diff --git a/src/core/game3/save_schema_firered.lua b/src/core/game3/save_schema_firered.lua
index 9a7d5e83..934fce4d 100644
--- a/src/core/game3/save_schema_firered.lua
+++ b/src/core/game3/save_schema_firered.lua
@@ -347,7 +347,8 @@ function Schema.fromSaveTable(save)
     engine = save.engine or "game3",
     version = version,
     generation = tonumber(save.generation) or 3,
-    party = save.party or {},
+    -- A party saved with gaps (older PC builds) is closed up on load.
+    party = require("src.core.game3.storage").compactParty(save.party or {}),
     bag = bag,
     dex = save.dex or {},
     money = save.money or 0,
diff --git a/src/core/game3/storage.lua b/src/core/game3/storage.lua
index 289f3282..b1fa442e 100644
--- a/src/core/game3/storage.lua
+++ b/src/core/game3/storage.lua
@@ -32,6 +32,23 @@ local function script_store(session)
   return (Space and Space.store) or (session and session.store) or nil
 end
 
+--- Close gaps in the party in place so mons fill slots 1..n in order.
+-- pokefirered/src/pokemon.c CompactPartySlots
+function Storage.compactParty(party)
+  if type(party) ~= "table" then return party end
+  local keys = {}
+  for k, m in pairs(party) do
+    local n = tonumber(k)
+    if n and m ~= nil then keys[#keys + 1] = { n = n, k = k } end
+  end
+  table.sort(keys, function(a, b) return a.n < b.n end)
+  local mons = {}
+  for i, e in ipairs(keys) do mons[i] = party[e.k] end
+  for _, e in ipairs(keys) do party[e.k] = nil end
+  for i, m in ipairs(mons) do party[i] = m end
+  return party
+end
+
 --- Create a fresh Storage instance (14 boxes, 30 slots each, 50-item PC).
 function Storage.new()
   local storage = {
@@ -240,7 +257,9 @@ function Storage.moveMon(session, srcLoc, srcIdx, destLoc, destIdx, srcBox, dest
   if not srcMon then return false, "src_empty" end
 
   -- Cannot leave party empty if withdrawing/moving away
-  if srcLoc == "party" and destLoc == "box" and not destMon and #session.party <= 1 then
+  local partyCount = 0
+  for _, m in pairs(session.party) do if m ~= nil then partyCount = partyCount + 1 end end
+  if srcLoc == "party" and destLoc == "box" and not destMon and partyCount <= 1 then
     return false, "last_pokemon"
   end
 
@@ -259,20 +278,6 @@ function Storage.moveMon(session, srcLoc, srcIdx, destLoc, destIdx, srcBox, dest
   -- Assign to src
   if srcLoc == "party" then
     session.party[srcIdx] = destMon
-    -- Clean up trailing nils in party array if moved without swap
-    if not destMon and srcIdx > #session.party then
-      local keys = {}
-      for k in pairs(session.party) do
-        if type(k) == "number" then keys[#keys + 1] = k end
-      end
-      table.sort(keys)
-      local newParty = {}
-      for _, k in ipairs(keys) do
-        local m = session.party[k]
-        if m then newParty[#newParty + 1] = m end
-      end
-      session.party = newParty
-    end
   elseif srcLoc == "box" then
     local box = storage.boxes[srcBox or storage.currentBox]
     box.mons[srcIdx] = destMon
@@ -297,6 +302,8 @@ function Storage.moveMon(session, srcLoc, srcIdx, destLoc, destIdx, srcBox, dest
   elseif srcLoc=="party" then
     Q.event(session,"DepositedMonInPC",{D0=srcName,D1=dstBoxName})
   else Q.event(session,"WithdrewMonFromPC",{D0=srcBoxName,D1=srcName}) end
+  -- A mon moved out of (or into) the middle of the party must not leave a gap.
+  Storage.compactParty(session.party)
   return true
 end
 
diff --git a/src/ui/game3/box_storage_ui.lua b/src/ui/game3/box_storage_ui.lua
index c9b60f96..a8fe387b 100644
--- a/src/ui/game3/box_storage_ui.lua
+++ b/src/ui/game3/box_storage_ui.lua
@@ -153,6 +153,8 @@ function BoxStorageUI.show(opts)
   BoxStorageUI._actionSource = nil
   BoxStorageUI._actionTarget = nil
   local storage = Storage.ensure(BoxStorageUI._session)
+  -- Repair a party left with gaps by an older build before any slot is indexed.
+  if BoxStorageUI._session then Storage.compactParty(BoxStorageUI._session.party) end
   -- pokefirered/src/pokemon_storage_system_tasks.c:426
   BoxStorageUI._lastUsedBox = storage and ((tonumber(storage.currentBox) or 1) - 1) or nil
 
