diff --git a/src/user/user_objects.cc b/src/user/user_objects.cc
index 66619b05..df3980a0 100644
--- a/src/user/user_objects.cc
+++ b/src/user/user_objects.cc
@@ -33,7 +33,6 @@
 #include <vector>
 
 #include "lodepng.h"
-#include <mujoco/mjmacro.h>
 #include <mujoco/mjmodel.h>
 #include <mujoco/mjplugin.h>
 #include <mujoco/mjtnum.h>
@@ -45,7 +44,6 @@
 #include "user/user_model.h"
 #include "user/user_resource.h"
 #include "user/user_util.h"
-#include "user/user_vfs.h"
 
 namespace {
 namespace mju = ::mujoco::util;
@@ -704,18 +702,14 @@ void mjCBase::NameSpace(const mjCModel* m) {
 
 // load resource if found (fallback to OS filesystem)
 mjResource* mjCBase::LoadResource(std::string filename, const mjVFS* vfs) {
-  // try reading from provided VFS
-  mjResource* r = mju_openVfsResource(filename.c_str(), vfs);
-
-  if (!r) {
-    std::array<char, 1024> error;
-    // not in vfs try a provider or fallback to OS filesystem
-    r = mju_openResource(filename.c_str(), error.data(), error.size());
-    if (!r) {
-      throw mjCError(nullptr, "%s", error.data());
-    }
+  // try reading from provided VFS or fallback to OS filesystem
+  std::array<char, 1024> error;
+  mjResource* resource = mju_openResource(filename.c_str(), vfs,
+                                          error.data(), error.size());
+  if (!resource) {
+    throw mjCError(nullptr, "%s", error.data());
   }
-  return r;
+  return resource;
 }
 
 
diff --git a/src/user/user_resource.cc b/src/user/user_resource.cc
index ebe21238..805a3156 100644
--- a/src/user/user_resource.cc
+++ b/src/user/user_resource.cc
@@ -18,7 +18,6 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 
-#include <climits>
 #include <cstddef>
 #include <cstdint>
 #include <cstdio>
@@ -35,12 +34,16 @@
 #endif
 
 #include <mujoco/mjplugin.h>
+#include <mujoco/mujoco.h>
 #include "engine/engine_plugin.h"
-#include "engine/engine_util_errmem.h"
 #include "engine/engine_util_misc.h"
+#include "user/user_util.h"
+#include "user/user_vfs.h"
 
 namespace {
 
+using mujoco::user::FileToMemory;
+
 // file buffer used internally for the OS filesystem
 struct FileSpec {
   bool is_read;                 // set to nonzero if buffer was read into
@@ -48,11 +51,74 @@ struct FileSpec {
   time_t mtime;                 // last modified time
 };
 
+// callback for opening a resource, returns zero on failure
+int FileOpen(mjResource* resource, char* error, size_t nerror) {
+  resource->provider = nullptr;
+  resource->data = new FileSpec;
+  const char* name = resource->name;
+  FileSpec* spec = (FileSpec*) resource->data;
+  spec->is_read = false;
+  struct stat file_stat;
+  if (stat(name, &file_stat) == 0) {
+    memcpy(&spec->mtime, &file_stat.st_mtime, sizeof(time_t));
+  } else {
+    if (error) {
+      snprintf(error, nerror, "Error opening file '%s': %s", name,
+               strerror(errno));
+    }
+    return 0;
+  }
+  mju_encodeBase64(resource->timestamp, (uint8_t*) &spec->mtime,
+                   sizeof(time_t));
+  return 1;
+}
+
+// OS filesystem read callback
+int FileRead(mjResource* resource, const void** buffer) {
+  FileSpec* spec = (FileSpec*) resource->data;
+
+  // only read once from file
+  if (!spec->is_read) {
+    spec->buffer = FileToMemory(resource->name);
+    spec->is_read = true;
+  }
+  *buffer = spec->buffer.data();
+  return spec->buffer.size();
+}
+
+// OS filesystem close callback
+void FileClose(mjResource* resource) {
+  FileSpec* spec = (FileSpec*) resource->data;
+  if (spec) delete spec;
+}
+
+// OS filesystem getdir callback
+void FileGetDir(mjResource* resource, const char** dir, int* ndir) {
+  *dir = resource->name;
+  *ndir = mjuu_dirnamelen(resource->name);
+}
+
+// OS filesystem modified callback
+int FileModified(const mjResource* resource, const char*timestamp) {
+  if (mju_isValidBase64(timestamp) != sizeof(time_t)) {
+    return 1;  // error (assume modified)
+  }
+
+  time_t time1, time2;
+  mju_decodeBase64((uint8_t*) &time1, timestamp);
+  time2 = ((FileSpec*) resource->data)->mtime;
+  double diff = difftime(time2, time1);
+  if (diff < 0) return -1;
+  if (diff > 0) return  1;
+  return 0;
+}
+
 }  // namespace
 
