diff --git a/api/doc/events/post-req/schema.js b/api/doc/events/post-req/schema.js
index d857f7c..fd95a1e 100644
--- a/api/doc/events/post-req/schema.js
+++ b/api/doc/events/post-req/schema.js
@@ -1,3 +1,5 @@
+import PostSingleReqSchema from '../post-single-req/schema.js'
+
 export default {
   $id: 'https://github.com/data-fair/events/events/post-req',
   title: 'Post event req',
@@ -7,9 +9,8 @@ export default {
   properties: {
     body: {
       type: 'array',
-      items: {
-        $ref: 'https://github.com/data-fair/lib/event'
-      }
+      items: PostSingleReqSchema.properties.body
     }
-  }
+  },
+  $defs: PostSingleReqSchema.$defs
 }
diff --git a/api/doc/events/post-single-req/schema.js b/api/doc/events/post-single-req/schema.js
index f439aa0..4bd812b 100644
--- a/api/doc/events/post-single-req/schema.js
+++ b/api/doc/events/post-single-req/schema.js
@@ -1,3 +1,6 @@
+import jsonSchema from '@data-fair/lib-utils/json-schema.js'
+import EventSchema from '@data-fair/lib-common-types/event/schema.js'
+
 export default {
   $id: 'https://github.com/data-fair/events/events/post-single-req',
   title: 'Post single event req',
@@ -5,6 +8,12 @@ export default {
   type: 'object',
   required: ['body'],
   properties: {
-    body: { $ref: 'https://github.com/data-fair/lib/event' }
-  }
+    body: jsonSchema(EventSchema)
+      .removeReadonlyProperties()
+      .removeFromRequired(['date'])
+      .removeId()
+      .appendTitle(' post')
+      .schema
+  },
+  $defs: EventSchema.$defs
 }
diff --git a/api/doc/notifications/post-req/schema.js b/api/doc/notifications/post-req/schema.js
index d877c22..50a5cdf 100644
--- a/api/doc/notifications/post-req/schema.js
+++ b/api/doc/notifications/post-req/schema.js
@@ -1,5 +1,5 @@
 import jsonSchema from '@data-fair/lib-utils/json-schema.js'
-import NotificationSchema from '#types/notification/schema.js'
+import NotificationSchema from '@data-fair/lib-common-types/notification/schema.js'
 
 export default {
   $id: 'https://github.com/data-fair/events/notifications/post-req',
@@ -11,7 +11,7 @@ export default {
     body:
       jsonSchema(NotificationSchema)
         .removeReadonlyProperties()
-        .removeFromRequired(['visibility'])
+        .removeFromRequired(['date'])
         .removeId()
         .appendTitle(' post')
         .schema
diff --git a/api/package.json b/api/package.json
index 6b2c397..644c5cb 100644
--- a/api/package.json
+++ b/api/package.json
@@ -39,6 +39,7 @@
   },
   "devDependencies": {
     "@types/express": "^5.0.6",
+    "@types/ws": "^8.18.1",
     "@types/fs-extra": "^11.0.4",
     "@types/i18n": "^0.13.12",
     "@types/node-pushnotifications": "^3.1.1",
diff --git a/api/src/events/router.ts b/api/src/events/router.ts
index 4a89a89..0619792 100644
--- a/api/src/events/router.ts
+++ b/api/src/events/router.ts
@@ -1,5 +1,5 @@
 import type { Filter, Sort } from 'mongodb'
-import type { FullEvent } from '#types'
+import type { Event, FullEvent } from '#types'
 
 import { Router } from 'express'
 import mongo from '#mongo'
@@ -55,8 +55,12 @@ router.get('', async (req, res, next) => {
 router.post('', async (req, res, next) => {
   assertReqInternalSecret(req, config.secretKeys.events)
   const { body } = postReq.returnValid(req, { name: 'req' })
+  const events: Event[] = body.map(e => ({
+    date: new Date().toISOString(),
+    ...e,
+  }))
 
-  await postEvents(body)
+  await postEvents(events)
 
   res.status(201).json(body)
 })
diff --git a/api/src/events/service.ts b/api/src/events/service.ts
index 216962a..58eb7cc 100644
--- a/api/src/events/service.ts
