The combination of Textile-Reinforced Concrete (TRC) and Ultra-High Performance Concrete (UHPC) enables the creation of lightweight and durable thin-walled structural elements. While the flexural behavior of TRC I-beams has been the focus of several studies, their load-bearing capacity is often governed by a premature failure at the web-flange junction. With the shear behavior of such I-section beams remaining less understood, this study presents an experimental investigation of different web-flange connection details to evaluate their effect on structural performance. The methodology is based on a multi-scale experimental program. A pull-out test, designed to represent the web-flange junction, is used to characterize the local behavior of the connection details. Subsequently, full-scale Carbon Textile-Reinforced UHPC (CTR-UHPC) I-beams featuring distinct anchorage strategies are tested under a shear-critical three-point bending configuration. The results demonstrate a clear correlation between the junction's anchorage detail and the overall shear capacity of the beams. An improved connection detail mitigated the abrupt debonding failure, leading to an increase in both load-bearing capacity and deformation capability. The incorporation of short PVA fibers also provided post-cracking residual strength. This study concludes that the shear performance of CTR-UHPC I-beams is directly governed by the detailing of the web-flange connection. The experimental data presented serves as a valuable reference for the future development and validation of analytical models.