Claude Opus 5.5 launches with lower pricing for long-running agents

Anthropic has launched Claude Opus 5.5, the first model in its Claude 5.5 family. Anthropic describes it as a model for long-running agentic coding and knowledge work, with a 1M-token context window by default and always-on adaptive thinking.

A lower-cost Opus tier

The Claude API release notes list claude-opus-5-5 at $4 per million input tokens and $20 per million output tokens, down from $5 and $25 for Claude Opus 5. Cache reads are listed at $0.20 per million tokens, 60% lower than Opus 5.

Anthropic says Opus 5.5 is available through the Claude API, Amazon Bedrock, Claude Platform on AWS, Google Cloud, and Microsoft Foundry. The model is also available to Claude Pro, Max, Team, and Enterprise users.

Fast mode is available in Claude Code and on the Claude Platform, with up to 2.5x faster speed. Anthropic lists fast mode at $8 per million input tokens and $40 per million output tokens.

Model behavior and migration details

Opus 5.5 has a 128k maximum output and always-on adaptive thinking. On the Claude API and Google Cloud, computer use requires the computer_toolset_20260801 toolset; the earlier computer_20251124 tool returns a 400 error there. Amazon Bedrock keeps computer_20251124 working, according to Anthropic’s release notes.

Thinking cannot be disabled on Opus 5.5. Applications that previously sent thinking: {"type": "disabled"} should test the new model path and update error handling before switching production traffic.

What coding teams should test

The larger context window suits repository-scale work, but context capacity alone does not guarantee better agent runs. Compare Opus 5.5 with the model you use today on representative migrations, code review, tool-call reliability, and total tokens per completed task. Measure cache hits and output length along with latency and quality.

Sources

• Anthropic — “Introducing Claude Opus 5.5” (September 22, 2026): https://www.anthropic.com/claude-opus-5-5
• Anthropic — Claude Platform API release notes: https://docs.anthropic.com/en/release-notes/api
• Anthropic — Claude Opus model page: https://www.anthropic.com/claude/opus
• Anthropic on X — official Claude developer updates: https://x.com/ClaudeDevs