diff --git a/src/agent_env/providers/sandbox_providers/e2b/provider.py b/src/agent_env/providers/sandbox_providers/e2b/provider.py
index 050d74a4..c5c11b4c 100644
--- a/src/agent_env/providers/sandbox_providers/e2b/provider.py
+++ b/src/agent_env/providers/sandbox_providers/e2b/provider.py
@@ -381,3 +381,7 @@ async def get_sandbox(self, sandbox_id: str) -> E2BSandbox:
             )
             sandbox.network_policy = None
         return sandbox
+
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        if not await self._get_sandbox_cls().kill(sandbox_id, api_key=self._api_key):
+            logger.info("E2B sandbox %s was already absent during terminate", sandbox_id)
diff --git a/src/agent_env/providers/sandbox_providers/modal_sandbox.py b/src/agent_env/providers/sandbox_providers/modal_sandbox.py
index cc647e8d..cb09bd87 100644
--- a/src/agent_env/providers/sandbox_providers/modal_sandbox.py
+++ b/src/agent_env/providers/sandbox_providers/modal_sandbox.py
@@ -90,6 +90,14 @@ def _tunnel_url(t) -> str:
     return f"https://{t.host}" + (f":{t.port}" if t.port != 443 else "")
 
 
+async def _terminate_by_id(client, sandbox_id: str) -> None:
+    try:
+        sb = await modal.Sandbox.from_id.aio(sandbox_id, client=client)
+        await sb.terminate.aio()
+    except modal.exception.NotFoundError:
+        logger.info("Modal sandbox %s was already gone at terminate", sandbox_id)
+
+
 def _modal_network_kwargs(policy: NetworkPolicy) -> dict:
     """``policy`` as Modal ``_experimental_create`` kwargs.
 
@@ -480,6 +488,9 @@ async def get_sandbox(self, sandbox_id: str) -> Sandbox:
         i6pn_address = await _resolve_i6pn_address(sb)
         return self._sandbox_cls(sb, tunnel_urls, i6pn_address=i6pn_address)
 
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        await _terminate_by_id(await self._get_client(), sandbox_id)
+
     async def _registry_image(self, image_name: str) -> modal.Image:
         """``image_name`` pulled from its registry, with the image store's credentials for it, if any."""
         image_store = get_config().get_image_store_at(image_name)
diff --git a/src/agent_env/providers/sandbox_providers/modal_vm_sandbox.py b/src/agent_env/providers/sandbox_providers/modal_vm_sandbox.py
index d615d39a..0cec9499 100644
--- a/src/agent_env/providers/sandbox_providers/modal_vm_sandbox.py
+++ b/src/agent_env/providers/sandbox_providers/modal_vm_sandbox.py
@@ -32,6 +32,7 @@
     _attribution_tags,
     _log_sandbox_started,
     _resolve_app_base_name,
+    _terminate_by_id,
     _tunnel_url,
     _modal_network_kwargs,
 )
@@ -412,6 +413,9 @@ async def get_sandbox(self, sandbox_id: str) -> ModalVmSandbox:
         # dockerd is already running on a live sandbox; do not re-run setup here.
         return ModalVmSandbox(sb, tunnel_urls)
 
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        await _terminate_by_id(await self._get_client(), sandbox_id)
+
 
 # ── Object downloads (internal) ────────────────────────────────────────────────────
 # Object downloads run as one aria2c per object: a pool of HTTP range connections with small pieces,
diff --git a/src/agent_env/providers/sandbox_providers/sail_vm/provider.py b/src/agent_env/providers/sandbox_providers/sail_vm/provider.py
index 76170d72..24dfd5e1 100644
--- a/src/agent_env/providers/sandbox_providers/sail_vm/provider.py
+++ b/src/agent_env/providers/sandbox_providers/sail_vm/provider.py
@@ -429,3 +429,14 @@ async def get_sandbox(self, sandbox_id: str) -> SailVmSandbox:
                 sandbox_id, applied,
             )
         return sandbox
+
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        """Through the handle: terminating also deletes the Sailbox's model-key policy, which only its applied
+        policy names."""
+        sdk, _ = await self._connect()
+        try:
+            sandbox = await self.get_sandbox(sandbox_id)
+        except sdk.NotFoundError:
+            logger.info("Sailbox %s was already gone at terminate", sandbox_id)
+            return
+        await sandbox.terminate()
diff --git a/src/agent_env/providers/sandbox_providers/sandbox_provider.py b/src/agent_env/providers/sandbox_providers/sandbox_provider.py
index 522886ae..314de40b 100644
--- a/src/agent_env/providers/sandbox_providers/sandbox_provider.py
+++ b/src/agent_env/providers/sandbox_providers/sandbox_provider.py
@@ -162,6 +162,11 @@ def _container_args(self, sandbox: VmSandbox, *, image_name: str, port: int, env
     async def get_sandbox(self, sandbox_id: str) -> Sandbox:
         raise NotImplementedError(f"{type(self).__name__} does not support get_sandbox")
 
