diff --git a/scripts/gtdb_ground.py b/scripts/gtdb_ground.py
index fa2f646a..bddae2cf 100644
--- a/scripts/gtdb_ground.py
+++ b/scripts/gtdb_ground.py
@@ -157,6 +157,58 @@ def resolve_kg_microbe_dir(explicit: str | None) -> Path:
     )
 
 
+# GTDB appends an alphabetic suffix to every clade split off a genus/family that
+# does NOT contain the nomenclatural type: `g__Enterococcus_B` is Enterococcus
+# minus the lineage holding *E. faecalis*, which keeps the bare `g__Enterococcus`.
+# So the suffix is GTDB's own published marker for "not the type-anchored clade".
+_NON_TYPE_SUFFIX = re.compile(r"^(?P<base>[A-Z][A-Za-z0-9-]*)_(?P<suffix>[A-Z]+)$")
+
+
+def non_type_clade(name: str) -> str | None:
+    """The unsuffixed sibling of a GTDB name, when the name is a non-type clade.
+
+    Returns the base name (`Enterococcus` for `Enterococcus_B`), else None.
+
+    Used to *flag* rather than to *resolve* (#374). Grounding by majority-of-
+    genomes and GTDB's type-species rule disagree whenever a non-type clade is
+    more heavily sequenced. Verified against GTDB R226, that is one taxon of the
+    five where the two denominators differ — `Enterococcus` grounds to
+    `g__Enterococcus_B` while *E. faecalis* sits in `g__Enterococcus`. The other
+    four agree because the majority happens to be the type clade, which is luck
+    and not construction; nothing stops them flipping as sequencing depth shifts.
+
+    Deliberately not used to override the answer. Preferring the type clade
+    would change what every existing grounding means, on the evidence of a
+    single live case — and the majority answer is not obviously wrong, since a
+    user asking for "NCBI genus X" may well want the clade most of X's genomes
+    are in. Emitting both and letting a curator see the conflict costs nothing
+    and forecloses nothing.
+    """
+    match = _NON_TYPE_SUFFIX.match(name or "")
+    return match.group("base") if match else None
+
+
+def _non_type_warning(chosen: str, weights: dict) -> str:
+    """Human-readable note for a grounding that is not the type-anchored clade.
+
+    Says whether the unsuffixed sibling was even a contender, because the two
+    cases call for different curator action: if it drew genomes here, this is a
+    close call worth a look; if it drew none, the NCBI name's genomes simply do
+    not sit in the type clade at all, which is a stronger statement.
+    """
+    base = non_type_clade(chosen)
+    sibling = weights.get(base)
+    if sibling:
+        return (
+            f"{chosen} is not the type-anchored clade; GTDB reserves {base} for the "
+            f"lineage holding the nomenclatural type, which drew {int(sibling)} genomes here (#374)"
+        )
+    return (
+        f"{chosen} is not the type-anchored clade; GTDB reserves {base} for the "
+        f"lineage holding the nomenclatural type, which drew no genomes here (#374)"
+    )
+
+
 def _curie(name: str, prefix: str) -> str:
     return f"GTDB:{prefix}__" + name.replace(" ", "_")
 
@@ -584,6 +636,15 @@ def resolve_higher(
                 "is_reclassified": top != _clean_label(label),
                 "via": f"ncbi_rank_{prefix}",
                 "n_alt": len(weights),
+                # The majority answer is a non-type clade, so it disagrees with
+                # GTDB's own naming rule (#374). Reported, not resolved: the
+                # curator decides. Key omitted entirely when there is no
+                # conflict, so its presence always means something.
+                **(
+                    {"non_type_clade_warning": _non_type_warning(top, weights)}
+                    if non_type_clade(top)
+                    else {}
+                ),
             }
         # Same tie-break as `top` above: ties here were still row-ordered, so the
         # AMBIGUOUS option list a curator reads was not reproducible (#382 review).
@@ -1913,6 +1974,12 @@ def main(argv: list[str] | None = None) -> int:
         # record's *nitrite* oxidizer. The number alone did not say "look here".
         near = "  ⚠ NEAR-TIE" if _is_near_tie(g.get("majority_fraction")) else ""
         print(f"  majority     : {g['majority_fraction']}{via}{of}{thin}{near}")
+        # Printed, not just stored (#374). The whole value of flagging rather
+        # than resolving is that a curator sees the conflict at the moment they
+        # ground the taxon; a key that only ever appears in emitted YAML would
+        # be found later or not at all.
+        if g.get("non_type_clade_warning"):
+            print(f"  ⚠ NON-TYPE   : {g['non_type_clade_warning']}")
         if args.emit_yaml:
             print("  --- gtdb_classification block ---")
             for line in emit_block(g, mapping_source).splitlines():
diff --git a/tests/test_gtdb_non_type_clade_flag.py b/tests/test_gtdb_non_type_clade_flag.py
new file mode 100644
index 00000000..0f6a1bc0
--- /dev/null
+++ b/tests/test_gtdb_non_type_clade_flag.py
@@ -0,0 +1,156 @@
+"""Grounding to a non-type clade is reported, not resolved (#374).
+
+`gtdb_ground.py` grounds a higher-rank NCBI taxon to whichever GTDB taxon holds
+the most genomes. GTDB names by **nomenclatural type**: the lineage containing
+the type species keeps the unsuffixed name and the rest take alphabetic
+suffixes. The two rules disagree whenever a non-type clade is more heavily
+sequenced.
