HOW CURSOR SHIPPED ITS CODING AGENT TO PRODUCTION

Summary from the TLDR Dev newsletter

Cursor's team shipped Composer, a coding agent that completes most tasks in under 30 seconds, by solving three gnarly engineering problems: the “diff problem” (models aren't great at making clean code edits, so they trained specifically on edit trajectories and search-replace operations), compounded latency (each step in the agent loop adds delay, so they used MoE architecture, speculative decoding with draft models, and aggressive context compaction to stay fast), and sandboxing at scale (they built custom VM infrastructure to spin up thousands of isolated execution environments without the startup time becoming a bottleneck).