diff --git a/tst/integration/computer/clock-follower/envs/desktop/env.toml b/tst/integration/computer/clock-follower/envs/desktop/env.toml
new file mode 100644
index 000000000..4d17f5b6e
--- /dev/null
+++ b/tst/integration/computer/clock-follower/envs/desktop/env.toml
@@ -0,0 +1,4 @@
+type = "computer"
+computer = "ubuntu-24.04"
+driver = "reference"
+apps = ["clock"]
diff --git a/tst/integration/computer/clock-follower/tasks/desktop.json b/tst/integration/computer/clock-follower/tasks/desktop.json
new file mode 100644
index 000000000..67f3b3154
--- /dev/null
+++ b/tst/integration/computer/clock-follower/tasks/desktop.json
@@ -0,0 +1,3 @@
+[
+  {"id": "env", "type": "deploy_env", "env_id": "desktop"}
+]
diff --git a/tst/integration/computer/clock_follower_test.py b/tst/integration/computer/clock_follower_test.py
new file mode 100644
index 000000000..35ba335b4
--- /dev/null
+++ b/tst/integration/computer/clock_follower_test.py
@@ -0,0 +1,163 @@
+"""A multi env's computer on its gateway's clock, end to end on the local backend: the clock follower test bundle's
+desktop (the ubuntu-24.04 base, the reference driver and the ``clock`` app) deployed beside an MCP server.
+
+``sync_env_clock`` arms the gateway about 6 months back: core starts the computer's follower as root, the arm waits for
+it, and the session's shell and Python then read the gateway's universe time. An advance of a day and a re-arm at 60x
+reach them too, each acknowledged before its write returns. The session user can't write the clock page, read the
+follower's config or stop the follower, and a follower killed as root is back for the next write. Needs Docker and the
+local registry on localhost:5000."""
+
+import asyncio
+import subprocess
+import time
+import uuid
+from datetime import datetime, timezone
+
+import pytest
+from agent_env.env import Env
+from agent_env.env.env import DeployedEnv
+from agent_env.env.envs.computer.utils import clock, inside
+from agent_env.env.envs.mcp_server import MCPServerEnv
+from agent_env.env.envs.multi_env import MultiEnv
+from agent_env.env.gateway.constants import EXT_CLOCK_URI
+from agent_env.store.routing import namespace_routing
+from agent_env.task.teardown import teardown_run
+from agent_env.task_step.context import TaskStepContext
+from agent_env.task_step.task_steps.deploy_env import DeployEnvTaskStep
+from agent_env.task_step.task_steps.sync_env_clock import SyncEnvClockTaskStep
+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
+
+pytestmark = [pytest.mark.integration, pytest.mark.int_test_slow]
+
+CONTAINER = {"sandbox_type": "local", "env_params": {"form": "container"}}
+DAY = 86400
+#: How far outside the gateway's reads on either side of it a session's read may fall: the follower's offset estimate
+#: and the page's continuity, well inside the second a computer and the gateway must agree to.
+SLACK_S = 0.5
+
+
+def _iso(epoch: float) -> str:
+    return datetime.fromtimestamp(epoch, timezone.utc).isoformat().replace("+00:00", "Z")
+
+
+def _epoch(rfc3339: str) -> float:
+    return datetime.fromisoformat(rfc3339.replace("Z", "+00:00")).timestamp()
+
+
+async def _session_now(computer: DeployedEnv) -> dict[str, float]:
+    """The time the session user's shell and Python read, as epoch seconds."""
+    ran = await inside.run(computer, ["sh", "-c", "date +%s.%N; python3 -c 'import time; print(time.time())'"],
+                           timeout_s=30)
+    assert ran["exit_code"] == 0, ran
+    shell, python = ran["stdout"].split()
+    return {"shell": float(shell), "python": float(python)}
+
+
+async def _gateway_now(deployed: DeployedEnv) -> float:
+    return _epoch((await deployed.invoke(EXT_CLOCK_URI, "state"))["virtual_time"])
+
+
+async def _agreement(computer: DeployedEnv, deployed: DeployedEnv) -> dict:
+    """The session's shell and Python times, read between two reads of the gateway's clock."""
+    first = await _gateway_now(deployed)
+    session = await _session_now(computer)
+    return {"gateway": (first, await _gateway_now(deployed)), **session}
+
+
+def _agrees(read: dict) -> bool:
+    low, high = read["gateway"]
+    return all(low - SLACK_S <= read[what] <= high + SLACK_S for what in ("shell", "python"))
+
+
+async def _as_session(computer: DeployedEnv, command: str) -> dict:
+    return await inside.run(computer, ["sh", "-c", command], timeout_s=30)
+
+
+def _container(computer: DeployedEnv) -> str:
+    """The computer's container, the one of its sandbox's holding the follower."""
