---
id: "entity-opus-4-6"
type: "entity"
entityType: "product"
canonicalName: "Opus 4.6"
aliases: ["Claude Opus 4.6"]
source_timestamps: ["§ The Coupling of Model Training and Harness Design"]
tags: ["model"]
related: ["entity-terminal-bench-2-0", "entity-claude-code", "contrarian-harness-optimization"]
canonicalUrl: "https://www.anthropic.com/news/claude-3-family"
---
# Opus 4.6

## Profile

**Opus 4.6** is a specific version of Anthropic's flagship Claude Opus model. (Public Anthropic marketing usually refers to “Claude 3 Opus” rather than numbered minor versions; “4.6” may be an internal or community designation.)

## Role in This Source

Used as the **fixed model variable** in the evidence for [[contrarian-harness-optimization]]. The author points out that **Opus 4.6 running inside [[entity-claude-code|Claude Code]] scores far below Opus 4.6 running in other, more optimized harnesses** on the [[entity-terminal-bench-2-0|Terminal Bench 2.0]] leaderboard.

This demonstrates that the native harness ([[concept-harness-model-coevolution|the one the model was co-evolved with]]) is not necessarily the optimal harness — a key empirical anchor for the article's thesis.