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        """Terminate a sandbox this provider made, by id; one that has already finished or is gone is terminated.
+        A backend that can terminate without a live handle overrides this, so teardown doesn't need one."""
+        await (await self.get_sandbox(sandbox_id)).terminate()
+
     async def close(self) -> None:
         pass
 
diff --git a/src/agent_env/providers/sandbox_providers/smol_vm/provider.py b/src/agent_env/providers/sandbox_providers/smol_vm/provider.py
index 05f9c8f9..6c2c026d 100644
--- a/src/agent_env/providers/sandbox_providers/smol_vm/provider.py
+++ b/src/agent_env/providers/sandbox_providers/smol_vm/provider.py
@@ -183,6 +183,16 @@ async def get_sandbox(self, sandbox_id: str) -> SmolVmSandbox:
         sandbox.network_policy = self.effective_network_policy(None)
         return sandbox
 
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        """Connecting starts a stopped machine, and the SDK deletes only a connected one, so a listed machine is
+        connected first; one not listed is gone."""
+        conn = ConnectOptions(target="local", wait_for_ports=False)
+        if sandbox_id not in {machine.name for machine in await asyncio.to_thread(Machine.list, conn)}:
+            logger.info("SmolVM machine %s was already gone at terminate", sandbox_id)
+            return
+        machine = await asyncio.to_thread(Machine.connect, sandbox_id, conn)
+        await asyncio.to_thread(machine.delete)
+
     async def _configure_host_access(self, sandbox: SmolVmSandbox) -> None:
         code, stdout, stderr = await sandbox.exec_with_output("getent", "ahostsv4", "host.smolvm.internal")
         if code or not stdout.strip():
diff --git a/src/agent_env/providers/sandbox_providers/tenki/provider.py b/src/agent_env/providers/sandbox_providers/tenki/provider.py
index bf00a79d..a52d5ce0 100644
--- a/src/agent_env/providers/sandbox_providers/tenki/provider.py
+++ b/src/agent_env/providers/sandbox_providers/tenki/provider.py
@@ -18,13 +18,13 @@
 from typing import Any, ClassVar, Self
 from urllib.parse import urlparse
 
-from tenki import AsyncClient
+from tenki import AsyncClient, SessionNotFoundError
 
 from agent_env.attribution import Attribution
 from agent_env.config.errors import ConfigError
 from agent_env.providers.sandbox_providers.sandbox import NetworkPolicy, NetworkPolicyUnsupportedError
 from agent_env.providers.sandbox_providers.sandbox_provider import SandboxProvider, apply_default_attribution
-from agent_env.providers.sandbox_providers.tenki.sandbox import ENDED_STATES, TenkiSandbox, policy_from_info
+from agent_env.providers.sandbox_providers.tenki.sandbox import ENDED_STATES, TenkiSandbox, close_session, policy_from_info
 
 logger = logging.getLogger(__name__)
 
@@ -413,3 +413,11 @@ async def get_sandbox(self, sandbox_id: str) -> TenkiSandbox:
             network_policy=policy_from_info(info),
             command_timeout=_remaining_lifetime(info.timeout_at),
         )
+
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        try:
+            session = await self._client().get(sandbox_id)
+        except SessionNotFoundError:
+            logger.info("Tenki session %s was already gone at terminate", sandbox_id)
+            return
+        await close_session(session)
diff --git a/src/agent_env/providers/sandbox_providers/tenki/sandbox.py b/src/agent_env/providers/sandbox_providers/tenki/sandbox.py
index 841997b0..5031cfb5 100644
--- a/src/agent_env/providers/sandbox_providers/tenki/sandbox.py
+++ b/src/agent_env/providers/sandbox_providers/tenki/sandbox.py
@@ -174,30 +174,13 @@ def __init__(
         self.network_policy = network_policy
 
     async def terminate(self) -> None:
-        """Terminate the VM. One another handle already terminated, while this handle's cached state still says
-        running, is not an error."""
-        try:
-            await self._session.close_if_open()
-        except SessionNotFoundError:
-            logger.info("Tenki session %s was already gone at terminate", self.sandbox_id)
-        except (InvalidStateError, SessionTerminatedError):
-            if await self._current_state() not in ENDED_STATES:
-                raise
-            logger.info("Tenki session %s was already terminating at terminate", self.sandbox_id)
-        await self.release()
+        await close_session(self._session)
 
     async def release(self) -> None:
-        """Stop the session's data-plane credential renewal, which close_if_open leaves to the caller for a session
-        that is already ending."""
-        reset = getattr(self._session, "_reset_data_plane", None)
-        if reset is not None:
-            await reset()
+        await release_session(self._session)
 
