diff --git a/hnix-store-remote/hnix-store-remote.cabal b/hnix-store-remote/hnix-store-remote.cabal
index 6a1aaf71..3f0c18f4 100644
--- a/hnix-store-remote/hnix-store-remote.cabal
+++ b/hnix-store-remote/hnix-store-remote.cabal
@@ -76,6 +76,7 @@ library
     , System.Nix.Store.Remote
     , System.Nix.Store.Remote.Arbitrary
     , System.Nix.Store.Remote.Client
+    , System.Nix.Store.Remote.GADT
     , System.Nix.Store.Remote.Logger
     , System.Nix.Store.Remote.MonadStore
     , System.Nix.Store.Remote.Serialize
diff --git a/hnix-store-remote/src/System/Nix/Store/Remote/GADT.hs b/hnix-store-remote/src/System/Nix/Store/Remote/GADT.hs
new file mode 100644
index 00000000..867e64d3
--- /dev/null
+++ b/hnix-store-remote/src/System/Nix/Store/Remote/GADT.hs
@@ -0,0 +1,150 @@
+{-# language GADTs #-}
+{-# language Rank2Types #-}
+
+module System.Nix.Store.Remote.GADT
+  ( StoreRequest(..)
+  ) where
+
+import Control.Monad.IO.Class (MonadIO)
+import Data.ByteString (ByteString)
+import Data.HashSet (HashSet)
+import Data.Kind (Type)
+import Data.Map (Map)
+import Data.Set (Set)
+import Data.Text (Text)
+import Data.Some (Some)
+
+import System.Nix.Build (BuildMode, BuildResult)
+import System.Nix.Derivation (Derivation)
+import System.Nix.DerivedPath (DerivedPath)
+import System.Nix.Hash (HashAlgo)
+import System.Nix.Nar (NarSource)
+import System.Nix.Store.Types (RepairMode)
+import System.Nix.StorePath (StorePath, StorePathName, StorePathHashPart)
+import System.Nix.StorePath.Metadata (Metadata)
+import System.Nix.Store.Remote.Types.CheckMode (CheckMode)
+import System.Nix.Store.Remote.Types.SubstituteMode (SubstituteMode)
+
+data StoreRequest :: Type -> Type where
+  -- | Add @NarSource@ to the store.
+  AddToStore
+    :: StorePathName -- ^ Name part of the newly created @StorePath@
+    -> Bool -- ^ Add target directory recursively
+    -> Some HashAlgo
+    -> (forall m . MonadIO m => NarSource m) -- ^ provide nar stream
+    -> RepairMode -- ^ Only used by local store backend
+    -> StoreRequest StorePath
+
+  -- | Add text to store.
+  --
+  -- Reference accepts repair but only uses it
+  -- to throw error in case of remote talking to nix-daemon.
+  AddTextToStore
+    :: Text -- ^ Name of the text
+    -> Text -- ^ Actual text to add
+    -> HashSet StorePath -- ^ Set of @StorePath@s that the added text references
+    -> RepairMode -- ^ Repair mode, must be @RepairMode_DontRepair@ in case of remote backend
+    -> StoreRequest StorePath
+
+  AddSignatures
+    :: StorePath
+    -> [ByteString]
+    -> StoreRequest ()
+
+  -- | Add temporary garbage collector root.
+  --
+  -- This root is removed as soon as the client exits.
+  AddIndirectRoot
+    :: StorePath
+    -> StoreRequest ()
+
+  AddTempRoot
+    :: StorePath
+    -> StoreRequest ()
+
+  -- | Build paths if they are an actual derivations.
+  --
+  -- If derivation output paths are already valid, do nothing.
+  BuildPaths
+    :: Set DerivedPath
+    -> BuildMode
+    -> StoreRequest ()
+
+  BuildDerivation
+    :: StorePath
+    -> Derivation StorePath Text
+    -> BuildMode
+    -> StoreRequest BuildResult
+
+  EnsurePath
+    :: StorePath
+    -> StoreRequest ()
+
+  -- | Find garbage collector roots.
+  FindRoots
+    :: StoreRequest (Map ByteString StorePath)
+
+  IsValidPath
+    :: StorePath
+    -> StoreRequest Bool
+
+  -- | Query valid paths from set, optionally try to use substitutes.
+  QueryValidPaths
+    :: HashSet StorePath
+    -- ^ Set of @StorePath@s to query
+    -> SubstituteMode
+    -- ^ Try substituting missing paths when @SubstituteMode_DoSubstitute@
+    -> StoreRequest (HashSet StorePath)
+
+  QueryAllValidPaths
+    :: StoreRequest (HashSet StorePath)
+
+  QuerySubstitutablePaths
+    :: HashSet StorePath
+    -> StoreRequest (HashSet StorePath)
+
+  QueryPathInfo
+    :: StorePath
+    -> StoreRequest (Maybe (Metadata StorePath))
+
+  QueryReferrers
+    :: StorePath
+    -> StoreRequest (HashSet StorePath)
+
+  QueryValidDerivers
+    :: StorePath
+    -> StoreRequest (HashSet StorePath)
+
+  QueryDerivationOutputs
+    :: StorePath
+    -> StoreRequest (HashSet StorePath)
+
+  QueryDerivationOutputNames
+    :: StorePath
+    -> StoreRequest (HashSet StorePathName)
+
+  QueryPathFromHashPart
+    :: StorePathHashPart
+    -> StoreRequest StorePath
+
+  QueryMissing
+    :: Set DerivedPath
+    -> StoreRequest
+      ( HashSet StorePath -- Paths that will be built
+      , HashSet StorePath -- Paths that have substitutes
+      , HashSet StorePath -- Unknown paths
+      , Integer -- Download size
+      , Integer -- Nar size?
+      )
+
+  OptimiseStore
+    :: StoreRequest ()
+
+  SyncWithGC
+    :: StoreRequest ()
+
+  -- returns True on errors
+  VerifyStore
+    :: CheckMode
+    -> RepairMode
+    -> StoreRequest Bool