diff --git a/sync_ai_rules/core/generator_interface.py b/sync_ai_rules/core/generator_interface.py
index 49501c2..bc8e314 100644
--- a/sync_ai_rules/core/generator_interface.py
+++ b/sync_ai_rules/core/generator_interface.py
@@ -32,9 +32,7 @@ def is_multi_file(self) -> bool:
         """Whether this generator creates files directly via generate_files()."""
         return False
 
-    def generate_files(
-        self, rules: Dict[str, List[RuleMetadata]], project_root: str
-    ) -> None:
+    def generate_files(self, rules: Dict[str, List[RuleMetadata]], project_root: str) -> None:
         """Generate multiple files directly. Only called when is_multi_file is True."""
         raise NotImplementedError(
             f"{type(self).__name__} sets is_multi_file=True but does not implement generate_files()"
diff --git a/sync_ai_rules/generators/skills_generator.py b/sync_ai_rules/generators/skills_generator.py
index a7dc077..8d2c7c2 100644
--- a/sync_ai_rules/generators/skills_generator.py
+++ b/sync_ai_rules/generators/skills_generator.py
@@ -40,9 +40,7 @@ def generate(self, rules: Dict[str, List[RuleMetadata]], config: Dict[str, Any])
     def is_multi_file(self) -> bool:
         return True
 
-    def generate_files(
-        self, rules: Dict[str, List[RuleMetadata]], project_root: str
-    ) -> None:
+    def generate_files(self, rules: Dict[str, List[RuleMetadata]], project_root: str) -> None:
         """Generate skill files as direct children of .claude/skills/."""
         skills_root = os.path.join(project_root, _SKILLS_DIR)
 
@@ -74,19 +72,31 @@ def generate_files(
                     logger.warning("Failed to write skill %s: %s", skill_name, e)
                     print(f"  ✗ Failed to create skill: {skill_name}")
 
+        _write_gitattributes(skills_root)
+
     def get_section_markers(self) -> tuple[str, str]:
         return ("", "")
 
 
+def _write_gitattributes(skills_root: str) -> None:
+    """Write .gitattributes to hide generated skills from GitHub PR diffs."""
+    path = os.path.join(skills_root, ".gitattributes")
+    with open(path, "w", encoding="utf-8") as f:
+        f.write(
+            "# Auto-generated by sync-ai-rules hook. Do not edit.\n"
+            "generated_*/SKILL.md linguist-generated\n"
+        )
+
+
 def _strip_source_prefix(relative_path: str) -> str:
     """Strip the .cursor/rules/ prefix from a rule's relative path."""
     prefix = _SOURCE_DIR + os.sep
     if relative_path.startswith(prefix):
-        return relative_path[len(prefix):]
+        return relative_path[len(prefix) :]
     # Also handle forward-slash separators
     prefix_fwd = _SOURCE_DIR + "/"
     if relative_path.startswith(prefix_fwd):
-        return relative_path[len(prefix_fwd):]
+        return relative_path[len(prefix_fwd) :]
     return relative_path
 
 
diff --git a/test/after/.claude/skills/.gitattributes b/test/after/.claude/skills/.gitattributes
new file mode 100644
index 0000000..cf85641
--- /dev/null
+++ b/test/after/.claude/skills/.gitattributes
@@ -0,0 +1,2 @@
+# Auto-generated by sync-ai-rules hook. Do not edit.
+generated_*/SKILL.md linguist-generated