diff --git a/deploy/agent-host/check.sh b/deploy/agent-host/check.sh
index 117c4a6..ac16a93 100755
--- a/deploy/agent-host/check.sh
+++ b/deploy/agent-host/check.sh
@@ -10,6 +10,11 @@ bad() { echo "FAIL: $1"; fail=1; }
 cd "$stack" || { echo "FAIL: no $stack"; exit 1; }
 [ "$(sudo docker compose ps --status running -q | wc -l)" -ge 1 ] \
   && ok "SilverBullet is running" || bad "SilverBullet isn't running"
+if sudo docker compose logs --no-color silverbullet 2>/dev/null | grep -q 'boot mode: single-space'; then
+  bad "it booted a single space with no accounts (an SB_* setting?)"
+else
+  ok "it keeps accounts (no single-space boot)"
+fi
 code=$(curl -s -o /dev/null -w '%{http_code}' http://127.0.0.1:3000/)
 case $code in 2??|3??) ok "it answers locally ($code)" ;; *) bad "it answers $code" ;; esac
 probe=.nisse-probe-$$
diff --git a/deploy/agent-host/silverbullet/compose.yaml b/deploy/agent-host/silverbullet/compose.yaml
index 73aaabc..862d666 100644
--- a/deploy/agent-host/silverbullet/compose.yaml
+++ b/deploy/agent-host/silverbullet/compose.yaml
@@ -8,9 +8,10 @@ services:
     image: ghcr.io/silverbulletmd/silverbullet:2.11.1-slim
     restart: unless-stopped
     environment:
+      # Only these. Any SB_* setting (even SB_NAME) boots a single space with
+      # no accounts, serving /data instead of the vault.
       PUID: "1000"
       PGID: "1000"
-      SB_NAME: Nisse vault
     ports:
       # IPv4 only; setup.sh's firewall lets only the operator's Caddy in.
       - "0.0.0.0:3000:3000"
diff --git a/tests/deploy/test_agent_host.py b/tests/deploy/test_agent_host.py
index 21f0b62..ec47048 100644
--- a/tests/deploy/test_agent_host.py
+++ b/tests/deploy/test_agent_host.py
@@ -67,6 +67,12 @@ def test_no_secrets_in_the_compose_file() -> None:
     assert not [k for k in environment if re.search(r"USER|TOKEN|PASS|SECRET|KEY", k)]
 
 
+def test_it_boots_into_accounts_and_the_vault_not_a_bare_space() -> None:
+    # SB_NAME alone switched 2.11 to single-space mode: no accounts, no setup
+    # wizard, and /data served in place of the vault.
+    assert set(silverbullet()["environment"]) == {"PUID", "PGID"}
+
+
 def test_its_port_caddys_and_the_firewalls_agree() -> None:
     port = setting("SB_PORT")
     assert silverbullet()["ports"] == [f"0.0.0.0:{port}:3000"]  # IPv4 only
@@ -120,7 +126,9 @@ def test_the_firewall_lets_only_one_address_in_and_replaces_its_own_rule() -> No
 SCRIPT = HOST.parents[1] / "scripts" / "agent-host.sh"
 
 
-def _fake_host(tmp_path: Path, *, memory_writable: bool) -> dict[str, str]:
+def _fake_host(
+    tmp_path: Path, *, memory_writable: bool, boot: str = "multi-space"
+) -> dict[str, str]:
     """Commands standing in for the host's: ssh runs the command here, sudo
     just runs it, and docker reads all of stdin, as docker compose exec does."""
     bin_ = tmp_path / "bin"
@@ -134,6 +142,7 @@ def _fake_host(tmp_path: Path, *, memory_writable: bool) -> dict[str, str]:
             "cat > /dev/null\n"
             'case "$*" in\n'
             '  *"ps --status running"*) echo abc123 ;;\n'
+            f'  *" logs "*) echo "boot mode: {boot}" ;;\n'
             f'  *"/vault/memory/"*) exit {0 if memory_writable else 1} ;;\n'
             "esac"
         ),
@@ -167,6 +176,7 @@ def test_the_check_runs_every_step_even_though_docker_reads_stdin(
     assert result.returncode == 0, result.stdout + result.stderr
     assert result.stdout.splitlines() == [
         "ok:   SilverBullet is running",
+        "ok:   it keeps accounts (no single-space boot)",
         "ok:   it answers locally (200)",
         "ok:   the operator's folders are writable",
         "ok:   memory/ is read-only to SilverBullet",
@@ -184,3 +194,9 @@ def test_a_writable_memory_folder_fails_the_check(tmp_path: Path) -> None:
     )
     assert "ok:   the firewall rule is in place" in result.stdout  # still checked
     assert "all checks passed" not in result.stdout
+
+
+def test_a_single_space_boot_fails_the_check(tmp_path: Path) -> None:
+    result = _check(_fake_host(tmp_path, memory_writable=False, boot="single-space"))
+    assert result.returncode == 1
+    assert "FAIL: it booted a single space with no accounts" in result.stdout