diff --git a/command.py b/command.py
index dc765db0..4087cab5 100644
--- a/command.py
+++ b/command.py
@@ -15,7 +15,6 @@
 import multiprocessing
 import os
 import optparse
-import platform
 import re
 import sys
 
@@ -58,11 +57,13 @@ class Command(object):
   # it is the number of parallel jobs to default to.
   PARALLEL_JOBS = None
 
-  def __init__(self, repodir=None, client=None, manifest=None, gitc_manifest=None):
+  def __init__(self, repodir=None, client=None, manifest=None, gitc_manifest=None,
+               git_event_log=None):
     self.repodir = repodir
     self.client = client
     self.manifest = manifest
     self.gitc_manifest = gitc_manifest
+    self.git_event_log = git_event_log
 
     # Cache for the OptionParser property.
     self._optparse = None
diff --git a/git_superproject.py b/git_superproject.py
index 3c4144dd..8f1e04d6 100644
--- a/git_superproject.py
+++ b/git_superproject.py
@@ -19,12 +19,13 @@ https://en.wikibooks.org/wiki/Git/Submodules_and_Superprojects
 
 Examples:
   superproject = Superproject()
-  project_commit_ids = superproject.UpdateProjectsRevisionId(projects)
+  UpdateProjectsResult = superproject.UpdateProjectsRevisionId(projects)
 """
 
 import hashlib
 import os
 import sys
+from typing import NamedTuple
 
 from git_command import git_require, GitCommand
 from git_refs import R_HEADS
@@ -34,6 +35,33 @@ _SUPERPROJECT_GIT_NAME = 'superproject.git'
 _SUPERPROJECT_MANIFEST_NAME = 'superproject_override.xml'
 
 
+class SyncResult(NamedTuple):
+  """Return the status of sync and whether caller should exit."""
+
+  # Whether the superproject sync was successful.
+  success: bool
+  # Whether the caller should exit.
+  fatal: bool
+
+
+class CommitIdsResult(NamedTuple):
+  """Return the commit ids and whether caller should exit."""
+
+  # A dictionary with the projects/commit ids on success, otherwise None.
+  commit_ids: dict
+  # Whether the caller should exit.
+  fatal: bool
+
+
+class UpdateProjectsResult(NamedTuple):
+  """Return the overriding manifest file and whether caller should exit."""
+
+  # Path name of the overriding manfiest file if successful, otherwise None.
+  manifest_path: str
+  # Whether the caller should exit.
+  fatal: bool
+
+
 class Superproject(object):
   """Get commit ids from superproject.
 
@@ -41,19 +69,21 @@ class Superproject(object):
   lookup of commit ids for all projects. It contains _project_commit_ids which
   is a dictionary with project/commit id entries.
   """
-  def __init__(self, manifest, repodir, superproject_dir='exp-superproject',
-               quiet=False):
+  def __init__(self, manifest, repodir, git_event_log,
+               superproject_dir='exp-superproject', quiet=False):
     """Initializes superproject.
 
     Args:
       manifest: A Manifest object that is to be written to a file.
       repodir: Path to the .repo/ dir for holding all internal checkout state.
           It must be in the top directory of the repo client checkout.
+      git_event_log: A git trace2 event log to log events.
       superproject_dir: Relative path under |repodir| to checkout superproject.
       quiet:  If True then only print the progress messages.
     """
     self._project_commit_ids = None
     self._manifest = manifest
+    self._git_event_log = git_event_log
     self._quiet = quiet
     self._branch = self._GetBranch()
     self._repodir = os.path.abspath(repodir)
@@ -172,44 +202,48 @@ class Superproject(object):
     """Gets a local copy of a superproject for the manifest.
 
