diff --git a/.github/workflows/haskell-ci.yml b/.github/workflows/haskell-ci.yml
index f8df82b64..7809130af 100644
--- a/.github/workflows/haskell-ci.yml
+++ b/.github/workflows/haskell-ci.yml
@@ -235,8 +235,8 @@ jobs:
           cabal-docspec $ARG_COMPILER
       - name: hlint
         run: |
-          if [ $((HCNUMVER < 90000)) -ne 0 ] ; then (cd ${PKGDIR_swarm} && hlint -h ${GITHUB_WORKSPACE}/source/.hlint.yaml -XHaskell2010 -XStrictData src) ; fi
-          if [ $((HCNUMVER < 90000)) -ne 0 ] ; then (cd ${PKGDIR_swarm} && hlint -h ${GITHUB_WORKSPACE}/source/.hlint.yaml -XHaskell2010 app) ; fi
+          if [ $((HCNUMVER < 90000)) -ne 0 ] ; then (cd ${PKGDIR_swarm} && hlint -h ${GITHUB_WORKSPACE}/source/.hlint.yaml -XHaskell2010 -XBangPatterns -XDeriveAnyClass -XDeriveDataTypeable -XDeriveFunctor -XDeriveGeneric -XDeriveTraversable -XExplicitForAll -XFlexibleContexts -XFlexibleInstances -XGADTSyntax -XMultiParamTypeClasses -XNumericUnderscores -XRankNTypes -XScopedTypeVariables -XStandaloneDeriving -XTupleSections -XTypeApplications -XTypeOperators -XImportQualifiedPost -XLambdaCase -XStrictData src) ; fi
+          if [ $((HCNUMVER < 90000)) -ne 0 ] ; then (cd ${PKGDIR_swarm} && hlint -h ${GITHUB_WORKSPACE}/source/.hlint.yaml -XHaskell2010 -XImportQualifiedPost app) ; fi
       - name: cabal check
         run: |
           cd ${PKGDIR_swarm} || false
diff --git a/.hlint.yaml b/.hlint.yaml
index 2e340dad8..e6baab2c3 100644
--- a/.hlint.yaml
+++ b/.hlint.yaml
@@ -10,7 +10,6 @@
 #
 # - arguments: [--color, --cpp-simple, -XQuasiQuotes]
 
-
 # Control which extensions/flags/modules/functions can be used
 #
 # - extensions:
diff --git a/.restyled.yaml b/.restyled.yaml
index b0ac4f734..b956f53e3 100644
--- a/.restyled.yaml
+++ b/.restyled.yaml
@@ -1,3 +1,17 @@
 restylers_version: dev
 restylers:
-  - fourmolu
+  - fourmolu:
+      arguments:
+        [ '--ghc-opt=-XBangPatterns'
+        , '--ghc-opt=-XFlexibleContexts'
+        , '--ghc-opt=-XFlexibleInstances'
+        , '--ghc-opt=-XGADTSyntax'
+        , '--ghc-opt=-XMultiParamTypeClasses'
+        , '--ghc-opt=-XNumericUnderscores'
+        , '--ghc-opt=-XRankNTypes'
+        , '--ghc-opt=-XTupleSections'
+        , '--ghc-opt=-XTypeApplications'
+        , '--ghc-opt=-XTypeOperators'
+        , '--ghc-opt=-XImportQualifiedPost'
+        , '--ghc-opt=-XLambdaCase'
+        ]
diff --git a/app/Main.hs b/app/Main.hs
index 2ab5af599..2c3291e61 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -7,7 +7,7 @@ import Data.Text (
   Text,
   pack,
  )
-import qualified Data.Text.IO as Text
+import Data.Text.IO qualified as Text
 import GitHash
 import Options.Applicative
 import Swarm.App (appMain)
diff --git a/bench/Benchmark.hs b/bench/Benchmark.hs
index cfe47580c..afef4e278 100644
--- a/bench/Benchmark.hs
+++ b/bench/Benchmark.hs
@@ -9,7 +9,7 @@ import Control.Monad.Except (runExceptT)
 import Control.Monad.State (evalStateT, execStateT)
 import Criterion.Main (Benchmark, bench, bgroup, defaultConfig, defaultMainWith, whnfAppIO)
 import Criterion.Types (Config (timeLimit))
-import qualified Data.Functor.Const as F
+import Data.Functor.Const qualified as F
 import Data.Int (Int64)
 import Linear.V2 (V2 (V2))
 import Swarm.Game.CESK (emptyStore, initMachine)
@@ -19,7 +19,7 @@ import Swarm.Game.State (GameState, addURobot, classicGame0, creativeMode, world
 import Swarm.Game.Step (gameTick)
 import Swarm.Game.Terrain (TerrainType (DirtT))
 import Swarm.Game.World (newWorld)
-import qualified Swarm.Language.Context as Context
+import Swarm.Language.Context qualified as Context
 import Swarm.Language.Pipeline (ProcessedTerm)
 import Swarm.Language.Pipeline.QQ (tmQ)
 import Swarm.Language.Syntax (north)
diff --git a/src/Swarm/App.hs b/src/Swarm/App.hs
index 87615a1a5..cf441807b 100644
--- a/src/Swarm/App.hs
+++ b/src/Swarm/App.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE NumericUnderscores #-}
-
 -- |
 -- Module      :  Swarm.App
 -- Copyright   :  Brent Yorgey
@@ -14,10 +12,10 @@ import Control.Concurrent (forkIO, threadDelay)
 
