diff --git a/Cargo.lock b/Cargo.lock
index f8b0d2e48..3366f953f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1145,7 +1145,6 @@ name = "cpio-archive"
 version = "0.10.0"
 dependencies = [
  "chrono",
- "is_executable",
  "simple-file-manifest",
  "thiserror 2.0.18",
 ]
@@ -2359,15 +2358,6 @@ dependencies = [
  "serde",
 ]
 
-[[package]]
-name = "is_executable"
-version = "1.0.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "baabb8b4867b26294d818bf3f651a454b6901431711abb96e296245888d6e8c4"
-dependencies = [
- "windows-sys 0.60.2",
-]
-
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.2"
diff --git a/cpio-archive/Cargo.toml b/cpio-archive/Cargo.toml
index 272497b36..165fcfee6 100644
--- a/cpio-archive/Cargo.toml
+++ b/cpio-archive/Cargo.toml
@@ -13,6 +13,5 @@ readme = "README.md"
 
 [dependencies]
 chrono = "0.4.43"
-is_executable = "1.0.5"
 simple-file-manifest = "0.11.0"
 thiserror = "2.0.18"
diff --git a/cpio-archive/src/odc.rs b/cpio-archive/src/odc.rs
index 486a44c06..629f90779 100644
--- a/cpio-archive/src/odc.rs
+++ b/cpio-archive/src/odc.rs
@@ -11,13 +11,13 @@
 use {
     crate::{CpioHeader, CpioReader, CpioResult, Error},
     chrono::{DateTime, Utc},
-    is_executable::IsExecutable,
     simple_file_manifest::{
         FileManifest, S_IFDIR, S_IRGRP, S_IROTH, S_IRUSR, S_IWUSR, S_IXGRP, S_IXOTH, S_IXUSR,
     },
     std::{
         collections::HashSet,
         ffi::CStr,
+        fs,
         io::{Read, Take, Write},
         path::Path,
     },
@@ -70,6 +70,33 @@ fn write_octal(value: u64, writer: &mut impl Write, size: usize) -> CpioResult<(
     Ok(())
 }
 
+/// permissions_to_u32 converts fs::Permissions objects to chmod integers.
+pub fn permissions_to_u32(permissions: fs::Permissions) -> u32 {
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        permissions.mode()
+    }
+    #[cfg(windows)]
+    {
+        if permissions.readonly() {
+            0o444u32
+        } else {
+            0o666u32
+        }
+    }
+}
+
+/// GENERIC_DIRECTORY_MODE applies to auto generated directories.
+const GENERIC_DIRECTORY_MODE: u32 = S_IFDIR
+    | S_IRUSR
+    | S_IWUSR
+    | S_IXUSR
+    | S_IRGRP
+    | S_IXGRP
+    | S_IROTH
+    | S_IXOTH;
+
 /// Parsed portable ASCII format header.
 #[derive(Clone, Debug)]
 pub struct OdcHeader {
@@ -297,8 +324,8 @@ pub struct OdcBuilder<W: Write + Sized> {
     default_uid: u32,
     default_gid: u32,
     default_mtime: DateTime<Utc>,
-    default_mode_file: u32,
-    default_mode_dir: u32,
+    default_mode_file: Option<u32>,
+    default_mode_dir: Option<u32>,
     auto_write_dirs: bool,
     seen_dirs: HashSet<String>,
     entry_count: u32,
@@ -313,15 +340,8 @@ impl<W: Write + Sized> OdcBuilder<W> {
             default_uid: 0,
             default_gid: 0,
             default_mtime: Utc::now(),
-            default_mode_file: S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH,
-            default_mode_dir: S_IFDIR
-                | S_IRUSR
-                | S_IWUSR
-                | S_IXUSR
-                | S_IRGRP
-                | S_IXGRP
-                | S_IROTH
-                | S_IXOTH,
+            default_mode_file: None,
+            default_mode_dir: None,
             auto_write_dirs: true,
             seen_dirs: HashSet::new(),
             entry_count: 0,
@@ -330,12 +350,12 @@ impl<W: Write + Sized> OdcBuilder<W> {
     }
 
     /// Set the default file mode to use for files.
-    pub fn default_mode_file(&mut self, mode: u32) {
+    pub fn default_mode_file(&mut self, mode: Option<u32>) {
         self.default_mode_file = mode;
     }
 
     /// Set the default file mode to use for directories.
-    pub fn default_mode_directory(&mut self, mode: u32) {
+    pub fn default_mode_directory(&mut self, mode: Option<u32>) {
         self.default_mode_dir = mode;
     }
 
@@ -372,7 +392,7 @@ impl<W: Write + Sized> OdcBuilder<W> {
         OdcHeader {
             dev: 0,
             inode,
-            mode: self.default_mode_file,
+            mode: 0u32,
             uid: self.default_uid,
             gid: self.default_gid,
             nlink: 0,
@@ -407,7 +427,7 @@ impl<W: Write + Sized> OdcBuilder<W> {
 
             if !self.seen_dirs.contains(&dir) {
                 let mut header = self.next_header();
-                header.mode = self.default_mode_dir;
+                header.mode = self.default_mode_file.unwrap_or(GENERIC_DIRECTORY_MODE);
                 header.name = dir.clone();
 
                 bytes_written += header.write(&mut self.writer)?;
@@ -418,6 +438,18 @@ impl<W: Write + Sized> OdcBuilder<W> {
         Ok(bytes_written)
     }
 
+    /// Append a raw header, such as for a directory.
+    ///
+    /// The writer is written as-is.
+    ///
+    /// Automatic directory emission is not processed in this mode.
+    pub fn append_header(
+        &mut self,
+        header: OdcHeader,
+    ) -> CpioResult<u64> {
+        header.write(&mut self.writer)
+    }
+
     /// Append a raw header and corresponding file data to the writer.
     ///
     /// The writer and data are written as-is.
@@ -516,10 +548,7 @@ impl<W: Write + Sized> OdcBuilder<W> {
         let mut header = self.next_header();
         header.name = archive_path;
         header.file_size = metadata.len();
-
-        if path.is_executable() {
-            header.mode |= S_IXUSR | S_IXGRP | S_IXOTH;
-        }
+        header.mode = self.default_mode_file.unwrap_or(permissions_to_u32(metadata.permissions()));
 
         bytes_written += header.write(&mut self.writer)?;
         bytes_written += std::io::copy(&mut fh, &mut self.writer)?;
@@ -532,7 +561,19 @@ impl<W: Write + Sized> OdcBuilder<W> {
         let mut bytes_written = 0;
 
         for (path, entry) in manifest.iter_entries() {
-            let mode = if entry.is_executable() { 0o755 } else { 0o644 };
+            let metadata = path.metadata()?;
+            let mut mode = permissions_to_u32(metadata.permissions());
+
+            if metadata.is_file() {
+                if let Some(m) = self.default_mode_file {
+                    mode = m;
+                }
+            } else if metadata.is_dir() {
+                if let Some(m) = self.default_mode_dir {
+                    mode = m;
+                }
+            }
+
             let data = entry.resolve_content()?;
 
             bytes_written += self.append_file_from_data(path.display().to_string(), data, mode)?;