Performance of the COCA framework when applied outside the range of the training data. We compare the power spectrum (top row) and cross-correlation coefficient (bottom row) of the matter density field (left column) and velocity potential (right column) when using our emulator with a different set of cosmological parameters than it was trained on. The coloured lines show the mean across 50 test simulations as a function of the number of force evaluations, n_f. The grey band indicates 99% agreement. In this test of robustness to cosmological parameter mis-specification, only eight force evaluations are required to correct the emulation error up to k ≳ 0.6 h Mpc⁻¹.