diff --git a/src/main/index.ts b/src/main/index.ts
index be581c9..d44aa0a 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -432,10 +432,13 @@ ipcMain.handle("folio:getClipboardText", () => {
 });
 
 // Theme preference. Stored as a plain string so future themes can be added
-// without touching the main process.
-ipcMain.handle("folio:getTheme", () => getSetting("theme", "default"));
+// without touching the main process. "default" from older builds maps to
+// "light" in the renderer, so it is normalized here too.
+ipcMain.handle("folio:getTheme", () => getSetting("theme", "light"));
 ipcMain.handle("folio:setTheme", (_e, id: unknown) => {
-  setSetting("theme", typeof id === "string" && id ? id : "default");
+  const theme =
+    typeof id === "string" && id && id !== "default" ? id : "light";
+  setSetting("theme", theme);
   return { ok: true };
 });
 
diff --git a/src/renderer/index.html b/src/renderer/index.html
index fe9137f..9fa1c80 100644
--- a/src/renderer/index.html
+++ b/src/renderer/index.html
@@ -30,7 +30,7 @@
           <div class="theme-control">
             <label class="theme-label" for="themeSelect">Theme</label>
             <select id="themeSelect" class="theme-select" title="Interface theme">
-              <option value="default">Default</option>
+              <option value="light">Light</option>
               <option value="neonflux">Neonflux</option>
             </select>
           </div>
diff --git a/src/renderer/theme.ts b/src/renderer/theme.ts
index e0afdd0..d1162e6 100644
--- a/src/renderer/theme.ts
+++ b/src/renderer/theme.ts
@@ -6,28 +6,37 @@ export interface ThemeApi {
   setTheme: (id: string) => Promise<unknown>;
 }
 
-function selector(): HTMLSelectElement {
+export function selector(): HTMLSelectElement {
   return document.getElementById("themeSelect") as HTMLSelectElement;
 }
 
+// Older builds stored the theme as "default"; that now maps to the Light
+// theme, which replaced it as Folio's default light appearance.
+const LIGHT = "light";
+
+function normalizeTheme(id: unknown): string {
+  if (typeof id !== "string" || !id || id === "default") return LIGHT;
+  return id;
+}
+
 export function applyTheme(id: string): void {
-  const theme = typeof id === "string" && id ? id : "default";
+  const theme = normalizeTheme(id);
   document.documentElement.setAttribute("data-theme", theme);
   const sel = selector();
   if (sel && sel.value !== theme) sel.value = theme;
 }
 
 export function currentTheme(): string {
-  return document.documentElement.getAttribute("data-theme") || "default";
+  return normalizeTheme(document.documentElement.getAttribute("data-theme"));
 }
 
 // Load the saved theme and wire the selector. Unknown stored values fall back
-// to Default (the :root base), so adding a theme later is safe for old saves.
+// to Light (the :root base), so adding a theme later is safe for old saves.
 export async function initTheme(api: ThemeApi): Promise<void> {
-  let saved = "default";
+  let saved = LIGHT;
   try {
     const value = await api.getTheme();
-    if (typeof value === "string" && value) saved = value;
+    if (typeof value === "string" && value) saved = normalizeTheme(value);
   } catch {
     // keep the default on any IPC failure
   }
diff --git a/src/renderer/themes.css b/src/renderer/themes.css
index a5528ac..e1499a2 100644
--- a/src/renderer/themes.css
+++ b/src/renderer/themes.css
@@ -4,9 +4,8 @@
    just a block of variable values — adding one means dropping a
    `:root[data-theme="..."]` block here plus an <option> in the theme selector.
 
-   Default mirrors Folio's original appearance: light, with an automatic dark
-   variant that follows the OS color scheme. Neonflux is a fixed dark,
-   futuristic theme. */
+   Light is Folio's default: a warm, writing-focused light scheme. Neonflux is
+   a fixed dark, futuristic theme. */
 
 /* ---- shared (non-color) tokens ---- */
 :root {
@@ -17,58 +16,35 @@
   --gap: 16px;
 }
 
