Herb in Rails 8.2: Your ERB views, now HTML-aware @ Rails World 2026, Austin, Texas

With teams, companies, and open source projects adopting Herb in their daily workflows, the foundation is proving itself at scale and is on track to become an opt-in view engine in Rails 8.2.

This talk explores what Herb brings to Rails: how it integrates with ActionView and the tooling and developer experience every Rails developer gains as a result.

But that's only the beginning. To complete the Hotwire story, Rails needs reactivity.

Herb's understanding of HTML and ERB makes this possible. I'll introduce the first production-ready version of ReActionView, bringing Phoenix LiveView-like fine-grained reactivity to standard Rails templates. Fully optional. Gradual to adopt. No JavaScript framework. No new file format.

Your HTML+ERB templates, now reactive.

1. Marco Roth Herb in Rails 8.2: Your ERB views, now HTML-aware Sep 24, 2026 - Rails World 2026, Austin, Texas
2. 🌐 marcoroth.dev Marco Roth ! Full-Stack Developer & Open Source Contributor  @marcoroth  @marcoroth@ruby.social  @marcoroth_  @marcoroth.dev
4. Developer Tooling & Developer Experience
5. Herb
7. Marco Roth Herb in Rails 8.2: Your ERB views, now HTML-aware Sep 24, 2026 - Rails World 2026, Austin, Texas
8. What is Herb?
9. What is Herb? What ships in Rails 8.2?
10. What is Herb? What ships in Rails 8.2? What does this enable?
11. What is Herb?
12. A modern templating language for the HTML+ERB you already have.
13. One language and toolchain that understands your HTML and Ruby together.
14. Herb has full semantic and structural understanding of your HTML views.
15. Linter Formatter Language Server Engine Dev Tools Dev Server
19. herb dev
22. Herb helps you in development, in your editor, in CI, and when rendering your views.
23. What ships in Rails 8.2?
24. Action View
25. Herb? Action View
26. index.html.erb
27. index.html.erb action
28. index.html.erb action format
29. index.html.erb action format handler
30. Herb is the new default for the HTML format
31. format == :html && handler == :erb
32. *.html.erb → Herb
33. *.html.erb → Herb *.****.erb → Erubi
34. bin/rails herb:check
35. config.action_view .erb_implementation=
36. config/application.rb config.load_defaults 8.2
37. Rails 8.2 defaults .erb_implementation = :herb
38. Restore previous behavior .erb_implementation = :erubi
40. LSP features
41. Find all references Workspaces Support Hover Previews Extract to Partial Cross File Diagnostics
42. Runtime Instrumentation
43. ActiveSupport::Notifications .subscribe("sql.active_record") do |*, payload| Herb::Engine::Report::Session.observe( :queries, payload ) end
44. Runtime Diagnostics
48. LSP Runtime Inlay Hints
52. 68 new linter rules
54. 166 linter rules
57. https://herb-tools.dev/blog/whats-new-in-herb-v0-11
58. What does this enable?
59. The Herb foundation is available in all new apps
60. The Compiler as a Platform
61. One-Person Framework
62. Rails 7 brought a lot of simplification with Hotwire
63. HTML-over-the-wire
64. Rails 8 brought a lot of simplification with the Solid Trifecta
65. The View Layer in Rails doesn't scale the same way as the rest of the framework does.
66. What becomes possible when the engine and runtime also understand HTML?
67. How can we evolve Hotwire so you can build competitive, modern, and ambitious UIs?
68. What does it take to complete the Hotwire story?
69. Reactivity
70. Fine-grained reactivity
71. The design goal for Herb tooling was to be fully backwards compatible for existing HTML+ERB files
72. I was curious if we can do the same for templating, reactivity, and interactivity.
73. I wanted to explore if there is a way how I can revisit some of the old and untapped ideas from StimulusReflex
76. ActionView
77. ActionView Reimagined
78. ActionView Reimagined Reengineered
