diff --git a/src/app/editor/dungeon/dungeon_editor.cc b/src/app/editor/dungeon/dungeon_editor.cc
index 9c8829fd..a91b01ac 100644
--- a/src/app/editor/dungeon/dungeon_editor.cc
+++ b/src/app/editor/dungeon/dungeon_editor.cc
@@ -13,6 +13,7 @@
 #include "app/zelda3/dungeon/dungeon_editor_system.h"
 #include "app/zelda3/dungeon/dungeon_object_editor.h"
 #include "app/zelda3/dungeon/room.h"
+#include "app/zelda3/dungeon/room_visual_diagnostic.h"
 #include "imgui/imgui.h"
 
 namespace yaze::editor {
@@ -283,6 +284,36 @@ void DungeonEditor::DrawCanvasAndPropertiesPanel() {
       ImGui::EndTabItem();
     }
 
+    // Visual Diagnostic tab - for debugging rendering
+    if (ImGui::BeginTabItem("Visual Diagnostic")) {
+      if (!active_rooms_.empty()) {
+        int room_id = active_rooms_[current_active_room_tab_];
+        auto& room = rooms_[room_id];
+        
+        // Show button to toggle diagnostic window
+        if (ImGui::Button("Open Diagnostic Window")) {
+          show_visual_diagnostic_ = true;
+        }
+        
+        // Render visual diagnostic
+        if (show_visual_diagnostic_) {
+          // Get the global graphics buffer for tile decoding
+          static std::vector<uint8_t> empty_gfx;
+          const auto& gfx_buffer = rom()->graphics_buffer();
+          
+          zelda3::dungeon::RoomVisualDiagnostic::DrawDiagnosticWindow(
+              &show_visual_diagnostic_,
+              gfx::Arena::Get().bg1(),
+              gfx::Arena::Get().bg2(),
+              current_palette_,
+              gfx_buffer.empty() ? empty_gfx : gfx_buffer);
+        }
+      } else {
+        ImGui::TextColored(ImVec4(1, 1, 0, 1), "No room selected. Open a room to see diagnostics.");
+      }
+      ImGui::EndTabItem();
+    }
+
     // Room Properties tab - debug and editing controls
     if (ImGui::BeginTabItem("Room Properties")) {
       if (ImGui::Button("Room Debug Info")) {
diff --git a/src/app/editor/dungeon/dungeon_editor.h b/src/app/editor/dungeon/dungeon_editor.h
index c77b5ecc..482e9c80 100644
--- a/src/app/editor/dungeon/dungeon_editor.h
+++ b/src/app/editor/dungeon/dungeon_editor.h
@@ -146,6 +146,7 @@ class DungeonEditor : public Editor {
   bool show_door_editor_ = false;
   bool show_chest_editor_ = false;
   bool show_properties_editor_ = false;
+  bool show_visual_diagnostic_ = false;
 
   uint16_t current_entrance_id_ = 0;
   uint16_t current_room_id_ = 0;
diff --git a/src/app/gfx/background_buffer.cc b/src/app/gfx/background_buffer.cc
index 6579b1fb..c7ae471d 100644
--- a/src/app/gfx/background_buffer.cc
+++ b/src/app/gfx/background_buffer.cc
@@ -36,7 +36,15 @@ void BackgroundBuffer::ClearBuffer() { std::ranges::fill(buffer_, 0); }
 void BackgroundBuffer::DrawTile(const TileInfo& tile, uint8_t* canvas,
                                 const uint8_t* tiledata, int indexoffset) {
   int tx = (tile.id_ / 16 * 512) + ((tile.id_ & 0xF) * 4);
-  uint8_t palnibble = (uint8_t)(tile.palette_ << 4);
+  
+  // Clamp palette to 0-5 (90 colors / 16 = 5.625, so max palette is 5)
+  // Palettes 6-7 would require colors 96-127, which don't exist in dungeon palettes
+  uint8_t clamped_palette = tile.palette_ & 0x07;  // Get palette 0-7
