diff --git a/lib/galaxy/dependencies/dev-requirements.txt b/lib/galaxy/dependencies/dev-requirements.txt
index 92c59a38551..6247364dab5 100644
--- a/lib/galaxy/dependencies/dev-requirements.txt
+++ b/lib/galaxy/dependencies/dev-requirements.txt
@@ -6,6 +6,8 @@ alabaster==0.7.12; python_version >= "3.5"
 amqp==5.0.3; python_version >= "3.6"
 appdirs==1.4.4; python_version >= "3.6"
 argcomplete==1.12.2; python_version >= "3.6" and python_version < "4"
+async-exit-stack==1.0.1; python_version >= "3.6" and python_version < "3.7"
+async-generator==1.10; python_version >= "3.6" and python_version < "3.7"
 atomicwrites==1.4.0; python_version >= "3.6" and python_full_version < "3.0.0" and sys_platform == "win32" and (python_version >= "3.6" and python_full_version < "3.0.0" or python_full_version >= "3.5.0" and python_version >= "3.6") or sys_platform == "win32" and python_version >= "3.6" and python_full_version >= "3.4.0" and (python_version >= "3.6" and python_full_version < "3.0.0" or python_full_version >= "3.5.0" and python_version >= "3.6")
 attmap==0.12.11
 attrs==20.3.0; python_version >= "3.6" and python_full_version < "3.0.0" or python_full_version >= "3.5.0" and python_version >= "3.6"
diff --git a/lib/galaxy/dependencies/pinned-requirements.txt b/lib/galaxy/dependencies/pinned-requirements.txt
index ba1b06b2a07..22cb517c5d2 100644
--- a/lib/galaxy/dependencies/pinned-requirements.txt
+++ b/lib/galaxy/dependencies/pinned-requirements.txt
@@ -5,6 +5,8 @@ aiofiles==0.6.0
 amqp==5.0.3; python_version >= "3.6"
 appdirs==1.4.4; python_version >= "3.6"
 argcomplete==1.12.2; python_version >= "3.6" and python_version < "4"
+async-exit-stack==1.0.1; python_version >= "3.6" and python_version < "3.7"
+async-generator==1.10; python_version >= "3.6" and python_version < "3.7"
 attmap==0.12.11
 attrs==20.3.0; python_version >= "3.6" and python_full_version < "3.0.0" or python_full_version >= "3.4.0" and python_version >= "3.6"
 babel==2.9.0; (python_version >= "2.7" and python_full_version < "3.0.0") or (python_full_version >= "3.4.0")
diff --git a/lib/galaxy/exceptions/__init__.py b/lib/galaxy/exceptions/__init__.py
index c79d1f9c8c6..9871df1be09 100644
--- a/lib/galaxy/exceptions/__init__.py
+++ b/lib/galaxy/exceptions/__init__.py
@@ -87,6 +87,11 @@ class MalformedId(MessageException):
     err_code = error_codes_by_name['MALFORMED_ID']
 
 
+class UserInvalidRunAsException(MessageException):
+    status_code = 400
+    err_code = error_codes_by_name['USER_INVALID_RUN_AS']
+
+
 class MalformedContents(MessageException):
     status_code = 400
     err_code = error_codes_by_name['MALFORMED_CONTENTS']
@@ -157,6 +162,11 @@ class InsufficientPermissionsException(MessageException):
     err_code = error_codes_by_name['INSUFFICIENT_PERMISSIONS']
 
 
+class UserCannotRunAsException(MessageException):
+    status_code = 403
+    err_code = error_codes_by_name['USER_CANNOT_RUN_AS']
+
+
 class AdminRequiredException(MessageException):
     status_code = 403
     err_code = error_codes_by_name['ADMIN_REQUIRED']
diff --git a/lib/galaxy/job_execution/ports/view.py b/lib/galaxy/job_execution/ports/view.py
index b84955e08c2..d9390c30496 100644
--- a/lib/galaxy/job_execution/ports/view.py
+++ b/lib/galaxy/job_execution/ports/view.py
@@ -34,7 +34,7 @@ class JobPortsView:
             raise ItemAccessibilityException("Invalid job_key supplied.")
 
         # Verify job is active. Don't update the contents of complete jobs.
-        sa_session = self._app.model.context.current
+        sa_session = self._app.model.session
         job = sa_session.query(model.Job).get(job_id)
         if not job.running:
             error_message = "Attempting to read or modify the files of a job that has already completed."
diff --git a/lib/galaxy/jobs/runners/pulsar.py b/lib/galaxy/jobs/runners/pulsar.py
index bd3633a52ee..d60c1fc9748 100644
--- a/lib/galaxy/jobs/runners/pulsar.py
+++ b/lib/galaxy/jobs/runners/pulsar.py
@@ -883,7 +883,7 @@ class PulsarJobRunner(AsynchronousJobRunner):
             remote_job_id = full_status["job_id"]
             if len(remote_job_id) == 32:
                 # It is a UUID - assign_ids = uuid in destination params...
-                sa_session = self.app.model.context.current
+                sa_session = self.app.model.session
                 galaxy_job_id = sa_session.query(model.Job).filter(model.Job.job_runner_external_id == remote_job_id).one().id
             else:
                 galaxy_job_id = remote_job_id
diff --git a/lib/galaxy/managers/context.py b/lib/galaxy/managers/context.py
index 16f74881e32..4b9069a6f85 100644
--- a/lib/galaxy/managers/context.py
+++ b/lib/galaxy/managers/context.py
@@ -42,7 +42,12 @@ from typing import List, Optional
 from sqlalchemy.orm.scoping import scoped_session
 
 from galaxy.exceptions import UserActivationRequiredException
-from galaxy.model import Dataset, History, HistoryDatasetAssociation, Role
+from galaxy.model import (
+    Dataset,
+    History,
+    HistoryDatasetAssociation,
+    Role,
+)
 from galaxy.model.base import ModelMapping
 from galaxy.security.idencoding import IdEncodingHelper
 from galaxy.structured_app import StructuredApp
@@ -126,7 +131,7 @@ class ProvidesAppContext:
 
         :rtype: sqlalchemy.orm.scoping.scoped_session
         """
-        return self.app.model.context.current
+        return self.app.model.session
 
     def expunge_all(self):
         """Expunge all the objects in Galaxy's SQLAlchemy sessions."""
@@ -201,13 +206,7 @@ class ProvidesUserContext(ProvidesAppContext):
 
     @property
     def user_can_do_run_as(self) -> bool:
-        run_as_users = [user for user in self.app.config.get("api_allow_run_as", "").split(",") if user]
-        if not run_as_users:
-            return False
-        user_in_run_as_users = self.user and self.user.email in run_as_users
-        # Can do if explicitly in list or master_api_key supplied.
-        can_do_run_as = user_in_run_as_users or self.user.bootstrap_admin_user
-        return can_do_run_as
+        return self.app.user_manager.user_can_do_run_as(self.user)
 
