Gaia Coherent Kinematics Survey (GCKS): A Blind Search for Unexplained Coherent Kinematic Structures within 300 pc — Frozen Pre-Registration Specification v1.0

This is a pre-registration. No candidate scan has been executed at time of depositThis document freezes, in advance of any candidate analysis, the complete analysis plan for the Gaia Coherent Kinematics Survey (GCKS): a blind search of the 6-D Gaia DR3 sample within 300 pc of the Sun for spatially coherent groups of stars whose velocity residuals share a common pattern not attributable to measurement error, instrumental systematics, or ordinary astrophysical populations. The survey computes a multiscale local velocity field, forms measurement-error-aware residuals δv, gates stars on a frozen Mahalanobis criterion, and clusters survivors at fixed spatial scales. Significance is assessed against a graded null hierarchy in which a permutation test (N0) is treated only as a structural control and is explicitly not presented as a Galactic-dynamics null; matched Gaia control volumes, an empirical kinematic mixture, and binary/systematics controls follow. Known streams associations, and moving groups are not removed prior to detection, so their recovery functions as a positive control on the pipeline. Detectability is calibrated by injection–recovery over (Δv, R, N, t) before the real scan, yielding a sensitivity envelope; a null result therefore produces quantitative exclusion limits rather than an absence of information. No causal or technological interpretation forms any part of the detection criterion. Surviving structures are reported as unexplained coherent kinematic structures and nothing further until ordinaryexplanations are exhausted.