Claude Opus 5.5 (Fast)

anthropic/claude-opus-5.5-fast

A chat model with a 1M-token context window, at $8.40 per million input tokens and $42.00 per million output tokens.

Details

Maker: anthropic
Kind: Chat
Context window: 1,000,000 tokens
Max output: 128,000 tokens
Input: $8.40 per million tokens
Cached input: $0.42 per million tokens, 95% off
Cache write: $10.50 per million tokens
Output: $42.00 per million tokens
Capabilities: Reasoning, tool use, vision, file input, web search, fast
Takes: Text, image, pdf
Returns: Text
Zero data retention: Yes, on every provider
No training on requests: Yes, on every provider
Released: 2026-09-22
Newer model: anthropic/claude-haiku-5.5Released later by the same maker, costs no more, and lists the same capabilities. Compare the two

Description

Claude Opus 5.5 is a step-change improvement over Opus 5 for agentic coding, long-running agentic tasks, knowledge work, communication, and vision. It is more token-efficient per completed task and reports progress, findings, and next steps in clear language.

Call it

curl

curl https://phantom.codes/v1/chat/completions \
  -H "Authorization: Bearer $PHANTOM_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-opus-5.5-fast",
    "messages": [
      {"role": "user", "content": "Hello"}
    ]
  }'

Set PHANTOM_KEY to your key. Any OpenAI client works with the base URL https://phantom.codes/v1.

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