fix(rails): make Action Cable handle_open/handle_close overrides public for Rails 8.2

[kylekeesling]

Description

Rails 8.2 decoupled the Action Cable connection from the socket in rails/rails#50979 (merged 2026-05-28): ActionCable::Server::Socket now invokes connection.handle_open and connection.handle_close from outside the connection object.

Sentry::Rails::ActionCableExtensions::Connection declares its handle_open/handle_close overrides as private, which shadows the (public) framework methods through the prepend chain. On Rails main / 8.2, every cable connection then raises:

NoMethodError (private method 'handle_open' called for an instance of ApplicationCable::Connection)
  actioncable/lib/action_cable/server/socket.rb:127:in 'ActionCable::Server::Socket#handle_open'

before the welcome message is sent. The practical effect is severe and silent: the WebSocket upgrade succeeds (101), but clients never receive welcome or pings, so they treat the connection as stale and reconnect in a loop forever — no broadcasts (e.g. Turbo Streams) are ever delivered. The exception only hits the Rails logger, not Sentry, since it occurs in the instrumentation wrapper itself.

We hit this in production on a Rails edge app with sentry-rails 6.6.0 and confirmed the root cause by inspecting method visibility:

ApplicationCable::Connection.instance_method(:handle_open).owner
# => Sentry::Rails::ActionCableExtensions::Connection
ApplicationCable::Connection.private_method_defined?(:handle_open)
# => true

Fix

Make the two overrides public. On Rails < 8.2 they are only invoked internally on self (visibility is irrelevant there), so this is safe across all supported Rails versions. Added a regression spec asserting the visibility and a changelog entry.

bundle exec rspec spec/sentry/rails/action_cable_spec.rb → 12 examples, 0 failures.

[kaushgem]

Independently confirmed on Rails main (8.2.0.alpha, rev 324b65c2dffe) with sentry-rails 6.6.1 / Ruby 4.0.1. Every /cable upgrade raises:

NoMethodError: private method 'handle_open' called for an instance of ApplicationCable::Connection
  actioncable/lib/action_cable/server/socket.rb:127:in 'handle_open'

The upgrade returns 101, but handle_open raises in the instrumentation wrapper, so the client never gets welcome and no Turbo Stream / presence broadcasts are delivered — in every environment. Making the overrides public fixes it. Full repro in #2975. Would love to see this land 🙏

[solnic]

Thanks for tackling this. I left some comments but let's hold off with this until we have a beta released, so that we can add it to the CI matrix, which would help over here.

[solnic]

We need to do this conditionally, otherwise on older Rails version we'd be changing method visibility, and that would be an unwanted side-effect.

[solnic]

This tests implementation details. I assume that under Rails 8.2 some of our specs would fail, right? If they do, then this test is redundant, if they don't, then it would be good to reproduce the issue under 8.2 by exercising the actual behavior that Sentry adds.

[solnic]

No need to update this as CHANGELOG is now updated automatically during the release process 🪄