diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..b8f2743
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2026-01-20 - XSync vs XFlush in Event-Driven Drawing
+**Learning:** `XSync` is a blocking round-trip to the X server, while `XFlush` is asynchronous. In `instantwm`, `XSync` was used in `drw_map` (called on every bar redraw) and `resizeclient` (called on every window resize), causing significant performance degradation due to unnecessary waiting for server confirmation.
+**Action:** Replace `XSync` with `XFlush` in high-frequency drawing/window management paths when immediate confirmation is not strictly required for logic correctness.
diff --git a/client.c b/client.c
index 13f1e27..c03e6b4 100644
--- a/client.c
+++ b/client.c
@@ -279,7 +279,7 @@ void resizeclient(Client *c, int x, int y, int w, int h) {
     XConfigureWindow(dpy, c->win,
                      CWX | CWY | CWWidth | CWHeight | CWBorderWidth, &wc);
     configure(c);
-    XSync(dpy, False);
+    XFlush(dpy);
 }
 
 void updatetitle(Client *c) {
diff --git a/drw.c b/drw.c
index 7e99a38..e3f9501 100644
--- a/drw.c
+++ b/drw.c
@@ -494,7 +494,7 @@ void drw_map(Drw *drw, Window win, int x, int y, unsigned int w,
     }
 
     XCopyArea(drw->dpy, drw->drawable, win, drw->gc, x, y, w, h, x, y);
-    XSync(drw->dpy, False);
+    XFlush(drw->dpy);
 }
 
 unsigned int drw_fontset_getwidth(Drw *drw, const char *text) {