+  if (clamped_palette > 5) {
+    clamped_palette = clamped_palette % 6;  // Wrap palette 6->0, 7->1
+  }
+  
+  uint8_t palnibble = (uint8_t)(clamped_palette << 4);
   uint8_t r = tile.horizontal_mirror_ ? 1 : 0;
 
   for (int yl = 0; yl < 512; yl += 64) {
diff --git a/src/app/zelda3/dungeon/room.cc b/src/app/zelda3/dungeon/room.cc
index c51c8463..efb3897f 100644
--- a/src/app/zelda3/dungeon/room.cc
+++ b/src/app/zelda3/dungeon/room.cc
@@ -310,11 +310,25 @@ void Room::RenderRoomGraphics() {
   std::printf("5. BG1 bitmap: active=%d, size=%dx%d, data_size=%zu\n",
              bg1_bmp.is_active(), bg1_bmp.width(), bg1_bmp.height(), bg1_bmp.vector().size());
 
-  // Get the palette for this room
-  auto bg1_palette =
-      rom()->mutable_palette_group()->get_group("dungeon_main")[0].palette(0);
+  // Get the palette for this room - just use the 90-color palette as-is
+  // The SNES will index into this palette correctly without needing expansion
+  auto& dungeon_pal_group = rom()->mutable_palette_group()->get_group("dungeon_main")[0];
+  int num_palettes = dungeon_pal_group.size();
+  int palette_id = palette;
   
-  std::printf("5a. Palette loaded: size=%zu colors\n", bg1_palette.size());
+  // Validate palette ID and fall back to palette 0 if invalid
+  if (palette_id < 0 || palette_id >= num_palettes) {
+    std::printf("WARNING: Room %d has invalid palette_id=%d (max=%d), falling back to palette 0\n", 
+                room_id_, palette_id, num_palettes - 1);
+    palette_id = 0;
+  }
+  
+  // Load the 90-color dungeon palette directly
+  // The palette contains colors for BG layers - sprite colors are handled separately
+  auto bg1_palette = dungeon_pal_group.palette(palette_id);
+  
+  std::printf("5a. Palette loaded: room palette_id=%d (requested=%d), size=%zu colors\n", 
+              palette_id, palette, bg1_palette.size());
 
   // CRITICAL: Apply palette to bitmaps BEFORE creating/updating textures
   bg1_bmp.SetPaletteWithTransparent(bg1_palette, 0);
diff --git a/src/app/zelda3/dungeon/room_visual_diagnostic.cc b/src/app/zelda3/dungeon/room_visual_diagnostic.cc
new file mode 100644
index 00000000..e823b4f4
--- /dev/null
+++ b/src/app/zelda3/dungeon/room_visual_diagnostic.cc
@@ -0,0 +1,330 @@
+#include "app/zelda3/dungeon/room_visual_diagnostic.h"
+
+#include <algorithm>
+#include <cstdio>
+#include <map>
+#include <set>
+#include <vector>
+
+#include "absl/strings/str_format.h"
+#include "app/gfx/snes_tile.h"
+#include "imgui/imgui.h"
+
+namespace yaze {
+namespace zelda3 {
+namespace dungeon {
+
+void RoomVisualDiagnostic::DrawDiagnosticWindow(
+    bool* p_open,
+    gfx::BackgroundBuffer& bg1_buffer,
+    gfx::BackgroundBuffer& bg2_buffer,
+    const gfx::SnesPalette& palette,
+    const std::vector<uint8_t>& gfx16_data) {
+  
+  if (!ImGui::Begin("Room Rendering Diagnostic", p_open, ImGuiWindowFlags_AlwaysAutoResize)) {
+    ImGui::End();
+    return;
+  }
+
+  if (ImGui::CollapsingHeader("Texture Previews", ImGuiTreeNodeFlags_DefaultOpen)) {
+    DrawTexturePreview(bg1_buffer.bitmap(), "BG1 Texture");
+    ImGui::Separator();
+    DrawTexturePreview(bg2_buffer.bitmap(), "BG2 Texture");
+  }
+