 // open the given resource; if the name doesn't have a prefix matching with a
 // resource provider, then the OS filesystem is used
-mjResource* mju_openResource(const char* name, char* error, size_t nerror) {
+mjResource* mju_openResource(const char* name, const mjVFS* vfs,
+                             char* error, size_t nerror) {
   // no error so far
   if (error) {
     error[0] = '\0';
@@ -60,7 +126,10 @@ mjResource* mju_openResource(const char* name, char* error, size_t nerror) {
 
   mjResource* resource = (mjResource*) mju_malloc(sizeof(mjResource));
   if (resource == nullptr) {
-    mjERROR("could not allocate memory");
+    if (error) {
+      strncpy(error, "could not allocate memory", nerror);
+      error[nerror - 1] = '\0';
+    }
     return nullptr;
   }
 
@@ -70,16 +139,30 @@ mjResource* mju_openResource(const char* name, char* error, size_t nerror) {
   // copy name
   resource->name = (char*) mju_malloc(sizeof(char) * (strlen(name) + 1));
   if (resource->name == nullptr) {
+    if (error) {
+      strncpy(error, "could not allocate memory", nerror);
+      error[nerror - 1] = '\0';
+    }
     mju_closeResource(resource);
-    mjERROR("could not allocate memory");
     return nullptr;
   }
   memcpy(resource->name, name, sizeof(char) * (strlen(name) + 1));
 
+  // first priority is to check the VFS
+  if (vfs != nullptr) {
+    const mjpResourceProvider* provider = GetVfsResourceProvider();
+    resource->data = (void*) vfs;
+    resource->provider = provider;
+    if (provider->open(resource)) {
+      return resource;
+    }
+  }
+
   // find provider based off prefix of name
   const mjpResourceProvider* provider = mjp_getResourceProvider(name);
   if (provider != nullptr) {
     resource->provider = provider;
+    resource->data = nullptr;
     if (provider->open(resource)) {
       return resource;
     }
@@ -95,24 +178,11 @@ mjResource* mju_openResource(const char* name, char* error, size_t nerror) {
   }
 
   // lastly fallback to OS filesystem
-  resource->provider = nullptr;
-  resource->data = new FileSpec;
-  FileSpec* spec = (FileSpec*) resource->data;
-  spec->is_read = false;
-  struct stat file_stat;
-  if (stat(name, &file_stat) == 0) {
-    memcpy(&spec->mtime, &file_stat.st_mtime, sizeof(time_t));
-  } else {
-    if (error) {
-      snprintf(error, nerror, "Error opening file '%s': %s", name,
-               strerror(errno));
-    }
-    mju_closeResource(resource);
-    return nullptr;
+  if (FileOpen(resource, error, nerror)) {
+    return resource;
   }
-  mju_encodeBase64(resource->timestamp, (uint8_t*) &spec->mtime,
-                   sizeof(time_t));
-  return resource;
+  mju_closeResource(resource);
+  return nullptr;
 }
 
