Claude Opus 5.5

by Anthropic

Claude Opus 5.5 is Anthropic's most capable model as of September 2026, released September 22, 2026. It is designed for long-running agentic coding and knowledge work, featuring a one-million-token context window and adaptive thinking. It includes strengthened cybersecurity, biology, and anti-distillation safeguards.

Large Language Models
Proprietary

Primary Use Cases

  • Long-horizon agentic software development
  • Complex knowledge work and research
  • Enterprise coding automation
  • Tasks requiring extended context retention

✅ Strengths

  • Largest context window in Anthropic lineup at 1M tokens
  • Strongest Anthropic model for agentic and coding tasks
  • Comprehensive safety evaluations published

⚠️ Limitations

  • Higher cost than Sonnet 5.5
  • Released September 22 — just outside the exact reporting week

Technical Specifications

Developer
Anthropic
Category
Large Language Models
Type
🧠 Foundation Model
License
UNKNOWN
Version
Opus 5.5

Trust & Privacy

Health Status
🟢 Active
Trains on User Data
🔄 Opt-out available
Certifications
None listed

Ecosystem & Integrations

API Access
✅ Available
Chrome Extension
❌ No
Mobile App
❌ No
Pricing Model
💰 Pay Per Use

Pricing Breakdown

API

Pay-per-use API access