One page from Andrej Karpathy quietly turns REA + Opus 5.5 + Obsidian into an agent that clones any $1M+ SaaS in a weekend
it reads the system, explains how every part works, and rebuilds your own version from open tools, 70% cheaper and 4x faster
save this before it gets taken down
the usual objection to letting an agent work while you work is that it is in your files
in grok build it does not have to be
subagents run in parallel, each with its own context window,
and they can be launched in their own worktree
so the branch you are sitting on is untouched while something else is being tried in a separate checkout
you get the result handed back, not a surprise in your diff
and when you want the fan out shaped rather than ad hoc,
slash create workflow writes one, it asks about fan out,
verification and scope, then saves the file as a rhai script in the project
after that it runs by name, with arguments,
and you can pause it, resume it, or stop it mid run
parallel work was never the risky part
sharing one checkout was