diff --git a/src/govoplan_scheduling/backend/router.py b/src/govoplan_scheduling/backend/router.py
index 8e5867d..7791f76 100644
--- a/src/govoplan_scheduling/backend/router.py
+++ b/src/govoplan_scheduling/backend/router.py
@@ -19,6 +19,7 @@ from govoplan_scheduling.backend.schemas import (
     SchedulingDecisionRequest,
     SchedulingInvitationActionRequest,
     SchedulingInvitationActionResponse,
+    SchedulingInvitationRevokeRequest,
     SchedulingNotificationCreateRequest,
     SchedulingNotificationListResponse,
     SchedulingNotificationResponse,
@@ -482,6 +483,7 @@ def api_issue_scheduling_participant_invitation(
             tenant_id=principal.tenant_id,
             request_id=request_id,
             participant_id=participant_id,
+            participant_revision=payload.participant_revision,
             action=payload.action,
         )
     except SchedulingError as exc:
@@ -543,6 +545,7 @@ def api_issue_scheduling_participant_invitation(
 def api_revoke_scheduling_participant_invitation(
     request_id: str,
     participant_id: str,
+    payload: SchedulingInvitationRevokeRequest,
     response: Response,
     session: Session = Depends(get_session),
     principal: ApiPrincipal = Depends(get_api_principal),
@@ -558,6 +561,7 @@ def api_revoke_scheduling_participant_invitation(
             tenant_id=principal.tenant_id,
             request_id=request_id,
             participant_id=participant_id,
+            participant_revision=payload.participant_revision,
         )
     except SchedulingError as exc:
         raise _scheduling_http_error(exc) from exc
diff --git a/src/govoplan_scheduling/backend/schemas.py b/src/govoplan_scheduling/backend/schemas.py
index 525c289..e6de55a 100644
--- a/src/govoplan_scheduling/backend/schemas.py
+++ b/src/govoplan_scheduling/backend/schemas.py
@@ -523,6 +523,31 @@ class SchedulingInvitationActionRequest(BaseModel):
     model_config = ConfigDict(extra="forbid")
 
     action: Literal["copy", "send"]
+    participant_revision: str = Field(
+        min_length=64,
+        max_length=64,
+        pattern=r"^[0-9a-f]{64}$",
+        description=(
+            "Semantic revision from the participant management projection; "
+            "stale actions are rejected before rotating or delivering a link."
+        ),
+    )
+
+
+class SchedulingInvitationRevokeRequest(BaseModel):
+    """Revoke the link represented by one current participant projection."""
+
+    model_config = ConfigDict(extra="forbid")
+
+    participant_revision: str = Field(
+        min_length=64,
+        max_length=64,
+        pattern=r"^[0-9a-f]{64}$",
+        description=(
+            "Semantic revision from the participant management projection; "
+            "stale revocations are rejected before changing access."
+        ),
+    )
 
 
 class SchedulingInvitationActionResponse(BaseModel):
diff --git a/src/govoplan_scheduling/backend/service.py b/src/govoplan_scheduling/backend/service.py
index 54d035b..1b8f889 100644
--- a/src/govoplan_scheduling/backend/service.py
+++ b/src/govoplan_scheduling/backend/service.py
@@ -2866,6 +2866,19 @@ def _participant_for_invitation_action(
     return participant
 
 
+def _require_current_invitation_participant_revision(
+    participant: SchedulingParticipant,
+    *,
+    participant_revision: str,
+) -> None:
+    """Reject a stale invitation command while the participant row is locked."""
+
+    if participant_revision != scheduling_participant_revision(participant):
+        raise SchedulingConflictError(
+            "Scheduling participant invitation changed; reload and try again"
+        )
+
+
 def _new_public_invitation_expiry(
     request: SchedulingRequest,
 ) -> datetime | None:
@@ -2904,6 +2917,7 @@ def issue_scheduling_participant_invitation(
     tenant_id: str,
     request_id: str,
     participant_id: str,
+    participant_revision: str,
     action: str,
 ) -> SchedulingInvitationActionResult:
     """Rotate one bearer link for explicit copy or immediate delivery.
@@ -2925,6 +2939,10 @@ def issue_scheduling_participant_invitation(
         request,
         participant_id=participant_id,
     )
+    _require_current_invitation_participant_revision(
+        participant,
+        participant_revision=participant_revision,
+    )
     if request.poll_id is None:
         raise SchedulingError("Scheduling invitation action is unavailable")
     participation_provider = _poll_participation_provider()
@@ -3016,8 +3034,9 @@ def revoke_scheduling_participant_invitation(
     tenant_id: str,
     request_id: str,
     participant_id: str,
+    participant_revision: str,
 ) -> SchedulingInvitationActionResult:
-    """Immediately revoke the current link; exact repeats are safe no-ops."""
+    """Revoke the current link; refreshed no-link projections replay safely."""
 
