HTML report truncated at `window.CUCUMBER_MESSAGES = [`

[oellul]

👓 What did you see?

The generated HTML report ends with this line:

<script>
window.CUCUMBER_MESSAGES = [

✅ What did you expect to see?

window.CUCUMBER_MESSAGES array should be populated:

<script>
window.CUCUMBER_MESSAGES = [
{"meta":{"protocolVersion":"32.3.1","implementation":{"name":"cucumber-ruby","version":"11.1.0"},"runtime":{"name":"ruby","version":"4.0.5"},"os":{"name":"linux","version":"#1 SMP PREEMPT_DYNAMIC Sun, 17 May 2026 17:23:07 +0000"},"cpu":{"name":"x86_64"}}},
...
]
</script>

📦 Which tool/library version are you using?

ruby v4.0.5
cucumber-ruby v11.1.0
linux

🔬 How could we reproduce it?

1. Setup a blank project
2. Add Gemfile

# frozen_string_literal: true

source 'https://rubygems.org'

gem 'cucumber'

3. Add basic feature file: features/feature/test.feature

Feature: Test

  Scenario: Run a step
    When I run a single step

4. Add step definition: features/step_definitions/test.rb

# frozen_string_literal: true

When('I run a single step') do
  expect(1).to eq(1)
end

5. Run bundle install
6. Run bundle exec cucumber --format html --out report.html

📚 Any additional context?

I found that the probable cause was that output_envelope is defined but not subscribed to the :envelope event

I am working around the issue with this monkey-patch:
features/support/html_formatter_fix.rb

# frozen_string_literal: true

require 'cucumber/formatter/html'

module Cucumber
  module Formatter
    class HTML
      alias _bugfix_original_initialize initialize

      def initialize(config)
        _bugfix_original_initialize(config)
        config.on_event(:envelope) do |event|
          envelope = event.envelope
          @html_formatter.write_message(envelope)
          @html_formatter.write_post_message if envelope.test_run_finished
        end
      end
    end
  end
end

[luke-hill]

I can see the issue. Actually a slightly better fix is to just override on_envelope in the HTML formatter proper. I'll get working on a fix soon. Sorry for this oversight.