How Software Development Changed

A plain account of what actually shifted in how software gets built, for people who write code or manage people who do. Where the bottleneck moved, why plausible-but-wrong code is a new kind of failure, how review and testing have to change, why specifications got more valuable, and which parts of the job got harder rather than easier. Vendor-neutral, with the contested parts marked as contested.

1. 1The cost curve moved, but only part of it8 minGenerating code got cheap; deciding what to build and confirming it is right did not.
2. 2Reviewing code you did not write9 minYou own every line you submit, whoever typed it; if you cannot explain it in review, it is not ready.
3. 3The new failure mode: plausible and wrong9 minCode that looks right is no longer evidence that it is right; polish and correctness came apart.
4. 4Testing when generating is free9 minA test only counts if you have seen it fail for the right reason.
5. 5Why writing it down matters more now8 minAmbiguity used to stop you while typing; now it gets resolved for you, silently, in some direction.
6. 6Pairing with a model on real work10 minWork in steps you can run and throw away; speed only helps when reversing it is cheap.
7. 7Juniors, and the rung that went missing9 minThe work that used to make people senior is the work that got cheapest, so the rung has to be rebuilt on purpose.
8. 8The parts that got harder10 minMore code with unchanged verification capacity is not more throughput; it is a growing queue.