     Returns:
-      True if sync of superproject is successful, or False.
+      SyncResult
     """
     print('NOTICE: --use-superproject is in beta; report any issues to the '
           'address described in `repo version`', file=sys.stderr)
 
     if not self._manifest.superproject:
-      print('error: superproject tag is not defined in manifest',
-            file=sys.stderr)
-      return False
+      msg = (f'repo error: superproject tag is not defined in manifest: '
+             f'{self._manifest.manifestFile}')
+      print(msg, file=sys.stderr)
+      self._git_event_log.ErrorEvent(msg, '')
+      return SyncResult(False, False)
 
+    should_exit = True
     url = self._manifest.superproject['remote'].url
     if not url:
       print('error: superproject URL is not defined in manifest',
             file=sys.stderr)
-      return False
+      return SyncResult(False, should_exit)
 
     if not self._Init():
-      return False
+      return SyncResult(False, should_exit)
     if not self._Fetch(url):
-      return False
+      return SyncResult(False, should_exit)
     if not self._quiet:
       print('%s: Initial setup for superproject completed.' % self._work_git)
-    return True
+    return SyncResult(True, False)
 
   def _GetAllProjectsCommitIds(self):
     """Get commit ids for all projects from superproject and save them in _project_commit_ids.
 
     Returns:
-      A dictionary with the projects/commit ids on success, otherwise None.
+      CommitIdsResult
     """
-    if not self.Sync():
-      return None
+    sync_result = self.Sync()
+    if not sync_result.success:
+      return CommitIdsResult(None, sync_result.fatal)
 
     data = self._LsTree()
     if not data:
       print('error: git ls-tree failed to return data for superproject',
             file=sys.stderr)
-      return None
+      return CommitIdsResult(None, True)
 
     # Parse lines like the following to select lines starting with '160000' and
     # build a dictionary with project path (last element) and its commit id (3rd element).
@@ -225,7 +259,7 @@ class Superproject(object):
         commit_ids[ls_data[3]] = ls_data[2]
 
     self._project_commit_ids = commit_ids
-    return commit_ids
+    return CommitIdsResult(commit_ids, False)
 
   def _WriteManfiestFile(self):
     """Writes manifest to a file.
@@ -250,6 +284,23 @@ class Superproject(object):
       return None
     return manifest_path
 
+  def _SkipUpdatingProjectRevisionId(self, project):
+    """Checks if a project's revision id needs to be updated or not.
+
+    Revision id for projects from local manifest will not be updated.
+
+    Args:
+      project: project whose revision id is being updated.
+
+    Returns:
+      True if a project's revision id should not be updated, or False,
+    """
+    path = project.relpath
+    if not path:
+      return True
+    # Skip the project if it comes from the local manifest.
+    return any(s.startswith(LOCAL_MANIFEST_GROUP_PREFIX) for s in project.groups)
+
   def UpdateProjectsRevisionId(self, projects):
     """Update revisionId of every project in projects with the commit id.
 
@@ -257,30 +308,35 @@ class Superproject(object):
       projects: List of projects whose revisionId needs to be updated.
 
     Returns:
-      manifest_path: Path name of the overriding manfiest file instead of None.
+      UpdateProjectsResult
     """
-    commit_ids = self._GetAllProjectsCommitIds()
+    commit_ids_result = self._GetAllProjectsCommitIds()
+    commit_ids = commit_ids_result.commit_ids
     if not commit_ids:
       print('error: Cannot get project commit ids from manifest', file=sys.stderr)
-      return None
+      return UpdateProjectsResult(None, commit_ids_result.fatal)
 
     projects_missing_commit_ids = []
     for project in projects:
+      if self._SkipUpdatingProjectRevisionId(project):
+        continue
       path = project.relpath
-      if not path:
-        continue
-      # Skip the project if it comes from local manifest.
-      if any(s.startswith(LOCAL_MANIFEST_GROUP_PREFIX) for s in project.groups):
-        continue
       commit_id = commit_ids.get(path)
-      if commit_id:
-        project.SetRevisionId(commit_id)
-      else:
+      if not commit_id:
         projects_missing_commit_ids.append(path)
+
+    # If superproject doesn't have a commit id for a project, then report an
+    # error event and continue as if do not use superproject is specified.
     if projects_missing_commit_ids:
-      print('error: please file a bug using %s to report missing commit_ids for: %s' %
-            (self._manifest.contactinfo.bugurl, projects_missing_commit_ids), file=sys.stderr)
-      return None
+      msg = (f'error: please file a bug using {self._manifest.contactinfo.bugurl} '
+             f'to report missing commit_ids for: {projects_missing_commit_ids}')
+      print(msg, file=sys.stderr)
+      self._git_event_log.ErrorEvent(msg, '')
+      return UpdateProjectsResult(None, False)
+
+    for project in projects:
+      if not self._SkipUpdatingProjectRevisionId(project):
+        project.SetRevisionId(commit_ids.get(project.relpath))
 
