fix(send_message): constrain opaque plugin fallback

tests/tools/test_send_message_tool.py

@@ -275,6 +275,143 @@ def _ensure_slack_mock(monkeypatch):
 
 
 class TestSendMessageTool:
+    def test_resolved_opaque_plugin_target_uses_directory_id(self):
+        from gateway.platform_registry import PlatformEntry, platform_registry
+
+        platform_name = "opaque-resolved-test"
+        entry = PlatformEntry(
+            name=platform_name,
+            label="Opaque resolved test",
+            adapter_factory=lambda cfg: None,
+            check_fn=lambda: True,
+        )
+        platform_registry.register(entry)
+        platform = Platform(platform_name)
+        pconfig = SimpleNamespace(enabled=True, token=None, extra={})
+        config = SimpleNamespace(
+            platforms={platform: pconfig},
+            get_home_channel=lambda _platform: None,
+        )
+        try:
+            with patch("gateway.config.load_gateway_config", return_value=config), \
+                 patch("tools.interrupt.is_interrupted", return_value=False), \
+                 patch(
+                     "gateway.channel_directory.resolve_channel_name",
+                     return_value="opaque:directory-id",
+                 ), \
+                 patch("model_tools._run_async", side_effect=_run_async_immediately), \
+                 patch(
+                     "tools.send_message_tool._send_to_platform",
+                     new=AsyncMock(return_value={"success": True}),
+                 ) as send_mock, \
+                 patch("gateway.mirror.mirror_to_session", return_value=True):
+                result = json.loads(
+                    send_message_tool(
+                        {
+                            "action": "send",
+                            "target": f"{platform_name}:Friendly name",
+                            "message": "hello",
+                        }
+                    )
+                )
+        finally:
+            platform_registry.unregister(platform_name)
+
+        assert result["success"] is True
+        send_mock.assert_awaited_once_with(
+            platform,
+            pconfig,
+            "opaque:directory-id",
+            "hello",
+            thread_id=None,
+            media_files=[],
+            force_document=False,
+        )
+
+    def test_unresolved_opaque_plugin_target_passes_through_verbatim(self):
+        from gateway.platform_registry import PlatformEntry, platform_registry
+
+        platform_name = "opaque-verbatim-test"
+        entry = PlatformEntry(
+            name=platform_name,
+            label="Opaque verbatim test",
+            adapter_factory=lambda cfg: None,
+            check_fn=lambda: True,
+        )
+        platform_registry.register(entry)
+        platform = Platform(platform_name)
+        pconfig = SimpleNamespace(enabled=True, token=None, extra={})
+        config = SimpleNamespace(
+            platforms={platform: pconfig},
+            get_home_channel=lambda _platform: None,
+        )
+        try:
+            with patch("gateway.config.load_gateway_config", return_value=config), \
+                 patch("tools.interrupt.is_interrupted", return_value=False), \
+                 patch(
+                     "gateway.channel_directory.resolve_channel_name",
+                     return_value=None,
+                 ), \
+                 patch("model_tools._run_async", side_effect=_run_async_immediately), \
+                 patch(
+                     "tools.send_message_tool._send_to_platform",
+                     new=AsyncMock(return_value={"success": True}),
+                 ) as send_mock, \
+                 patch("gateway.mirror.mirror_to_session", return_value=True):
+                result = json.loads(
+                    send_message_tool(
+                        {
+                            "action": "send",
+                            "target": f"{platform_name}:dm:panyaozhen",
+                            "message": "hello",
+                        }
+                    )
+                )
+        finally:
+            platform_registry.unregister(platform_name)
+
+        assert result["success"] is True
+        send_mock.assert_awaited_once_with(
+            platform,
+            pconfig,
+            "dm:panyaozhen",
+            "hello",
+            thread_id=None,
+            media_files=[],
+            force_document=False,
+        )
+
+    def test_unresolved_builtin_target_keeps_directory_error(self):
+        config, _telegram_cfg = _make_config()
+
+        with patch("gateway.config.load_gateway_config", return_value=config), \
+             patch("gateway.channel_directory.resolve_channel_name", return_value=None), \
+             patch(
+                 "tools.send_message_tool._send_to_platform",
+                 new=AsyncMock(return_value={"success": True}),
+             ) as send_mock:
+            result = json.loads(
+                send_message_tool(
+                    {
+                        "action": "send",
+                        "target": "telegram:missing-room",
+                        "message": "hello",
+                    }
+                )
+            )
+
+        assert result == {
+            "error": "Could not resolve 'missing-room' on telegram. "
+            "Use send_message(action='list') to see available targets."
+        }
+        send_mock.assert_not_awaited()
+
+    def test_ntfy_topic_target_is_explicit(self):
+        chat_id, thread_id, is_explicit = _parse_target_ref("ntfy", "alerts-channel")
+
+        assert chat_id == "alerts-channel"
+        assert thread_id is None
+        assert is_explicit is True
 
     def test_ntfy_topic_target_bypasses_channel_directory(self):
         ntfy_platform = Platform("ntfy")

tools/send_message_tool.py

@@ -453,10 +453,10 @@ def _handle_send(args):
                 # core.  Their adapter owns final target validation.
                 chat_id = target_ref
             elif resolution_failed:
-                return json.dumps({
-                    "error": f"Could not resolve '{target_ref}' on {platform_name}. "
+                return tool_error(
+                    f"Could not resolve '{target_ref}' on {platform_name}. "
                     f"Try using a numeric channel ID instead."
-                })
+                )
             else:
                 return tool_error(
                     f"Could not resolve '{target_ref}' on {platform_name}. "