--- a/misc.py
+++ b/misc.py
@@ -710,16 +710,17 @@ def makeMHFactory(config, pf, mh_cfg=Non
         scriptRepo=scriptRepo,
         interpreter=mh_cfg.get('mozharness_python', pf.get('mozharness_python')),
         scriptName=mh_cfg['script_name'],
         reboot_command=mh_cfg.get('reboot_command', pf.get('reboot_command')),
         extra_args=extra_args,
         script_timeout=mh_cfg.get('script_timeout', pf.get('timeout', 3600)),
         script_maxtime=mh_cfg.get('script_maxtime', pf.get('maxTime', 4 * 3600)),
         script_repo_cache=script_repo_cache,
+        script_repo_manifest=config.get('script_repo_manifest'),
         tools_repo_cache=mh_cfg.get('tools_repo_cache',
                                     pf.get('tools_repo_cache')),
         **kwargs
     )
     return factory
 
 
 def makeBundleBuilder(config, name):
@@ -993,16 +994,18 @@ def generateDesktopMozharnessBuilders(na
     # look mom, no buildbot properties needed for desktop
     # mozharness builds!!
     mh_build_properties = {
         # our buildbot master.cfg requires us to at least have
         # these but mozharness doesn't need them
         'branch': name,
         'platform': platform,
         'product': pf['stage_product'],
+        'repo_path': config['repo_path'],
+        'script_repo_revision': config["mozharness_tag"],
     }
     dep_signing_servers = secrets.get(pf.get('dep_signing_servers'))
     nightly_signing_servers = secrets.get(pf.get('nightly_signing_servers'))
 
     # grab the l10n schedulers that nightlies will trigger (if any)
     triggered_nightly_schedulers = []
     if (config['enable_l10n'] and platform in config['l10n_platforms'] and
             '%s nightly' % pf['base_name'] in l10nNightlyBuilders):

--- a/process/factory.py
+++ b/process/factory.py
@@ -5345,59 +5345,88 @@ class ScriptFactory(RequestSortingBuildF
                 workdir="."
             ))
             self.env['EXTRA_DATA'] = WithProperties('%(basedir)s/data.json')
         self.addStep(ShellCommand(
             name="clobber_properties",
             command=['rm', '-rf', 'properties'],
             workdir=".",
         ))
-        self.addStep(SetProperty(
-            name='set_script_repo_url',
-            command=['echo', scriptRepo],
-            property='script_repo_url',
+        self.addStep(SetBuildProperty(
+            property_name='script_repo_url',
+            value=scriptRepo,
         ))
         script_repo_url = WithProperties('%(script_repo_url)s')
 
         if self.script_repo_cache:
             # all slaves bar win tests have a copy of hgtool on their path.
             # However, let's use runner's checkout version like we do for
             # script repo
             assert self.tools_repo_cache
             # ScriptFactory adds the props file into its env but we don't
             # want to pass that to the hgtool call because hgtool will assume
             # things like ['sourcestamp']['branch'] should be our branch
             # that script_repo pulls from
+            hgtool_path = \
+                    os.path.join(self.tools_repo_cache,
+                                 'buildfarm',
+                                 'utils',
+                                 'hgtool.py')
+            repository_manifest_path = \
+                    os.path.join(self.tools_repo_cache,
+                                'buildfarm',
+                                'utils',
+                                'repository_manifest.py')
+
+            if script_repo_manifest:
+                self.addStep(SetProperty(
+                    name="set_script_repo_url_and_script_repo_revision",
+                    extract_fn=extractProperties,
+                    command=['bash', '-c',
+                        WithProperties(
+                        'python %s ' % repository_manifest_path +
+                        '--default-repo %s ' % scriptRepo +
+                        '--default-revision %(script_repo_revision:-default)s ' +
+                        '--default-checkout %s ' % self.script_repo_cache +
+                        '--checkout %(basedir)s/build/scripts ' +
+                        '--manifest-url %s' % script_repo_manifest)],
+                    log_eval_func=rc_eval_func({0: SUCCESS, None: EXCEPTION}),
+                    haltOnFailure=True,
+                ))
+            else:
+                self.addStep(SetBuildProperty(
+                    property_name='script_repo_checkout',
+                    value=self.script_repo_cache,
+                ))
+
             hg_script_repo_env = self.env.copy()
             hg_script_repo_env.pop('PROPERTIES_FILE', None)
-            hgtool_path = os.path.join(self.tools_repo_cache,
-                                       'buildfarm',
-                                       'utils',
-                                       'hgtool.py')
+
             hgtool_cmd = [
                 'python', hgtool_path, '--purge',
                 '-r', WithProperties('%(script_repo_revision:-default)s'),
-                scriptRepo, self.script_repo_cache
+                WithProperties('%(script_repo_url)s'),
+                WithProperties('%(script_repo_checkout)s'),
             ]
+
             self.addStep(ShellCommand(
                 name='update_script_repo_cache',
                 command=hgtool_cmd,
                 env=hg_script_repo_env,
                 haltOnFailure=True,
-                workdir=os.path.dirname(self.script_repo_cache),
                 flunkOnFailure=True,
             ))
             self.addStep(SetProperty(
                 name='get_script_repo_revision',
                 property='script_repo_revision',
                 command=[hg_bin, 'id', '-i'],
-                workdir=self.script_repo_cache,
+                workdir=WithProperties('%(script_repo_checkout)s'),
                 haltOnFailure=False,
             ))
-            script_path = '%s/%s' % (script_repo_cache, scriptName)
+            script_path = WithProperties('%(script_repo_checkout)s/' + scriptName)
         else:
             # fall back to legacy clobbering + cloning script repo
             if script_repo_manifest:
                 # By setting scriptRepoManifest we indicate that we don't
                 # want to use scriptRepo but we want to let the manifest associated
                 # to set the repo to checkout and which revision/branch to update to
                 # If the repo specified in the manifest matches scriptRepo we will
                 # use the cached version if available (i.e. script_repo_cache has