 import Brick
 import Brick.BChan
-import qualified Graphics.Vty as V
+import Graphics.Vty qualified as V
 
 import Control.Monad.Except
-import qualified Data.Text.IO as T
+import Data.Text.IO qualified as T
 import Swarm.TUI.Attr
 import Swarm.TUI.Controller
 import Swarm.TUI.Model
diff --git a/src/Swarm/DocGen.hs b/src/Swarm/DocGen.hs
index 38cc92b72..796f290ce 100644
--- a/src/Swarm/DocGen.hs
+++ b/src/Swarm/DocGen.hs
@@ -1,10 +1,4 @@
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE GADTSyntax #-}
-{-# LANGUAGE ImportQualifiedPost #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TupleSections #-}
 
 module Swarm.DocGen (
   generateDocs,
diff --git a/src/Swarm/Game/CESK.hs b/src/Swarm/Game/CESK.hs
index 9b3578398..87571b5cd 100644
--- a/src/Swarm/Game/CESK.hs
+++ b/src/Swarm/Game/CESK.hs
@@ -89,7 +89,7 @@ module Swarm.Game.CESK (
 
 import Control.Lens.Combinators (pattern Empty)
 import Data.IntMap.Strict (IntMap)
-import qualified Data.IntMap.Strict as IM
+import Data.IntMap.Strict qualified as IM
 import Data.List (intercalate)
 import Witch (from)
 
diff --git a/src/Swarm/Game/Display.hs b/src/Swarm/Game/Display.hs
index 1220c7d8b..1b375f323 100644
--- a/src/Swarm/Game/Display.hs
+++ b/src/Swarm/Game/Display.hs
@@ -1,7 +1,5 @@
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
-{-# LANGUAGE DeriveAnyClass #-}
-{-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE TemplateHaskell #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
@@ -41,7 +39,7 @@ import Brick (AttrName, Widget, str, withAttr)
 import Control.Lens hiding (Const, from, (.=))
 import Data.Hashable
 import Data.Map (Map)
-import qualified Data.Map as M
+import Data.Map qualified as M
 
 import Data.Yaml
 import GHC.Generics (Generic)
diff --git a/src/Swarm/Game/Entity.hs b/src/Swarm/Game/Entity.hs
index 62c429c88..28c8934d4 100644
--- a/src/Swarm/Game/Entity.hs
+++ b/src/Swarm/Game/Entity.hs
@@ -1,11 +1,4 @@
-{-# LANGUAGE DeriveAnyClass #-}
-{-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
 
 -- |
@@ -94,15 +87,15 @@ import Data.Function (on)
 import Data.Hashable
 import Data.Int (Int64)
 import Data.IntMap (IntMap)
-import qualified Data.IntMap as IM
+import Data.IntMap qualified as IM
 import Data.IntSet (IntSet)
-import qualified Data.IntSet as IS
+import Data.IntSet qualified as IS
 import Data.List (foldl')
 import Data.Map (Map)
-import qualified Data.Map as M
+import Data.Map qualified as M
 import Data.Maybe (fromMaybe, isJust, listToMaybe)
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import GHC.Generics (Generic)
 import Linear (V2)
 import Text.Read (readMaybe)
diff --git a/src/Swarm/Game/Exception.hs b/src/Swarm/Game/Exception.hs
index e6172a97d..3d942be17 100644
--- a/src/Swarm/Game/Exception.hs
+++ b/src/Swarm/Game/Exception.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 -- |
@@ -21,10 +20,10 @@ module Swarm.Game.Exception (
 
 import Data.Set (Set)
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 
 import Control.Lens ((^.))
-import qualified Data.Set as S
+import Data.Set qualified as S
 import Swarm.Game.Entity (EntityMap, deviceForCap, entityName)
 import Swarm.Language.Capability (Capability (CGod), capabilityName)
 import Swarm.Language.Pretty (prettyText)
diff --git a/src/Swarm/Game/Recipe.hs b/src/Swarm/Game/Recipe.hs
index 4edfecaf9..f68622899 100644
--- a/src/Swarm/Game/Recipe.hs
+++ b/src/Swarm/Game/Recipe.hs
@@ -1,12 +1,7 @@
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TypeApplications #-}
 
