diff --git a/api/src/limits/service.ts b/api/src/limits/service.ts
index 636fd6e0..87233f7d 100644
--- a/api/src/limits/service.ts
+++ b/api/src/limits/service.ts
@@ -17,9 +17,10 @@ export const getOrgLimits = async (org: Organization) => {
   return limit
 }
 
-// NHIs are not members: findMembers excludes them by default, this query has to do the same
+// NHIs count as members here: they hold an org membership like humans do and consume the same quota,
+// even though findMembers hides them by default
 const getNbMembers = async (orgId: string) => {
-  return mongo.users.countDocuments({ 'organizations.id': orgId, plannedDeletion: { $exists: false }, nhi: { $exists: false } })
+  return mongo.users.countDocuments({ 'organizations.id': orgId, plannedDeletion: { $exists: false } })
 }
 
 export const setNbMembersLimit = async (orgId: string) => {
diff --git a/api/src/nhis/router.ts b/api/src/nhis/router.ts
index 83920cb3..e67f399d 100644
--- a/api/src/nhis/router.ts
+++ b/api/src/nhis/router.ts
@@ -4,7 +4,7 @@ import eventsLog from '@data-fair/lib-express/events-log.js'
 import config from '#config'
 import storages from '#storages'
 import { reqI18n } from '#i18n'
-import { postUserIdentityWebhook, deleteIdentityWebhook } from '#services'
+import { postUserIdentityWebhook, deleteIdentityWebhook, getOrgLimits, setNbMembersLimit } from '#services'
 import { isOrgAdmin } from '../organizations/service.ts'
 import { checkProvider } from './keys.ts'
 import { checkAllowedIps } from './ips.ts'
@@ -43,9 +43,15 @@ router.post('', async (req: Request<OrgParams>, res) => {
   if (!roles.includes(body.role)) throw httpError(400, 'unknown role')
   await checkProvider(body.provider)
   if (body.allowedIps) checkAllowedIps(body.allowedIps)
+  logContext.account = { type: 'organization', id: org.id, name: org.name }
+  const limits = await getOrgLimits(org)
+  if (limits.store_nb_members.limit > 0 && limits.store_nb_members.consumption >= limits.store_nb_members.limit) {
+    eventsLog.info('sd.nhi.limit', `limit error for NHI creation in org ${org.id}`, logContext)
+    throw httpError(429, reqI18n(req).messages.errors.maxNbMembers)
+  }
   const sessionUser = reqSessionAuthenticated(req).user
   const user = await createNhi(org, body, { id: sessionUser.id, name: sessionUser.name })
-  logContext.account = { type: 'organization', id: org.id, name: org.name }
+  await setNbMembersLimit(org.id)
   eventsLog.info('sd.nhi.create', `an NHI was created ${user.id} in org ${org.id}`, logContext)
   postUserIdentityWebhook(user)
   res.status(201).send(user)
@@ -111,6 +117,7 @@ router.delete('/:nhiId', async (req: Request<NhiParams>, res) => {
   const user = await getNhi(req.params.organizationId, req.params.nhiId)
   logContext.account = { type: 'organization', id: req.params.organizationId, name: user.organizations[0]?.name }
   await storages.globalStorage.deleteUser(user.id)
+  await setNbMembersLimit(req.params.organizationId)
   eventsLog.info('sd.nhi.delete', `an NHI was deleted ${user.id}`, logContext)
   deleteIdentityWebhook('user', user.id)
   res.status(204).send()
diff --git a/docs/architecture/non-human-identities.md b/docs/architecture/non-human-identities.md
index 6db82128..988616fa 100644
--- a/docs/architecture/non-human-identities.md
+++ b/docs/architecture/non-human-identities.md
@@ -369,16 +369,19 @@ $exists: false }`). An NHI id passed as `:userId` 404s before the
 `assertNotNhiSession` guard is even relevant — the guard covers the case of
 an NHI *session* acting on someone else, the 404 gate covers an NHI as
 *target*. `GET /api/organizations/:id/members` uses the same default, so
-existing consumers (quota counts, invitation UIs, other services) see no
+existing consumers (invitation UIs, other services) see no
 behavior change unless they opt in with `?types=nhi` or
 `?types=user,nhi`.
 
