diff --git a/engine/compile_m.py b/engine/compile_m.py
index b35e38c..66b4ac7 100644
--- a/engine/compile_m.py
+++ b/engine/compile_m.py
@@ -32,6 +32,8 @@ from test_m import pack_layer, defines
 EXACT = os.environ.get('M_EXACT') == '1'
 FAST = [] if EXACT or '-DM_RELAXED' in os.environ.get('M_DEFS', '').split() else ['-DM_RELAXED']
 FAST_WPW = [] if EXACT or os.environ.get('M_WPW') or 'WPW=' in os.environ.get('M_DEFS', '') else ['-DWPW=2']
+# preset L's expansion stage (dec0l) two windows per wave as well; its input stage (enc0l) is slower that way
+L_WPW = [] if EXACT or 'WPW=' in os.environ.get('M_DEFS', '') + os.environ.get('M_DEFS_DEC0L', '') else ['-DWPW=2']
 SHADERS = {'enc1': 'm_enc1', 'enc2': 'm_enc2', 'enc3_tube': 'm_tube', 'dec2': 'm_dec2', 'dec1': 'm_dec1'}
 
 
@@ -159,7 +161,7 @@ def compile_l(a, one, R):
     for name, out in SHADERS.items(): glsl('layer_m.comp', out + '.spv', defines(name) + ['-DTEXL=1'] + FAST + FAST_WPW)
     for planes, suffix in ((0, ''), (1, '_planes')):
         glsl('layer_m.comp', f'enc0_l{suffix}.spv', defines('enc0l') + ldr + [f'-DPLANES={planes}'] + FAST)
-        glsl('layer_m.comp', f'dec0_l{suffix}.spv', defines('dec0l') + [f'-DPLANES={planes}'] + FAST)
+        glsl('layer_m.comp', f'dec0_l{suffix}.spv', defines('dec0l') + [f'-DPLANES={planes}'] + FAST + L_WPW)
     # the reconstruction one render texel wider per tier than M's (4x4 taps): 11 (reconstruction/render >= 3),
     # 16 (the whole post_3_2 range), 12 (the compact tier: render/reconstruction <= 0.45, jitter within half a texel)
     for out, tile in (('post_l', 11), ('post_l_q', 16), ('post_l_c', 12)):
diff --git a/engine/layer_m.comp b/engine/layer_m.comp
index 36bd42c..84e673c 100644
--- a/engine/layer_m.comp
+++ b/engine/layer_m.comp
@@ -64,8 +64,8 @@
 #ifndef WPW
 #define WPW 1
 #endif
-#if WPW > 1 && KIND >= 3
-#error layer_m.comp: L's input and expansion stages stage their pixels per thread (WPW = 1)
+#if WPW > 2 && KIND >= 3
+#error layer_m.comp: L's input and expansion stages handle their 64 pixels one per invocation (WPW <= 2)
 #endif
 layout(local_size_x = 128 / WPW) in;
 // o: 0 g1, 1 bo, 2 g2, 3 b2 (f16); per head h at 4 + 4h: q, v (FP8), bias (f16), wo (FP8);
@@ -496,8 +496,7 @@ void main()
 #endif
 #if KIND == 3
     // ------------------------------------------------------------ L's input: features, embedding -> x0
-    FORW {
-        WINV
+    {
         const float e1 = ep.expo == 0.0 ? 1.0 : ep.expo, e2 = ep.expoPrev == 0.0 ? 1.0 : ep.expoPrev;
         const uint li = gl_LocalInvocationID.x;
         if (li < 64u)
@@ -510,7 +509,10 @@ void main()
             const uint at = (((py >> 2) * 2u + (px >> 2)) * 16u + (py & 3u) * 4u + (px & 3u)) * FS;
             for (uint k = 0u; k < 32u; ++k) FEW[at + k] = fe[k];
         }
-        SYNC
+    }
+    SYNC
+    FORW {
+        WINV
         // the embedding has the shape of an MLP chunk: 32 features -> 32 hidden (ReLU, FP8) -> C
         B8 f0, f1;
         coopMatLoad(f0, FEW, mt * 16u * FS, FS, CM);
@@ -532,8 +534,8 @@ void main()
         for (int i = 0; i < 8; ++i) X0S[xb + 16u * (N) + uint(i)] = float16_t(x_[i]); }
         EACH_T(EMB_N)
 #undef EMB_N
-        SYNC
     }
+    SYNC
 #endif
     // ------------------------------------------------------------ norm 1: sum of squares, residual and h1
     FORW {
@@ -768,7 +770,9 @@ void main()
         const uint hb = (mt * 16u + row) * HS + ch8;
         for (uint nt = 0u; nt < NT; ++nt)
             for (int i = 0; i < 8; ++i) HO[hb + 16u * nt + uint(i)] = float16_t(res[nt][i]);
-        SYNC
+    }
+    SYNC
+    {
         const uint li = gl_LocalInvocationID.x;
         const uint px = li & 7u, py = li >> 3;
         const ivec2 at = ivec2(X0 + int(px), Y0 + int(py));
diff --git a/engine/test_m.py b/engine/test_m.py
index 257e4c0..ffa273e 100644
--- a/engine/test_m.py
+++ b/engine/test_m.py
@@ -90,7 +90,7 @@ def defines(name):
     # compile_m.py's arithmetic (ZLUDA's lowering); M_TEXL=0 gives the native accuracy kernels' for the network layers.
     # M_DEFS: extra defines for every layer_m.comp stage; M_DEFS_ENC1, M_DEFS_ENC3_TUBE, ...: for one layer
     texl = ['-DTEXL=1'] if kind >= 3 or os.environ.get('M_TEXL', '1') != '0' else []
-    # M_WPW=2: two 4x4-token windows per wave in the network layers (layer_m.comp WPW; not L's input / expansion)
+    # M_WPW=2: two 4x4-token windows per wave in the network layers (layer_m.comp WPW; L's input / expansion: M_DEFS_*)
     wpw = [f"-DWPW={os.environ['M_WPW']}"] if kind < 3 and os.environ.get('M_WPW') else []
     return [f'-DC={C}', f'-DNH={heads}', f'-DKIND={kind}', f'-DXC={NPM or CIN or 16}'] + texl + wpw + os.environ.get('M_DEFS', '').split() + os.environ.get('M_DEFS_' + name.upper(), '').split()