[AINews] Claude Opus 5: Fable-level performance at Opus price (half Fable)

In a rare Friday release, Opus 5 took the headlines today. Athrough most of its official benchmarks have it technically beating Fable, the official messaging still says it “comes close”. This mostly reflects the difficulty of Evals - today’s AIE track drop - not reflecting “big model smell” that Anthropic obviously knows Fable retains but can’t measure.Fortunately, independent evaluations of Opus confirm the outperformance:@AnthropicAI has released Claude Opus 5, the new leader on the Artificial Analysis Intelligence Index, and ","username":"ArtificialAnlys","name":"Artificial Analysis","profile_image_url":"https://pbs.substack.com/profile_images/2042402069320290304/A8C1lP07_normal.jpg","date":"2026-07-24T22:10:41.000Z","photos":[{"img_url":"https://pbs.substack.com/media/HOBjK6cbIAA2Yph.jpg","link_url":"https://t.co/SFuDwqY6XE"}],"quoted_tweet":{},"reply_count":16,"retweet_count":45,"like_count":451,"impression_count":34514,"expanded_url":null,"video_url":null,"video_preview_media_key":null,"belowTheFold":false}" data-component-name="Twitter2ToDOM">And the improved efficiency story, beyond just pricing, is also important… although it only just matches GPT 5.6 Sol:AI News for 7/23/2026-7/24/2026. We checked 12 subreddits, 544 Twitters and no further Discords. AINews’ website lets you search all past issues. As a reminder, AINews is now a section of Latent Space. You can opt in/out of email frequencies!AI Twitter RecapTop Story: Claude Opus 5 model launchWhat happenedAnthropic’s Claude Opus 5 launch triggered a mix of benchmark scrutiny, strong anecdotal coding-agent praise, and renewed debate about frontier model evaluation.Multiple tweets explicitly discuss Claude Opus 5 as a newly launched model and compare it to other frontier systems on coding and general capability metrics, including Epoch’s ECI assessment, a FrontierCode anomaly discussion, and early user reactions from tool-use workflows like browser automation @abacaj, @abacaj.Epoch reported that Claude Opus 5 achieves an ECI of 159, “slightly below Fable 5’s value of 161,” while matching Fable 5 on SWE-ECI at 161 on software engineering benchmarks @EpochAIResearch.The ECI result immediately drew criticism from users who felt the score understated Opus 5’s practical improvements; one response called it “incredibly underrated,” noting it appears only 1 point better than Opus 4.8 despite seeming “much better at everything” in practice @scaling01. The same user argued for harder public benchmarks @scaling01.A separate thread highlighted an apparent benchmark irregularity: Opus 5 scored better on FrontierCode at medium effort than at higher effort, even though more effort improved performance on other evals @jerhadf. That suggests either task-specific search/effort tradeoffs or evaluation instability rather than monotonic gains from extra inference-time compute.Several technically literate users praised Opus 5’s coding performance. Mikhail Parakhin @MParakhin—said “Best-of-n rules” and reported a clear head-to-head win against Fable “for math and everything, really,” while wishing it were available in Codex.Arena promoted first impressions of Opus 5 and said leaderboard scores based on real-world use were coming soon @arena, indicating community evals were still catching up at posting time.Nous Research’s portal added access to the model, with a tweet saying users could directly use Opus 5 through Nous Portal and that a 20% discount applied to all models including Opus 5 @witcheer. This is distribution/availability rather than a capability claim.User anecdotes emphasized browser control / agentic tool use. One post said Opus 5 opened the browser and canceled a ChatGPT Pro subscription @abacaj, followed by “This thing can really drive a browser wow” @abacaj. These are isolated demos, not systematic evals, but they