 -- |
 -- Module      :  Swarm.Game.Recipe
@@ -45,11 +40,11 @@ import Control.Lens hiding (from, (.=))
 import Data.Bifunctor (second)
 import Data.Either.Validation
 import Data.IntMap (IntMap)
-import qualified Data.IntMap as IM
+import Data.IntMap qualified as IM
 import Data.List (foldl')
 import Data.Maybe (fromMaybe)
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Witch
 
 import Data.Yaml
diff --git a/src/Swarm/Game/Robot.hs b/src/Swarm/Game/Robot.hs
index dec791d9d..2be789d6f 100644
--- a/src/Swarm/Game/Robot.hs
+++ b/src/Swarm/Game/Robot.hs
@@ -1,10 +1,6 @@
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-{-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE ViewPatterns #-}
 
@@ -75,7 +71,7 @@ import Data.Hashable (hashWithSalt)
 import Data.Int (Int64)
 import Data.Maybe (isNothing)
 import Data.Sequence (Seq)
-import qualified Data.Sequence as Seq
+import Data.Sequence qualified as Seq
 import Data.Set (Set)
 import Data.Set.Lens (setOf)
 import Data.Text (Text)
diff --git a/src/Swarm/Game/Scenario.hs b/src/Swarm/Game/Scenario.hs
index 173ca354a..5df9aa19c 100644
--- a/src/Swarm/Game/Scenario.hs
+++ b/src/Swarm/Game/Scenario.hs
@@ -1,14 +1,8 @@
 {-# LANGUAGE DefaultSignatures #-}
-{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DerivingVia #-}
-{-# LANGUAGE ImportQualifiedPost #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TypeApplications #-}
 
 -- |
 -- Module      :  Swarm.Game.Scenario
diff --git a/src/Swarm/Game/State.hs b/src/Swarm/Game/State.hs
index 6d33f57eb..54c2c237b 100644
--- a/src/Swarm/Game/State.hs
+++ b/src/Swarm/Game/State.hs
@@ -1,9 +1,6 @@
-{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE ViewPatterns #-}
 
 -- |
@@ -93,20 +90,20 @@ import Control.Monad.Except
 import Data.Array (Array, listArray)
 import Data.Int (Int64)
 import Data.IntMap (IntMap)
-import qualified Data.IntMap as IM
+import Data.IntMap qualified as IM
 import Data.IntSet (IntSet)
-import qualified Data.IntSet as IS
+import Data.IntSet qualified as IS
 import Data.IntSet.Lens (setOf)
 import Data.List (partition)
 import Data.Map (Map)
-import qualified Data.Map as M
+import Data.Map qualified as M
 import Data.Maybe (fromMaybe)
-import qualified Data.Set as S
+import Data.Set qualified as S
 import Data.Text (Text)
-import qualified Data.Text as T (lines)
-import qualified Data.Text.IO as T (readFile)
+import Data.Text qualified as T (lines)
+import Data.Text.IO qualified as T (readFile)
 import Linear
-import qualified System.Clock
+import System.Clock qualified
 import System.Random (StdGen, mkStdGen, randomRIO)
 import Witch (into)
 
@@ -121,10 +118,10 @@ import Swarm.Game.Recipe
 import Swarm.Game.Robot
 import Swarm.Game.Scenario
 import Swarm.Game.Value
-import qualified Swarm.Game.World as W
+import Swarm.Game.World qualified as W
 import Swarm.Game.WorldGen (Seed)
 import Swarm.Language.Capability (constCaps)
-import qualified Swarm.Language.Context as Ctx
+import Swarm.Language.Context qualified as Ctx
 import Swarm.Language.Pipeline (ProcessedTerm)
 import Swarm.Language.Pipeline.QQ (tmQ)
 import Swarm.Language.Syntax (Const, Term (TString), allConst)
diff --git a/src/Swarm/Game/Step.hs b/src/Swarm/Game/Step.hs
index f68841cab..1c4449692 100644
--- a/src/Swarm/Game/Step.hs
+++ b/src/Swarm/Game/Step.hs
@@ -1,13 +1,6 @@
-{-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE BlockArguments #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeOperators #-}
 