 
@@ -124,14 +194,11 @@ void mju_closeResource(mjResource* resource) {
   }
 
   // use the resource provider close callback
-  if (resource->provider && resource->provider->close) {
-    resource->provider->close(resource);
+  const mjpResourceProvider* provider = resource->provider;
+  if (provider) {
+    if (provider->close) provider->close(resource);
   } else {
-    // clear OS filesystem if present
-    FileSpec* spec = (FileSpec*) resource->data;
-    if (spec) {
-      delete spec;
-    }
+     FileClose(resource);  // clear OS filesystem if present
   }
 
   // free resource
@@ -149,36 +216,26 @@ int mju_readResource(mjResource* resource, const void** buffer) {
   }
 
   // if provider is NULL, then OS filesystem is used
-  FileSpec* spec = (FileSpec*) resource->data;
-
-  // only read once from file
-  if (!spec->is_read) {
-    spec->buffer = mju_fileToMemory(resource->name);
-    spec->is_read = true;
-  }
-  *buffer = spec->buffer.data();
-  return spec->buffer.size();
+  return FileRead(resource, buffer);
 }
 
 
 
 // get directory path of resource
 void mju_getResourceDir(mjResource* resource, const char** dir, int* ndir) {
-  *dir = NULL;
+  *dir = nullptr;
   *ndir = 0;
 
-  if (resource == NULL) {
+  if (resource == nullptr) {
     return;
   }
 
-  // provider is not OS filesystem
-  if (resource->provider) {
-    if (resource->provider->getdir) {
-      resource->provider->getdir(resource, dir, ndir);
-    }
+  const mjpResourceProvider* provider = resource->provider;
+  if (provider) {
+    if (provider->getdir) provider->getdir(resource, dir, ndir);
   } else {
-    *dir = resource->name;
-    *ndir = mju_dirnamelen(resource->name);
+    // fallback to OS filesystem
+    FileGetDir(resource, dir, ndir);
   }
 }
 
@@ -197,89 +254,5 @@ int mju_isModifiedResource(const mjResource* resource, const char* timestamp) {
   }
 
   // fallback to OS filesystem
-  if (mju_isValidBase64(timestamp) != sizeof(time_t)) {
-    return 1;  // error (assume modified)
-  }
-
-  time_t time1, time2;
-  mju_decodeBase64((uint8_t*) &time1, timestamp);
-  time2 = ((FileSpec*) resource->data)->mtime;
-  double diff = difftime(time2, time1);
-  if (diff < 0) return -1;
-  if (diff > 0) return  1;
-  return 0;
-}
-
-
-
-// get the length of the dirname portion of a given path
-int mju_dirnamelen(const char* path) {
-  if (!path) {
-    return 0;
-  }
-
-  int pos = -1;
-  for (int i = 0; path[i]; ++i) {
-    if (path[i] == '/' || path[i] == '\\') {
-      pos = i;
-    }
-  }
-
-  return pos + 1;
-}
-
-
-
-// read file into memory buffer (allocated here with mju_malloc)
-std::vector<uint8_t> mju_fileToMemory(const char* filename) {
-  FILE* fp = fopen(filename, "rb");
-  if (!fp) {
-    return {};
-  }
-
-  // find size
-  if (fseek(fp, 0, SEEK_END) != 0) {
-    fclose(fp);
-    mju_warning("Failed to calculate size for '%s'", filename);
-    return {};
-  }
-
-  // ensure file size fits in int
-  long long_filesize = ftell(fp);  // NOLINT(runtime/int)
-  if (long_filesize > INT_MAX) {
-    fclose(fp);
-    mju_warning("File size over 2GB is not supported. File: '%s'", filename);
-    return {};
-  } else if (long_filesize < 0) {
-    fclose(fp);
-    mju_warning("Failed to calculate size for '%s'", filename);
-    return {};
-  }
-
-  std::vector<uint8_t> buffer(long_filesize);
-
-  // go back to start of file
-  if (fseek(fp, 0, SEEK_SET) != 0) {
-    fclose(fp);
-    mju_warning("Read error while reading '%s'", filename);
-    return {};
-  }
-
-  // allocate and read
-  std::size_t bytes_read = fread(buffer.data(), 1, buffer.size(), fp);
-
-  // check that read data matches file size
-  if (bytes_read != buffer.size()) {  // SHOULD NOT OCCUR
-    if (ferror(fp)) {
-      fclose(fp);
-      mju_warning("Read error while reading '%s'", filename);
-      return {};
-    } else if (feof(fp)) {
-      buffer.resize(bytes_read);
-    }
-  }
-
-  // close file, return contents
-  fclose(fp);
-  return buffer;
+  return FileModified(resource, timestamp);
 }
diff --git a/src/user/user_resource.h b/src/user/user_resource.h
index 3a564091..e64874cb 100644
--- a/src/user/user_resource.h
+++ b/src/user/user_resource.h
@@ -30,7 +30,8 @@ extern "C" {
 