+    listed = subprocess.run(["docker", "ps", "-q", "--filter", f"name={computer.sandbox_id}"],
+                            capture_output=True, text=True, check=True).stdout.split()
+    for container in listed:
+        if subprocess.run(["docker", "exec", container, "test", "-e", "/opt/agentenv/clock/follow"]).returncode == 0:
+            return container
+    raise AssertionError(f"no container of sandbox {computer.sandbox_id} has the clock follower: {listed}")
+
+
+def _as_root(container: str, *argv: str) -> str:
+    return subprocess.run(["docker", "exec", "-u", "0", container, *argv], capture_output=True, text=True).stdout
+
+
+@pytest.fixture(scope="module")
+def items(clock_follower_desktop):
+    with namespace_routing():
+        _seed_bootstrap_envs()
+        uid = uuid.uuid4().hex[:8]
+        return MCPServerEnv.put(id=f"@local/~/clock-{uid}/items", environment_name="items",
+                                docker_image_artifact=_put_items_image(f"clock-items-{uid}"))
+
+
+@pytest.mark.asyncio
+async def test_a_multi_envs_computer_follows_its_gateways_clock_through_an_arm_an_advance_and_a_rate(
+        clock_follower_desktop, items):
+    with namespace_routing():
+        office = MultiEnv.put(id=f"@local/~/clock-{uuid.uuid4().hex[:8]}/office", mcp_server_envs=[items],
+                              computer_envs=[Env.get(clock_follower_desktop.id)], name="office")
+        context = TaskStepContext()
+        try:
+            [deployed] = (await DeployEnvTaskStep(id="office", version=None, env_id=office.id, sandbox_type="local",
+                                                  ttl_seconds=900, child_envs={"desktop": CONTAINER})
+                          .execute(context)).deployed_envs
+            computer = DeployedEnv.from_dict(deployed.child_envs["desktop"])
+            follows = clock.runs_follower(computer.environment_card)
+            before = await _session_now(computer)
+            real_before = time.time()
+
+            universe = time.time() - 182 * DAY
+            armed_at = time.monotonic()
+            await SyncEnvClockTaskStep(id="arm", version=None, env_id=office.id,
+                                       virtual_time=_iso(universe)).execute(context)
+            arm_s = time.monotonic() - armed_at
+            configuration = context.metadata["clock_configurations"][-1]
+            armed = await _agreement(computer, deployed)
+
+            target = armed["gateway"][1] + DAY
+            await deployed.invoke(EXT_CLOCK_URI, "advance", {"virtual_time": _iso(target), "wait_followers_s": 10})
+            advanced = await _agreement(computer, deployed)
+
+            await SyncEnvClockTaskStep(id="fast", version=None, env_id=office.id, virtual_time=_iso(target),
+                                       virtual_seconds_per_real_second=60).execute(context)
+            fast = [await _session_now(computer)]
+            await asyncio.sleep(3)
+            fast.append(await _session_now(computer))
+
+            # The session user can't change, stop or read into the clock.
+            refused = {
+                "write_page": await _as_session(computer, "printf x > /dev/shm/agentenv-clock"),
+                "write_file": await _as_session(computer, "echo '@0 x1' > /run/agentenv-clock/clock"),
+                "read_config": await _as_session(computer, f"cat {clock.CONFIG}"),
+                "kill": await _as_session(computer, "pkill -9 -u agentenv-clock"),
+            }
+            # Killed as root, the follower is back for the next write, which waits for it.
+            container = _container(computer)
+            _as_root(container, "pkill", "-9", "-u", "agentenv-clock")
+            await asyncio.sleep(2.5)
+            back = _as_root(container, "pgrep", "-u", "agentenv-clock").split()
+            await deployed.invoke(EXT_CLOCK_URI, "advance", {"virtual_time": _iso(target + 3 * DAY),
+                                                             "wait_followers_s": 10})
+            after_kill = await _agreement(computer, deployed)
+        finally:
+            report = await teardown_run(context)
+
+    assert follows, "the computer's card doesn't say it runs the clock follower"
+    assert abs(before["shell"] - real_before) < 5, before  # real time before the arm
+    assert [s["service"] for s in configuration["synced"] if s["service"] == "clock"] == ["clock"], configuration
+    assert arm_s < 30, arm_s
+    assert [read for read in (armed, advanced, after_kill) if not _agrees(read)] == []
+    assert abs(armed["gateway"][0] - universe) < 60, (armed, universe)
+    assert advanced["gateway"][0] - armed["gateway"][1] >= DAY, (armed, advanced)
+    assert after_kill["gateway"][0] >= target + 3 * DAY, after_kill
+    assert 3 * 60 * 0.8 < fast[1]["shell"] - fast[0]["shell"] < 3 * 60 * 1.6, fast  # ~3 s at 60x, plus the reads
+    assert all(result["exit_code"] != 0 for result in refused.values()), refused
+    assert back, "the follower wasn't restarted"
+    assert not report.failed
diff --git a/tst/integration/computer/conftest.py b/tst/integration/computer/conftest.py
index 3d2fdaf35..269d327f1 100644
--- a/tst/integration/computer/conftest.py
+++ b/tst/integration/computer/conftest.py
@@ -43,6 +43,8 @@
 BROWSER_COMPUTER = Path(__file__).parent / "browser-computer"
 TLS = Path(__file__).parent / "tls"
 CLOCK_DESKTOP = Path(__file__).parent / "clock-desktop"
+#: A desktop composing agent-env's clock app, whose follower keeps it on its multi env's gateway clock.
+CLOCK_FOLLOWER = Path(__file__).parent / "clock-follower"
 #: agent-env's libfaketime recipe, which the clock desktop's universe-clock app builds.
 CLOCK_RECIPE = Path(agent_env.__file__).parent / "computers" / "clock"
 #: Playwright and Puppeteer, which connect to a cdp address from Node.
@@ -134,6 +136,13 @@ def clock_desktop(tmp_path_factory):
     yield from _composed(root, parse_bundle(bundle))
 
 
+@pytest.fixture(scope="module")
+def clock_follower_desktop(tmp_path_factory):
+    """The clock follower test bundle's desktop, the ubuntu-24.04 base and the reference driver with agent-env's
+    ``clock`` app, composed as ``desktop`` is."""
+    yield from _composed(tmp_path_factory.mktemp("clock-follower"), parse_bundle(CLOCK_FOLLOWER))
+
+
 @pytest.fixture(scope="module")
 def cdp_clients(tmp_path_factory) -> Path:
     """The CDP clients installed in a folder of their own, or the test skipped without Node 20 or later and npm."""