fix: hold the PR title only to rules a title can meet

main.py

@@ -502,6 +502,22 @@ def keep_ai_rules(scope: ScopeResult) -> ScopeResult:
     return skip_when_no_ai_rule_ran(scope)
 
 
+#: Rules about a commit rather than about a line of text: it has a body
+#: (CC011), a sign-off (CC012), an author that is no AI tool (CC017). A pull
+#: request title has neither body nor trailers nor an author of its own, so
+#: judged as a commit message it could never pass the first two, and the
+#: third would judge whatever git identity the runner has.
+COMMIT_ONLY_RULE_IDS = frozenset({"CC011", "CC012", "CC017"})
+
+
+def drop_commit_only_rules(scope: ScopeResult) -> ScopeResult:
+    """Narrow the PR title scope to the rules a one-line title can meet."""
+    scope.checks = [
+        c for c in scope.checks if c.get("rule_id") not in COMMIT_ONLY_RULE_IDS
+    ]
+    return scope
+
+
 def get_pr_title() -> str | None:
     """Read PR title from GitHub event payload."""
     if not is_pr_event():
@@ -972,7 +988,8 @@ def run_commit_check() -> tuple[int, list[ScopeResult]]:
     if PR_TITLE_ENABLED and is_pr_event():
         pr_title = get_pr_title()
         if pr_title:
-            results.append(check_scope("PR title", ["--message"], input_text=pr_title))
+            scope = check_scope("PR title", ["--message"], input_text=pr_title)
+            results.append(drop_commit_only_rules(scope))
 
     # ---- 2. PR description ------------------------------------------------
     if (PR_BODY_AI_ATTRIBUTION_ENABLED or ai_label_name()) and is_pr_event():

main_test.py

@@ -1004,6 +1004,33 @@ def test_pr_title_check_runs_when_enabled(self):
             "PR title", ["--message"], input_text="feat: a feature"
         )
 
+    def test_pr_title_is_not_held_to_commit_only_rules(self):
+        # require_body and require_signed_off_by judge a commit; a title has
+        # no body or trailers, so it could never pass them.
+        title = main.ScopeResult(
+            label="PR title",
+            checks=[
+                make_check("message", "pass", "CC001", value="feat: add login"),
+                make_check("require_body", "fail", "CC011", value="feat: add login"),
+                make_check("require_signed_off_by", "fail", "CC012"),
+                make_check("ai_author", "fail", "CC017", value="Claude <x@y.z>"),
+            ],
+        )
+        with (
+            patch("main.PR_TITLE_ENABLED", True),
+            patch("main.MESSAGE_ENABLED", False),
+            patch("main.BRANCH_ENABLED", False),
+            patch("main.AUTHOR_NAME_ENABLED", False),
+            patch("main.AUTHOR_EMAIL_ENABLED", False),
+            patch("main.is_pr_event", return_value=True),
+            patch("main.get_pr_title", return_value="feat: add login"),
+            patch("main.check_scope", return_value=title),
+            patch("main.run_other_checks", return_value=[]),
+        ):
+            rc, results = main.run_commit_check()
+        self.assertEqual(rc, 0)
+        self.assertEqual([c["rule_id"] for c in results[0].checks], ["CC001"])
+
     def test_pr_title_failure_propagates(self):
         with (
             patch("main.PR_TITLE_ENABLED", True),
@@ -4222,6 +4249,18 @@ def test_failing_message(self):
             main.render_report([scope]),
         )
 
+    def test_a_title_meets_only_the_rules_a_title_can(self):
+        with open(self.config, "w", encoding="utf-8") as f:
+            f.write("[commit]\nrequire_body = true\nrequire_signed_off_by = true\n")
+        rc, data = self._run("feat: add login page")
+        failed = {c["rule_id"] for c in data["checks"] if c["status"] == "fail"}
+        self.assertEqual(rc, 1)
+        self.assertEqual(failed, {"CC011", "CC012"})
+        scope = main.drop_commit_only_rules(
+            main.ScopeResult(label="PR title", checks=data["checks"])
+        )
+        self.assertEqual(scope.status, "pass")
+
 
 class TestStderrIsNotPartOfTheJson(unittest.TestCase):
     """stdout is the JSON; stderr is what the CLI has to say to a person.