     async def _current_state(self) -> str:
-        try:
-            return (await self._session.refresh()).state
-        except SessionNotFoundError:
-            return "GONE"
+        return await _session_state(self._session)
 
     async def exec(self, *command: str) -> _CompletedProcess:
         """Run argv to completion as root, so a leading ``sudo`` is dropped. A lost stream is exit -1, which
@@ -329,3 +312,32 @@ async def _load_tarballs(self, artifacts: list) -> None:
         signed_urls = await self._signed_image_urls(artifacts)
         reachable = [url if self._can_download(url) else None for url in signed_urls]
         await self._load_docker_images(artifacts, reachable)
+
+
+async def close_session(session: Any) -> None:
+    """Terminate a session's VM. One another handle already terminated, while this one's cached state still says
+    running, is not an error."""
+    try:
+        await session.close_if_open()
+    except SessionNotFoundError:
+        logger.info("Tenki session %s was already gone at terminate", session.id)
+    except (InvalidStateError, SessionTerminatedError):
+        if await _session_state(session) not in ENDED_STATES:
+            raise
+        logger.info("Tenki session %s was already terminating at terminate", session.id)
+    await release_session(session)
+
+
+async def release_session(session: Any) -> None:
+    """Stop the session's data-plane credential renewal, which close_if_open leaves to the caller for a session
+    that is already ending."""
+    reset = getattr(session, "_reset_data_plane", None)
+    if reset is not None:
+        await reset()
+
+
+async def _session_state(session: Any) -> str:
+    try:
+        return (await session.refresh()).state
+    except SessionNotFoundError:
+        return "GONE"
diff --git a/src/agent_env/providers/sandbox_providers/tensorlake/provider.py b/src/agent_env/providers/sandbox_providers/tensorlake/provider.py
index 087a97c7..cbd0ed46 100644
--- a/src/agent_env/providers/sandbox_providers/tensorlake/provider.py
+++ b/src/agent_env/providers/sandbox_providers/tensorlake/provider.py
@@ -336,3 +336,10 @@ async def get_sandbox(self, sandbox_id: str) -> TensorlakeSandbox:
                 "Reconnected to Tensorlake sandbox %s, but image loading will fail closed: %s", sandbox_id, exc,
             )
         return sandbox
+
+    async def terminate_sandbox(self, sandbox_id: str) -> None:
+        try:
+            raw_sandbox = await self._sandbox_cls.connect(sandbox_id, **self._client_kwargs())
+            await raw_sandbox.terminate()
+        except SandboxNotFoundError:
+            logger.info("Tensorlake sandbox %s was already absent during terminate", sandbox_id)
diff --git a/src/agent_env/task/teardown.py b/src/agent_env/task/teardown.py
index 263e2f0e..f01419fe 100644
--- a/src/agent_env/task/teardown.py
+++ b/src/agent_env/task/teardown.py
@@ -98,14 +98,14 @@ async def take_down(sandbox: RecordedSandbox) -> None:
             return
         try:
             async with asyncio.timeout(timeout):
-                handle = await _terminate(sandbox)
+                on_this_machine = await _terminate(sandbox)
         except Exception as e:
             reason = f"timed out after {timeout:g}s" if isinstance(e, TimeoutError) else _described(e)
             logger.warning("teardown: %s (%s) was not terminated: %s", sandbox.sandbox_id, kind(sandbox), reason)
             failed.append((sandbox, reason))
             return
         context.metadata[TORN_DOWN_KEY] = [*context.metadata.get(TORN_DOWN_KEY, []), sandbox.sandbox_id]
-        if handle.ON_THIS_MACHINE and (why := await _remove_folder(sandbox)):
+        if on_this_machine and (why := await _remove_folder(sandbox)):
             failed.append((sandbox, why))
         else:
             terminated.append(sandbox)
@@ -133,12 +133,17 @@ async def _remove_folder(sandbox: RecordedSandbox) -> str | None:
     return None
 
 
-async def _terminate(sandbox: RecordedSandbox):
-    provider = (build_sandbox_provider(sandbox.sandbox_type) if sandbox.sandbox_type
-                else _DEFAULT_PROVIDERS[sandbox.slot]())
-    handle = await provider.get_sandbox(sandbox.sandbox_id)
+async def _terminate(sandbox: RecordedSandbox) -> bool:
+    """Terminate ``sandbox`` and say whether it ran on this machine: by id through the backend that made it, or, for
+    a record that doesn't name one, through a live handle, since "not found" from a provider that didn't make the
+    sandbox doesn't mean it's gone."""
+    if sandbox.sandbox_type:
+        provider = build_sandbox_provider(sandbox.sandbox_type)
+        await provider.terminate_sandbox(sandbox.sandbox_id)
+        return provider.ON_THIS_MACHINE
+    handle = await _DEFAULT_PROVIDERS[sandbox.slot]().get_sandbox(sandbox.sandbox_id)
     await handle.terminate()
-    return handle
+    return handle.ON_THIS_MACHINE
 
