Microsoft agentically ports Copilot runtime to Rust for $120K

Microsoft used AI agents to port the Copilot runtime from TypeScript to Rust in about 14.5 weeks, spending roughly $120K in tokens and a few weeks of engineer time, while achieving major gains in startup speed, throughput, and memory efficiency. For CIOs, the strategic signal is that agentic coding can materially reduce the cost and time of large-scale platform modernization, but it does not eliminate the need for experienced engineers to manage architecture, validate requirements, and catch regressions. IT organizations should view this as a model for selective modernization of high-scale services where performance and resource density matter, not as a blanket replacement for software engineering discipline.