Add flash data

docs/.vitepress/config.mts

@@ -130,6 +130,7 @@ export default defineConfig({
           text: 'Data & Props',
           items: [
             { text: 'Shared data', link: '/guide/shared-data' },
+            { text: 'Flash data', link: '/guide/flash-data' },
             { text: 'Partial reloads', link: '/guide/partial-reloads' },
             { text: 'Deferred props', link: '/guide/deferred-props' },
             { text: 'Polling', link: '/guide/polling' },

docs/guide/configuration.md

@@ -143,6 +143,29 @@ When set to `true`, an empty `errors: {}` object will always be included in Iner
 
 The default value will be changed to `true` in the next major version.
 
+### `flash_keys`
+
+**Default**: `%i[notice alert]`
+
+@available_since rails=master core=2.3.3
+
+Specifies which Rails flash keys are exposed to the frontend. By default, only known-safe keys (`notice`, `alert`) are included.
+
+```ruby
+InertiaRails.configure do |config|
+  # Default: safe keys only
+  config.flash_keys = %i[notice alert]
+
+  # Add your custom keys
+  config.flash_keys = %i[notice alert toast message]
+
+  # Disable Rails flash integration (use only flash.inertia)
+  config.flash_keys = nil
+end
+```
+
+See the [flash data documentation](/guide/flash-data) for more details on using flash with Inertia.
+
 ### `parent_controller`
 
 **Default**: `'::ApplicationController'`

docs/guide/events.md

@@ -495,6 +495,53 @@ router.on('success', (event) => {
 
 The `success` event is not cancelable.
 
+## Flash
+
+@available_since rails=master core=2.3.3
+
+The `flash` event fires when [flash data](/guide/flash-data) is received from the server. This is useful for displaying toast notifications or handling temporary data in a central location.
+
+:::tabs key:frameworks
+== Vue
+
+```js
+import { router } from '@inertiajs/vue3'
+
+router.on('flash', (event) => {
+  if (event.detail.flash.toast) {
+    showToast(event.detail.flash.toast)
+  }
+})
+```
+
+== React
+
+```js
+import { router } from '@inertiajs/react'
+
+router.on('flash', (event) => {
+  if (event.detail.flash.toast) {
+    showToast(event.detail.flash.toast)
+  }
+})
+```
+
+== Svelte 4|Svelte 5
+
+```js
+import { router } from '@inertiajs/svelte'
+
+router.on('flash', (event) => {
+  if (event.detail.flash.toast) {
+    showToast(event.detail.flash.toast)
+  }
+})
+```
+
+:::
+
+The `flash` event is not cancelable. [Partial reloads](/guide/partial-reloads) will only trigger the event if the flash data has changed.
+
 ## Error
 
 The `error` event fires when validation errors are present on "successful" page visits.