--- title: Can Claude Fable 5.1 Build a Real App in One Prompt? description: A creator rebuilds a habit-tracker iOS app with Claude Opus/Sonnet 5.1 (the transcript garbles the name as 'Fable 5.1') using the same prompt, MCP servers, and... canonical: https://daily.dev/posts/can-claude-fable-5-1-build-a-real-app-in-one-prompt--jr2liwq9n twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Can Claude Fable 5.1 Build a Real App in One Prompt? | daily.dev og:description: A creator rebuilds a habit-tracker iOS app with Claude Opus/Sonnet 5.1 (the transcript garbles the name as 'Fable 5.1') using the same prompt, MCP servers, and... og:url: https://daily.dev/posts/can-claude-fable-5-1-build-a-real-app-in-one-prompt--jr2liwq9n og:image: https://api.daily.dev/og/posts/JR2LIWq9N.png og:image:alt: Can Claude Fable 5.1 Build a Real App in One Prompt? 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. # Can Claude Fable 5.1 Build a Real App in One Prompt? **[Code with Beto](https://daily.dev/sources/codewithbeto)** · 12 min read · 1 upvotes · 0 comments ## Summary A creator rebuilds a habit-tracker iOS app with Claude Opus/Sonnet 5.1 (the transcript garbles the name as 'Fable 5.1') using the same prompt, MCP servers, and plan as a prior Claude 5 attempt, to test whether the new release is actually cheaper and better at agentic coding. Anthropic kept per-token pricing the same ($10 in/$50 out per million tokens) but claims roughly 25% cheaper real-world costs due to a 75% improvement in caching, plus stronger agentic coding performance at lower reasoning effort. The build used Expo, native UI components, a widget, an app icon skill, and iOS simulator testing via MCP. This run cost $33 versus about $50 previously, took about 40 minutes, and succeeded on the first try including a working widget, whereas the earlier attempt had a broken widget. The video also mentions Claude Opus 5.1 ('Mythos 5.1') being used experimentally for protein binder design and a new high-resolution Venus radar map, and includes a paid promotion for the creator's mobile app development book. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How much cheaper is Claude Opus 5.1 compared to Claude Opus 5 for agentic coding tasks? Anthropic states per-token pricing stayed the same at $10 per million input tokens and $50 per million output tokens, but real-world costs drop by about 25% overall due to a 75% improvement in prompt caching, with savings reaching closer to 45-50% on long agentic coding sessions that read a lot of context. _Track real-world cost changes across model releases like this one on daily.dev before budgeting your next agentic coding session._ ### Does Claude 5.1 perform better than Claude 5 at agentic coding with lower reasoning effort? Yes, Claude 5.1 running with low reasoning effort reportedly matches the results that Claude 5 achieved with max or high thinking effort, while also performing better overall. This means agentic coding sessions can use a cheaper, lower-effort setting and still get comparable or improved outcomes compared to the prior model. _Compare agentic coding model upgrades like this on daily.dev before deciding which reasoning tier to run._ ### How much did it cost to build a full React Native habit tracker app with a working iOS widget using Claude 5.1? Building a complete habit tracker app in Expo/React Native with native components, a home screen widget, custom app icon, dark mode, haptics, and local storage cost $33 in usage credits and took about 40 minutes using Claude Opus 5.1 with an MCP server for UI examples. A prior attempt with Claude 5 on the same app and prompt cost about $50 and produced a broken widget. _See real cost breakdowns like this one on daily.dev when scoping how much an AI-built mobile app might run you._ --- Tags: [#react-native](https://daily.dev/tags/react-native), [#mcp](https://daily.dev/tags/mcp), [#claude](https://daily.dev/tags/claude), [#vibe-coding](https://daily.dev/tags/vibe-coding) [View this post on daily.dev](https://daily.dev/posts/can-claude-fable-5-1-build-a-real-app-in-one-prompt--jr2liwq9n) ```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":"Can Claude Fable 5.1 Build a Real App in One Prompt?","url":"https://daily.dev/posts/can-claude-fable-5-1-build-a-real-app-in-one-prompt--jr2liwq9n","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/can-claude-fable-5-1-build-a-real-app-in-one-prompt--jr2liwq9n"},"datePublished":"2026-09-03T11:02:49.909Z","dateModified":"2026-09-03T11:03:53.048Z","description":"A creator rebuilds a habit-tracker iOS app with Claude Opus/Sonnet 5.1 (the transcript garbles the name as 'Fable 5.1') using the same prompt, MCP servers, and...","image":"https://i.ytimg.com/vi/9V2ZFhLsh9w/sddefault.jpg","thumbnailUrl":"https://i.ytimg.com/vi/9V2ZFhLsh9w/sddefault.jpg","isAccessibleForFree":true,"articleSection":"Code with Beto","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":"Code with Beto","logo":"https://media.daily.dev/image/upload/s--8oKUFd2X--/f_auto,q_auto/v1774179046/logos/codewithbeto?_a=BAMAMiWQ0","url":"https://daily.dev/sources/codewithbeto"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/can-claude-fable-5-1-build-a-real-app-in-one-prompt--jr2liwq9n","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"react-native,mcp,claude,vibe-coding","timeRequired":"PT12M","video":{"@type":"VideoObject","name":"Can Claude Fable 5.1 Build a Real App in One Prompt?","description":"A creator rebuilds a habit-tracker iOS app with Claude Opus/Sonnet 5.1 (the transcript garbles the name as 'Fable 5.1') using the same prompt, MCP servers, and...","thumbnailUrl":"https://i.ytimg.com/vi/9V2ZFhLsh9w/sddefault.jpg","uploadDate":"2026-09-03T11:02:49.909Z","duration":"PT12M","url":"https://api.daily.dev/r/JR2LIWq9N","embedUrl":"https://www.youtube.com/embed/9V2ZFhLsh9w"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Code with Beto","item":"https://daily.dev/sources/codewithbeto"},{"@type":"ListItem","position":3,"name":"Can Claude Fable 5.1 Build a Real App in One Prompt?"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/can-claude-fable-5-1-build-a-real-app-in-one-prompt--jr2liwq9n#faq","mainEntity":[{"@type":"Question","name":"How much cheaper is Claude Opus 5.1 compared to Claude Opus 5 for agentic coding tasks?","acceptedAnswer":{"@type":"Answer","text":"Anthropic states per-token pricing stayed the same at $10 per million input tokens and $50 per million output tokens, but real-world costs drop by about 25% overall due to a 75% improvement in prompt caching, with savings reaching closer to 45-50% on long agentic coding sessions that read a lot of context. 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