diff --git a/api/tools/equipment.py b/api/tools/equipment.py
index d2dfb37..a1f63d4 100644
--- a/api/tools/equipment.py
+++ b/api/tools/equipment.py
@@ -18,6 +18,7 @@ import psycopg
 from psycopg.rows import dict_row
 
 from config import settings
+from contracts import ContractViolation
 
 log = logging.getLogger("tools.equipment")
 
@@ -56,12 +57,43 @@ def _connect() -> psycopg.Connection:
     )
 
 
+# PS_* IS NOT A NAMESPACE, AND ASKING FOR ONE IS AN ERROR - NOT AN EMPTY RESULT.
+#
+# The point list delivered in August carried names like PS_STN_WET_WELL_LEVEL
+# where the CI Server ITEM name belongs (AID.WRPS.STN.LEVEL). CI Server never
+# used them; they were a proposal derived from the PLC register map. A corrected
+# delivery arrived 2026-09-01 and the seed carries no PS_ key any more.
+#
+# Without this guard the old names simply match nothing, and the assistant says
+# "no records found" - which an operator reads as "the plant recorded nothing",
+# not as "you asked with a retired name". That is the exact confusion the four
+# namespaces exist to prevent, so it fails loudly instead.
+#
+# The four Modbus POLL GROUPS keep the prefix legitimately. They are groups, not
+# point or tag names, and nothing resolves an operator term onto one.
+_POLL_GROUPS = {"PS_STATUS_BITS", "PS_PUBLISHED", "PS_SETPOINTS", "PS_SIM_CONTROL"}
+_RETIRED_TAG = re.compile(r"^PS_[A-Z][A-Z0-9_]*$")
+
+
+def reject_retired_tag(term: str) -> None:
+    """Raise if `term` is one of the retired PS_* names. See the note above."""
+    candidate = term.strip().upper()
+    if _RETIRED_TAG.match(candidate) and candidate not in _POLL_GROUPS:
+        raise ContractViolation(
+            f"{candidate} is a retired name and is not a tag in this system. "
+            "It came from a superseded SCADA point list; CI Server never used it. "
+            "Use the CI Server item name instead, for example AID.WRPS.STN.LEVEL. "
+            "See db/seed/scada-source/README.md."
+        )
+
+
 def resolve(term: str, *, conn: psycopg.Connection | None = None) -> list[Resolved]:
     """Resolve one operator term to equipment and/or tags, best first.
 
     Returns every plausible match rather than picking one. An ambiguous term is
     a clarifying question, not a coin toss - agent.py surfaces the alternatives.
     """
+    reject_retired_tag(term)
     owned = conn is None
     conn = conn or _connect()
     try: