Trivial-nontrivial programmable topological metasurfaces for sensing and communication.

Trivial-nontrivial topological switching provides a distinctive physical pathway for multifunctional electromagnetic systems, yet has never been exploited for integrated sensing and communication (ISAC). Existing ISAC architectures rely almost exclusively on trivial spatial-wave beamforming, constraining near-field sensing robustness and limiting hardware scalability in 6 G scenarios. Here, we propose an intelligent ISAC platform enabled by a programmable topological metasurface (PTM) that dynamically switches between trivial radiation states and non-trivial valley-Hall states, which is achieved through FPGA-controlled symmetry modulation of the PTM's unit cells. In its non-trivial state, the PTM forms multiple topologically protected domain-wall channels, guiding surface waves with robustness and enabling the extraction of electromagnetic signatures for human localization. A convolutional neural network trained on these signatures achieves a localization accuracy of 99.54%. Upon position recognition, the PTM transitions to its trivial radiation phase, generating spatial phase-gradient beams for directional wireless communication without requiring additional hardware. Experimental results are consistent with theoretical predictions, validating an implementation of topological state switching for dual-mode ISAC functionality. It suggests that topological state programmability could be a potential mechanism for building compact, robust, and intelligent electromagnetic platforms for next-generation wireless systems.