+++ b/api/src/events/service.ts
@@ -1,4 +1,4 @@
-import type { Filter } from 'mongodb'
+import { MongoBulkWriteError, type Filter } from 'mongodb'
 import type { Event, FullEvent, SearchableEvent, LocalizedEvent, Subscription, WebhookSubscription, Notification } from '#types'
 import config from '#config'
 import mongo from '#mongo'
@@ -61,10 +61,10 @@ export const postEvents = async (events: Event[]) => {
     // this logic should work much better on a mongodb version that would support multi-language indexing
     // https://www.mongodb.com/docs/manual/core/indexes/index-types/index-text/specify-language-text-index/create-text-index-multiple-languages/
     const event: SearchableEvent = {
-      ...rawEvent,
       _id: nanoid(),
-      _search: [],
-      visibility: rawEvent.visibility ?? 'private'
+      visibility: 'private',
+      ...rawEvent,
+      _search: []
     }
     for (const locale of config.i18n.locales) {
       const localizedEvent = localizeEvent(event, locale)
@@ -98,11 +98,43 @@ export const postEvents = async (events: Event[]) => {
       await createWebhook(localizeEvent(event), webhookSubscription)
     }
   }
-  if (eventsBulkOp.length) await eventsBulkOp.execute()
-  if (notifsBulkOp.length) await notifsBulkOp.execute()
+
+  if (eventsBulkOp.length) {
+    try {
+      await eventsBulkOp.execute({})
+    } catch (err) {
+      // we ignore conflict error, meaning that the same event id can be sent twice without triggering a failure
+      // but without being inserted twice either
+      if (err instanceof MongoBulkWriteError) {
+        const nonConflictError = err.result.getWriteErrors().find(e => e.code !== 11000)
+        if (nonConflictError) throw err
+      } else {
+        throw err
+      }
+    }
+  }
+
+  const insertedNotifications: Notification[] = []
+  if (notifsBulkOp.length) {
+    try {
+      const res = await notifsBulkOp.execute({})
+      for (const id of Object.values(res.insertedIds)) {
+        insertedNotifications.push(notifications.find(n => n._id === id)!)
+      }
+    } catch (err) {
+      // we ignore conflict error, meaning that the same event id can be sent twice without triggering a failure
+      // but without being inserted twice either
+      if (err instanceof MongoBulkWriteError) {
+        const nonConflictError = err.result.getWriteErrors().find(e => e.code !== 11000)
+        if (nonConflictError) throw err
+      } else {
+        throw err
+      }
+    }
+  }
 
   // insertion must be performed before, so that data is available on receiving a WS event
-  for (const notification of notifications) {
+  for (const notification of insertedNotifications) {
     await sendNotification(notification, true)
   }
 }
diff --git a/api/src/mongo.ts b/api/src/mongo.ts
index 8a93b3c..d2522cf 100644
--- a/api/src/mongo.ts
+++ b/api/src/mongo.ts
@@ -61,7 +61,14 @@ export class EventsMongo {
         ]
       },
       notifications: {
-        'main-keys': { 'recipient.id': 1, date: -1 }
+        'main-keys': { 'recipient.id': 1, date: -1 },
+        'unique-event': [
+          { 'recipient.id': 1, eventId: 1 },
+          {
+            unique: true,
+            partialFilterExpression: { eventId: { $exists: true } }
+          }
+        ]
       },
       'webhook-subscriptions': {
         'main-keys': { 'sender.type': 1, 'sender.id': 1, 'owner.type': 1, 'owner.id': 1, 'topic.key': 1 }
diff --git a/api/src/notifications/router.ts b/api/src/notifications/router.ts
index 81158ea..e9fd0ab 100644
--- a/api/src/notifications/router.ts
