The number one power move I have is Nix integration. The availability of tooling, secrets, environment and the ability for the agent to modify its own environment is... well, I don't know how people live without it. I guess you guys still install things using commands and hope everything you need is present on the next machine? Developer machine, CI environment, deployment environment: They're all derived from a single source, and compiling and running always works on every machine.

In Claude I use /branch and /rename a lot (context checkpoints, fork, go back)

I use sandboxing almost exclusively: https://github.com/nix-tools/bubblebox -- it's a generalisation of Numtide's claudebox with a few fixes and some feature additions (more coming). This is best compared to always running your Claude in Docker containers, except there's no Docker runtime. Works fine in WSL and nix-darwin, too.