diff --git a/public/js/render/board3d/materials.js b/public/js/render/board3d/materials.js
index d986c485..b122bebf 100644
--- a/public/js/render/board3d/materials.js
+++ b/public/js/render/board3d/materials.js
@@ -1,8 +1,8 @@
 // render/board3d/materials.js — three.js materials of the official board scene (DESIGN §15). THREE is injected
 // (the renderer loads /vendor/three.module.js; Node tests pass the npm package).
 //
-//   MT_autochess        → MeshStandardMaterial: albedo TX_autochessi_D (sRGB), normal TX_autochessi_N (BC5 → RGB,
-//                         tools/local-extract DERIVED), roughness 1 − smoothness of TX_autochessi_M (DERIVED), metal 0,
+//   MT_autochess        → MeshStandardMaterial: albedo TX_autochessi_D (sRGB), normal TX_autochessi_N (BC5 / DXT5nm →
+//                         RGB, tools/local-extract DERIVED), roughness 1 − smoothness of TX_autochessi_M (DERIVED), metal 0,
 //                         emission TX_autochessi_E (_EmissionColor white), vertex colours = baked AO / tints
 //   MT_autochess_common → device plates of TX_autochessi_common_D, alpha test 0.408, emission _E × 0.559
 //   MT_autochessi_BG    → unlit TX_autochessi_BG × 0.713 (Torappu/Unlit/Texture, _Color)
diff --git a/test/render/board3d-extract.test.js b/test/render/board3d-extract.test.js
index 864a7a08..5df1d688 100644
--- a/test/render/board3d-extract.test.js
+++ b/test/render/board3d-extract.test.js
@@ -1,6 +1,6 @@
 // test/render/board3d-extract.test.js — the local-client exports behind the official 3D board (DESIGN §13/§15):
 // tools/local-extract/extract.py's board jobs (gate / objective effects, blower texture, water & noise maps), the
-// derived three.js maps (BC5 normal → RGB normal, Unity metallic/gloss → roughness), the WebP copies of the textures
+// derived three.js maps (BC5 / DXT5nm normal → RGB normal, Unity metallic/gloss → roughness), the WebP copies of the textures
 // the renderer downloads (extract.py WEBP), the prefab mesh keys, and —
 // when a client was extracted here — the files and manifest entries the renderer loads (render/board3d/load.js).
 
@@ -65,6 +65,23 @@ print(json.dumps({'n': [list(rn.getpixel((i, 0))) for i in range(3)], 'm': [list
     assert.deepEqual(out.m, [[255, 255, 0], [255, 55, 0]]);
   });
 