-**`findMembers` is not the only place that has to exclude NHIs.**
+**NHIs do count in the members quota.** Unlike `findMembers`,
 `getNbMembers` (`api/src/limits/service.ts`), which feeds the
-`store_nb_members` quota, counts the `users` collection directly instead of
-going through `findMembers`, so it repeats the `nhi: { $exists: false }`
-filter itself. Any new consumer that counts memberships with its own query
-has to do the same.
+`store_nb_members` quota, counts every membership in the `users` collection,
+NHIs included: a service account holds an org membership and acts with its
+role, so it consumes a member slot like a human does. NHI creation
+(`POST /api/organizations/:organizationId/nhis`) is refused with a 429 when the
+org is full, and both creation and deletion recompute the counter. The
+consequence is that `store_nb_members.consumption` can exceed the `count` of
+the default (human only) member listing.
 
 **Cleanup jobs exclude NHIs.** `storage.findInactiveUsers` /
 `findUsersToDelete` (`api/src/storages/mongo.ts`) filter NHIs out, so
diff --git a/tests/features/nhis.api.spec.ts b/tests/features/nhis.api.spec.ts
index 7ddee8bd..70319f9e 100644
--- a/tests/features/nhis.api.spec.ts
+++ b/tests/features/nhis.api.spec.ts
@@ -356,27 +356,29 @@ test('nhi provider is validated at create and patch time', async () => {
   await ax.patch(`/api/organizations/${org.id}/nhis/${nhi.id}`, { name: 'Renamed validated agent' })
 })
 
-test('NHIs do not consume a member slot in the organization limits', async () => {
-  const { ax, user } = await createUser('nhi-limits@test.com')
+test('NHIs consume a member slot in the organization limits', async () => {
+  const { ax } = await createUser('nhi-limits@test.com')
   const org = (await ax.post('/api/organizations', { name: 'NHI limits org' })).data
   ax.setOrg(org.id)
+  const { ax: adminAx } = await createUser('admin@test.com', true)
+  const getConsumption = async () => (await ax.get(`/api/limits/organization/${org.id}`)).data.store_nb_members.consumption
 
   // reading the limits is what creates the denormalized counter
-  assert.equal((await ax.get(`/api/limits/organization/${org.id}`)).data.store_nb_members.consumption, 1)
-
-  await ax.post(`/api/organizations/${org.id}/nhis`, nhiBody())
+  assert.equal(await getConsumption(), 1)
 
-  // deleting the last human recomputes the counter: the NHI must not hold the org at 1 member,
-  // consistently with the member listing that excludes NHIs by default
-  const { ax: adminAx } = await createUser('admin@test.com', true)
-  await adminAx.delete(`/api/users/${user.id}`)
+  const nhi = (await ax.post(`/api/organizations/${org.id}/nhis`, nhiBody())).data
+  assert.equal(await getConsumption(), 2)
 
-  const orgLimits = (await adminAx.get('/api/limits', { params: { type: 'organization', id: org.id } })).data.results[0]
-  assert.equal(orgLimits.store_nb_members.consumption, 0)
+  // a full org refuses another NHI, like it refuses another invitation
+  await adminAx.post(`/api/limits/organization/${org.id}`, { store_nb_members: { limit: 2, consumption: 2 }, lastUpdate: new Date().toISOString() })
+  await assert.rejects(ax.post(`/api/organizations/${org.id}/nhis`, nhiBody({ name: 'Second agent' })), { status: 429 })
+  assert.equal((await ax.get(`/api/organizations/${org.id}/nhis`)).data.count, 1)
 
-  // the creator is deleted above, so DELETE /api/test-env cannot scope this org by created.id
-  // any more -- drop it here, or it accumulates across runs and pollutes name-based org searches
-  await adminAx.delete(`/api/organizations/${org.id}`)
+  // deleting the NHI frees its slot
+  await ax.delete(`/api/organizations/${org.id}/nhis/${nhi.id}`)
+  assert.equal(await getConsumption(), 1)
+  await ax.post(`/api/organizations/${org.id}/nhis`, nhiBody({ name: 'Second agent' }))
+  assert.equal(await getConsumption(), 2)
 })
 
