diff --git a/.github/workflows/haskell.yml b/.github/workflows/haskell.yml
index 5e285d10..8661ef32 100644
--- a/.github/workflows/haskell.yml
+++ b/.github/workflows/haskell.yml
@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ghc: ['9.6.2', '9.4.6', '9.2.8', '9.0.2', '8.10.7', '8.8.4', '8.6.5']
+        ghc: ['9.6.2', '9.4.6', '9.2.8', '9.0.2', '8.10.7']
         os: [ubuntu-latest, macOS-latest, windows-latest]
 
     steps:
diff --git a/hie-bios.cabal b/hie-bios.cabal
index cf39f50d..d38a0ed8 100644
--- a/hie-bios.cabal
+++ b/hie-bios.cabal
@@ -139,7 +139,7 @@ Extra-Source-Files:     ChangeLog.md
                         tests/projects/stack-with-yaml/stack-with-yaml.cabal
                         tests/projects/stack-with-yaml/src/Lib.hs
 
-tested-with: GHC ==8.6.5 || ==8.8.4 || ==8.10.7 || ==9.0.2 || ==9.2.8 || ==9.4.6 || ==9.6.2
+tested-with: GHC ==8.10.7 || ==9.0.2 || ==9.2.8 || ==9.4.6 || ==9.6.2
 
 Library
   Default-Language:     Haskell2010
@@ -163,7 +163,7 @@ Library
   Other-Modules:        Paths_hie_bios
   autogen-modules:      Paths_hie_bios
   Build-Depends:
-                        base                 >= 4.8 && < 5,
+                        base                 >= 4.14 && < 5,
                         aeson                >= 1.4.4 && < 2.3,
                         base16-bytestring    >= 0.1.1 && < 1.1,
                         bytestring           >= 0.10.8 && < 0.13,
@@ -176,7 +176,7 @@ Library
                         time                 >= 1.8.0 && < 1.13,
                         extra                >= 1.6.14 && < 1.8,
                         prettyprinter        ^>= 1.6 || ^>= 1.7.0,
-                        ghc                  >= 8.6.1 && < 9.7,
+                        ghc                  >= 8.10.1 && < 9.7,
                         transformers         >= 0.5.2 && < 0.7,
                         temporary            >= 1.2 && < 1.4,
                         template-haskell,
diff --git a/src/HIE/Bios/Cradle.hs b/src/HIE/Bios/Cradle.hs
index 60515ccf..c819b1b8 100644
--- a/src/HIE/Bios/Cradle.hs
+++ b/src/HIE/Bios/Cradle.hs
@@ -190,7 +190,7 @@ addActionDeps deps =
       CradleNone
       (\err -> CradleFail (err { cradleErrorDependencies = cradleErrorDependencies err `union` deps }))
       (\(ComponentOptions os' dir ds) -> CradleSuccess (ComponentOptions os' dir (ds `union` deps)))
-  
+
 
 resolvedCradlesToCradle :: Show a => LogAction IO (WithSeverity Log) -> (b -> CradleAction a) -> FilePath -> [ResolvedCradle b] -> IO (Cradle a)
 resolvedCradlesToCradle logger buildCustomCradle root cs = mdo
@@ -275,7 +275,7 @@ resolveCradleAction l buildCustomCradle cs root cradle =
     ConcreteOther a -> buildCustomCradle a
 
 resolveCradleTree :: FilePath -> CradleConfig a -> [ResolvedCradle a]
-resolveCradleTree root (CradleConfig deps tree) = go root deps tree
+resolveCradleTree root (CradleConfig confDeps confTree) = go root confDeps confTree
   where
     go pfix deps tree = case tree of
       Cabal t              -> [ResolvedCradle pfix deps (ConcreteCabal t)]
@@ -422,7 +422,7 @@ noneCradle =
 canonicalizeResolvedCradles :: FilePath -> [ResolvedCradle a] -> IO [ResolvedCradle a]
 canonicalizeResolvedCradles cur_dir cs =
   sortOn (Down . prefix)
-    <$> mapM (\c -> (\abs -> c {prefix = abs}) <$> makeAbsolute (cur_dir </> prefix c)) cs
+    <$> mapM (\c -> (\abs_fp -> c {prefix = abs_fp}) <$> makeAbsolute (cur_dir </> prefix c)) cs
 
 selectCradle :: (a -> FilePath) -> FilePath -> [a] -> Maybe a
 selectCradle _ _ [] = Nothing
@@ -442,7 +442,7 @@ directCradle l wdir args
           return (CradleSuccess (ComponentOptions (args ++ argDynamic) wdir []))
       , runGhcCmd = runGhcCmdOnPath l wdir
       }
-    
+
 
