*   New applications get a dependency on the new `debug` gem, replacing `byebug`.

    *Xavier Noria*

*   Add SSL support for postgresql in `bin/rails dbconsole`.

    Fixes #43114.

    *Michael Bayucot*

*   Add support for comments above gem declaration in Rails application templates, e.g. `gem("nokogiri", comment: "For XML")`.

    *Linas Juškevičius*

*   The setter `config.autoloader=` has been deleted. `zeitwerk` is the only
    available autoloading mode.

    *Xavier Noria*

*   `config.autoload_once_paths` can be configured in the body of the
    application class defined in `config/application.rb` or in the configuration
    for environments in `config/environments/*`.

    Similarly, engines can configure that collection in the class body of the
    engine class or in the configuration for environments.

    After that, the collection is frozen, and you can autoload from those paths.
    They are managed by the `Rails.autoloaders.once` autoloader, which does not
    reload, only autoloads/eager loads.

    *Xavier Noria*

*   During initialization, you cannot autoload reloadable classes or modules
    like application models, unless they are wrapped in a `to_prepare` block.
    For example, from `config/initializers/*`, or in application, engines, or
    railties initializers.

    Please check the [autoloading
    guide](https://guides.rubyonrails.org/v7.0/autoloading_and_reloading_constants.html#autoloading-when-the-application-boots)
    for details.

    *Xavier Noria*

*   While they are allowed to have elements in common, it is no longer required
    that `config.autoload_once_paths` is a subset of `config.autoload_paths`.
    The former are managed by the `once` autoloader. The `main` autoloader
    manages the latter minus the former.

    *Xavier Noria*

*   Show Rake task description if command is run with `-h`.

    Adding `-h` (or `--help`) to a Rails command that's a Rake task now outputs
    the task description instead of the general Rake help.

    *Petrik de Heus*

*   Add missing `plugin new` command to help.

    *Petrik de Heus

*   Fix `config_for` error when there's only a shared root array.

    *Loïc Delmaire*

*   Raise an error in generators if an index type is invalid.

    *Petrik de Heus*

*   `package.json` now uses a strict version constraint for Rails JavaScript packages on new Rails apps.

    *Zachary Scott*, *Alex Ghiculescu*

*   Modified scaffold generator template so that running
    `rails g scaffold Author` no longer generates tests called "creating
    a Author", "updating a Author", and "destroying a Author".

    Fixes #40744.

    *Michael Duchemin*

*   Raise an error in generators if a field type is invalid.

    *Petrik de Heus*

*   `bin/rails tmp:clear` deletes also files and directories in `tmp/storage`.

    *George Claghorn*

*   Fix compatibility with `psych >= 4`.

    Starting in Psych 4.0.0 `YAML.load` behaves like `YAML.safe_load`. To preserve compatibility
    `Rails.application.config_for` now uses `YAML.unsafe_load` if available.

    *Jean Boussier*

*   Allow loading nested locales in engines.

    *Gannon McGibbon*

*   Ensure `Rails.application.config_for` always cast hashes to `ActiveSupport::OrderedOptions`.

    *Jean Boussier*

*   Remove `Rack::Runtime` from the default middleware stack and deprecate
    referencing it in middleware operations without adding it back.

    *Hartley McGuire*

*   Allow adding additional authorized hosts in development via `ENV['RAILS_DEVELOPMENT_HOSTS']`.

    *Josh Abernathy*, *Debbie Milburn*

*   Add app concern and test keepfiles to generated engine plugins.

    *Gannon McGibbon*

*   Stop generating a license for in-app plugins.

    *Gannon McGibbon*

*   `rails app:update` no longer prompts you to overwrite files that are generally modified in the
    course of developing a Rails app. See [#41083](https://github.com/rails/rails/pull/41083) for
    the full list of changes.

    *Alex Ghiculescu*

*   Change default branch for new Rails projects and plugins to `main`.

    *Prateek Choudhary*

*   The new method `Rails.benchmark` gives you a quick way to measure and log the execution time taken by a block:

        def test_expensive_stuff
          Rails.benchmark("test_expensive_stuff") { ... }
        end

    This functionality was available in some contexts only before.

    *Simon Perepelitsa*

*   Applications generated with `--skip-sprockets` no longer get `app/assets/config/manifest.js` and `app/assets/stylesheets/application.css`.

    *Cindy Gao*

*   Add support for stylesheets and ERB views to `rails stats`.

    *Joel Hawksley*

*   Allow appended root routes to take precedence over internal welcome controller.

    *Gannon McGibbon*


Please check [6-1-stable](https://github.com/rails/rails/blob/6-1-stable/railties/CHANGELOG.md) for previous changes.