 // open the given resource; if the name doesn't have a prefix matching with a
 // resource provider, then the OS filesystem is used
-MJAPI mjResource* mju_openResource(const char* name, char* error, std::size_t nerror);
+MJAPI mjResource* mju_openResource(const char* name, const mjVFS* vfs,
+                                   char* error, std::size_t nerror);
 
 // close the given resource; no-op if resource is NULL
 MJAPI void mju_closeResource(mjResource* resource);
@@ -47,14 +48,8 @@ MJAPI void mju_getResourceDir(mjResource* resource, const char** dir, int* ndir)
 // return < 0 if the resource is older than the given timestamp
 MJAPI int mju_isModifiedResource(const mjResource* resource, const char* timestamp);
 
-// get the length of the dirname portion of a given path
-MJAPI int mju_dirnamelen(const char* path);
-
 #ifdef __cplusplus
 }
 #endif
 
-// read file into memory buffer (allocated here with mju_malloc)
-std::vector<uint8_t> mju_fileToMemory(const char* filename);
-
 #endif  // MUJOCO_SRC_ENGINE_ENGINE_RESOURCE_H_
diff --git a/src/user/user_util.cc b/src/user/user_util.cc
index 6305bca5..92ce36c4 100644
--- a/src/user/user_util.cc
+++ b/src/user/user_util.cc
@@ -16,8 +16,10 @@
 
 #include <algorithm>
 #include <cctype>
+#include <climits>
 #include <cmath>
 #include <cstddef>
+#include <cstdint>
 #include <cstdio>
 #include <cstring>
 #include <optional>
@@ -941,6 +943,22 @@ std::string mjuu_extToContentType(std::string_view filename) {
   }
 }
 
+// get the length of the dirname portion of a given path
+int mjuu_dirnamelen(const char* path) {
+  if (!path) {
+    return 0;
+  }
+
+  int pos = -1;
+  for (int i = 0; path[i]; ++i) {
+    if (path[i] == '/' || path[i] == '\\') {
+      pos = i;
+    }
+  }
+
+  return pos + 1;
+}
+
 namespace mujoco::user {
 
 std::string FilePath::Combine(const std::string& s1, const std::string& s2) {
@@ -1012,7 +1030,6 @@ FilePath FilePath::StripExt() const {
   return FilePathFast(path_.substr(0, n));
 }
 
-
 // is directory absolute path
 std::string FilePath::AbsPrefix(const std::string& str) {
   // empty: not absolute
@@ -1066,5 +1083,59 @@ std::string FilePath::StrLower() const {
   return str;
 }
 
