diff --git a/apps/ui/src/components/views/project-settings-view/project-theme-section.tsx b/apps/ui/src/components/views/project-settings-view/project-theme-section.tsx
index d0d7744f..dca0f7b2 100644
--- a/apps/ui/src/components/views/project-settings-view/project-theme-section.tsx
+++ b/apps/ui/src/components/views/project-settings-view/project-theme-section.tsx
@@ -10,7 +10,11 @@ import {
 } from '@/components/ui/select';
 import { Palette, Moon, Sun, Type } from 'lucide-react';
 import { darkThemes, lightThemes, type Theme } from '@/config/theme-options';
-import { UI_SANS_FONT_OPTIONS, UI_MONO_FONT_OPTIONS } from '@/config/ui-font-options';
+import {
+  UI_SANS_FONT_OPTIONS,
+  UI_MONO_FONT_OPTIONS,
+  DEFAULT_FONT_VALUE,
+} from '@/config/ui-font-options';
 import { cn } from '@/lib/utils';
 import { useAppStore } from '@/store/app-store';
 import type { Project } from '@/lib/electron';
@@ -27,13 +31,17 @@ export function ProjectThemeSection({ project }: ProjectThemeSectionProps) {
     setProjectFontMono,
   } = useAppStore();
   const [activeTab, setActiveTab] = useState<'dark' | 'light'>('dark');
-  const [fontSans, setFontSansLocal] = useState<string>(project.fontFamilySans || '');
-  const [fontMono, setFontMonoLocal] = useState<string>(project.fontFamilyMono || '');
+  const [fontSans, setFontSansLocal] = useState<string>(
+    project.fontFamilySans || DEFAULT_FONT_VALUE
+  );
+  const [fontMono, setFontMonoLocal] = useState<string>(
+    project.fontFamilyMono || DEFAULT_FONT_VALUE
+  );
 
   // Sync font state when project changes
   useEffect(() => {
-    setFontSansLocal(project.fontFamilySans || '');
-    setFontMonoLocal(project.fontFamilyMono || '');
+    setFontSansLocal(project.fontFamilySans || DEFAULT_FONT_VALUE);
+    setFontMonoLocal(project.fontFamilyMono || DEFAULT_FONT_VALUE);
   }, [project]);
 
   const projectTheme = project.theme as Theme | undefined;
@@ -58,14 +66,14 @@ export function ProjectThemeSection({ project }: ProjectThemeSectionProps) {
 
   const handleFontSansChange = (value: string) => {
     setFontSansLocal(value);
-    // Empty string means default, so we pass null to clear the override
-    setProjectFontSans(project.id, value || null);
+    // 'default' means use theme default, so we pass null to clear the override
+    setProjectFontSans(project.id, value === DEFAULT_FONT_VALUE ? null : value);
   };
 
   const handleFontMonoChange = (value: string) => {
     setFontMonoLocal(value);
-    // Empty string means default, so we pass null to clear the override
-    setProjectFontMono(project.id, value || null);
+    // 'default' means use theme default, so we pass null to clear the override
+    setProjectFontMono(project.id, value === DEFAULT_FONT_VALUE ? null : value);
   };
 
   return (
@@ -214,8 +222,15 @@ export function ProjectThemeSection({ project }: ProjectThemeSectionProps) {
                 </SelectTrigger>
                 <SelectContent>
                   {UI_SANS_FONT_OPTIONS.map((option) => (
-                    <SelectItem key={option.value || 'default-sans'} value={option.value}>
-                      <span style={{ fontFamily: option.value || undefined }}>{option.label}</span>
+                    <SelectItem key={option.value} value={option.value}>
+                      <span
+                        style={{
+                          fontFamily:
+                            option.value === DEFAULT_FONT_VALUE ? undefined : option.value,
+                        }}
+                      >
+                        {option.label}
+                      </span>
                     </SelectItem>
                   ))}
                 </SelectContent>
@@ -236,8 +251,15 @@ export function ProjectThemeSection({ project }: ProjectThemeSectionProps) {
                 </SelectTrigger>
                 <SelectContent>
                   {UI_MONO_FONT_OPTIONS.map((option) => (
-                    <SelectItem key={option.value || 'default-mono'} value={option.value}>
-                      <span style={{ fontFamily: option.value || undefined }}>{option.label}</span>
+                    <SelectItem key={option.value} value={option.value}>
+                      <span
+                        style={{
+                          fontFamily:
+                            option.value === DEFAULT_FONT_VALUE ? undefined : option.value,
+                        }}
+                      >
+                        {option.label}
+                      </span>
                     </SelectItem>
                   ))}
                 </SelectContent>
diff --git a/apps/ui/src/config/ui-font-options.ts b/apps/ui/src/config/ui-font-options.ts
index 5d40a198..98b77151 100644
--- a/apps/ui/src/config/ui-font-options.ts
+++ b/apps/ui/src/config/ui-font-options.ts
@@ -5,18 +5,21 @@
  * Users must have the fonts installed on their system for them to work.
  */
 