     manifest_path = self._WriteManfiestFile()
-    return manifest_path
+    return UpdateProjectsResult(manifest_path, False)
diff --git a/main.py b/main.py
index 32ad0ff6..f6631f5f 100755
--- a/main.py
+++ b/main.py
@@ -208,7 +208,8 @@ class _Repo(object):
           repodir=self.repodir,
           client=repo_client,
           manifest=repo_client.manifest,
-          gitc_manifest=gitc_manifest)
+          gitc_manifest=gitc_manifest,
+          git_event_log=git_trace2_event_log)
     except KeyError:
       print("repo: '%s' is not a repo command.  See 'repo help'." % name,
             file=sys.stderr)
diff --git a/subcmds/init.py b/subcmds/init.py
index 750facba..536e367c 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import optparse
 import os
 import platform
 import re
@@ -97,10 +96,13 @@ to update the working directory files.
     """
     superproject = git_superproject.Superproject(self.manifest,
                                                  self.repodir,
+                                                 self.git_event_log,
                                                  quiet=opt.quiet)
-    if not superproject.Sync():
+    sync_result = superproject.Sync()
+    if not sync_result.success:
       print('error: git update of superproject failed', file=sys.stderr)
-      sys.exit(1)
+      if sync_result.fatal:
+        sys.exit(1)
 
   def _SyncManifest(self, opt):
     m = self.manifest.manifestProject
diff --git a/subcmds/sync.py b/subcmds/sync.py
index b15d9477..8d89cf72 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -302,21 +302,25 @@ later is required to fix a server side protocol bug.
       load_local_manifests: Whether to load local manifests.
 
     Returns:
-      Returns path to the overriding manifest file.
+      Returns path to the overriding manifest file instead of None.
     """
     superproject = git_superproject.Superproject(self.manifest,
                                                  self.repodir,
+                                                 self.git_event_log,
                                                  quiet=opt.quiet)
     all_projects = self.GetProjects(args,
                                     missing_ok=True,
                                     submodules_ok=opt.fetch_submodules)
-    manifest_path = superproject.UpdateProjectsRevisionId(all_projects)
-    if not manifest_path:
+    update_result = superproject.UpdateProjectsRevisionId(all_projects)
+    manifest_path = update_result.manifest_path
+    if manifest_path:
+      self._ReloadManifest(manifest_path, load_local_manifests)
+    else:
       print('error: Update of revsionId from superproject has failed. '
             'Please resync with --no-use-superproject option',
             file=sys.stderr)
-      sys.exit(1)
-    self._ReloadManifest(manifest_path, load_local_manifests)
+      if update_result.fatal:
+        sys.exit(1)
     return manifest_path
 
   def _FetchProjectList(self, opt, projects):
@@ -961,7 +965,9 @@ later is required to fix a server side protocol bug.
 
     load_local_manifests = not self.manifest.HasLocalManifests
     if self._UseSuperproject(opt):
-      manifest_name = self._UpdateProjectsRevisionId(opt, args, load_local_manifests)
+      new_manifest_name = self._UpdateProjectsRevisionId(opt, args, load_local_manifests)
+      if not new_manifest_name:
+        manifest_name = new_manifest_name
 
     if self.gitc_manifest:
       gitc_manifest_projects = self.GetProjects(args,
diff --git a/tests/test_git_superproject.py b/tests/test_git_superproject.py
index ba61a3d1..d612f4e7 100644
--- a/tests/test_git_superproject.py
+++ b/tests/test_git_superproject.py
@@ -14,6 +14,7 @@
 
 """Unittests for the git_superproject.py module."""
 