 -- |
 -- Module      :  Swarm.Game.Step
@@ -26,21 +19,21 @@ import Data.Array (bounds, (!))
 import Data.Bool (bool)
 import Data.Either (partitionEithers, rights)
 import Data.Foldable (traverse_)
-import qualified Data.Functor.Const as F
+import Data.Functor.Const qualified as F
 import Data.Int (Int64)
-import qualified Data.IntMap as IM
-import qualified Data.IntSet as IS
+import Data.IntMap qualified as IM
+import Data.IntSet qualified as IS
 import Data.List (find)
-import qualified Data.List as L
-import qualified Data.Map as M
+import Data.List qualified as L
+import Data.Map qualified as M
 import Data.Maybe (fromMaybe, isNothing, listToMaybe, mapMaybe)
-import qualified Data.Sequence as Seq
-import qualified Data.Set as S
+import Data.Sequence qualified as Seq
+import Data.Set qualified as S
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Linear (V2 (..), zero, (^+^))
 import System.Clock (TimeSpec)
-import qualified System.Clock
+import System.Clock qualified
 import System.Random (UniformRange, uniformR)
 import Witch (From (from), into)
 import Prelude hiding (lookup)
@@ -48,13 +41,13 @@ import Prelude hiding (lookup)
 import Swarm.Game.CESK
 import Swarm.Game.Display
 import Swarm.Game.Entity hiding (empty, lookup, singleton, union)
-import qualified Swarm.Game.Entity as E
+import Swarm.Game.Entity qualified as E
 import Swarm.Game.Exception
 import Swarm.Game.Recipe
 import Swarm.Game.Robot
 import Swarm.Game.State
 import Swarm.Game.Value
-import qualified Swarm.Game.World as W
+import Swarm.Game.World qualified as W
 import Swarm.Language.Capability
 import Swarm.Language.Context hiding (delete)
 import Swarm.Language.Pipeline
diff --git a/src/Swarm/Game/Terrain.hs b/src/Swarm/Game/Terrain.hs
index bdfd689b9..29aa1b898 100644
--- a/src/Swarm/Game/Terrain.hs
+++ b/src/Swarm/Game/Terrain.hs
@@ -1,6 +1,3 @@
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE TypeApplications #-}
-
 -- |
 -- Module      :  Swarm.Game.Terrain
 -- Copyright   :  Brent Yorgey
@@ -19,8 +16,8 @@ module Swarm.Game.Terrain (
 import Brick (Widget)
 import Data.Aeson (FromJSON (..), withText)
 import Data.Map (Map, (!))
-import qualified Data.Map as M
-import qualified Data.Text as T
+import Data.Map qualified as M
+import Data.Text qualified as T
 import Text.Read (readMaybe)
 import Witch (into)
 
diff --git a/src/Swarm/Game/Value.hs b/src/Swarm/Game/Value.hs
index 43cb7d639..90732d7dc 100644
--- a/src/Swarm/Game/Value.hs
+++ b/src/Swarm/Game/Value.hs
@@ -20,8 +20,8 @@ module Swarm.Game.Value (
 
 import Data.Bool (bool)
 import Data.List (foldl')
-import qualified Data.Map as M
-import qualified Data.Set as S
+import Data.Map qualified as M
+import Data.Set qualified as S
 import Data.Set.Lens (setOf)
 import Data.Text (Text)
 import Prelude
diff --git a/src/Swarm/Game/World.hs b/src/Swarm/Game/World.hs
index 5641165b3..18bea1163 100644
--- a/src/Swarm/Game/World.hs
+++ b/src/Swarm/Game/World.hs
@@ -1,10 +1,4 @@
 {-# LANGUAGE AllowAmbiguousTypes #-}
-{-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
 
 -- |
@@ -52,13 +46,13 @@ module Swarm.Game.World (
 
 import Control.Arrow ((&&&))
 import Control.Lens
-import qualified Data.Array as A
+import Data.Array qualified as A
 import Data.Array.IArray
-import qualified Data.Array.Unboxed as U
+import Data.Array.Unboxed qualified as U
 import Data.Bits
 import Data.Foldable (foldl')
 import Data.Int (Int64)
-import qualified Data.Map.Strict as M
+import Data.Map.Strict qualified as M
 import GHC.Generics (Generic)
 import Linear
 import Prelude hiding (lookup)
diff --git a/src/Swarm/Game/WorldGen.hs b/src/Swarm/Game/WorldGen.hs
index 52bb5132b..a298f84bd 100644
--- a/src/Swarm/Game/WorldGen.hs
+++ b/src/Swarm/Game/WorldGen.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE ImportQualifiedPost #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 -- |
diff --git a/src/Swarm/Language/Capability.hs b/src/Swarm/Language/Capability.hs
index 573319a9b..e44960276 100644
--- a/src/Swarm/Language/Capability.hs
+++ b/src/Swarm/Language/Capability.hs
@@ -1,9 +1,3 @@
-{-# LANGUAGE DeriveAnyClass #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE TypeApplications #-}
-
 -- |
 -- Module      :  Swarm.Language.Capability
 -- Copyright   :  Brent Yorgey
@@ -27,9 +21,9 @@ import Data.Char (toLower)
 import Data.Hashable (Hashable)
 import Data.Maybe (fromMaybe)
 import Data.Set (Set)
-import qualified Data.Set as S
+import Data.Set qualified as S
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Text.Read (readMaybe)
 import Witch (from)
 import Prelude hiding (lookup)
diff --git a/src/Swarm/Language/Context.hs b/src/Swarm/Language/Context.hs
index 3fb681468..e726cd8d6 100644
--- a/src/Swarm/Language/Context.hs
+++ b/src/Swarm/Language/Context.hs
@@ -1,8 +1,5 @@
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE FlexibleContexts #-}
 