+// read file into memory buffer
+std::vector<uint8_t> FileToMemory(const char* filename) {
+  FILE* fp = fopen(filename, "rb");
+  if (!fp) {
+    return {};
+  }
+
+  // find size
+  if (fseek(fp, 0, SEEK_END) != 0) {
+    fclose(fp);
+    mju_warning("Failed to calculate size for '%s'", filename);
+    return {};
+  }
+
+  // ensure file size fits in int
+  long long_filesize = ftell(fp);  // NOLINT(runtime/int)
+  if (long_filesize > INT_MAX) {
+    fclose(fp);
+    mju_warning("File size over 2GB is not supported. File: '%s'", filename);
+    return {};
+  } else if (long_filesize < 0) {
+    fclose(fp);
+    mju_warning("Failed to calculate size for '%s'", filename);
+    return {};
+  }
+
+  std::vector<uint8_t> buffer(long_filesize);
+
+  // go back to start of file
+  if (fseek(fp, 0, SEEK_SET) != 0) {
+    fclose(fp);
+    mju_warning("Read error while reading '%s'", filename);
+    return {};
+  }
+
+  // allocate and read
+  std::size_t bytes_read = fread(buffer.data(), 1, buffer.size(), fp);
+
+  // check that read data matches file size
+  if (bytes_read != buffer.size()) {  // SHOULD NOT OCCUR
+    if (ferror(fp)) {
+      fclose(fp);
+      mju_warning("Read error while reading '%s'", filename);
+      return {};
+    } else if (feof(fp)) {
+      buffer.resize(bytes_read);
+    }
+  }
+
+  // close file, return contents
+  fclose(fp);
+  return buffer;
+}
+
 }  // namespace mujoco::user
 
diff --git a/src/user/user_util.h b/src/user/user_util.h
index 336ee4bb..1bce5010 100644
--- a/src/user/user_util.h
+++ b/src/user/user_util.h
@@ -16,9 +16,11 @@
 #define MUJOCO_SRC_USER_USER_UTIL_H_
 
 #include <cstddef>
+#include <cstdint>
 #include <optional>
 #include <string>
 #include <string_view>
+#include <vector>
 
 const double mjEPS = 1E-14;     // minimum value in various calculations
 const double mjMINMASS = 1E-6;  // minimum mass allowed
@@ -230,6 +232,9 @@ class FilePath {
   std::string path_;
 };
 
+// read file into memory buffer
+std::vector<uint8_t> FileToMemory(const char* filename);
+
 }  // namespace mujoco::user
 
 // strip path from filename
@@ -258,4 +263,7 @@ std::optional<std::string_view> mjuu_parseContentTypeAttrSubtype(std::string_vie
 // convert filename extension to content type; return empty string if not found
 std::string mjuu_extToContentType(std::string_view filename);
 
+// get the length of the dirname portion of a given path
+int mjuu_dirnamelen(const char* path);
+
 #endif  // MUJOCO_SRC_USER_USER_UTIL_H_
diff --git a/src/user/user_vfs.cc b/src/user/user_vfs.cc
index 88b6c87d..8bc484a2 100644
--- a/src/user/user_vfs.cc
+++ b/src/user/user_vfs.cc
@@ -17,19 +17,20 @@
 #include <cstddef>
 #include <cstring>
 #include <cstdint>
+#include <cstdio>
+#include <cstdlib>
 #include <string>
 #include <unordered_map>
 #include <utility>
 #include <vector>
 
-#include "engine/engine_util_errmem.h"
 #include "engine/engine_util_misc.h"
-#include "user/user_resource.h"
 #include "user/user_util.h"
 
 namespace {
 
 using mujoco::user::FilePath;
+using mujoco::user::FileToMemory;
 
 // internal struct for VFS files
 struct VFSFile {
@@ -177,7 +178,7 @@ void Close(mjResource* resource) {
 // getdir callback for the VFS resource provider
 void GetDir(mjResource* resource, const char** dir, int* ndir) {
   *dir = (resource) ? resource->name : nullptr;
-  *ndir = (resource) ? mju_dirnamelen(resource->name) : 0;
+  *ndir = (resource) ? mjuu_dirnamelen(resource->name) : 0;
 }
 
 // modified callback for the VFS resource provider
@@ -227,7 +228,7 @@ int mj_addFileVFS(mjVFS* vfs, const char* directory, const char* filename) {
   }
 
   // allocate and read
-  std::vector<uint8_t> buffer = mju_fileToMemory(fullname.c_str());
+  std::vector<uint8_t> buffer = FileToMemory(fullname.c_str());
   if (buffer.empty()) {
     return -1;
   }
@@ -265,44 +266,8 @@ void mj_deleteVFS(mjVFS* vfs) {
   }
 }
 
