@@ -2,6 +2,105 @@
 
 Decisions made outside the Google Drive documents, newest first.
 
+## 2026-10-28 — No enchantment lists a tag twice, and a test refuses a repeated tag in any generated table (#1823)
+
+**Affects:** five cells of the "Enchantments" sheet of `docs/All_Things_Cataclysm.xlsx` (I5, I167, I182, I193, D378) and
+the lines they generate in `game/Data/EnchantmentsNegative.csv` (5, 167, 182, 193) and
+`game/Data/EnchantmentsPositive.csv` (377); a new test, `tools/tests/test_no_tag_column_repeats_a_tag.py`; this file. No
+C++. The two enchantment DataTable assets are rebuilt in the window, because their Tags text changes. **Closes
+[#1823](https://github.com/sdubois777/Cataclysm/issues/1823).**
+
+### SAID FIRST
+
+- **NOTHING CHANGES IN PLAY.** An enchantment's `Tags` is a plain `FString` (`FCataclysmEnchantmentRow`,
+  `game/Source/Cataclysm/Data/CataclysmDataRows.h`), not a tag container. The one reader in game code,
+  `UCataclysmDropRoll::EnchantmentSuitsSlot` (`CataclysmDropRoll.cpp`), splits it and looks only for tags beginning
+  `Item.Slot.`; these five repeat `Slot.Ultimate` or `Slot.Movement`, and a repeat gives the same answer either way. No
+  tooltip or item code reads it, and scoping reads the effect rows' `RequiredTags`, which repeat nothing. The issue said
+  the second copy "is dropped on import"; that is not the mechanism, though its conclusion holds.
+- **THE REPEATS WERE IN THE WORKBOOK**, typed that way, not added by the generator.
+
+### THE RULING, VERBATIM (the coordinating session, 2026-10-28)
+
+> Coordinator, #1823:
+> (c) The check is a test, as you recommend. It runs over every tag column in every generated game/Data CSV, found by
+> column name, and names each row and its repeated tag. The generator stays unchanged: a test catches this before merge,
+> and it covers new tables without being edited. Prove it with prove_guard in a copy by re-adding one duplicate.
+> GRANT on fix/no-tag-twice-in-an-enchantment from e0351fdcd, in docs/All_Things_Cataclysm.xlsx, exactly five cells on
+> the "Enchantments" sheet: I5, I167, I182, I193 and D378. Remove only the second copy of the repeated tag and keep the
+> order, to the values in your trial. No other cell changes. The grant runs from the edit until the branch merges.
+
+### THE FIVE CELLS (commit `f0ebf746f`)
+
+| Cell | Row | Before | After |
+|---|---|---|---|
+| I5 | `Negative_Ultimate_cooldowns_increased_by_100_500` | `Slot.Ultimate, Slot.Ultimate` | `Slot.Ultimate` |
+| I167 | `Negative_Movement_abilities_have_50_increased_cooldown` | `Slot.Movement, Slot.Movement` | `Slot.Movement` |
+| I182 | `Negative_After_you_use_a_movement_ability_you_lose_50_mo` | `Slot.Movement, Slot.Movement, Stat.Utility.Movespeed` | `Slot.Movement, Stat.Utility.Movespeed` |
+| I193 | `Negative_Your_own_ultimate_ability_is_disabled` | `Slot.Ultimate, Slot.Ultimate` | `Slot.Ultimate` |
+| D378 | `Positive_Warlord_s_Will_10_Piece_Bonus_Every_30_second` | `Stat.Utility.Movespeed, Slot.Movement, Slot.Movement, Keyword.Consume` | `Stat.Utility.Movespeed, Slot.Movement, Keyword.Consume` |
+
+One script run asserted each old value and every sheet's shape before writing. The generator then changed exactly
+these five lines (Negative 5, 167, 182, 193; Positive 377), each only in its Tags field, with every table's line count
+unchanged, and `--check` passed. A trial in a git-archive copy at `9293573bf` and again at `e0351fdcd` gave the same
+five lines. Measured across every tag column in `game/Data` at `e0351fdcd`, no other row repeated a tag
+(EnchantmentEffects RequiredTags 707 rows, PassiveEffects RequiredTags 325, WeaponSkills Tags 403, MinionTypes Tags 9,
+MinionScaling RequiresTag 2, ElementVisuals ElementTag 8: none).
+
+### THE TEST
+
+`tools/tests/test_no_tag_column_repeats_a_tag.py`, three tests:
+
+- `test_the_scan_reads_every_tag_column_it_must`: the scope, read first. Six columns the scan must find (the two
+  enchantment Tags, EnchantmentEffects and PassiveEffects RequiredTags, WeaponSkills and MinionTypes Tags), so a renamed
+  column cannot leave the check reading nothing.
