diff --git a/config/environments/development.rb b/config/environments/development.rb
index 92bae2cd04..8a858f65e4 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -3,9 +3,7 @@
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
-  # In the development environment your application's code is reloaded any time
-  # it changes. This slows down response time but is perfect for development
-  # since you don't have to restart the web server when you make code changes.
+  # Make code changes take effect immediately without server restart.
   config.enable_reloading = true
 
   # Do not eager load code on boot.
@@ -17,8 +15,8 @@
   # Enable server timing.
   config.server_timing = true
 
-  # Enable/disable caching. By default caching is disabled.
-  # Run rails dev:cache to toggle caching.
+  # Enable/disable Action Controller caching. By default Action Controller caching is disabled.
+  # Run rails dev:cache to toggle Action Controller caching.
   if Rails.root.join("tmp/caching-dev.txt").exist?
     config.action_controller.perform_caching = true
     config.action_controller.enable_fragment_cache_logging = true
@@ -69,9 +67,6 @@
   config.hosts << "frontend.dev.gov.uk"
   config.hosts << "example.org"
 
-  # Uncomment if you wish to allow Action Cable access from any origin.
-  # config.action_cable.disable_request_forgery_protection = true
-
   # Raise error when a before_action's only/except options reference missing actions.
   config.action_controller.raise_on_missing_callback_actions = true
 
diff --git a/config/environments/production.rb b/config/environments/production.rb
index 5104b79134..bc48b4aced 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -7,21 +7,21 @@
   # Code is not reloaded between requests.
   config.enable_reloading = false
 
-  # Eager load code on boot. This eager loads most of Rails and
-  # your application in memory, allowing both threaded web servers
-  # and those relying on copy on write to perform better.
-  # Rake tasks automatically ignore this option for performance.
+  # Eager load code on boot for better performance and memory savings (ignored by Rake tasks).
   config.eager_load = true
 
-  # Full error reports are disabled and caching is turned on.
+  # Full error reports are disabled.
   config.consider_all_requests_local = false
+
+  # Turn on fragment caching in view templates.
   config.action_controller.perform_caching = true
 
   # Ensures that a master key has been made available in ENV["RAILS_MASTER_KEY"], config/master.key, or an environment
   # key such as config/credentials/production.key. This key is used to decrypt credentials (and other encrypted files).
   # config.require_master_key = true
 
-  # Disable serving static files from `public/`, relying on NGINX/Apache to do so instead.
+  # Disable serving static files from the `/public` folder by default since
+  # Apache or NGINX already handles this.
   config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
 
   # Compress CSS using a preprocessor.
@@ -30,15 +30,14 @@
   # Do not fall back to assets pipeline if a precompiled asset is missed.
   config.assets.compile = false
 
+  config.assets.compress = true
+  config.assets.digest = true
+  config.assets.js_compressor = :terser
+
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.asset_host = "http://assets.example.com"
 
-  # Specifies the header that your server uses for sending files.
-  # config.action_dispatch.x_sendfile_header = "X-Sendfile" # for Apache
-  # config.action_dispatch.x_sendfile_header = "X-Accel-Redirect" # for NGINX
-
   # Assume all access to the app is happening through a SSL-terminating reverse proxy.
-  # Can be used together with config.force_ssl for Strict-Transport-Security and secure cookies.
   # config.assume_ssl = true
 
   # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
@@ -47,18 +46,33 @@
   # Skip http-to-https redirect for the default health check endpoint.
   # config.ssl_options = { redirect: { exclude: ->(request) { request.path == "/up" } } }
 
+  if ENV["RAILS_LOG_TO_STDOUT"].present?
+    logger           = ActiveSupport::Logger.new($stdout)
+    logger.formatter = config.log_formatter
+    config.logger    = ActiveSupport::TaggedLogging.new(logger)
+  end
+
   # Prepend all log lines with the following tags.
   config.log_tags = [:request_id]
 
+  # Use default logging formatter so that PID and timestamp are not suppressed.
+  config.log_formatter = ::Logger::Formatter.new
+
   # "info" includes generic and useful information about system operation, but avoids logging too much
   # information to avoid inadvertent exposure of personally identifiable information (PII). If you
   # want to log everything, set the level to "debug".
   config.log_level = ENV.fetch("RAILS_LOG_LEVEL", "info")
 
-  # Use a different cache store in production (if configured)
+  # Prevent health checks from clogging up the logs.
+  config.silence_healthcheck_path = "/up"
+
+  # Don't log any deprecations.
+  config.active_support.report_deprecations = false
+
+  # Replace the default in-process memory cache store with a durable alternative (if configured).
   config.cache_store = :mem_cache_store, nil, { namespace: :frontend, compress: true } if ENV["MEMCACHE_SERVERS"]
 
-  # Use a real queuing backend for Active Job (and separate queues per environment).
+  # Replace the default in-process and non-durable queuing backend for Active Job.
   # config.active_job.queue_adapter = :resque
   # config.active_job.queue_name_prefix = "frontend_production"
 
@@ -66,34 +80,15 @@
   # the I18n.default_locale when a translation cannot be found).
   config.i18n.fallbacks = true
 
-  # Don't log any deprecations.
-  config.active_support.report_deprecations = false
-
   # Enable DNS rebinding protection and other `Host` header attacks.
   # config.hosts = [
   #   "example.com",     # Allow requests from example.com
   #   /.*\.example\.com/ # Allow requests from subdomains like `www.example.com`
   # ]
+  #
   # Skip DNS rebinding protection for the default health check endpoint.
   # config.host_authorization = { exclude: ->(request) { request.path == "/up" } }
 