 -------------------------------------------------------------------------
 
@@ -526,7 +526,7 @@ cabalCradle l cs wdir mc projectFile
         cabalProc <- cabalProcess l projectFile wdir "v2-exec" $ ["ghc", "-v0", "--"] ++ args
         readProcessWithCwd' l cabalProc ""
     }
-    
+
 
 -- | Execute a cabal process in our custom cache-build directory configured
 -- with the custom ghc executable.
diff --git a/src/HIE/Bios/Environment.hs b/src/HIE/Bios/Environment.hs
index a750ddd2..eb82d219 100644
--- a/src/HIE/Bios/Environment.hs
+++ b/src/HIE/Bios/Environment.hs
@@ -13,7 +13,6 @@ import System.FilePath
 import System.Environment (lookupEnv)
 
 import qualified Crypto.Hash.SHA1 as H
-import Colog.Core (LogAction, WithSeverity)
 import qualified Data.ByteString.Char8 as B
 import Data.ByteString.Base16
 import Data.List
diff --git a/src/HIE/Bios/Flags.hs b/src/HIE/Bios/Flags.hs
index ccf73cf3..a9d9bb44 100644
--- a/src/HIE/Bios/Flags.hs
+++ b/src/HIE/Bios/Flags.hs
@@ -2,7 +2,7 @@ module HIE.Bios.Flags (getCompilerOptions) where
 
 import HIE.Bios.Types
 
-import Colog.Core (LogAction (..), WithSeverity (..), Severity (..), (<&))
+import Colog.Core (WithSeverity (..), Severity (..), (<&))
 
 -- | Initialize the 'DynFlags' relating to the compilation of a single
 -- file or GHC session according to the provided 'Cradle'.
diff --git a/src/HIE/Bios/Ghc/Api.hs b/src/HIE/Bios/Ghc/Api.hs
index 0749581b..4dc19844 100644
--- a/src/HIE/Bios/Ghc/Api.hs
+++ b/src/HIE/Bios/Ghc/Api.hs
@@ -23,7 +23,6 @@ import qualified GhcMake as G
 import qualified HIE.Bios.Ghc.Gap as Gap
 import Control.Monad (void)
 import Control.Monad.IO.Class
-import Colog.Core (LogAction (..), WithSeverity (..))
 import HIE.Bios.Types
 import HIE.Bios.Environment
 import HIE.Bios.Flags
diff --git a/src/HIE/Bios/Ghc/Check.hs b/src/HIE/Bios/Ghc/Check.hs
index d08bd352..e7b88faf 100644
--- a/src/HIE/Bios/Ghc/Check.hs
+++ b/src/HIE/Bios/Ghc/Check.hs
@@ -7,14 +7,9 @@ module HIE.Bios.Ghc.Check (
   , check
   ) where
 
-import GHC (DynFlags(..), GhcMonad)
+import GHC (GhcMonad)
 import qualified GHC as G
 
-#if __GLASGOW_HASKELL__ >= 900
-import qualified GHC.Driver.Session as G
-#else
-import qualified DynFlags as G
-#endif
 
 import Control.Exception
 import Control.Monad.IO.Class
@@ -28,8 +23,6 @@ import qualified HIE.Bios.Types as T
 import qualified HIE.Bios.Ghc.Load as Load
 import HIE.Bios.Environment
 
-import System.IO.Unsafe (unsafePerformIO)
-import qualified HIE.Bios.Ghc.Gap as Gap
 
 data Log =
   LoadLog Load.Log
@@ -74,23 +67,8 @@ check :: (GhcMonad m)
       -> [FilePath]  -- ^ The target files.
       -> m (Either String String)
 check logger fileNames = do
-  libDir <- G.topDir <$> G.getDynFlags
-  withLogger (setAllWarningFlags libDir) $ Load.setTargetFiles (cmap (fmap LoadLog) logger) (map dup fileNames)
+  withLogger id $ Load.setTargetFiles (cmap (fmap LoadLog) logger) (map dup fileNames)
 
 dup :: a -> (a, a)
 dup x = (x, x)
 
