diff --git a/apps/desktop/e2e/white-theme.spec.ts b/apps/desktop/e2e/white-theme.spec.ts
new file mode 100644
index 0000000..4a67bee
--- /dev/null
+++ b/apps/desktop/e2e/white-theme.spec.ts
@@ -0,0 +1,28 @@
+import { expect, test } from "@playwright/test";
+
+test("white canvas, sidebar and panels survive system dark mode", async ({ page }, testInfo) => {
+  await page.emulateMedia({ colorScheme: "dark" });
+  for (const view of ["today", "chats", "teams", "automations", "apps", "providers", "tokens", "settings"]) {
+    await page.goto(`/?state=active&view=${view}`);
+    const surfaces = await page.evaluate(() => ["canvas", "sidebar", "surface", "surface-strong"].map((token) =>
+      getComputedStyle(document.documentElement).getPropertyValue(`--${token}`).trim()));
+    expect(surfaces).toEqual(["#ffffff", "#ffffff", "#ffffff", "#ffffff"]);
+    for (const selector of ["html", "body", ".app-shell", ".sidebar", ".topbar"]) {
+      await expect(page.locator(selector)).toHaveCSS("background-color", "rgb(255, 255, 255)");
+    }
+    if (view === "tokens") await expect(page.locator(".token-query")).toHaveCSS("background-color", "rgb(255, 255, 255)");
+    expect(await page.evaluate(() => document.documentElement.scrollWidth > document.documentElement.clientWidth)).toBe(false);
+  }
+  await page.goto("/?state=active&view=today");
+  await page.screenshot({ path: testInfo.outputPath("desktop-white-today.png"), fullPage: true });
+});
+
+test("sign-in and access-gated pages use the same white background", async ({ page }, testInfo) => {
+  for (const state of ["signed_out", "inactive", "unknown"]) {
+    await page.goto(`/?state=${state}`);
+    const selectors = state === "signed_out" ? [".access-layout", ".access-story", ".access-panel"] : [".locked-layout"];
+    for (const selector of selectors) await expect(page.locator(selector)).toHaveCSS("background-color", "rgb(255, 255, 255)");
+  }
+  await page.goto("/?state=signed_out");
+  await page.screenshot({ path: testInfo.outputPath("desktop-white-login.png"), fullPage: true });
+});
diff --git a/apps/desktop/src-tauri/tauri.conf.json b/apps/desktop/src-tauri/tauri.conf.json
index a67c0a3..b71baaf 100644
--- a/apps/desktop/src-tauri/tauri.conf.json
+++ b/apps/desktop/src-tauri/tauri.conf.json
@@ -14,6 +14,8 @@
       {
         "label": "main",
         "title": "Simplicio",
+        "theme": "Light",
+        "backgroundColor": "#ffffff",
         "width": 1280,
         "height": 820,
         "minWidth": 860,
diff --git a/apps/desktop/src/design_system.test.ts b/apps/desktop/src/design_system.test.ts
index baabf12..fd3a03c 100644
--- a/apps/desktop/src/design_system.test.ts
+++ b/apps/desktop/src/design_system.test.ts
@@ -1,8 +1,17 @@
 import { describe, expect, it } from "vitest";
+import rawConfig from "../src-tauri/tauri.conf.json?raw";
 import { copy, locale, t } from "./i18n";
 import { designTokens } from "./design_tokens";
 
 describe("desktop design system", () => {
+  it("keeps white surfaces consistent in shared tokens and the native window", () => {
+    const config = JSON.parse(rawConfig);
+    expect(designTokens.color.canvas).toBe("#ffffff");
+    expect(designTokens.color.surface).toBe("#ffffff");
+    expect(config.app.windows[0].backgroundColor).toBe("#ffffff");
+    expect(config.app.windows[0].theme).toBe("Light");
+  });
+
   it("keeps the initial locale and UI copy separate from Runtime data", () => {
     expect(locale).toBe("pt-BR");
     expect(t("nav.settings")).toBe("Configurações");
diff --git a/apps/desktop/src/design_tokens.ts b/apps/desktop/src/design_tokens.ts
index ee52656..f82d565 100644
--- a/apps/desktop/src/design_tokens.ts
+++ b/apps/desktop/src/design_tokens.ts
@@ -2,8 +2,8 @@ export const designTokens = {
   color: {
     ink: "#25261f",
     muted: "#777567",
-    canvas: "#f3edda",
-    surface: "#faf7ea",
+    canvas: "#ffffff",
+    surface: "#ffffff",
     green: "#54a879",
     greenDark: "#2f704e",
     warning: "#bb7b34",
diff --git a/apps/desktop/src/styles.css b/apps/desktop/src/styles.css
index 333787d..bf68b83 100644
--- a/apps/desktop/src/styles.css
+++ b/apps/desktop/src/styles.css
@@ -1,7 +1,7 @@
 :root {
   font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
   color: #25261f;
-  background: #f3edda;
+  background: #ffffff;
   font-synthesis: none;
   text-rendering: optimizeLegibility;
   --ink: #25261f;
@@ -13,13 +13,13 @@
   --green-pale: #eef5e9;
   --yellow: #e7c66a;
   --yellow-soft: #f6e9bd;
-  --canvas: #f3edda;
-  --sidebar: #ece4cc;
-  --surface: #faf7ea;
-  --surface-strong: #fffdf6;
-  --surface-muted: #f0ead7;
-  --line: #d8d0b9;
-  --line-soft: rgba(117, 108, 79, 0.14);
+  --canvas: #ffffff;
+  --sidebar: #ffffff;
+  --surface: #ffffff;
+  --surface-strong: #ffffff;
+  --surface-muted: #f5f6f7;
+  --line: #dfe3e6;
+  --line-soft: rgba(37, 38, 31, 0.12);
   --warning: #bb7b34;
   --danger: #bd665d;
   --mono: "SFMono-Regular", "IBM Plex Mono", Consolas, monospace;
@@ -163,11 +163,11 @@ p { margin-top: 0; }
 .button-secondary {
   color: #4f5148;
   border-color: var(--line);
-  background: rgba(255, 253, 246, 0.68);
+  background: var(--surface);
 }
 
