fix(gateway): only session-discover channel targets for connected platforms (#60574)

Session-based channel discovery resurrected historical origins for
platforms with no connected adapter, exposing stale send_message
targets that can no longer deliver. Gate both the enum loop and the
plugin-registry loop on the live adapter set.

Surgical reapply of the channel-directory portion of PR #25959 (branch
was 6.5k commits stale; the text-batching delay changes bundled there
were dropped - separate concern, defaults have since been retuned on
main).

Co-authored-by: Marco-Olivier Lavoie <marcolivier@gmail.com>

gateway/channel_directory.py

@@ -128,21 +128,34 @@ async def build_channel_directory(adapters: Dict[Any, Any]) -> Dict[str, Any]:
             logger.warning("Channel directory: failed to build %s: %s", platform.value, e)
 
     # Platforms that don't support direct channel enumeration get session-based
-    # discovery automatically.  Skip infrastructure entries that aren't messaging
-    # platforms — everything else falls through to _build_from_sessions().
+    # discovery automatically, but only for platforms connected in THIS gateway
+    # process. Historical session origins for disabled/decommissioned platforms
+    # must not be resurrected into the active send-target directory (stale
+    # targets make send_message route to platforms that can no longer deliver).
     _SKIP_SESSION_DISCOVERY = frozenset({"local", "api_server", "webhook"})
+    adapter_platform_names = {getattr(p, "value", str(p)) for p in adapters}
     for plat in Platform:
         plat_name = plat.value
-        if plat_name in _SKIP_SESSION_DISCOVERY or plat_name in platforms:
+        if (
+            plat_name in _SKIP_SESSION_DISCOVERY
+            or plat_name in platforms
+            or plat_name not in adapter_platform_names
+        ):
             continue
         platforms[plat_name] = _build_from_sessions(plat_name)
 
     # Include plugin-registered platforms (dynamic enum members aren't in
-    # Platform.__members__, so the loop above misses them).
+    # Platform.__members__, so the loop above misses them). Same
+    # connected-only rule: don't expose stale session targets for plugins
+    # that are not loaded.
     try:
         from gateway.platform_registry import platform_registry
         for entry in platform_registry.plugin_entries():
-            if entry.name not in _SKIP_SESSION_DISCOVERY and entry.name not in platforms:
+            if (
+                entry.name not in _SKIP_SESSION_DISCOVERY
+                and entry.name not in platforms
+                and entry.name in adapter_platform_names
+            ):
                 platforms[entry.name] = _build_from_sessions(entry.name)
     except Exception:
         pass

tests/gateway/test_channel_directory_connected_only.py

@@ -0,0 +1,46 @@
+"""Session-based channel discovery must not resurrect disconnected platforms.
+
+Surgical reapply of the directory portion of PR #25959: historical session
+origins for platforms with no connected adapter must not become active
+send_message targets."""
+
+import asyncio
+from unittest.mock import patch
+
+from gateway.channel_directory import build_channel_directory
+from gateway.platforms.base import Platform
+
+
+def test_does_not_resurrect_disconnected_platforms_from_session_history(tmp_path, monkeypatch):
+    cache_file = tmp_path / "channel_directory.json"
+
+    calls = []
+
+    def fake_build_from_sessions(plat_name):
+        calls.append(plat_name)
+        return {"channels": [{"id": "1", "name": "old"}]}
+
+    with patch("gateway.channel_directory._build_from_sessions", side_effect=fake_build_from_sessions), \
+         patch("gateway.channel_directory.DIRECTORY_PATH", cache_file):
+        # Only telegram is connected; no discord/slack/whatsapp adapters.
+        directory = asyncio.run(build_channel_directory({Platform.TELEGRAM: object()}))
+
+    plats = directory["platforms"]
+    assert "telegram" in plats
+    # Disconnected platforms must not appear via session discovery.
+    for stale in ("whatsapp", "signal", "matrix"):
+        assert stale not in plats, f"{stale} resurrected from session history"
+    assert set(calls) <= {"telegram"}
+
+
+def test_connected_platform_still_uses_session_discovery(tmp_path):
+    cache_file = tmp_path / "channel_directory.json"
+
+    with patch(
+        "gateway.channel_directory._build_from_sessions",
+        return_value={"channels": []},
+    ) as mock_sessions, patch("gateway.channel_directory.DIRECTORY_PATH", cache_file):
+        directory = asyncio.run(build_channel_directory({Platform.TELEGRAM: object()}))
+
+    assert "telegram" in directory["platforms"]
+    mock_sessions.assert_any_call("telegram")