Claude Opus 5.5
The strongest-performing model we've tested to date
Context window
1M
Input / 1M tokens
$4.00
Output / 1M tokens
$20.00
Provider
Anthropic
Data verified 2026-09-23
Claude Opus 5.5 is Anthropic's flagship reasoning and coding model, featuring a 1M token context window and adaptive thinking. It performs at Claude Fable 5.1 level on most work while costing 40% less to run than Opus 5, with 30% faster output speeds. Optimized for agentic coding tasks, knowledge work, and financial analysis.
Capability index
Relative estimates (0-100) to place this model against its peers, grounded in published benchmarks.
How to access it
Available via Anthropic Claude API, Amazon Bedrock, Google Cloud, and Microsoft Foundry. Accessible through Claude web interface and subscription plans.
Strengths
- ✓Achieves Fable 5.1-level performance at 40% lower cost
- ✓1M token context window for long-running tasks
- ✓30%+ faster output generation than Opus 5
- ✓Strongest performance on Anthropic's alignment tests
- ✓Multimodal input (text and images)
- ✓Improved clarity in communication
Best for developers who...
When to choose it (and when not to)
Reach for Claude Opus 5.5 when...
- →When you need Fable-level performance at mid-tier pricing
- →For long-context coding and knowledge work
- →When cost-efficiency matters alongside capability
Look elsewhere if...
- ✕If you need the absolute highest performance (use Fable 5.1)
- ✕For simple, quick queries where faster/cheaper models suffice
How to use it
- ›Leverage the 1M context window for comprehensive documents and conversation history
- ›Adaptive thinking is always-on with medium as default effort level
Quickstart
Pythonimport anthropic
client = anthropic.Anthropic()
message = client.messages.create(
model="claude-opus-5-5",
max_tokens=1024,
messages=[{"role": "user", "content": "Your prompt here"}]
)
print(message.content[0].text)Model ID is 'claude-opus-5-5' across all platforms (API, Bedrock, GCP, Azure)
API model id: claude-opus-5-5
Benchmarks
| Benchmark | Score | Notes |
|---|---|---|
| Terminal Bench 4.0 | 66.4% | Internal Anthropic benchmark |
| Anthropic Automated Behavioral Audit | Strongest-performing model tested | Comprehensive alignment and safety evaluation |
Source: Anthropic System Card
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