---
id: "anthropic/claude-opus-5.5"
also: ["anthropic/claude-opus-5.5-20260921", "requesty/anthropic/claude-opus-5-5", "vercel/anthropic/claude-opus-5.5"]
card_usd_per_m: "4.0 in, 20.0 out, at anthropic"
cheapest_list_usd_per_m: "4.0 in, 20.0 out, at amazon-bedrock on openrouter"
cheapest_effective_usd_per_m: "0.3991 in, 22.0 out, at google-vertex/europe on openrouter"
context: 1000000
max_output: 128000
input: ["text", "image", "file"]
output: ["text"]
released: "2026-09-22"
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: 27
gateways: "requesty (12), openrouter (11), vercel (4)"
no_training: 27
trains: 0
retains_prompts: 6
intelligence: 59.1000
---
# Anthropic: Claude Opus 5.5

Claude Opus 5.5 is a step-change improvement over Opus 5, with the biggest gains in agentic coding, long-running agentic tasks, and knowledge work. It is also a much better collaborator on long-running work. It reports back in plain language on what it did, what it found, and what it needs next.