 -- |
 -- Module      :  Swarm.Language.Context
@@ -20,7 +17,7 @@ import Control.Lens.Prism (prism)
 import Control.Monad.Reader (MonadReader, local)
 import Data.Data (Data)
 import Data.Map (Map)
-import qualified Data.Map as M
+import Data.Map qualified as M
 import Data.Text (Text)
 import Prelude hiding (lookup)
 
diff --git a/src/Swarm/Language/LSP.hs b/src/Swarm/Language/LSP.hs
index 2a2213c66..2fe29e906 100644
--- a/src/Swarm/Language/LSP.hs
+++ b/src/Swarm/Language/LSP.hs
@@ -16,14 +16,14 @@ import Control.Monad (void)
 import Control.Monad.IO.Class
 import Data.Maybe (fromMaybe)
 import Data.Text (Text)
-import qualified Data.Text.IO as Text
+import Data.Text.IO qualified as Text
 import System.IO (stderr)
 import Witch
 
 import Language.LSP.Diagnostics
 import Language.LSP.Server
-import qualified Language.LSP.Types as J
-import qualified Language.LSP.Types.Lens as J
+import Language.LSP.Types qualified as J
+import Language.LSP.Types.Lens qualified as J
 import Language.LSP.VFS
 
 import Swarm.Language.Parse
diff --git a/src/Swarm/Language/Parse.hs b/src/Swarm/Language/Parse.hs
index 47b391b3b..a4b222d38 100644
--- a/src/Swarm/Language/Parse.hs
+++ b/src/Swarm/Language/Parse.hs
@@ -1,7 +1,4 @@
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
 
 -- |
@@ -41,22 +38,22 @@ module Swarm.Language.Parse (
 import Control.Monad.Reader
 import Data.Bifunctor
 import Data.List (nub)
-import qualified Data.List.NonEmpty (head)
+import Data.List.NonEmpty qualified (head)
 import Data.Maybe (fromMaybe, mapMaybe)
 import Data.Text (Text, index, toLower)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Data.Void
 import Witch
 
 import Control.Monad.Combinators.Expr
-import qualified Data.Map.Strict as Map
+import Data.Map.Strict qualified as Map
 import Text.Megaparsec hiding (runParser)
 import Text.Megaparsec.Char
-import qualified Text.Megaparsec.Char.Lexer as L
-import qualified Text.Megaparsec.Pos as Pos
+import Text.Megaparsec.Char.Lexer qualified as L
+import Text.Megaparsec.Pos qualified as Pos
 
 import Data.Foldable (asum)
-import qualified Data.Set as S
+import Data.Set qualified as S
 import Data.Set.Lens (setOf)
 import Swarm.Language.Syntax
 import Swarm.Language.Types
diff --git a/src/Swarm/Language/Parse/QQ.hs b/src/Swarm/Language/Parse/QQ.hs
index a2fb28b2f..913976047 100644
--- a/src/Swarm/Language/Parse/QQ.hs
+++ b/src/Swarm/Language/Parse/QQ.hs
@@ -9,7 +9,7 @@
 module Swarm.Language.Parse.QQ (tyQ) where
 
 import Data.Generics
-import qualified Language.Haskell.TH as TH
+import Language.Haskell.TH qualified as TH
 import Language.Haskell.TH.Quote
 
 import Swarm.Language.Parse
diff --git a/src/Swarm/Language/Pipeline.hs b/src/Swarm/Language/Pipeline.hs
index 0ea3675cc..8b7311370 100644
--- a/src/Swarm/Language/Pipeline.hs
+++ b/src/Swarm/Language/Pipeline.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 -- |
diff --git a/src/Swarm/Language/Pipeline/QQ.hs b/src/Swarm/Language/Pipeline/QQ.hs
index 9f7238236..293c373f5 100644
--- a/src/Swarm/Language/Pipeline/QQ.hs
+++ b/src/Swarm/Language/Pipeline/QQ.hs
@@ -9,7 +9,7 @@
 module Swarm.Language.Pipeline.QQ (tmQ) where
 
 import Data.Generics
-import qualified Language.Haskell.TH as TH
+import Language.Haskell.TH qualified as TH
 import Language.Haskell.TH.Quote
 import Witch (from)
 
diff --git a/src/Swarm/Language/Pretty.hs b/src/Swarm/Language/Pretty.hs
index a1895919b..3635da34b 100644
--- a/src/Swarm/Language/Pretty.hs
+++ b/src/Swarm/Language/Pretty.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE UndecidableInstances #-}
@@ -19,10 +18,10 @@ import Data.Bool (bool)
 import Data.Functor.Fixedpoint (Fix, unFix)
 import Data.String (fromString)
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Prettyprinter
-import qualified Prettyprinter.Render.String as RS
-import qualified Prettyprinter.Render.Text as RT
+import Prettyprinter.Render.String qualified as RS
+import Prettyprinter.Render.Text qualified as RT
 import Witch
 
 import Control.Unification
diff --git a/src/Swarm/Language/Syntax.hs b/src/Swarm/Language/Syntax.hs
index 2e887047d..e9b5ac9bc 100644
--- a/src/Swarm/Language/Syntax.hs
+++ b/src/Swarm/Language/Syntax.hs
@@ -1,12 +1,6 @@
-{-# LANGUAGE DeriveAnyClass #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE DerivingStrategies #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE PatternSynonyms #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TupleSections #-}
 {-# LANGUAGE UndecidableInstances #-}
 
