--- title: Carl Lerche's Topcoat 0.9 is the Rails-for-Rust bet... description: Carl Lerche, a former Rails core contributor, has released version 0.9 of Topcoat, a batteries-included full-stack Rust web framework positioned as a... canonical: https://daily.dev/posts/carl-lerche-s-topcoat-0-9-is-the-rails-for-rust-bet-dhh-s-keynote-accidentally-started-98lj9z3p7 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Carl Lerche's Topcoat 0.9 is the Rails-for-Rust bet DHH's keynote accidentally started | daily.dev og:description: Carl Lerche, a former Rails core contributor, has released version 0.9 of Topcoat, a batteries-included full-stack Rust web framework positioned as a... og:url: https://daily.dev/posts/carl-lerche-s-topcoat-0-9-is-the-rails-for-rust-bet-dhh-s-keynote-accidentally-started-98lj9z3p7 og:image: https://api.daily.dev/og/posts/98lJ9z3p7.png og:image:alt: Carl Lerche's Topcoat 0.9 is the Rails-for-Rust bet DHH's keynote accidentally started 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. # Carl Lerche's Topcoat 0.9 is the Rails-for-Rust bet DHH's keynote accidentally started **[Trends](https://daily.dev/sources/trends)** · 2 min read · 4 upvotes · 0 comments ## Summary Carl Lerche, a former Rails core contributor, has released version 0.9 of Topcoat, a batteries-included full-stack Rust web framework positioned as a Rails-style alternative to WebAssembly-based frameworks like Leptos and Dioxus. Topcoat compiles client-side code to JavaScript rather than WASM, defaults to server-side rendering with opt-in reactivity via 'shard' functions, and streams live updates over WebSockets using `live!` and `emit!` macros. Its ORM, Toasty, gained an `update!` macro for atomic updates, JSONB support in PostgreSQL, and polymorphic relations via enums. Community reaction is mixed: reviewers like the approachable syntax and simpler mental model, but WASM advocates argue Leptos still wins for canvas-heavy or fully client-side Rust apps, calling Topcoat a good starting point rather than a replacement. ## Content DHH's keynote apparently lit a fuse. Carl Lerche — former Rails core contributor — used the fallout to explain why he's building Topcoat, a batteries-included full-stack Rust web framework that just shipped v0.9. The timing is deliberate. The framing is pointed. The 0.9 release is genuinely interesting. Topcoat takes a different bet than Leptos or Dioxus: it compiles client-side code to JavaScript instead of WebAssembly. That's a philosophical choice as much as a technical one. The framework defaults to server-side rendering with opt-in reactivity — think HTMX-style server round trips via "shard" functions — rather than pushing you toward a full SPA. Live updates stream through WebSockets using `live!` and `emit!` macros, with suspense-like loading states built in. The ORM layer, Toasty, also got real work: an `update!` macro for atomic field updates, first-class JSONB support in PostgreSQL, and a polymorphic relations pattern using enums. The community reaction is split in a familiar way. Reviewers praise Topcoat's approachability — the view macro syntax is clean, the mental model is simple, and it's genuinely friendlier to newcomers than the Leptos/Dioxus ecosystem. But the JS compilation target is where people pump the brakes. Leptos loyalists point out that WebAssembly still wins for canvas-heavy apps and anything needing full client-side Rust. The conclusion from most reviewers: good starting point, not yet a replacement. What's actually interesting here is the positioning. Lerche isn't trying to out-Leptos Leptos. He's making a Rails argument in Rust — convention over configuration, server-first, real-time as a first-class feature rather than an afterthought. Whether that resonates depends entirely on whether you think the Rust web ecosystem needs another WASM framework or a different kind of framework entirely. The DHH connection gives this a sharper edge than a typical framework release. Lerche is explicitly entering a conversation about what "full-stack" should mean, and Topcoat is his answer. ## Questions this post answers ### What is Topcoat 0.9 and how does it differ from Leptos or Dioxus? Topcoat 0.9 is a full-stack Rust web framework built by former Rails core contributor Carl Lerche that compiles client-side code to JavaScript instead of WebAssembly, unlike Leptos or Dioxus. It defaults to server-side rendering with opt-in reactivity through 'shard' functions, HTMX-style server round trips, and live updates over WebSockets via `live!