diff --git a/scripts/reclassify_hhrsh_storage.py b/scripts/reclassify_hhrsh_storage.py
index da4fbce82..952b205b7 100644
--- a/scripts/reclassify_hhrsh_storage.py
+++ b/scripts/reclassify_hhrsh_storage.py
@@ -1,12 +1,145 @@
 """One-time re-classification of HHRSH overrides funnelled into old storage.
 
-Placeholder — decision function stubbed; filled in GREEN.
+#1376 / ADR-0044: with no High Heat Retention archetype, the LLM classified
+"Electric Storage Systems: High heat retention storage heaters" to
+``"Electric storage heaters, old"`` (SAP 401) — scoring the *best* modern storage
+as the *worst* old large-volume type. An audit found 111 such rows.
+
+The live classifier now applies ``main_heating_guard`` deterministically (so new
+intakes are correct); this fixes the rows written before it. The **same guard**
+decides the correction here, so the backfill and the live path cannot drift.
+
+Updates the TEXT ``property_overrides.override_value`` (what the modelling reads —
+the immediate fix) unconditionally. The ``landlord_main_heating_system_overrides``
+``value`` classifier cache is a ``main_heating_system`` **pgEnum**; the new HHRSH
+archetype is an FE-owned value, so its cache write is **deferred** until the
+Drizzle migration adds it (the Class-A/B pattern).
+
+DRY-RUN BY DEFAULT: prints the counts it would change and writes nothing. Pass
+``--apply`` to execute inside a transaction. Idempotent — only rows whose stored
+value differs from the target member are touched.
 """
 
 from __future__ import annotations
 
+import argparse
 from collections.abc import Iterable
 
+from sqlalchemy import Connection, text
 
-def hhrsh_storage_corrections(stored: Iterable[tuple[str, str]]) -> dict[str, str]:
-    raise NotImplementedError
+from domain.epc.property_overrides.main_heating_guard import main_heating_guard
+from scripts.e2e_common import build_engine, load_env
+
+
+def hhrsh_storage_corrections(
+    stored: Iterable[tuple[str, str]],
+) -> dict[str, str]:
+    """``(description, stored override_value)`` → the HHRSH archetype value, for the
+    descriptions the main-heating guard resolves to HHRSH whose stored value is not
+    already it. Descriptions the guard defers and rows already on the target are
+    omitted, so re-running against corrected data is a no-op."""
+    corrections: dict[str, str] = {}
+    for description, value in stored:
+        member = main_heating_guard(description)
+        if member is not None and value != member.value:
+            corrections[description] = member.value
+    return corrections
+
+
+_DISTINCT = text(
+    """
+    SELECT DISTINCT lower(original_spreadsheet_description) AS description,
+                    override_value AS value
+    FROM property_overrides
+    WHERE override_component = 'main_heating_system'
+    """
+)
+_OVERRIDES_UPDATE = text(
+    """
+    UPDATE property_overrides
+       SET override_value = :new_value
+     WHERE override_component = 'main_heating_system'
+       AND lower(original_spreadsheet_description) = :description
+       AND override_value <> :new_value
+    """
+)
+_OVERRIDES_COUNT = text(
+    """
+    SELECT count(*) FROM property_overrides
+     WHERE override_component = 'main_heating_system'
+       AND lower(original_spreadsheet_description) = :description
+       AND override_value <> :new_value
+    """
+)
+_CACHE_UPDATE = text(
+    """
+    UPDATE landlord_main_heating_system_overrides
+       SET value = :new_value, updated_at = now()
+     WHERE lower(description) = :description
+       AND value::text <> :new_value
+    """
+)
+_ENUM_VALUES = text(
+    "SELECT e.enumlabel FROM pg_enum e JOIN pg_type t ON t.oid = e.enumtypid "
+    "WHERE t.typname = 'main_heating_system'"
+)
+
+
+def reclassify(conn: Connection, *, apply: bool) -> tuple[int, set[str]]:
+    """Re-map old-storage HHRSH overrides onto the high-heat-retention archetype.
+    Returns the number of ``property_overrides`` rows found and the set of target
+    values the live ``main_heating_system`` pgEnum does not yet carry (cache-
+    deferred until the FE migration)."""
+    stored = [(r.description, r.value) for r in conn.execute(_DISTINCT)]
+    enum_values = {r[0] for r in conn.execute(_ENUM_VALUES)}
+    total = 0
+    deferred: set[str] = set()
+    for description, new_value in hhrsh_storage_corrections(stored).items():
+        params = {"description": description, "new_value": new_value}
+        total += conn.execute(_OVERRIDES_COUNT, params).scalar() or 0
+        in_enum = new_value in enum_values
+        if not in_enum:
+            deferred.add(new_value)
+        if apply:
+            conn.execute(_OVERRIDES_UPDATE, params)
+            if in_enum:
+                conn.execute(_CACHE_UPDATE, params)
+    return total, deferred
+
+
+def main() -> None:
+    load_env()
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "--apply",
+        action="store_true",
+        help="execute the updates (default: dry-run, writes nothing)",
+    )
+    args = parser.parse_args()
+
+    engine = build_engine()
+    with engine.begin() as conn:
+        conn.execute(text("SET statement_timeout = 120000"))
+        total, deferred = reclassify(conn, apply=args.apply)
+
+    verb = "re-classified" if args.apply else "would re-classify"
+    print(
+        f"{verb} {total} high-heat-retention storage override row(s) off "
+        "'Electric storage heaters, old' onto the HHRSH archetype (SAP 409) — "
+        "property_overrides / TEXT, what the modelling reads."
+    )
+    if deferred:
+        print(
+            f"\n{len(deferred)} target value(s) NOT yet in the main_heating_system "
+            "pgEnum — their classifier-cache rows are deferred until the FE-repo "
+            "enum migration adds these members (property_overrides was still "
+            "updated, which is what the modelling reads):"
+        )
+        for value in sorted(deferred):
+            print(f"    {value!r}")
+    if not args.apply:
+        print("\nDRY-RUN — nothing written. Re-run with --apply to execute.")
+
+
+if __name__ == "__main__":
+    main()