@@ -379,6 +381,8 @@ function BoxStorageUI.handleInput(input)
               se(se_id("SE_BAG_POCKET"))
             end
           end
+          -- pokefirered/src/pokemon_storage_system_tasks.c SetUpHidePartyMenu -> CompactPartySlots
+          Storage.compactParty(party)
         elseif mon then
           BoxStorageUI._actionSource = "party"
           BoxStorageUI._actionTarget = { mon = mon, loc = "party", boxId = nil, slot = pIdx }
diff --git a/src/ui/game3/party_menu.lua b/src/ui/game3/party_menu.lua
index 24dcff19..5061f113 100644
--- a/src/ui/game3/party_menu.lua
+++ b/src/ui/game3/party_menu.lua
@@ -2490,6 +2490,16 @@ local function slot_description(slot, mon)
   local item = PartyMenu._item
   if not item or PartyMenu._battle then return nil end
   if PartyMenu.mode ~= "use" and PartyMenu.mode ~= "message" then return nil end
+  -- pokefirered/src/party_menu.c:856 TM/HM -> DisplayPartyPokemonDataToTeachMove
+  if ItemsData.isTm(item) then
+    -- pokefirered/src/party_menu.c:4760 CanMonLearnTMTutor
+    if Pokemon.isEgg(mon) then return desc_text("NOT_ABLE_2") end
+    local moveId = Pokemon.moveFromTmItem(item)
+    local species = tonumber(mon.species or mon.speciesId)
+    if not moveId or not Pokemon.canLearnTmItem(species, item) then return desc_text("NOT_ABLE_2") end
+    if Pokemon.knowsMove(mon, moveId) then return desc_text("LEARNED") end
+    return desc_text("ABLE_2")
+  end
   if not is_evolution_stone(item) then return nil end
   local Evolution = require("src.core.game3.evolution")
   if Evolution.itemCheck(mon, item) then return nil end
diff --git a/tests/game3_pc_party_gap_2494_test.lua b/tests/game3_pc_party_gap_2494_test.lua
new file mode 100644
index 00000000..0e34b53c
--- /dev/null
+++ b/tests/game3_pc_party_gap_2494_test.lua
@@ -0,0 +1,96 @@
+#!/usr/bin/env luajit
+-- #2494: moving a party mon out of the middle of the party in the PC left a
+-- hole, so later slots showed as empty in battle and could not be filled.
+-- pokefirered/src/pokemon.c CompactPartySlots keeps the party packed.
+
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+require("tests.game3_cache").stubSpeciesNames()
+require("tests.fixture_data.game3_items").install()
+package.loaded["src.core.game3.rom_text"] = {
+  plain = function(key) return key end, box = function(key) return key end,
+  ascii = function(key) return key end, has = function() return true end,
+  key = function(n, i) return n .. "[" .. i .. "]" end,
+  at = function(n, i) return n .. "[" .. i .. "]" end,
+  count = function() return 0 end, list = function() return {} end,
+  lazy = function(map) return setmetatable({}, { __index = function(_, k) return map[k] end }) end,
+}
+
+local Storage = require("src.core.game3.storage")
+local BoxStorageUI = require("src.ui.game3.box_storage_ui")
+
+local failed = 0
+local function check(cond, msg)
+  if cond then
+    print("[ok] " .. msg)
+  else
+    failed = failed + 1
+    print("[FAIL] " .. msg)
+  end
+end
+
+local function mon(species)
+  return { species = species, speciesId = species, level = 5, hp = 20, maxHp = 20, moves = { 33 }, pp = { 35 } }
+end
+
+local function packed(party, n)
+  for i = 1, n do
+    if party[i] == nil then return false end
+  end
+  for k in pairs(party) do
+    if type(k) ~= "number" or k > n then return false end
+  end
+  return true
+end
+
+print("[test] 1. moving slot 3 of 6 into a box closes the gap")
+do
+  local session = { party = { mon(1), mon(4), mon(7), mon(10), mon(13), mon(16) } }
+  local party = session.party
+  Storage.ensure(session)
+  local ok = Storage.moveMon(session, "party", 3, "box", 1, nil, 1)
+  check(ok == true, "the move succeeds")
+  check(session.party == party, "the party table keeps its identity")
+  check(packed(session.party, 5), "the party is packed into slots 1..5")
+  check(session.party[3].species == 10 and session.party[5].species == 16,
+    "later mons shift up in order")
+end
+
+print("[test] 2. placing a box mon into an empty far party slot packs it")
+do
+  local session = { party = { mon(1), mon(4) } }
+  Storage.ensure(session)
+  BoxStorageUI.show({ session = session })
+  local storage = Storage.ensure(session)
+  storage.boxes[1].mons[1] = mon(25)
+  BoxStorageUI.mode = "party_drawer"
+  BoxStorageUI.drawerOpen = true
+  BoxStorageUI.holdingMon = storage.boxes[1].mons[1]
+  BoxStorageUI.holdingSource = { loc = "box", boxId = 1, slot = 1 }