 -- |
@@ -73,10 +67,10 @@ module Swarm.Language.Syntax (
 import Control.Lens (Plated (..), Traversal', (%~))
 import Data.Data.Lens (uniplate)
 import Data.Int (Int64)
-import qualified Data.Map as M
-import qualified Data.Set as S
+import Data.Map qualified as M
+import Data.Set qualified as S
 import Data.Text hiding (filter, map)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Linear
 
 import Data.Aeson.Types
diff --git a/src/Swarm/Language/Typecheck.hs b/src/Swarm/Language/Typecheck.hs
index 181759cf1..cb0274b53 100644
--- a/src/Swarm/Language/Typecheck.hs
+++ b/src/Swarm/Language/Typecheck.hs
@@ -1,12 +1,5 @@
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE TypeOperators #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 -- For 'Ord IntVar' instance
@@ -56,18 +49,18 @@ import Control.Monad.Reader
 import Data.Foldable (fold)
 import Data.Functor.Identity
 import Data.Map (Map)
-import qualified Data.Map as M
+import Data.Map qualified as M
 import Data.Maybe
 import Data.Set (Set, (\\))
-import qualified Data.Set as S
+import Data.Set qualified as S
 import Prelude hiding (lookup)
 
 import Control.Unification hiding (applyBindings, (=:=))
-import qualified Control.Unification as U
+import Control.Unification qualified as U
 import Control.Unification.IntVar
 
 import Swarm.Language.Context hiding (lookup)
-import qualified Swarm.Language.Context as Ctx
+import Swarm.Language.Context qualified as Ctx
 import Swarm.Language.Parse.QQ (tyQ)
 import Swarm.Language.Syntax
 import Swarm.Language.Types
diff --git a/src/Swarm/Language/Types.hs b/src/Swarm/Language/Types.hs
index 5761b0fb0..938ba455a 100644
--- a/src/Swarm/Language/Types.hs
+++ b/src/Swarm/Language/Types.hs
@@ -1,13 +1,4 @@
-{-# LANGUAGE DeriveAnyClass #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE PatternSynonyms #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
@@ -90,10 +81,10 @@ import Data.Foldable (fold)
 import Data.Functor.Fixedpoint
 import Data.Maybe (fromJust)
 import Data.Set (Set)
-import qualified Data.Set as S
+import Data.Set qualified as S
 import Data.String (IsString (..))
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import GHC.Generics (Generic1)
 import Witch
 
diff --git a/src/Swarm/TUI/Attr.hs b/src/Swarm/TUI/Attr.hs
index 360a9e935..efc769e5c 100644
--- a/src/Swarm/TUI/Attr.hs
+++ b/src/Swarm/TUI/Attr.hs
@@ -1,7 +1,6 @@
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE TypeApplications #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 -- |
@@ -19,7 +18,7 @@ import Brick
 import Brick.Forms
 import Brick.Widgets.Dialog
 import Brick.Widgets.List
-import qualified Graphics.Vty as V
+import Graphics.Vty qualified as V
 
 import Data.Yaml
 import Witch (from)
diff --git a/src/Swarm/TUI/Border.hs b/src/Swarm/TUI/Border.hs
index 150234399..a63af6d7b 100644
--- a/src/Swarm/TUI/Border.hs
+++ b/src/Swarm/TUI/Border.hs
@@ -34,7 +34,7 @@ import Brick
 import Brick.Widgets.Border
 import Control.Lens (makeLenses, to, (^.))
 import Data.Function ((&))
-import qualified Graphics.Vty as V
+import Graphics.Vty qualified as V
 
 -- | Labels for a horizontal border, with optional left, middle, and
 --   right labels.
diff --git a/src/Swarm/TUI/Controller.hs b/src/Swarm/TUI/Controller.hs
index ede097943..8066f7847 100644
--- a/src/Swarm/TUI/Controller.hs
+++ b/src/Swarm/TUI/Controller.hs
@@ -1,7 +1,3 @@
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE ImportQualifiedPost #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE NumericUnderscores #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE PatternSynonyms #-}
 
diff --git a/src/Swarm/TUI/List.hs b/src/Swarm/TUI/List.hs
index 156bd9825..6a6a2bfce 100644
--- a/src/Swarm/TUI/List.hs
+++ b/src/Swarm/TUI/List.hs
@@ -14,8 +14,8 @@ import Data.Foldable (toList)
 import Data.List (find)
 
 import Brick (EventM)
-import qualified Brick.Widgets.List as BL
-import qualified Graphics.Vty as V
+import Brick.Widgets.List qualified as BL
+import Graphics.Vty qualified as V
 