+- `test_no_row_lists_a_tag_twice`: every column whose name contains "tag", in every CSV under `game/Data`; a failure
+  names the table, column, row and repeated tag.
+- `test_a_repeat_is_found_and_a_single_tag_is_not`: the helper on made-up cells, including spacing.
+
+Run on the tree before the edit (`e0351fdcd`), the second test failed naming exactly the five rows above.
+
+### THE PROOF
+
+`tools/prove_guard.py` `break_and_run`, in a git-archive copy outside the repository: the line
+`Negative_Ultimate_cooldowns_increased_by_100_500,...,2.0,Slot.Ultimate,True,` of `EnchantmentsNegative.csv` (counted
+once) given back its repeat, `"Slot.Ultimate, Slot.Ultimate"`. Printed: "PROVED: 1 failed, 2 passed in 0.15s |
+restored: 3 passed in 0.06s"; named_failures
+`tools/tests/test_no_tag_column_repeats_a_tag.py::test_no_row_lists_a_tag_twice`.
+
+### JUDGEMENTS OF MY OWN, WITH THE OPTION NOT TAKEN
+
+- **The scan reads the generated CSVs, not the workbook**, because the CSVs are what the game reads and every tag
+  column reaches one. Not taken: reading the sheets, whose column layout differs per sheet.
+- **A column is a tag column when its name contains "tag"**, which today finds eight columns in eight tables. Not
+  taken: a fixed list, which a new table would escape.
+
+### NO GENRE SOURCE
+
+None. This is authoring hygiene, not a mechanic.
+
+### FOR THE OWNER'S PLAY-CHECK LIST
+
+- Nothing to see: no enchantment behaves differently.
+
+### THE WINDOW'S RUN, t183w
+
+Window t183w, run 2026-10-28 under the lock as `enchant-t183w`, at `abcd2e564` on development `db73850a7` (moved from
+`285fae4ce` on `e0351fdcd` as `fix/no-tag-twice-in-an-enchantment-1`; the workbook blob, the zero-context patch ids of
+the CSVs and the test file, and the hash of this file's changed lines matched for all three commits). Free memory
+immediately before the lock, at 13:39:39, was 11,233 MB, against the floor of 10 GiB (10,240 MB). No C++ changed, so
+no new Unreal test and no C++ proof. Every step exited 0:
+
+| Step | Result |
+|---|---|
+| The build | "35 actions, 32 files compiled" (development's own C++ from #2540, not yet built in this worktree) |
+| The DataTable assets | exactly `DT_EnchantmentsNegative.uasset`, `DT_EnchantmentsPositive.uasset` and `datatable_asset_sources.json` changed; committed as `36908a535` |
+| The whole Unreal suite | "4343 tests performed, 4343 succeeded, 0 failed"; 4343 declared, gap 0 |
+| Memory | `tests=4950 peak_used_virtual_mb=8107 final_used_virtual_mb=7772` |
+| Python of record | "7015 passed, 8 skipped"; JUnit 7023 tests, 0 failures, 0 errors, 8 skipped (the asset-hash test passes after the asset commit); ruff "All checks passed!" |
+
+---
+
 ## 2026-10-28 — A thrall explodes under Every One Bursts: 3 m, three of its own blows, raised by Volatile (#2540)
 
 **Affects:** `CataclysmMinion.h` and `.cpp` (`ThrallExplosionDamage`, `ThrallBurst` and two constants),
 
@@ -1,3 +1,3 @@
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+size 140780
@@ -2,7 +2,7 @@ Name,Effect,EnchantmentType,Weight,Tags,IsNegative,RollsDown
 Negative_Can_t_use_a_basic_attack,Can’t use a basic attack,Generic,0.0,Scope.BasicOnly,True,
 Negative_80_99_of_your_health_is_reserved,80%-99% of your health is reserved,Generic,1.0,Stat.Defense.Life,True,
 Negative_You_lose_1_4_max_resistances_for_every_100_000,"You lose 1-4% max resistances for every 100,000 - 500,000 kills",Generic,3.0,Stat.Defense.Resist,True,2
-Negative_Ultimate_cooldowns_increased_by_100_500,Ultimate cooldowns increased by 100%-500%,Generic,2.0,"Slot.Ultimate, Slot.Ultimate",True,