 
 def _described(error: Exception) -> str:
diff --git a/src/agent_env/task_step/task_steps/teardown_sandboxes.py b/src/agent_env/task_step/task_steps/teardown_sandboxes.py
index 7f8f1539..e53ec765 100644
--- a/src/agent_env/task_step/task_steps/teardown_sandboxes.py
+++ b/src/agent_env/task_step/task_steps/teardown_sandboxes.py
@@ -166,8 +166,10 @@ def _is_backend(name: str) -> bool:
 
 
 async def _terminate(sandbox_id: str, sandbox_type: Optional[str], default_slot: str) -> None:
-    provider: SandboxProvider = (
-        build_sandbox_provider(sandbox_type) if sandbox_type else _DEFAULT_PROVIDERS[default_slot]()
-    )
-    sandbox = await provider.get_sandbox(sandbox_id)
-    await sandbox.terminate()
+    """By id through the backend that made it; a record that doesn't name one goes through a live handle, since
+    "not found" from a provider that didn't make the sandbox doesn't mean it's gone."""
+    if sandbox_type:
+        await build_sandbox_provider(sandbox_type).terminate_sandbox(sandbox_id)
+        return
+    provider: SandboxProvider = _DEFAULT_PROVIDERS[default_slot]()
+    await (await provider.get_sandbox(sandbox_id)).terminate()
diff --git a/tst/manual/smol_vm_agent_check.py b/tst/manual/smol_vm_agent_check.py
index 9909d467..eda376aa 100644
--- a/tst/manual/smol_vm_agent_check.py
+++ b/tst/manual/smol_vm_agent_check.py
@@ -13,7 +13,7 @@
 from agent_env.task_step.context import TaskStepContext
 from agent_env.task_step.task_steps.deploy_agent import DeployAgentTaskStep
 from agent_env.task_step.task_steps.deploy_sandbox import DeploySandboxTaskStep
-from tst.integration.store.local_parallel_deploy_test import local_stack  # noqa: F401
+from tst.integration.store.local_parallel_deploy_test import local_stack as local_stack
 from tst.util.a2a_test_agent import build_test_agent_image, put_test_agent
 
 
diff --git a/tst/manual/smol_vm_gateway_check.py b/tst/manual/smol_vm_gateway_check.py
index 7b8730d2..a5534e33 100644
--- a/tst/manual/smol_vm_gateway_check.py
+++ b/tst/manual/smol_vm_gateway_check.py
@@ -18,7 +18,7 @@
 from agent_env.task_step.task_steps.deploy_sandbox import DeploySandboxTaskStep
 from tst.integration.env.envs.multi_env_local_test import _items_universe
 from tst.integration.env.envs.server_env_local_test import _put_items_image
-from tst.integration.store.local_parallel_deploy_test import _seed_bootstrap_envs, local_stack  # noqa: F401
+from tst.integration.store.local_parallel_deploy_test import _seed_bootstrap_envs, local_stack as local_stack
 from tst.util.a2a_test_agent import put_test_agent
 
 
diff --git a/tst/unit/bundle/run_teardown_test.py b/tst/unit/bundle/run_teardown_test.py
index 916dbaf2..40af715d 100644
--- a/tst/unit/bundle/run_teardown_test.py
+++ b/tst/unit/bundle/run_teardown_test.py
@@ -22,6 +22,7 @@
 from agent_env.env.env import DeployedGatewayEnv
 from agent_env.task_step.context import DeployedAgent, DeployedSandbox, TaskStepContext
 from agent_env.task_step.task_step import TaskStep
+from agent_env.providers.sandbox_providers.sandbox_provider import SandboxProvider
 from tst.unit.bundle._support import layout, local_store
 
 pytestmark = pytest.mark.usefixtures("sigint_handled")
@@ -91,7 +92,7 @@ def __init__(self):
 def terminated(monkeypatch):
     log = _Terminated()
 
-    class _Provider:
+    class _Provider(SandboxProvider):
         async def get_sandbox(self, sandbox_id):
             return _FakeSandbox(log, sandbox_id)
 
diff --git a/tst/unit/cli/eval_run_teardown_test.py b/tst/unit/cli/eval_run_teardown_test.py
index 6a07b939..c9575317 100644
--- a/tst/unit/cli/eval_run_teardown_test.py
+++ b/tst/unit/cli/eval_run_teardown_test.py
@@ -15,6 +15,7 @@
 from agent_env.task import Task, teardown
 from agent_env.task.teardown import TeardownReport
 from agent_env.task_step.context import DeployedSandbox
+from agent_env.providers.sandbox_providers.sandbox_provider import SandboxProvider
 
 eval_run = importlib.import_module("agent_env.cli.eval.run")  # the package's ``run`` is the click command
 pytestmark = pytest.mark.usefixtures("sigint_handled")
@@ -81,7 +82,7 @@ async def terminate(self):
                 await asyncio.sleep(0.2)
             terminated.append(self.sandbox_id)
 