     @property
     def user_is_active(self) -> bool:
diff --git a/lib/galaxy/managers/jobs.py b/lib/galaxy/managers/jobs.py
index 40cab0a1481..8ebdd07400a 100644
--- a/lib/galaxy/managers/jobs.py
+++ b/lib/galaxy/managers/jobs.py
@@ -84,7 +84,7 @@ class JobManager:
     def stop(self, job, message=None):
         if not job.finished:
             job.mark_deleted(self.app.config.track_jobs_in_database)
-            self.app.model.context.current.flush()
+            self.app.model.session.flush()
             self.app.job_manager.stop(job, message=message)
             return True
         else:
diff --git a/lib/galaxy/managers/tags.py b/lib/galaxy/managers/tags.py
index a166d2578ba..6f059f49014 100644
--- a/lib/galaxy/managers/tags.py
+++ b/lib/galaxy/managers/tags.py
@@ -11,6 +11,7 @@ from pydantic import (
 
 from galaxy.managers.context import ProvidesUserContext
 from galaxy.model import ItemTagAssociation
+from galaxy.model.tags import GalaxyTagHandlerSession
 from galaxy.schema.fields import EncodedDatabaseIdField
 
 taggable_item_names = {item: item for item in ItemTagAssociation.associated_item_names}
@@ -45,7 +46,7 @@ class TagsManager:
 
     def update(self, trans: ProvidesUserContext, payload: ItemTagsPayload) -> None:
         """Apply a new set of tags to an item; previous tags are deleted."""
-        tag_handler = trans.app.tag_handler
+        tag_handler = GalaxyTagHandlerSession(trans.sa_session)
         new_tags: Optional[str] = None
         if payload.item_tags and len(payload.item_tags) > 0:
             new_tags = ",".join(payload.item_tags)
@@ -59,7 +60,7 @@ class TagsManager:
         """
         Get an item based on type and id.
         """
-        tag_handler = trans.app.tag_handler
+        tag_handler = GalaxyTagHandlerSession(trans.sa_session)
         id = trans.security.decode_id(payload.item_id)
         item_class = tag_handler.item_tag_assoc_info[payload.item_class].item_class
         item = trans.sa_session.query(item_class).filter(item_class.id == id).first()
diff --git a/lib/galaxy/managers/users.py b/lib/galaxy/managers/users.py
index 36dc4239402..9a76959b626 100644
--- a/lib/galaxy/managers/users.py
+++ b/lib/galaxy/managers/users.py
@@ -225,6 +225,9 @@ class UserManager(base.ModelManager, deletable.PurgableManagerMixin):
         if self.by_email(email) is not None:
             raise exceptions.Conflict('Email must be unique', email=email)
 
+    def by_id(self, user_id):
+        return self.app.model.session.query(self.model_class).get(user_id)
+
     # ---- filters
     def by_email(self, email, filters=None, **kwargs):
         """
@@ -352,6 +355,15 @@ class UserManager(base.ModelManager, deletable.PurgableManagerMixin):
         # TODO: seems like this should return the model
         return api_keys.ApiKeyManager(self.app).create_api_key(user)
 
+    def user_can_do_run_as(self, user) -> bool:
+        run_as_users = [u for u in self.app.config.get("api_allow_run_as", "").split(",") if u]
+        if not run_as_users:
+            return False
+        user_in_run_as_users = user and user.email in run_as_users
+        # Can do if explicitly in list or master_api_key supplied.
+        can_do_run_as = user_in_run_as_users or user.bootstrap_admin_user
+        return can_do_run_as
+
     # TODO: possibly move to ApiKeyManager
     def valid_api_key(self, user):
         """
diff --git a/lib/galaxy/model/base.py b/lib/galaxy/model/base.py
index 31cd7b40eba..aaf92d53289 100644
--- a/lib/galaxy/model/base.py
+++ b/lib/galaxy/model/base.py
@@ -21,14 +21,15 @@ class ModelMapping(Bunch):
 
     def __init__(self, model_modules, engine):
         self.engine = engine
-        Session = sessionmaker(autoflush=False, autocommit=True)
-        versioned_session(Session)
-        context = scoped_session(Session)
+        SessionLocal = sessionmaker(autoflush=False, autocommit=True)
+        versioned_session(SessionLocal)
+        context = scoped_session(SessionLocal)
         # For backward compatibility with "context.current"
         # deprecated?
         context.current = context
-        self.context = context
-        self.session = context
+        self._SessionLocal = SessionLocal
+        self._session = context
+        self.local_session = None
 
         model_classes = {}
         for module in model_modules:
@@ -41,6 +42,27 @@ class ModelMapping(Bunch):
         context.remove()
         context.configure(bind=engine)
 
+    def set_local_session(self):
+        self.session = self._SessionLocal()
+
+    def dispose_local_session(self):
+        self.session = None
+
+    @property
+    def session(self):
+        return self.local_session or self._session
+
+    @session.setter
+    def session(self, session):
+        # For backward compatibility with "context.current"
+        if session:
+            session.current = session
+        self.local_session = session
+
+    @property
+    def context(self):
+        return self.session
+
     @property
     def Session(self):
         """
diff --git a/lib/galaxy/model/store/__init__.py b/lib/galaxy/model/store/__init__.py
index bc7fb924906..46bacd26801 100644
--- a/lib/galaxy/model/store/__init__.py
+++ b/lib/galaxy/model/store/__init__.py
@@ -78,7 +78,7 @@ class ModelImportStore(metaclass=abc.ABCMeta):
         self.object_store = object_store
         self.app = app
         if app is not None:
-            self.sa_session = app.model.context.current
+            self.sa_session = app.model.session
             self.sessionless = False
         else:
             self.sa_session = SessionlessContext()
@@ -1137,7 +1137,7 @@ class DirectoryModelExportStore(ModelExportStore):
         with open(history_attrs_filename, 'w') as history_attrs_out:
             dump(history_attrs, history_attrs_out)
 
-        sa_session = app.model.context.current
+        sa_session = app.model.session
 
         # Write collections' attributes (including datasets list) to file.
         query = (sa_session.query(model.HistoryDatasetCollectionAssociation)
diff --git a/lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py b/lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py
index 06558b4e497..68ef4616c1e 100644
--- a/lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py
+++ b/lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py
@@ -110,8 +110,8 @@ class InstalledRepositoryManager:
                                           data_manager_relative_install_dir,
                                           repository,
                                           repository_tools_tups)
-        self.install_model.context.current.add(repository)
-        self.install_model.context.current.flush()
+        self.install_model.session.add(repository)
+        self.install_model.session.flush()
         if repository.includes_datatypes:
             if tool_path:
                 repository_install_dir = os.path.abspath(os.path.join(tool_path, relative_install_dir))
@@ -663,13 +663,13 @@ class InstalledRepositoryManager:
             repository.error_message = None
         else:
             repository.status = self.app.install_model.ToolShedRepository.installation_status.DEACTIVATED
-        self.app.install_model.context.current.add(repository)
-        self.app.install_model.context.current.flush()
+        self.app.install_model.session.add(repository)
+        self.app.install_model.session.flush()
         return errors
 
     def purge_repository(self, repository):
         """Purge a repository with status New (a white ghost) from the database."""
-        sa_session = self.app.model.context.current
+        sa_session = self.app.model.session
         status = 'ok'
         message = ''
         purged_tool_versions = 0
diff --git a/lib/galaxy/tool_shed/galaxy_install/migrate/common.py b/lib/galaxy/tool_shed/galaxy_install/migrate/common.py
index 32644c4021a..96946914ab3 100644
--- a/lib/galaxy/tool_shed/galaxy_install/migrate/common.py
+++ b/lib/galaxy/tool_shed/galaxy_install/migrate/common.py
@@ -66,7 +66,7 @@ class MigrateToolsApplication(galaxy.config.ConfiguresGalaxyMixin):
 
