diff --git a/packages/review-editor/components/ReviewHeaderMenu.tsx b/packages/review-editor/components/ReviewHeaderMenu.tsx
index ffdaf002b..4004b04d1 100644
--- a/packages/review-editor/components/ReviewHeaderMenu.tsx
+++ b/packages/review-editor/components/ReviewHeaderMenu.tsx
@@ -1,4 +1,4 @@
-import React, { useMemo } from 'react';
+import React from 'react';
 import {
   ActionMenu,
   ActionMenuDivider,
@@ -6,6 +6,7 @@ import {
   ActionMenuSectionLabel,
 } from '@plannotator/ui/components/ActionMenu';
 import { useTheme } from '@plannotator/ui/components/ThemeProvider';
+import { THEME_MODES } from '@plannotator/ui/components/themeModes';
 import { MenuVersionSection } from '@plannotator/ui/components/MenuVersionSection';
 import { ReviewAgentsIcon } from '@plannotator/ui/components/ReviewAgentsIcon';
 import { TextShimmer } from '@plannotator/ui/components/TextShimmer';
@@ -44,10 +45,7 @@ export const ReviewHeaderMenu: React.FC<ReviewHeaderMenuProps> = ({
   origin,
   isWSL = false,
 }) => {
-  const { theme, resolvedMode, setTheme } = useTheme();
-  const activeTheme = useMemo<'light' | 'dark'>(() => {
-    return theme === 'system' ? resolvedMode : theme;
-  }, [resolvedMode, theme]);
+  const { theme, setTheme } = useTheme();
 
   const showUpdateDot = !!updateInfo?.updateAvailable && !updateInfo.dismissed;
 
@@ -87,21 +85,21 @@ export const ReviewHeaderMenu: React.FC<ReviewHeaderMenuProps> = ({
           <div className="px-3 py-2 space-y-1.5">
             <ActionMenuSectionLabel>Theme</ActionMenuSectionLabel>
             <div className="flex items-center gap-1 rounded-lg bg-muted/50 p-0.5">
-              {(['light', 'dark'] as const).map((mode) => (
+              {THEME_MODES.map(({ id, label, Icon }) => (
                 <button
-                  key={mode}
+                  key={id}
                   onClick={() => {
                     closeMenu();
-                    setTheme(mode);
+                    setTheme(id);
                   }}
                   className={`flex flex-1 items-center justify-center gap-1.5 rounded-md px-2 py-1 text-[11px] font-medium transition-colors ${
-                    activeTheme === mode
+                    theme === id
                       ? 'bg-background text-foreground shadow-sm'
                       : 'text-muted-foreground hover:text-foreground'
                   }`}
                 >
-                  {mode === 'light' ? <SunIcon /> : <MoonIcon />}
-                  <span className="capitalize">{mode}</span>
+                  <Icon />
+                  <span>{label}</span>
                 </button>
               ))}
             </div>
@@ -213,19 +211,6 @@ const ExportIcon = () => (
   </svg>
 );
 
-const SunIcon = () => (
-  <svg className="w-3.5 h-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path strokeLinecap="round" strokeLinejoin="round" d="M12 3v2.25M12 18.75V21M3 12h2.25M18.75 12H21M5.636 5.636l1.591 1.591M16.773 16.773l1.591 1.591M5.636 18.364l1.591-1.591M16.773 7.227l1.591-1.591" />
-    <circle cx="12" cy="12" r="3.25" />
-  </svg>
-);
-
-const MoonIcon = () => (
-  <svg className="w-3.5 h-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path strokeLinecap="round" strokeLinejoin="round" d="M21 12.79A9 9 0 1111.21 3c-.18.57-.21 1.19-.21 1.82A8 8 0 0019.18 13c.63 0 1.25-.03 1.82-.21z" />
-  </svg>
-);
-
 const FileTreeMenuIcon = () => (
   <svg className="w-3.5 h-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
     <path strokeLinecap="round" strokeLinejoin="round" d="M3 7v10a2 2 0 002 2h14a2 2 0 002-2V9a2 2 0 00-2-2h-6l-2-2H5a2 2 0 00-2 2z" />
diff --git a/packages/ui/components/ModeToggle.tsx b/packages/ui/components/ModeToggle.tsx
index 8119d4fc3..1f0a7ecee 100644
--- a/packages/ui/components/ModeToggle.tsx
+++ b/packages/ui/components/ModeToggle.tsx
@@ -1,5 +1,6 @@
 import React, { useState, useRef, useEffect } from 'react';
 import { useTheme } from './ThemeProvider';
+import { THEME_MODES } from './themeModes';
 
 export function ModeToggle() {
   const { theme, setTheme } = useTheme();
@@ -48,17 +49,17 @@ export function ModeToggle() {
 
