diff --git a/autoceiling.lua b/autoceiling.lua
new file mode 100644
index 000000000..67b4877cc
--- /dev/null
+++ b/autoceiling.lua
@@ -0,0 +1,237 @@
+-- AutoCeiling.lua
+-- Purpose: flood-fill the connected dug area on the cursor z-level (z0)
+-- and place constructed floors directly above (z0+1). When the buildingplan
+-- plugin is enabled, planned constructions are created. Otherwise we fall back
+-- to native construction designations so dwarves get immediate jobs.
+-- The script skips tiles that already have a player-made construction or
+-- any existing building at the target tile on z0+1.
+
+-------------------------
+-- Configuration defaults
+-------------------------
+local CONFIG = {
+  MAX_FILL_TILES = 2000,   -- positive integer; safety limit
+  ALLOW_DIAGONALS = false, -- set true to allow 8-way fill
+  MAX_LIMIT_HARD = 4000  -- hard clamp to avoid runaway fills
+}
+
+-------------------------
+-- Utilities and guards
+-------------------------
+local function err(msg) qerror('AutoCeiling: ' .. tostring(msg)) end
+
+local function xyz2pos(x, y, z)
+  return { x = x, y = y, z = z }
+end
+
+-- Cache frequently used modules/tables for readability
+local maps          = dfhack.maps
+local constructions = dfhack.constructions
+local buildings     = dfhack.buildings
+local tattrs        = df.tiletype.attrs
+
+-------------------------
+-- World and map helpers
+-------------------------
+local function in_bounds(x, y, z)
+  return maps.isValidTilePos(x, y, z)
+end
+
+local function get_tiletype(x, y, z)
+  return maps.getTileType(x, y, z)
+end
+
+local function tile_shape(tt)
+  if not tt then return nil end
+  local a = tattrs[tt]
+  return (a and a.shape ~= df.tiletype_shape.NONE) and a.shape or nil
+end
+
+-------------------------
+-- Predicates
+-------------------------
+local function is_walkable_dug(tt)
+  local s = tile_shape(tt)
+  if not s then return false end
+  return s == df.tiletype_shape.FLOOR
+      or s == df.tiletype_shape.RAMP
+      or s == df.tiletype_shape.STAIR_UP
+      or s == df.tiletype_shape.STAIR_DOWN
+      or s == df.tiletype_shape.STAIR_UPDOWN
+      or s == df.tiletype_shape.EMPTY
+end
+
+local function is_constructed_tile(x, y, z)
+  return constructions.findAtTile(x, y, z) ~= nil
+end
+
+local function has_any_building(x, y, z)
+  return buildings.findAtTile(xyz2pos(x, y, z)) ~= nil
+end
+
+-------------------------
+-- Flood fill
+-------------------------
+local function flood_fill_footprint(seed_x, seed_y, z0)
+  local footprint = {}
+  local visited = {}
+  local queue = { { seed_x, seed_y } }
+  visited[seed_x .. ',' .. seed_y] = true
+  local queue_pos = 1
+
+  local function push_if_ok(x, y)
+    if not in_bounds(x, y, z0) then return end
+    local key = x .. ',' .. y
+    if visited[key] then return end
+    local tt = get_tiletype(x, y, z0)
+    if is_walkable_dug(tt) then
+      visited[key] = true
+      table.insert(queue, { x, y })
+    end
+  end
+
+  while queue_pos <= #queue and #footprint < CONFIG.MAX_FILL_TILES do
+    local x, y = table.unpack(queue[queue_pos])
+    queue_pos = queue_pos + 1
+    table.insert(footprint, { x = x, y = y })
+    push_if_ok(x + 1, y)
+    push_if_ok(x - 1, y)
+    push_if_ok(x, y + 1)
+    push_if_ok(x, y - 1)
+    if CONFIG.ALLOW_DIAGONALS then
+      push_if_ok(x + 1, y + 1)
+      push_if_ok(x + 1, y - 1)
+      push_if_ok(x - 1, y + 1)
+      push_if_ok(x - 1, y - 1)
+    end
+  end
+
+  if #queue > CONFIG.MAX_FILL_TILES then
+    dfhack.printerr(('AutoCeiling: flood fill truncated at %d tiles'):format(CONFIG.MAX_FILL_TILES))
+  end
+  return footprint
+end
+
+-------------------------
+-- Placement strategies
+-------------------------
+local function place_planned(bp, pos)
+  local ok, bld = pcall(function()
+    return dfhack.buildings.constructBuilding{
+      type    = df.building_type.Construction,
+      subtype = df.construction_type.Floor,
+      pos     = pos
+    }
+  end)
+  if not ok or not bld then return false, 'construct-error' end
+  pcall(function() bp.addPlannedBuilding(bld) end)
+  return true
+end
+
+local function place_native(cons, pos)
+  if not cons or not cons.designateNew then return false, 'no-constructions-api' end
+
+  local ok, res = pcall(function()
+    return cons.designateNew(pos, df.construction_type.Floor, -1, -1)
+  end)
+  if ok and res then return true end
+
+  local ok2, res2 = pcall(function()
+    return cons.designateNew(pos, df.construction_type.Floor, df.item_type.BOULDER, -1)
+  end)
+  if ok2 and res2 then return true end
+
+  return false, 'designate-error'
+end
+
+-------------------------
+-- Main
+-------------------------
+local utils = require('utils')
+
+local function main(...)