     @property
     def sa_session(self):
-        return self.model.context.current
+        return self.model.session
 
     def shutdown(self):
         self.object_store.shutdown()
diff --git a/lib/galaxy/tool_shed/metadata/metadata_generator.py b/lib/galaxy/tool_shed/metadata/metadata_generator.py
index e3741039d28..dcdc2009204 100644
--- a/lib/galaxy/tool_shed/metadata/metadata_generator.py
+++ b/lib/galaxy/tool_shed/metadata/metadata_generator.py
@@ -100,7 +100,7 @@ class MetadataGenerator:
         self.updating_installed_repository = updating_installed_repository
         self.persist = persist
         self.invalid_file_tups = []
-        self.sa_session = app.model.context.current
+        self.sa_session = app.model.session
         self.NOT_TOOL_CONFIGS = [suc.DATATYPES_CONFIG_FILENAME,
                                  REPOSITORY_DEPENDENCY_DEFINITION_FILENAME,
                                  TOOL_DEPENDENCY_DEFINITION_FILENAME,
diff --git a/lib/galaxy/tool_shed/util/repository_util.py b/lib/galaxy/tool_shed/util/repository_util.py
index 3adc5e2fbdd..905a4778cc0 100644
--- a/lib/galaxy/tool_shed/util/repository_util.py
+++ b/lib/galaxy/tool_shed/util/repository_util.py
@@ -308,7 +308,7 @@ def get_repository_by_id(app, id):
     if is_tool_shed_client(app):
         return app.install_model.context.query(app.install_model.ToolShedRepository).get(app.security.decode_id(id))
     else:
-        sa_session = app.model.context.current
+        sa_session = app.model.session
         return sa_session.query(app.model.Repository).get(app.security.decode_id(id))
 
 
@@ -495,7 +495,7 @@ def get_repository_query(app):
 
 def get_role_by_id(app, role_id):
     """Get a Role from the database by id."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.Role).get(app.security.decode_id(role_id))
 
 
diff --git a/lib/galaxy/tool_shed/util/shed_util_common.py b/lib/galaxy/tool_shed/util/shed_util_common.py
index 0d3eb393796..42647404eb4 100644
--- a/lib/galaxy/tool_shed/util/shed_util_common.py
+++ b/lib/galaxy/tool_shed/util/shed_util_common.py
@@ -157,7 +157,7 @@ def get_tool_panel_config_tool_path_install_dir(app, repository):
 
 def get_user(app, id):
     """Get a user from the database by id."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.User).get(app.security.decode_id(id))
 
 
diff --git a/lib/galaxy/tool_util/verify/interactor.py b/lib/galaxy/tool_util/verify/interactor.py
index aa224b04fdb..b8686c7d097 100644
--- a/lib/galaxy/tool_util/verify/interactor.py
+++ b/lib/galaxy/tool_util/verify/interactor.py
@@ -670,36 +670,36 @@ class GalaxyInteractorApi:
 
         return fetcher
 
-    def api_key_header(self, key, admin, anon):
-        header = {}
+    def api_key_header(self, key, admin, anon, headers):
+        header = headers or {}
         if not anon:
             if not key:
                 key = self.api_key if not admin else self.master_api_key
             header['x-api-key'] = key
         return header
 
-    def _post(self, path, data=None, files=None, key=None, admin=False, anon=False, json=False):
+    def _post(self, path, data=None, files=None, key=None, headers=None, admin=False, anon=False, json=False):
         # If json=True, use post payload using request's json parameter instead of the data
         # parameter (i.e. assume the contents is a jsonified blob instead of form parameters
         # with individual parameters jsonified if needed).
-        headers = self.api_key_header(key=key, admin=admin, anon=anon)
+        headers = self.api_key_header(key=key, admin=admin, anon=anon, headers=headers)
         url = f"{self.api_url}/{path}"
         return galaxy_requests_post(url, data=data, files=files, as_json=json, headers=headers)
 
-    def _delete(self, path, data=None, key=None, admin=False, anon=False):
-        headers = self.api_key_header(key=key, admin=admin, anon=anon)
+    def _delete(self, path, data=None, key=None, headers=None, admin=False, anon=False):
+        headers = self.api_key_header(key=key, admin=admin, anon=anon, headers=headers)
         return requests.delete(f"{self.api_url}/{path}", params=data, headers=headers)
 
-    def _patch(self, path, data=None, key=None, admin=False, anon=False):
-        headers = self.api_key_header(key=key, admin=admin, anon=anon)
+    def _patch(self, path, data=None, key=None, headers=None, admin=False, anon=False):
+        headers = self.api_key_header(key=key, admin=admin, anon=anon, headers=headers)
         return requests.patch(f"{self.api_url}/{path}", data=data, headers=headers)
 
-    def _put(self, path, data=None, key=None, admin=False, anon=False):
-        headers = self.api_key_header(key=key, admin=admin, anon=anon)
+    def _put(self, path, data=None, key=None, headers=None, admin=False, anon=False):
+        headers = self.api_key_header(key=key, admin=admin, anon=anon, headers=headers)
         return requests.put(f"{self.api_url}/{path}", data=data, headers=headers)
 
