Anthropic's Claude Sonnet 5 lands as default model across Free and Pro, at a steep discount to Opus 4.8

The mid-tier release closes much of the agentic-coding gap with the flagship Opus 4.8 at roughly 40 percent lower list pricing, and arrives with Anthropic's IPO prospectus confidentially filed and its most powerful models still under Trump-administration restrictions.

Anthropic on Monday released Claude Sonnet 5 and installed it as the default model across its Free and Pro plans, positioning what the company calls “the most agentic Sonnet model yet” as a deliberately cheaper substitute for its flagship Opus 4.8. The model is also available on Max, Team, and Enterprise tiers, in Claude Code, and through the Claude API.

The pricing gap is the story. Sonnet 5 lists at $2 per million input tokens and $10 per million output tokens through August 31, 2026, before settling at $3 and $15. Opus 4.8 remains $5 and $25. By VentureBeat’s math, that’s roughly 40 percent cheaper at standard rates and about 60 percent cheaper during the introductory window.

On an agentic coding evaluation, Sonnet 5 scored 63.2 percent versus 69.2 percent for Opus 4.8 and 58.1 percent for the February-vintage Sonnet 4.6. Anthropic’s framing is characteristically restrained: “Opus 4.8 is still the model of choice for higher accuracy on these tasks, but Sonnet 5 provides developers with lower-priced options that are of much higher quality than what was previously available.”

There’s a wrinkle. Sonnet 5 ships with an updated tokenizer that maps the same input to 1.0–1.35× more tokens depending on content type, which Anthropic says leaves the introductory price “roughly cost-neutral” against Sonnet 4.6. The company also claims a lower rate of undesirable behaviors than 4.6 and “a much lower ability to perform” dangerous cybersecurity tasks than current Opus models.

That safety framing isn’t decorative. Per Axios, Anthropic remains in ongoing talks with the Trump administration over its most powerful systems, discussions that extended into the Sonnet 5 release. Mythos is back on a limited basis, and Fable 5 is “on track to return soon” after the government asked Anthropic to pull both over security concerns.

The commercial subtext is legible enough. Anthropic confidentially filed its S-1 with the SEC in early June, in what CNBC called “the most scrutinized public offering of the year.” Sonnet 5 is the high-volume, lower-margin product that has to carry the revenue story to public investors while the most capable models sit in a regulatory holding pattern. The IPO gets pitched on the tier the government hasn’t restricted.

Anthropic's Claude Sonnet 5 lands as default model across Free and Pro, at a steep discount to Opus 4.8

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