--- title: I recreated Fable 5 with Opus and agent loops, and it's... description: After Anthropic's Fable 5 model was banned by the U.S. government over national security concerns, the author found a workable alternative using Claude Opus... canonical: https://daily.dev/posts/i-recreated-fable-5-with-opus-and-agent-loops-and-it-s-close-enough-that-i-stopped-missing-the-bann-8iuunavyj twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: I recreated Fable 5 with Opus and agent loops, and it's close enough that I stopped missing the banned model | daily.dev og:description: After Anthropic's Fable 5 model was banned by the U.S. government over national security concerns, the author found a workable alternative using Claude Opus... og:url: https://daily.dev/posts/i-recreated-fable-5-with-opus-and-agent-loops-and-it-s-close-enough-that-i-stopped-missing-the-bann-8iuunavyj og:image: https://api.daily.dev/og/posts/8iuUnavyj.png og:image:alt: I recreated Fable 5 with Opus and agent loops, and it's close enough that I stopped missing the banned model og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # I recreated Fable 5 with Opus and agent loops, and it's close enough that I stopped missing the banned model **[XDA Developers](https://daily.dev/sources/xda-developers)** · 4 min read · 7 upvotes · 0 comments ## Summary After Anthropic's Fable 5 model was banned by the U.S. government over national security concerns, the author found a workable alternative using Claude Opus 4.8 combined with the Ralph Loop plugin for agent loops. The Ralph Loop plugin enables iterative execution workflows in Claude Code, allowing the model to repeatedly revisit objectives until completion rather than treating tasks as single request-response cycles. The author estimates this combination delivers about 80% of Fable 5's capabilities, and recommends structuring prompts into milestones and using detailed, structured commands to maximize Opus 4.8's output. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is the Ralph Loop plugin for Claude Code? Ralph Loop is an Anthropic-developed plugin that gives Claude Code an iterative execution workflow instead of a single request-response cycle. Claude creates a plan, works through it, reviews the output, updates its approach, and keeps going until it reaches a predefined completion signal, allowing longer, more autonomous task execution. _Developers building longer autonomous coding workflows can follow agent-loop tooling updates like this on daily.dev._ ### Why was Anthropic's Fable 5 model taken offline? Fable 5, a derivative of Anthropic's Mythos model previously deemed too dangerous to release, was restricted by the U.S. government days after launch over national security concerns, prompting Anthropic to disable it worldwide. Users who had access described it as noticeably more capable than Opus 4.8 or GPT-5.5, especially at completing tasks without hand-holding. _Track how access to powerful AI coding models changes on daily.dev before it affects your workflow._ ### Can Opus 4.8 replace Fable 5 for agentic coding tasks? Opus 4.8 combined with an agent loop like Ralph Loop can reportedly reach about 80% of what made Fable 5 special, though it is not identical. Structuring work into milestones, reviewing output after each one, and using detailed, structured prompts helps close the gap versus giving Opus a single broad instruction. _Compare model and workflow combinations for agentic coding tasks on daily.dev before committing to one._ ## Similar posts on daily.dev - [Anthropic’s Opus 5 is almost Fable 5](https://daily.dev/posts/anthropic-s-opus-5-is-almost-fable-5-vlen80a1c) · The New Stack · 9 upvotes · 2 comments --- Tags: [#ai-coding](https://daily.dev/tags/ai-coding), [#claude](https://daily.dev/tags/claude), [#prompt-engineering](https://daily.dev/tags/prompt-engineering), [#claude-code](https://daily.dev/tags/claude-code) [View this post on daily.dev](https://daily.dev/posts/i-recreated-fable-5-with-opus-and-agent-loops-and-it-s-close-enough-that-i-stopped-missing-the-bann-8iuunavyj) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"I recreated Fable 5 with Opus and agent loops, and it's close enough that I stopped missing the banned model","url":"https://daily.dev/posts/i-recreated-fable-5-with-opus-and-agent-loops-and-it-s-close-enough-that-i-stopped-missing-the-bann-8iuunavyj","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/i-recreated-fable-5-with-opus-and-agent-loops-and-it-s-close-enough-that-i-stopped-missing-the-bann-8iuunavyj"},"datePublished":"2026-06-20T14:32:44.069Z","dateModified":"2026-09-13T20:25:56.863Z","description":"After Anthropic's Fable 5 model was banned by the U.S. government over national security concerns, the author found a workable alternative using Claude Opus...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/cdc224e0364021a22f74f655d5c37308?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/cdc224e0364021a22f74f655d5c37308?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"XDA Developers","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"XDA Developers","logo":"https://media.daily.dev/image/upload/s--kCg6yyAP--/f_auto,q_auto/v1774964407/logos/xda-developers?_a=BAMAMiWQ0","url":"https://daily.dev/sources/xda-developers"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/i-recreated-fable-5-with-opus-and-agent-loops-and-it-s-close-enough-that-i-stopped-missing-the-bann-8iuunavyj","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":7},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"ai-coding,claude,prompt-engineering,claude-code","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"XDA Developers","item":"https://daily.dev/sources/xda-developers"},{"@type":"ListItem","position":3,"name":"I recreated Fable 5 with Opus and agent loops, and it's close enough that I stopped missing the banned model"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/i-recreated-fable-5-with-opus-and-agent-loops-and-it-s-close-enough-that-i-stopped-missing-the-bann-8iuunavyj#faq","mainEntity":[{"@type":"Question","name":"What is the Ralph Loop plugin for Claude Code?","acceptedAnswer":{"@type":"Answer","text":"Ralph Loop is an Anthropic-developed plugin that gives Claude Code an iterative execution workflow instead of a single request-response cycle. Claude creates a plan, works through it, reviews the output, updates its approach, and keeps going until it reaches a predefined completion signal, allowing longer, more autonomous task execution. Developers building longer autonomous coding workflows can follow agent-loop tooling updates like this on daily.dev."}},{"@type":"Question","name":"Why was Anthropic's Fable 5 model taken offline?","acceptedAnswer":{"@type":"Answer","text":"Fable 5, a derivative of Anthropic's Mythos model previously deemed too dangerous to release, was restricted by the U.S. government days after launch over national security concerns, prompting Anthropic to disable it worldwide. Users who had access described it as noticeably more capable than Opus 4.8 or GPT-5.5, especially at completing tasks without hand-holding. 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