-    class _Provider:
+    class _Provider(SandboxProvider):
         async def get_sandbox(self, sandbox_id):
             return _Sandbox(sandbox_id)
 
diff --git a/tst/unit/providers/sandbox_providers/e2b_sandbox_provider_test.py b/tst/unit/providers/sandbox_providers/e2b_sandbox_provider_test.py
index 7ec2b44d..1cdfc4fe 100644
--- a/tst/unit/providers/sandbox_providers/e2b_sandbox_provider_test.py
+++ b/tst/unit/providers/sandbox_providers/e2b_sandbox_provider_test.py
@@ -328,3 +328,17 @@ async def test_adapter_construction_failure_kills_raw_sandbox():
         await provider.create_vm(exposed_ports=[8080], setup_for_gateway=False)
 
     raw.kill.assert_awaited_once_with()
+
+
+@pytest.mark.parametrize("killed", [True, False], ids=["killed", "already absent"])
+@pytest.mark.asyncio
+async def test_terminate_sandbox_kills_by_id_without_connecting(monkeypatch, killed):
+    kill = AsyncMock(return_value=killed)
+    monkeypatch.setattr(_AsyncSandboxSdk, "kill", kill, raising=False)
+    provider = E2BSandboxProvider(api_key="e2b-secret", base_template="agent-env-v1", template_resolver=_Resolver(),
+                                  sandbox_cls=_AsyncSandboxSdk)
+
+    await provider.terminate_sandbox("e2b-sandbox-1")
+
+    kill.assert_awaited_once_with("e2b-sandbox-1", api_key="e2b-secret")
+    _AsyncSandboxSdk.connect.assert_not_called()
diff --git a/tst/unit/providers/sandbox_providers/modal_sandbox_test.py b/tst/unit/providers/sandbox_providers/modal_sandbox_test.py
index 3b1e9bea..82b0b0d7 100644
--- a/tst/unit/providers/sandbox_providers/modal_sandbox_test.py
+++ b/tst/unit/providers/sandbox_providers/modal_sandbox_test.py
@@ -5,6 +5,7 @@
 import asyncio
 from unittest.mock import AsyncMock, MagicMock, patch
 
+import modal
 import pytest
 
 from agent_env.config import get_config
@@ -437,3 +438,34 @@ async def collect(chunks, destination_path):
     sandbox._write_stream_via_exec = collect
     await sandbox.write_file_from_object(url, "/data/a.json")
     assert written == [(b"LOCAL", "/data/a.json")]
+
+
+@pytest.mark.asyncio
+async def test_terminate_sandbox_terminates_by_id_without_reading_its_tunnels(_patched_provider):
+    sb = MagicMock()
+    sb.tunnels.aio = AsyncMock(side_effect=modal.exception.ConflictError("Sandbox has already finished with status terminated"))
+    sb.terminate.aio = AsyncMock()
+    with patch("agent_env.providers.sandbox_providers.modal_sandbox.modal.Sandbox.from_id") as from_id:
+        from_id.aio = AsyncMock(return_value=sb)
+        await _patched_provider.terminate_sandbox("sb-finished")
+
+    sb.terminate.aio.assert_awaited_once()
+    sb.tunnels.aio.assert_not_called()
+    sb.exec.aio.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_terminate_sandbox_counts_a_sandbox_modal_no_longer_knows_as_gone(_patched_provider):
+    with patch("agent_env.providers.sandbox_providers.modal_sandbox.modal.Sandbox.from_id") as from_id:
+        from_id.aio = AsyncMock(side_effect=modal.exception.NotFoundError("Sandbox not found"))
+        await _patched_provider.terminate_sandbox("sb-gone")
+
+
+@pytest.mark.asyncio
+async def test_get_sandbox_still_raises_for_a_finished_sandbox_so_a_reattach_sees_it_dead(_patched_provider):
+    sb = MagicMock()
+    sb.tunnels.aio = AsyncMock(side_effect=modal.exception.ConflictError("Sandbox has already finished with status terminated"))
+    with patch("agent_env.providers.sandbox_providers.modal_sandbox.modal.Sandbox.from_id") as from_id:
+        from_id.aio = AsyncMock(return_value=sb)
+        with pytest.raises(modal.exception.ConflictError):
+            await _patched_provider.get_sandbox("sb-finished")
diff --git a/tst/unit/providers/sandbox_providers/modal_vm_sandbox_test.py b/tst/unit/providers/sandbox_providers/modal_vm_sandbox_test.py
index 514c5e29..2a8ce590 100644
--- a/tst/unit/providers/sandbox_providers/modal_vm_sandbox_test.py
+++ b/tst/unit/providers/sandbox_providers/modal_vm_sandbox_test.py
@@ -9,6 +9,7 @@
 
