diff --git a/src/mtlfns.m b/src/mtlfns.m
index 01be4988138..78f7bc4381a 100644
--- a/src/mtlfns.m
+++ b/src/mtlfns.m
@@ -111,6 +111,11 @@ FRAME must be a live graphical NS frame.  */)
      The NS terminal still handles events, menus, and scrollbars. */
   mtl_patch_terminal_rif (f);
 
+  /* Warm the glyph atlas with printable ASCII for the default face so the
+     first big redraw (e.g. first tab switch) doesn't rasterize everything at
+     once, which showed as a visible blink. */
+  mtl_warm_glyph_cache (f);
+
   /* Begin Metal rendering for this frame */
   [fd beginFrame];
   [fd endFrame];
diff --git a/src/mtlterm.h b/src/mtlterm.h
index 2686dee2ec7..949b64f5236 100644
--- a/src/mtlterm.h
+++ b/src/mtlterm.h
@@ -263,6 +263,9 @@ extern MtlFrameData *mtl_get_frame_data (struct frame *f);
 
 MtlGlyphCacheEntry *mtl_cache_glyph (CTFontRef font, uint32_t codepoint);
 
+/* Pre-rasterize printable ASCII for FRAME's default face (atlas warm-up). */
+extern void mtl_warm_glyph_cache (struct frame *f);
+
 extern bool mtl_render_offscreen_png (const char *path, int w, int h,
                                        void (^draw)(id<MTLRenderCommandEncoder>));
 extern bool mtl_render_text_png (const char *path);
diff --git a/src/mtlterm.m b/src/mtlterm.m
index a56d3bfc404..ee4bf3d9130 100644
--- a/src/mtlterm.m
+++ b/src/mtlterm.m
@@ -1820,6 +1820,20 @@ mtl_ctfont_for_face (struct face *face)
   return (CTFontRef)ptr;
 }
 
+/* Pre-rasterize the printable ASCII range for FRAME's default face into the
+   glyph atlas.  Called from mtl-enable-for-frame so the first full redraw of
+   new content (e.g. the first tab switch) does not pay the whole rasterization
+   cost at once, which showed up as a visible blink. */
+void
+mtl_warm_glyph_cache (struct frame *f)
+{
+  struct face *face = FACE_FROM_ID_OR_NULL (f, DEFAULT_FACE_ID);
+  CTFontRef ctfont = mtl_ctfont_for_face (face);
+  if (!ctfont) return;
+  for (uint32_t c = 32; c < 127; c++)
+    mtl_cache_glyph (ctfont, c);
+}
+
 /* -----------------------------------------------------------------------
    Phase 5: inline image support — NSImage (EmacsImage) → MTLTexture
    ----------------------------------------------------------------------- */