-    def _get(self, path, data=None, key=None, admin=False, anon=False):
-        headers = self.api_key_header(key=key, admin=admin, anon=anon)
+    def _get(self, path, data=None, key=None, headers=None, admin=False, anon=False):
+        headers = self.api_key_header(key=key, admin=admin, anon=anon, headers=headers)
         if path.startswith("/api"):
             path = path[len("/api"):]
         url = f"{self.api_url}/{path}"
diff --git a/lib/galaxy/tools/cache.py b/lib/galaxy/tools/cache.py
index 771e0c29c36..501c8d4641f 100644
--- a/lib/galaxy/tools/cache.py
+++ b/lib/galaxy/tools/cache.py
@@ -293,7 +293,7 @@ class ToolShedRepositoryCache:
 
     def rebuild(self):
         try:
-            session = self.app.install_model.context.current.session_factory()
+            session = self.app.install_model._SessionLocal()
             self.repositories = session.query(self.app.install_model.ToolShedRepository).options(
                 defer(self.app.install_model.ToolShedRepository.metadata),
                 joinedload('tool_dependencies').subqueryload('tool_shed_repository').options(
diff --git a/lib/galaxy/util/tool_shed/common_util.py b/lib/galaxy/util/tool_shed/common_util.py
index e5a700f371d..ceeb94894bd 100644
--- a/lib/galaxy/util/tool_shed/common_util.py
+++ b/lib/galaxy/util/tool_shed/common_util.py
@@ -271,7 +271,7 @@ def get_tool_shed_repository_url(app, tool_shed, owner, name):
 
 def get_user_by_username(app, username):
     """Get a user from the database by username."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     try:
         user = sa_session.query(app.model.User) \
                          .filter(app.model.User.table.c.username == username) \
diff --git a/lib/galaxy/web/framework/decorators.py b/lib/galaxy/web/framework/decorators.py
index 475fe3ce052..75388fc0892 100644
--- a/lib/galaxy/web/framework/decorators.py
+++ b/lib/galaxy/web/framework/decorators.py
@@ -221,6 +221,9 @@ def __extract_payload_from_request(trans, func, kwargs):
         # should ideally be in reverse, with the if clause being a check for application/json and the else clause assuming a standard encoding
         # such as multipart/form-data. Leaving it as is for backward compatibility, just in case.
         payload = loads(unicodify(trans.request.body))
+        run_as = trans.request.headers.get('run-as')
+        if run_as:
+            payload['run_as'] = run_as
     return payload
 
 
diff --git a/lib/galaxy/webapps/galaxy/api/__init__.py b/lib/galaxy/webapps/galaxy/api/__init__.py
index 02e2669397a..8da18edf0f6 100644
--- a/lib/galaxy/webapps/galaxy/api/__init__.py
+++ b/lib/galaxy/webapps/galaxy/api/__init__.py
@@ -3,6 +3,7 @@ This module *does not* contain API routes. It exclusively contains dependencies
 """
 from typing import (
     cast,
+    Generator,
     Optional,
 )
 
@@ -19,17 +20,32 @@ from galaxy import (
     model,
 )
 from galaxy.app import UniverseApplication
-from galaxy.exceptions import AdminRequiredException
+from galaxy.exceptions import (
+    AdminRequiredException,
+    UserCannotRunAsException,
+    UserInvalidRunAsException,
+)
 from galaxy.managers.jobs import JobManager
 from galaxy.managers.session import GalaxySessionManager
 from galaxy.managers.users import UserManager
 from galaxy.model import User
+from galaxy.schema.fields import EncodedDatabaseIdField
+from galaxy.security.idencoding import IdEncodingHelper
 from galaxy.web.framework.decorators import require_admin_message
 from galaxy.work.context import SessionRequestContext
 
 
-def get_app() -> UniverseApplication:
-    return cast(UniverseApplication, galaxy_app.app)
+def get_app() -> Generator[UniverseApplication, None, None]:
+    app = cast(UniverseApplication, galaxy_app.app)
+    try:
+        app.model.set_local_session()
+        yield app
+    finally:
+        app.model.dispose_local_session()
+
+
+def get_id_encoding_helper(app: UniverseApplication = Depends(get_app)) -> IdEncodingHelper:
+    return app.security
 
 
 def get_job_manager(app: UniverseApplication = Depends(get_app)) -> JobManager:
@@ -51,21 +67,36 @@ def get_session_manager(app: UniverseApplication = Depends(get_app)) -> GalaxySe
 
 
 def get_session(session_manager: GalaxySessionManager = Depends(get_session_manager),
-                app: UniverseApplication = Depends(get_app),
+                security: IdEncodingHelper = Depends(get_id_encoding_helper),
                 galaxysession: Optional[str] = Cookie(None)) -> Optional[model.GalaxySession]:
     if galaxysession:
-        session_key = app.security.decode_guid(galaxysession)
+        session_key = security.decode_guid(galaxysession)
         if session_key:
             return session_manager.get_session_from_session_key(session_key)
         # TODO: What should we do if there is no session? Since this is the API, maybe nothing is the right choice?
     return None
 
 
-def get_api_user(user_manager: UserManager = Depends(get_user_manager), key: Optional[str] = Query(None), x_api_key: Optional[str] = Header(None)) -> Optional[User]:
+def get_api_user(
+        security: IdEncodingHelper = Depends(get_id_encoding_helper),
+        user_manager: UserManager = Depends(get_user_manager),
+        key: Optional[str] = Query(None),
+        x_api_key: Optional[str] = Header(None),
+        run_as: Optional[EncodedDatabaseIdField] = Header(None, title='Run as User', description='Admins and ')) -> Optional[User]:
     api_key = key or x_api_key
     if not api_key:
         return None
-    return user_manager.by_api_key(api_key=api_key)
+    user = user_manager.by_api_key(api_key=api_key)
+    if run_as:
+        if user_manager.user_can_do_run_as(user):
+            try:
+                decoded_run_as_id = security.decode_id(run_as)
+            except Exception:
+                raise UserInvalidRunAsException
+            return user_manager.by_id(decoded_run_as_id)
+        else:
+            raise UserCannotRunAsException
+    return user
 
 
 def get_user(galaxy_session: Optional[model.GalaxySession] = Depends(get_session), api_user: Optional[User] = Depends(get_api_user)) -> Optional[User]:
diff --git a/lib/galaxy/webapps/galaxy/api/pages.py b/lib/galaxy/webapps/galaxy/api/pages.py
index 9660b58e208..a50513e080e 100644
--- a/lib/galaxy/webapps/galaxy/api/pages.py
+++ b/lib/galaxy/webapps/galaxy/api/pages.py
@@ -33,8 +33,7 @@ from . import get_app, get_trans
 
 log = logging.getLogger(__name__)
 
-# TODO: This FastAPI router is disabled. Please rename it to `router` when the database session issues are fixed.
-_router = APIRouter(tags=['pages'])
+router = APIRouter(tags=['pages'])
 
 DeletedQueryParam: bool = Query(
     default=False,
@@ -53,11 +52,11 @@ def get_pages_manager(app=Depends(get_app)) -> PagesManager:
     return PagesManager(app)
 
 
-@cbv(_router)
+@cbv(router)
 class FastAPIPages:
     manager: PagesManager = Depends(get_pages_manager)
 
-    @_router.get(
+    @router.get(
         '/api/pages',
         summary="Lists all Pages viewable by the user.",
         response_description="A list with summary page information.",
@@ -70,7 +69,7 @@ class FastAPIPages:
         """Get a list with summary information of all Pages available to the user."""
         return self.manager.index(trans, deleted)
 
-    @_router.post(
+    @router.post(
         '/api/pages',
         summary="Create a page and return summary information.",
         response_description="The page summary information.",
@@ -83,7 +82,7 @@ class FastAPIPages:
         """Get a list with details of all Pages available to the user."""
         return self.manager.create(trans, payload)
 