+import json
 import os
 import platform
 import tempfile
@@ -21,6 +22,7 @@ import unittest
 from unittest import mock
 
 import git_superproject
+import git_trace2_event_log
 import manifest_xml
 import platform_utils
 from test_manifest_xml import sort_attributes
@@ -29,6 +31,11 @@ from test_manifest_xml import sort_attributes
 class SuperprojectTestCase(unittest.TestCase):
   """TestCase for the Superproject module."""
 
+  PARENT_SID_KEY = 'GIT_TRACE2_PARENT_SID'
+  PARENT_SID_VALUE = 'parent_sid'
+  SELF_SID_REGEX = r'repo-\d+T\d+Z-.*'
+  FULL_SID_REGEX = r'^%s/%s' % (PARENT_SID_VALUE, SELF_SID_REGEX)
+
   def setUp(self):
     """Set up superproject every time."""
     self.tempdir = tempfile.mkdtemp(prefix='repo_tests')
@@ -38,6 +45,13 @@ class SuperprojectTestCase(unittest.TestCase):
     os.mkdir(self.repodir)
     self.platform = platform.system().lower()
 
+    # By default we initialize with the expected case where
+    # repo launches us (so GIT_TRACE2_PARENT_SID is set).
+    env = {
+        self.PARENT_SID_KEY: self.PARENT_SID_VALUE,
+    }
+    self.git_event_log = git_trace2_event_log.EventLog(env=env)
+
     # The manifest parsing really wants a git repo currently.
     gitdir = os.path.join(self.repodir, 'manifests.git')
     os.mkdir(gitdir)
@@ -54,7 +68,8 @@ class SuperprojectTestCase(unittest.TestCase):
   <project path="art" name="platform/art" groups="notdefault,platform-""" + self.platform + """
   " /></manifest>
 """)
-    self._superproject = git_superproject.Superproject(manifest, self.repodir)
+    self._superproject = git_superproject.Superproject(manifest, self.repodir,
+                                                       self.git_event_log)
 
   def tearDown(self):
     """Tear down superproject every time."""
@@ -66,14 +81,56 @@ class SuperprojectTestCase(unittest.TestCase):
       fp.write(data)
     return manifest_xml.XmlManifest(self.repodir, self.manifest_file)
 
+  def verifyCommonKeys(self, log_entry, expected_event_name, full_sid=True):
+    """Helper function to verify common event log keys."""
+    self.assertIn('event', log_entry)
+    self.assertIn('sid', log_entry)
+    self.assertIn('thread', log_entry)
+    self.assertIn('time', log_entry)
+
+    # Do basic data format validation.
+    self.assertEqual(expected_event_name, log_entry['event'])
+    if full_sid:
+      self.assertRegex(log_entry['sid'], self.FULL_SID_REGEX)
+    else:
+      self.assertRegex(log_entry['sid'], self.SELF_SID_REGEX)
+    self.assertRegex(log_entry['time'], r'^\d+-\d+-\d+T\d+:\d+:\d+\.\d+Z$')
+
+  def readLog(self, log_path):
+    """Helper function to read log data into a list."""
+    log_data = []
+    with open(log_path, mode='rb') as f:
+      for line in f:
+        log_data.append(json.loads(line))
+    return log_data
+
+  def verifyErrorEvent(self):
+    """Helper to verify that error event is written."""
+
+    with tempfile.TemporaryDirectory(prefix='event_log_tests') as tempdir:
+      log_path = self.git_event_log.Write(path=tempdir)
+      self.log_data = self.readLog(log_path)
+
+    self.assertEqual(len(self.log_data), 2)
+    error_event = self.log_data[1]
+    self.verifyCommonKeys(self.log_data[0], expected_event_name='version')
+    self.verifyCommonKeys(error_event, expected_event_name='error')
+    # Check for 'error' event specific fields.
+    self.assertIn('msg', error_event)
+    self.assertIn('fmt', error_event)
+
   def test_superproject_get_superproject_no_superproject(self):
     """Test with no url."""
     manifest = self.getXmlManifest("""
 <manifest>
 </manifest>
 """)
-    superproject = git_superproject.Superproject(manifest, self.repodir)
-    self.assertFalse(superproject.Sync())
+    superproject = git_superproject.Superproject(manifest, self.repodir, self.git_event_log)
+    # Test that exit condition is false when there is no superproject tag.
+    sync_result = superproject.Sync()
+    self.assertFalse(sync_result.success)
+    self.assertFalse(sync_result.fatal)
+    self.verifyErrorEvent()
 
