Not a checklist, but patterns I've seen in people who made the jump:

Not a checklist, but patterns I've seen in people who made the jump: 1. They ask 'what happens when this fails?' before anyone else does. 2. Their PRs are small and their descriptions explain why, not what. 3. They unblock others without being asked. 4. They can say 'I don't know, let me find out' comfortably. 5. They think about the on-call person who'll inherit their code. Technical depth matters, but most people who get stuck at mid-level are stuck on #3 and #5.