+++ b/api/src/notifications/router.ts
@@ -1,7 +1,6 @@
 import type { SortDirection } from 'mongodb'
 import type { Pointer } from '../types.ts'
 import type { Notification } from '#types'
-import { nanoid } from 'nanoid'
 import { Router } from 'express'
 import debugModule from 'debug'
 import mongo from '#mongo'
@@ -12,6 +11,7 @@ import * as eventsPostSingleReq from '#doc/events/post-single-req/index.ts'
 import * as notificationsPostReq from '#doc/notifications/post-req/index.ts'
 import { postEvents } from '../events/service.ts'
 import { sendNotification } from './service.ts'
+import { nanoid } from 'nanoid'
 
 const debug = debugModule('events')
 
@@ -66,7 +66,7 @@ router.post('', async (req, res, next) => {
       delete req.body.recipient
     }
     const { body } = eventsPostSingleReq.returnValid(req, { name: 'req' })
-    await postEvents([body])
+    await postEvents([{ date: new Date().toISOString(), ...body }])
     res.status(201).json(body)
   } else {
     debug('pushing a notification with a recipient', req.body)
@@ -81,10 +81,11 @@ router.post('', async (req, res, next) => {
 
     const { body } = notificationsPostReq.returnValid(req, { name: 'req' })
     const notification: Notification = {
-      ...body,
       _id: nanoid(),
-      date: new Date().toISOString()
+      date: new Date().toISOString(),
+      ...body,
     }
+
     await sendNotification(notification)
     res.status(200).json(notification)
   }
diff --git a/api/src/notifications/service.ts b/api/src/notifications/service.ts
index 10b6cc6..7b34294 100644
--- a/api/src/notifications/service.ts
+++ b/api/src/notifications/service.ts
@@ -13,6 +13,7 @@ import config from '#config'
 import * as metrics from './metrics.js'
 import { localizeEvent } from '../events/service.ts'
 import * as pushService from '../push/service.ts'
+import { MongoError } from 'mongodb'
 
 const debug = Debug('notifications')
 
@@ -24,6 +25,7 @@ export const prepareSubscriptionNotification = (event: FullEvent, subscription:
   delete localizedEvent.originator
   delete localizedEvent.urlParams
   const notification: Notification = {
+    eventId: event._id,
     icon: subscription.icon || config.theme.notificationIcon || (subscription.origin + '/events/logo-192x192.png'),
     locale: subscription.locale,
     ...localizedEvent,
@@ -54,7 +56,18 @@ export const prepareSubscriptionNotification = (event: FullEvent, subscription:
 
 export const sendNotification = async (notification: Notification, skipInsert = false) => {
   // global.events.emit('saveNotification', notification)
-  if (!skipInsert) await mongo.notifications.insertOne(notification)
+  if (!skipInsert) {
+    try {
+      await mongo.notifications.insertOne(notification)
+    } catch (err) {
+      if (err instanceof MongoError && err.code === 11000) {
+        // conflict error, simply ignore this duplicate notification
+        return
+      } else {
+        throw err
+      }
+    }
+  }
   debug('Send WS notif', notification.recipient, notification)
   await wsEmitter.emit(`user:${notification.recipient.id}:notifications`, notification)
   if (notification.outputs && notification.outputs.includes('devices')) {
diff --git a/api/types/index.ts b/api/types/index.ts
index eafd0a6..36996c2 100644
--- a/api/types/index.ts
+++ b/api/types/index.ts
@@ -1,13 +1,13 @@
 import type { Event } from '@data-fair/lib-common-types/event/index.js'
+import type { Notification } from '@data-fair/lib-common-types/notification/index.js'
 
+export type { Event, Notification }
 export type { Subscription } from './subscription/index.js'
