Note: The following is out of date. Updated recommendations here: https://h1rails.com/server_for_state

Views

Wrap your form in a div with a known id. You'll use this as your hx-target when the form is submitted.

<div id="task-form">
  <%= render partial: "partials/task_form" %>
</div>

Write your form as normal, but use hx-post instead of action, and specify a hx-target

# /views/partials/_task_form.html.erb

<div class="flex flex-col space-y-3">
  <% if @task.persisted? %>
    <div class="bg-blue-600 text-white p-5 rounded">
      Great! Your details have been saved!
    </div>
  <% else %>
    <%= render partial: "shared/form_errors", locals: { record: @task } %>
    <form hx-post="<%= new_task_path %>" hx-target="#task-form" >
      <div class="grid grid-cols-7 md:space-x-4 space-y-3 md:space-y-0">
        <div class="md:col-span-2 col-span-7">
          <label for="name-field">Name</label>
          <input class="<%= 'invalid' if @task.errors[:name].present? %>" id="name-field" type="text" placeholder="Task Name" name="task[name]" value="<%= @task.name %>" />
        </div>
        <div class="md:col-span-1 col-span-7">
          <label>&nbsp;</label>
          <input type="submit" value="Submit">
        </div>
      </div>
    </form>
  <% end %>
</div>

Controller

Add a method to your application controller that looks out for the HX-Request header and responds without the full layout.

class ApplicationController < ActionController::Base

  def support_partial_response
    if request.headers['HX-Request']
      @async_request = true
      render :layout => false
    else  
      render 
    end
  end
  
end

Now add that method to the final line of whatever controller action you'd like to support

class Tasks < ApplicationController

  def new
    if request.post?
      @task = Task.new(task_params)
      @task.save
    end
    support_partial_response
  end
  
end