The 28th International Conference on Human-Computer Interaction, HCI International 2026 (HCII 2026), took place in Montreal, QC, Canada, during July 2026. A total of 7435 individuals from academia, research institutes, industry, and government agencies from 94 countries submitted contributions to HCII 2026. Following peer review, 1463 papers and 360 posters (as short research papers) are included in the volumes of the HCII 2026 proceedings published just before the start of the conference. Six volumes (CCIS 3047 – 3052) of the HCII 2026 proceedings are dedicated to this year’s poster extended abstracts, in the form of short research papers, focusing on the following topics: Volume I: HCI Theory and Foundations; Visual Perception and User Interface Design; UX Evaluation, Metrics, and Research Methods; Accessibility and Inclusive Design Volume II: Immersive XR and Virtual Experience Design; XR for Learning and Training; Games, Gamification, and Playful Interaction; Cultural Heritage and Interactive Narrative Experiences Volume III: Social Robots, Service Robots, and Human–Robot Interaction; Automated Driving, Vehicle HMI, and Driver Experience; Mobility, Aviation, and Transportation Platforms; Product, Service, and Experience Design; Fashion, Architecture, and Interior Design; Haptics, Biometrics, and Advanced Interaction Modalities Volume IV: Social Robots, Service Robots, and Human–Robot Interaction; Automated Driving, Vehicle HMI, and Driver Experience; Mobility, Aviation, and Transportation Platforms; Product, Service, and Experience Design; Fashion, Architecture, and Interior Design; Haptics, Biometrics, and Advanced Interaction Modalities Volume V: Social Robots, Service Robots, and Human–Robot Interaction; Automated Driving, Vehicle HMI, and Driver Experience; Mobility, Aviation, and Transportation Platforms; Product, Service, and Experience Design; Fashion, Architecture, and Interior Design; Haptics, Biometrics, and Advanced Interaction Modalities Volume VI: Education, Learning Systems, and Pedagogical Innovation; Clinical Decision Support and Medical Interfaces; Patient Experience and Health Service Design; Aging, Independent Living, and Age-friendly Interaction; Well-Being, Emotional Support, and Everyday Care Technologies