 -- | Handle a list event, taking an extra predicate to identify which
 --   list elements are separators; separators will be skipped if
diff --git a/src/Swarm/TUI/Model.hs b/src/Swarm/TUI/Model.hs
index 961791ae7..9a3d4168f 100644
--- a/src/Swarm/TUI/Model.hs
+++ b/src/Swarm/TUI/Model.hs
@@ -1,10 +1,6 @@
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE ImportQualifiedPost #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE ViewPatterns #-}
 
 -- |
diff --git a/src/Swarm/TUI/Panel.hs b/src/Swarm/TUI/Panel.hs
index 5e7915a9d..09cc04ebb 100644
--- a/src/Swarm/TUI/Panel.hs
+++ b/src/Swarm/TUI/Panel.hs
@@ -1,7 +1,5 @@
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE TemplateHaskell #-}
 
 -- |
diff --git a/src/Swarm/TUI/View.hs b/src/Swarm/TUI/View.hs
index 1f28a761b..1c329de7e 100644
--- a/src/Swarm/TUI/View.hs
+++ b/src/Swarm/TUI/View.hs
@@ -1,8 +1,4 @@
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TypeApplications #-}
 
 -- |
 -- Module      :  Swarm.TUI.View
@@ -45,16 +41,16 @@ module Swarm.TUI.View (
 import Control.Arrow ((&&&))
 import Control.Lens hiding (Const, from)
 import Data.Array (range)
-import qualified Data.Foldable as F
-import qualified Data.IntMap as IM
-import qualified Data.List as L
+import Data.Foldable qualified as F
+import Data.IntMap qualified as IM
+import Data.List qualified as L
 import Data.List.NonEmpty (NonEmpty (..))
 import Data.List.Split (chunksOf)
-import qualified Data.Map as M
+import Data.Map qualified as M
 import Data.Maybe (fromMaybe, mapMaybe)
 import Data.String (fromString)
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Linear
 import System.Clock (TimeSpec (..))
 import Text.Printf
@@ -67,8 +63,8 @@ import Brick.Forms
 import Brick.Widgets.Border (hBorder, hBorderWithLabel, joinableBorder, vBorder)
 import Brick.Widgets.Center (center, centerLayer, hCenter)
 import Brick.Widgets.Dialog
-import qualified Brick.Widgets.List as BL
-import qualified Brick.Widgets.Table as BT
+import Brick.Widgets.List qualified as BL
+import Brick.Widgets.Table qualified as BT
 
 import Swarm.Game.CESK (CESK (..))
 import Swarm.Game.Display
@@ -78,7 +74,7 @@ import Swarm.Game.Robot
 import Swarm.Game.Scenario (ScenarioItem (..), scenarioDescription, scenarioItemName, scenarioName)
 import Swarm.Game.State
 import Swarm.Game.Terrain (displayTerrain)
-import qualified Swarm.Game.World as W
+import Swarm.Game.World qualified as W
 import Swarm.Language.Pipeline (ProcessedTerm (..), processParsedTerm)
 import Swarm.Language.Pretty (prettyText)
 import Swarm.Language.Syntax
diff --git a/src/Swarm/Util.hs b/src/Swarm/Util.hs
index 81d174048..e8614234c 100644
--- a/src/Swarm/Util.hs
+++ b/src/Swarm/Util.hs
@@ -1,11 +1,5 @@
-{-# LANGUAGE DeriveAnyClass #-}
-{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE TemplateHaskellQuotes #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeOperators #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 -- |
@@ -74,17 +68,17 @@ import Data.Char (isAlphaNum)
 import Data.Either.Validation
 import Data.Int (Int64)
 import Data.Map (Map)
-import qualified Data.Map as M
+import Data.Map qualified as M
 import Data.Maybe (fromMaybe, mapMaybe)
 import Data.Text (Text, toUpper)
-import qualified Data.Text as T
-import qualified Data.Text.IO as T
+import Data.Text qualified as T
+import Data.Text.IO qualified as T
 import Data.Tuple (swap)
 import Data.Yaml
 import Language.Haskell.TH
 import Language.Haskell.TH.Syntax (lift)
 import Linear (V2)
-import qualified NLP.Minimorph.English as MM
+import NLP.Minimorph.English qualified as MM
 import NLP.Minimorph.Util ((<+>))
 import Paths_swarm (getDataDir)
 import System.Directory (
diff --git a/src/Swarm/Util/Yaml.hs b/src/Swarm/Util/Yaml.hs
index fa9e8fe92..e3e90c33b 100644
--- a/src/Swarm/Util/Yaml.hs
+++ b/src/Swarm/Util/Yaml.hs
@@ -1,9 +1,5 @@
 {-# LANGUAGE DefaultSignatures #-}
-{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DerivingVia #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE UndecidableInstances #-}
 