+Negative_Ultimate_cooldowns_increased_by_100_500,Ultimate cooldowns increased by 100%-500%,Generic,2.0,Slot.Ultimate,True,
 Negative_You_have_no_armor,You have no armor,Generic,1.0,Stat.Defense.Armor,True,
 Negative_DoTs_deal_double_damage_to_you,DoTs deal double damage to you,Generic,2.0,Keyword.DoT.Generic,True,
 Negative_You_lose_15_of_your_max_hp_every_5_seconds,You lose 15% of your max hp every 5 seconds,Generic,1.0,Stat.Defense.Life,True,
@@ -164,7 +164,7 @@ Negative_Can_t_inflict_bleeding,Can't inflict bleeding,Generic,4.0,Keyword.DoT.B
 Negative_You_have_25_50_less_crit_chance,You have 25%-50% less crit chance,Generic,3.0,Stat.Offense.Crit,True,
 Negative_Energy_shield_can_now_be_effected_by_bleed,Energy shield can now be effected by bleed,Generic,4.0,"Stat.Defense.EnergyShield, Keyword.DoT.Bleed",True,
 Negative_Cannot_evade_melee_attacks,Cannot evade melee attacks,Generic,4.0,Stat.Defense.Evasion,True,
-Negative_Movement_abilities_have_50_increased_cooldown,Movement abilities have 50% increased cooldown,Generic,4.0,"Slot.Movement, Slot.Movement",True,
+Negative_Movement_abilities_have_50_increased_cooldown,Movement abilities have 50% increased cooldown,Generic,4.0,Slot.Movement,True,
 Negative_Movement_abilities_cost_20_50_of_your_maximum,Movement abilities cost 20%-50% of your maximum mana,Generic,4.0,"Slot.Movement, Stat.Resource.Mana",True,
 Negative_Cooldowns_are_increased_by_30_50,Cooldowns are increased by 30%-50%,Generic,3.0,Scope.Global,True,
 Negative_You_take_10_20_of_the_damage_you_reflect,You take 10%-20% of the damage you reflect,Generic,4.0,,True,
@@ -179,7 +179,7 @@ Negative_Your_cooldown_abilities_have_a_25_chance_to_dea,Your cooldown abilities
 Negative_Your_cooldowns_are_increased_by_100_200,Your cooldowns are increased by 100%-200%,Generic,2.0,,True,
 Negative_Lose_5_15_attack_speed,Lose 5%-15% attack speed,Generic,4.0,Stat.Offense.Speed,True,
 Negative_You_have_10_20_less_chance_to_evade,You have 10%-20% less chance to evade,Generic,4.0,Stat.Defense.Evasion,True,
-Negative_After_you_use_a_movement_ability_you_lose_50_mo,After you use a movement ability you lose 50% movespeed for 3 seconds,Generic,4.0,"Slot.Movement, Slot.Movement, Stat.Utility.Movespeed",True,
+Negative_After_you_use_a_movement_ability_you_lose_50_mo,After you use a movement ability you lose 50% movespeed for 3 seconds,Generic,4.0,"Slot.Movement, Stat.Utility.Movespeed",True,
 Negative_Ranged_skills_have_20_35_reduced_projectile_sp,Ranged skills have 20%-35% reduced projectile speed,Generic,4.0,"Type.Ranged, Type.Projectile",True,
 Negative_Your_movement_speed_is_reduced_by_10,Your movement speed is reduced by 10%,Set,5.0,Stat.Utility.Movespeed,True,
 Negative_Minion_maximum_health_is_reduced_by_50,Minion maximum health is reduced by 50%,Set,6.0,Stat.Defense.Life,True,
@@ -190,7 +190,7 @@ Negative_Melee_damage_is_reduced_by_50,Melee damage is reduced by 50%,Set,10.0,T
 Negative_Ranged_attacks_deal_20_more_damage_to_you,Ranged attacks deal 20% more damage to you,Set,11.0,Type.Projectile,True,
 Negative_Your_direct_damage_is_reduced_by_25,Your direct damage is reduced by 25%,Set,12.0,,True,
 Negative_You_have_no_health_mana_es_regen,You have no health/mana/es regen,Set,13.0,"Stat.Recovery.Regen, Stat.Resource.Mana, Stat.Defense.EnergyShield",True,
-Negative_Your_own_ultimate_ability_is_disabled,Your own ultimate ability is disabled,Set,14.0,"Slot.Ultimate, Slot.Ultimate",True,
+Negative_Your_own_ultimate_ability_is_disabled,Your own ultimate ability is disabled,Set,14.0,Slot.Ultimate,True,
 Negative_Your_health_is_reduced_by_10,Your health is reduced by 10%,Set,16.0,Stat.Defense.Life,True,
