J. Latour, V. Christiaens, O. Absil, M. Bonse, R. Savonet, S. Juillard, I. Hammond, S. Casassus, L. Cieza, G. Cugno, C. Desgrange, S. Lacour, D. Mawet, M. Montesinos, S. Perez, C. Pinte, M. Reggiani, T. Stolker, N. van der Marel, A. Zurlo

The HD 135344B (SAO 206462) disk exhibits strong signposts of planet formation. ALMA images in the sub-mm revealed a gap-crossing dust filament whose position coincides with a twist detected in the scattered-light spiral structure. Analysis of the spirals in polarized light also hints at a spiral-driving protoplanet in the sub-mm gap. We aim to study the spirals dynamics, as well as the twist, over a 10-year baseline, in different bands. We also seek to assess the authenticity of a recently claimed candidate protoplanet. We use high-fidelity post-processing algorithms such as IPCA to minimize the biases induced by ADI on extended sources and analyze archival VLT/NACO, VLT/SPHERE, VLT/ERIS and JWST/NIRCam datasets to obtain the spiral traces and measure their orbital motion in multiple scattered light bands. We measure an average spiral orbital motion of 0.81$\pm$0.05 deg/yr, in agreement with the literature value of about 0.85$\pm$0.05 deg/yr at all wavelengths. With simple modeling of the twist morphology, we confirm that it is co-moving with the spiral in which it is embedded. While the position angle of the twist coincides with the dust filament, it is located at a smaller angular separation from the star, which we attribute to the fact that the spiral trace moves away from the central star with increasing wavelength. We find that a recently claimed protoplanet candidate can be explained as a post-processing artifact. Our confirmation that the motion of the scattered light twist is consistent with the orbital velocity of a planet at 69$\pm$4 au over a 10-year baseline suggests that the spirals, the gap, the dust filament, and the twist, could indeed be attributed to the same hypothetical protoplanet embedded within the spiral. A perplexing trend for a wavelength-dependence of the angular distance of the spiral traces to the central star remains to be explained.