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How to Run a Gauntlet Loop
The prompting method behind Claude of Duty. Give the agent a bar it can't talk its way around, let it split the work, and never let the builder grade itself.
Matt Shumer
Claude Opus 5
Opus 5 is a step change improvement for the Opus tier powering long-running agents while delivering improvements in coding and professional work.
Specs
Model
- Family
- Claude
- Variant
- Opus 5
- Weights
- Proprietary
Limits
- Context
- 1,000,000 tokens
- Max output
- 128,000 tokens
Modalities
- Input
- Text Image PDF
- Output
- Text
Pricing
- Input
- $5 / 1M
- Output
- $25 / 1M
- Cache read
- $0.5 / 1M
- Cache write
- $6.25 / 1M
Capabilities
- Reasoning
- Yes
- Reasoning control
- Effort levels
- Tool calling
- Yes
- Attachments
- Yes
Dates
- Released
- 24 Jul 2026
- Knowledge cutoff
- May 2026
Articles
All articlessomethingbig.ai
Anthropic
Introducing Claude Opus 5
Opus 5 is a step change improvement for the Opus tier powering long-running agents while delivering improvements in coding and professional work.
Anthropic
X
The new rules of context engineering for Claude 5 models
I’ve written previously about how to best prompt the newest generation of Claude 5 models and work with them iteratively to discover what you want to build.
Thariq@trq212