diff --git a/packages/web/src/components/NumberInput.tsx b/packages/web/src/components/NumberInput.tsx
index 293da3d..11d73b3 100644
--- a/packages/web/src/components/NumberInput.tsx
+++ b/packages/web/src/components/NumberInput.tsx
@@ -73,6 +73,7 @@ export default function NumberInput({
   max = 999,
   step = 1,
   style,
+  placeholder,
   'aria-label': ariaLabel,
 }: {
   value: number
@@ -81,6 +82,7 @@ export default function NumberInput({
   max?: number
   step?: number
   style?: React.CSSProperties
+  placeholder?: string
   'aria-label'?: string
 }) {
   const valueRef = useRef(value)
@@ -113,16 +115,18 @@ export default function NumberInput({
       <input
         type="text"
         inputMode="numeric"
-        value={value}
+        value={value === 0 && placeholder ? '' : value}
+        placeholder={placeholder}
         aria-label={ariaLabel}
         onChange={(e) => {
+          if (e.target.value === '') { onChange(0); return }
           const n = parseInt(e.target.value)
           if (!isNaN(n)) onChange(clamp(n))
         }}
         style={{
           flex: 1,
           minWidth: 0,
-          padding: '8px 4px',
+          padding: '8px 8px',
           background: 'transparent',
           border: 'none',
           outline: 'none',
diff --git a/packages/web/src/pages/admin/AdminSecurity.tsx b/packages/web/src/pages/admin/AdminSecurity.tsx
index 9c91799..25a6e6f 100644
--- a/packages/web/src/pages/admin/AdminSecurity.tsx
+++ b/packages/web/src/pages/admin/AdminSecurity.tsx
@@ -727,7 +727,7 @@ function BoardSecurityCard({ board, selected, onToggleSelect }: { board: BoardSu
             aria-label="Sensitivity level"
           />
         </div>
-        <div style={{ width: 100 }}>
+        <div style={{ minWidth: 140 }}>
           <label style={{ display: 'block', color: 'var(--text-tertiary)', fontSize: 'var(--text-xs)', marginBottom: 4 }}>
             Velocity threshold
           </label>
@@ -737,6 +737,7 @@ function BoardSecurityCard({ board, selected, onToggleSelect }: { board: BoardSu
             min={0}
             max={1000}
             step={5}
+            placeholder="Auto"
           />
         </div>
         <label