Chiral metasurfaces supported by symmetry-protected bound states in the continuum (SP-BICs) possess exceptional capabilities for confining light fields and enhancing light-matter interactions. However, a fundamental trade-off persists in chiral metasurfaces: systematically achieving both ultrahigh-$Q$ resonances and maximum circular dichroism (CD). Here, we propose a robust strategy for chiral quasi-BIC metasurfaces, where perturbations are introduced to the symmetric eigenfield, enabling the systematic realization of ultrahigh $Q$-factors and near-unity CD. We demonstrate that the two holes within the nanodisks, acting as perturbations, whose position dominates the $Q$-factors, provide sufficient chiral degrees of freedom to tailor the C points along the $k_x$ and $k_y$ directions in momentum space. When the chiral perturbations are located at the eigenfield minima, this enables the achievement of $Q\approx 1.879\times {10}^5$ and CD = 0.99. This method enables the reconfiguration of C points from arbitrary initial positions and is broadly applicable to various eigenmodes, providing a systematic and robust framework for high-performance chiral optoelectronic and photonic devices.

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• Bound states in the continuum
• Chirality
• Metasurfaces