AISystem

Claude Sonnet 5

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)

Anthropic model used as the predecessor comparison for Sonnet 5.5.

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Development timeline

Newest reporting dates first. Reporting dates may differ from event dates.

2026-09-30: Sonnet 5.5's longer output raises reported task costs

2026-09-29: Anthropic introduces Claude Sonnet 5.5

2026-09-29: Sonnet 5.5 improves on Terminal-Bench 4.0

Knowledge graphopen in browser →

Developed by

Anthropic

Evaluated on

Terminal-Bench 4.0

Cite or correct this record

Citation formatCitation text

Claude Sonnet 5
Innermost Loop KB — secondary record
Reporting date: unknown
KB permalink: https://nicholsn.github.io/innermost-loop-kb/systems/claude-sonnet-5
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.

Suggest a correction — opens a GitHub draft for you to review and submit.