       {isOpen && (
         <div className="absolute right-0 mt-1 w-32 rounded-lg border border-border bg-popover shadow-xl z-50 overflow-hidden py-1">
-          {(['light', 'dark', 'system'] as const).map((t) => (
+          {THEME_MODES.map(({ id, label }) => (
             <button
-              key={t}
-              onClick={() => { setTheme(t); setIsOpen(false); }}
-              className={`w-full px-3 py-1.5 text-left text-xs capitalize transition-colors ${
-                theme === t
+              key={id}
+              onClick={() => { setTheme(id); setIsOpen(false); }}
+              className={`w-full px-3 py-1.5 text-left text-xs transition-colors ${
+                theme === id
                   ? 'text-primary bg-primary/10 font-medium'
                   : 'text-popover-foreground hover:bg-muted'
               }`}
             >
-              {t}
+              {label}
             </button>
           ))}
         </div>
diff --git a/packages/ui/components/PlanHeaderMenu.tsx b/packages/ui/components/PlanHeaderMenu.tsx
index 2855ecfde..875d26077 100644
--- a/packages/ui/components/PlanHeaderMenu.tsx
+++ b/packages/ui/components/PlanHeaderMenu.tsx
@@ -6,7 +6,7 @@ import {
   ActionMenuSectionLabel,
 } from './ActionMenu';
 import { useTheme } from './ThemeProvider';
-import { SunIcon, MoonIcon, SystemIcon } from './icons/themeIcons';
+import { THEME_MODES } from './themeModes';
 import { ReviewAgentsIcon } from './ReviewAgentsIcon';
 import { MenuVersionSection } from './MenuVersionSection';
 import { TextShimmer } from './TextShimmer';
@@ -101,21 +101,21 @@ export const PlanHeaderMenu: React.FC<PlanHeaderMenuProps> = ({
           <div className="px-3 py-2 space-y-1.5">
             <ActionMenuSectionLabel>Theme</ActionMenuSectionLabel>
             <div className="flex items-center gap-1 rounded-lg bg-muted/50 p-0.5">
-              {(['light', 'dark', 'system'] as const).map((mode) => (
+              {THEME_MODES.map(({ id, label, Icon }) => (
                 <button
-                  key={mode}
+                  key={id}
                   onClick={() => {
                     closeMenu();
-                    setTheme(mode);
+                    setTheme(id);
                   }}
                   className={`flex flex-1 items-center justify-center gap-1.5 rounded-md px-2 py-1 text-[11px] font-medium transition-colors ${
-                    theme === mode
+                    theme === id
                       ? 'bg-background text-foreground shadow-sm'
                       : 'text-muted-foreground hover:text-foreground'
                   }`}
                 >
-                  {mode === 'light' ? <SunIcon /> : mode === 'dark' ? <MoonIcon /> : <SystemIcon />}
-                  <span className="capitalize">{mode}</span>
+                  <Icon />
+                  <span>{label}</span>
                 </button>
               ))}
             </div>
diff --git a/packages/ui/components/ThemeProvider.tsx b/packages/ui/components/ThemeProvider.tsx
index 6fc8c096d..ee326c37b 100644
--- a/packages/ui/components/ThemeProvider.tsx
+++ b/packages/ui/components/ThemeProvider.tsx
@@ -1,8 +1,7 @@
 import { createContext, useCallback, useContext, useEffect, useMemo, useState } from 'react';
 import { storage } from '../utils/storage';
 import { BUILT_IN_THEMES, type ThemeInfo } from '../utils/themeRegistry';
-
-export type Mode = 'dark' | 'light' | 'system';
+import type { Mode } from './themeModes';
 
