diff --git a/tests/unit/test_api.py b/tests/unit/test_api.py
index 454008f..d4d2233 100644
--- a/tests/unit/test_api.py
+++ b/tests/unit/test_api.py
@@ -8,9 +8,11 @@ All I/O is stubbed so no container is created.
 from __future__ import annotations
 
 import unittest
+from pathlib import Path
 from unittest.mock import MagicMock, patch
 
 from bot_bottle import BottleError, destroy, freeze, resume_headless, start_headless
+from bot_bottle.log import Die
 
 
 # ---------------------------------------------------------------------------
@@ -104,6 +106,21 @@ class TestStartHeadless(unittest.TestCase):
                 start_headless("implementer", prompt="Do it")
         self._launch.assert_not_called()
 
+    def test_manifest_error_in_resolve_raises_bottle_error(self):
+        from bot_bottle.manifest import ManifestError
+        patch(
+            "bot_bottle.api.ManifestIndex.resolve", side_effect=ManifestError("bad")
+        ).start()
+        with self.assertRaises(BottleError):
+            start_headless("implementer", prompt="Do it")
+        self._launch.assert_not_called()
+
+    def test_die_from_launch_bottle_raises_bottle_error(self):
+        self._launch.side_effect = Die(3, "backend exploded")
+        with self.assertRaises(BottleError) as ctx:
+            start_headless("implementer", prompt="Do it")
+        self.assertEqual(3, ctx.exception.exit_code)
+
     def test_backend_name_forwarded(self):
         start_headless("implementer", prompt="Do it", backend_name="docker")
         self.assertEqual("docker", self._launch.call_args[1]["backend_name"])
@@ -164,6 +181,21 @@ class TestResumeHeadless(unittest.TestCase):
             resume_headless("implementer-abc12", prompt="Prompt")
         self.assertEqual(2, ctx.exception.exit_code)
 
+    def test_manifest_error_in_resolve_raises_bottle_error(self):
+        from bot_bottle.manifest import ManifestError
+        patch(
+            "bot_bottle.api.ManifestIndex.resolve", side_effect=ManifestError("bad")
+        ).start()
+        with self.assertRaises(BottleError):
+            resume_headless("implementer-abc12", prompt="Prompt")
+        self._launch.assert_not_called()
+
+    def test_die_from_launch_bottle_raises_bottle_error(self):
+        self._launch.side_effect = Die(5, "resume failed")
+        with self.assertRaises(BottleError) as ctx:
+            resume_headless("implementer-abc12", prompt="Prompt")
+        self.assertEqual(5, ctx.exception.exit_code)
+
     def test_backend_from_metadata_when_not_supplied(self):
         resume_headless("implementer-abc12", prompt="Prompt")
         self.assertEqual("docker", self._launch.call_args[1]["backend_name"])
@@ -207,6 +239,12 @@ class TestFreeze(unittest.TestCase):
         with self.assertRaises(BottleError):
             freeze("implementer-abc12")
 
+    def test_die_from_freezer_raises_bottle_error(self):
+        self._freezer.commit_slug.side_effect = Die(2, "commit exploded")
+        with self.assertRaises(BottleError) as ctx:
+            freeze("implementer-abc12")
+        self.assertEqual(2, ctx.exception.exit_code)
+
 
 # ---------------------------------------------------------------------------
 # destroy
@@ -239,6 +277,17 @@ class TestDestroy(unittest.TestCase):
         ds.assert_called_once_with("implementer-abc12")
         self._dd.assert_not_called()
 
+    def test_other_backend_skips_docker_and_smolmachines(self):
+        patch(
+            "bot_bottle.api.read_metadata",
+            return_value=_metadata(backend="macos-container"),
+        ).start()
+        ds = patch("bot_bottle.api._destroy_smolmachines").start()
+        destroy("implementer-abc12")
+        self._dd.assert_not_called()
+        ds.assert_not_called()
+        self._cleanup.assert_called_once_with("implementer-abc12")
+
     def test_missing_metadata_defaults_to_docker(self):
         patch("bot_bottle.api.read_metadata", return_value=None).start()
         destroy("no-state-abc12")
@@ -250,6 +299,81 @@ class TestDestroy(unittest.TestCase):
         ds.assert_called_once_with("implementer-abc12")
         self._dd.assert_not_called()
 
+    def test_die_from_backend_raises_bottle_error(self):
+        self._dd.side_effect = Die(1, "compose failed")
+        with self.assertRaises(BottleError):
+            destroy("implementer-abc12")
+
+
+# ---------------------------------------------------------------------------
+# _destroy_docker (helper)
+# ---------------------------------------------------------------------------
+
+
+class TestDestroyDocker(unittest.TestCase):
+    def setUp(self) -> None:
+        self._compose_down = patch(
+            "bot_bottle.backend.docker.compose.compose_down"
+        ).start()
+        self._compose_project_name = patch(
+            "bot_bottle.backend.docker.compose.compose_project_name",
+            return_value="bb-proj",
+        ).start()
+        self._state_dir = patch(
+            "bot_bottle.bottle_state.bottle_state_dir",
+            return_value=Path("/fake/state"),
+        ).start()
+        self.addCleanup(patch.stopall)
+
+    def _run(self, exists: bool) -> None:
+        fake_file = MagicMock()
+        fake_file.exists.return_value = exists
+        with patch(
+            "bot_bottle.backend.docker.compose.compose_file_path",
+            return_value=fake_file,
+        ):
+            from bot_bottle.api import _destroy_docker
+            _destroy_docker("slug-1")
+
+    def test_calls_compose_down_when_file_exists(self) -> None:
+        self._run(exists=True)
+        self._compose_down.assert_called_once()
+
+    def test_noop_when_compose_file_absent(self) -> None:
+        self._run(exists=False)
+        self._compose_down.assert_not_called()
+
+
+# ---------------------------------------------------------------------------
+# _destroy_smolmachines (helper)
+# ---------------------------------------------------------------------------
+
+
+class TestDestroySmolmachines(unittest.TestCase):
+    def setUp(self) -> None:
+        self._run = patch("subprocess.run").start()
+        self._run.return_value = MagicMock(returncode=0, stderr="", stdout="")
+        self.addCleanup(patch.stopall)
+
+    def _call(self) -> None:
+        from bot_bottle.api import _destroy_smolmachines
+        _destroy_smolmachines("slug-7")
+
+    def test_issues_stop_then_delete(self) -> None:
+        self._call()
+        self.assertEqual(2, self._run.call_count)
+        first_argv = self._run.call_args_list[0][0][0]
+        self.assertIn("stop", first_argv)
+        second_argv = self._run.call_args_list[1][0][0]
+        self.assertIn("delete", second_argv)
+
+    def test_nonzero_delete_does_not_raise(self) -> None:
+        self._run.side_effect = [
+            MagicMock(returncode=0),
+            MagicMock(returncode=1, stderr="not found", stdout=""),
+        ]
+        self._call()  # must not raise
+
 
 # ---------------------------------------------------------------------------
 # public surface exported from bot_bottle.__init__