--- a/python/mozbuild/mozbuild/mach_commands.py
+++ b/python/mozbuild/mozbuild/mach_commands.py
@@ -1776,21 +1776,18 @@ class PackageFrontend(MachCommandBase):
             open_manifest,
             unpack_file,
         )
         from requests.adapters import HTTPAdapter
         import redo
         import requests
         import shutil
 
-        from taskgraph.generator import Kind
-        from taskgraph.optimize import optimize_task
         from taskgraph.util.taskcluster import (
             get_artifact_url,
-            list_artifacts,
         )
         import yaml
 
         self._set_log_level(verbose)
         # Normally, we'd use self.log_manager.enable_unstructured(),
         # but that enables all logging, while we only really want tooltool's
         # and it also makes structured log output twice.
         # So we manually do what it does, and limit that to the tooltool
@@ -1876,63 +1873,48 @@ class PackageFrontend(MachCommandBase):
                                         record.digest)
                 records[record.filename] = DownloadRecord(
                     url, record.filename, record.size, record.digest,
                     record.algorithm, unpack=record.unpack,
                     version=record.version, visibility=record.visibility,
                     setup=record.setup)
 
         if from_build:
-            params = {
-                'message': '',
-                'project': '',
-                'level': os.environ.get('MOZ_SCM_LEVEL', '3'),
-                'base_repository': '',
-                'head_repository': '',
-                'head_rev': '',
-                'moz_build_date': '',
-                'build_date': 0,
-                'pushlog_id': 0,
-                'owner': '',
-            }
+            from taskgraph.util.taskcluster import find_task_id, get_artifact
+            # find the latest m-c decision task and use its notion of what artifacts are what
+            decision_task_id = find_task_id('gecko.v2.mozilla-central.latest.firefox.decision')
+            full_task_graph = get_artifact(decision_task_id, "public/full-task-graph.json")
+            label_to_taskid = get_artifact(decision_task_id, "public/label-to-taskid.json")
 
-            # TODO: move to the taskcluster package
-            def tasks(kind):
-                kind_path = mozpath.join(self.topsrcdir, 'taskcluster', 'ci', kind)
-                with open(mozpath.join(kind_path, 'kind.yml')) as f:
-                    config = yaml.load(f)
-                    tasks = Kind(kind, kind_path, config).load_tasks(params, {})
-                    return {
-                        task.task['metadata']['name']: task
-                        for task in tasks
-                    }
-
-            toolchains = tasks('toolchain')
+            toolchains = {l: t for l, t in full_task_graph.iteritems()
+                          if t['attributes']['kind'] == 'toolchain'}
 
             aliases = {}
-            for t in toolchains.values():
-                alias = t.attributes.get('toolchain-alias')
+            for l, t in toolchains.items():
+                alias = t['attributes'].get('toolchain-alias')
                 if alias:
-                    aliases['toolchain-{}'.format(alias)] = \
-                        t.task['metadata']['name']
+                    aliases['toolchain-{}'.format(alias)] = l
 
             for b in from_build:
                 user_value = b
 
                 if not b.startswith('toolchain-'):
                     b = 'toolchain-{}'.format(b)
 
                 task = toolchains.get(aliases.get(b, b))
                 if not task:
                     self.log(logging.ERROR, 'artifact', {'build': user_value},
                              'Could not find a toolchain build named `{build}`')
                     return 1
 
-                task_id = optimize_task(task, {})
-                artifact_name = task.attributes.get('toolchain-artifact')
+                # NOTE: if all tasks that used this toolchain were optimized away for this
+                # particular push, then the artifact task will not be found.  See bug 1397847
+                # for a better approach.
+                task_id = label_to_taskid.get(task['label'])
+                artifact_name = task['attributes'].get('toolchain-artifact')
                 if task_id in (True, False) or not artifact_name:
                     self.log(logging.ERROR, 'artifact', {'build': user_value},
                              'Could not find artifacts for a toolchain build '
                              'named `{build}`')
                     return 1
 
                 record = ArtifactRecord(task_id, artifact_name)
                 records[record.filename] = record