Development

Anthropic introduces Claude Sonnet 5.5

The edition connects lower cost with stronger capabilities and new safety requirements.

development2026-09-29models

Claim

The issue reports Sonnet 5.5 being over 30% faster and up to 30% cheaper than Sonnet 5, the first Sonnet to complete Pokémon Red from screenshots and the first to require cyber safeguards.

Reported metric: 30%+ faster; up to 30% cheaper

Reporting date: 2026-09-29 (not necessarily the event date)

Sources

Attribution and reporting linked by this record; links do not imply independent verification.

Welcome to September 29, 2026 (theinnermostloop.substack.com)
Source linked by the September 29 issue (www.anthropic.com)

Indexed from the September 29 newsletter. Linked-source claims have not been independently verified.

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About

Reported in

Welcome to September 29, 2026

Actor

Anthropic

Evidence for

An intelligence explosion that is also a price implosion

Referenced by

Cite or correct this record

Citation formatCitation text

Anthropic introduces Claude Sonnet 5.5
Innermost Loop KB — secondary record
Reporting date: 2026-09-29
KB permalink: https://nicholsn.github.io/innermost-loop-kb/developments/2026-09-29-sonnet-release
Claim: The issue reports Sonnet 5.5 being over 30% faster and up to 30% cheaper than Sonnet 5, the first Sonnet to complete Pokémon Red from screenshots and the first to require cyber safeguards.
Attributed sources:
- Welcome to September 29, 2026 — https://theinnermostloop.substack.com/p/welcome-to-september-29-2026
- Source linked by the September 29 issue — https://www.anthropic.com/claude-sonnet-5-5
This citation does not imply independent verification of linked-source claims.

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