-    @_router.delete(
+    @router.delete(
         '/api/pages/{id}',
         summary="Marks the specific Page as deleted.",
         status_code=status.HTTP_204_NO_CONTENT,
@@ -96,7 +95,7 @@ class FastAPIPages:
         """Marks the Page with the given ID as deleted."""
         self.manager.delete(trans, id)
 
-    @_router.get(
+    @router.get(
         '/api/pages/{id}',
         summary="Return a page summary and the content of the last revision.",
         response_description="The page summary information.",
@@ -109,7 +108,7 @@ class FastAPIPages:
         """Return summary information about a specific Page and the content of the last revision."""
         return self.manager.show(trans, id)
 
-    @_router.get(
+    @router.get(
         '/api/pages/{id}.pdf',
         summary="Return a PDF document of the last revision of the Page.",
         response_class=StreamingResponse,
@@ -191,6 +190,7 @@ class PagesController(BaseAPIController):
         :returns:   Dictionary with 'success' or 'error' element to indicate the result of the request
         """
         self.manager.delete(trans, id)
+        trans.response.status = 204
 
     @expose_api_anonymous_and_sessionless
     def show(self, trans, id, **kwd):
diff --git a/lib/galaxy/webapps/galaxy/api/tags.py b/lib/galaxy/webapps/galaxy/api/tags.py
index aa36d091389..9af7182d565 100644
--- a/lib/galaxy/webapps/galaxy/api/tags.py
+++ b/lib/galaxy/webapps/galaxy/api/tags.py
@@ -25,19 +25,18 @@ from . import (
 
 log = logging.getLogger(__name__)
 
-# TODO: This FastAPI router is disabled. Please rename it to `router` when the database session issues are fixed.
-_router = APIRouter(tags=['tags'])
+router = APIRouter(tags=['tags'])
 
 
 def get_tags_manager() -> TagsManager:
     return TagsManager()  # TODO: remove/refactor after merging #11180
 
 
-@cbv(_router)
+@cbv(router)
 class FastAPITags:
     manager: TagsManager = Depends(get_tags_manager)
 
-    @_router.put(
+    @router.put(
         '/api/tags',
         summary="Apply a new set of tags to an item.",
         status_code=status.HTTP_204_NO_CONTENT,
diff --git a/lib/galaxy/webapps/galaxy/controllers/admin_toolshed.py b/lib/galaxy/webapps/galaxy/controllers/admin_toolshed.py
index f1636ef7d31..b5f91cb58ad 100644
--- a/lib/galaxy/webapps/galaxy/controllers/admin_toolshed.py
+++ b/lib/galaxy/webapps/galaxy/controllers/admin_toolshed.py
@@ -546,7 +546,7 @@ class AdminToolshed(AdminGalaxy):
         clause_list = []
         for tsr_id in tsr_ids:
             clause_list.append(trans.install_model.ToolShedRepository.table.c.id == tsr_id)
-        query = trans.install_model.context.current.query(trans.install_model.ToolShedRepository).filter(or_(*clause_list))
+        query = trans.install_model.session.query(trans.install_model.ToolShedRepository).filter(or_(*clause_list))
         return trans.fill_template('admin/tool_shed_repository/monitor_repository_installation.mako',
                                    tool_shed_repositories=tool_shed_repositories,
                                    query=query,
@@ -978,7 +978,7 @@ class AdminToolshed(AdminGalaxy):
         clause_list = []
         for tsr_id in tsr_ids:
             clause_list.append(trans.install_model.ToolShedRepository.table.c.id == tsr_id)
-        query = trans.install_model.context.current.query(trans.install_model.ToolShedRepository) \
+        query = trans.install_model.session.query(trans.install_model.ToolShedRepository) \
                                            .filter(or_(*clause_list))
         return trans.fill_template('admin/tool_shed_repository/monitor_repository_installation.mako',
                                    encoded_kwd=encoded_kwd,
diff --git a/lib/galaxy_test/api/test_pages.py b/lib/galaxy_test/api/test_pages.py
index 94d6bca53d6..26f632267d5 100644
--- a/lib/galaxy_test/api/test_pages.py
+++ b/lib/galaxy_test/api/test_pages.py
@@ -16,8 +16,7 @@ class BasePageApiTestCase(ApiTestCase):
     def _create_valid_page_as(self, other_email, slug):
         run_as_user = self._setup_user(other_email)
         page_request = self._test_page_payload(slug=slug)
-        page_request["run_as"] = run_as_user["id"]
-        page_response = self._post("pages", page_request, admin=True, json=True)
+        page_response = self._post("pages", page_request, headers={'run-as': run_as_user["id"]}, admin=True, json=True)
         self._assert_status_code_is(page_response, 200)
         return page_response.json()
 
@@ -138,7 +137,7 @@ steps:
     def test_delete(self):
         response_json = self._create_valid_page_with_slug("testdelete")
         delete_response = delete(self._api_url("pages/%s" % response_json['id'], use_key=True))
-        self._assert_status_code_is(delete_response, 200)
+        self._assert_status_code_is(delete_response, 204)
 
     def test_400_on_delete_invalid_page_id(self):
         delete_response = delete(self._api_url("pages/%s" % self._random_key(), use_key=True))
diff --git a/lib/galaxy_test/base/populators.py b/lib/galaxy_test/base/populators.py
index 52d53561fa3..53de0a7f6c8 100644
--- a/lib/galaxy_test/base/populators.py
+++ b/lib/galaxy_test/base/populators.py
@@ -212,19 +212,19 @@ def _raise_skip_if(check, *args):
 class BasePopulator(metaclass=ABCMeta):
 
     @abstractmethod
-    def _post(self, route, data=None, files=None, admin=False, json: bool = False) -> Response:
+    def _post(self, route, data=None, files=None, headers=None, admin=False, json: bool = False) -> Response:
         """POST data to target Galaxy instance on specified route."""
 
     @abstractmethod
-    def _put(self, route, data=None, admin=False) -> Response:
+    def _put(self, route, data=None, headers=None, admin=False) -> Response:
         """PUT data to target Galaxy instance on specified route."""
 
     @abstractmethod
-    def _get(self, route, data=None, admin=False) -> Response:
+    def _get(self, route, data=None, headers=None, admin=False) -> Response:
         """GET data from target Galaxy instance on specified route."""
 
     @abstractmethod
-    def _delete(self, route, data=None, admin=False) -> Response:
+    def _delete(self, route, data=None, headers=None, admin=False) -> Response:
         """DELETE against target Galaxy instance on specified route."""
 