-----------------------------------------------------------------
-
--- | Set 'DynFlags' equivalent to "-Wall".
-setAllWarningFlags :: FilePath -> DynFlags -> DynFlags
-setAllWarningFlags libDir df = df { warningFlags = allWarningFlags libDir }
-
-{-# NOINLINE allWarningFlags #-}
-allWarningFlags :: FilePath -> Gap.WarnFlags
-allWarningFlags libDir = unsafePerformIO $
-    G.runGhcT (Just libDir) $ do
-        df <- G.getSessionDynFlags
-        (df', _) <- addCmdOpts ["-Wall"] df
-        return $ G.warningFlags df'
-
diff --git a/src/HIE/Bios/Ghc/Gap.hs b/src/HIE/Bios/Ghc/Gap.hs
index 2d5ece4a..b4cd74ce 100644
--- a/src/HIE/Bios/Ghc/Gap.hs
+++ b/src/HIE/Bios/Ghc/Gap.hs
@@ -3,8 +3,6 @@
 module HIE.Bios.Ghc.Gap (
   ghcVersion
   -- * Warnings, Doc Compat
-  , WarnFlags
-  , emptyWarnFlags
   , makeUserStyle
   , PprStyle
   -- * Argument parsing
@@ -27,11 +25,6 @@ module HIE.Bios.Ghc.Gap (
   , HIE.Bios.Ghc.Gap.getLogger
   -- * AST compat
   , pattern HIE.Bios.Ghc.Gap.RealSrcSpan
-  , LExpression
-  , LBinding
-  , LPattern
-  , inTypes
-  , outType
   -- * Exceptions
   , catch
   , bracket
@@ -49,7 +42,6 @@ module HIE.Bios.Ghc.Gap (
   -- * Platform constants
   , hostIsDynamic
   -- * misc
-  , getModuleName
   , getTyThing
   , fixInfo
   , Tc.FrontendResult(..)
@@ -68,7 +60,7 @@ import qualified Control.Monad.Catch as E
 import GHC
 import qualified GHC as G
 
-#if __GLASGOW_HASKELL__ >= 804 && __GLASGOW_HASKELL__ < 900
+#if __GLASGOW_HASKELL__ >= 810 && __GLASGOW_HASKELL__ < 900
 import Data.List
 import System.FilePath
 
@@ -89,25 +81,13 @@ import DriverPhases as G
 import Util as G
 import qualified GhcMonad as G
 
-#if __GLASGOW_HASKELL__ >= 808
 import qualified DynamicLoading (initializePlugins)
 import qualified Plugins (plugins)
 #endif
-
-#if __GLASGOW_HASKELL__ >= 806 && __GLASGOW_HASKELL__ < 810
-import HsExtension (GhcTc)
-import HsExpr (MatchGroup, MatchGroupTc(..))
-#elif __GLASGOW_HASKELL__ >= 804 && __GLASGOW_HASKELL__ < 810
-import HsExtension (GhcTc)
-import HsExpr (MatchGroup)
-#endif
-#endif
 ----------------------------------------------------------------
 ----------------------------------------------------------------
 
 #if __GLASGOW_HASKELL__ >= 902
-import GHC.Core.Multiplicity (irrelevantMult)
-import GHC.Data.EnumSet as E
 import GHC.Driver.CmdLine as CmdLine
 import GHC.Driver.Env as G
 import GHC.Driver.Session as G
@@ -195,15 +175,9 @@ handle :: (G.ExceptionMonad m, E.Exception e) => (e -> m a) -> m a -> m a
 handle = G.ghandle
 #endif
 
-#if __GLASGOW_HASKELL__ >= 810
 catch :: (E.MonadCatch m, E.Exception e) => m a -> (e -> m a) -> m a
 catch =
   E.catch
-#else
-catch :: (G.ExceptionMonad m, E.Exception e) => m a -> (e -> m a) -> m a
-catch =
-  G.gcatch
-#endif
 