-export type { Notification } from './notification/index.js'
 export type { Webhook } from './webhook/index.js'
 export type { WebhookSubscription } from './webhook-subscription/index.js'
-export type { Event }
 export type { DevicesPushSubscription } from './push-subscription/index.js'
 export type { DeviceRegistration } from './device-registration/index.js'
 
-export type FullEvent = Event & Required<Pick<Event, 'visibility'>> & { _id: string }
+export type FullEvent = Event & Required<Pick<Event, 'visibility'>>
 export type LocalizedEvent = Omit<FullEvent, 'title' | 'body' | 'htmlBody'> & { title: string, body?: string, htmlBody?: string }
 export type SearchableEvent = FullEvent & { _search: { language: string, text: string }[] }
diff --git a/api/types/notification/index.js b/api/types/notification/index.js
deleted file mode 100644
index f5d615b..0000000
--- a/api/types/notification/index.js
+++ /dev/null
@@ -1 +0,0 @@
-export * from './.type/index.js'
diff --git a/api/types/notification/schema.js b/api/types/notification/schema.js
deleted file mode 100644
index 8da0eae..0000000
--- a/api/types/notification/schema.js
+++ /dev/null
@@ -1,78 +0,0 @@
-export default {
-  $id: 'https://github.com/data-fair/events/notification',
-  'x-exports': ['types', 'validate'],
-  title: 'Notification',
-  type: 'object',
-  additionalProperties: false,
-  required: ['_id', 'title', 'topic', 'recipient', 'date'],
-  properties: {
-    _id: {
-      type: 'string',
-      title: 'Identifiant',
-      readOnly: true
-    },
-    origin: {
-      type: 'string',
-      title: 'Site d\'origine de la souscription',
-      readOnly: true
-    },
-    title: {
-      type: 'string',
-      title: 'Titre'
-    },
-    body: {
-      type: 'string',
-      title: 'Contenu'
-    },
-    htmlBody: {
-      type: 'string',
-      title: 'Contenu HTML'
-    },
-    locale: {
-      type: 'string',
-      title: 'Langue de la notification',
-      enum: ['fr', 'en']
-    },
-    icon: {
-      type: 'string',
-      title: 'URL de l\'icone de la notification'
-    },
-    // sender is the owner of the topic
-    sender: { $ref: 'https://github.com/data-fair/lib/event#/$defs/sender' },
-    topic: { $ref: 'https://github.com/data-fair/lib/event#/$defs/topicRef' },
-    // the recipient of the matched subscription
-    recipient: { $ref: 'https://github.com/data-fair/events/partial#/$defs/recipient' },
-    outputs: {
-      type: 'array',
-      title: 'Sorties',
-      items: {
-        type: 'string',
-        oneOf: [{
-          const: 'devices',
-          title: 'recevoir la notification sur vos appareils configurés'
-        }, {
-          const: 'email',
-          title: 'recevoir la notification par email'
-        }]
-      }
-    },
-    url: {
-      type: 'string',
-      title: 'défini explicitement ou calculé à partir de subscription.urlTemplate et event.urlParams',
-    },
-    date: {
-      readOnly: true,
-      type: 'string',
-      description: 'reception date',
-      format: 'date-time'
-    },
-    new: {
-      readOnly: true,
-      type: 'boolean'
-    },
-    extra: {
-      type: 'object',
-      description: 'propriétés libres qui varient en fonction du type de notification'
-    }
-  }
-}
diff --git a/package-lock.json b/package-lock.json
index ef350e7..1609496 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -63,7 +63,8 @@
         "@types/i18n": "^0.13.12",
         "@types/node-pushnotifications": "^3.1.1",
         "@types/useragent": "^2.3.4",
-        "@types/web-push": "^3.6.4"
+        "@types/web-push": "^3.6.4",