+  BoxStorageUI.partyCursor = 6
+  BoxStorageUI.handleInput({
+    wasPressed = function(_, k) return k == "a" end,
+    isDown = function(_, k) return k == "a" end,
+  })
+  check(packed(session.party, 3), "the party is packed into slots 1..3")
+  check(session.party[3] and session.party[3].species == 25, "the placed mon lands in slot 3")
+  check(storage.boxes[1].mons[1] == nil, "the box slot is emptied")
+  BoxStorageUI.close()
+end
+
+print("[test] 3. a party already saved with a gap is repaired")
+do
+  local party = { mon(1), mon(4), nil, mon(10), mon(13) }
+  party[3] = nil
+  Storage.compactParty(party)
+  check(packed(party, 4), "numeric gaps close")
+  local stringy = { ["1"] = mon(1), ["2"] = mon(4), ["4"] = mon(10) }
+  Storage.compactParty(stringy)
+  check(packed(stringy, 3) and stringy[3].species == 10, "string-keyed slots close too")
+end
+
+if failed > 0 then
+  print(string.format("[FAIL] %d check(s) failed", failed))
+  os.exit(1)
+end
+print("[PASS] game3_pc_party_gap_2494")
diff --git a/tests/game3_tm_able_desc_2520_test.lua b/tests/game3_tm_able_desc_2520_test.lua
new file mode 100644
index 00000000..6743dee9
--- /dev/null
+++ b/tests/game3_tm_able_desc_2520_test.lua
@@ -0,0 +1,80 @@
+#!/usr/bin/env luajit
+-- #2520: choosing a TM/HM from the bag opens the party menu without the
+-- ABLE! / NOT ABLE! / LEARNED labels on each slot.
+-- pokefirered/src/party_menu.c:856 DisplayPartyPokemonDataForMoveTutorOrEvolutionItem
+-- -> DisplayPartyPokemonDataToTeachMove.
+
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+require("tests.game3_cache").stubSpeciesNames()
+require("tests.fixture_data.game3_items").install()
+
+-- pokefirered/src/data/party_menu.h:634 sDescriptionStringTable
+local DESCRIPTIONS = { [0] = "NO USE", "ABLE", "FIRST", "SECOND", "THIRD", "ABLE",
+  "NOT ABLE", "ABLE!", "NOT ABLE!", "LEARNED" }
+package.loaded["src.core.game3.rom_text"] = {
+  plain = function(key) return key end, box = function(key) return key end,
+  ascii = function(key) return key end, has = function() return true end,
+  key = function(n, i) return n .. "[" .. tostring(i) .. "]" end,
+  at = function(n, i)
+    if n == "sDescriptionStringTable" then return DESCRIPTIONS[i] end
+    return n .. "[" .. tostring(i) .. "]"
+  end,
+  count = function() return 0 end, list = function() return {} end,
+  lazy = function(map) return setmetatable({}, { __index = function(_, k) return map[k] end }) end,
+}
+
+local ItemsData = require("src.core.game3.items_data")
+local Pokemon = require("src.core.game3.pokemon")
+
+local TM06, TOXIC = 294, 92
+local BULBASAUR, CHARMANDER, GEODUDE = 1, 4, 74
+
+ItemsData.isTm = function(id) return id == TM06 end
+Pokemon.moveFromTmItem = function(id) return id == TM06 and TOXIC or nil end
+Pokemon.canLearnTmItem = function(species) return species ~= CHARMANDER end
+
+local PartyMenu = require("src.ui.game3.party_menu")
+
+local failed = 0
+local function check(cond, msg)
+  if cond then
+    print("[ok] " .. msg)
+  else
+    failed = failed + 1
+    print("[FAIL] " .. msg)
+  end
+end
+
+local function mon(species, moves)
+  return { species = species, speciesId = species, level = 10, hp = 20, maxHp = 20,
+    moves = moves or { 33 }, pp = { 35 } }
+end
+
+local party = {
+  mon(BULBASAUR),
+  mon(CHARMANDER),
+  mon(GEODUDE, { 33, TOXIC }),
+  { species = BULBASAUR, speciesId = BULBASAUR, isEgg = true, hp = 0, maxHp = 0, moves = {} },
+}
+PartyMenu.show(party, nil, { mode = "use", item = TM06 })
+PartyMenu._item = TM06
+PartyMenu.mode = "use"
+
+check(PartyMenu.slotDescription(1) == "ABLE!",
+  "a compatible mon reads ABLE!, got " .. tostring(PartyMenu.slotDescription(1)))
+check(PartyMenu.slotDescription(2) == "NOT ABLE!",
+  "an incompatible mon reads NOT ABLE!, got " .. tostring(PartyMenu.slotDescription(2)))
+check(PartyMenu.slotDescription(3) == "LEARNED",
+  "a mon that knows the move reads LEARNED, got " .. tostring(PartyMenu.slotDescription(3)))
+check(PartyMenu.slotDescription(4) == "NOT ABLE!",
+  "an egg reads NOT ABLE!, got " .. tostring(PartyMenu.slotDescription(4)))
+
+PartyMenu._item = 13 -- a Potion: no label
+check(PartyMenu.slotDescription(1) == nil, "a non-TM item shows no label")
+
+if failed > 0 then
+  print(string.format("[FAIL] %d check(s) failed", failed))
+  os.exit(1)
+end
+print("[PASS] game3_tm_able_desc_2520")