 test('nhi token exchange is restricted to the declared allowedIps', async () => {
diff --git a/ui/src/components/add-nhi-menu.vue b/ui/src/components/add-nhi-menu.vue
index d220be81..d07a8150 100644
--- a/ui/src/components/add-nhi-menu.vue
+++ b/ui/src/components/add-nhi-menu.vue
@@ -22,7 +22,15 @@
       <v-card-title>
         {{ $t('pages.organization.addNhi') }}
       </v-card-title>
-      <template v-if="editNhi">
+      <v-card-text v-if="disableCreate">
+        <v-alert
+          :value="true"
+          type="warning"
+        >
+          {{ $t('pages.organization.disableInvite') }}
+        </v-alert>
+      </v-card-text>
+      <template v-else-if="editNhi">
         <v-card-text>
           <v-form
             ref="createForm"
@@ -138,8 +146,10 @@ import type { VForm } from 'vuetify/components'
 const { sendUiNotif } = useUiNotif()
 const { t } = useI18n()
 
-const { orga } = defineProps({
-  orga: { type: Object as () => Organization, required: true }
+const { orga, disableCreate } = defineProps({
+  orga: { type: Object as () => Organization, required: true },
+  // NHIs consume a member slot, so the members quota gates their creation too
+  disableCreate: { type: Boolean, default: false }
 })
 const { roleItems } = useRoleLabels(() => orga)
 const emit = defineEmits(['change'])
diff --git a/ui/src/components/organization-nhis.vue b/ui/src/components/organization-nhis.vue
index 7fb9b71f..114552a8 100644
--- a/ui/src/components/organization-nhis.vue
+++ b/ui/src/components/organization-nhis.vue
@@ -16,7 +16,8 @@
         <add-nhi-menu
           v-if="adminMode"
           :orga="orga"
-          @change="fetchNhis.refresh()"
+          :disable-create="disableCreate"
+          @change="onChange"
         />
         <v-tooltip location="right">
           <template #activator="{props}">
@@ -92,7 +93,7 @@
               <edit-nhi-menu
                 :orga="orga"
                 :nhi="nhi"
-                @change="fetchNhis.refresh()"
+                @change="onChange"
               />
             </v-list-item-action>
             <v-list-item-action
@@ -102,7 +103,7 @@
               <delete-nhi-menu
                 :orga="orga"
                 :nhi="nhi"
-                @change="fetchNhis.refresh()"
+                @change="onChange"
               />
             </v-list-item-action>
           </template>
@@ -121,12 +122,17 @@ import { useClipboard } from '@vueuse/core'
 // Progressive rollout: normal org admins get a read-only view, and only once at least
 // one NHI exists (the whole section is hidden otherwise). Only superadmins see the
 // create/edit/delete controls. This is a UI gate only — the API stays org-admin scoped.
-const { orga } = defineProps({
+const { orga, nbMembersLimits } = defineProps({
   orga: {
     type: Object as () => Organization,
     required: true
+  },
+  nbMembersLimits: {
+    type: Object as () => { limit: number, consumption: number } | undefined,
+    default: undefined
   }
 })
+const emit = defineEmits(['change'])
 const { roleLabel } = useRoleLabels(() => orga)
 
 const { copy } = useClipboard()
@@ -135,6 +141,12 @@ const adminMode = computed(() => !!session.user.value?.adminMode)
 
 const fetchNhis = useFetch<{ count: number, results: any[] }>(`${$apiPath}/organizations/${orga.id}/nhis`)
 const nhis = computed(() => fetchNhis.data.value)
+const disableCreate = computed(() => !nbMembersLimits || (nbMembersLimits.limit > 0 && nbMembersLimits.consumption >= nbMembersLimits.limit))
+// NHIs count in the members quota, let the parent refresh the limits it shares with the members list
+const onChange = () => {
+  fetchNhis.refresh()
+  emit('change')
+}
 // cache-buster tied to list refreshes so an avatar uploaded through the edit dialog
 // shows up on the next change event instead of the browser's cached image
 const avatarsTimestamp = ref(Date.now())
diff --git a/ui/src/pages/organization/[id]/index.vue b/ui/src/pages/organization/[id]/index.vue
index 2eab3623..1b0b6945 100644
--- a/ui/src/pages/organization/[id]/index.vue
+++ b/ui/src/pages/organization/[id]/index.vue
@@ -154,6 +154,8 @@
     <organization-nhis
       v-if="$uiConfig.manageNhis && orgRole === 'admin'"
       :orga="orga"
+      :nb-members-limits="limits.data.value?.store_nb_members"
+      @change="limits.refresh()"
     />
   </v-container>
 </template>