` and `emit!` macros with built-in suspense-like loading states. _Developers weighing Rust web framework options can follow releases like this one on daily.dev._ ### What new ORM features shipped with Topcoat 0.9's Toasty layer? Toasty, Topcoat's ORM, added an `update!` macro for atomic field updates, first-class JSONB support in PostgreSQL, and a polymorphic relations pattern implemented using enums in version 0.9. These changes strengthen the ORM's database capabilities alongside the broader framework release. _Anyone tracking Rust ORM capabilities can keep up with changes like these on daily.dev._ ### Is Topcoat a replacement for Leptos in the Rust web ecosystem? Not yet, according to most reviewers. Topcoat is considered more approachable for newcomers with a cleaner view macro syntax and simpler mental model, but WebAssembly still outperforms it for canvas-heavy applications and anything requiring full client-side Rust, since Topcoat compiles to JavaScript rather than WASM. _Developers deciding between Rust web frameworks can compare tradeoffs like these on daily.dev._ ## Similar posts on daily.dev - [Announcing Topcoat: a framework for building full-stack reactive web apps with Rust](https://daily.dev/posts/announcing-topcoat-a-framework-for-building-full-stack-reactive-web-apps-with-rust-rfcymwhic) · Tokio · 20 upvotes · 1 comments - [GitHub - tokio-rs/topcoat: A batteries-included framework for building web apps](https://daily.dev/posts/github---tokio-rs-topcoat-a-batteries-included-framework-for-building-web-apps-vvuisd732) · Hacker News · 4 upvotes · 0 comments --- Tags: [#rust](https://daily.dev/tags/rust), [#webassembly](https://daily.dev/tags/webassembly) [View this post on daily.dev](https://daily.dev/posts/carl-lerche-s-topcoat-0-9-is-the-rails-for-rust-bet-dhh-s-keynote-accidentally-started-98lj9z3p7) ```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":"Carl Lerche's Topcoat 0.9 is the Rails-for-Rust bet DHH's keynote accidentally started","url":"https://daily.dev/posts/carl-lerche-s-topcoat-0-9-is-the-rails-for-rust-bet-dhh-s-keynote-accidentally-started-98lj9z3p7","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/carl-lerche-s-topcoat-0-9-is-the-rails-for-rust-bet-dhh-s-keynote-accidentally-started-98lj9z3p7"},"datePublished":"2026-09-24T20:07:34.655Z","dateModified":"2026-09-24T20:08:18.409Z","description":"Carl Lerche, a former Rails core contributor, has released version 0.9 of Topcoat, a batteries-included full-stack Rust web framework positioned as a...","isAccessibleForFree":true,"articleSection":"Trends","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":"Trends","logo":"https://media.daily.dev/image/upload/s--ZfSp3asX--/f_auto,q_auto/v1780996004/logos/trends?_a=BAMAMiWQ0","url":"https://daily.dev/sources/trends"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/carl-lerche-s-topcoat-0-9-is-the-rails-for-rust-bet-dhh-s-keynote-accidentally-started-98lj9z3p7","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":4},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"rust,webassembly","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Trends","item":"https://daily.dev/sources/trends"},{"@type":"ListItem","position":3,"name":"Carl Lerche's Topcoat 0.9 is the Rails-for-Rust bet DHH's keynote accidentally started"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/carl-lerche-s-topcoat-0-9-is-the-rails-for-rust-bet-dhh-s-keynote-accidentally-started-98lj9z3p7#faq","mainEntity":[{"@type":"Question","name":"What is Topcoat 0.9 and how does it differ from Leptos or Dioxus?","acceptedAnswer":{"@type":"Answer","text":"Topcoat 0.9 is a full-stack Rust web framework built by former Rails core contributor Carl Lerche that compiles client-side code to JavaScript instead of WebAssembly, unlike Leptos or Dioxus. 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