diff --git a/src/ui-touch/UITask.cpp b/src/ui-touch/UITask.cpp
index 736df7e..f95e4b0 100644
--- a/src/ui-touch/UITask.cpp
+++ b/src/ui-touch/UITask.cpp
@@ -1950,7 +1950,19 @@ static bool g_cap_touch_hw_started = false;
 // build). 24 × 240 × 2 B = 11.5 KB. Flush time is bound by SPI clock
 // (80 MHz), not memcpy speed, so the throughput delta is small —
 // LVGL just calls flush_cb more often.
+#if defined(HAS_TDISPLAY_P4)
+// DIAGNOSTIC (#167): the T-Display P4 is a DSI video-mode panel with a SINGLE framebuffer, so every
+// LVGL band is copied into the buffer the panel is actively scanning out. At 24 lines a full-screen
+// repaint is ~26 back-to-back DMA transfers into that live buffer -- and the events testers report
+// (a message arriving, opening a chat with unread, adding/deleting a contact) are exactly the ones
+// that rebuild the whole screen, while panning the map only repaints its own region and never
+// flashes. Wider bands make the same repaint ~10 transfers instead of ~26. Kept just small enough
+// that the 2x upscale scratch still fits internal SRAM (568*128*2 = ~145 KB), so this changes ONLY
+// the burst count and not where the scratch lives.
+static constexpr int LV_DRAW_BUF_LINES = 64;
+#else
 static constexpr int LV_DRAW_BUF_LINES = 24;
+#endif
 static lv_color_t* g_draw_buffer = nullptr;
 static uint32_t    g_draw_buf_px  = 240 * LV_DRAW_BUF_LINES;   // actual buffer size in px; shrinks if the full alloc fails at boot
 #if CAP_LARGE_SCREEN
diff --git a/variants/tdisplay_p4/RM69A10Display.cpp b/variants/tdisplay_p4/RM69A10Display.cpp
index cdcad22..ee5d922 100644
--- a/variants/tdisplay_p4/RM69A10Display.cpp
+++ b/variants/tdisplay_p4/RM69A10Display.cpp
@@ -3,6 +3,7 @@
 #include "RM69A10Display.h"
 #include <Arduino.h>
 #include "esp_heap_caps.h"
+#include "esp_cache.h"   // esp_cache_msync — flush the memset framebuffer out to the DSI DMA
 #include "esp_ldo_regulator.h"
 #include "Xl9535.h"                 // SCREEN_RST lives on the expander (reset_gpio_num = -1)
 #include "esp_lcd_mipi_dsi.h"
@@ -109,6 +110,19 @@ bool RM69A10Display::begin() {
 
   esp_lcd_panel_reset(_panel);
   if (esp_lcd_panel_init(_panel) != ESP_OK) { Serial.println("[RM69A10] panel_init fail"); return false; }
+
+  // Blank the framebuffer BEFORE switching the panel on. It is freshly allocated PSRAM, so it holds
+  // garbage; turning the panel on first meant the DSI streamed that garbage to the screen until the
+  // clear below finished -- the colour flash testers see before the boot splash (#167). Write the
+  // buffer directly (memset + a cache flush to make it visible to the DSI's DMA) instead of pushing
+  // strips through draw_bitmap: it is one pass with the panel still dark, and it avoids a burst of
+  // 39 back-to-back DMA transfers into a buffer the panel is scanning out.
+  void* fb = nullptr;
+  if (esp_lcd_dpi_panel_get_frame_buffer(_panel, 1, &fb) == ESP_OK && fb) {
+    const size_t fb_bytes = (size_t)RM_W * RM_H * 2;
+    memset(fb, 0, fb_bytes);
+    esp_cache_msync(fb, fb_bytes, ESP_CACHE_MSYNC_FLAG_DIR_C2M);
+  }
   esp_lcd_panel_disp_on_off(_panel, true);
 
   // Brightness: the init array ships 0x51=0 (placeholder), and RM69A10 brightness is driven at
@@ -125,20 +139,6 @@ bool RM69A10Display::begin() {
   cbs.on_color_trans_done = rm69a10TransDone;
   esp_lcd_dpi_panel_register_event_callbacks(_panel, &cbs, nullptr);
 
-  // Clear the panel framebuffer to black once, so nothing stale shows before LVGL's first flush.
-  {
-    const int SH = 32;
-    uint16_t* strip = (uint16_t*)heap_caps_calloc((size_t)RM_W * SH, 2, MALLOC_CAP_SPIRAM);
-    if (strip) {
-      for (int y0 = 0; y0 < RM_H; y0 += SH) {
-        int hh = (y0 + SH <= RM_H) ? SH : (RM_H - y0);
-        esp_lcd_panel_draw_bitmap(_panel, 0, y0, RM_W, y0 + hh, strip);
-        if (s_flush_sem) xSemaphoreTake(s_flush_sem, pdMS_TO_TICKS(100));   // let the copy finish before reusing/freeing strip
-      }
-      free(strip);
-    }
-  }
-
   Serial.printf("[RM69A10] up %dx%d\n", RM_W, RM_H);
   return true;
 }