Development

Sonnet 5.5 improves on Terminal-Bench 4.0

development2026-09-29benchmarks

Claim

The newsletter reports Sonnet's Terminal-Bench 4.0 score rising from 10.3% to 70.6%, with Sonnet 5.5 outperforming Opus 5.5.

Reported metric: 10.3% to 70.6%

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

Referenced by

Welcome to September 29, 2026

Cite or correct this record

Citation formatCitation text

Sonnet 5.5 improves on Terminal-Bench 4.0
Innermost Loop KB — secondary record
Reporting date: 2026-09-29
KB permalink: https://nicholsn.github.io/innermost-loop-kb/developments/2026-09-29-sonnet-terminal
Claim: The newsletter reports Sonnet's Terminal-Bench 4.0 score rising from 10.3% to 70.6%, with Sonnet 5.5 outperforming Opus 5.5.
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.

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