---
id: "2026-07-24-claude-opus-5"
url: "https://postcutoff.com/e/2026-07-24-claude-opus-5/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2026-07-24"
date_precision: day
category: model-release
importance: 4
confidence: high
status: [Confirmed]
sources: 9
editor: human editor
human_review: null
version: "2026-10-29"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2026-07-24-claude-opus-5/

# Anthropic releases Claude Opus 5

Full title: Anthropic releases Claude Opus 5 — near-Fable-5 intelligence at half the price

Claude Opus 5 (`claude-opus-5`) launched on July 24, 2026 at $5/$25 per million tokens. Anthropic said it comes close to Fable 5's frontier intelligence at half the price and sets new highs on Frontier-Bench v0.1 and GDPval-AA. Developers soon complained it was verbose and prone to over-engineering, which Opus 5.5 set out to fix two months later.

## Key facts
- Released July 24, 2026; model id claude-opus-5; $5 input / $25 output per 1M tokens; fast mode 2x base price for ~2.5x speed
- Context 1M tokens (default and max), 128K output; thinking on by default
- Frontier-Bench v0.1: more than doubles Opus 4.8's performance; CursorBench 3.2 within 0.5% of Fable 5 at half the cost (Anthropic)
- Anthropic reports an ARC-AGI-3 score 3x higher than the next-best model (exact number not captured)
- Default model on Claude Max; cybersecurity classifiers intervene 85% less often than on Fable 5
- Anthropic called it its 'most aligned model to date' on the behavioral audit
- Irregular (July 24): on a nine-challenge CyScenarioBench subset with deployment mitigations disabled, Opus 5 averaged a 33.7% solve rate vs Opus 4.8 24.4%, Sonnet 5 3.3% and Claude Mythos 5 47.0%; most attempts did not reach the scenario objective

## What happened

Opus 5 upgrades Opus 4.8 with gains in agentic coding, computer use and long-horizon knowledge work. It is much better at verifying its own work and iterating until it succeeds. New API betas arrived with it: changing tools mid-conversation and automatic fallback to alternative models. It remained behind Mythos 5 on cyber exploitation and biology research.

Reception was mixed. Commentators such as MindStudio reported developer complaints that it was verbose, turned small fixes into large rewrites, and flagged trivial issues as urgent.

## Why it matters

Opus 5 brought most of Fable 5's capability to half the price. Its reception problems explain why Opus 5.5's launch messaging stressed clear, concise communication.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): 85 days after its cutoff
- Claude Opus 5.5 (training cutoff June 2026): 24 days after its cutoff
- Gemini 4 Hydrogen (training cutoff March 2026): 115 days after its cutoff
- Grok 4.7 (training cutoff May 2026): 54 days after its cutoff

## Sources

1. [Introducing Claude Opus 5 (Anthropic)](https://www.anthropic.com/news/claude-opus-5) (anthropic.com, official)
2. [Claude Opus 5 System Card (PDF)](https://www-cdn.anthropic.com/c5fbac3f0b1280a933ebd26d3cb8bb9f5bdeaf48/Claude%20Opus%205%20System%20Card.pdf) (www-cdn.anthropic.com, paper)
3. [Claude Opus 5 docs overview](https://platform.claude.com/docs/en/models/opus-5/overview) (platform.claude.com, docs)
4. [Irregular: Assessing Claude Opus 5 against offensive security benchmarks (July 24)](https://www.irregular.com/research/assessing-claude-opus-5-against-offensive-security-benchmarks) (irregular.com, official)
5. [TechCrunch: Anthropic launches Opus 5](https://techcrunch.com/2026/07/24/anthropic-launches-opus-5/) (techcrunch.com, press)
6. [Axios: Anthropic releases new model, Opus 5](https://www.axios.com/2026/07/24/anthropic-releases-new-model-opus-5) (axios.com, press)
7. [9to5Mac: Anthropic upgrades Claude with Opus 5](https://9to5mac.com/2026/07/24/anthropic-upgrades-claude-with-new-opus-5-model-details-here/) (9to5mac.com, press)
8. [Simon Willison: Introducing Claude Opus 5](https://simonwillison.net/2026/Jul/24/introducing-claude-opus-5/) (simonwillison.net, discussion)
9. [MindStudio: Why is Opus 5 getting bad reviews despite top benchmarks?](https://www.mindstudio.ai/blog/anthropic-claude-opus-5-trust-crisis) (mindstudio.ai, discussion)

## Changes

- 2026-10-29: Added Irregular's CyScenarioBench result (read directly) (news agent)
- 2026-09-29 (filed): Created

## Related

- 2026-09-22: [Anthropic releases Claude Opus 5.5](https://postcutoff.com/e/2026-09-22-claude-opus-5-5/index.md)
- 2026-06-09: [Anthropic releases Claude Fable 5 and Claude Mythos 5](https://postcutoff.com/e/2026-06-09-claude-fable-5-mythos-5/index.md)
- 2026-05-28: [Anthropic releases Claude Opus 4.8 with cheaper fast mode and Claude Code "dynamic workflows"](https://postcutoff.com/e/2026-05-28-claude-opus-4-8/index.md)
- People: [Simon Willison](https://postcutoff.com/person/simon-willison/)
- Archived: 2 posts and 7 videos, listed in https://postcutoff.com/e/2026-07-24-claude-opus-5/index.json