     request = _lock_scheduling_request(
         session,
@@ -3029,6 +3048,10 @@ def revoke_scheduling_participant_invitation(
         request,
         participant_id=participant_id,
     )
+    _require_current_invitation_participant_revision(
+        participant,
+        participant_revision=participant_revision,
+    )
     invitation_id = participant.poll_invitation_id
     replayed = invitation_id is None
     if invitation_id is not None:
diff --git a/tests/test_response_editing.py b/tests/test_response_editing.py
index 2d95615..9ff7e27 100644
--- a/tests/test_response_editing.py
+++ b/tests/test_response_editing.py
@@ -214,6 +214,7 @@ class SchedulingResponseEditingTests(unittest.TestCase):
             tenant_id=request.tenant_id,
             request_id=request.id,
             participant_id=participant.id,
+            participant_revision=scheduling_participant_revision(participant),
             action="copy",
         )
         self.assertIsNotNone(result.action_url)
@@ -1753,6 +1754,7 @@ class SchedulingResponseEditingTests(unittest.TestCase):
                     tenant_id=request.tenant_id,
                     request_id=request.id,
                     participant_id=participant.id,
+                    participant_revision=scheduling_participant_revision(participant),
                     action="copy",
                 )
 
diff --git a/tests/test_service.py b/tests/test_service.py
index 628e98e..c231f1f 100644
--- a/tests/test_service.py
+++ b/tests/test_service.py
@@ -43,6 +43,7 @@ from govoplan_scheduling.backend.schemas import (
     SchedulingCandidateSlotInput,
     SchedulingDecisionRequest,
     SchedulingInvitationActionRequest,
+    SchedulingInvitationRevokeRequest,
     SchedulingParticipantInput,
     SchedulingPublicParticipationAccessRequest,
     SchedulingPublicParticipationSubmitRequest,
@@ -82,6 +83,7 @@ from govoplan_scheduling.backend.service import (
     open_scheduling_request,
     require_visible_scheduling_results,
     scheduling_request_summary,
+    scheduling_participant_revision,
     scheduling_slot_revision,
     submit_public_scheduling_participation,
     update_scheduling_request,
@@ -222,6 +224,7 @@ class SchedulingServiceTests(unittest.TestCase):
             tenant_id=request.tenant_id,
             request_id=request.id,
             participant_id=participant.id,
+            participant_revision=scheduling_participant_revision(participant),
             action="copy",
         )
         self.assertIsNotNone(result.action_url)
@@ -1517,6 +1520,7 @@ class SchedulingServiceTests(unittest.TestCase):
                     tenant_id=request.tenant_id,
                     request_id=request.id,
                     participant_id=participant.id,
+                    participant_revision=scheduling_participant_revision(participant),
                     action="send",
                 )
                 for participant in request.participants
@@ -1576,6 +1580,7 @@ class SchedulingServiceTests(unittest.TestCase):
                 tenant_id=request.tenant_id,
                 request_id=request.id,
                 participant_id=participant.id,
+                participant_revision=scheduling_participant_revision(participant),
                 action="send",
             )
 
@@ -1625,6 +1630,7 @@ class SchedulingServiceTests(unittest.TestCase):
                 tenant_id=request.tenant_id,
                 request_id=request.id,
                 participant_id=participant.id,
+                participant_revision=scheduling_participant_revision(participant),
                 action="send",
             )
 