+  if (ImGui::CollapsingHeader("Palette Inspector")) {
+    DrawPaletteInspector(palette);
+  }
+
+  if (ImGui::CollapsingHeader("Tile Buffer Inspector")) {
+    if (ImGui::BeginTabBar("BufferTabs")) {
+      if (ImGui::BeginTabItem("BG1 Buffer")) {
+        DrawTileBufferInspector(bg1_buffer, palette);
+        ImGui::EndTabItem();
+      }
+      if (ImGui::BeginTabItem("BG2 Buffer")) {
+        DrawTileBufferInspector(bg2_buffer, palette);
+        ImGui::EndTabItem();
+      }
+      ImGui::EndTabBar();
+    }
+  }
+
+  if (ImGui::CollapsingHeader("Pixel Inspector")) {
+    if (ImGui::BeginTabBar("PixelTabs")) {
+      if (ImGui::BeginTabItem("BG1 Pixels")) {
+        DrawPixelInspector(bg1_buffer.bitmap(), palette);
+        ImGui::EndTabItem();
+      }
+      if (ImGui::BeginTabItem("BG2 Pixels")) {
+        DrawPixelInspector(bg2_buffer.bitmap(), palette);
+        ImGui::EndTabItem();
+      }
+      ImGui::EndTabBar();
+    }
+  }
+
+  if (ImGui::CollapsingHeader("Tile Decoder")) {
+    static int test_tile_id = 0xEE;
+    ImGui::InputInt("Tile ID (hex)", &test_tile_id, 1, 16, ImGuiInputTextFlags_CharsHexadecimal);
+    test_tile_id = std::clamp(test_tile_id, 0, 0x1FF);
+    DrawTileDecoder(gfx16_data, test_tile_id);
+  }
+
+  ImGui::End();
+}
+
+void RoomVisualDiagnostic::DrawTexturePreview(const gfx::Bitmap& bitmap, const char* label) {
+  ImGui::Text("%s", label);
+  
+  if (!bitmap.is_active()) {
+    ImGui::TextColored(ImVec4(1, 0, 0, 1), "Bitmap not active");
+    return;
+  }
+
+  ImGui::Text("Size: %dx%d, Data: %zu bytes", 
+              bitmap.width(), bitmap.height(), bitmap.vector().size());
+  
+  // Show texture if available
+  if (bitmap.texture()) {
+    ImVec2 preview_size(256, 256);  // Quarter size preview
+    ImGui::Image(bitmap.texture(), preview_size);
+    
+    if (ImGui::IsItemHovered()) {
+      ImGui::BeginTooltip();
+      // Zoomed preview on hover
+      ImVec2 zoom_size(512, 512);
+      ImGui::Image(bitmap.texture(), zoom_size);
+      ImGui::EndTooltip();
+    }
+  } else {
+    ImGui::TextColored(ImVec4(1, 1, 0, 1), "No texture available");
+  }
+}
+
+void RoomVisualDiagnostic::DrawPaletteInspector(const gfx::SnesPalette& palette) {
+  ImGui::Text("Palette size: %zu colors", palette.size());
+  
+  int cols = 16;
+  for (size_t i = 0; i < palette.size(); i++) {
+    if (i % cols != 0) ImGui::SameLine();
+    
+    auto color = palette[i];
+    auto rgb = color.rgb();
+    ImVec4 imcolor(rgb.x, rgb.y, rgb.z, 1.0f);
+    
+    ImGui::PushID(static_cast<int>(i));
+    if (ImGui::ColorButton("##color", imcolor, 
+                           ImGuiColorEditFlags_NoAlpha | ImGuiColorEditFlags_NoPicker,
+                           ImVec2(20, 20))) {
+      // Clicked - could add inspection
+    }
+    ImGui::PopID();
+    
+    if (ImGui::IsItemHovered()) {
+      ImGui::SetTooltip("[%zu] SNES:0x%04X RGB:(%.0f,%.0f,%.0f)", 
+                        i, color.snes(), 
+                        rgb.x * 255, rgb.y * 255, rgb.z * 255);
+    }
+  }
+}
+
+void RoomVisualDiagnostic::DrawTileBufferInspector(gfx::BackgroundBuffer& buffer,
+                                                     const gfx::SnesPalette& palette) {
