diff --git a/src/c.zig b/src/c.zig
index 5e74b804f34860..167b94b6ad4faf 100644
--- a/src/c.zig
+++ b/src/c.zig
@@ -157,10 +157,6 @@ pub fn moveFileZSlow(from_dir: bun.FileDescriptor, filename: [:0]const u8, to_di
 }
 
 pub fn copyFileZSlowWithHandle(in_handle: bun.FileDescriptor, to_dir: bun.FileDescriptor, destination: [:0]const u8) !void {
-    if (comptime Environment.isWindows) {
-        @panic("TODO windows");
-    }
-
     const stat_ = if (comptime Environment.isPosix) try std.os.fstat(in_handle.cast()) else void{};
 
     // Attempt to delete incase it already existed.
diff --git a/src/install/npm.zig b/src/install/npm.zig
index 8df30abf62f6c9..893465fa4866a8 100644
--- a/src/install/npm.zig
+++ b/src/install/npm.zig
@@ -657,13 +657,21 @@ pub const PackageManifest = struct {
             }
         }
 
-        fn writeFile(this: *const PackageManifest, tmp_path: [:0]const u8, tmpdir: std.fs.Dir) !void {
-            var tmpfile = try tmpdir.createFileZ(tmp_path, .{
-                .truncate = true,
-            });
-            defer tmpfile.close();
-            const writer = tmpfile.writer();
-            try Serializer.write(this, @TypeOf(writer), writer);
+        fn writeFile(
+            this: *const PackageManifest,
+            tmpdir: anytype,
+            tmp_path: [:0]const u8,
+            cache_dir: anytype,
+            out_path: [:0]const u8,
+        ) !void {
+            var tmpfile = try bun.sys.File.openat(tmpdir, tmp_path, std.os.O.CREAT | std.os.O.TRUNC | std.os.O.WRONLY, 0).unwrap();
+            {
+                errdefer tmpfile.close();
+                const writer = tmpfile.writer();
+                try Serializer.write(this, @TypeOf(writer), writer);
+            }
+
+            try tmpfile.closeAndMoveAt(tmpdir, tmp_path, cache_dir, out_path);
         }
 
         pub fn save(this: *const PackageManifest, tmpdir: std.fs.Dir, cache_dir: std.fs.Dir) !void {
@@ -678,9 +686,8 @@ pub const PackageManifest = struct {
             try dest_path_stream_writer.print("{any}.npm-{any}", .{ hex_fmt, hex_timestamp_fmt });
             try dest_path_stream_writer.writeByte(0);
             const tmp_path: [:0]u8 = dest_path_buf[0 .. dest_path_stream.pos - 1 :0];
-            try writeFile(this, tmp_path, tmpdir);
             const out_path = std.fmt.bufPrintZ(&out_path_buf, "{any}.npm", .{hex_fmt}) catch unreachable;
-            try std.os.renameatZ(tmpdir.fd, tmp_path, cache_dir.fd, out_path);
+            try writeFile(this, tmpdir, tmp_path, cache_dir, out_path);
         }
 
         pub fn load(allocator: std.mem.Allocator, cache_dir: std.fs.Dir, package_name: string) !?PackageManifest {
@@ -688,23 +695,11 @@ pub const PackageManifest = struct {
             var file_path_buf: [512 + 64]u8 = undefined;
             const hex_fmt = bun.fmt.hexIntLower(file_id);
             const file_path = try std.fmt.bufPrintZ(&file_path_buf, "{any}.npm", .{hex_fmt});
-            var cache_file = cache_dir.openFileZ(
-                file_path,
-                .{ .mode = .read_only },
-            ) catch return null;
             var timer: std.time.Timer = undefined;
             if (PackageManager.verbose_install) {
                 timer = std.time.Timer.start() catch @panic("timer fail");
             }
-            defer cache_file.close();
-            const bytes = try cache_file.readToEndAllocOptions(
-                allocator,
-                std.math.maxInt(u32),
-                cache_file.getEndPos() catch null,
-                @alignOf(u8),
-                null,
-            );
-
+            const bytes = bun.sys.File.readFrom(cache_dir, file_path, allocator).unwrap() catch return null;
             errdefer allocator.free(bytes);
             if (bytes.len < header_bytes.len) return null;
             const result = try readAll(bytes);
diff --git a/src/sys.zig b/src/sys.zig
index 270369fb97cc24..552eb5dec154a6 100644
--- a/src/sys.zig
+++ b/src/sys.zig
@@ -2632,11 +2632,15 @@ pub const File = struct {
     pub const ReadError = anyerror;
 
     pub fn closeAndMoveTo(this: File, src: [:0]const u8, dest: [:0]const u8) !void {
+        return closeAndMoveAt(this, std.fs.cwd(), src, std.fs.cwd(), dest);
+    }
+
+    pub fn closeAndMoveAt(this: File, src_dir: anytype, src: [:0]const u8, dest_dir: anytype, dest: [:0]const u8) !void {
         // On POSIX, close the file after moving it.
         defer if (Environment.isPosix) this.close();
         // On Windows, close the file before moving it.
         if (Environment.isWindows) this.close();
-        try bun.C.moveFileZWithHandle(this.handle, bun.toFD(std.fs.cwd()), src, bun.toFD(std.fs.cwd()), dest);
+        try bun.C.moveFileZWithHandle(this.handle, bun.toFD(src_dir), src, bun.toFD(dest_dir), dest);
     }
 
     fn stdIoRead(this: File, buf: []u8) ReadError!usize {