@@ -1644,6 +1650,142 @@ class SchedulingServiceTests(unittest.TestCase):
             request.id,
         )
 
+    def test_stale_copy_is_rejected_before_rotating_invitation(self) -> None:
+        request, _automatic_tokens = create_scheduling_request(
+            self.session,
+            tenant_id="tenant-1",
+            user_id="user-1",
+            payload=self._payload().model_copy(
+                update={"calendar": SchedulingCalendarPreferences()}
+            ),
+        )
+        participant = request.participants[0]
+        stale_revision = scheduling_participant_revision(participant)
+        self._issue_copy(request, participant)
+        invitation_id = participant.poll_invitation_id
+        organizer = self._principal("user-1", scopes={SCHEDULING_WRITE_SCOPE})
+
+        with (
+            patch("govoplan_scheduling.backend.router.audit_event") as audit,
+            self.assertRaises(HTTPException) as conflict,
+        ):
+            api_issue_scheduling_participant_invitation(
+                request.id,
+                participant.id,
+                SchedulingInvitationActionRequest(
+                    action="copy",
+                    participant_revision=stale_revision,
+                ),
+                Response(),
+                session=self.session,
+                principal=organizer,
+            )
+
+        self.assertEqual(conflict.exception.status_code, 409)
+        self.assertEqual(participant.poll_invitation_id, invitation_id)
+        invitation = self.session.query(PollInvitation).filter(
+            PollInvitation.id == invitation_id
+        ).one()
+        self.assertIsNone(invitation.revoked_at)
+        audit.assert_not_called()
+
+    def test_stale_send_is_rejected_before_delivery_or_rotation(self) -> None:
+        class CapturingNotificationProvider:
+            def __init__(self) -> None:
+                self.requests = []
+
+            def enqueue_notification(self, _session, request, *, enqueue_delivery):
+                self.requests.append(request)
+                return {"id": "notification-1", "status": "queued"}
+
+        provider = CapturingNotificationProvider()
+        request, _automatic_tokens = create_scheduling_request(
+            self.session,
+            tenant_id="tenant-1",
+            user_id="user-1",
+            payload=self._payload().model_copy(
+                update={"calendar": SchedulingCalendarPreferences()}
+            ),
+        )
+        participant = request.participants[0]
+        stale_revision = scheduling_participant_revision(participant)
+        self._issue_copy(request, participant)
+        invitation_id = participant.poll_invitation_id
+        organizer = self._principal("user-1", scopes={SCHEDULING_WRITE_SCOPE})
+
+        with (
+            patch(
+                "govoplan_scheduling.backend.service.notification_dispatch_provider",
+                return_value=provider,
+            ),
+            patch("govoplan_scheduling.backend.router.audit_event") as audit,
+            self.assertRaises(HTTPException) as conflict,
+        ):
+            api_issue_scheduling_participant_invitation(
+                request.id,
+                participant.id,
+                SchedulingInvitationActionRequest(
+                    action="send",
+                    participant_revision=stale_revision,
+                ),
+                Response(),
+                session=self.session,
+                principal=organizer,
+            )
+
+        self.assertEqual(conflict.exception.status_code, 409)
+        self.assertEqual(participant.poll_invitation_id, invitation_id)
+        invitation = self.session.query(PollInvitation).filter(
+            PollInvitation.id == invitation_id
+        ).one()
+        self.assertIsNone(invitation.revoked_at)
+        self.assertEqual(provider.requests, [])
+        self.assertEqual(
+            self.session.query(SchedulingNotification).filter(
+                SchedulingNotification.request_id == request.id
+            ).count(),
+            0,
+        )
+        audit.assert_not_called()
+
+    def test_stale_revoke_is_rejected_before_changing_access(self) -> None:
+        request, _automatic_tokens = create_scheduling_request(
+            self.session,
+            tenant_id="tenant-1",
+            user_id="user-1",
+            payload=self._payload().model_copy(
+                update={"calendar": SchedulingCalendarPreferences()}
+            ),
+        )
+        participant = request.participants[0]
+        stale_revision = scheduling_participant_revision(participant)
+        self._issue_copy(request, participant)
+        invitation_id = participant.poll_invitation_id
+        organizer = self._principal("user-1", scopes={SCHEDULING_WRITE_SCOPE})
+
+        with (
+            patch("govoplan_scheduling.backend.router.audit_event") as audit,