 from unittest.mock import AsyncMock, MagicMock, patch
 
+import modal
 import pytest
 
 from agent_env.providers.sandbox_providers.modal_vm_sandbox import ModalVmSandbox, ModalVmSandboxProvider
@@ -395,3 +396,19 @@ async def test_apps_are_looked_up_in_the_configured_environment():
         lookup.aio = AsyncMock(return_value=MagicMock())
         await provider._get_app("agent-env-p")
     assert lookup.aio.call_args.kwargs["environment_name"] == "rl-prod"
+
+
+@pytest.mark.parametrize("found", [True, False], ids=["live or finished", "gone"])
+@pytest.mark.asyncio
+async def test_terminate_sandbox_terminates_a_vm_by_id_and_counts_one_modal_no_longer_knows_as_gone(found):
+    provider = ModalVmSandboxProvider()
+    provider._get_client = AsyncMock(return_value=MagicMock())  # type: ignore[method-assign]
+    sb = MagicMock()
+    sb.terminate.aio = AsyncMock()
+    with patch("agent_env.providers.sandbox_providers.modal_sandbox.modal.Sandbox.from_id") as from_id:
+        from_id.aio = (AsyncMock(return_value=sb) if found
+                       else AsyncMock(side_effect=modal.exception.NotFoundError("Sandbox not found")))
+        await provider.terminate_sandbox("sb-vm")
+
+    assert sb.terminate.aio.await_count == (1 if found else 0)
+    sb.tunnels.aio.assert_not_called()
diff --git a/tst/unit/providers/sandbox_providers/sail_vm_sandbox_provider_test.py b/tst/unit/providers/sandbox_providers/sail_vm_sandbox_provider_test.py
index bce5ff88..fb89a870 100644
--- a/tst/unit/providers/sandbox_providers/sail_vm_sandbox_provider_test.py
+++ b/tst/unit/providers/sandbox_providers/sail_vm_sandbox_provider_test.py
@@ -407,3 +407,16 @@ def test_a_rejected_key_can_be_retried():
     assert _sdk.API_KEY_ENV not in os.environ
     _sdk.connect("sail-secret", "agent-env", sdk=sdk)
     assert sdk.reset_transports.call_count == 2
+
+
+@pytest.mark.asyncio
+async def test_terminate_sandbox_terminates_through_the_handle_and_counts_a_sailbox_gone_as_terminated():
+    sailbox = _sailbox()
+    sdk = _fake_sdk(sailbox)
+    provider = _provider(sdk)
+
+    await provider.terminate_sandbox("sb_1")
+    sailbox.terminate.aio.assert_awaited_once()
+
+    sdk.Sailbox.get.aio = AsyncMock(side_effect=sdk.NotFoundError("gone"))
+    await provider.terminate_sandbox("sb_gone")
diff --git a/tst/unit/providers/sandbox_providers/smol_vm_provider_test.py b/tst/unit/providers/sandbox_providers/smol_vm_provider_test.py
index 85c0a4a6..274d504d 100644
--- a/tst/unit/providers/sandbox_providers/smol_vm_provider_test.py
+++ b/tst/unit/providers/sandbox_providers/smol_vm_provider_test.py
@@ -57,7 +57,7 @@ class FakeMachine:
         id = "agentenv-test"
 
         def endpoint(self, port):
-            return SimpleNamespace(http_url=f"http://127.0.0.1:44000")
+            return SimpleNamespace(http_url="http://127.0.0.1:44000")
 
         def write_file(self, path, data):
             created.append((path, data))
@@ -298,3 +298,20 @@ async def test_loopback_advertised_grant_uses_object_push(monkeypatch, tmp_path)
     await sandbox._download_object_to_vm(object_url, "/storage/image.tar.gz")
 