 
@@ -784,23 +784,23 @@ class GalaxyInteractorHttpMixin:
     def _api_key(self):
         return self.galaxy_interactor.api_key
 
-    def _post(self, route, data=None, files=None, admin=False, json: bool = False) -> Response:
-        return self.galaxy_interactor.post(route, data, files=files, admin=admin, json=json)
+    def _post(self, route, data=None, files=None, headers=None, admin=False, json: bool = False) -> Response:
+        return self.galaxy_interactor.post(route, data, files=files, admin=admin, headers=headers, json=json)
 
-    def _put(self, route, data=None, admin=False):
-        return self.galaxy_interactor.put(route, data, admin=admin)
+    def _put(self, route, data=None, headers=None, admin=False):
+        return self.galaxy_interactor.put(route, data, headers=headers, admin=admin)
 
-    def _get(self, route, data=None, admin=False):
+    def _get(self, route, data=None, headers=None, admin=False):
         if data is None:
             data = {}
 
-        return self.galaxy_interactor.get(route, data=data, admin=admin)
+        return self.galaxy_interactor.get(route, data=data, headers=headers, admin=admin)
 
-    def _delete(self, route, data=None, admin=False):
+    def _delete(self, route, data=None, headers=None, admin=False):
         if data is None:
             data = {}
 
-        return self.galaxy_interactor.delete(route, data=data, admin=admin)
+        return self.galaxy_interactor.delete(route, data=data, headers=headers, admin=admin)
 
 
 class DatasetPopulator(GalaxyInteractorHttpMixin, BaseDatasetPopulator):
@@ -1732,26 +1732,26 @@ class GiHttpMixin:
             data = {}
         return self._gi.make_get_request(self._url(route), data=data)
 
-    def _post(self, route, data=None, files=None, admin=False, json: bool = False) -> Response:
+    def _post(self, route, data=None, files=None, headers=None, admin=False, json: bool = False) -> Response:
         if data is None:
             data = {}
         data = data.copy()
         data['key'] = self._gi.key
-        return requests.post(self._url(route), data=data)
+        return requests.post(self._url(route), data=data, headers=headers)
 
-    def _put(self, route, data=None, admin=False):
+    def _put(self, route, data=None, headers=None, admin=False):
         if data is None:
             data = {}
         data = data.copy()
         data['key'] = self._gi.key
-        return requests.put(self._url(route), data=data)
+        return requests.put(self._url(route), data=data, headers=headers)
 
-    def _delete(self, route, data=None):
+    def _delete(self, route, data=None, headers=None):
         if data is None:
             data = {}
         data = data.copy()
         data['key'] = self._gi.key
-        return requests.delete(self._url(route), data=data)
+        return requests.delete(self._url(route), data=data, headers=headers)
 
     def _url(self, route):
         if route.startswith("/api/"):
diff --git a/lib/galaxy_test/selenium/framework.py b/lib/galaxy_test/selenium/framework.py
index 643524afe06..befca53af76 100644
--- a/lib/galaxy_test/selenium/framework.py
+++ b/lib/galaxy_test/selenium/framework.py
@@ -541,7 +541,7 @@ class SeleniumSessionGetPostMixin:
     def _mixin_admin_api_key(self) -> str:
         return getattr(self, "admin_api_key", get_admin_api_key())
 
-    def _get(self, route, data=None, admin=False) -> Response:
+    def _get(self, route, data=None, headers=None, admin=False) -> Response:
         data = data or {}
         full_url = self.selenium_context.build_url("api/" + route, for_selenium=False)
         cookies = None
@@ -549,10 +549,10 @@ class SeleniumSessionGetPostMixin:
             full_url = f"{full_url}?key={self._mixin_admin_api_key}"
         else:
             cookies = self.selenium_context.selenium_to_requests_cookies()
-        response = requests.get(full_url, params=data, cookies=cookies)
+        response = requests.get(full_url, params=data, cookies=cookies, headers=headers)
         return response
 
-    def _post(self, route, data=None, files=None, admin=False, json: bool = False) -> Response:
+    def _post(self, route, data=None, files=None, headers=None, admin=False, json: bool = False) -> Response:
         full_url = self.selenium_context.build_url("api/" + route, for_selenium=False)
         if data is None:
             data = {}
@@ -567,10 +567,10 @@ class SeleniumSessionGetPostMixin:
             full_url = f"{full_url}?key={self._mixin_admin_api_key}"
         else:
             cookies = self.selenium_context.selenium_to_requests_cookies()
-        response = requests.post(full_url, data=data, cookies=cookies, files=files)
+        response = requests.post(full_url, data=data, cookies=cookies, files=files, headers=headers)
         return response
 
-    def _delete(self, route, data=None, admin=False) -> Response:
+    def _delete(self, route, data=None, headers=None, admin=False) -> Response:
         data = data or {}
         full_url = self.selenium_context.build_url("api/" + route, for_selenium=False)
         cookies = None
@@ -578,10 +578,10 @@ class SeleniumSessionGetPostMixin:
             full_url = f"{full_url}?key={self._mixin_admin_api_key}"
         else:
             cookies = self.selenium_context.selenium_to_requests_cookies()
-        response = requests.delete(full_url, data=data, cookies=cookies)
+        response = requests.delete(full_url, data=data, cookies=cookies, headers=headers)
         return response
 
-    def _put(self, route, data=None, admin=False) -> Response:
+    def _put(self, route, data=None, headers=None, admin=False) -> Response:
         data = data or {}
         full_url = self.selenium_context.build_url("api/" + route, for_selenium=False)
         cookies = None
@@ -589,7 +589,7 @@ class SeleniumSessionGetPostMixin:
             full_url = f"{full_url}?key={self._mixin_admin_api_key}"
         else:
             cookies = self.selenium_context.selenium_to_requests_cookies()
-        response = requests.put(full_url, data=data, cookies=cookies)
+        response = requests.put(full_url, data=data, cookies=cookies, headers=headers)
         return response
 
 
diff --git a/lib/tool_shed/repository_registry.py b/lib/tool_shed/repository_registry.py
index a40787cf67d..304a03ecf48 100644
--- a/lib/tool_shed/repository_registry.py
+++ b/lib/tool_shed/repository_registry.py
@@ -347,7 +347,7 @@ class Registry:
 
     @property
     def sa_session(self):
-        return self.app.model.context.current
+        return self.app.model.session
 
     def unload_certified_level_one_repository_and_suite_tuple(self, repository):
         # The received repository has been determined to be level one certified.
diff --git a/lib/tool_shed/util/commit_util.py b/lib/tool_shed/util/commit_util.py
index 2d5d511a3c7..10289b0788d 100644
--- a/lib/tool_shed/util/commit_util.py
+++ b/lib/tool_shed/util/commit_util.py
@@ -67,7 +67,7 @@ def check_file_contents_for_email_alerts(app):
     See if any admin users have chosen to receive email alerts when a repository is updated.
     If so, the file contents of the update must be checked for inappropriate content.
     """
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     admin_users = app.config.get("admin_users", "").split(",")
     for repository in sa_session.query(app.model.Repository) \
                                 .filter(app.model.Repository.table.c.email_alerts != null()):
diff --git a/lib/tool_shed/util/metadata_util.py b/lib/tool_shed/util/metadata_util.py
index 4bbfa14c44c..6719ee24d46 100644
--- a/lib/tool_shed/util/metadata_util.py
+++ b/lib/tool_shed/util/metadata_util.py
@@ -19,7 +19,7 @@ def get_all_dependencies(app, metadata_entry, processed_dependency_links=None):
     encoder = app.security.encode_id
     value_mapper = {'repository_id': encoder, 'id': encoder, 'user_id': encoder}
     metadata = metadata_entry.to_dict(value_mapper=value_mapper, view='element')
-    db = app.model.context.current
+    db = app.model.session
     returned_dependencies = []
     required_metadata = get_dependencies_for_metadata_revision(app, metadata)
     if required_metadata is None:
@@ -102,7 +102,7 @@ def get_latest_downloadable_changeset_revision(app, repository):
 