+            self.assertRaises(HTTPException) as conflict,
+        ):
+            api_revoke_scheduling_participant_invitation(
+                request.id,
+                participant.id,
+                SchedulingInvitationRevokeRequest(
+                    participant_revision=stale_revision,
+                ),
+                Response(),
+                session=self.session,
+                principal=organizer,
+            )
+
+        self.assertEqual(conflict.exception.status_code, 409)
+        self.assertEqual(participant.poll_invitation_id, invitation_id)
+        invitation = self.session.query(PollInvitation).filter(
+            PollInvitation.id == invitation_id
+        ).one()
+        self.assertIsNone(invitation.revoked_at)
+        audit.assert_not_called()
+
     def test_invitation_router_rotates_revokes_and_enforces_management_policy(self) -> None:
         request, automatic_tokens = create_scheduling_request(
             self.session,
@@ -1663,7 +1805,10 @@ class SchedulingServiceTests(unittest.TestCase):
             first = api_issue_scheduling_participant_invitation(
                 request.id,
                 participant.id,
-                SchedulingInvitationActionRequest(action="copy"),
+                SchedulingInvitationActionRequest(
+                    action="copy",
+                    participant_revision=scheduling_participant_revision(participant),
+                ),
                 response_headers,
                 session=self.session,
                 principal=organizer,
@@ -1688,7 +1833,10 @@ class SchedulingServiceTests(unittest.TestCase):
             api_issue_scheduling_participant_invitation(
                 request.id,
                 participant.id,
-                SchedulingInvitationActionRequest(action="copy"),
+                SchedulingInvitationActionRequest(
+                    action="copy",
+                    participant_revision=scheduling_participant_revision(participant),
+                ),
                 Response(),
                 session=self.session,
                 principal=unrelated_writer,
@@ -1713,7 +1861,10 @@ class SchedulingServiceTests(unittest.TestCase):
             rotated = api_issue_scheduling_participant_invitation(
                 request.id,
                 participant.id,
-                SchedulingInvitationActionRequest(action="copy"),
+                SchedulingInvitationActionRequest(
+                    action="copy",
+                    participant_revision=scheduling_participant_revision(participant),
+                ),
                 Response(),
                 session=self.session,
                 principal=administrator,
@@ -1737,6 +1888,9 @@ class SchedulingServiceTests(unittest.TestCase):
             revoked = api_revoke_scheduling_participant_invitation(
                 request.id,
                 participant.id,
+                SchedulingInvitationRevokeRequest(
+                    participant_revision=scheduling_participant_revision(participant),
+                ),
                 Response(),
                 session=self.session,
                 principal=organizer,
@@ -1744,6 +1898,9 @@ class SchedulingServiceTests(unittest.TestCase):
             replayed = api_revoke_scheduling_participant_invitation(
                 request.id,
                 participant.id,
+                SchedulingInvitationRevokeRequest(
+                    participant_revision=scheduling_participant_revision(participant),
+                ),
                 Response(),
                 session=self.session,
                 principal=organizer,
@@ -1793,7 +1950,12 @@ class SchedulingServiceTests(unittest.TestCase):
                 issued = api_issue_scheduling_participant_invitation(
                     request.id,
                     request.participants[0].id,
-                    SchedulingInvitationActionRequest(action="copy"),
+                    SchedulingInvitationActionRequest(
+                        action="copy",
+                        participant_revision=scheduling_participant_revision(
+                            request.participants[0]
+                        ),
+                    ),
                     Response(),
                     session=self.session,
                     principal=organizer,
@@ -1838,7 +2000,10 @@ class SchedulingServiceTests(unittest.TestCase):
             result = api_issue_scheduling_participant_invitation(
                 request.id,
                 participant.id,
-                SchedulingInvitationActionRequest(action="send"),
+                SchedulingInvitationActionRequest(
+                    action="send",
+                    participant_revision=scheduling_participant_revision(participant),
+                ),
                 Response(),
                 session=self.session,
                 principal=organizer,