-// open VFS resource
-mjResource* mju_openVfsResource(const char* name, const mjVFS* vfs) {
-  if (vfs == nullptr) {
-    return nullptr;
-  }
-
-  // VFS provider
-  static struct mjpResourceProvider provider = { nullptr, &Open, &Read, &Close,
-                                                &GetDir, &Modified, nullptr };
-
-  // create resource
-  mjResource* resource = (mjResource*) mju_malloc(sizeof(mjResource));
-  if (resource == nullptr) {
-    mjERROR("could not allocate memory");
-    return nullptr;
-  }
-
-  // clear out resource
-  memset(resource, 0, sizeof(mjResource));
-
-  // copy name
-  std::size_t n = std::strlen(name);
-  resource->name = (char*) mju_malloc(sizeof(char) * (n + 1));
-  if (resource->name == nullptr) {
-    mju_closeResource(resource);
-    mjERROR("could not allocate memory");
-    return nullptr;
-  }
-  std::memcpy(resource->name, name, sizeof(char) * (n + 1));
-  resource->data = (void*) vfs;
-
-  // open resource
-  resource->provider = &provider;
-  if (provider.open(resource)) {
-    return resource;
-  }
-
-  // not found in VFS
-  mju_closeResource(resource);
-  return nullptr;
+const mjpResourceProvider* GetVfsResourceProvider() {
+  static mjpResourceProvider provider
+      = { nullptr, &Open, &Read, &Close, &GetDir, &Modified, nullptr };
+  return &provider;
 }
diff --git a/src/user/user_vfs.h b/src/user/user_vfs.h
index c133ef66..416de6f7 100644
--- a/src/user/user_vfs.h
+++ b/src/user/user_vfs.h
@@ -45,11 +45,10 @@ MJAPI int mj_deleteFileVFS(mjVFS* vfs, const char* filename);
 // delete all files from VFS
 MJAPI void mj_deleteVFS(mjVFS* vfs);
 
-// open VFS resource
-MJAPI mjResource* mju_openVfsResource(const char* name, const mjVFS* vfs);
-
 #ifdef __cplusplus
 }
 #endif
 
+const mjpResourceProvider* GetVfsResourceProvider();
+
 #endif  // MUJOCO_SRC_USER_USER_VFS_H_
diff --git a/src/xml/xml.cc b/src/xml/xml.cc
index 7ec8243a..9c64ce2d 100644
--- a/src/xml/xml.cc
+++ b/src/xml/xml.cc
@@ -173,27 +173,23 @@ static void mjIncludeXML(mjXReader& reader, XMLElement* elem,
   } else {
     fullname = filename;
   }
-  mjResource *resource = mju_openVfsResource(fullname.c_str(), vfs);
-  if (!resource) {
-    // load from provider or OS filesystem
-    std::array<char, 1024> error;
-    resource = mju_openResource(fullname.c_str(), error.data(), error.size());
-    if (!resource) {
-      if (!mjuu_isabspath(filename)) {
-        fullname = std::string(dir) + filename;
-      } else {
-        fullname = filename;
-      }
 
-      // load from provider or OS filesystem
-      std::array<char, 1024> error;
-      resource = mju_openResource(fullname.c_str(), error.data(), error.size());
-      if (!resource) {
-        throw mjXError(elem, "%s", error.data());
-      }
+  // legacy behavior: try to load in top level directory
+  std::array<char, 1024> error;
+  mjResource *resource = mju_openResource(fullname.c_str(), vfs,
+                                          error.data(), error.size());
+  if (resource == nullptr) {
+    // new behavior: try to load in relative directory
+    if (!mjuu_isabspath(filename)) {
+      fullname = std::string(dir) + filename;
+      resource = mju_openResource(fullname.c_str(), vfs, error.data(), error.size());
     }
   }
 
+  if (resource == nullptr) {
+    throw mjXError(elem, "%s", error.data());
+  }
+
   if (!mjuu_isabspath(filename)) {
     filename = std::string(dir) + filename;
   }
@@ -293,16 +289,12 @@ mjSpec* mjParseXML(const char* filename, const mjVFS* vfs,
 
