High-fidelity spin readout is a crucial component for quantum information processing with optically interfaced solid-state spins. Here, we propose and investigate two theoretical protocols for fast single-shot readout of cavity-coupled single textitT center electronic spins. For fluorescence-based readout, we selectively couple one of the textitT center spin-conserving transitions to a single-mode photonic cavity, exploiting the enhancement of the fluorescence emission and cyclicity. For reflection-based readout, we leverage the spin-dependent cavity reflection contrast to generate the qubit readout signal. We show that the cavity reflection approach enables high-fidelity spin readout even when the textitT center only has a modest cyclicity. With realistic system parameters, such as cavity quality factor Q = 2×10⁵ and textitT-center optical linewidth Γ/2π = 100 MHz, we calculate a single-shot readout fidelity exceeding 99% within 10 μs for both spin readout protocols.