diff --git a/.vscode/launch.json b/.vscode/launch.json
index 5ea80f1..f6a7815 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -3,7 +3,7 @@
     "configurations": [
         {
             "name": "Debug autosample (macOS)",
-            "type": "lldb",
+            "type": "lldb-dap",
             "request": "launch",
             "program": "${workspaceFolder}/build_debug/autosample.app/Contents/MacOS/autosample",
             "args": [],
diff --git a/src/renderer/renderer_metal.mm b/src/renderer/renderer_metal.mm
index bc03bdf..c97fd29 100644
--- a/src/renderer/renderer_metal.mm
+++ b/src/renderer/renderer_metal.mm
@@ -203,6 +203,14 @@ static bool create_font_atlas(Renderer *r, F32 font_size) {
     // White text
     CGContextSetGrayFillColor(ctx, 1.0, 1.0);
 
+    // Flip CG context so (0,0) is top-left, matching our pen_y convention
+    CGContextTranslateCTM(ctx, 0, render_h);
+    CGContextScaleCTM(ctx, 1.0, -1.0);
+
+    // In the flipped context, Core Text draws upside down unless we undo the
+    // text matrix flip. Set the text matrix to flip Y back for glyph rendering.
+    CGContextSetTextMatrix(ctx, CGAffineTransformMake(1, 0, 0, -1, 0, 0));
+
     // Render each glyph
     int pen_x = SS, pen_y = SS;
     int row_height = 0;
@@ -230,9 +238,10 @@ static bool create_font_atlas(Renderer *r, F32 font_size) {
 
         if (pen_y + gh >= render_h) { CFRelease(line); break; }
 
-        // CoreGraphics has bottom-left origin; draw relative to pen position
+        // Context is flipped to top-left origin. Position baseline:
+        // pen_y + SS is the top of the glyph cell, baseline is ascent below that.
         F32 draw_x = (F32)(pen_x + SS) - (F32)bounds.origin.x;
-        F32 draw_y = (F32)(render_h - pen_y - SS) - ascent;
+        F32 draw_y = (F32)(pen_y + SS) + ascent;
 
         CGContextSetTextPosition(ctx, draw_x, draw_y);
         CTLineDraw(line, ctx);
@@ -252,18 +261,16 @@ static bool create_font_atlas(Renderer *r, F32 font_size) {
         CFRelease(line);
     }
 
-    // Box-filter downsample
+    // Box-filter downsample (context is flipped, so bitmap is already top-down)
     uint8_t *src = (uint8_t *)CGBitmapContextGetData(ctx);
     uint8_t *atlas_data = (uint8_t *)malloc(FONT_ATLAS_W * FONT_ATLAS_H);
 
-    // CoreGraphics bitmap has bottom-left origin — flip Y during downsample
     for (int y = 0; y < FONT_ATLAS_H; y++) {
         for (int x = 0; x < FONT_ATLAS_W; x++) {
             int sum = 0;
             for (int sy = 0; sy < SS; sy++) {
                 for (int sx = 0; sx < SS; sx++) {
-                    int src_y = render_h - 1 - (y * SS + sy); // flip Y
-                    int src_idx = src_y * render_w + (x * SS + sx);
+                    int src_idx = (y * SS + sy) * render_w + (x * SS + sx);
                     sum += src[src_idx];
                 }
             }
@@ -620,17 +627,7 @@ void renderer_destroy(Renderer *r) {
 }
 
 bool renderer_begin_frame(Renderer *r) {
-    dispatch_semaphore_wait(r->frame_semaphore, DISPATCH_TIME_FOREVER);
-
-    id<CAMetalDrawable> drawable = [r->metal_layer nextDrawable];
-    if (!drawable) {
-        dispatch_semaphore_signal(r->frame_semaphore);
-        return false;
-    }
-
-    // Store drawable for end_frame (use a thread-local or just re-acquire)
-    // We'll re-acquire in end_frame — nextDrawable is fast if we just called it
-    dispatch_semaphore_signal(r->frame_semaphore);
+    if (r->width <= 0 || r->height <= 0) return false;
     return true;
 }