   def test_superproject_get_superproject_invalid_url(self):
     """Test with an invalid url."""
@@ -84,8 +141,10 @@ class SuperprojectTestCase(unittest.TestCase):
   <superproject name="superproject"/>
 </manifest>
 """)
-    superproject = git_superproject.Superproject(manifest, self.repodir)
-    self.assertFalse(superproject.Sync())
+    superproject = git_superproject.Superproject(manifest, self.repodir, self.git_event_log)
+    sync_result = superproject.Sync()
+    self.assertFalse(sync_result.success)
+    self.assertTrue(sync_result.fatal)
 
   def test_superproject_get_superproject_invalid_branch(self):
     """Test with an invalid branch."""
@@ -96,21 +155,28 @@ class SuperprojectTestCase(unittest.TestCase):
   <superproject name="superproject"/>
 </manifest>
 """)
-    superproject = git_superproject.Superproject(manifest, self.repodir)
+    self._superproject = git_superproject.Superproject(manifest, self.repodir,
+                                                       self.git_event_log)
     with mock.patch.object(self._superproject, '_GetBranch', return_value='junk'):
-      self.assertFalse(superproject.Sync())
+      sync_result = self._superproject.Sync()
+      self.assertFalse(sync_result.success)
+      self.assertTrue(sync_result.fatal)
 
   def test_superproject_get_superproject_mock_init(self):
     """Test with _Init failing."""
     with mock.patch.object(self._superproject, '_Init', return_value=False):
-      self.assertFalse(self._superproject.Sync())
+      sync_result = self._superproject.Sync()
+      self.assertFalse(sync_result.success)
+      self.assertTrue(sync_result.fatal)
 
   def test_superproject_get_superproject_mock_fetch(self):
     """Test with _Fetch failing."""
     with mock.patch.object(self._superproject, '_Init', return_value=True):
       os.mkdir(self._superproject._superproject_path)
       with mock.patch.object(self._superproject, '_Fetch', return_value=False):
-        self.assertFalse(self._superproject.Sync())
+        sync_result = self._superproject.Sync()
+        self.assertFalse(sync_result.success)
+        self.assertTrue(sync_result.fatal)
 
   def test_superproject_get_all_project_commit_ids_mock_ls_tree(self):
     """Test with LsTree being a mock."""
@@ -122,12 +188,13 @@ class SuperprojectTestCase(unittest.TestCase):
     with mock.patch.object(self._superproject, '_Init', return_value=True):
       with mock.patch.object(self._superproject, '_Fetch', return_value=True):
         with mock.patch.object(self._superproject, '_LsTree', return_value=data):
-          commit_ids = self._superproject._GetAllProjectsCommitIds()
-          self.assertEqual(commit_ids, {
+          commit_ids_result = self._superproject._GetAllProjectsCommitIds()
+          self.assertEqual(commit_ids_result.commit_ids, {
               'art': '2c2724cb36cd5a9cec6c852c681efc3b7c6b86ea',
               'bootable/recovery': 'e9d25da64d8d365dbba7c8ee00fe8c4473fe9a06',
               'build/bazel': 'ade9b7a0d874e25fff4bf2552488825c6f111928'
           })
+          self.assertFalse(commit_ids_result.fatal)
 
