Validation of the forward-modelling procedure. The input model is a spherically symmetric cluster at z = 2, transformed into a 100 ks mock X-IFU observation. Top left: Surface brightness profile from the mock 0.4–1 keV image (green points and errors). The posterior mean (best-fit model) and the 68% confidence range appear as a purple solid line and dashed envelope. The sub-panel represents the difference between measurements and the best-fit model, normalised by the uncertainties. Top right: 2D temperature profile measured from X-IFU mock events using XSPEC (green points and errors). The emission-measure-weighted temperature T_EM known as input is displayed as a thick black line. The posterior mean (best-fit model) and the 68% envelope are shown in purple (solid and dashed lines, respectively). Bottom panels: Inferred electron density (left) and pressure (right) profiles are represented with the red line and dashed envelope (68% confidence level). The input profiles are in blue, and follow Eqs. 4 and 5, respectively. The two sub-panels represent the deviation of the best-fit models relative to the true input profiles. The range of fidelity of our fit is located between the PSF size (indicated with the leftmost vertical dashed line) and R₅₀₀ (rightmost line).