Anthropic released Claude8.3 out of 10 Sonnet 5 on June 30, positioning it as a substantially cheaper way to run agentic workloads that had previously required its flagship Opus model. Sonnet 5 is now the default model for Free and Pro plan users and is also available to Max, Team, and Enterprise customers, in Claude Code8.3 out of 10, and via the Claude Platform API.
Closing the gap with Opus, at a fraction of the cost
On SWE-bench Pro, an agentic coding benchmark that measures a model’s ability to write, run, and fix code across multi-step tasks rather than produce a single snippet, Sonnet 5 scores 63.2% — up from Sonnet 4.6’s 58.1% and closing to within about six points of Opus 4.8’s 69.2%. On Terminal-Bench 2.1, which tests command-line agentic tasks, Sonnet 5 actually outscores Opus 4.8, 80.4% to 74.6%. It also posts 81.2% on OSWorld-Verified (versus Opus 4.8’s 83.4%) and 84.7% on BrowseComp, a benchmark for agentic web search.
The pricing gap is the bigger story. Sonnet 5 launched at introductory API pricing of $2 per million input tokens and $10 per million output tokens, available through August 31, after which it moves to standard pricing of $3 per million input and $15 per million output. Opus 4.8, by comparison, is priced at $5 per million input tokens and $25 per million output tokens — meaning Sonnet 5 costs roughly 40% less than Opus at standard rates and around 60% less during the introductory window, while delivering performance that overlaps substantially with the flagship model on several agentic benchmarks.
Why it matters
Making a near-Opus-capability model the default for free users lowers the cost floor for running autonomous coding and browsing agents at scale, a shift that matters most for developers and enterprises running high-volume agentic workloads rather than one-off chat queries. The launch also lands as Anthropic pushes toward a widely reported IPO, with the pricing move read by several outlets as a bid to widen Claude’s usage base and agentic-coding market share ahead of that milestone. It follows a turbulent few weeks for Anthropic’s model lineup, after a US export control directive briefly halted global access to its Mythos 5 and Fable 5 models in mid-June before a partial reversal restored Mythos 5 to a vetted list of enterprise and government customers.