Use Claude Sonnet 5.5 in AimiChat

What is Claude Sonnet 5.5?

Anthropic released Claude Sonnet 5.5 on September 28, 2026, six days after Claude Opus 5.5. It is a direct upgrade over Claude Sonnet 5: Anthropic says it runs more than 30% faster, needs far fewer tokens for the same work, and costs up to 30% less per task at the same list price.

It is aimed at well-scoped everyday work: building features, fixing bugs, and producing polished documents, slides and spreadsheets. It keeps the 1-million-token context window and text, image and file inputs. Through the API it costs $2 per million input tokens and $10 per million output tokens, the same list price as OpenAI's GPT-6 Sol.

Claude Sonnet 5.5 specs and pricing

API prices are what developers pay Anthropic directly. In AimiChat you pay a flat plan price instead and do not need your own API key. Limits per message and per day depend on your plan.

What Claude Sonnet 5.5 is good at

• Writing that needs little editing. Reports, articles, cover letters and long emails where structure and tone matter. Anthropic says it writes more clearly than the previous generation.
• Following detailed instructions. Prompts with many constraints, formats or style rules that must all be respected at once.
• Coding and bug fixing. Understanding an unfamiliar codebase quickly, fixing bugs, and writing functions with tests. Anthropic reports a large jump over Sonnet 5 on agentic coding.
• Documents, slides and spreadsheets. Reading long PDFs, contracts or research papers, and turning material into a polished deck or report.

When to use a different model

• The hardest problems. For long, open-ended work that needs sustained judgment, or large codebase changes, Claude Opus 5.5 is still the stronger choice.
• Quick one-line answers. If you only need a fast definition or rewrite, GPT-6 Luna on the Free plan is quicker and uses fewer credits.
• Some cybersecurity requests. Anthropic ships Sonnet 5.5 with extra cyber safeguards, so higher-risk security requests may be handled more conservatively or answered by an earlier model.

Claude Sonnet 5.5 benchmarks

These are the maker's own published results. Different companies run different test setups, so scores are only comparable within the same table from the same source.

Prompts to try with Claude Sonnet 5.5

1. Here is my rough draft. Keep my voice, cut filler, and flag any sentence that makes a claim I have not supported.
2. Review this function for bugs and edge cases, then rewrite it with tests.
3. Read this contract and list every obligation, deadline and penalty, with the clause each one comes from.

How to use Claude Sonnet 5.5 in AimiChat

1. Open AimiChat and sign in on the Aimi+ plan or higher (see plans).
2. Choose the Balanced quality in the model menu next to the message box.
3. Send your message. You can switch quality in the same chat at any time, so you can start with a faster model and move up when a question needs more depth.

Compare Claude Sonnet 5.5

• Claude Sonnet 5.5 vs GPT-6 Sol: when GPT-6 Sol is the better pick.
• Claude Opus 5.5 vs Claude Sonnet 5.5: when Claude Opus 5.5 is the better pick.
• Claude Sonnet 5.5 vs GPT-6 Luna: when GPT-6 Luna is the better pick.

See every model in AimiChat side by side.

Claude Sonnet 5.5 FAQ

Which AimiChat plan includes Claude Sonnet 5.5?

Claude Sonnet 5.5 powers the Balanced quality, included from the Aimi+ plan ($15/month). Aimi Ultra and Aimi Genius include it too.

What changed from Claude Sonnet 5?

Anthropic reports it runs more than 30% faster, costs up to 30% less per task because it uses fewer tokens, writes more clearly, and scores 70.6% on Terminal-Bench 4.0 against 10.3% for Sonnet 5. The price per token is unchanged.

How big is Claude Sonnet 5.5's context window?

Published specs list 1 million tokens of context and up to 128,000 output tokens through the API. The amount you can use in a single AimiChat message depends on your plan.

Is Claude Sonnet 5.5 better than GPT-6 Sol?

They cost the same through the API and are close overall. Sonnet 5.5 tends to be the better writer and instruction follower; GPT-6 Sol is aimed at demanding reasoning and agentic coding. See the full comparison for details.

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