Despite documented best practices and specialized tools, managers continue to face major challenges in software development. While managers are traditionally advised to choose between plan-driven and agile principles, software organizations increasingly face situations in which they need to take advantage of both. There is, however, limited actionable advice on how managers can shape the organizational context to develop such capability. We therefore combine theory on ambidexterity and contextualist inquiry to report from a two-year action research study at TelSoft. As a result, we propose a model for how software organizations can become ambidextrous through the processes of diagnosing, visioning, intervening, and practicing and discuss the implications for research and practice into software management.