+        "@types/ws": "^8.18.1"
       }
     },
     "api/node_modules/nanoid": {
@@ -1792,16 +1793,6 @@
         "url": "https://github.com/sponsors/kazupon"
       }
     },
-    "node_modules/@isaacs/cliui": {
-      "version": "9.0.0",
-      "resolved": "https://registry.npmjs.org/@isaacs/cliui/-/cliui-9.0.0.tgz",
-      "integrity": "sha512-AokJm4tuBHillT+FpMtxQ60n8ObyXBatq7jD2/JA9dxbDDokKQm8KMht5ibGzLVU9IJDIKK4TPKgMHEYMn3lMg==",
-      "dev": true,
-      "license": "BlueOak-1.0.0",
-      "engines": {
-        "node": ">=18"
-      }
-    },
     "node_modules/@jridgewell/sourcemap-codec": {
       "version": "1.5.5",
       "resolved": "https://registry.npmjs.org/@jridgewell/sourcemap-codec/-/sourcemap-codec-1.5.5.tgz",
@@ -3025,12 +3016,12 @@
       "license": "MIT"
     },
     "node_modules/@types/node": {
-      "version": "25.2.3",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-25.2.3.tgz",
-      "integrity": "sha512-m0jEgYlYz+mDJZ2+F4v8D1AyQb+QzsNqRuI7xg1VQX/KlKS0qT9r1Mo16yo5F/MtifXFgaofIFsdFMox2SxIbQ==",
+      "version": "25.3.0",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-25.3.0.tgz",
+      "integrity": "sha512-4K3bqJpXpqfg2XKGK9bpDTc6xO/xoUP/RBWS7AtRMug6zZFaRekiLzjVtAoZMquxoAbzBvy5nxQ7veS5eYzf8A==",
       "license": "MIT",
       "dependencies": {
-        "undici-types": "~7.16.0"
+        "undici-types": "~7.18.0"
       }
     },
     "node_modules/@types/node-pushnotifications": {
@@ -3175,6 +3166,16 @@
         "@types/webidl-conversions": "*"
       }
     },
+    "node_modules/@types/ws": {
+      "version": "8.18.1",
+      "resolved": "https://registry.npmjs.org/@types/ws/-/ws-8.18.1.tgz",
+      "integrity": "sha512-ThVF6DCVhA8kUGy+aazFQ4kXQ7E1Ty7A3ypFOe0IcJV8O/M511G99AW24irKrW56Wt44yG9+ij8FaqoBGkuBXg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/node": "*"
+      }
+    },
     "node_modules/@typescript-eslint/eslint-plugin": {
       "version": "8.56.0",
       "resolved": "https://registry.npmjs.org/@typescript-eslint/eslint-plugin/-/eslint-plugin-8.56.0.tgz",
@@ -4075,9 +4076,9 @@
       }
     },
     "node_modules/acorn": {
-      "version": "8.15.0",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.15.0.tgz",
-      "integrity": "sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==",
+      "version": "8.16.0",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.16.0.tgz",
+      "integrity": "sha512-UVJyE9MttOsBQIDKw1skb9nAwQuR5wuGD3+82K6JgJlm/Y+KI92oNsMNGZCYdDsVtRHSak0pcV5Dno5+4jh9sw==",
       "license": "MIT",
       "bin": {
         "acorn": "bin/acorn"
@@ -4582,9 +4583,9 @@
       "optional": true
     },
     "node_modules/bn.js": {
-      "version": "4.12.2",
-      "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-4.12.2.tgz",
-      "integrity": "sha512-n4DSx829VRTRByMRGdjQ9iqsN0Bh4OolPsFnaZBLcbi8iXcB+kJ9s7EnRt4wILZNV3kPLHkRVfOc/HvhC3ovDw==",
+      "version": "4.12.3",
+      "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-4.12.3.tgz",
+      "integrity": "sha512-fGTi3gxV/23FTYdAoUtLYp6qySe2KE3teyZitipKNRuVYcBkoP/bB3guXN/XVKUe9mxCHXnc9C4ocyz8OmgN0g==",
       "license": "MIT"
     },
     "node_modules/body-parser": {
@@ -6097,14 +6098,11 @@
       }
     },
     "node_modules/eslint-plugin-import-x/node_modules/balanced-match": {
-      "version": "4.0.2",
-      "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-4.0.2.tgz",
-      "integrity": "sha512-x0K50QvKQ97fdEz2kPehIerj+YTeptKF9hyYkKf6egnwmMWAkADiO0QCzSp0R5xN8FTZgYaBfSaue46Ej62nMg==",
+      "version": "4.0.3",
+      "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-4.0.3.tgz",