     sandbox._write_unsigned_object.assert_awaited_once_with(store, object_url, "/storage/image.tar.gz")
+
+
+@pytest.mark.parametrize("listed", [True, False], ids=["listed", "gone"])
+@pytest.mark.asyncio
+async def test_terminate_sandbox_deletes_a_listed_machine_without_setting_it_up(monkeypatch, listed):
+    deleted = []
+    connect = MagicMock(return_value=SimpleNamespace(delete=lambda: deleted.append(True)))
+    machines = [SimpleNamespace(name="agentenv-vm-1")] if listed else []
+    monkeypatch.setattr(module, "Machine", SimpleNamespace(list=lambda conn: machines, connect=connect))
+    setup = AsyncMock()
+    monkeypatch.setattr(module.SmolVmSandboxProvider, "_setup_docker", setup)
+
+    await module.SmolVmSandboxProvider().terminate_sandbox("agentenv-vm-1")
+
+    assert deleted == ([True] if listed else [])
+    assert connect.called is listed
+    setup.assert_not_called()
diff --git a/tst/unit/providers/sandbox_providers/tenki_sandbox_provider_test.py b/tst/unit/providers/sandbox_providers/tenki_sandbox_provider_test.py
index 9830f0b5..8a905ec6 100644
--- a/tst/unit/providers/sandbox_providers/tenki_sandbox_provider_test.py
+++ b/tst/unit/providers/sandbox_providers/tenki_sandbox_provider_test.py
@@ -21,7 +21,7 @@
     vm_shape,
 )
 from agent_env.providers.sandbox_providers.tenki.sandbox import DOCKER_BOOTSTRAP, TenkiSandbox
-from tenki import SandboxError
+from tenki import SandboxError, SessionNotFoundError
 
 from tst.unit.providers.sandbox_providers.tenki_fakes import FakeSession, fake_client_cls, result
 
@@ -383,3 +383,26 @@ async def test_get_sandbox_restores_ports_policy_and_lifetime(client_cls):
         mode=ALLOWLIST, allow_hosts=("pypi.org",), allow_cidrs=("10.0.0.0/8",),
     )
     assert 1700 <= sandbox.command_timeout <= 1800
+
+
+@pytest.mark.asyncio
+async def test_terminate_sandbox_closes_the_session_by_id(client_cls):
+    provider = _provider(client_cls)
+    created = await provider.create_vm(setup_for_gateway=False)
+    session = client_cls.instances[0].sessions[created.sandbox_id]
+
+    await provider.terminate_sandbox(created.sandbox_id)
+
+    assert (session.closed, session.info.state) == (1, "TERMINATED")
+
+
+@pytest.mark.asyncio
+async def test_terminate_sandbox_counts_a_session_tenki_no_longer_knows_as_gone(client_cls, monkeypatch):
+    provider = _provider(client_cls)
+    client = provider._client()
+
+    async def gone(sandbox_id):
+        raise SessionNotFoundError("gone")
+
+    monkeypatch.setattr(client, "get", gone)
+    await provider.terminate_sandbox("sess-gone")
diff --git a/tst/unit/providers/sandbox_providers/tensorlake_sandbox_provider_test.py b/tst/unit/providers/sandbox_providers/tensorlake_sandbox_provider_test.py
index 788a49d9..703fd224 100644
--- a/tst/unit/providers/sandbox_providers/tensorlake_sandbox_provider_test.py
+++ b/tst/unit/providers/sandbox_providers/tensorlake_sandbox_provider_test.py
@@ -451,3 +451,25 @@ async def test_get_sandbox_with_an_unknown_policy_fails_closed():
     sandbox = await provider.get_sandbox("tl-test")
 
     assert sandbox.network_policy is None
+
+
+@pytest.mark.asyncio
+async def test_terminate_sandbox_connects_by_id_and_terminates_without_reading_its_info():
+    raw = _raw_sandbox()
+    provider, sdk = _provider(raw)
+
+    await provider.terminate_sandbox("tl-test")
+
+    sdk.connect.assert_awaited_once()
+    raw.terminate.assert_awaited_once()
+    raw.info.assert_not_called()
+
+
+@pytest.mark.parametrize("where", ["connect", "terminate"])
+@pytest.mark.asyncio
+async def test_terminate_sandbox_counts_a_sandbox_tensorlake_no_longer_knows_as_gone(where):
+    raw = _raw_sandbox()
+    provider, sdk = _provider(raw)
+    (sdk.connect if where == "connect" else raw.terminate).side_effect = SandboxNotFoundError("tl-test")
+
+    await provider.terminate_sandbox("tl-test")
diff --git a/tst/unit/task/teardown_test.py b/tst/unit/task/teardown_test.py
index 1c7b5aea..7ceb5c77 100644
--- a/tst/unit/task/teardown_test.py
+++ b/tst/unit/task/teardown_test.py
@@ -8,9 +8,13 @@
 import tempfile
 import time
 
+from unittest.mock import AsyncMock, MagicMock
+
+import modal
 import pytest
 
 from agent_env.env.env import DeployedEnv, DeployedGatewayEnv
+from agent_env.providers.sandbox_providers.modal_sandbox import ModalSandboxProvider
 from agent_env.providers.sandbox_providers.local_sandbox import LocalSandbox, remove_local_work_dir
 from agent_env.task import teardown
 from agent_env.task.teardown import RecordedSandbox, TeardownReport, recorded_sandboxes, teardown_run
@@ -35,6 +39,8 @@ async def terminate(self):
 
 
 class _FakeProvider:
+    ON_THIS_MACHINE = False
+
     def __init__(self, name, log):
         self.name, self.log = name, log
 
