Breaking

Anthropic Releases Claude Sonnet 5.5 as Faster Mid-Tier Model for Agents and Developers

September 28, 2026 at 14:10 EDT

Foundation Models
AI Agents
Software Dev & Coding

Anthropic released Claude Sonnet 5.5 on September 28, positioning the new model as the company's best mix of speed and intelligence for everyday agentic work. The model is now listed as active on the Claude API, Amazon Bedrock, Google Cloud and Microsoft Foundry, with the API identifier claude-sonnet-5-5 and pricing of $2 per million input tokens and $10 per million output tokens in Anthropic's model documentation.

September 28, 2026 · Anthropic

Claude Sonnet 5.5 moves into the workhorse slot

The new Sonnet model pairs a 1M-token context window with faster latency and lower token pricing than Opus 5.5, while adding migration changes developers must handle.

context tokens

128K

max output

input per MTok

$10

output per MTok

Token price scale

Input

$10

Output

Each block represents $1 per million tokens.

Developer migration checklist

Thinking

Use between_tools instead of disabled.

Tools

Forced tool use is not supported.

Computer use

Move to computer_toolset_20260801 where required.

Why teams care

A faster mid-tier model with Opus-scale context is aimed at coding agents, workflow automation and high-volume knowledge work.

What may slow adoption

Existing Sonnet 5 integrations may need changes for thinking blocks, tool choice, advisor pairings and computer-use tools.

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