> ## Documentation Index
> Fetch the complete documentation index at: https://forest-docs-cli-reference-headless-commands.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# Upgrade to v3
> Help developers to move from v2 to v3. Please read carefully and integrate the following breaking changes to ensure a smooth update.
Please be aware that while Forest make every effort to ensure that our platform updates are broadly compatible and offer detailed instructions for upgrading, Forest cannot guarantee that custom code developed by the developers will always be compatible with new versions of our software. This includes any custom modifications or extensions to core functionalities, such as method overrides or custom integrations. It is the responsibility of the developers to review and test their custom code to ensure compatibility with each new version. Our team provides comprehensive upgrade guides to assist in this process, but these cannot encompass the unique customizations that may be present in each customer's environment. Therefore, Forest strongly recommend establishing a thorough testing protocol for your specific customizations to safeguard against potential issues during the upgrade process.
## Breaking changes
### Cors configuration
Set CORS `credentials: true` if you're using custom CORS configuration. See [how to configure CORS headers](/legacy/ruby-agent/how-tos/setup/configuring-cors-headers).
### Rails
We use the [Rack CORS](https://github.com/cyu/rack-cors) Gem for this purpose.
```ruby theme={null}
# Gemfile
source 'https://rubygems.org'
# ...
gem 'forest_liana'
gem 'rack-cors'
```
```ruby theme={null}
module LiveDemoRails
class Application < Rails::Application
# ...
# For Rails 5, use the class Rack::Cors. For Rails 4, you MUST use the string 'Rack::Cors'.
config.middleware.insert_before 0, Rack::Cors do
allow do
origins 'app.forestadmin.com'
resource '*',
headers: :any,
methods: :any,
expose: ['Content-Disposition'],
credentials: true
end
end
end
end
```
### Global smart action
Smart actions defined as follows `global: true` will no longer be considered as global.
Please now use `type: 'global'`.
### Rails
**Before**
```ruby theme={null}
class Forest::Product
include ForestLiana::Collection
collection :Product
action 'Import data',
global: true
# ...
end
```
**After**
```ruby theme={null}
class Forest::Product
include ForestLiana::Collection
collection :Product
action 'Import data',
type: 'global'
# ...
end
```
### Schema versioning
On server start - *only in development environments* - the agent will generate a `.forestadmin-schema.json` file reflecting your **Forest schema**.
If you change your models or database, Forest will automatically load a new schema to keep the layout up to date.
**Do not edit this file**. It will be automatically generated on server start **only in development environments**.
This file **must be deployed** for any remote environment (staging, production, etc.), as it will be used to generate your Forest UI.
**Version this file.** It will give you more visibility on the changes detected by Forest.
In the following example, we have added two fields on the `invoices` table:
* `emailSent`
* `quadernoId`
Versioning the`.forestadmin-schema.json` file allows you to easily visualize the changes.
## Changelogs
This release note covers only the major changes. To learn more, please refer to the changelogs in our different repositories:
* [Rails changelog](https://github.com/ForestAdmin/forest-rails/blob/master/CHANGELOG.md#release-300---2019-04-22)