diff --git a/navi/api/websocket.py b/navi/api/websocket.py
index 758104e..3862111 100644
--- a/navi/api/websocket.py
+++ b/navi/api/websocket.py
@@ -563,6 +563,7 @@
                     proposal_id,
                     accepted=action == "accept",
                     user_id=actor_id,
+                    is_admin=is_admin,
                 )
                 await websocket.send_json({
                     "type": "skill_proposal_decided",
diff --git a/navi/skills/store.py b/navi/skills/store.py
index ef3bcb3..7105cd7 100644
--- a/navi/skills/store.py
+++ b/navi/skills/store.py
@@ -574,15 +574,19 @@
         *,
         accepted: bool,
         user_id: str = "",
+        is_admin: bool = False,
     ) -> tuple[SkillProposal | None, SkillEntry | None, str]:
         """Accept or reject a proposal.
 
         Accepting writes the catalog row (or a new version of the protocol the
         proposal replaces) with ``user_id`` as the author — the user's click is
         the authorization, so the version history names the person who agreed to
-        the procedure. Returns ``(proposal, entry, error)``: an unknown id gives
-        ``(None, None, message)``; a document the store refuses leaves the
-        proposal pending and returns the reason.
+        the procedure. A replacement is authorized again at the click: the
+        protocol may have changed hands (a personal one promoted to shared) while
+        the proposal sat pending. Returns ``(proposal, entry, error)``: an unknown
+        id gives ``(None, None, message)``; a document — or a protocol the actor
+        may no longer write — the store refuses leaves the proposal pending and
+        returns the reason.
         """
         await self._ensure_ready()
         proposal = await self.get_proposal(proposal_id)
@@ -599,6 +603,23 @@
 
         try:
             if proposal.replaces_id:
+                # Ownership was proven when the proposal was written; it has to
+                # hold at the click too, because the entry can be promoted to
+                # shared (losing its owner) in the meantime. A shared protocol
+                # is then the hive's, and only an admin may replace it.
+                current = await self.get(proposal.replaces_id)
+                if current is None or current.kind != "protocol":
+                    raise SkillError("the protocol this proposal would replace is gone")
+                if current.visibility == "shared":
+                    if not is_admin:
+                        raise SkillError(
+                            "the protocol is shared now; only an admin can replace it"
+                        )
+                elif current.owner_id != user_id:
+                    raise SkillError(
+                        "the protocol changed hands while this proposal was pending; "
+                        "only its owner can replace it"
+                    )
                 entry = await self.update(
                     proposal.replaces_id,
                     content=proposal.content,
diff --git a/tests/unit/skills/test_skill_store.py b/tests/unit/skills/test_skill_store.py
index e2bcde0..d0a8f7e 100644
--- a/tests/unit/skills/test_skill_store.py
+++ b/tests/unit/skills/test_skill_store.py
@@ -321,6 +321,7 @@
     async def test_accepting_a_replacement_bumps_that_protocol(self):
         store, conn = _store()
         conn.enqueue(self._proposal_row(replaces_id="sk1"))
+        conn.enqueue(_row(kind="protocol", version=1))            # ownership re-check
         conn.enqueue(_row(kind="protocol", version=1))            # current
         conn.enqueue("OK")                            # history row
         conn.enqueue("OK")                            # update skills
@@ -333,6 +334,42 @@
         assert entry.version == 2
         assert any("UPDATE skills SET" in c[1] for c in conn.calls)
 
+    async def test_a_replacement_promoted_to_shared_needs_an_admin(self):
+        # The owner proposed a change while the protocol was personal; an admin
+        # then promoted it to the hive. The owner's click must no longer write.
+        store, conn = _store()
+        conn.enqueue(self._proposal_row(replaces_id="sk1"))
+        conn.enqueue(_row(kind="protocol", visibility="shared", owner_id=""))
+        conn.enqueue("OK")                            # store the error text
+        conn.enqueue(self._proposal_row(
+            replaces_id="sk1", error="the protocol is shared now; only an admin",
+        ))
+
+        _, entry, error = await store.decide_proposal("pr1", accepted=True, user_id="u1")
+
+        assert entry is None
+        assert "only an admin can replace it" in error
+        assert not any("UPDATE skills SET" in c[1] for c in conn.calls)
+
+    async def test_an_admin_still_accepts_a_replacement_of_a_shared_protocol(self):
+        store, conn = _store()
+        conn.enqueue(self._proposal_row(replaces_id="sk1"))
+        conn.enqueue(_row(kind="protocol", visibility="shared", owner_id=""))
+        conn.enqueue(_row(kind="protocol", visibility="shared", owner_id="", version=1))
+        conn.enqueue("OK")                            # history row
+        conn.enqueue("OK")                            # update skills
+        conn.enqueue(_row(kind="protocol", visibility="shared", owner_id="", version=2))
+        conn.enqueue("OK")                            # mark accepted
+        conn.enqueue(self._proposal_row(status="accepted", replaces_id="sk1", skill_id="sk1"))
+
+        _, entry, error = await store.decide_proposal(
+            "pr1", accepted=True, user_id="admin1", is_admin=True,
+        )
+
+        assert error == ""
+        assert entry.version == 2
+        assert any("UPDATE skills SET" in c[1] for c in conn.calls)
+
     async def test_rejecting_leaves_the_catalog_untouched(self):
         store, conn = _store()
         conn.enqueue(self._proposal_row())