Stability analysis of the TOI-2141 planetary system in the plane (P_b, e_b), assuming coplanar orbits. For fixed initial conditions, the parameter space of the system is explored by varying the orbital period and the eccentricity of planet-b. The step size is 0.005 day in the orbital period and 0.0025 in the eccentricity. For each initial condition, the system is integrated over 10⁴ yr, and a stability indicator is calculated, which involves a frequency analysis of the mean longitude of planet b. The chaotic diffusion is measured by the variation in the frequency (see text). Red points correspond to highly unstable orbits, while blue points correspond to orbits that are likely to be stable on Gyr timescales. The vertical dashed lines correspond to both 10/3 period ratios with planets c and d. The black dot shows the best fit solution from Sect. 3.4.