Shape Up
Shape Up is Basecamp's product-development methodology (Ryan Singer, 2019). The cycle has three phases: shaping (a senior PM scopes a 6-week project with hard boundaries, what's in, what's out, sketches); betting (a small group commits to the next cycle's projects); building (chosen teams execute autonomously with hill charts replacing burndown).
Shape Up's strongest commitments are its hardest sells: fixed time, variable scope (the 6 weeks is non-negotiable; the team cuts scope to fit); no backlog (stale work doesn't get re-bet); explicit cool-down between cycles (2 weeks of unstructured work). It's not a replacement for Scrum at most companies. It's a different model that works well in product organisations with stable teams and clear product authority. Companies that have adopted Shape Up beyond Basecamp report success in specific cultures (autonomous senior teams, product-led decision-making) and failure in others (large consensus-driven orgs, regulated industries). Worth studying even where you don't adopt it.