A fable is a story that speaks: Latin fabula, from fari, “to speak”, and in the genre as Aesop and La Fontaine practiced it, the speaking is done by animals. An opus is a work: the crafted thing itself, named for its workmanship. Today, June 9, 2026, Anthropic released Fable 5, a new model positioned above Opus 4.8 and priced at twice Opus’s rate per token. I wanted to know, before release day ended, what that premium buys a working iOS developer. So I staged a contest of genres: four Claude Code sessions, two models at two effort levels apiece, each session given an identical request to review the codebase of Conjuguer, my French-conjugation app, and to rank what it found by impact. This post is the comparison, with tables. Being about a fable, it ends with a moral.

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Every prompt I send to Claude Code carries a hidden dial. Turn it one way and I wait twice as long, and pay nearly twice the tokens, for an answer I could have had sooner. Turn it the other way and I get a competent, forgettable response to a question that deserved judgment. The dial is called effort, and for the seven months I have used Claude Code I have never been sure where to leave it.

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I was preparing a new release of my German verb-conjugation iOS app, Konjugieren, and I noticed something strange about its on-device AI tutor. The tutor would occasionally produce a polite German refusal, “Ich kann dir keine Filmempfehlungen machen…”, and then render that refusal inside the speech bubble as if it were a verb-conjugation lesson. The user, who had asked something perfectly reasonable, would see the refusal appear in the conversation as a totally normal-looking response. There was no error and no fallback. The model had simply declined, and the app had presented the decline as if it were content.

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