79. ActionView Reimagined Reengineered Reactive
82. ReActionView v0.6
83. Reactivity for the HTML+ERB you already have.
84. Everything a clientside framework gives you, without adopting one.
85. And the best thing?
86. You already wrote a ReActionView template.
87. Your existing HTML+ERB views are now reactive.
88. 6 Adoption Levels of ReActionView
89. Level 1 - Better Errors Messages Level 2 - HTML-aware Engine Level 3 - Action View Optimizations Level 4 - Reactive ERB Views Level 5 - Client-side Templates Level 6 - External Components
90. Slots
91. <section> <h2><%= @title %></h2> <ul> <% @albums.each do |album| %> <li id="<%= album.id %>"> <%= album.name %> </li> <% end %> </ul> </section>
92. <section> <h2><%= @title %></h2> <ul> <% @albums.each do |album| %> <li id="<%= album.id %>"> <%= album.name %> </li> <% end %> </ul> </section>
93. <section> <h2><%= @title %></h2> <ul> <% @albums.each do |album| %> <li id="<%= album.id %>"> <%= album.name %> </li> <% end %> </ul> </section>
94. <section> <h2><%= @title %></h2> <ul> <% @albums.each do |album| %> <li id="<%= album.id %>"> <%= album.name %> </li> <% end %> </ul> </section>
95. Herb fully understands what the view is doing
96. So we can compile the template into two formats to support reactivity.
97. One for the regular render, and one for this new slots format
98. <h2>Hello, <%= @title %>!</h2>
99. <h2>Hello, Rails World!</h2>
100. <h2>Hello, Rails World!</h2>
101. <h2> Hello, <!--herb-slot:1-->Rails World<!--/herb-slot:1-->! </h2>
102. <h2> Hello, <!--herb-slot:1-->Rails World<!--/herb-slot:1-->! </h2>
103. <!--herb-region:test.html.erb--> <h2> Hello, <!--herb-slot:1-->Rails World<!--/herb-slot:1-->! </h2> <!--/herb-region:test.html.erb-->
104. <!--herb-region:test.html.erb--> <h2> Hello, <!--herb-slot:1-->Austin<!--/herb-slot:1-->! </h2> <!--/herb-region:test.html.erb-->
105. Both the server and the client have a map of where the dynamic slot values go
106. Wherever new values come from, the client knows how to update it.
107. ERB Output Collections/Loops Conditionals
108. No page reloads. No DOM-morphing.
109. <div class="container"> <%= Time.now %> </div>
110. <div class="container"> <%= Time.now %> <button data-herb-action="$refresh">Refresh</button> </div>
111. <div class="container"> <%= Time.now %> <button data-herb-action="$refresh">Refresh</button> </div>
112. GET /demo Accept: application/vnd.herb.slots+json
113. def show end
114. def show respond_to do |format| format.html end end
115. def show respond_to do |format| format.html format.slots end end
116. GET /demo Accept: application/vnd.herb.slots+json { "template": "app/views/demo/show.html.erb", "version": "ddfca612", "occurrence": 0, "slots": { "0": "2026-09-24 12:14:38 +0200" } }
117. GET /demo Accept: application/vnd.herb.slots+json { "template": "app/views/demo/show.html.erb", "version": "ddfca612", "occurrence": 0, "slots": { "0": "2026-09-24 12:14:38 +0200" } }
118. State
119. Not every UI interaction should require a serverroundtrip
120. Typically you would reach for Stimulus
121. But, what if you could just write this in ERB?
122. <button>Show Details</button> <% if show? %> <span>Here are the details!</span> <% end %>
123. <%# herb:state (show: false) %> <button>Show Details</button> <% if show? %> <span>Here are the details!</span> <% end %>
124. <%# herb:state (show: false) %> <button data-herb-set="click->show=true">Show Details</button> <% if show? %> <span>Here are the details!</span> <% end %>
125. <%# herb:state (show: false) %> <button data-herb-set="show=true">Show Details</button> <% if show? %> <span>Here are the details!</span> <% end %>
126. <%# herb:state (show: false) %> <button data-herb-set="show=true">Show Details</button> <% if show? %> <span>Here are the details!</span> <% end %>