+  const auto& tile_buffer = buffer.buffer();
+  const auto& bitmap = buffer.bitmap();
+  int tiles_w = bitmap.width() / 8;
+  int tiles_h = bitmap.height() / 8;
+  
+  ImGui::Text("Buffer size: %zu tiles (%d x %d)", tile_buffer.size(), tiles_w, tiles_h);
+  
+  // Count non-empty tiles
+  int non_empty = 0;
+  std::set<uint16_t> unique_tiles;
+  for (auto word : tile_buffer) {
+    if (word != 0xFFFF && word != 0) {
+      non_empty++;
+      unique_tiles.insert(word);
+    }
+  }
+  
+  ImGui::Text("Non-empty tiles: %d / %zu", non_empty, tile_buffer.size());
+  ImGui::Text("Unique tile words: %zu", unique_tiles.size());
+  
+  // Sample tiles
+  ImGui::Separator();
+  ImGui::Text("First 20 tiles:");
+  
+  static int selected_tile = -1;
+  for (int i = 0; i < std::min<int>(20, tile_buffer.size()); i++) {
+    uint16_t word = tile_buffer[i];
+    auto tile = gfx::WordToTileInfo(word);
+    
+    bool is_selected = (selected_tile == i);
+    if (ImGui::Selectable(absl::StrFormat("[%d] Word:0x%04X ID:%d Pal:%d H:%d V:%d P:%d",
+                                          i, word, tile.id_, tile.palette_,
+                                          tile.horizontal_mirror_, tile.vertical_mirror_,
+                                          tile.over_).c_str(),
+                          is_selected)) {
+      selected_tile = i;
+    }
+  }
+  
+  if (selected_tile >= 0 && selected_tile < tile_buffer.size()) {
+    ImGui::Separator();
+    ImGui::Text("Selected Tile %d:", selected_tile);
+    uint16_t word = tile_buffer[selected_tile];
+    auto tile = gfx::WordToTileInfo(word);
+    
+    ImGui::BulletText("Word: 0x%04X", word);
+    ImGui::BulletText("Tile ID: 0x%03X (%d)", tile.id_, tile.id_);
+    ImGui::BulletText("Palette: %d", tile.palette_);
+    ImGui::BulletText("H-Mirror: %d, V-Mirror: %d", 
+                      tile.horizontal_mirror_, tile.vertical_mirror_);
+    ImGui::BulletText("Priority: %d", tile.over_);
+    
+    // Calculate palette color range for this tile
+    int pal_start = tile.palette_ * 16;
+    int pal_end = pal_start + 15;
+    ImGui::BulletText("Palette range: colors %d-%d", pal_start, pal_end);
+    
+    if (pal_end >= palette.size()) {
+      ImGui::TextColored(ImVec4(1, 0, 0, 1), 
+                         "WARNING: Palette range exceeds palette size (%zu)!", 
+                         palette.size());
+    }
+  }
+}
+
+void RoomVisualDiagnostic::DrawPixelInspector(const gfx::Bitmap& bitmap, 
+                                               const gfx::SnesPalette& palette) {
+  if (!bitmap.is_active() || bitmap.vector().empty()) {
+    ImGui::TextColored(ImVec4(1, 0, 0, 1), "Bitmap not active or empty");
+    return;
+  }
+  
+  const auto& pixels = bitmap.vector();
+  
+  // Analyze pixels
+  std::map<uint8_t, int> color_histogram;
+  for (size_t i = 0; i < std::min<size_t>(1000, pixels.size()); i++) {
+    color_histogram[pixels[i]]++;
+  }
+  
+  ImGui::Text("Pixel analysis (first 1000 pixels):");
+  ImGui::Text("Unique colors: %zu", color_histogram.size());
+  
+  ImGui::Separator();
+  ImGui::Text("Color distribution:");
+  
+  // Show top 10 most common colors