   // get data source
   const char* xmlstring = nullptr;
-  mjResource* resource = mju_openVfsResource(filename, vfs);
-
-  if (!resource) {
-    // load from provider or fallback to OS filesystem
-    std::array<char, 1024> rerror;
-    resource = mju_openResource(filename, rerror.data(), rerror.size());
-    if (!resource) {
-      std::snprintf(error, error_sz, "mjParseXML: %s", rerror.data());
-      return nullptr;
-    }
+  std::array<char, 1024> rerror;
+  mjResource* resource = mju_openResource(filename, vfs,
+                                          rerror.data(), rerror.size());
+  if (resource == nullptr) {
+    std::snprintf(error, error_sz, "mjParseXML: %s", rerror.data());
+    return nullptr;
   }
 
   int buffer_size = mju_readResource(resource, (const void**) &xmlstring);
diff --git a/src/xml/xml_api.cc b/src/xml/xml_api.cc
index bb4b4aa9..623466ed 100644
--- a/src/xml/xml_api.cc
+++ b/src/xml/xml_api.cc
@@ -14,6 +14,7 @@
 
 #include "xml/xml_api.h"
 
+#include <array>
 #include <cstdio>
 #include <cstring>
 #include <fstream>
@@ -186,15 +187,12 @@ int mj_printSchema(const char* filename, char* buffer, int buffer_sz, int flg_ht
 
 // load model from binary MJB resource
 mjModel* mj_loadModel(const char* filename, const mjVFS* vfs) {
-  mjResource* resource = nullptr;
-
-  // first try vfs, otherwise try a provider or OS filesystem
-  if (!(resource = mju_openVfsResource(filename, vfs))) {
-    char error[1024];
-    if (!(resource = mju_openResource(filename, error, 1024))) {
-       mju_warning("%s", error);
-      return nullptr;
-    }
+  std::array<char, 1024> error;
+  mjResource* resource = mju_openResource(filename, vfs,
+                                          error.data(), error.size());
+  if (resource == nullptr) {
+    mju_warning("%s", error.data());
+    return nullptr;
   }
 
   const void* buffer = NULL;
diff --git a/src/xml/xml_util.cc b/src/xml/xml_util.cc
index 7defaa85..038dba05 100644
--- a/src/xml/xml_util.cc
+++ b/src/xml/xml_util.cc
@@ -169,7 +169,8 @@ static std::string ResolveFilePath(XMLElement* e, std::string filename,
   // TODO(kylebayes): We first look in the base model directory for files to
   // remain backwards compatible.
   std::string full_filename = mjuu_combinePaths(dir, filename);
-  mjResource *resource = mju_openResource(full_filename.c_str(), nullptr, 0);
+  mjResource *resource = mju_openResource(full_filename.c_str(), nullptr,
+                                          nullptr, 0);
   if (resource != nullptr) {
     mju_closeResource(resource);
     return filename;
diff --git a/test/user/user_cache_test.cc b/test/user/user_cache_test.cc
index e6111bd5..5b353eac 100644
--- a/test/user/user_cache_test.cc
+++ b/test/user/user_cache_test.cc
@@ -47,7 +47,7 @@ void CacheText(mjCCache& cache, const std::string& model,
   mjVFS vfs;
   mj_defaultVFS(&vfs);
   mj_addBufferVFS(&vfs, name.c_str(), text.data(), text.size());
-  mjResource* resource = mju_openVfsResource(name.c_str(), &vfs);
+  mjResource* resource = mju_openResource(name.c_str(), &vfs, nullptr, 0);
   std::shared_ptr<const void> data(&text, +[](const void* data) {});
   cache.Insert(model, resource, data, text.size());
   mju_closeResource(resource);
@@ -61,7 +61,7 @@ GetCachedText(mjCCache& cache, const std::string& model,
   mjVFS vfs;
   mj_defaultVFS(&vfs);
   mj_addBufferVFS(&vfs, name.c_str(), text.data(), std::strlen(text.c_str()));
-  mjResource* resource = mju_openVfsResource(name.c_str(), &vfs);
+  mjResource* resource = mju_openResource(name.c_str(), &vfs, nullptr, 0);
   bool inserted = cache.PopulateData(resource,
                                      [&cached_text](const void* data) {
     cached_text = *(static_cast<const std::string*>(data));
diff --git a/test/user/user_resource_test.cc b/test/user/user_resource_test.cc
index 0f2380d2..3f243641 100644
--- a/test/user/user_resource_test.cc
+++ b/test/user/user_resource_test.cc
@@ -233,7 +233,7 @@ TEST_F(ResourceTest, GeneralTest) {
   EXPECT_GT(i, 0);
 