 def get_latest_repository_metadata(app, decoded_repository_id, downloadable=False):
     """Get last metadata defined for a specified repository from the database."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     repository = sa_session.query(app.model.Repository).get(decoded_repository_id)
     if downloadable:
         changeset_revision = get_latest_downloadable_changeset_revision(app, repository)
@@ -117,7 +117,7 @@ def get_metadata_revisions(app, repository, sort_revisions=True, reverse=False,
     """
     Return a list of changesets for the provided repository.
     """
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     if downloadable:
         metadata_revisions = repository.downloadable_revisions
     else:
@@ -225,7 +225,7 @@ def get_repository_metadata_by_changeset_revision(app, id, changeset_revision):
     # Make sure there are no duplicate records, and return the single unique record for the changeset_revision.
     # Duplicate records were somehow created in the past.  The cause of this issue has been resolved, but we'll
     # leave this method as is for a while longer to ensure all duplicate records are removed.
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     all_metadata_records = sa_session.query(app.model.RepositoryMetadata) \
                                      .filter(and_(app.model.RepositoryMetadata.table.c.repository_id == app.security.decode_id(id),
                                                   app.model.RepositoryMetadata.table.c.changeset_revision == changeset_revision)) \
@@ -243,7 +243,7 @@ def get_repository_metadata_by_changeset_revision(app, id, changeset_revision):
 
 def get_repository_metadata_by_id(app, id):
     """Get repository metadata from the database"""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.RepositoryMetadata).get(app.security.decode_id(id))
 
 
diff --git a/lib/tool_shed/util/repository_util.py b/lib/tool_shed/util/repository_util.py
index 504de162c50..6a569b56357 100644
--- a/lib/tool_shed/util/repository_util.py
+++ b/lib/tool_shed/util/repository_util.py
@@ -130,7 +130,7 @@ def create_repository_admin_role(app, repository):
     Create a new role with name-spaced name based on the repository name and its owner's public user
     name.  This will ensure that the tole name is unique.
     """
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     name = get_repository_admin_role_name(str(repository.name), str(repository.user.username))
     description = 'A user or group member with this role can administer this repository.'
     role = app.model.Role(name=name, description=description, type=app.model.Role.types.SYSTEM)
@@ -148,7 +148,7 @@ def create_repository_admin_role(app, repository):
 def create_repository(app, name, type, description, long_description, user_id, category_ids=None, remote_repository_url=None, homepage_url=None):
     """Create a new ToolShed repository"""
     category_ids = category_ids or []
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     # Add the repository record to the database.
     repository = app.model.Repository(name=name,
                                       type=type,
@@ -263,7 +263,7 @@ def get_repo_info_dict(app, user, repository_id, changeset_revision):
 
 
 def get_repositories_by_category(app, category_id, installable=False, sort_order='asc', sort_key='name', page=None, per_page=25):
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     query = sa_session.query(app.model.Repository) \
                       .join(app.model.RepositoryCategoryAssociation, app.model.Repository.id == app.model.RepositoryCategoryAssociation.repository_id) \
                       .join(app.model.User, app.model.User.id == app.model.Repository.user_id) \
@@ -349,7 +349,7 @@ def get_tool_shed_repository_status_label(app, tool_shed_repository=None, name=N
 
 
 def handle_role_associations(app, role, repository, **kwd):
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     message = escape(kwd.get('message', ''))
     status = kwd.get('status', 'done')
     repository_owner = repository.user
@@ -415,7 +415,7 @@ def update_repository(app, trans, id, **kwds):
     """Update an existing ToolShed repository"""
     message = None
     flush_needed = False
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     repository = sa_session.query(app.model.Repository).get(app.security.decode_id(id))
     if repository is None:
         return None, "Unknown repository ID"
diff --git a/lib/tool_shed/util/review_util.py b/lib/tool_shed/util/review_util.py
index 0e1f5980ce6..fe5c5088518 100644
--- a/lib/tool_shed/util/review_util.py
+++ b/lib/tool_shed/util/review_util.py
@@ -32,19 +32,19 @@ def changeset_revision_reviewed_by_user(user, repository, changeset_revision):
 
 def get_component(app, id):
     """Get a component from the database."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.Component).get(app.security.decode_id(id))
 
 
 def get_component_review(app, id):
     """Get a component_review from the database"""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.ComponentReview).get(app.security.decode_id(id))
 
 
 def get_component_by_name(app, name):
     """Get a component from the database via a name."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.Component) \
                      .filter(app.model.Component.table.c.name == name) \
                      .first()
@@ -52,7 +52,7 @@ def get_component_by_name(app, name):
 
 def get_component_review_by_repository_review_id_component_id(app, repository_review_id, component_id):
     """Get a component_review from the database via repository_review_id and component_id."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.ComponentReview) \
                      .filter(and_(app.model.ComponentReview.table.c.repository_review_id == app.security.decode_id(repository_review_id),
                                   app.model.ComponentReview.table.c.component_id == app.security.decode_id(component_id))) \
@@ -60,7 +60,7 @@ def get_component_review_by_repository_review_id_component_id(app, repository_re
 
 
 def get_components(app):
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.Component) \
                      .order_by(app.model.Component.name) \
                      .all()
@@ -90,7 +90,7 @@ def get_previous_repository_reviews(app, repository, changeset_revision):
 
 def get_review(app, id):
     """Get a repository_review from the database via id."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.RepositoryReview).get(app.security.decode_id(id))
 
