What's this about?
Thariq (Anthropic) shared a case where Claude autonomously reverse-engineered and modernized a mission-critical system from 1996 — with zero access to the original source code — as an example of what agentic coding can now do on legacy systems.
What is "reverse-engineering" software?
Reverse-engineering means figuring out how a system works from the outside — its behavior, binaries, and interfaces — when you don't have the source code or documentation. It's slow, expert human work. Getting an agent to do it, and then rebuild a modern equivalent, is a meaningful step because so much of the world runs on undocumented legacy code nobody dares touch.
Why does it matter?
"Legacy modernization" is a huge, expensive, unglamorous problem across banks, governments, and infrastructure. If agents can safely reverse-engineer and rewrite 30-year-old systems, that's one of the more concrete near-term economic uses of coding agents.