+      "integrity": "sha512-1pHv8LX9CpKut1Zp4EXey7Z8OfH11ONNH6Dhi2WDUt31VVZFXZzKwXcysBgqSumFCmR+0dqjMK5v5JiFHzi0+g==",
       "dev": true,
       "license": "MIT",
-      "dependencies": {
-        "jackspeak": "^4.2.3"
-      },
       "engines": {
         "node": "20 || >=22"
       }
@@ -6123,16 +6121,16 @@
       }
     },
     "node_modules/eslint-plugin-import-x/node_modules/minimatch": {
-      "version": "10.2.1",
-      "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-10.2.1.tgz",
-      "integrity": "sha512-MClCe8IL5nRRmawL6ib/eT4oLyeKMGCghibcDWK+J0hh0Q8kqSdia6BvbRMVk6mPa6WqUa5uR2oxt6C5jd533A==",
+      "version": "10.2.2",
+      "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-10.2.2.tgz",
+      "integrity": "sha512-+G4CpNBxa5MprY+04MbgOw1v7So6n5JY166pFi9KfYwT78fxScCeSNQSNzp6dpPSW2rONOps6Ocam1wFhCgoVw==",
       "dev": true,
       "license": "BlueOak-1.0.0",
       "dependencies": {
         "brace-expansion": "^5.0.2"
       },
       "engines": {
-        "node": "20 || >=22"
+        "node": "18 || 20 || >=22"
       },
       "funding": {
         "url": "https://github.com/sponsors/isaacs"
@@ -8426,22 +8424,6 @@
         "node": ">= 0.4"
       }
     },
-    "node_modules/jackspeak": {
-      "version": "4.2.3",
-      "resolved": "https://registry.npmjs.org/jackspeak/-/jackspeak-4.2.3.tgz",
-      "integrity": "sha512-ykkVRwrYvFm1nb2AJfKKYPr0emF6IiXDYUaFx4Zn9ZuIH7MrzEZ3sD5RlqGXNRpHtvUHJyOnCEFxOlNDtGo7wg==",
-      "dev": true,
-      "license": "BlueOak-1.0.0",
-      "dependencies": {
-        "@isaacs/cliui": "^9.0.0"
-      },
-      "engines": {
-        "node": "20 || >=22"
-      },
-      "funding": {
-        "url": "https://github.com/sponsors/isaacs"
-      }
-    },
     "node_modules/jiti": {
       "version": "2.6.1",
       "resolved": "https://registry.npmjs.org/jiti/-/jiti-2.6.1.tgz",
@@ -10071,9 +10053,9 @@
       }
     },
     "node_modules/node-pushnotifications/node_modules/fast-xml-parser": {
-      "version": "5.3.6",
-      "resolved": "https://registry.npmjs.org/fast-xml-parser/-/fast-xml-parser-5.3.6.tgz",
-      "integrity": "sha512-QNI3sAvSvaOiaMl8FYU4trnEzCwiRr8XMWgAHzlrWpTSj+QaCSvOf1h82OEP1s4hiAXhnbXSyFWCf4ldZzZRVA==",
+      "version": "5.3.7",
+      "resolved": "https://registry.npmjs.org/fast-xml-parser/-/fast-xml-parser-5.3.7.tgz",
+      "integrity": "sha512-JzVLro9NQv92pOM/jTCR6mHlJh2FGwtomH8ZQjhFj/R29P2Fnj38OgPJVtcvYw6SuKClhgYuwUZf5b3rd8u2mA==",
       "funding": [
         {
           "type": "github",
@@ -10792,6 +10774,7 @@
       "version": "7.1.3",
       "resolved": "https://registry.npmjs.org/prebuild-install/-/prebuild-install-7.1.3.tgz",
       "integrity": "sha512-8Mf2cbV7x1cXPUILADGI3wuhfqWvtiLA1iclTDbFRZkgRQS0NqsPZphna9V+HyTEadheuPmjaJMsbzKQFOzLug==",
+      "deprecated": "No longer maintained. Please contact the author of the relevant native addon; alternatives are available.",
       "license": "MIT",
       "dependencies": {
         "detect-libc": "^2.0.0",
@@ -13135,17 +13118,17 @@
       }
     },
     "node_modules/underscore": {
-      "version": "1.13.7",
-      "resolved": "https://registry.npmjs.org/underscore/-/underscore-1.13.7.tgz",
-      "integrity": "sha512-GMXzWtsc57XAtguZgaQViUOzs0KTkk8ojr3/xAxXLITqf/3EMwxC0inyETfDFjH/Krbhuep0HNbbjI9i/q3F3g==",
+      "version": "1.13.8",
+      "resolved": "https://registry.npmjs.org/underscore/-/underscore-1.13.8.tgz",
+      "integrity": "sha512-DXtD3ZtEQzc7M8m4cXotyHR+FAS18C64asBYY5vqZexfYryNNnDc02W4hKg3rdQuqOYas1jkseX0+nZXjTXnvQ==",
       "dev": true,