 -- |
@@ -36,7 +32,7 @@ import Data.Aeson.Types (explicitParseField, explicitParseFieldMaybe)
 import Data.Bifunctor (first)
 import Data.Maybe (fromMaybe)
 import Data.Text (Text)
-import qualified Data.Vector as V
+import Data.Vector qualified as V
 import Data.Yaml as Y
 
 ------------------------------------------------------------
diff --git a/swarm.cabal b/swarm.cabal
index 9909d5f91..3f45cf945 100644
--- a/swarm.cabal
+++ b/swarm.cabal
@@ -50,8 +50,35 @@ common stan-config
     ghc-options:      -fwrite-ide-info
                       -hiedir=.hie
 
+-- Harmless extensions from GHC2021
+common ghc2021-extensions
+    ghc-options:  -Wprepositive-qualified-module
+    default-extensions:
+      BangPatterns
+      DeriveAnyClass
+      DeriveDataTypeable
+      DeriveFunctor
+      DeriveGeneric
+      DeriveTraversable
+      ExplicitForAll
+      FlexibleContexts
+      FlexibleInstances
+      GADTSyntax
+      MultiParamTypeClasses
+      NumericUnderscores
+      RankNTypes
+      ScopedTypeVariables
+      StandaloneDeriving
+      TupleSections
+      TypeApplications
+      TypeOperators
+      -- Note we warn on prequalified
+      ImportQualifiedPost
+      -- Not GHC2021, but until we get \cases we use \case a lot
+      LambdaCase
+
 library
-    import:           stan-config, common
+    import:           stan-config, common, ghc2021-extensions
     exposed-modules:  Swarm.Language.Context
                       Swarm.Language.Types
                       Swarm.Language.Syntax
@@ -130,7 +157,10 @@ library
                       yaml                          >= 0.11 && < 0.12,
     hs-source-dirs:   src
     default-language: Haskell2010
-    default-extensions: StrictData
+    default-extensions:
+      -- Avoid unexpected unevaluated thunk buildup
+      -- See discussion in #415
+      StrictData
 
 executable swarm
     import:           stan-config, common
@@ -144,9 +174,10 @@ executable swarm
     hs-source-dirs:   app
     default-language: Haskell2010
     ghc-options:      -threaded
+    default-extensions: ImportQualifiedPost
 
 test-suite swarm-unit
-    import:           stan-config, common
+    import:           stan-config, common, ghc2021-extensions
     main-is:          Main.hs
     type:             exitcode-stdio-1.0
 
@@ -168,7 +199,7 @@ test-suite swarm-unit
     ghc-options:      -threaded
 
 test-suite swarm-integration
-    import:           stan-config, common
+    import:           stan-config, common, ghc2021-extensions
     main-is:          Main.hs
     type:             exitcode-stdio-1.0
 
@@ -193,7 +224,7 @@ test-suite swarm-integration
     ghc-options:      -threaded
 
 benchmark benchmark
-  import:         stan-config, common
+  import:         stan-config, common, ghc2021-extensions
   main-is:        Benchmark.hs
   hs-source-dirs: bench
   type:           exitcode-stdio-1.0
diff --git a/test/integration/Main.hs b/test/integration/Main.hs
index 2b25154e5..e97ad00ba 100644
--- a/test/integration/Main.hs
+++ b/test/integration/Main.hs
@@ -11,11 +11,11 @@ import Control.Monad.State (StateT (runStateT), gets)
 import Control.Monad.Trans.Except (runExceptT)
 import Data.Containers.ListUtils (nubOrd)
 import Data.Foldable (Foldable (toList), find)
-import qualified Data.IntSet as IS
-import qualified Data.Map as M
+import Data.IntSet qualified as IS
+import Data.Map qualified as M
 import Data.Maybe (isJust)
 import Data.Text (Text)
-import qualified Data.Text as T
+import Data.Text qualified as T
 import Data.Yaml (ParseException, prettyPrintParseException)
 import Swarm.Game.CESK (emptyStore, initMachine)
 import Swarm.Game.Entity (EntityMap, loadEntities)
@@ -33,7 +33,7 @@ import Swarm.Game.State (
   winSolution,
  )
 import Swarm.Game.Step (gameTick)
-import qualified Swarm.Language.Context as Ctx
+import Swarm.Language.Context qualified as Ctx
 import Swarm.Language.Pipeline (processTerm)
 import Swarm.Util.Yaml (decodeFileEitherE)
 import System.Directory (doesDirectoryExist, doesFileExist, listDirectory)
diff --git a/test/unit/Main.hs b/test/unit/Main.hs
index 9153c9862..d4b2b0eac 100644
--- a/test/unit/Main.hs
+++ b/test/unit/Main.hs
@@ -1,5 +1,4 @@
 {-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE ImportQualifiedPost #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE TypeApplications #-}