 
@@ -99,7 +99,7 @@ def get_review_by_repository_id_changeset_revision_user_id(app, repository_id, c
     Get a repository_review from the database via repository id, changeset_revision
     and user_id.
     """
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.RepositoryReview) \
                      .filter(and_(app.model.RepositoryReview.repository_id == app.security.decode_id(repository_id),
                                   app.model.RepositoryReview.changeset_revision == changeset_revision,
@@ -109,7 +109,7 @@ def get_review_by_repository_id_changeset_revision_user_id(app, repository_id, c
 
 def get_reviews_by_repository_id_changeset_revision(app, repository_id, changeset_revision):
     """Get all repository_reviews from the database via repository id and changeset_revision."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.RepositoryReview) \
                      .filter(and_(app.model.RepositoryReview.repository_id == app.security.decode_id(repository_id),
                                   app.model.RepositoryReview.changeset_revision == changeset_revision)) \
diff --git a/lib/tool_shed/util/search_util.py b/lib/tool_shed/util/search_util.py
index 7cbc2996de4..5a9eef5ca54 100644
--- a/lib/tool_shed/util/search_util.py
+++ b/lib/tool_shed/util/search_util.py
@@ -91,7 +91,7 @@ def search_names_versions(tool_dict, exact_matches_checked, match_tuples, reposi
 
 def search_repository_metadata(app, exact_matches_checked, tool_ids='', tool_names='', tool_versions='',
                                workflow_names='', all_workflows=False):
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     match_tuples = []
     ok = True
     if tool_ids or tool_names or tool_versions:
diff --git a/lib/tool_shed/util/shed_index.py b/lib/tool_shed/util/shed_index.py
index 57ebcf3c7ca..f9e5a3d2d6f 100644
--- a/lib/tool_shed/util/shed_index.py
+++ b/lib/tool_shed/util/shed_index.py
@@ -38,7 +38,7 @@ def build_index(whoosh_index_dir, file_path, hgweb_config_dir, dburi, **kwargs):
     Returns a tuple with number of repos and tools that were indexed.
     """
     model = ts_mapping.init(file_path, dburi, engine_options={}, create_tables=False)
-    sa_session = model.context.current
+    sa_session = model.session
     repo_index, tool_index = _get_or_create_index(whoosh_index_dir)
 
     repo_index_writer = AsyncWriter(repo_index)
diff --git a/lib/tool_shed/util/shed_util_common.py b/lib/tool_shed/util/shed_util_common.py
index 9f850de157e..c450202db7e 100644
--- a/lib/tool_shed/util/shed_util_common.py
+++ b/lib/tool_shed/util/shed_util_common.py
@@ -97,7 +97,7 @@ This message was sent from the Galaxy Tool Shed instance hosted on the server
 
 
 def count_repositories_in_category(app, category_id):
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.RepositoryCategoryAssociation) \
                      .filter(app.model.RepositoryCategoryAssociation.table.c.category_id == app.security.decode_id(category_id)) \
                      .count()
@@ -105,7 +105,7 @@ def count_repositories_in_category(app, category_id):
 
 def get_categories(app):
     """Get all categories from the database."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.Category) \
                      .filter(app.model.Category.table.c.deleted == false()) \
                      .order_by(app.model.Category.table.c.name) \
@@ -114,13 +114,13 @@ def get_categories(app):
 
 def get_category(app, id):
     """Get a category from the database."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.Category).get(app.security.decode_id(id))
 
 
 def get_category_by_name(app, name):
     """Get a category from the database via name."""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     try:
         return sa_session.query(app.model.Category).filter_by(name=name).one()
     except sqlalchemy.orm.exc.NoResultFound:
@@ -180,7 +180,7 @@ def get_requirements_from_repository(repository):
 
 def get_repository_categories(app, id):
     """Get categories of a repository on the tool shed side from the database via id"""
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     return sa_session.query(app.model.RepositoryCategoryAssociation) \
         .filter(app.model.RepositoryCategoryAssociation.table.c.repository_id == app.security.decode_id(id))
 
@@ -326,7 +326,7 @@ def handle_email_alerts(app, host, repository, content_alert_str='', new_repo_al
        that was included in the change set.
 
     """
-    sa_session = app.model.context.current
+    sa_session = app.model.session
     repo = repository.hg_repo
     sharable_link = repository_util.generate_sharable_link_for_repository_in_tool_shed(repository, changeset_revision=None)
     smtp_server = app.config.smtp_server
diff --git a/pyproject.toml b/pyproject.toml
index 961a96d2289..9a497ec3db0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -15,6 +15,8 @@ url = "https://wheels.galaxyproject.org/simple"
 
 [tool.poetry.dependencies]
 aiofiles = "*"
+async-generator = {version = "*", python = "~3.6"}
+async-exit-stack = {version = "*", python = "~3.6"}
 Babel = "*"
 bdbag = "*"
 Beaker = "1.11.0"
diff --git a/test/integration/test_page_revision_json_encoding.py b/test/integration/test_page_revision_json_encoding.py
index b1952ef0a58..6ac0667fb9a 100644
--- a/test/integration/test_page_revision_json_encoding.py
+++ b/test/integration/test_page_revision_json_encoding.py
@@ -26,7 +26,7 @@ class PageJsonEncodingIntegrationTestCase(integration_util.IntegrationTestCase):
             title="MY PAGE",
             content='''<p>Page!<div class="embedded-item" id="History-%s"></div></p>''' % self.history_id,
         )
-        page_response = self._post("pages", request)
+        page_response = self._post("pages", request, json=True)
         api_asserts.assert_status_code_is_ok(page_response)
         sa_session = self._app.model.context
         page_revision = sa_session.query(model.PageRevision).filter_by(content_format="html").all()[0]
@@ -50,7 +50,7 @@ history_dataset_display(history_dataset_id=%s)
 ```''' % dataset["id"],
             content_format="markdown",
         )
-        page_response = self._post("pages", request)
+        page_response = self._post("pages", request, json=True)
         api_asserts.assert_status_code_is_ok(page_response)
         sa_session = self._app.model.context
         page_revision = sa_session.query(model.PageRevision).filter_by(content_format="markdown").all()[0]
diff --git a/test/unit/jobs/test_job_wrapper.py b/test/unit/jobs/test_job_wrapper.py
index b7f3560c89a..c5e3b5e6e20 100644
--- a/test/unit/jobs/test_job_wrapper.py
+++ b/test/unit/jobs/test_job_wrapper.py
@@ -31,7 +31,7 @@ class BaseWrapperTestCase(UsesApp):
         job.user = User()
         job.object_store_id = "foo"
         self.model_objects = {Job: {345: job}}
-        self.app.model.context = MockContext(self.model_objects)
+        self.app.model._session = MockContext(self.model_objects)
 
         self.app.toolbox = MockToolbox(MockTool(self))
         self.working_directory = os.path.join(self.test_directory, "working")
diff --git a/tools/cloud/send.xml b/tools/cloud/send.xml
index c5dd5c70fc3..62e5ccffd94 100644
--- a/tools/cloud/send.xml
+++ b/tools/cloud/send.xml
@@ -8,8 +8,8 @@
     -->
     <command><![CDATA[
         #try
-            #set $authz_record=$__app__.authnz_manager.try_get_authz_config($__app__.obj.model.context.current, int($__user_id__), $__app__.security.decode_id($authz_id.__str__()))
-            #set $credentials_file = $__app__.authnz_manager.get_cloud_access_credentials_in_file($__app__.config.new_file_path, $authz_record, $__app__.obj.model.context.current, int($__user_id__))
+            #set $authz_record=$__app__.authnz_manager.try_get_authz_config($__app__.obj.model.session, int($__user_id__), $__app__.security.decode_id($authz_id.__str__()))
+            #set $credentials_file = $__app__.authnz_manager.get_cloud_access_credentials_in_file($__app__.config.new_file_path, $authz_record, $__app__.obj.model.session, int($__user_id__))
         #except Exception as e:
             echo '$e' >&2
         #else