diff --git a/.gitignore b/.gitignore
index 6cf5fb5f32d63e..7bf0420d87b744 100644
--- a/.gitignore
+++ b/.gitignore
@@ -278,3 +278,8 @@ lcov*.info
 /bundled_gems.json
 /default_gems.json
 /gems/default_gems
+
+# AI agents
+/.claude
+/AGENTS.md
+/CLAUDE.md
diff --git a/file.c b/file.c
index c23e92d22e029f..112d9b3e4d090c 100644
--- a/file.c
+++ b/file.c
@@ -5019,7 +5019,7 @@ rb_file_s_basename(int argc, VALUE *argv, VALUE _)
 {
     VALUE fname, fext;
     const char *name, *p;
-    long f, n;
+    long f = 0, n;
     rb_encoding *enc;
 
     fext = Qnil;