@@ -43,6 +49,9 @@ async def get_sandbox(self, sandbox_id):
             raise RuntimeError(f"no sandbox {sandbox_id}")
         return _FakeSandbox(self, sandbox_id)
 
+    async def terminate_sandbox(self, sandbox_id):
+        await (await self.get_sandbox(sandbox_id)).terminate()
+
 
 class _Log(list):
     """The (provider, sandbox_id) terminate log, and how given sandboxes misbehave."""
@@ -144,6 +153,44 @@ def test_a_terminate_that_fails_is_reported_not_raised_and_the_others_still_go(t
     assert "sb-gw" not in context.metadata[TORN_DOWN_KEY]
 
 
+def test_a_record_that_names_its_backend_is_terminated_by_id_and_one_that_doesnt_through_a_handle(
+    terminated, monkeypatch,
+):
+    by_id = []
+
+    async def terminate_sandbox(self, sandbox_id):
+        by_id.append((self.name, sandbox_id))
+
+    monkeypatch.setattr(_FakeProvider, "terminate_sandbox", terminate_sandbox)
+    context = TaskStepContext(deployed_sandboxes=[
+        DeployedSandbox(sandbox_name="named", sandbox_id="sb-named", sandbox_mode="vm", sandbox_type="modal"),
+        DeployedSandbox(sandbox_name="unnamed", sandbox_id="sb-unnamed", sandbox_mode="vm"),
+    ])
+
+    report = _run(context)
+
+    assert by_id == [("modal", "sb-named")]
+    assert terminated == [("default-sandbox", "sb-unnamed")]
+    assert {sandbox.sandbox_id for sandbox in report.terminated} == {"sb-named", "sb-unnamed"}
+
+
+def test_a_modal_sandbox_that_already_finished_is_counted_down_not_reported_up(monkeypatch):
+    sb = MagicMock()
+    sb.tunnels.aio = AsyncMock(side_effect=modal.exception.ConflictError("Sandbox has already finished with status terminated"))
+    sb.terminate.aio = AsyncMock()
+    monkeypatch.setattr(modal.Sandbox, "from_id", MagicMock(aio=AsyncMock(return_value=sb)))
+    monkeypatch.setattr(ModalSandboxProvider, "_get_client", AsyncMock(return_value=MagicMock()))
+    context = TaskStepContext(deployed_sandboxes=[
+        DeployedSandbox(sandbox_name="box", sandbox_id="sb-finished", sandbox_mode="container", sandbox_type="modal")])
+
+    report = _run(context)
+
+    assert report.terminated == (RecordedSandbox("sb-finished", "modal", "sandbox"),)
+    assert report.still_up == ()
+    assert context.metadata[TORN_DOWN_KEY] == ["sb-finished"]
+    sb.tunnels.aio.assert_not_called()
+
+
 def test_cancelling_it_returns_what_it_reached_and_leaves_the_rest(terminated):
     terminated.behaviors["sb-gw"] = "hang"
     context = _context()
diff --git a/tst/unit/task_step/test_teardown_sandboxes.py b/tst/unit/task_step/test_teardown_sandboxes.py
index de32bcda..63617d85 100644
--- a/tst/unit/task_step/test_teardown_sandboxes.py
+++ b/tst/unit/task_step/test_teardown_sandboxes.py
@@ -34,6 +34,9 @@ def __init__(self, name, terminated, failing):
     async def get_sandbox(self, sandbox_id):
         return _FakeSandbox(self, sandbox_id)
 
+    async def terminate_sandbox(self, sandbox_id):
+        await (await self.get_sandbox(sandbox_id)).terminate()
+
 
 class _Log(list):
     """The (provider, sandbox_id) terminate log, plus the sandbox ids whose terminate should fail."""
@@ -141,6 +144,20 @@ async def test_an_env_tears_down_every_sandbox_behind_it_on_its_own_backend(term
     ]
 
 
+@pytest.mark.asyncio
+async def test_a_typed_sandbox_is_terminated_by_id_without_a_handle(terminated, monkeypatch):
+    async def no_handle(self, sandbox_id):
+        raise AssertionError(f"asked {self.name} for a handle to {sandbox_id}")
+
+    async def by_id(self, sandbox_id):
+        self.terminated.append((self.name, sandbox_id))
+
+    monkeypatch.setattr(_FakeProvider, "get_sandbox", no_handle)
+    monkeypatch.setattr(_FakeProvider, "terminate_sandbox", by_id)
+    await _step(agent_names=["solver"]).execute(_context())
+    assert terminated == [("modal", "sb-solver")]
+
+
 @pytest.mark.asyncio
 async def test_an_untyped_sandbox_uses_its_slot_default(terminated):
     await _step(sandbox_names=["gpu-box"]).execute(_context())