 Negative_Your_movement_speed_is_reduced_by_10_1,Your movement speed is reduced by 10%,Set,17.0,Stat.Utility.Movespeed,True,
 Negative_All_of_your_life_regeneration_effects_are_reduce,All of your life regeneration effects are reduced by 50%,Set,18.0,,True,
 
@@ -374,7 +374,7 @@ Positive_Divine_Retribution_6_Piece_Bonus_When_your_en,"Divine Retribution (6-Pi
 Positive_Divine_Retribution_10_Piece_Bonus_Every_5_sec,"Divine Retribution (10-Piece Bonus): Every 5 seconds, you gain a stack of 'Sanctified Power.' When you block an attack, you consume all stacks of 'Sanctified Power' and all of your skills are instantly refreshed. The bonus is permanent for the rest of the dungeon",Set,16.0,"Stat.Defense.Block, Keyword.Consume, Trigger.OnBlock",False,
 Positive_Warlord_s_Will_2_Piece_Bonus_Your_armor_is_in,Warlord's Will (2-Piece Bonus): Your armor is increased by 25%,Set,17.0,Stat.Defense.Armor,False,
 Positive_Warlord_s_Will_6_Piece_Bonus_When_you_take_da,"Warlord's Will (6-Piece Bonus): When you take damage, you have a 10% chance to summon a ""Warhound"" to fight for you for a short duration. The Warhound taunts enemies and deals damage based on your armor",Set,17.0,"Type.Minion, Stat.Defense.Armor",False,
-Positive_Warlord_s_Will_10_Piece_Bonus_Every_30_second,"Warlord's Will (10-Piece Bonus): Every 30 seconds, you gain a stack of 'Tactical Advantage.' When you use a movement ability, you consume all stacks of 'Tactical Advantage' and gain 100% more movement speed and 50% more damage for 5 seconds. This bonus scales with the number of enemies in the area: 10% more damage for each enemy within 8 meters, up to 5.",Set,17.0,"Stat.Utility.Movespeed, Slot.Movement, Slot.Movement, Keyword.Consume",False,
+Positive_Warlord_s_Will_10_Piece_Bonus_Every_30_second,"Warlord's Will (10-Piece Bonus): Every 30 seconds, you gain a stack of 'Tactical Advantage.' When you use a movement ability, you consume all stacks of 'Tactical Advantage' and gain 100% more movement speed and 50% more damage for 5 seconds. This bonus scales with the number of enemies in the area: 10% more damage for each enemy within 8 meters, up to 5.",Set,17.0,"Stat.Utility.Movespeed, Slot.Movement, Keyword.Consume",False,
 Positive_Reaper_s_Embrace_2_Piece_Bonus_You_gain_10_m,Reaper's Embrace (2-Piece Bonus): You gain 10% more life from all sources,Set,18.0,Stat.Defense.Life,False,
 Positive_Reaper_s_Embrace_6_Piece_Bonus_When_a_minion,"Reaper's Embrace (6-Piece Bonus): When a minion or pet dies, it leaves behind a ""Soul"" that can be picked up. Picking up a Soul grants a stack of Soul Strike that increases your damage by 10% for 5 seconds. Max 10 stacks.",Set,18.0,Type.Minion,False,
 Positive_Reaper_s_Embrace_10_Piece_Bonus_For_each_stac,"Reaper's Embrace (10-Piece Bonus): For each stack of Soul Strike you gain 5% cull on hit. Killing an enemy instanly spawns one of your minions, up to your max",Set,18.0,Type.Minion,False,
@@ -59,13 +59,13 @@
       "asset": "DT_EnchantmentsNegative",
       "csv": "EnchantmentsNegative.csv",
       "rows": 196,
-      "csv_sha256": "0125478821c0ffe6a7cf4e4c70e6eccbb542849322c7d312cdbdb3e9217c10f4"
+      "csv_sha256": "d498793734a213fc2197b00a2dc9d07f2032f25044e2d689e1d6886fbe6a8ea7"
     },
     {
       "asset": "DT_EnchantmentsPositive",
       "csv": "EnchantmentsPositive.csv",
       "rows": 379,
-      "csv_sha256": "72388c6166670e1aaeb72d43e2bb3d5b9b54042a1235bcbb92220941e9e4f7e0"
+      "csv_sha256": "7f5dc0ae130ff410db4db6d0232c7892f5993934307efde06ba3f700bf8c987d"
     },
     {
       "asset": "DT_EnemyArchetypes",
 
@@ -0,0 +1,98 @@
+"""No row of any generated table lists the same tag twice in a tag column.