+  std::vector<std::pair<uint8_t, int>> sorted_colors(color_histogram.begin(), color_histogram.end());
+  std::sort(sorted_colors.begin(), sorted_colors.end(), 
+            [](const auto& a, const auto& b) { return a.second > b.second; });
+  
+  for (size_t i = 0; i < std::min<size_t>(10, sorted_colors.size()); i++) {
+    uint8_t idx = sorted_colors[i].first;
+    int count = sorted_colors[i].second;
+    
+    ImGui::Text("[%3d] Count: %4d (%.1f%%)", idx, count, (count * 100.0f) / 1000.0f);
+    
+    if (idx < palette.size()) {
+      ImGui::SameLine();
+      auto color = palette[idx];
+      auto rgb = color.rgb();
+      ImVec4 imcolor(rgb.x, rgb.y, rgb.z, 1.0f);
+      ImGui::ColorButton("##pal", imcolor, ImGuiColorEditFlags_NoAlpha, ImVec2(16, 16));
+      
+      if (ImGui::IsItemHovered()) {
+        ImGui::SetTooltip("SNES:0x%04X RGB:(%.0f,%.0f,%.0f)", 
+                          color.snes(), rgb.x * 255, rgb.y * 255, rgb.z * 255);
+      }
+    } else {
+      ImGui::SameLine();
+      ImGui::TextColored(ImVec4(1, 0, 0, 1), "OUT OF RANGE!");
+    }
+  }
+  
+  // Interactive pixel inspector
+  ImGui::Separator();
+  static int inspect_x = 0;
+  static int inspect_y = 0;
+  
+  ImGui::Text("Pixel Inspector:");
+  ImGui::SliderInt("X", &inspect_x, 0, bitmap.width() - 1);
+  ImGui::SliderInt("Y", &inspect_y, 0, bitmap.height() - 1);
+  
+  int pixel_idx = inspect_y * bitmap.width() + inspect_x;
+  if (pixel_idx >= 0 && pixel_idx < pixels.size()) {
+    uint8_t pal_idx = pixels[pixel_idx];
+    ImGui::Text("Pixel (%d, %d) = Palette Index %d", inspect_x, inspect_y, pal_idx);
+    
+    if (pal_idx < palette.size()) {
+      auto color = palette[pal_idx];
+      auto rgb = color.rgb();
+      ImVec4 imcolor(rgb.x, rgb.y, rgb.z, 1.0f);
+      ImGui::ColorButton("##pixel_color", imcolor, ImGuiColorEditFlags_NoAlpha, ImVec2(40, 40));
+      ImGui::SameLine();
+      ImGui::Text("SNES:0x%04X RGB:(%.0f,%.0f,%.0f)", 
+                  color.snes(), rgb.x * 255, rgb.y * 255, rgb.z * 255);
+    } else {
+      ImGui::TextColored(ImVec4(1, 0, 0, 1), "Palette index %d out of range (max: %zu)!", 
+                         pal_idx, palette.size() - 1);
+    }
+  }
+}
+
+void RoomVisualDiagnostic::DrawTileDecoder(const std::vector<uint8_t>& gfx16_data, int tile_id) {
+  if (gfx16_data.empty()) {
+    ImGui::TextColored(ImVec4(1, 0, 0, 1), "No graphics data");
+    return;
+  }
+  
+  // Calculate tile offset in graphics data
+  int tx = (tile_id / 16 * 512) + ((tile_id & 0xF) * 4);
+  
+  ImGui::Text("Decoding tile 0x%03X", tile_id);
+  ImGui::Text("Offset in gfx16_data: 0x%X (%d)", tx, tx);
+  
+  if (tx < 0 || tx + 32 > gfx16_data.size()) {
+    ImGui::TextColored(ImVec4(1, 0, 0, 1), "Tile offset out of range!");
+    return;
+  }
+  
+  // Show raw tile data
+  ImGui::Text("Raw 4bpp data (32 bytes):");
+  for (int i = 0; i < 32; i += 8) {
+    ImGui::Text("%02X %02X %02X %02X %02X %02X %02X %02X",
+                gfx16_data[tx + i], gfx16_data[tx + i + 1],
+                gfx16_data[tx + i + 2], gfx16_data[tx + i + 3],
+                gfx16_data[tx + i + 4], gfx16_data[tx + i + 5],
+                gfx16_data[tx + i + 6], gfx16_data[tx + i + 7]);
+  }
