diff --git a/src-tauri/tauri.conf.json b/src-tauri/tauri.conf.json
index 3fafb59d..27a543ca 100644
--- a/src-tauri/tauri.conf.json
+++ b/src-tauri/tauri.conf.json
@@ -16,6 +16,8 @@
         "title": "Laputa",
         "width": 1400,
         "height": 900,
+        "minWidth": 800,
+        "minHeight": 400,
         "resizable": true,
         "fullscreen": false,
         "titleBarStyle": "Overlay",
diff --git a/src/App.css b/src/App.css
index 71c33ce1..de568d63 100644
--- a/src/App.css
+++ b/src/App.css
@@ -16,7 +16,8 @@
 }
 
 .app__sidebar {
-  flex-shrink: 0;
+  flex-shrink: 1;
+  min-width: 180px;
   display: flex;
   flex-direction: column;
 }
@@ -26,7 +27,8 @@
 }
 
 .app__note-list {
-  flex-shrink: 0;
+  flex-shrink: 10;
+  min-width: 220px;
   display: flex;
   flex-direction: column;
 }
@@ -37,7 +39,7 @@
 
 .app__editor {
   flex: 1;
-  min-width: 0;
+  min-width: 400px;
   min-height: 0;
   overflow: hidden;
   display: flex;
diff --git a/src/components/EditorRightPanel.tsx b/src/components/EditorRightPanel.tsx
index 68153b13..2dd8bf0d 100644
--- a/src/components/EditorRightPanel.tsx
+++ b/src/components/EditorRightPanel.tsx
@@ -40,7 +40,7 @@ export function EditorRightPanel({
     return (
       <div
         className="shrink-0 flex flex-col min-h-0"
-        style={{ width: inspectorWidth, height: '100%' }}
+        style={{ width: inspectorWidth, minWidth: 240, height: '100%' }}
       >
         <AiPanel
           onClose={() => onToggleAIChat?.()}
diff --git a/src/hooks/useLayoutPanels.test.ts b/src/hooks/useLayoutPanels.test.ts
new file mode 100644
index 00000000..9aae1c9a
--- /dev/null
+++ b/src/hooks/useLayoutPanels.test.ts
@@ -0,0 +1,55 @@
+import { describe, it, expect } from 'vitest'
+import { renderHook, act } from '@testing-library/react'
+import { useLayoutPanels, COLUMN_MIN_WIDTHS } from './useLayoutPanels'
+
+describe('useLayoutPanels', () => {
+  it('exports column minimum widths', () => {
+    expect(COLUMN_MIN_WIDTHS.sidebar).toBe(180)
+    expect(COLUMN_MIN_WIDTHS.noteList).toBe(220)
+    expect(COLUMN_MIN_WIDTHS.editor).toBe(400)
+    expect(COLUMN_MIN_WIDTHS.inspector).toBe(240)
+  })
+
+  it('returns default widths', () => {
+    const { result } = renderHook(() => useLayoutPanels())
+    expect(result.current.sidebarWidth).toBe(250)
+    expect(result.current.noteListWidth).toBe(300)
+    expect(result.current.inspectorWidth).toBe(280)
+  })
+
+  it('clamps sidebar resize to minimum', () => {
+    const { result } = renderHook(() => useLayoutPanels())
+    act(() => result.current.handleSidebarResize(-500))
+    expect(result.current.sidebarWidth).toBe(COLUMN_MIN_WIDTHS.sidebar)
+  })
+
+  it('clamps note list resize to minimum', () => {
+    const { result } = renderHook(() => useLayoutPanels())
+    act(() => result.current.handleNoteListResize(-500))
+    expect(result.current.noteListWidth).toBe(COLUMN_MIN_WIDTHS.noteList)
+  })
+
+  it('clamps inspector resize to minimum', () => {
+    const { result } = renderHook(() => useLayoutPanels())
+    act(() => result.current.handleInspectorResize(500))
+    expect(result.current.inspectorWidth).toBe(COLUMN_MIN_WIDTHS.inspector)
+  })
+
+  it('clamps sidebar resize to maximum', () => {
+    const { result } = renderHook(() => useLayoutPanels())
+    act(() => result.current.handleSidebarResize(500))
+    expect(result.current.sidebarWidth).toBe(400)
+  })
+
+  it('clamps note list resize to maximum', () => {
+    const { result } = renderHook(() => useLayoutPanels())
+    act(() => result.current.handleNoteListResize(500))
+    expect(result.current.noteListWidth).toBe(500)
+  })
+
+  it('clamps inspector resize to maximum', () => {
+    const { result } = renderHook(() => useLayoutPanels())
+    act(() => result.current.handleInspectorResize(-500))
+    expect(result.current.inspectorWidth).toBe(500)
+  })
+})
diff --git a/src/hooks/useLayoutPanels.ts b/src/hooks/useLayoutPanels.ts
index 192c276f..d2b15b25 100644
--- a/src/hooks/useLayoutPanels.ts
+++ b/src/hooks/useLayoutPanels.ts
@@ -1,12 +1,19 @@
 import { useCallback, useState } from 'react'
 
+export const COLUMN_MIN_WIDTHS = {
+  sidebar: 180,
+  noteList: 220,
+  editor: 400,
+  inspector: 240,
+} as const
+
 export function useLayoutPanels() {
   const [sidebarWidth, setSidebarWidth] = useState(250)
   const [noteListWidth, setNoteListWidth] = useState(300)
   const [inspectorWidth, setInspectorWidth] = useState(280)
   const [inspectorCollapsed, setInspectorCollapsed] = useState(false)
-  const handleSidebarResize = useCallback((delta: number) => setSidebarWidth((w) => Math.max(150, Math.min(400, w + delta))), [])
-  const handleNoteListResize = useCallback((delta: number) => setNoteListWidth((w) => Math.max(200, Math.min(500, w + delta))), [])
-  const handleInspectorResize = useCallback((delta: number) => setInspectorWidth((w) => Math.max(200, Math.min(500, w - delta))), [])
+  const handleSidebarResize = useCallback((delta: number) => setSidebarWidth((w) => Math.max(COLUMN_MIN_WIDTHS.sidebar, Math.min(400, w + delta))), [])
+  const handleNoteListResize = useCallback((delta: number) => setNoteListWidth((w) => Math.max(COLUMN_MIN_WIDTHS.noteList, Math.min(500, w + delta))), [])
+  const handleInspectorResize = useCallback((delta: number) => setInspectorWidth((w) => Math.max(COLUMN_MIN_WIDTHS.inspector, Math.min(500, w - delta))), [])
   return { sidebarWidth, noteListWidth, inspectorWidth, inspectorCollapsed, setInspectorCollapsed, handleSidebarResize, handleNoteListResize, handleInspectorResize }
 }