Breaking

Anthropic Launches Claude Sonnet 5.5 Across Claude Platform and Claude Code

September 29, 2026 at 07:42 EDT

Foundation Models
AI Agents
Software Dev & Coding

Anthropic released Claude Sonnet 5.5 on September 28, positioning it as a faster, lower-cost successor to Claude Sonnet 5 for everyday coding, agentic workflows and knowledge work. The model is available across Anthropic’s services and cloud channels, including Claude Platform, Claude Code, Amazon Web Services, Google Cloud and Microsoft Azure, with the API model ID claude-sonnet-5-5.

Sep. 28, 2026 · Anthropic

Claude Sonnet 5.5 targets faster coding agents

The new Sonnet model keeps the $2/$10 per million-token list price while claiming a large jump on agentic coding benchmarks and more than 30% faster output.

70.6%

Terminal-Bench 4.0 score

Token context window

30%+

Faster output than Sonnet 5

$2/$10

Input/output price per MTok

Agentic coding jump

10.3%

Sonnet 5

70.6%

Sonnet 5.5

66.4%

Opus 5.5

Stacked columns show Terminal-Bench 4.0 scores rounded to proportional segments.

Where it fits

Plan

Opus 5.5 remains the higher-tier option for complex judgment.

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Implement

Sonnet 5.5 is aimed at routine coding, bug fixing and agent steps.

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Check cost

Cache-heavy sessions may see a different cost profile.

Positive read

Developers are treating it as a speed-and-efficiency upgrade for everyday coding-agent work.

Open question

The same $0.20 cache-read price as Opus 5.5 complicates the value case for cache-heavy workloads.

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