-/* ---- Default (light) ---- */
+/* ---- Light (default) ----
+   A clean, professional writing theme. Warm off-white chrome keeps the app
+   soft instead of harsh, while a warm-white editor surface and charcoal text
+   stay comfortable for long-form reading. Borders and dividers are subtle
+   warm grays; the accent is a restrained deep teal-green so interactive and
+   selected elements stay clearly visible without shouting. */
 :root,
-:root[data-theme="default"] {
-  --color-bg: #ffffff;
-  --color-panel: #f7f7f8;
-  --color-border: #e2e2e7;
-  --color-text: #1a1a1d;
-  --color-muted: #6b6b76;
-  --color-accent: #2563eb;
-  --color-accent-hover: #1d4ed8;
+:root[data-theme="light"] {
+  --color-bg: #fffdf9;
+  --color-panel: #f5f1e9;
+  --color-border: #e4e0d5;
+  --color-text: #2b2925;
+  --color-muted: #7c786d;
+  --color-accent: #2f6b5f;
+  --color-accent-hover: #26584e;
 
   --color-on-accent: #ffffff;
-  --color-on-accent-soft: rgba(255, 255, 255, 0.15);
-  --color-on-accent-border: rgba(255, 255, 255, 0.3);
+  --color-on-accent-soft: rgba(255, 255, 255, 0.18);
+  --color-on-accent-border: rgba(255, 255, 255, 0.35);
 
-  --color-selection: rgba(37, 99, 235, 0.25);
-  --color-selection-strong: rgba(37, 99, 235, 0.5);
+  --color-selection: rgba(47, 107, 95, 0.22);
+  --color-selection-strong: rgba(47, 107, 95, 0.45);
 
-  --color-shadow: rgba(0, 0, 0, 0.25);
-  --color-shadow-strong: rgba(0, 0, 0, 0.3);
-  --color-backdrop: rgba(0, 0, 0, 0.45);
+  --color-shadow: rgba(45, 40, 32, 0.18);
+  --color-shadow-strong: rgba(45, 40, 32, 0.26);
+  --color-backdrop: rgba(45, 40, 32, 0.4);
 
-  --color-scrollbar: rgba(0, 0, 0, 0.18);
-  --color-scrollbar-hover: rgba(0, 0, 0, 0.32);
-}
-
-/* ---- Default (dark, follows OS preference) ---- */
-@media (prefers-color-scheme: dark) {
-  :root:not([data-theme]),
-  :root[data-theme="default"] {
-    --color-bg: #0f0f12;
-    --color-panel: #18181e;
-    --color-border: #2a2a32;
-    --color-text: #e6e6ec;
-    --color-muted: #9a9aa6;
-    --color-accent: #4a94f0;
-    --color-accent-hover: #6ab0ff;
-
-    --color-on-accent: #ffffff;
-    --color-on-accent-soft: rgba(255, 255, 255, 0.15);
-    --color-on-accent-border: rgba(255, 255, 255, 0.3);
-
-    --color-selection: rgba(74, 148, 240, 0.25);
-    --color-selection-strong: rgba(74, 148, 240, 0.5);
-
-    --color-shadow: rgba(0, 0, 0, 0.55);
-    --color-shadow-strong: rgba(0, 0, 0, 0.65);
-    --color-backdrop: rgba(0, 0, 0, 0.6);
-
-    --color-scrollbar: rgba(255, 255, 255, 0.15);
-    --color-scrollbar-hover: rgba(255, 255, 255, 0.3);
-  }
+  --color-scrollbar: rgba(45, 40, 32, 0.22);
+  --color-scrollbar-hover: rgba(45, 40, 32, 0.38);
 }
 
 /* ---- Neonflux ----
diff --git a/tests/selftest-scenario.js b/tests/selftest-scenario.js
index 132bf7c..eb0ea63 100644
--- a/tests/selftest-scenario.js
+++ b/tests/selftest-scenario.js
@@ -762,10 +762,16 @@ const BOOK3_DIR = __BOOKDIR3_VALUE__;
     out.themeSelectOptions = themeSelect
       ? Array.from(themeSelect.options).map((o) => o.value)
       : [];
-    out.themeHasDefault = out.themeSelectOptions.includes("default");
+    out.themeHasLight = out.themeSelectOptions.includes("light");
     out.themeHasNeonflux = out.themeSelectOptions.includes("neonflux");
-    out.themeInitialAttr = document.documentElement.getAttribute("data-theme");
     out.themeInitialStored = await window.folio.getTheme();
+    out.themeInitialAttr = document.documentElement.getAttribute("data-theme");
+    // Old saves may hold "default", which must resolve to the Light theme
+    // (migration). Valid saved themes must be restored exactly on startup.
+    out.themeInitialConsistent =
+      out.themeInitialStored === "default" || out.themeInitialStored === "light"
+        ? out.themeInitialAttr === "light"
+        : out.themeInitialAttr === out.themeInitialStored;
 
