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CTO Field Notes is a collection of practical articles on the decisions behind engineering delivery: how teams use AI without giving up judgment, manage technical risk, keep software changeable, and turn uncertain plans into reliable progress.

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Evals Are the New Tests

In April 2025 OpenAI shipped a model update whose offline evals and A/B tests all looked good. It was sycophantic enough to roll back within days. A practical guide to building the measurement layer that would have caught it - with a working eval spec and grading rubric.

Code Was Never the Bottleneck

Your engineers are producing more code and your delivery cadence has barely moved. The waiting did not disappear - it moved downstream to review and absorption, and that is where the constraint always was. Includes a review-capacity audit.

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