Multi-Probe Cosmological Constraints on Clustering DBI Dark Energy Scenario

We present a multi-probe observational analysis of a clustering tachyonic Dirac-Born-Infeld~(DBI) dark energy model. Its noncanonical kinetic term gives a subluminal sound speed, so dark energy perturbations can grow on subhorizon scales. Working in a multifluid framework that tracks both the background expansion and linear perturbations, we constrain the model with nested sampling, using Planck 2018 compressed CMB distance priors, DESI DR2 BAO, cosmic chronometers, fσ₈ growth data, and three Type Ia supernova compilations: Pantheon$+$, DES-SN5YR, and Union3. The standard cosmological parameters agree with $Λ$CDM within $2σ$, with DBI preferring a slightly lower H₀ and higher Ωₘ₀, with the largest shift being 1.8σ in H₀ for Pantheon$+$. The Bayesian evidence favours DBI in every compilation, moderately for Pantheon$+$ (Δ3.4) and inconclusively for DES-SN5YR and Union3 (Δ0.6-$0.7$). The field thaws naturally. Dark energy perturbations stay several orders of magnitude below matter perturbations, yet the noncanonical sound speed still alters the Hubble friction term, raising S₈ by only ≈0.5σ relative to $Λ$CDM. Four independent diagnostics, namely the CPL parametrization, $Om(z)$, the statefinder hierarchy, and the growth index, all point to genuinely evolving dark energy rather than a cosmological constant. The thermal history is left intact, with negligible early dark energy. However, one limitation remains. Because w_ϕ=ϕ²-1≥-1, the phantom regime is out of reach, which is in line with the no-go theorem for a single minimally coupled scalar field, so the model cannot follow the DESI DR2 preference for an effective equation of state crossing $w=-1$.