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A FREE MCP READS 212 LEGACY FILES AND WRITES THE SPEC BEFORE ANY AGENT TOUCHES THE CODE most rewrites go wrong in the same place. you dump the whole old system into one model and it drowns this setup splits the work: OPUS 5.5 > writes the plan, then sits idle for the rest of the run REA > reverse-engineers legacy/billing once and turns it into spec.md with 14 endpoints, 37 rules, 9 edge cases SONNET 5.5 x12 > one module each, built from a ~1.5k token slice of the spec. none of them opens the old code REA VERIFY > replays the new system against the legacy one, 148 of 148 behaviours match on screen the swarm finishes in 7m 05s for $0.88. opus $0.22, REA $0.32, twelve sonnets $0.34. Opus 5.5 alone sits at 23% and $1.20, still running the video marks that comparison as illustrative, so take the numbers as a demo REA doesn't come from Anthropic. it's morluto/rea on github, MIT licensed and free, you only pay for the model. one line installs it: npx rea-agents setup before you point it at client code: > REA analyzes locally, but your agent still sends tool results to the model provider > decompiled code from a private app ends up with Anthropic or OpenAI, under their data policy it's free today. save it before someone sells it as a $500 course