+  
+  // Decode and visualize 8x8 tile
+  ImGui::Separator();
+  ImGui::Text("Decoded 8x8 pixel values (palette 0):");
+  
+  // Decode the tile manually to show what pixels are produced
+  for (int y = 0; y < 8; y++) {
+    std::string line;
+    for (int x = 0; x < 8; x++) {
+      int yl = (y / 8) * 64 + (y % 8) * 8;
+      int xl = x / 2;
+      
+      if (tx + yl + xl < gfx16_data.size()) {
+        uint8_t pixel_byte = gfx16_data[tx + yl + xl];
+        uint8_t pixel_val = (x % 2 == 0) ? (pixel_byte >> 4) : (pixel_byte & 0x0F);
+        line += absl::StrFormat("%X", pixel_val);
+      } else {
+        line += "?";
+      }
+    }
+    ImGui::Text("%s", line.c_str());
+  }
+}
+
+}  // namespace dungeon
+}  // namespace zelda3
+}  // namespace yaze
+
diff --git a/src/app/zelda3/dungeon/room_visual_diagnostic.h b/src/app/zelda3/dungeon/room_visual_diagnostic.h
new file mode 100644
index 00000000..114f4bac
--- /dev/null
+++ b/src/app/zelda3/dungeon/room_visual_diagnostic.h
@@ -0,0 +1,52 @@
+#ifndef YAZE_APP_ZELDA3_DUNGEON_ROOM_VISUAL_DIAGNOSTIC_H
+#define YAZE_APP_ZELDA3_DUNGEON_ROOM_VISUAL_DIAGNOSTIC_H
+
+#include "imgui/imgui.h"
+#include "app/gfx/bitmap.h"
+#include "app/gfx/snes_palette.h"
+#include "app/gfx/background_buffer.h"
+
+namespace yaze {
+namespace zelda3 {
+namespace dungeon {
+
+/**
+ * @brief Visual diagnostic tool for dungeon rendering using ImGui
+ * 
+ * Provides interactive visualization of:
+ * - Texture previews (BG1, BG2)
+ * - Bitmap data with zoom
+ * - Tile buffer contents
+ * - Palette colors
+ * - Pixel value inspection
+ */
+class RoomVisualDiagnostic {
+ public:
+  /**
+   * @brief Draw the diagnostic window
+   * @param bg1_buffer Background 1 buffer reference
+   * @param bg2_buffer Background 2 buffer reference  
+   * @param palette Current palette being used
+   * @param gfx16_data Graphics data buffer
+   */
+  static void DrawDiagnosticWindow(
+      bool* p_open,
+      gfx::BackgroundBuffer& bg1_buffer,
+      gfx::BackgroundBuffer& bg2_buffer,
+      const gfx::SnesPalette& palette,
+      const std::vector<uint8_t>& gfx16_data);
+
+ private:
+  static void DrawTexturePreview(const gfx::Bitmap& bitmap, const char* label);
+  static void DrawPaletteInspector(const gfx::SnesPalette& palette);
+  static void DrawTileBufferInspector(gfx::BackgroundBuffer& buffer, const gfx::SnesPalette& palette);
+  static void DrawPixelInspector(const gfx::Bitmap& bitmap, const gfx::SnesPalette& palette);
+  static void DrawTileDecoder(const std::vector<uint8_t>& gfx16_data, int tile_id);
+};
+
+}  // namespace dungeon
+}  // namespace zelda3
+}  // namespace yaze
+
+#endif  // YAZE_APP_ZELDA3_DUNGEON_ROOM_VISUAL_DIAGNOSTIC_H
+
diff --git a/src/app/zelda3/zelda3.cmake b/src/app/zelda3/zelda3.cmake
index 4d07bb91..a0581d8d 100644
--- a/src/app/zelda3/zelda3.cmake
+++ b/src/app/zelda3/zelda3.cmake
@@ -16,6 +16,7 @@ set(
   app/zelda3/dungeon/object_renderer.cc
   app/zelda3/dungeon/room_layout.cc
   app/zelda3/dungeon/room_diagnostic.cc
+  app/zelda3/dungeon/room_visual_diagnostic.cc
   app/zelda3/dungeon/dungeon_editor_system.cc
   app/zelda3/dungeon/dungeon_object_editor.cc
 )
\ No newline at end of file