     // Switch to Neonflux: applies immediately and persists via IPC.
     themeSelect.value = "neonflux";
@@ -784,26 +790,55 @@ const BOOK3_DIR = __BOOKDIR3_VALUE__;
       neonAccent.toLowerCase() === "#22d3ee";
 
     // Neonflux is dark: computed background of the app should be near-black.
-    const bodyBg = getComputedStyle(document.body).backgroundColor;
-    out.themeNeonfluxDark = /rgb\((10|11|12|9|8),/.test(bodyBg);
+    const neonBodyBg = getComputedStyle(document.body).backgroundColor;
+    out.themeNeonfluxDark = /rgb\((10|11|12|9|8),/.test(neonBodyBg);
 
     // Switching themes must not touch the manuscript content.
     out.themeContentUnchanged = navBook.state.doc.toString() === docBeforeTheme;
 
-    // Switch back to Default: applies immediately and persists.
-    themeSelect.value = "default";
+    // Switch to Light: applies immediately and persists.
+    themeSelect.value = "light";
     themeSelect.dispatchEvent(new Event("change", { bubbles: true }));
     await navWait(200);
-    out.themeDefaultAttr = document.documentElement.getAttribute("data-theme");
-    out.themeDefaultStored = await window.folio.getTheme();
-    const defaultBg = themeVar("--color-bg");
-    out.themeDefaultBg = defaultBg;
-    out.themeDefaultApplied =
-      out.themeDefaultAttr === "default" &&
-      out.themeDefaultStored === "default" &&
-      (defaultBg.toLowerCase() === "#ffffff" || defaultBg.toLowerCase() === "#0f0f12");
+    out.themeLightAttr = document.documentElement.getAttribute("data-theme");
+    out.themeLightStored = await window.folio.getTheme();
+    const lightBg = themeVar("--color-bg");
+    const lightAccent = themeVar("--color-accent");
+    out.themeLightBg = lightBg;
+    out.themeLightAccent = lightAccent;
+    out.themeLightApplied =
+      out.themeLightAttr === "light" &&
+      out.themeLightStored === "light" &&
+      lightBg.toLowerCase() === "#fffdf9" &&
+      lightAccent.toLowerCase() === "#2f6b5f";
+
+    // Light is light: computed background must be a warm off-white, never the
+    // near-black used by Neonflux.
+    const lightBodyBg = getComputedStyle(document.body).backgroundColor;
+    out.themeLightNotDark = !/rgb\((10|11|12|9|8),/.test(lightBodyBg);
     out.themeContentUnchanged2 = navBook.state.doc.toString() === docBeforeTheme;
 
+    // Round-trip: back to Neonflux restores it exactly.
+    themeSelect.value = "neonflux";
+    themeSelect.dispatchEvent(new Event("change", { bubbles: true }));
+    await navWait(200);
+    out.themeRoundTripAttr = document.documentElement.getAttribute("data-theme");
+    out.themeRoundTripStored = await window.folio.getTheme();
+    out.themeRoundTripOk =
+      out.themeRoundTripAttr === "neonflux" &&
+      out.themeRoundTripStored === "neonflux" &&
+      themeVar("--color-bg").toLowerCase() === "#0a0d14" &&
+      themeVar("--color-accent").toLowerCase() === "#22d3ee";
+
+    // Leave the app on Light so subsequent runs start deterministically.
+    themeSelect.value = "light";
+    themeSelect.dispatchEvent(new Event("change", { bubbles: true }));
+    await navWait(200);
+    out.themeFinalAttr = document.documentElement.getAttribute("data-theme");
+    out.themeFinalStored = await window.folio.getTheme();
+    out.themeFinalLightOk = out.themeFinalAttr === "light" && out.themeFinalStored === "light";
+    out.themeContentUnchanged3 = navBook.state.doc.toString() === docBeforeTheme;
+
     const okFlags = [
       "dndMoved",
       "kbMoved",
@@ -876,13 +911,18 @@ const BOOK3_DIR = __BOOKDIR3_VALUE__;
       "navNextAfterReorderOk",
       "navBreaksOk",
       "themeSelectPresent",
-      "themeHasDefault",
+      "themeHasLight",
       "themeHasNeonflux",
+      "themeInitialConsistent",
       "themeNeonfluxApplied",
       "themeNeonfluxDark",
       "themeContentUnchanged",
-      "themeDefaultApplied",
+      "themeLightApplied",
+      "themeLightNotDark",
       "themeContentUnchanged2",
+      "themeRoundTripOk",
+      "themeFinalLightOk",
+      "themeContentUnchanged3",
     ];
     out.all = okFlags.every((f) => out[f] === true);
   } catch (e) {