       "license": "MIT",
       "optional": true
     },
     "node_modules/undici-types": {
-      "version": "7.16.0",
-      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.16.0.tgz",
-      "integrity": "sha512-Zz+aZWSj8LE6zoxD+xrjh4VfkIG8Ya6LvYkZqtUQGJPZjYl53ypCaUwWqo7eI0x66KBGeRo+mlBEkMSeSZ38Nw==",
+      "version": "7.18.2",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.18.2.tgz",
+      "integrity": "sha512-AsuCzffGHJybSaRrmr5eHr81mwJU3kjw6M+uprWvCXiNeN9SOGwQ3Jn8jb8m3Z6izVgknn1R0FTCEAP2QrLY/w==",
       "license": "MIT"
     },
     "node_modules/unicorn-magic": {
@@ -13968,9 +13951,9 @@
       }
     },
     "node_modules/vuetify": {
-      "version": "3.11.8",
-      "resolved": "https://registry.npmjs.org/vuetify/-/vuetify-3.11.8.tgz",
-      "integrity": "sha512-4iKnntOnLFFklygZjzlVfcHrtLO8+iK4HOhiia6HP2U8v82x+ngaSCgm+epvPrGyCMfCpfuEttqD2qElrr1axw==",
+      "version": "3.12.0",
+      "resolved": "https://registry.npmjs.org/vuetify/-/vuetify-3.12.0.tgz",
+      "integrity": "sha512-N1y3sxLAyrblBHJ6vFTQoTM9icwZd/jNUsmYVQTvHNQHN22XDqb0w2+ujaSoEn/JCHbtGb70tKRlB9SJ6HhVgg==",
       "license": "MIT",
       "funding": {
         "type": "github",
diff --git a/test-it/01-events.ts b/test-it/01-events.ts
index 6a75a34..350fee7 100644
--- a/test-it/01-events.ts
+++ b/test-it/01-events.ts
@@ -78,4 +78,24 @@ describe('events', () => {
     assert.equal(res.data.results.length, 1)
     assert.equal(res.data.results[0].title, 'an english notification')
   })
+
+  it('should send an event with same id twice', async () => {
+    let res = await axPush.post('/api/events', [{
+      _id: 'test',
+      date: new Date().toISOString(),
+      topic: { key: 'topic1' },
+      title: 'notif 1',
+      sender: { type: 'user', id: 'user1', name: 'User 1' }
+    }])
+    res = await axPush.post('/api/events', [{
+      _id: 'test',
+      date: new Date().toISOString(),
+      topic: { key: 'topic1' },
+      title: 'notif 2',
+      sender: { type: 'user', id: 'user1', name: 'User 1' }
+    }])
+    res = await user1.get('/api/events')
+    assert.equal(res.data.results.length, 1)
+    assert.equal(res.data.results[0].title, 'notif 1')
+  })
 })
diff --git a/test-it/02-subscriptions.ts b/test-it/02-subscriptions.ts
index 09eca35..da28cad 100644
--- a/test-it/02-subscriptions.ts
+++ b/test-it/02-subscriptions.ts
@@ -1,5 +1,6 @@
 import { strict as assert } from 'node:assert'
 import { it, describe, before, beforeEach, after } from 'node:test'
+import WebSocket from 'ws'
 import { axios, axiosAuth, clean, startApiServer, stopApiServer } from './utils/index.ts'
 
 const axPush = axios({ params: { key: 'SECRET_EVENTS' }, baseURL: 'http://localhost:8082/events' })
@@ -221,4 +222,126 @@ describe('subscriptions', () => {
     res = await user2.get('/api/notifications')
     assert.equal(res.data.count, 1)
   })
+
+  it('should send notificationss of de-duplicated events', async () => {
+    // user1 is subscribed in 2 different manners
+    let res = await user1.post('/api/subscriptions', {
+      topic: { key: 'topic1' },
+      sender: { type: 'organization', id: 'orga1' }
+    })
+    res = await user1.post('/api/subscriptions', {
+      topic: { key: 'topic2' },
+      sender: { type: 'organization', id: 'orga1' }
+    })
+
+    // admin is subscribed in the second manner only
+    res = await admin1.post('/api/subscriptions', {
+      topic: { key: 'topic2' },
+      sender: { type: 'organization', id: 'orga1' }
+    })
+
+    res = await axPush.post('/api/events', [{
+      _id: 'test',
+      date: new Date().toISOString(),
