diff --git a/adapter/matrix/store.py b/adapter/matrix/store.py
index d046640..34532a6 100644
--- a/adapter/matrix/store.py
+++ b/adapter/matrix/store.py
@@ -19,6 +19,19 @@ async def set_room_meta(store: StateStore, room_id: str, meta: dict) -> None:
     await store.set(f"{ROOM_META_PREFIX}{room_id}", meta)
 
 
+async def get_platform_chat_id(store: StateStore, room_id: str) -> str | None:
+    meta = await get_room_meta(store, room_id)
+    return meta.get("platform_chat_id") if meta else None
+
+
+async def set_platform_chat_id(
+    store: StateStore, room_id: str, platform_chat_id: str
+) -> None:
+    meta = await get_room_meta(store, room_id) or {}
+    meta["platform_chat_id"] = platform_chat_id
+    await set_room_meta(store, room_id, meta)
+
+
 async def get_user_meta(store: StateStore, matrix_user_id: str) -> dict | None:
     return await store.get(f"{USER_META_PREFIX}{matrix_user_id}")
 
diff --git a/tests/adapter/matrix/test_store.py b/tests/adapter/matrix/test_store.py
index 35f8131..6be84c4 100644
--- a/tests/adapter/matrix/test_store.py
+++ b/tests/adapter/matrix/test_store.py
@@ -5,12 +5,14 @@ import pytest
 from adapter.matrix.store import (
     clear_pending_confirm,
     get_pending_confirm,
+    get_platform_chat_id,
     get_room_meta,
     get_room_state,
     get_skills_message_id,
     get_user_meta,
     next_chat_id,
     set_pending_confirm,
+    set_platform_chat_id,
     set_room_meta,
     set_room_state,
     set_skills_message_id,
@@ -35,6 +37,27 @@ async def test_room_meta_roundtrip(store: InMemoryStore):
     assert await get_room_meta(store, "!r:m.org") == meta
 
 
+async def test_room_meta_roundtrip_with_platform_chat_id(store: InMemoryStore):
+    meta = {
+        "chat_id": "C1",
+        "matrix_user_id": "@alice:example.org",
+        "platform_chat_id": "chat-platform-1",
+    }
+    await set_room_meta(store, "!r:m.org", meta)
+    saved = await get_room_meta(store, "!r:m.org")
+    assert saved is not None
+    assert saved["platform_chat_id"] == "chat-platform-1"
+
+
+async def test_platform_chat_id_helpers_roundtrip(store: InMemoryStore):
+    await set_platform_chat_id(store, "!r:m.org", "chat-platform-1")
+
+    assert await get_platform_chat_id(store, "!r:m.org") == "chat-platform-1"
+    assert await get_room_meta(store, "!r:m.org") == {
+        "platform_chat_id": "chat-platform-1"
+    }
+
+
 async def test_room_meta_missing(store: InMemoryStore):
     assert await get_room_meta(store, "!nonexistent:m.org") is None