+
+Verified against GTDB R226 (the mapping this repo reads), `Enterococcus` grounds
+to `g__Enterococcus_B` at 0.598 while *E. faecalis* — the type species — sits in
+`g__Enterococcus`, which drew 9904 of the 28462 genomes. The other four taxa
+where the denominators differ agree only because the majority happens to be the
+type clade, which is luck rather than construction.
+
+**Reported, not resolved, by decision.** Preferring the type clade would change
+what every existing grounding means on the evidence of one live case, and the
+majority answer is not obviously wrong — someone asking for "NCBI genus X" may
+well want the clade most of X's genomes are in. So the tool emits both and the
+curator decides.
+
+The suffix is not a heuristic: it is GTDB's own published marker for "this clade
+does not contain the type". That is why the check can be a regex and still be
+correct.
+"""
+
+from __future__ import annotations
+
+import importlib.util
+import pathlib
+
+import pytest
+
+REPO = pathlib.Path(__file__).parent.parent
+SCRIPT = REPO / "scripts/gtdb_ground.py"
+
+
+@pytest.fixture(scope="module")
+def gtdb():
+    spec = importlib.util.spec_from_file_location("gtdb_ground_under_test", SCRIPT)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+@pytest.mark.parametrize(
+    ("name", "expected_base"),
+    [
+        # Every non-type clade actually present in the KB today.
+        ("Enterococcus_B", "Enterococcus"),
+        ("Cetobacterium_A", "Cetobacterium"),
+        ("Methanobrevibacter_A", "Methanobrevibacter"),
+        ("Bacillota_A", "Bacillota"),
+        ("Clostridium_AM", "Clostridium"),
+        ("Acidithiobacillus_A", "Acidithiobacillus"),
+        ("Pseudomonas_E", "Pseudomonas"),
+        ("Ruminococcus_B", "Ruminococcus"),
+    ],
+)
+def test_a_suffixed_name_is_a_non_type_clade(gtdb, name, expected_base):
+    assert gtdb.non_type_clade(name) == expected_base
+
+
+@pytest.mark.parametrize(
+    "name",
+    [
+        # The type-anchored names themselves.
+        "Enterococcus",
+        "Pseudomonas",
+        "Bacillus",
+        "Leptospirillum",
+        # A binomial is not a genus name; the species path does not get this
+        # warning, and passing one here must not produce a false positive.
+        "Ruminococcus_B gnavus",
+        "Clostridium_AM drakei",
+        # Genuine names that merely contain characters the pattern touches.
+        "Candidatus Nitrosocosmicus",
+        "CAG-267",
+        "",
+    ],
+)
+def test_these_are_not_flagged(gtdb, name):
+    assert gtdb.non_type_clade(name) is None
+
+
+def test_the_warning_names_the_type_clade_and_its_support(gtdb):
+    """The message has to tell a curator what to compare against.
+
+    Numbers from the real Enterococcus case: the type clade is not a fringe
+    option, it drew 9904 genomes against the winner's 17011, which is exactly
+    the situation where a curator's judgement is worth having.
+    """
+    warning = gtdb._non_type_warning(
+        "Enterococcus_B", {"Enterococcus_B": 17011, "Enterococcus": 9904}
+    )
+
+    assert "Enterococcus_B is not the type-anchored clade" in warning
+    assert "reserves Enterococcus for" in warning
+    assert "9904 genomes" in warning
+    assert "#374" in warning
+
+
+def test_the_warning_distinguishes_a_type_clade_with_no_genomes(gtdb):
+    """Different curator action, so a different sentence.
+
+    If the type clade drew nothing, the NCBI name's genomes simply do not sit in
+    it — a stronger statement than a close call, and it should not read as one.
+    """
+    warning = gtdb._non_type_warning("Cetobacterium_A", {"Cetobacterium_A": 40})
+
+    assert "drew no genomes here" in warning
+    assert "0 genomes" not in warning, "a bare 0 reads like a close call that lost"
+
+
+def _ground(name: str) -> str:
+    """Run the real CLI against the real GTDB mapping."""
+    import subprocess
+
+    result = subprocess.run(
+        ["uv", "run", "python", str(SCRIPT), "--name", name],
+        capture_output=True,
+        text=True,
+        cwd=REPO,
+    )
+    return result.stdout
+
+
+@pytest.mark.integration
+def test_enterococcus_warns_and_still_returns_the_majority_answer():
+    """End-to-end on the one taxon in the KB where the rules actually disagree.
+
+    Flagging must not change the answer — that was the decision. If someone
+    later makes this prefer the type clade, the second assertion goes red and
+    they have to say so deliberately.
+    """
+    out = _ground("Enterococcus")
+    if "GTDB taxon" not in out:
+        pytest.skip("local GTDB mapping unavailable")
+
+    assert "NON-TYPE" in out, "the one real conflict in the KB produced no warning"
+    assert "g__Enterococcus_B" in out, "the majority answer was silently overridden"
+
+
+@pytest.mark.integration
+@pytest.mark.parametrize("name", ["Pseudomonas", "Acetobacter", "Leptospirillum", "Bacillus"])
+def test_the_four_that_agree_do_not_warn(name):
+    """The other four taxa where the denominators differ.
+
+    They agree with the type rule only because the majority happens to be the
+    type clade. A warning here would be a false positive on 4 of 5 cases, which
+    would train a curator to ignore it.
+    """
+    out = _ground(name)
+    if "GTDB taxon" not in out:
+        pytest.skip("local GTDB mapping unavailable")
+
+    assert "NON-TYPE" not in out, f"{name} agrees with the type rule but was flagged"