+      topic: { key: 'topic1' },
+      title: 'notif 1',
+      sender: { type: 'organization', id: 'orga1', name: 'Orga 1' }
+    }])
+    res = await axPush.post('/api/events', [{
+      _id: 'test',
+      date: new Date().toISOString(),
+      topic: { key: 'topic2' },
+      title: 'notif 2',
+      sender: { type: 'organization', id: 'orga1', name: 'Orga 1' }
+    }])
+    res = await admin1.get('/api/notifications')
+    assert.equal(res.data.count, 1)
+    // no duplicate created
+    res = await user1.get('/api/notifications')
+    assert.equal(res.data.count, 1)
+
+    // another notification sent straight to the user
+    res = await axPush.post('/api/notifications', {
+      // eventId: 'test',
+      date: new Date().toISOString(),
+      topic: { key: 'topic2' },
+      title: 'notif 2',
+      recipient: { id: 'user1' }
+    })
+    res = await user1.get('/api/notifications')
+    assert.equal(res.data.count, 2)
+
+    // a duplicate not saved
+    res = await axPush.post('/api/notifications', {
+      eventId: 'test',
+      date: new Date().toISOString(),
+      topic: { key: 'topic2' },
+      title: 'notif 2',
+      recipient: { id: 'user1' }
+    })
+    res = await user1.get('/api/notifications')
+    assert.equal(res.data.count, 2)
+  })
+
+  it('should deliver direct notifications via WS', async () => {
+    const cookies = user1.cookieJar.getCookiesSync('http://localhost:5600')
+    const ws = new WebSocket('ws://localhost:8082', { headers: { Cookie: cookies.map(String).join('; ') } })
+    const messages: any[] = []
+
+    await new Promise<void>((resolve, reject) => {
+      ws.on('message', (raw: Buffer) => {
+        const msg = JSON.parse(raw.toString())
+        if (msg.type === 'subscribe-confirm') resolve()
+        if (msg.type === 'message') messages.push(msg)
+      })
+      ws.on('open', () => ws.send(JSON.stringify({ type: 'subscribe', channel: 'user:user1:notifications' })))
+      ws.on('error', reject)
+    })
+
+    await axPush.post('/api/notifications', {
+      topic: { key: 'topic1' },
+      sender: { type: 'user', id: 'user1', name: 'User 1' },
+      title: 'notif direct 1',
+      recipient: { id: 'user1' }
+    })
+    await new Promise(resolve => setTimeout(resolve, 200))
+    assert.equal(messages.length, 1)
+    assert.equal(messages[0].data.title, 'notif direct 1')
+
+    await axPush.post('/api/notifications', {
+      topic: { key: 'topic1' },
+      sender: { type: 'user', id: 'user1', name: 'User 1' },
+      title: 'notif direct 2',
+      recipient: { id: 'user1' }
+    })
+    await new Promise(resolve => setTimeout(resolve, 200))
+    assert.equal(messages.length, 2)
+    assert.equal(messages[1].data.title, 'notif direct 2')
+
+    // a duplicate should not produce a WS message
+    await axPush.post('/api/notifications', {
+      eventId: 'ws-dedup',
+      topic: { key: 'topic1' },
+      sender: { type: 'user', id: 'user1', name: 'User 1' },
+      title: 'notif dedup',
+      recipient: { id: 'user1' }
+    })
+    await new Promise(resolve => setTimeout(resolve, 200))
+    assert.equal(messages.length, 3)
+
+    await axPush.post('/api/notifications', {
+      eventId: 'ws-dedup',
+      topic: { key: 'topic1' },
+      sender: { type: 'user', id: 'user1', name: 'User 1' },
+      title: 'notif dedup',
+      recipient: { id: 'user1' }
+    })
+    await new Promise(resolve => setTimeout(resolve, 200))
+    assert.equal(messages.length, 3)
+
+    const res = await user1.get('/api/notifications')
+    assert.equal(res.data.count, 3)
+
+    ws.close()
+  })
 })