: Math.sin(nightProgress * Math.PI) * 0.9 + 0.05 },
+    starIntensity,
+    cityLights: !sunUp || Math.sin(dayProgress * Math.PI) < 0.12,
+  };
+}
+
+function paletteAt(hour: number): SkyPalette {
+  for (let i = 0; i + 1 < TIMELINE.length; i++) {
+    const [fromHour, fromPalette] = TIMELINE[i];
+    const [toHour, toPalette] = TIMELINE[i + 1];
+    if (hour >= fromHour && hour <= toHour) {
+      const t = toHour === fromHour ? 0 : (hour - fromHour) / (toHour - fromHour);
+      return {
+        top: lerpRgb(fromPalette.top, toPalette.top, t),
+        bottom: lerpRgb(fromPalette.bottom, toPalette.bottom, t),
+      };
+    }
+  }
+  return NIGHT;
+}
+
+export function drawWindowSky(ctx: CanvasRenderingContext2D, glass: Rect, scene: SkyScene, seed: number): void {
+  const gradient = ctx.createLinearGradient(0, glass.y, 0, glass.y + glass.h);
+  gradient.addColorStop(0, css(scene.top));
+  gradient.addColorStop(1, css(scene.bottom));
+  ctx.fillStyle = gradient;
+  ctx.fillRect(glass.x, glass.y, glass.w, glass.h);
+
+  if (scene.starIntensity > 0) {
+    ctx.fillStyle = `rgba(238,240,255,${0.85 * scene.starIntensity})`;
+    for (let i = 0; i < Math.floor(glass.w / 5); i++) {
+      const sx = glass.x + ((seed * 61 + i * 137) % glass.w);
+      const sy = glass.y + ((seed * 43 + i * 89) % Math.max(1, glass.h - 14));
+      ctx.fillRect(sx, sy, 1, 1);
+    }
+  }
+
+  if (scene.sun) {
+    const sx = glass.x + 4 + scene.sun.x * (glass.w - 8);
+    const sy = glass.y + 4 + (1 - scene.sun.elevation) * (glass.h - 16);
+    ctx.fillStyle = "rgba(255,214,120,0.35)";
+    ctx.fillRect(sx - 4, sy - 4, 9, 9);
+    ctx.fillStyle = "#ffd66e";
+    ctx.fillRect(sx - 2, sy - 2, 5, 5);
+  } else if (scene.moon) {
+    const mx = glass.x + 4 + scene.moon.x * (glass.w - 8);
+    const my = glass.y + 4 + (1 - scene.moon.elevation) * (glass.h - 16);
+    ctx.fillStyle = "#e8ecf5";
+    ctx.fillRect(mx - 2, my - 2, 5, 5);
+    ctx.fillStyle = "#c3cad9";
+    ctx.fillRect(mx, my - 1, 2, 2);
+  }
+
+  drawSkyline(ctx, glass, scene, seed);
+}
+
+function drawSkyline(ctx: CanvasRenderingContext2D, glass: Rect, scene: SkyScene, seed: number): void {
+  const silhouette = scene.phase === "day" ? rgb(122, 148, 178) : lerpRgb(rgb(26, 30, 48), scene.bottom, 0.25);
+  const baseline = glass.y + glass.h;
+  let x = glass.x;
+  let column = 0;
+  while (x < glass.x + glass.w) {
+    const key = seed * 31 + column * 97;
+    const width = 8 + (key % 8);
+    const height = 8 + ((key >> 2) % Math.max(4, glass.h - 18));
+    const w = Math.min(width, glass.x + glass.w - x);
+    ctx.fillStyle = css(silhouette);
+    ctx.fillRect(x, baseline - height, w, height);
+    if (scene.cityLights) {
+      ctx.fillStyle = "rgba(255,224,130,0.9)";
+      for (let wx = 1; wx + 2 < w; wx += 3) {
+        for (let wy = 2; wy + 2 < height; wy += 4) {
+          if (((key >> 3) + wx * 7 + wy * 13) % 4 === 0) ctx.fillRect(x + wx, baseline - height + wy, 1, 2);
+        }
+      }
+    }
+    x += w;
+    column += 1;
+  }
+}
+
+function rgb(r: number, g: number, b: number): Rgb {
+  return { r, g, b };
+}
+
+function lerpRgb(from: Rgb, to: Rgb, t: number): Rgb {
+  return {
+    r: Math.round(from.r + (to.r - from.r) * t),
+    g: Math.round(from.g + (to.g - from.g) * t),
+    b: Math.round(from.b + (to.b - from.b) * t),
+  };
+}
+
+function css(color: Rgb): string {
+  return `rgb(${color.r},${color.g},${color.b})`;
+}
+
+function clamp01(value: number): number {
+  return Math.min(1, Math.max(0, value));
+}
diff --git a/AgentCompany-New/tests/unit/office-sky.test.ts b/AgentCompany-New/tests/unit/office-sky.test.ts
new file mode 100644
index 00000000..830dcaa4
--- /dev/null
+++ b/AgentCompany-New/tests/unit/office-sky.test.ts
@@ -0,0 +1,53 @@
+import { describe, expect, test } from "vitest";
+import { phaseAt, skyScene } from "../../src/renderer/src/pages/office/sky";
+
+function at(hours: number, minutes: number): Date {
+  return new Date(2026, 6, 6, hours, minutes, 0);
+}
+
+describe("office window sky", () => {
+  test("maps local time to the four phases", () => {
+    expect(phaseAt(at(3, 0))).toBe("night");
+    expect(phaseAt(at(6, 30))).toBe("dawn");
+    expect(phaseAt(at(12, 0))).toBe("day");
+    expect(phaseAt(at(18, 30))).toBe("dusk");
+    expect(phaseAt(at(22, 0))).toBe("night");
+  });
+
+  test("the sun crosses the sky through the day and hands over to the moon", () => {
+    const morning = skyScene(at(8, 0));
+    const noon = skyScene(at(13, 0));
+    const evening = skyScene(at(18, 0));
+    const night = skyScene(at(23, 0));
+    expect(morning.sun).not.toBeNull();
+    expect(noon.sun!.elevation).toBeGreaterThan(morning.sun!.elevation);
+    expect(evening.sun!.x).toBeGreaterThan(morning.sun!.x);
+    expect(morning.moon).toBeNull();
+    expect(night.sun).toBeNull();
+    expect(night.moon).not.toBeNull();
+  });
+
+  test("stars and city lights belong to the night, not midday", () => {
+    const night = skyScene(at(1, 30));
+    const noon = skyScene(at(13, 0));
+    expect(night.starIntensity).toBe(1);
+    expect(night.cityLights).toBe(true);
+    expect(noon.starIntensity).toBe(0);
+    expect(noon.cityLights).toBe(false);
+  });
+
+  test("dawn blends smoothly instead of snapping palettes", () => {
+    const early = skyScene(at(5, 45));
+    const later = skyScene(at(6, 15));
+    expect(early.top).not.toEqual(later.top);
+    const delta = Math.abs(early.bottom.r - later.bottom.r);
+    expect(delta).toBeGreaterThan(0);
+    expect(delta).toBeLessThan(120);
+  });
+
+  test("sunrise and sunset windows glow with city lights while the sun is low", () => {
+    const sunrise = skyScene(at(6, 10));
+    expect(sunrise.sun).not.toBeNull();
+    expect(sunrise.cityLights).toBe(true);
+  });
+});