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Anthropic swapped Claude's default model — what Claude says about your business changed with it

On June 30, 2026, Anthropic released Claude Sonnet 5 and made it the default model for every Free and Pro Claude user. That means the answers Claude gives to “who's the best {your category} in {your city}” are now generated by a different model than they were a week ago — and any AI-visibility measurement taken before the swap describes a model your buyers no longer talk to.

What Anthropic shipped

According to Anthropic's announcement, published June 30, 2026:

Why a default-model swap matters if you care about AI visibility

Claude is one of the four engines we query in every AskedAbout audit, and for many businesses it's quietly the friendliest one: in our 1,120-answer engine comparison, Claude recommended the audited business in 38% of answers — more than double ChatGPT's 16%. Those numbers were measured against the model Claude was running then. As of this week, the model answering buyer questions for most Claude users is a different one.

AI answers are unstable even when the model doesn't change: in our run-to-run study, only 31% of recommended brands survived every repeat of the same question on the same engine. A default-model swap is a step change on top of that flicker — new training, new search behavior, and no guarantee the businesses Sonnet 4.6 kept naming are the ones Sonnet 5 names.

The takeaway

Treat June 30 as a reset line for your Claude numbers. Any measurement taken before it — a screenshot, an agency report, the Claude column in a monitoring dashboard — describes a retired model. Re-measure this week: a free 60-second check shows what the engines say about your business right now, and if a tool is doing this for you, confirm it has re-sampled since the swap (here's how the monitoring tools compare). Engines change underneath you without notice; local businesses — med spas, law firms, the trades — are the least likely to hear about it and the most exposed when the shortlist reshuffles.

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