Official Prompting Guide for Anthropic's Claude Opus 5.5 Released

What happened

Anthropic has successively released the Claude Opus 5.5 adaptation guide and mid-tier model Claude Sonnet 5.5, alongside launching a plugin portal, Cloud Sessions, Claude Projects, and open-source custom agent framework Claude Mods, with Haiku 5.5 scheduled to launch in the coming weeks. Opus 5.5 delivers over 30% faster output token speed compared to its predecessor, with its default effort tier adjusted from High to Medium; Sonnet 5.5 boasts over 30% faster inference speed than the previous generation, costs reduced by up to 30% for most use cases, matches the predecessor's pricing point, and is already the default model for claude.ai's free tier.

Key facts

Release issuer

Anthropic

Core released offerings

Claude Opus 5.5 adaptation guide, Claude Sonnet 5.5, plugin portal, Cloud Sessions, Claude Projects, Claude Mods

Sonnet 5.5 core specifications

Over 30% faster speed than the previous generation, costs reduced by up to 30% for most use cases, pricing matches the predecessor

Sonnet 5.5 launch status

Already deployed as the default model for the claude.ai free tier

Upcoming product roadmap

Haiku 5.5 expected to launch within weeks

Anthropic latest annualized revenue

Surpassed $65 billion in July 2026, projected to hit $100 billion by year-end

Background

Anthropic has previously rolled out flagship and mid-tier models including Opus 5 and, three months ago, Sonnet 5. Competition on cost-effectiveness in the mid-tier large model space is heating up across the industry, and the performance bar for free AI products continues to rise.

Why it matters

For the large model industry, this release lowers the barrier to deploying high-end models, escalates cost-effectiveness competition in the mid-tier segment, and raises the competitiveness threshold for free AI offerings by bringing near-top model capabilities to the free tier. For developers, it will sharply reduce costs for cross-version adaptation, prototyping, and agent deployment, while the custom agent framework lowers the barrier to building bespoke programming agents. For end users, it delivers smoother response experiences and near-high-end model capabilities at no cost.

What to watch

Watch for the official launch performance of Haiku 5.5 in the coming weeks, as well as official disclosures on AI integration in finance at the New York AI Engineers Conference in two weeks.