 .button-secondary:hover {
-  border-color: #bdb49b;
+  border-color: #b9c1c7;
   background: var(--surface-strong);
 }
 
@@ -255,7 +255,7 @@ p { margin-top: 0; }
 
 .nav-item:hover {
   color: #41433b;
-  background: rgba(255, 253, 246, 0.48);
+  background: var(--surface-muted);
 }
 
 .nav-item.active {
@@ -281,9 +281,9 @@ p { margin-top: 0; }
 .sidebar-runtime {
   margin-top: auto;
   padding: 11px;
-  border: 1px solid #d3cab1;
+  border: 1px solid var(--line);
   border-radius: 10px;
-  background: rgba(255, 253, 246, 0.52);
+  background: var(--surface);
 }
 
 .runtime-row {
@@ -338,7 +338,7 @@ p { margin-top: 0; }
   grid-template-columns: 1fr auto 1fr;
   align-items: center;
   gap: 16px;
-  background: rgba(250, 247, 234, 0.82);
+  background: var(--surface);
   backdrop-filter: blur(14px);
 }
 
@@ -814,7 +814,7 @@ p { margin-top: 0; }
   display: flex;
   align-items: center;
   gap: 18px;
-  background: rgba(250, 247, 234, 0.72);
+  background: var(--surface);
 }
 
 .provider-summary > div {
@@ -854,7 +854,7 @@ p { margin-top: 0; }
   border: 1px solid var(--line);
   border-radius: 9px;
   display: inline-flex;
-  background: rgba(236, 228, 204, 0.56);
+  background: var(--surface-muted);
 }
 
 .segmented-control button {
@@ -1007,13 +1007,13 @@ p { margin-top: 0; }
   min-width: 0;
   margin-top: 10px;
   padding: 13px 15px;
-  border: 1px solid #d3cbb3;
+  border: 1px solid var(--line);
   border-radius: 11px;
   display: grid;
   grid-template-columns: auto minmax(0, 1fr) auto;
   align-items: center;
   gap: 13px;
-  background: #eee7d1;
+  background: var(--surface-muted);
 }
 
 .principle-icon {
@@ -1149,7 +1149,7 @@ p { margin-top: 0; }
   border-radius: 20px 0 0 20px;
   display: flex;
   flex-direction: column;
-  background: var(--yellow-soft);
+  background: var(--surface);
 }
 
 .access-story > .brand { margin-bottom: 40px; }
@@ -1183,7 +1183,7 @@ p { margin-top: 0; }
   display: inline-flex;
   align-items: center;
   gap: 6px;
-  background: rgba(255, 253, 246, 0.42);
+  background: var(--surface-muted);
 }
 
 .access-proof-grid article > span { color: var(--green-dark); font-size: 10px; }
diff --git a/docs/desktop/DESIGN.md b/docs/desktop/DESIGN.md
index ff405bb..f75753e 100644
--- a/docs/desktop/DESIGN.md
+++ b/docs/desktop/DESIGN.md
@@ -1,10 +1,16 @@
 # Desktop design system and accessibility baseline
 
-The Desktop uses a small, light-native visual system: butter canvas, ivory
+The Desktop uses a small, light-native visual system: white canvas, sidebar and
 surfaces, near-black text, soft green for healthy/action states, and amber only
 for attention. CSS custom properties in `src/styles.css` are the source of
 truth for color, spacing, radius, focus, motion, and target-size tokens.
 
+The native window also starts with a white background and the light theme, so
+startup, login and workspace surfaces remain consistent when the operating
+system prefers dark mode. Neutral secondary surfaces use a light gray; color
+accents communicate status and actions rather than tinting the application
+background. Browser theme tests do not certify an installed platform package.
+
 The initial locale is `pt-BR`. `src/i18n.ts` contains UI copy keys only;
 Runtime strings and provider IDs remain data and are never used as translation
 keys.