---
id: "anthropic/claude-sonnet-5.5"
also: ["anthropic/claude-sonnet-5.5-20260928", "requesty/anthropic/claude-sonnet-5-5", "vercel/anthropic/claude-sonnet-5.5"]
card_usd_per_m: "2.0 in, 10.0 out, at anthropic"
cheapest_list_usd_per_m: "2.0 in, 10.0 out, at amazon-bedrock on openrouter"
cheapest_effective_usd_per_m: "0.39 in, 10.0 out, at vertexAnthropic on vercel"
context: 1000000
max_output: 128000
input: ["text", "image", "file"]
output: ["text"]
released: "2026-09-28"
reasoning: ["max", "xhigh", "high", "medium", "low"]
api: ["/api/v1/chat/completions", "/api/v1/completions", "/api/v1/messages", "/api/v1/responses"]
params: ["include_reasoning", "max_completion_tokens", "max_tokens", "reasoning", "reasoning_effort", "response_format", "stop", "structured_outputs", "tool_choice", "tools", "verbosity"]
endpoints: 23
gateways: "openrouter (10), requesty (9), vercel (4)"
no_training: 23
trains: 0
retains_prompts: 5
intelligence: 54.5000
---
# Anthropic: Claude Sonnet 5.5

Claude Sonnet 5.5 is a step-change improvement over Sonnet 5. It performs great with well-scoped everyday tasks like building features, fixing bugs, and creating polished documents, slides, and spreadsheets. Sonnet 5.5 also improves on communication and writes more clearly than Sonnet 5.