diff --git a/crates/xgen-adapter-filesystem/src/atomic_commit.rs b/crates/xgen-adapter-filesystem/src/atomic_commit.rs
index 2aad9b0..53c1f1d 100644
--- a/crates/xgen-adapter-filesystem/src/atomic_commit.rs
+++ b/crates/xgen-adapter-filesystem/src/atomic_commit.rs
@@ -146,7 +146,9 @@ fn open_parent(root: &Dir, path: &RelativePath) -> Result<(Dir, String), AtomicC
                 OpenErrorClass::Missing | OpenErrorClass::NotADirectory => {
                     AtomicCommitFailure::ParentNotFound
                 }
-                OpenErrorClass::Refused => AtomicCommitFailure::OpenParent,
+                OpenErrorClass::Directory | OpenErrorClass::Refused => {
+                    AtomicCommitFailure::OpenParent
+                }
             }
         })?;
         if is_windows_reparse_point(
diff --git a/crates/xgen-adapter-filesystem/src/path.rs b/crates/xgen-adapter-filesystem/src/path.rs
index 918bba8..51c7db4 100644
--- a/crates/xgen-adapter-filesystem/src/path.rs
+++ b/crates/xgen-adapter-filesystem/src/path.rs
@@ -73,6 +73,9 @@ pub(crate) enum OpenErrorClass {
     Missing,
     /// Something other than a directory exists at the name.
     NotADirectory,
+    /// A directory exists at the name. Some platforms refuse to open a directory as a file, so
+    /// this is how a file open learns that the name has the wrong kind.
+    Directory,
     /// The name exists but is refused, such as a symbolic link, or the error is not classified.
     Refused,
 }
@@ -85,15 +88,16 @@ pub(crate) fn classify_open_error(
     name: &str,
     error: &std::io::Error,
 ) -> OpenErrorClass {
-    match error.kind() {
-        std::io::ErrorKind::NotFound => OpenErrorClass::Missing,
-        std::io::ErrorKind::NotADirectory
-            if !parent
-                .symlink_metadata(name)
-                .is_ok_and(|metadata| metadata.file_type().is_symlink()) =>
-        {
-            OpenErrorClass::NotADirectory
-        }
+    if error.kind() == std::io::ErrorKind::NotFound {
+        return OpenErrorClass::Missing;
+    }
+    let file_type = parent
+        .symlink_metadata(name)
+        .map(|metadata| metadata.file_type());
+    match file_type {
+        Ok(file_type) if file_type.is_symlink() => OpenErrorClass::Refused,
+        _ if error.kind() == std::io::ErrorKind::NotADirectory => OpenErrorClass::NotADirectory,
+        Ok(file_type) if file_type.is_dir() => OpenErrorClass::Directory,
         _ => OpenErrorClass::Refused,
     }
 }
diff --git a/crates/xgen-adapter-filesystem/src/query.rs b/crates/xgen-adapter-filesystem/src/query.rs
index 72b9a52..65d1056 100644
--- a/crates/xgen-adapter-filesystem/src/query.rs
+++ b/crates/xgen-adapter-filesystem/src/query.rs
@@ -1009,7 +1009,7 @@ fn open_directory(root: &Dir, path: &RelativePath) -> Result<Dir, QueryFailure>
                 // means the requested path does not exist.
                 OpenErrorClass::NotADirectory if index == last => QueryFailure::NotADirectory,
                 OpenErrorClass::Missing | OpenErrorClass::NotADirectory => QueryFailure::NotFound,
-                OpenErrorClass::Refused => QueryFailure::Open,
+                OpenErrorClass::Directory | OpenErrorClass::Refused => QueryFailure::Open,
             }
         })?;
         if is_windows_reparse_point(&directory.dir_metadata().map_err(|_| QueryFailure::Open)?) {
@@ -1035,6 +1035,7 @@ fn open_regular_file(root: &Dir, path: &RelativePath) -> Result<File, QueryFailu
     let file = directory.open_with(leaf, &options).map_err(|error| {
         match classify_open_error(&directory, leaf, &error) {
             OpenErrorClass::Missing | OpenErrorClass::NotADirectory => QueryFailure::NotFound,
+            OpenErrorClass::Directory => QueryFailure::NotAFile,
             OpenErrorClass::Refused => QueryFailure::Open,
         }
     })?;
diff --git a/crates/xgen-adapter-filesystem/src/read_text.rs b/crates/xgen-adapter-filesystem/src/read_text.rs
index c065f6f..6d9321b 100644
--- a/crates/xgen-adapter-filesystem/src/read_text.rs
+++ b/crates/xgen-adapter-filesystem/src/read_text.rs
@@ -270,10 +270,12 @@ impl ReadFailure {
 }
 
 /// A missing component, or a parent component that is not a directory, means the path does not
-/// exist. Every other open error stays unclassified beyond "unavailable".
+/// exist, and a directory is not a file. Every other open error stays unclassified beyond
+/// "unavailable".
 fn open_failure(parent: &Dir, name: &str, error: &std::io::Error) -> ReadFailure {
     match classify_open_error(parent, name, error) {
         OpenErrorClass::Missing | OpenErrorClass::NotADirectory => ReadFailure::NotFound,
+        OpenErrorClass::Directory => ReadFailure::NonRegular,
         OpenErrorClass::Refused => ReadFailure::Open,
     }
 }