Anthropic Claude Sonnet 5
This is a rumor, not an announcement: as of June 23, 2026 Anthropic has confirmed nothing, and 'Claude Sonnet 5' does not appear on its official model pages. Reporting traces back to a 'claude-sonnet-5' identifier (codename 'Fennec') that surfaced in a Google Vertex AI log in early February 2026, plus the same slug reappearing on an Anthropic partner provider — leaks of this kind have historically preceded a release by days, but in February that exact checkpoint shipped as Claude Sonnet 4.6, not a '5'. June 2026 coverage lumps Sonnet 5 in with an expected OpenAI GPT-5.6 launch 'the week of June 23,' though that window is applied more confidently to GPT-5.6 than to Sonnet. The substantive rumors — a 1M-token context, stronger coding, better vision and price/performance versus the Opus/Fable tier — are unverified leak claims and benchmark guesses, not measured results. Net: a credible expectation that a next Sonnet is in testing, attached to a low-confidence, repeatedly-wrong timing prediction, with no specs Anthropic stands behind.
Sonnet is Anthropic's mid-tier 'workhorse,' the model most teams actually deploy at scale, so a generational bump would reset the cost-for-capability math for everyday AI work. The bigger literacy lesson: 'imminent next week' has been wrong about this exact model since February — a reminder to wait for the vendor's own announcement before acting on a leak.