+
+WHY THIS EXISTS. Issue #1823. Five enchantment rows carried a repeated tag, all of
+them typed into the design workbook that way: "Slot.Ultimate, Slot.Ultimate" and
+"Slot.Movement, Slot.Movement". It changed nothing in play -- an enchantment's
+`Tags` is a plain string, and the one reader in the game,
+`UCataclysmDropRoll::EnchantmentSuitsSlot`, gives the same answer for a tag listed
+once or twice -- but it meant the column could not be read as a count of anything,
+and nothing reported it. The five cells were corrected in the same change as this
+test.
+
+WHAT IS CHECKED. Every CSV under `game/Data`, which the generator writes from the
+workbook and the game reads, and in each every column whose name contains "tag".
+The columns are FOUND BY NAME rather than listed, so a new table with a tag column
+is covered without this file being edited. Ruled by the coordinating session on
+2026-10-28: a test, and not a refusal in `tools/generate_datatables.py`, because
+this catches it before merge and covers new tables on its own.
+
+A failure names each table, column, row and repeated tag.
+"""
+
+from __future__ import annotations
+
+import collections
+import csv
+import pathlib
+
+REPO_ROOT = pathlib.Path(__file__).resolve().parents[2]
+DATA = REPO_ROOT / "game" / "Data"
+
+#: THE COLUMNS THIS MUST AT LEAST READ, so a renamed column or a moved folder
+#: cannot leave the check reading nothing and passing. Each held a tag list when
+#: this was written (issue #1823); the scan is not limited to them.
+MUST_READ = {
+    ("EnchantmentsPositive.csv", "Tags"),
+    ("EnchantmentsNegative.csv", "Tags"),
+    ("EnchantmentEffects.csv", "RequiredTags"),
+    ("PassiveEffects.csv", "RequiredTags"),
+    ("WeaponSkills.csv", "Tags"),
+    ("MinionTypes.csv", "Tags"),
+}
+
+
+def repeated_tags(cell: str) -> list[str]:
+    """The tags a comma-separated cell lists more than once, in first-seen order."""
+    tags = [tag.strip() for tag in (cell or "").split(",") if tag.strip()]
+    return [tag for tag, count in collections.Counter(tags).items() if count > 1]
+
+
+def tag_columns() -> dict[tuple[str, str], list[dict[str, str]]]:
+    """Every (table, column) whose column name contains "tag", with the table's rows."""
+    found: dict[tuple[str, str], list[dict[str, str]]] = {}
+    for path in sorted(DATA.glob("*.csv")):
+        with path.open(encoding="utf-8-sig", newline="") as handle:
+            rows = list(csv.DictReader(handle))
+        if not rows:
+            continue
+        for column in rows[0]:
+            if column and "tag" in column.lower():
+                found[(path.name, column)] = rows
+    return found
+
+
+def test_the_scan_reads_every_tag_column_it_must():
+    """THE SCOPE, checked first, so the test below cannot pass by reading nothing."""
+    read = set(tag_columns())
+    missing = sorted(MUST_READ - read)
+    assert not missing, (
+        f"These tag columns were not found under {DATA}: {missing}. A column was "
+        "renamed or a table moved; update MUST_READ, or the check is reading less "
+        "than it says.")
+
+
+def test_no_row_lists_a_tag_twice():
+    wrong = []
+    for (table, column), rows in tag_columns().items():
+        for row in rows:
+            repeats = repeated_tags(row[column])
+            if repeats:
+                key = next(iter(row.values()), "")
+                wrong.append(f"{table} {column}, row {key}: {', '.join(repeats)}")
+    assert not wrong, (
+        "These rows list a tag more than once. The tag is written twice in the "
+        "design workbook, docs/All_Things_Cataclysm.xlsx; remove the second copy "
+        "there and regenerate:\n  " + "\n  ".join(wrong))
+
+
+def test_a_repeat_is_found_and_a_single_tag_is_not():
+    """The helper, on made-up cells, so no change to the real tables can hide a
+    mistake in it."""
+    assert repeated_tags("Slot.Ultimate, Slot.Ultimate") == ["Slot.Ultimate"]
+    assert repeated_tags(
+        "Stat.Utility.Movespeed, Slot.Movement, Slot.Movement, Keyword.Consume"
+    ) == ["Slot.Movement"]
+    assert repeated_tags("Slot.Movement, Stat.Utility.Movespeed") == []
+    assert repeated_tags("") == []
+    # SPACING DOES NOT HIDE A REPEAT, since the cells are written "A, B".
+    assert repeated_tags("Slot.Heavy,Slot.Heavy ") == ["Slot.Heavy"]