   def test_superproject_write_manifest_file(self):
     """Test with writing manifest to a file after setting revisionId."""
@@ -163,9 +230,10 @@ class SuperprojectTestCase(unittest.TestCase):
                                return_value=data):
           # Create temporary directory so that it can write the file.
           os.mkdir(self._superproject._superproject_path)
-          manifest_path = self._superproject.UpdateProjectsRevisionId(projects)
-          self.assertIsNotNone(manifest_path)
-          with open(manifest_path, 'r') as fp:
+          update_result = self._superproject.UpdateProjectsRevisionId(projects)
+          self.assertIsNotNone(update_result.manifest_path)
+          self.assertFalse(update_result.fatal)
+          with open(update_result.manifest_path, 'r') as fp:
             manifest_xml_data = fp.read()
           self.assertEqual(
               sort_attributes(manifest_xml_data),
@@ -178,6 +246,34 @@ class SuperprojectTestCase(unittest.TestCase):
               '<superproject name="superproject"/>'
               '</manifest>')
 
+  def test_superproject_update_project_revision_id_no_superproject_tag(self):
+    """Test update of commit ids of a manifest without superproject tag."""
+    manifest = self.getXmlManifest("""
+<manifest>
+  <remote name="default-remote" fetch="http://localhost" />
+  <default remote="default-remote" revision="refs/heads/main" />
+  <project name="test-name"/>
+</manifest>
+""")
+    self.maxDiff = None
+    self._superproject = git_superproject.Superproject(manifest, self.repodir,
+                                                       self.git_event_log)
+    self.assertEqual(len(self._superproject._manifest.projects), 1)
+    projects = self._superproject._manifest.projects
+    project = projects[0]
+    project.SetRevisionId('ABCDEF')
+    update_result = self._superproject.UpdateProjectsRevisionId(projects)
+    self.assertIsNone(update_result.manifest_path)
+    self.assertFalse(update_result.fatal)
+    self.verifyErrorEvent()
+    self.assertEqual(
+        sort_attributes(manifest.ToXml().toxml()),
+        '<?xml version="1.0" ?><manifest>'
+        '<remote fetch="http://localhost" name="default-remote"/>'
+        '<default remote="default-remote" revision="refs/heads/main"/>'
+        '<project name="test-name" revision="ABCDEF"/>'
+        '</manifest>')
+
   def test_superproject_update_project_revision_id_from_local_manifest_group(self):
     """Test update of commit ids of a manifest that have local manifest no superproject group."""
     local_group = manifest_xml.LOCAL_MANIFEST_GROUP_PREFIX + ':local'
@@ -194,7 +290,8 @@ class SuperprojectTestCase(unittest.TestCase):
   " /></manifest>
 """)
     self.maxDiff = None
-    self._superproject = git_superproject.Superproject(manifest, self.repodir)
+    self._superproject = git_superproject.Superproject(manifest, self.repodir,
+                                                       self.git_event_log)
     self.assertEqual(len(self._superproject._manifest.projects), 2)
     projects = self._superproject._manifest.projects
     data = ('160000 commit 2c2724cb36cd5a9cec6c852c681efc3b7c6b86ea\tart\x00'
@@ -206,9 +303,10 @@ class SuperprojectTestCase(unittest.TestCase):
                                return_value=data):
           # Create temporary directory so that it can write the file.
           os.mkdir(self._superproject._superproject_path)
-          manifest_path = self._superproject.UpdateProjectsRevisionId(projects)
-          self.assertIsNotNone(manifest_path)
-          with open(manifest_path, 'r') as fp:
+          update_result = self._superproject.UpdateProjectsRevisionId(projects)
+          self.assertIsNotNone(update_result.manifest_path)
+          self.assertFalse(update_result.fatal)
+          with open(update_result.manifest_path, 'r') as fp:
             manifest_xml_data = fp.read()
           # Verify platform/vendor/x's project revision hasn't changed.
           self.assertEqual(