+// Sentinel value for "use default font" - Radix Select doesn't allow empty strings
+export const DEFAULT_FONT_VALUE = 'default';
+
 export interface UIFontOption {
-  value: string; // CSS font-family value (empty string means "use default")
+  value: string; // CSS font-family value ('default' means "use default")
   label: string; // Display label for the dropdown
 }
 
 /**
  * Sans/UI fonts for headings, labels, and general text
  *
- * Empty value means "use the theme default" (Geist Sans for all themes)
+ * 'default' value means "use the theme default" (Geist Sans for all themes)
  */
 export const UI_SANS_FONT_OPTIONS: readonly UIFontOption[] = [
-  { value: '', label: 'Default (Geist Sans)' },
+  { value: DEFAULT_FONT_VALUE, label: 'Default (Geist Sans)' },
   { value: "'Inter', system-ui, sans-serif", label: 'Inter' },
   { value: "'SF Pro', system-ui, sans-serif", label: 'SF Pro' },
   { value: "'Source Sans 3', system-ui, sans-serif", label: 'Source Sans' },
@@ -28,10 +31,10 @@ export const UI_SANS_FONT_OPTIONS: readonly UIFontOption[] = [
 /**
  * Mono/code fonts for code blocks, terminals, and monospaced text
  *
- * Empty value means "use the theme default" (Geist Mono for all themes)
+ * 'default' value means "use the theme default" (Geist Mono for all themes)
  */
 export const UI_MONO_FONT_OPTIONS: readonly UIFontOption[] = [
-  { value: '', label: 'Default (Geist Mono)' },
+  { value: DEFAULT_FONT_VALUE, label: 'Default (Geist Mono)' },
   { value: "'JetBrains Mono', monospace", label: 'JetBrains Mono' },
   { value: "'Fira Code', monospace", label: 'Fira Code' },
   { value: "'SF Mono', Menlo, Monaco, monospace", label: 'SF Mono' },
@@ -48,7 +51,7 @@ export function getFontLabel(
   fontValue: string | undefined,
   options: readonly UIFontOption[]
 ): string {
-  if (!fontValue) return options[0].label;
+  if (!fontValue || fontValue === DEFAULT_FONT_VALUE) return options[0].label;
   const option = options.find((o) => o.value === fontValue);
   return option?.label ?? fontValue;
 }
diff --git a/package-lock.json b/package-lock.json
index 66065929..c542b728 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "automaker",
-  "version": "1.0.0",
+  "version": "0.12.0rc",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "automaker",
-      "version": "1.0.0",
+      "version": "0.12.0rc",
       "hasInstallScript": true,
       "workspaces": [
         "apps/*",
@@ -29,7 +29,7 @@
     },
     "apps/server": {
       "name": "@automaker/server",
-      "version": "0.11.0",
+      "version": "0.12.0",
       "license": "SEE LICENSE IN LICENSE",
       "dependencies": {
         "@anthropic-ai/claude-agent-sdk": "0.1.76",
@@ -80,7 +80,7 @@
     },
     "apps/ui": {
       "name": "@automaker/ui",
-      "version": "0.11.0",
+      "version": "0.12.0",
       "hasInstallScript": true,
       "license": "SEE LICENSE IN LICENSE",
       "dependencies": {