 type ThemeProviderState = {
   // Mode (dark/light/system) — backward-compatible with old "theme" API
diff --git a/packages/ui/components/ThemeTab.tsx b/packages/ui/components/ThemeTab.tsx
index b3d9cd72f..49c07a7f9 100644
--- a/packages/ui/components/ThemeTab.tsx
+++ b/packages/ui/components/ThemeTab.tsx
@@ -1,6 +1,6 @@
 import React from 'react';
-import { useTheme, type Mode } from './ThemeProvider';
-import { SunIcon, MoonIcon, SystemIcon } from './icons/themeIcons';
+import { useTheme } from './ThemeProvider';
+import { THEME_MODES } from './themeModes';
 
 interface ThemeTabProps {
   onPreview?: () => void;
@@ -16,39 +16,22 @@ export const ThemeTab: React.FC<ThemeTabProps> = ({ onPreview, compact }) => {
       <div className={compact ? 'flex items-center gap-3 mb-2' : 'space-y-2'}>
         {!compact && <label className="text-xs font-medium text-muted-foreground uppercase tracking-wide">Mode</label>}
         <div className="flex gap-1">
-          {(['dark', 'light', 'system'] as Mode[]).map(m => {
-            const isActive = mode === m;
-            return (
-              <button
-                key={m}
-                onClick={() => setMode(m)}
-                className={`px-2.5 py-1.5 rounded-md text-xs font-medium transition-colors ${
-                  isActive
-                    ? 'bg-primary text-primary-foreground'
-                    : 'bg-muted text-muted-foreground hover:text-foreground'
-                }`}
-              >
-                {m === 'dark' && (
-                  <span className="flex items-center gap-1.5">
-                    <MoonIcon className="w-3 h-3" />
-                    Dark
-                  </span>
-                )}
-                {m === 'light' && (
-                  <span className="flex items-center gap-1.5">
-                    <SunIcon className="w-3 h-3" />
-                    Light
-                  </span>
-                )}
-                {m === 'system' && (
-                  <span className="flex items-center gap-1.5">
-                    <SystemIcon className="w-3 h-3" />
-                    System
-                  </span>
-                )}
-              </button>
-            );
-          })}
+          {THEME_MODES.map(({ id, label, Icon }) => (
+            <button
+              key={id}
+              onClick={() => setMode(id)}
+              className={`px-2.5 py-1.5 rounded-md text-xs font-medium transition-colors ${
+                mode === id
+                  ? 'bg-primary text-primary-foreground'
+                  : 'bg-muted text-muted-foreground hover:text-foreground'
+              }`}
+            >
+              <span className="flex items-center gap-1.5">
+                <Icon className="w-3 h-3" />
+                {label}
+              </span>
+            </button>
+          ))}
         </div>
         {compact && (
           <span className="text-[10px] text-muted-foreground/60 ml-auto flex items-center gap-1">
diff --git a/packages/ui/components/icons/themeIcons.tsx b/packages/ui/components/icons/themeIcons.tsx
index dad95f89c..218a9d4d1 100644
--- a/packages/ui/components/icons/themeIcons.tsx
+++ b/packages/ui/components/icons/themeIcons.tsx
@@ -12,7 +12,7 @@ import React from 'react';
  * the dropdown segmented controls use w-3.5, the settings tab uses w-3.
  */
 
-interface IconProps {
+export interface IconProps {
   className?: string;
 }
 
diff --git a/packages/ui/components/themeModes.ts b/packages/ui/components/themeModes.ts
new file mode 100644
index 000000000..4162fe155
--- /dev/null
+++ b/packages/ui/components/themeModes.ts
@@ -0,0 +1,23 @@
+import type { FC } from 'react';
+import { SunIcon, MoonIcon, SystemIcon } from './icons/themeIcons';
+import type { IconProps } from './icons/themeIcons';
+
+/** A theme mode paired with how a picker draws it. */
+interface ThemeMode {
+  readonly id: string;
+  readonly label: string;
+  readonly Icon: FC<IconProps>;
+}
+
+/** The one shared list of theme modes every picker renders.
+ *  `as const` preserves each literal `id`; `satisfies` checks each
+ *  entry's shape without widening it. */
+export const THEME_MODES = [
+  { id: 'light', label: 'Light', Icon: SunIcon },
+  { id: 'dark', label: 'Dark', Icon: MoonIcon },
+  { id: 'system', label: 'System', Icon: SystemIcon },
+] as const satisfies readonly ThemeMode[];
+
+/** A theme mode's id — the union of every id in THEME_MODES.
+ *  A mode cannot exist without a render entry. */
+export type Mode = (typeof THEME_MODES)[number]['id'];