+  local args = {...}
+
+  for _, raw in ipairs(args) do
+    local s = tostring(raw):lower()
+    local num = tonumber(s)
+    if num then
+      if num < 1 then err('MAX_FILL_TILES must be >= 1') end
+      if num > CONFIG.MAX_LIMIT_HARD then
+        dfhack.printerr(('clamping MAX_FILL_TILES from %d to %d'):format(num, CONFIG.MAX_LIMIT_HARD))
+        num = CONFIG.MAX_LIMIT_HARD
+      end
+      CONFIG.MAX_FILL_TILES = math.floor(num)
+    elseif s == 't' or s == 'true' then
+      CONFIG.ALLOW_DIAGONALS = true
+    elseif s == 'h' or s == 'help' then
+      print('Usage: autoceiling [t] [<max_fill_tiles>]')
+      print('  t: enable diagonal flood fill')
+      print('  <max_fill_tiles>: positive integer, default ' .. CONFIG.MAX_FILL_TILES)
+      return
+    elseif s ~= '' then
+      err('unknown argument: ' .. tostring(raw))
+    end
+  end
+
+  local cur = utils.clone(df.global.cursor)
+  if cur.x == -30000 then err('cursor not set. Move to a dug tile and run again.') end
+  local z0 = cur.z
+  local seed_tt = get_tiletype(cur.x, cur.y, z0)
+  if not is_walkable_dug(seed_tt) then err('cursor tile is not dug/open interior') end
+
+  local footprint = flood_fill_footprint(cur.x, cur.y, z0)
+  if #footprint == 0 then
+    print('AutoCeiling: nothing to do — no connected dug tiles found at cursor')
+    return
+  end
+  local z_surface = z0 + 1
+
+  -- Require buildingplan directly; let it error if missing
+  local bp = require('plugins.buildingplan')
+  if bp and (not bp.isEnabled or not bp.isEnabled()) then bp = nil end
+  local cons = dfhack.constructions
+
+  local placed, skipped = 0, 0
+  local reasons = {}
+  local function skip(reason)
+    skipped = skipped + 1
+    reasons[reason] = (reasons[reason] or 0) + 1
+  end
+
+  for i, foot in ipairs(footprint) do
+    local x, y = foot.x, foot.y
+    local pos = xyz2pos(x, y, z_surface)
+    if not in_bounds(x, y, z_surface) then
+      skip('oob')
+    elseif is_constructed_tile(x, y, z_surface) then
+      skip('constructed')
+    elseif has_any_building(x, y, z_surface) then
+      skip('building')
+    else
+      local ok, why
+      if bp then
+        ok, why = place_planned(bp, pos)
+      else
+        ok, why = place_native(cons, pos)
+      end
+      if ok then placed = placed + 1 else skip(why or 'unknown') end
+    end
+  end
+
+  if bp and bp.doCycle then pcall(function() bp.doCycle() end) end
+
+  print(('AutoCeiling: placed %d floor construction(s); skipped %d'):format(placed, skipped))
+  if bp then
+    print('buildingplan active: created planned floors that will auto-assign materials')
+  elseif cons and cons.designateNew then
+    print('used native construction designations')
+  else
+    print('no buildingplan and no constructions API available')
+  end
+  for k, v in pairs(reasons) do
+    print(('  skipped %-18s %d'):format(k, v))
+  end
+end
+
+main(...)
diff --git a/docs/autoceiling.rst b/docs/autoceiling.rst
new file mode 100644
index 000000000..7ca33e166
--- /dev/null
+++ b/docs/autoceiling.rst
@@ -0,0 +1,49 @@
+autoceiling
+===========
+
+.. dfhack-tool::
+    :summary: Place floors above dug areas to seal surface openings.
+    :tags: construction automation utility
+
+**AutoCeiling** is a DFHack Lua script that automatically places constructed
+floors above any dug-out area. It uses a flood-fill algorithm to detect connected
+dug tiles on the selected Z-level, then creates planned floor constructions
+directly above them to seal the area. This prevents surface collapse and stops
+creatures from entering your fortress through unexpected openings. It’s
+especially useful when building farms directly below the surface, since those
+areas are prone to collapsing without warning and can leave open spaces that
+allow surface creatures to breach your fort.
+
+Usage
+-----
+
+::
+
+    autoceiling [t] [<max>]
+
+Examples
+--------
+
+``autoceiling``
+    Run with default settings (4,000 tile flood-fill limit, no diagonal fill).
+
+``autoceiling t``
+    Enable diagonal flood-fill connections (8-way fill).
+
+``autoceiling 500``
+    Raise or lower flood-fill limits.
+
+``autoceiling t 6000`` or ``autoceiling 6000 t``
+    Allow diagonals and increase fill limit to 6,000 tiles.
+
+Options
+-------
+
+``t``
+    Enables 8-directional (diagonal) flood fill mode.
+
+``<max>``
+    Sets the maximum number of tiles the flood fill can cover (default: 4000).
+
+These are the only two options available for this command. Use ``t`` to toggle
+diagonal fill and ``<max>`` to control the tile limit for flood fill.