Anthropic launches Claude Sonnet 5.5, faster mid-tier AI model ahead of IPO

Anthropic on Monday released Claude Sonnet 5.5, the second model in its Claude 5.5 family, as the AI lab expands its product lineup ahead of a planned IPO, Reuters reported.

The new model is priced at $2 per million input tokens and $10 per million output tokens — unchanged from its predecessor, Sonnet 5. Anthropic said it produces responses more than 30 per cent faster and can cost up to 30 per cent less per task, because it needs fewer tokens to complete the same work.

The company positions Sonnet 5.5 as a faster, lower-cost complement to Claude Opus 5.5, which it launched last week at $4 per million input tokens and $20 per million output tokens. The model’s biggest reported jump is in agentic coding: it scored 70.6 per cent on Terminal-Bench 4.0, up from 10.3 per cent for Sonnet 5 and ahead of the pricier Opus 5.5’s 66.4 per cent. It also reached 55.5 per cent on CursorBench 4.0 and, according to the company, became the first Sonnet model to beat the game Pokémon Red using only screenshots.

Anthropic says Sonnet 5.5 is suited to everyday enterprise tasks such as coding, document creation and spreadsheet work. Enterprise customers account for about 80 per cent of its business, with clients including Salesforce, Databricks, Goldman Sachs and Novo Nordisk. A third model, Haiku 5.5, designed for fast, high-volume work, is due soon.

The launch comes amid a heated debate over AI safety. Chief executive Dario Amodei earlier this month called on the global AI community to slow the pace of releasing new capabilities to address safety concerns.

Sources

• Reuters: “Anthropic rolls out second Claude 5.5 model as it builds toward IPO” (28 September 2026) — https://www.reuters.com/technology/anthropic-rolls-out-second-claude-55-model-it-builds-toward-ipo-2026-09-28/
• Business Today: “Anthropic introduces Claude Sonnet 5.5: Faster AI model promises lower costs” — https://www.businesstoday.in/technology/news/story/anthropic-introduces-claude-sonnet-5-5-faster-ai-model-promises-lower-costs-558406-2026-09-29