diff --git a/openspec/changes/sidepanel-ux-improvements/tasks.md b/openspec/changes/sidepanel-ux-improvements/tasks.md
index f806011..8ef35d5 100644
--- a/openspec/changes/sidepanel-ux-improvements/tasks.md
+++ b/openspec/changes/sidepanel-ux-improvements/tasks.md
@@ -22,7 +22,7 @@
 - [x] 4.1 Add `A-` and `A+` buttons to the header in `sidepanel/sidepanel.html` before the `☰` button; style them like `#open-list` in `sidepanel/sidepanel.css`
 - [x] 4.2 In `sidepanel/sidepanel.js`, implement font-size state: default 16px, range 10–24px, step 1px; apply via `editor.style.fontSize`; load from `localStorage` (`side-notes:fontSize`) at init and persist on every change
 - [x] 4.3 Wire the two buttons to decrease/increase with clamping
-- [ ] 4.4 Add keyboard shortcuts in the existing keydown handler: `Ctrl/Cmd+=` (and `+` variant) increase, `Ctrl/Cmd+-` decrease, `Ctrl/Cmd+0` reset to 16px, all with `preventDefault()`
+- [x] 4.4 Add keyboard shortcuts in the existing keydown handler: `Ctrl/Cmd+=` (and `+` variant) increase, `Ctrl/Cmd+-` decrease, `Ctrl/Cmd+0` reset to 16px, all with `preventDefault()`
 - [ ] 4.5 Verify the find match scrolling (`selectMatch`) still scrolls correctly at min and max font sizes
 
 ## 5. Validation
diff --git a/sidepanel/sidepanel.js b/sidepanel/sidepanel.js
index 662633c..753f808 100644
--- a/sidepanel/sidepanel.js
+++ b/sidepanel/sidepanel.js
@@ -414,6 +414,19 @@ document.addEventListener('keydown', (e) => {
     e.stopPropagation();
     openFind();
   }
+  // Font size: Ctrl/Cmd+= (or +) increase, Ctrl/Cmd+- decrease, Ctrl/Cmd+0 reset
+  if ((e.ctrlKey || e.metaKey) && (e.key === '=' || e.key === '+')) {
+    e.preventDefault();
+    fontSize = applyFontSize(fontSize + FONT_SIZE_STEP);
+  }
+  if ((e.ctrlKey || e.metaKey) && e.key === '-') {
+    e.preventDefault();
+    fontSize = applyFontSize(fontSize - FONT_SIZE_STEP);
+  }
+  if ((e.ctrlKey || e.metaKey) && e.key === '0') {
+    e.preventDefault();
+    fontSize = applyFontSize(FONT_SIZE_DEFAULT);
+  }
   // Escape → close find bar
   if (e.key === 'Escape' && !findBar.hidden) {
     e.preventDefault();