§01We interviewed thirty-six CTOs that Vertex placed across 2026 and 2026 about their first ninety days in role. The interviews were structured: each CTO was asked to walk through, week by week, what they did and what they wished they had done differently. From those transcripts, four operating patterns and four recurrent mistakes emerged.

§02Pattern one: the listening tour, but not the way it is usually run. Every CTO ran one. The successful ones did so with a deliberate structure — between forty and sixty conversations of forty minutes each, with a fixed set of seven questions. The unsuccessful ones ran an unstructured sequence of "let's grab a coffee" sessions and emerged at week six with no consolidatable findings.

§03Pattern two: a written ninety-day-plus-one document. The successful CTOs all produced a written document at week ten or eleven that was, explicitly, a ninety-day-plus-one — a statement of what they had observed in the first ninety days, and what they would do in the second ninety days. The CEOs we spoke with cited this document as the single most useful artefact of the entire onboarding.

§04Pattern three: a single, deliberate, week-eight win. The successful CTOs all engineered a small, visible, deliberately-modest win at around week eight. The point was not the win itself; the point was to demonstrate operational follow-through to the engineering organisation while the listening tour was still in progress.

§05Pattern four: refusal to restructure inside the first ninety days. Without exception, the CTOs who restructured the org chart inside the first ninety days reported regretting it. Without exception, the CTOs who restructured at month four or five reported being satisfied with the outcome. Restraint at this point appears to be a near-perfect predictor of subsequent organisational health.

§06And the four recurrent mistakes: hiring too fast, firing too slow, replacing tooling before understanding why it was chosen, and skipping the offsite that is the ninety-day-plus-one in disguise. Every one of the thirty-six CTOs we interviewed had made at least one of these four mistakes. Most had made two.