127. <%# herb:state (show: false) %> <button data-herb-toggle="show">Show Details</button> <% if show? %> <span>Here are the details!</span> <% end %>
128. data-herb-set data-herb-action data-herb-toggle data-herb-increment data-herb-decrement
129. Two-way bindings
130. <input value="<%= message %>">
131. <%# herb:state (message: "") %> <input value="<%= message %>">
132. You now got a twoway binding
133. <%# herb:state (message: "") %> <input value="<%= message %>"> <p><%= message.length %> characters</p>
134. No network request needed
135. No custom JavaScript needed
136. Just pure understanding and efficient updates
137. No Ruby to JavaScript transpilation
138. So we don't need to run Ruby in WebAssembly in the browser
139. ReActionView sees all the methods that are being called on a herb:state local variable
140. The compiler understands a subset of Ruby that it can wire into the reactivity model
141. That way, it can run fully client-side without a server round-trip
142. For everything the compiler doesn't support, we do a network request
143. <%# herb:state (q: "") %> <input value="<%= q %>"> <% if q.present? %> <p><%= Topic.search(q).count %> results</p> <% end %>
144. The compiler prepares the view in a way so the client knows on which state change it has to rerequest the data
145. When the client has to request it, the server knows how to respond
146. and the client knows how to update and insert the new dynamic slot values
147. No Turbo Frames No Turbo Streams No new route
148. Just pure understanding of the view and finegrained reactivity.
149. Lazy Loading
150. <p><%= Stats.slow_query %></p>
151. <Async> <p><%= Stats.slow_query %></p> </Async>
152. <Async> <p><%= Stats.slow_query %></p> <Fallback> <p class="skeleton">&nbsp;</p> </Fallback> </Async>
153. <Lazy> <p><%= Stats.slow_query %></p> <Fallback> <p class="skeleton">&nbsp;</p> </Fallback> </Lazy>
155. Open to feedback about naming
157. Optimistic UI
159. You can do a lot with pure ERB
160. If you need to, there is a JavaScript API you can use to interact with the client runtime directly
161. Which also allows to build even more ambitious UIs, or allows to wire up NPM packages
162. bundle add reactionview rails generate reactionview:install
163. reactionview.dev demo.reactionview.dev
164. Outlook/Vision
165. <style scoped>
166. lightningcss-ruby
167. <script scoped>
168. oxc-ruby
169. rolldown-ruby
170. Offline Mode React Components Herb Components for gems Client-side routing
171. Conclusion
172. I'm really happy with the direction Herb and ReActionView are taking and how they are shaping up
173. And, how we can go back to just keep writing ERB views and get fully reactive UIs
174. I believe that this offers a great foundation for the future of the Rails frontend
175. The idea is to offer a spectrum for teams to adopt
176. Expand what's possible with Hotwire today
177. Allow people to write more JavaScript if the application needs it
178. And in case you'd want to use React or existing components, that you still have a way to use them alongside your ERB views
179. Without having to abandon the full-stack approach that makes Rails so special
181. ReActionView has become what I always wanted StimulusReflex to be
182. But I'm sure there are more things we can do, improve, and iterate on.
183. But I can't do it all by myself, I need your input.
184. I would love to talk to you if you have ideas or opinions about the things I have shown today.
185. Or if you are still skeptical and have questions on where things are heading
186. I would love your input and feedback
187. Acknowledgments
190.  github.com/sponsors/marcoroth
191. Thank you for the continued support!
192. Please try the tools, report issues, and give feedback.
195. herb-tools.dev reactionview.dev
198. Thank you "  @marcoroth 🌐 marcoroth.dev  @marcoroth_  @marcoroth.dev  @marcoroth@ruby.social  /in/marco-roth