Claude Sonnet 4.8: not released as of May 25

Claude Sonnet 4.8 is still unannounced, and Anthropic’s current Sonnet remains 4.6.

Claude Sonnet 4.8 is not released as of May 25, 2026. Anthropic has not posted an announcement, published an API model id, or shared benchmarks, pricing, or a date.

What changed

The rumor came from a single leaked string in the Anthropic Claude Code source bundle, exposed after a source-map file shipped with the @anthropic-ai/claude-code npm package on March 31, 2026. That dump surfaced unreleased model references, including a mention of Sonnet 4.8, but no matching product page, API alias, or official post.

Anthropic’s public model list still shows Claude Sonnet 4.6 as the current Sonnet tier and Claude Opus 4.7 as the flagship. The lineup also includes Claude Haiku 4.5, while the separate Project Glasswing research model, Claude Mythos Preview, is invitation-only and not a Sonnet successor.

• No Anthropic announcement for Sonnet 4.8.
• No claude-sonnet-4-8 API id or alias.
• No benchmark table, context update, or price sheet.
• Manifold’s release market closed at 3% and resolved no.

Why it matters

For developers, the practical choice has not changed: use Sonnet 4.6 for balanced coding and agent work, or move to Opus 4.7 when deeper reasoning matters. Teams waiting on 4.8 should not treat the rumor as a deployable target, because there is still nothing to test, price, or benchmark.

The bigger signal is cadence. Anthropic has historically kept Sonnet releases close to the matching Opus version, and skipping from 4.6 to 4.8 would be unusual. That makes a near-term Sonnet 4.7 more plausible than a direct 4.8 jump, even if Anthropic eventually ships both.

For the market, the delay leaves room for rivals that moved in the same window, including OpenAI’s GPT-5.5 and DeepSeek’s V4 Preview. If you run model evals for coding agents, the right move is to compare what is actually available now, not wait on a name that has not been shipped.

The short version: Claude Sonnet 4.8 is a rumor, not a release, and the only safe plan today is to build around Sonnet 4.6 or Opus 4.7.