diff --git a/tests/test_mcp_tool_systems.py b/tests/test_mcp_tool_systems.py
index 2af2e3f..9432553 100644
--- a/tests/test_mcp_tool_systems.py
+++ b/tests/test_mcp_tool_systems.py
@@ -243,33 +243,11 @@ async def test_populated_vocabulary_never_counts_records():
     notes.list_notes.assert_not_awaited()
 
 
-@pytest.mark.asyncio
-async def test_create_system_same_normalized_name_is_duplicate_gated():
-    existing = fake_system(id=7, name="Scrape Pipeline")
-    existing.id = 7
-    existing.name = "Scrape Pipeline"
-    with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
-         patch("scribe.mcp.tools.systems.systems_svc") as svc:
-        svc.list_systems = AsyncMock(return_value=[existing])
-        svc.create_system = AsyncMock()
-        from scribe.mcp.tools.systems import create_system
-        result = await create_system(project_id=5, name="  scrape   pipeline ")
-    assert result["duplicate"] is True
-    assert result["existing_id"] == 7
-    svc.create_system.assert_not_awaited()
-
-
-@pytest.mark.asyncio
-async def test_create_system_distinct_name_passes_the_gate():
-    other = fake_system(id=7, name="Workers")
-    other.name = "Workers"
-    with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
-         patch("scribe.mcp.tools.systems.systems_svc") as svc:
-        svc.list_systems = AsyncMock(return_value=[other])
-        svc.create_system = AsyncMock(return_value=fake_system(id=8, name="Exporter"))
-        from scribe.mcp.tools.systems import create_system
-        result = await create_system(project_id=5, name="Exporter")
-    assert result["name"] == "Exporter"
+# The name gate's own cases (case/whitespace normalisation, exact-over-overlap,
+# fail-open) moved to tests/test_services_systems.py with the logic itself —
+# services/systems.assess_system_name, so both doors share one answer (#2482).
+# What stays the TOOL's job — rendering a duplicate, applying an exact area,
+# offering an overlap — is covered at the top of this file.
 
 
 @pytest.mark.asyncio
diff --git a/tests/test_services_systems.py b/tests/test_services_systems.py
index 905090b..a15decf 100644
--- a/tests/test_services_systems.py
+++ b/tests/test_services_systems.py
@@ -59,3 +59,70 @@ async def test_count_open_issues_denied_returns_zero():
         from scribe.services.systems import count_open_issues
         result = await count_open_issues(user_id=1, project_id=5)
     assert result == 0
+
+
+# ── assess_system_name — the one gate both doors call (milestone 307) ──
+
+@pytest.mark.asyncio
+async def test_assess_matches_an_existing_system_on_case_and_spacing():
+    """The local gate compares the operator's own spelling: case and runs of
+    whitespace are not a different System. Anything stronger belongs to the
+    CANONICAL slug, which is a different question (is this the same AREA as
+    another project's System) with a different answer."""
+    existing = MagicMock()
+    existing.id, existing.name = 7, "Scrape Pipeline"
+    with patch("scribe.services.systems.list_systems", AsyncMock(return_value=[existing])):
+        from scribe.services.systems import assess_system_name
+        out = await assess_system_name(1, 5, "  scrape   pipeline ")
+    assert out["duplicate"] == {"id": 7, "name": "Scrape Pipeline"}
+    # A duplicate short-circuits: there is nothing to file when nothing is created.
+    assert out["canonical"] is None
+
+
+@pytest.mark.asyncio
+async def test_assess_prefers_an_exact_area_over_a_merely_similar_one():
+    from scribe.services.systems import assess_system_name
+    exact = MagicMock()
+    exact.id, exact.name = 3, "CI & Release"
+    with patch("scribe.services.systems.list_systems", AsyncMock(return_value=[])), \
+         patch("scribe.services.systems.canonical_systems_svc") as canon:
+        canon.find_by_name = AsyncMock(return_value=exact)
+        canon.best_overlap = AsyncMock()
+        out = await assess_system_name(1, 5, "CI and Release")
+    assert out["canonical"] == {"id": 3, "name": "CI & Release", "basis": "exact"}
+    # An exact hit is the answer — no need to go looking for a lesser one.
+    canon.best_overlap.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_assess_falls_back_to_overlap_and_never_invents_a_match():
+    from scribe.services.systems import assess_system_name
+    near = {"id": 3, "name": "CI & Release", "basis": "overlap", "score": 0.33}
+    with patch("scribe.services.systems.list_systems", AsyncMock(return_value=[])), \
+         patch("scribe.services.systems.canonical_systems_svc") as canon:
+        canon.find_by_name = AsyncMock(return_value=None)
+        canon.best_overlap = AsyncMock(return_value=near)
+        assert (await assess_system_name(1, 5, "CI & runners"))["canonical"] == near
+        canon.best_overlap = AsyncMock(return_value=None)
+        # Nothing resembles it: a project-specific area, and silence is the
+        # right answer — unmapped is a valid resting state.
+        assert (await assess_system_name(1, 5, "Soundboard"))["canonical"] is None
+
+
+@pytest.mark.asyncio
+async def test_assess_fails_open_so_a_naming_aid_cannot_block_a_create():
+    """Both arms degrade to "no opinion" rather than raising. A create must
+    never fail because the catalog was unreachable."""
+    from scribe.services.systems import assess_system_name
+    with patch("scribe.services.systems.list_systems", AsyncMock(side_effect=RuntimeError("db down"))):
+        assert await assess_system_name(1, 5, "Reader") == {"duplicate": None, "canonical": None}
+    with patch("scribe.services.systems.list_systems", AsyncMock(return_value=[])), \
+         patch("scribe.services.systems.canonical_systems_svc") as canon:
+        canon.find_by_name = AsyncMock(side_effect=RuntimeError("db down"))
+        assert (await assess_system_name(1, 5, "Reader"))["canonical"] is None
+
+
+@pytest.mark.asyncio
+async def test_assess_says_nothing_about_a_nameless_system():
+    from scribe.services.systems import assess_system_name
+    assert await assess_system_name(1, 5, "   ") == {"duplicate": None, "canonical": None}