Claude Sonnet 5.5

Claims and evidence

• Released 28 September 2026 ● Primary source[1] [3]Availability: Released

• Status Available ● Primary source[4]Compare models table [3]Availability [5]Model status table

• Successor of Claude Sonnet 5 ● Primary source[1]Introduction and Cost [6]

• Change · Safety Adds safety classifiers that block reasoning extraction, which Anthropic says is a first for a Sonnet model.Compared with Claude Sonnet 5 ● Primary source[1]
• Change · Reasoning Up-front thinking is turned off with the new between_tools setting instead of the disabled value, at high effort or below.Compared with Claude Sonnet 5 ● Primary source[2]September 28, 2026
• Change · Tool use Forced tool use (tool_choice types any and tool) returns an error.Compared with Claude Sonnet 5 ● Primary source[2]September 28, 2026
• Change · Tool use The older computer_20251124 computer use tool is not accepted on the Claude API and Google Cloud.Compared with Claude Sonnet 5 ● Primary source[2]September 28, 2026

• Input text, image ● Primary source[3]Capabilities: Input and output
• Output text ● Primary source[3]Capabilities: Input and output
• Context window 1M tokens ● Primary source[3]Capabilities: Context window
• Parameters Not disclosedNot disclosed by Anthropic. No claim madeNo source
• Access API, consumer app, cloud partner ● Primary source[1]Getting started [3]Availability: Platforms

Lineage

Variants

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