Regionally compile the DiT blocks even when enable_cuda_graph_decode is set and let graph capture record the compiled (fused) kernels; inductor's own cudagraphs stay off so the two graph layers never nest. Measured on GB200 (1024x1024, 50 steps, seed 42, BF16): combo 3.04s vs compile-only 3.2s, graph-only 4.0s, eager 4.3s per image; 44.5-45.6 dB PSNR vs eager.