+  test('derived normal map: the DXT5nm layout (R = 1, G = Y, A = X) gives the same normals as BC5 (R = X, G = Y)', { skip: !HAS_PIL && 'no Pillow' }, () => {
+    const out = py(`
+from PIL import Image
+xy = [(128, 128), (255, 128), (128, 20), (90, 200), (0, 128), (37, 37)]
+bc5 = Image.new('RGB', (len(xy), 1)); nm = Image.new('RGBA', (len(xy), 1)); opaque = Image.new('RGBA', (len(xy), 1))
+for i, (x, y) in enumerate(xy):
+    bc5.putpixel((i, 0), (x, y, 0)); nm.putpixel((i, 0), (255, y, y, x)); opaque.putpixel((i, 0), (x, y, 0, 255))
+px = lambda im: [list(im.getpixel((i, 0))) for i in range(len(xy))]
+print(json.dumps({'bc5': px(e.derive_normal_rg(bc5)), 'nm': px(e.derive_normal_rg(nm)), 'opaque': px(e.derive_normal_rg(opaque)),
+                  'mode': e.derive_normal_rg(nm).mode, 'xy': xy}))`);
+    assert.equal(out.mode, 'RGB');
+    assert.deepEqual(out.nm, out.bc5, 'X read from A when R is 1');
+    assert.deepEqual(out.opaque, out.bc5, 'a BC5 map decoded with an opaque alpha');
+    assert.deepEqual(out.nm.map((p) => p.slice(0, 2)), out.xy, 'XY kept');
+    assert.ok(out.nm[0][2] >= 254 && out.nm[3][2] > 128, 'z rebuilt, not the 128 of x = 1');
+  });
+
   test('WebP copies: exactly the board textures the renderer downloads; normal and data maps stay lossless', () => {
     const r = spawnSync(PY, [path.join(TOOL, 'extract.py'), '--print-jobs'], { encoding: 'utf8', env: ENV });
     assert.equal(r.status, 0, r.stderr);
@@ -182,7 +199,7 @@ describe('extracted board files (when a local client was extracted)', { skip: !m
     const n = decodePng(readFileSync(onDisk(pngOf(g.TX_autochessi_N_rgb.path))));
     let zSum = 0, cnt = 0;
     for (let i = 0; i < n.rgba.length; i += 4 * 97) { zSum += n.rgba[i + 2]; cnt++; }
-    assert.ok(zSum / cnt > 230, `mean z ${zSum / cnt}`);
+    assert.ok(zSum / cnt > 230, `mean z ${zSum / cnt} (128 = made by an extract.py that read a DXT5nm map as BC5: re-extract with --only map/autochess)`);
     const m = decodePng(readFileSync(onDisk(g.TX_autochessi_M.path)));
     const r = decodePng(readFileSync(onDisk(pngOf(g.TX_autochessi_M_rough.path))));
     assert.deepEqual([r.w, r.h], [m.w, m.h]);
diff --git a/tools/local-extract/extract.py b/tools/local-extract/extract.py
index f3e81105..45c607dd 100644
--- a/tools/local-extract/extract.py
+++ b/tools/local-extract/extract.py
@@ -28,9 +28,10 @@ aklz4.py registers a decoder for it. This script pulls the art the web sources l
     [opt]end_box / [opt]start_fly meshes, their merged additive textures, materials and prefab), the blower's texture
     (arts/maps/common/res.ab → map/common: TX_wind_device of the s_wind_device mesh) and the shared water / noise
     textures (arts/maps/effect.ab → map/water) used for deep-sea / mire / smog tiles
-  - derived PBR maps for three.js (DERIVED): Unity stores the theme's normal map as two channels (BC5: RG = XY, B = 0)
-    and metallic/gloss with the smoothness in A; the board renderer needs an RGB normal map (Z rebuilt) and a
-    roughness map in G (1 − smoothness; metalness B = 0), written next to the source as <name>_rgb.png / _rough.png
+  - derived PBR maps for three.js (DERIVED): Unity stores the theme's normal map as two channels (BC5: RG = XY, B = 0;
+    DXT5nm in an older bundle: AG = XY, R = 1) and metallic/gloss with the smoothness in A; the board renderer needs
+    an RGB normal map (Z rebuilt) and a roughness map in G (1 − smoothness; metalness B = 0), written next to the
+    source as <name>_rgb.png / _rough.png
   - WebP copies of the board textures every player downloads with the 3D board (WEBP), written next to their PNGs;
     the manifest lists the copy
 
@@ -148,8 +149,8 @@ TOKEN_PACKS = 'pkgrps/btl_pfb_tokens_*.ab'
 TOKEN_SPINE_SUB = 'spine/token'
 
 # Derived three.js maps: (output subdir, source texture, kind, output name). 'normal_rg' rebuilds Z of a two-channel
-# (BC5) normal map into an RGB tangent-space map; 'rough_from_gloss' turns Unity's metallic/gloss map (smoothness in
-# A) into a roughness (G) / metalness (B) map. Written after the job that exported the source texture.
+# (BC5 or DXT5nm) normal map into an RGB tangent-space map; 'rough_from_gloss' turns Unity's metallic/gloss map
+# (smoothness in A) into a roughness (G) / metalness (B) map. Written after the job that exported the source texture.
 DERIVED = [
     ('map/autochess', 'TX_autochessi_N', 'normal_rg', 'TX_autochessi_N_rgb'),
     ('map/autochess', 'TX_autochessi_M', 'rough_from_gloss', 'TX_autochessi_M_rough'),
@@ -400,13 +401,16 @@ def _normal_z_table():
 
 
 def derive_normal_rg(img):
-    """RGB tangent-space normal map from a two-channel (BC5: R = X, G = Y, B unused) one: Z rebuilt per pixel."""
-    from PIL import Image
-    rgb = img.convert('RGB')
-    r, g, _ = rgb.split()
+    """RGB tangent-space normal map from Unity's two-channel one: Z rebuilt per pixel. X and Y are read the way Unity's
+    shaders unpack them (UnityCG.cginc UnpackNormalmapRGorAG: x = R · A, y = G), which covers both layouts a client
+    build holds: BC5 (R = X, G = Y, B unused, no alpha → A = 1) and DXT5nm (R = 1, G = Y, A = X — the map_autochess
+    bundle before the client update of 2026-10)."""
+    from PIL import Image, ImageChops
+    r, g, _, a = img.convert('RGBA').split()
+    x = ImageChops.multiply(r, a)  # exact when either factor is 255
     table = _normal_z_table()
-    z = bytes(table[(x << 8) | y] for x, y in zip(r.tobytes(), g.tobytes()))
-    return Image.merge('RGB', (r, g, Image.frombytes('L', rgb.size, z)))
+    z = bytes(table[(xb << 8) | yb] for xb, yb in zip(x.tobytes(), g.tobytes()))
+    return Image.merge('RGB', (x, g, Image.frombytes('L', img.size, z)))
 
 
 def derive_rough_from_gloss(img):