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Résumé : We constrained the activity geometry of the interstellar comet 3I/ATLAS by combining high-resolution Hubble Space Telescope imaging with multi-epoch Zwicky Transient Facility observations and forward dust-dynamical modeling. The isotropic models explored here failed to reproduce the observed sunward structure, which was better matched by anisotropic emission from a rotating nucleus. Under the adopted prograde interpretation, the preferred solution has a high-obliquity spin state, with I ≃ 85° and Φ ≃ 15°, and an active source region concentrated at high southern latitudes, approximately between −90° and −45°. The position-angle modulation of the narrow sunward jet provides an additional sky-plane constraint and is consistent with a near-polar source at λ jet ≃ −84°. The preferred model is consistent with sustained dust activity beginning in late January 2025 and the modeled dust-production rate increases from approximately 20 kg s −1 on 2025 July 21 to about 50 kg s −1 by 2025 August 21. The grain-size distribution evolves with time, with the maximum grain radius increasing from approximately 1 to 5 mm and the power-law index from about 3.3 to 3.6. The inferred spin geometry predicts a seasonal transition across perihelion. The southern source is favored during the inbound phase and becomes less illuminated as the subsolar latitude migrates northward. This provides a possible explanation for the pre-perihelion sunward jet and its subsequent weakening.