   // open resource
-  mjResource* resource = mju_openResource("str:file", nullptr, 0);
+  mjResource* resource = mju_openResource("str:file", nullptr, nullptr, 0);
   ASSERT_THAT(resource,  NotNull());
 
   const char* buffer = NULL;
@@ -256,7 +256,7 @@ TEST_F(ResourceTest, GeneralFailureTest) {
   static std::array<char, 1024> error;
 
   // open resource
-  mjResource* resource = mju_openResource("str:notfound",
+  mjResource* resource = mju_openResource("str:notfound", nullptr,
                                           error.data(), error.size());
   ASSERT_THAT(resource, IsNull());
 
@@ -281,7 +281,7 @@ TEST_F(ResourceTest, NameWithValidPrefix) {
   };
 
   // open resource
-  mjResource* resource = mju_openResource("nop:found", nullptr, 0);
+  mjResource* resource = mju_openResource("nop:found", nullptr, nullptr, 0);
   ASSERT_THAT(resource, NotNull());
   mju_closeResource(resource);
 }
@@ -304,7 +304,7 @@ TEST_F(ResourceTest, NameWithUpperCasePrefix) {
   };
 
   // open resource
-  mjResource* resource = mju_openResource("NOP:found", nullptr, 0);
+  mjResource* resource = mju_openResource("NOP:found", nullptr, nullptr, 0);
   ASSERT_THAT(resource, NotNull());
   mju_closeResource(resource);
 }
@@ -327,7 +327,7 @@ TEST_F(ResourceTest, NameWithInvalidPrefix) {
   };
 
   // open resource
-  mjResource* resource = mju_openResource("nopfound", nullptr, 0);
+  mjResource* resource = mju_openResource("nopfound", nullptr, nullptr, 0);
   ASSERT_THAT(resource, IsNull());
 }
 
@@ -338,7 +338,8 @@ TEST_F(ResourceTest, OSFilesystemTimestamps) {
   const char* const file = "engine/testdata/collision_box/boxbox_deep.xml";
   const std::string xml_path = GetTestDataFilePath(file);
 
-  mjResource* resource = mju_openResource(xml_path.c_str(), nullptr, 0);
+  mjResource* resource = mju_openResource(xml_path.c_str(), nullptr,
+                                          nullptr, 0);
   mju_decodeBase64((uint8_t*) &t, resource->timestamp);
 
   // equal timestamps
diff --git a/test/user/user_vfs_test.cc b/test/user/user_vfs_test.cc
index b5931ed6..36378130 100644
--- a/test/user/user_vfs_test.cc
+++ b/test/user/user_vfs_test.cc
@@ -30,7 +30,7 @@ using ::testing::NotNull;
 using UserVfsTest = MujocoTest;
 
 static bool HasFile(const mjVFS* vfs, const std::string& filename) {
-  mjResource* resource = mju_openVfsResource(filename.c_str(), vfs);
+  mjResource* resource = mju_openResource(filename.c_str(), vfs, nullptr, 0);
   bool result = resource != nullptr;
   mju_closeResource(resource);
   return result;
@@ -222,7 +222,7 @@ TEST_F(UserVfsTest, Timestamps) {
   mj_defaultVFS(&vfs);
   mj_addBufferVFS(&vfs, "cube.obj", cube, sizeof(cube));
 
-  mjResource* resource = mju_openVfsResource("cube.obj", &vfs);
+  mjResource* resource = mju_openResource("cube.obj", &vfs, nullptr, 0);
 
   // same timestamps
   EXPECT_EQ(mju_isModifiedResource(resource, resource->timestamp), 0);