Is the $\Lambda$CDM Model in Crisis?
We present strong evidence for dynamical dark energy that challenges the standard $\Lambda$CDM model. Several dark energy scenarios are explored, including $\omega_0\omega_a$CDM, logarithmic, exponential, JBP, and BA parameterizations, along with non-flat cosmologies allowing for spatial curvature ($\Omega_k \neq 0$). Our analysis supports a flat Universe with $\Omega_k \approx 0$. Using MCMC techniques, we constrain these models with observational data from DESI~DR2 baryon acoustic oscillations, Type~Ia supernovae, and compressed CMB likelihoods. The results provide strong statistical evidence that $\omega \neq -1$, favoring dynamical dark-energy behavior consistent with a Quintom-B scenario ($\omega_0 > -1$, $\omega_a < 0$, and $\omega_0 + \omega_a < -1$). We also derive upper bounds on the total neutrino mass, $\sum m_\nu$, using CMB + DESI~DR2 data: $\sum m_\nu < 0.066~\mathrm{eV}$ for $\Lambda$CDM and $\sum m_\nu < 0.075~\mathrm{eV}$ for $\omega$CDM. In the non-flat extensions, o$\Lambda$CDM and o$\omega$CDM, the limits relax to $\sum m_\nu < 0.263~\mathrm{eV}$ and $\sum m_\nu < 0.520~\mathrm{eV}$, respectively. For the other models $\omega_0\omega_a$CDM, logarithmic, exponential, JBP, BA, and GEDE the constraints range between $<0.043$ and $<0.127~\mathrm{eV}$. The effective number of relativistic species remains consistent with the standard value, $N_{\mathrm{eff}} = 3.044$, across all models. Bayesian evidence further shows that combining DES-SN5Y or Union3 supernova samples with CMB + DESI~DR2 produces measurable deviations from $\Lambda$CDM. Although no model reaches the $5\sigma$ significance threshold, several exhibit tensions exceeding $3\sigma$, suggesting emerging cracks in the cosmological constant paradigm.