diff --git a/gateway/platforms/bluebubbles.py b/gateway/platforms/bluebubbles.py
index d4adbc7315..c3aae523ef 100644
--- a/gateway/platforms/bluebubbles.py
+++ b/gateway/platforms/bluebubbles.py
@@ -433,8 +433,15 @@ class BlueBubblesAdapter(BasePlatformAdapter):
 
         If *target* already contains a semicolon (raw GUID format like
         ``iMessage;-;user@example.com``), it is returned as-is.  Otherwise
-        the adapter queries the BlueBubbles chat list and matches on
-        ``chatIdentifier`` or participant address.
+        the adapter queries the BlueBubbles chat list and matches strictly
+        on ``chatIdentifier`` / ``identifier``.
+
+        Participant membership is intentionally NOT used as a fallback:
+        the same contact can appear in a 1:1 DM and in any number of group
+        chats, so a participant match would let an outbound DM reply leak
+        into a group thread (see #24157). When no exact chat identity
+        matches, return ``None`` and let the caller create a fresh DM
+        explicitly via ``_create_chat_for_handle``.
         """
         target = (target or "").strip()
         if not target:
@@ -459,12 +466,6 @@ class BlueBubblesAdapter(BasePlatformAdapter):
                         while len(self._guid_cache) > _GUID_CACHE_SIZE:
                             self._guid_cache.popitem(last=False)
                     return guid
-                for part in chat.get("participants", []) or []:
-                    if (part.get("address") or "").strip() == target and guid:
-                        self._guid_cache[target] = guid
-                        while len(self._guid_cache) > _GUID_CACHE_SIZE:
-                            self._guid_cache.popitem(last=False)
-                        return guid
         except Exception:
             pass
         return None
diff --git a/tests/gateway/test_bluebubbles.py b/tests/gateway/test_bluebubbles.py
index 7d4a71378c..11358ab2b8 100644
--- a/tests/gateway/test_bluebubbles.py
+++ b/tests/gateway/test_bluebubbles.py
@@ -426,6 +426,110 @@ class TestBlueBubblesGuidResolution:
         )
         assert result is None
 
+    @pytest.mark.asyncio
+    async def test_exact_chat_identifier_match_returns_dm_guid(self, monkeypatch):
+        """A 1:1 DM whose chatIdentifier equals the target resolves to its guid."""
+        adapter = _make_adapter(monkeypatch)
+
+        async def fake_api_post(path, payload):
+            return {
+                "data": [
+                    {
+                        "guid": "iMessage;-;user@example.com",
+                        "chatIdentifier": "user@example.com",
+                        "participants": [{"address": "user@example.com"}],
+                    }
+                ]
+            }
+
+        monkeypatch.setattr(adapter, "_api_post", fake_api_post)
+        result = await adapter._resolve_chat_guid("user@example.com")
+        assert result == "iMessage;-;user@example.com"
+
+    @pytest.mark.asyncio
+    async def test_participant_only_match_does_not_resolve_to_group(self, monkeypatch):
+        """Regression for #24157: contact appearing as a participant in a group
+        chat must NOT be selected when no DM with that exact chatIdentifier exists.
+
+        Otherwise an outbound DM reply leaks into the group thread.
+        """
+        adapter = _make_adapter(monkeypatch)
+
+        async def fake_api_post(path, payload):
+            return {
+                "data": [
+                    {
+                        "guid": "iMessage;+;chat0000000000-family-group",
+                        "chatIdentifier": "chat0000000000",
+                        "participants": [
+                            {"address": "user@example.com"},
+                            {"address": "+15555550100"},
+                        ],
+                    }
+                ]
+            }
+
+        monkeypatch.setattr(adapter, "_api_post", fake_api_post)
+        result = await adapter._resolve_chat_guid("user@example.com")
+        assert result is None, (
+            "participant-only match must not resolve to a group GUID — DM "
+            "replies would leak into the group thread"
+        )
+
+    @pytest.mark.asyncio
+    async def test_dm_chosen_over_group_when_both_contain_contact(self, monkeypatch):
+        """Even when a group chat is returned BEFORE a DM in the query result,
+        the resolver must lock onto the DM by chatIdentifier and not the
+        group via participant fallback.
+        """
+        adapter = _make_adapter(monkeypatch)
+
+        async def fake_api_post(path, payload):
+            return {
+                "data": [
+                    {
+                        "guid": "iMessage;+;chat0000000000-family-group",
+                        "chatIdentifier": "chat0000000000",
+                        "participants": [{"address": "user@example.com"}],
+                    },
+                    {
+                        "guid": "iMessage;-;user@example.com",
+                        "chatIdentifier": "user@example.com",
+                        "participants": [{"address": "user@example.com"}],
+                    },
+                ]
+            }
+
+        monkeypatch.setattr(adapter, "_api_post", fake_api_post)
+        result = await adapter._resolve_chat_guid("user@example.com")
+        assert result == "iMessage;-;user@example.com"
+
+    @pytest.mark.asyncio
+    async def test_unresolved_target_is_not_cached(self, monkeypatch):
+        """When no exact match is found, the resolver must NOT cache anything.
+
+        Otherwise a later attempt — after the DM has been created — would
+        keep returning the stale ``None`` from cache. Also guards against a
+        latent variant of #24157 where a group GUID could be cached under a
+        bare address key and persist across calls.
+        """
+        adapter = _make_adapter(monkeypatch)
+
+        async def fake_api_post(path, payload):
+            return {
+                "data": [
+                    {
+                        "guid": "iMessage;+;chat0000000000-family-group",
+                        "chatIdentifier": "chat0000000000",
+                        "participants": [{"address": "user@example.com"}],
+                    }
+                ]
+            }
+
+        monkeypatch.setattr(adapter, "_api_post", fake_api_post)
+        await adapter._resolve_chat_guid("user@example.com")
+        assert "user@example.com" not in adapter._guid_cache
+
 
 class TestBlueBubblesAttachmentDownload:
     """Verify _download_attachment routes to the correct cache helper."""