diff --git a/mergify_cli/ci/scopes/base_detector.py b/mergify_cli/ci/scopes/base_detector.py
index d9bb58a9..a48a8a9f 100644
--- a/mergify_cli/ci/scopes/base_detector.py
+++ b/mergify_cli/ci/scopes/base_detector.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import dataclasses
 import json
 import os
 import pathlib
@@ -64,7 +65,13 @@ def _detect_base_from_event(ev: dict[str, typing.Any]) -> str | None:
     return None
 
 
-def detect() -> str:
+@dataclasses.dataclass
+class Base:
+    ref: str
+    is_merge_queue: bool
+
+
+def detect() -> Base:
     event_path = os.environ.get("GITHUB_EVENT_PATH")
     event: dict[str, typing.Any] | None = None
     if event_path and pathlib.Path(event_path).is_file():
@@ -78,17 +85,17 @@ def detect() -> str:
         # 0) merge-queue PR override
         mq_sha = _detect_base_from_merge_queue_payload(event)
         if mq_sha:
-            return mq_sha
+            return Base(mq_sha, is_merge_queue=True)
 
         # 1) standard event payload
         event_sha = _detect_base_from_event(event)
         if event_sha:
-            return event_sha
+            return Base(event_sha, is_merge_queue=False)
 
     # 2) base ref (e.g., PR target branch)
     base_ref = os.environ.get("GITHUB_BASE_REF")
     if base_ref:
-        return base_ref
+        return Base(base_ref, is_merge_queue=False)
 
     msg = (
         "Could not detect base SHA. Ensure checkout has sufficient history "
diff --git a/mergify_cli/ci/scopes/cli.py b/mergify_cli/ci/scopes/cli.py
index f05d58e2..59eacbbe 100644
--- a/mergify_cli/ci/scopes/cli.py
+++ b/mergify_cli/ci/scopes/cli.py
@@ -45,6 +45,7 @@ class ScopeConfig(pydantic.BaseModel):
 
 class Config(pydantic.BaseModel):
     scopes: dict[ScopeName, ScopeConfig]
+    merge_queue_scope: str | None = "merge-queue"
 
     @classmethod
     def from_dict(cls, data: dict[str, typing.Any] | typing.Any) -> Config:  # noqa: ANN401
@@ -113,12 +114,18 @@ def detect(config_path: str) -> None:
     cfg = Config.from_yaml(config_path)
     base = base_detector.detect()
     try:
-        changed = changed_files.git_changed_files(base)
+        changed = changed_files.git_changed_files(base.ref)
     except changed_files.ChangedFilesError as e:
         raise ChangedFilesError(str(e))
     scopes_hit, per_scope = match_scopes(cfg, changed)
 
-    click.echo(f"Base: {base}")
+    all_scopes = set(cfg.scopes.keys())
+    if cfg.merge_queue_scope is not None:
+        all_scopes.add(cfg.merge_queue_scope)
+        if base.is_merge_queue:
+            scopes_hit.add(cfg.merge_queue_scope)
+
+    click.echo(f"Base: {base.ref}")
     if scopes_hit:
         click.echo("Scopes touched:")
         for s in sorted(scopes_hit):
@@ -129,4 +136,4 @@ def detect(config_path: str) -> None:
     else:
         click.echo("No scopes matched.")
 
-    maybe_write_github_outputs(cfg.scopes.keys(), scopes_hit)
+    maybe_write_github_outputs(all_scopes, scopes_hit)
diff --git a/mergify_cli/tests/ci/scopes/test_base_detector.py b/mergify_cli/tests/ci/scopes/test_base_detector.py
index 40ad7d9b..2d893b54 100644
--- a/mergify_cli/tests/ci/scopes/test_base_detector.py
+++ b/mergify_cli/tests/ci/scopes/test_base_detector.py
@@ -15,7 +15,7 @@ def test_detect_base_github_base_ref(
 
     result = base_detector.detect()
 
-    assert result == "main"
+    assert result == base_detector.Base("main", is_merge_queue=False)
 
 
 def test_detect_base_from_event_path(
@@ -35,7 +35,7 @@ def test_detect_base_from_event_path(
 
     result = base_detector.detect()
 
-    assert result == "abc123"
+    assert result == base_detector.Base("abc123", is_merge_queue=False)
 
 
 def test_detect_base_merge_queue_override(
@@ -56,7 +56,7 @@ def test_detect_base_merge_queue_override(
 
     result = base_detector.detect()
 
-    assert result == "xyz789"
+    assert result == base_detector.Base("xyz789", is_merge_queue=True)
 
 
 def test_detect_base_no_info(monkeypatch: pytest.MonkeyPatch) -> None:
diff --git a/mergify_cli/tests/ci/scopes/test_cli.py b/mergify_cli/tests/ci/scopes/test_cli.py
index 1180a832..21db571b 100644
--- a/mergify_cli/tests/ci/scopes/test_cli.py
+++ b/mergify_cli/tests/ci/scopes/test_cli.py
@@ -4,6 +4,7 @@
 import pytest
 import yaml
 
+from mergify_cli.ci.scopes import base_detector
 from mergify_cli.ci.scopes import cli
 
 
@@ -23,6 +24,7 @@ def test_from_yaml_valid(tmp_path: pathlib.Path) -> None:
 
     config = cli.Config.from_yaml(str(config_file))
     assert config.model_dump() == {
+        "merge_queue_scope": "merge-queue",
         "scopes": {
             "backend": {"include": ("api/**/*.py", "backend/**/*.py"), "exclude": ()},
             "frontend": {"include": ("ui/**/*.js", "ui/**/*.tsx"), "exclude": ()},
@@ -223,7 +225,7 @@ def test_detect_with_matches(
     config_file.write_text(yaml.dump(config_data))
 
     # Setup mocks
-    mock_detect_base.return_value = "main"
+    mock_detect_base.return_value = base_detector.Base("main", is_merge_queue=True)
     mock_git_changed.return_value = ["api/models.py", "other.txt"]
 
     # Capture output
@@ -240,6 +242,7 @@ def test_detect_with_matches(
     assert "Base: main" in calls
     assert "Scopes touched:" in calls
     assert "- backend" in calls
+    assert "- merge-queue" in calls
 
 
 @mock.patch("mergify_cli.ci.scopes.cli.base_detector.detect")
@@ -257,7 +260,7 @@ def test_detect_no_matches(
     config_file.write_text(yaml.dump(config_data))
 
     # Setup mocks
-    mock_detect_base.return_value = "main"
+    mock_detect_base.return_value = base_detector.Base("main", is_merge_queue=False)
     mock_git_changed.return_value = ["other.txt"]
 
     # Capture output
@@ -287,7 +290,7 @@ def test_detect_debug_output(
     config_file.write_text(yaml.dump(config_data))
 
     # Setup mocks
-    mock_detect_base.return_value = "main"
+    mock_detect_base.return_value = base_detector.Base("main", is_merge_queue=False)
     mock_git_changed.return_value = ["api/models.py", "api/views.py"]
 
     # Capture output