Frontier builder · United States

Anthropic

Frontier IC25 · Edition 2026.3 · Evidence reviewed October 8, 2026 UTC

A model builder whose Claude APIs expose reasoning, tool use and coding workflows.

Selected for a consequential, inspectable general-purpose model contribution. The displayed model is a named representative, not a claim of latest or best performance.

Official transparency page explicitly identifies US headquarters.

Selected model

Claude Sonnet 5.5 · claude-sonnet-5-5

Standard first-party synchronous API; uncached text tokens, prompt ≤100K.

1,000,000 · Context window

Scope and limitations

• Adaptive thinking is enabled by default; thinking tokens are billed as output and count toward output limits, even when returned thinking is omitted or summarized.
• 1 million context tokens are available at standard price; the legacy >200K premium does not apply to this selected model.
• US-only inference has a 1.1x token-price multiplier. Partner platforms have independent regional pricing.
• The 300K output beta is Batch API only and is excluded from this synchronous comparison.

Original sources

• Model specs
• First-party base pricing
• Thinking and billing
• Company headquarters
• Commercial service terms

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