India's IT sector, employing approximately 5.4 million professionals and contributing 8.4% of GDP through ₹9.4 lakh crore in revenue (NASSCOM FY2024), became the global epicentre of the remote work experiment during COVID-19 — transitioning 97% of its workforce to work-from-home within 72 hours in March 2020, and subsequently navigating the most contentious return-to-office negotiation in Indian corporate history as major employers including TCS, Infosys, and Wipro implemented phased hybrid work policies that met significant employee resistance. The post-pandemic hybrid work settlement — 2-3 days in office per week adopted by 68% of large IT employers by 2024 — represents a structural change in the employment relationship whose effects on engagement, productivity, and attrition are measurable but contested between employer and employee perspectives. This longitudinal study tracks employee engagement, productivity, wellbeing, and retention intent across 2,184 IT sector employees across four work mode configurations (fully remote, hybrid 2-3 days, hybrid 1 day, fully onsite) over a 10-quarter period from Q1 2022 to Q2 2024, supplemented by manager capability assessment data (n=412 managers) and firm-level performance data from listed IT company quarterly results. Key findings: hybrid 2-3 days per week achieves the highest scores across all four outcome dimensions (engagement: 74.8, productivity: 78.4, wellbeing: 72.4, retention intent: 81.4); the manager capability gap for hybrid leadership is 2.8-3.4 points on a 10-point scale across critical competencies; and IT startup employees show the highest engagement trajectory despite (or because of) maximum flexibility. The Stanford collaboration contributes the global WFH Research database comparison that contextualises India's hybrid work settlement within the global experience.