diff --git a/.github/scripts/check_plugin_api.py b/.github/scripts/check_plugin_api.py
index 962fbd91..c66d524c 100644
--- a/.github/scripts/check_plugin_api.py
+++ b/.github/scripts/check_plugin_api.py
@@ -419,8 +419,10 @@ def caller_breaks(path: str, old: griffe.Object, new: griffe.Object, reshaped: s
         else:
             found += [f"{path}.{name}: no longer in __all__"
                       for name in sorted(set(before or ()) - set(after or ())) if name in new.members]
-    for breakage in griffe.find_breaking_changes(old, new):
-        if _benign(breakage, old, new) or breakage.obj.path in reshaped:
+    scope = (old.parent, new.parent) if old.is_function else (old, new)
+    for breakage in griffe.find_breaking_changes(*scope):
+        if (old.is_function and breakage.obj.path != old.path) or _benign(breakage, old, new) \
+                or breakage.obj.path in reshaped:
             continue
         found.append(_describe(breakage, public))
     return found
diff --git a/tst/unit/test_check_plugin_api.py b/tst/unit/test_check_plugin_api.py
index 84fc4c5b..e0aad0e7 100644
--- a/tst/unit/test_check_plugin_api.py
+++ b/tst/unit/test_check_plugin_api.py
@@ -116,6 +116,14 @@ def settings(package, config=None):
     "internal.py": '''
 def compute(x):
     return x
+''',
+    "runner/store.py": '''
+def count_runs(task_id=None):
+    return 0
+
+
+def prune_runs(days=30):
+    return 0
 ''',
 }
 
@@ -188,11 +196,13 @@ def _check(tmp_path: Path, edits: list[tuple[str, str, str]], title: str | None
      "agent_env.plugins.ENVS: Attribute value was changed"),
     ([(ARTIFACT, "Field(default=0,", "Field(default=1,")],
      "agent_env.artifact.artifact.Artifact.version: Attribute value was changed"),
+    ([("runner/store.py", "def count_runs(task_id=None):", "def count_runs(task_id):")],
+     "agent_env.runner.store.count_runs(task_id): Parameter is now required"),
 ], ids=["method-removed", "parameter-renamed", "required-parameter-added", "default-changed", "class-attribute-changed",
         "base-removed", "abstract-method-added", "method-became-abstract", "method-became-required",
         "hook-parameter-added", "async-to-sync", "classmethod-to-staticmethod", "required-private-method-changed",
         "dataclass-field-removed", "dropped-from-all", "export-removed", "settings-signature-changed",
-        "group-name-changed", "field-default-changed"])
+        "group-name-changed", "field-default-changed", "used-function-signature-changed"])
 def test_reports_a_break(tmp_path, edits, reported):
     result = _check(tmp_path, edits)
 
@@ -213,9 +223,10 @@ def test_reports_a_break(tmp_path, edits, reported):
     [(CONTEXT, "    agent_model: str | None = None\n",
       "    agent_harness: str | None = None\n    agent_model: str | None = None\n")],
     [(ARTIFACT, 'Field(description="Unique id")', 'Field(description="The artifact\'s id")')],
+    [("runner/store.py", "def prune_runs(days=30):", "def prune_runs(days):")],
 ], ids=["docstring", "new-optional-method", "private-rename", "internal-module", "parameter-swallowed-by-kwargs",
         "annotation-gains-a-value", "instance-attribute-expression", "default-to-equal-literal",
-        "dataclass-field-inserted", "field-description"])
+        "dataclass-field-inserted", "field-description", "unused-sibling-of-a-used-function"])
 def test_passes_a_compatible_change(tmp_path, edits):
     result = _check(tmp_path, edits)