Claude Sonnet 5 just became the default AI for millions of users overnight

If you used Claude for free or on Pro this week and it suddenly felt sharper, that is not you imagining things. Anthropic switched every free and Pro user over to Claude Sonnet 5 without so much as a press conference, and it is quietly one of the bigger AI moves of the year.

Sonnet 5 landed on 30 June and became the default the very next day. No opt-in, no toggle, no "try the new model" banner to click past. One day you had Sonnet 4.6, the next you had a model Anthropic says gets close to its flagship Opus 4.8, for a fraction of the running cost.

That price gap matters more than the spec sheet. Sonnet 5 is priced at $2 per million input tokens and $10 per million output tokens until the end of August, before it jumps to $3 and $15. Opus 4.8 costs more than double that.

Anthropic's own benchmarks have Sonnet 5 scoring 63.2 percent on agentic coding against Opus 4.8's 69.2, and on knowledge work tasks it actually edges the flagship out.

Translation for anyone not fluent in benchmark speak: the free version of Claude just got noticeably better at planning, browsing, using tools and finishing multi-step jobs on its own, the kind of agentic work that used to be locked behind the expensive models.

Anthropic is also framing this as a safety upgrade, not just a capability one. Sonnet 5 reportedly hallucinates less, is less sycophantic and is better at shutting down prompt injection attempts than its predecessor.

Zapier engineer Daniel Shepard said in Anthropic's own release that a two-part job which used to stall halfway now finishes end to end without hand-holding.

Worth noting this is entirely separate from the Fable 5 access drama the blog covered recently. Two different models, two different stories, both landing in the same fortnight, which says something about how fast this industry is moving right now.

The bigger picture is the one worth sitting with. A model this capable, sitting on the free tier by default, is a genuinely big deal for accessibility. If you have not opened Claude in a while, it is worth a look this week, because the tool changed under you without asking permission first.