 ----------------------------------------------------------------
 
@@ -264,20 +238,8 @@ makeUserStyle _dflags style = mkUserStyle style AllTheWay
 makeUserStyle dflags style = mkUserStyle dflags style AllTheWay
 #endif
 
-#if __GLASGOW_HASKELL__ >= 804
-getModuleName :: (a, b) -> a
-getModuleName = fst
-#endif
-
 ----------------------------------------------------------------
-
-#if __GLASGOW_HASKELL__ >= 804
-type WarnFlags = E.EnumSet WarningFlag
-emptyWarnFlags :: WarnFlags
-emptyWarnFlags = E.empty
-#endif
-
-#if __GLASGOW_HASKELL__ >= 804
+#if __GLASGOW_HASKELL__ >= 810
 getModSummaries :: ModuleGraph -> [ModSummary]
 getModSummaries = mgModSummaries
 
@@ -293,44 +255,18 @@ fixInfo (t,f,cs,fs,_) = (t,f,cs,fs)
 mapOverIncludePaths :: (FilePath -> FilePath) -> DynFlags -> DynFlags
 mapOverIncludePaths f df = df
   { includePaths =
-#if __GLASGOW_HASKELL__ > 804
+#if __GLASGOW_HASKELL__ >= 810
       G.IncludeSpecs
           (map f $ G.includePathsQuote  (includePaths df))
           (map f $ G.includePathsGlobal (includePaths df))
 #if MIN_VERSION_GLASGOW_HASKELL(9,0,2,0)
           (map f $ G.includePathsQuoteImplicit (includePaths df))
 #endif
-#else
-      map f (includePaths df)
 #endif
   }
 
 ----------------------------------------------------------------
 
-#if __GLASGOW_HASKELL__ >= 806
-type LExpression = LHsExpr GhcTc
-type LBinding    = LHsBind GhcTc
-type LPattern    = LPat    GhcTc
-
-inTypes :: MatchGroup GhcTc LExpression -> [Type]
-#if __GLASGOW_HASKELL__ >= 900
-inTypes = map irrelevantMult . mg_arg_tys . mg_ext
-#else
-inTypes = mg_arg_tys . mg_ext
-#endif
-outType :: MatchGroup GhcTc LExpression -> Type
-outType = mg_res_ty . mg_ext
-#elif __GLASGOW_HASKELL__ >= 804
-type LExpression = LHsExpr GhcTc
-type LBinding    = LHsBind GhcTc
-type LPattern    = LPat    GhcTc
-
-inTypes :: MatchGroup GhcTc LExpression -> [Type]
-inTypes = mg_arg_tys
-outType :: MatchGroup GhcTc LExpression -> Type
-outType = mg_res_ty
-#endif
-
 unsetLogAction :: GhcMonad m => m ()
 unsetLogAction = do
 #if __GLASGOW_HASKELL__ >= 902
diff --git a/tests/BiosTests.hs b/tests/BiosTests.hs
index c6947b0d..82ae040c 100644
--- a/tests/BiosTests.hs
+++ b/tests/BiosTests.hs
@@ -352,14 +352,6 @@ stackYamlResolver =
   "lts-19.33" -- GHC 9.0.2
 #elif (defined(MIN_VERSION_GLASGOW_HASKELL) && (MIN_VERSION_GLASGOW_HASKELL(8,10,7,0)))
   "lts-18.28" -- GHC 8.10.7
-#elif (defined(MIN_VERSION_GLASGOW_HASKELL) && (MIN_VERSION_GLASGOW_HASKELL(8,10,1,0)))
-  "lts-18.6" -- GHC 8.10.4
-#elif (defined(MIN_VERSION_GLASGOW_HASKELL) && (MIN_VERSION_GLASGOW_HASKELL(8,8,1,0)))
-  "lts-16.31" -- GHC 8.8.4
-#elif (defined(MIN_VERSION_GLASGOW_HASKELL) && (MIN_VERSION_GLASGOW_HASKELL(8,6,5,0)))
-  "lts-14.27" -- GHC 8.6.5
-#elif (defined(MIN_VERSION_GLASGOW_HASKELL) && (MIN_VERSION_GLASGOW_HASKELL(8,6,4,0)))
-  "lts-13.19" -- GHC 8.6.4
 #endif
 
 -- ------------------------------------------------------------------