Claude Sonnet 5.5

Anthropic · Released September 2026

Claude Sonnet 5.5 is Anthropic's Sonnet-class model for well-scoped everyday work, succeeding Claude Sonnet 5 as a direct upgrade.

It belongs to Anthropic's Claude family: Opus is the deep-capability tier and Claude Opus 5.5 leads it, Sonnet balances quality and speed, Fable is the most recently introduced line, and Haiku is the light tier.

Facts and pricing

Provider

Anthropic

Context window

1M tokens

Input price

24.0 credits / 1M tokens ($2.00 raw)

Output price

120 credits / 1M tokens ($10.00 raw)

Vision (image input)

Yes

Tool calling

Yes

Extended reasoning

No

Credits are what Zeplik bills: 1 credit = $0.10, computed from the raw provider rate with a 1.20x margin. Raw prices shown per 1M tokens.

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What Claude Sonnet 5.5 is best for

• Hard problems where answer quality matters more than cost: strategy, analysis, difficult writing
• Very long documents and codebases: a 1M-token window fits entire books or repositories in one conversation
• Working with images: screenshots, charts, photos and scanned documents alongside text
• Tool use and agents: reliably calls functions, so it can search, run skills and drive workflows

Example prompts

Prompts that suit a frontier model like Claude Sonnet 5.5:

• Review this business plan and give me the three hardest questions an investor would ask
• Rewrite this announcement so it lands with both engineers and executives
• I am choosing between two job offers, help me think through the tradeoffs
• Draft a technical design doc for a rate limiter, including failure modes

Anthropic family

All 29 Anthropic models

Frequently asked questions

What is Claude Sonnet 5.5?

Claude Sonnet 5.5 is an AI model by Anthropic. Claude Sonnet 5.5 is Anthropic's Sonnet-class model for well-scoped everyday work, succeeding Claude Sonnet 5 as a direct upgrade.

How much does Claude Sonnet 5.5 cost on Zeplik?

Input tokens cost 24.0 credits per million and output tokens 120 credits per million (1 credit = $0.10; the raw provider rates are $2.00 and $10.00 per million). New accounts start with free credits.

How long can a conversation with Claude Sonnet 5.5 be?

Claude Sonnet 5.5 has a 1M-token context window (1,000,000 tokens), which covers the conversation plus any documents you attach.

Does Claude Sonnet 5.5 support images and tools?

Claude Sonnet 5.5 accepts image input and supports tool calling.

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