diff --git a/osbuild/__init__.py b/osbuild/__init__.py
index 19b2934f..e6d55296 100644
--- a/osbuild/__init__.py
+++ b/osbuild/__init__.py
@@ -8,11 +8,10 @@ The utility module `osbuild.util` provides access to common functionality
 independent of osbuild but used across the osbuild codebase.
 """
 
-from .pipeline import Assembler, Manifest, Pipeline, Stage
+from .pipeline import Manifest, Pipeline, Stage
 
 
 __all__ = [
-    "Assembler",
     "Manifest",
     "Pipeline",
     "Stage",
diff --git a/osbuild/monitor.py b/osbuild/monitor.py
index f8da0d07..f7e538a1 100644
--- a/osbuild/monitor.py
+++ b/osbuild/monitor.py
@@ -66,7 +66,7 @@ class BaseMonitor(abc.ABC):
     def stage(self, stage: osbuild.Stage):
         """Called when a stage is being built"""
 
-    def assembler(self, assembler: osbuild.Assembler):
+    def assembler(self, assembler: osbuild.Stage):
         """Called when an assembler is being built"""
 
     def result(self, result: osbuild.pipeline.BuildResult):
diff --git a/osbuild/pipeline.py b/osbuild/pipeline.py
index 314d0ad8..4973d17d 100644
--- a/osbuild/pipeline.py
+++ b/osbuild/pipeline.py
@@ -110,57 +110,6 @@ class Stage:
         return BuildResult(self, r.returncode, r.output, api.metadata, api.error)
 
 
-class Assembler:
-    def __init__(self, name, build, base, options):
-        self.name = name
-        self.build = build
-        self.base = base
-        self.options = options
-        self.checkpoint = False
-
-    @property
-    def id(self):
-        m = hashlib.sha256()
-        m.update(json.dumps(self.name, sort_keys=True).encode())
-        m.update(json.dumps(self.build, sort_keys=True).encode())
-        m.update(json.dumps(self.base, sort_keys=True).encode())
-        m.update(json.dumps(self.options, sort_keys=True).encode())
-        return m.hexdigest()
-
-    def run(self, tree, runner, build_tree, monitor, libdir, output_dir, var="/var/tmp"):
-        with buildroot.BuildRoot(build_tree, runner, libdir, var=var) as build_root:
-
-            args = {
-                "tree": "/run/osbuild/tree",
-                "options": self.options,
-                "meta": {
-                    "id": self.id
-                }
-            }
-
-            binds = []
-
-            output_dir = os.fspath(output_dir)
-            os.makedirs(output_dir, exist_ok=True)
-            binds.append(f"{output_dir}:/run/osbuild/output")
-            args["output_dir"] = "/run/osbuild/output"
-
-            ro_binds = [os.fspath(tree) + ":/run/osbuild/tree"]
-
-            api = API(args, monitor)
-            build_root.register_api(api)
-
-            rls = remoteloop.LoopServer()
-            build_root.register_api(rls)
-
-            r = build_root.run([f"/run/osbuild/lib/assemblers/{self.name}"],
-                               monitor,
-                               binds=binds,
-                               readonly_binds=ro_binds)
-
-        return BuildResult(self, r.returncode, r.output, api.metadata, api.error)
-
-
 class Pipeline:
     def __init__(self, runner=None, build=None):
         self.build = build
diff --git a/test/mod/test_monitor.py b/test/mod/test_monitor.py
index 5f3e93c7..cb549769 100644
--- a/test/mod/test_monitor.py
+++ b/test/mod/test_monitor.py
@@ -38,7 +38,7 @@ class TapeMonitor(osbuild.monitor.BaseMonitor):
         self.counter["stages"] += 1
         self.stages.add(stage.id)
 
-    def assembler(self, assembler: osbuild.Assembler):
+    def assembler(self, assembler: osbuild.Stage):
         self.counter["assembler"] += 1
         self.asm = assembler.id