Observational phase-coherent multipole-space residual oscillations in Planck, ACT, and SPT band power

We report evidence for a common oscillatory residual in CMB temperature and polarization bandpowers from public Planck-lite, ACT DR6, and SPT-3G D1 data. Motivated partly by a reported supernova Hubble-diagram residual oscillation, we test the compressed CMB residuals directly with native or compressed covariance matrices. The strongest all-spectrum phase coherence occurs near P₌, where the maximum Planck--ACT--SPT phase separations are 0.011, 0.020, and 0.118 cycles in EE, TE, and TT. A 10⁶-realization random-phase calculation gives pfixed= and a look-elsewhere-corrected pglobal=; a stricter componentwise diagnostic gives pglobal=. We additionally impose one common phase across the three experiments, retaining experiment-dependent amplitudes and offsets. Exact common phase is acceptable for EE and TE, with Δχ²=1.30 and 3.08 for two constraints, but not for TT, where Δχ²=86.74. Ten thousand native-covariance parametric mocks validate the nominal χ²₂ calibration. Thus TT is broadly aligned within 0.118 cycle but not exactly phase-equal, while the strongest exact coherence occurs in polarization. The result motivates a full likelihood-level investigation.