A founder's postmortem argues plan mode is the wrong abstraction now that agents interleave planning and building

Sources: primary, discussion
Summary: The post, dated 2026-09-24, reports that a generated specification added length without adding clarity, and that forcing a user to finish thinking before building blocked the loop the product depended on. The author concludes that a separate plan mode is the wrong abstraction once an agent can interleave planning and building.
Why it matters: Anyone adding a plan step to an agent workflow gets a dated first-hand account of that step failing in a shipped product rather than an argument from principle.