-  # Use default logging formatter so that PID and timestamp are not suppressed.
-  config.log_formatter = ::Logger::Formatter.new
-
-  # Use a different logger for distributed setups.
-  # require "syslog/logger"
-  # config.logger = ActiveSupport::TaggedLogging.new(Syslog::Logger.new "app-name")
-
-  if ENV["RAILS_LOG_TO_STDOUT"].present?
-    logger           = ActiveSupport::Logger.new($stdout)
-    logger.formatter = config.log_formatter
-    config.logger    = ActiveSupport::TaggedLogging.new(logger)
-  end
-
-  config.assets.compress = true
-  config.assets.digest = true
-  config.assets.js_compressor = :terser
-
   # Specifies the header that your server uses for sending files
   config.action_dispatch.x_sendfile_header = ENV["HEROKU_APP_NAME"] ? nil : "X-Sendfile"
 end
diff --git a/config/environments/test.rb b/config/environments/test.rb
index b6ffe146c2..dae63a0005 100644
--- a/config/environments/test.rb
+++ b/config/environments/test.rb
@@ -18,14 +18,13 @@
   config.eager_load = ENV["CI"].present?
 
   # Configure public file server for tests with Cache-Control for performance.
-  config.public_file_server.enabled = true
   config.public_file_server.headers = {
     "Cache-Control" => "public, max-age=#{1.hour.to_i}",
   }
+  config.public_file_server.enabled = true
 
-  # Show full error reports and disable caching.
+  # Show full error reports.
   config.consider_all_requests_local = true
-  config.action_controller.perform_caching = false
   config.cache_store = :null_store
 
   # Raise exceptions instead of rendering exception templates.
@@ -34,6 +33,8 @@
   # Disable request forgery protection in test environment.
   config.action_controller.allow_forgery_protection = false
 
+  config.action_controller.perform_caching = false
+
   # Print deprecation notices to the stderr.
   config.active_support.deprecation = :stderr
 
diff --git a/config/initializers/assets.rb b/config/initializers/assets.rb
index 1e972738bb..ded865c00f 100644
--- a/config/initializers/assets.rb
+++ b/config/initializers/assets.rb
@@ -6,8 +6,3 @@
 # Add additional assets to the asset load path.
 # Add Yarn node_modules folder to the asset load path.
 Rails.application.config.assets.paths << Rails.root.join("node_modules")
-
-# Precompile additional assets.
-# application.js, application.css, and all non-JS/CSS in the app/assets
-# folder are already added.
-# Rails.application.config.assets.precompile += %w[ admin.js admin.css ]
diff --git a/config/initializers/filter_parameter_logging.rb b/config/initializers/filter_parameter_logging.rb
index 63d4f8be0e..91cf7d6c08 100644
--- a/config/initializers/filter_parameter_logging.rb
+++ b/config/initializers/filter_parameter_logging.rb
@@ -1,8 +1,8 @@
 # Be sure to restart your server when you modify this file.
 
-# Configure parameters to be filtered from the log file. Use this to limit dissemination of
-# sensitive information. See the ActiveSupport::ParameterFilter documentation for supported
-# notations and behaviors.
+# Configure parameters to be partially matched (e.g. passw matches password) and filtered from the log file.
+# Use this to limit dissemination of sensitive information.
+# See the ActiveSupport::ParameterFilter documentation for supported notations and behaviors.
 Rails.application.config.filter_parameters += %i[
-  password passw secret token _key crypt salt certificate otp ssn
+  password passw email secret token _key crypt salt certificate otp ssn cvv cvc
 ]
diff --git a/config/initializers/new_framework_defaults_8_0.rb b/config/initializers/new_framework_defaults_8_0.rb
new file mode 100644
index 0000000000..92efa95152
--- /dev/null
+++ b/config/initializers/new_framework_defaults_8_0.rb
@@ -0,0 +1,30 @@
+# Be sure to restart your server when you modify this file.
+#
+# This file eases your Rails 8.0 framework defaults upgrade.
+#
+# Uncomment each configuration one by one to switch to the new default.
+# Once your application is ready to run with all new defaults, you can remove
+# this file and set the `config.load_defaults` to `8.0`.
+#
+# Read the Guide for Upgrading Ruby on Rails for more info on each option.
+# https://guides.rubyonrails.org/upgrading_ruby_on_rails.html
+
+###
+# Specifies whether `to_time` methods preserve the UTC offset of their receivers or preserves the timezone.
+# If set to `:zone`, `to_time` methods will use the timezone of their receivers.
+# If set to `:offset`, `to_time` methods will use the UTC offset.
+# If `false`, `to_time` methods will convert to the local system UTC offset instead.
+#++
+# Rails.application.config.active_support.to_time_preserves_timezone = :zone
+
+###
+# When both `If-Modified-Since` and `If-None-Match` are provided by the client
+# only consider `If-None-Match` as specified by RFC 7232 Section 6.
+# If set to `false` both conditions need to be satisfied.
+#++
+# Rails.application.config.action_dispatch.strict_freshness = true
+
+###
+# Set `Regexp.timeout` to `1`s by default to improve security over Regexp Denial-of-Service attacks.
+#++
+# Regexp.timeout = 1