diff --git a/flake.nix b/flake.nix
index 6bf1c9d..e41fb50 100644
--- a/flake.nix
+++ b/flake.nix
@@ -55,6 +55,8 @@
 
         devshells.default = internal.devShell.new;
 
+        checks.hlint = internal.hlintCheck;
+
         treefmt = {pkgs, ...}: {
           projectRootFile = "flake.nix";
           programs = {
diff --git a/nix/internal.nix b/nix/internal.nix
index 7ca4b97..1247be6 100644
--- a/nix/internal.nix
+++ b/nix/internal.nix
@@ -123,6 +123,17 @@ assert builtins.elem targetSystem ["x86_64-linux" "aarch64-linux" "aarch64-darwi
       };
     })
     .defaultNix;
+  cardano-node-devshell = cardano-node-flake'.devShells.${buildSystem}.default;
+  cardano-node-inputs = lib.filter lib.isDerivation (
+    (cardano-node-devshell.buildInputs or [])
+    ++ (cardano-node-devshell.nativeBuildInputs or [])
+    ++ (cardano-node-devshell.propagatedBuildInputs or [])
+    ++ (cardano-node-devshell.propagatedNativeBuildInputs or [])
+  );
+  # Extract an individual package from the cardano-node devshell inputs
+  # so we can expose it as a devshell command with its own menu entry.
+  cardano-node-findInput = pred: label:
+    lib.findFirst pred (throw "devshell input '${label}' not found") cardano-node-inputs;
 in rec {
   defaultPackage = testgen-hs;
   cardano-node-flake = cardano-node-flake';
@@ -139,13 +150,6 @@ in rec {
   inherit (cardano-node-packages) cardano-node cardano-cli;
 
   devShell = let
-    cardano-node-devshell = cardano-node-flake.devShells.${buildSystem}.default;
-    cardano-node-inputs = lib.filter lib.isDerivation (
-      (cardano-node-devshell.buildInputs or [])
-      ++ (cardano-node-devshell.nativeBuildInputs or [])
-      ++ (cardano-node-devshell.propagatedBuildInputs or [])
-      ++ (cardano-node-devshell.propagatedNativeBuildInputs or [])
-    );
     cardano-node-env = pkgs.buildEnv {
       name = "cardano-node-devshell-env";
       paths = cardano-node-inputs;
@@ -153,12 +157,7 @@ in rec {
     };
     cardano-node-ghc-libdir = cardano-node-devshell.NIX_GHC_LIBDIR or "";
 
-    # Extract an individual package from the cardano-node devshell inputs
-    # so we can expose it as a devshell command with its own menu entry.
-    findInput = pred: label:
-      lib.findFirst pred (throw "devshell input '${label}' not found") cardano-node-inputs;
-
-    haskell-language-server = findInput (p: (p.pname or "") == "haskell-language-server-exe-haskell-language-server") "haskell-language-server";
+    haskell-language-server = cardano-node-findInput (p: (p.pname or "") == "haskell-language-server-exe-haskell-language-server") "haskell-language-server";
 
     # Shim so that editors looking for haskell-language-server-wrapper find it
     # on PATH; the devshell already sets the correct GHC.
@@ -271,12 +270,12 @@ in rec {
       commands = [
         {
           name = "ghc";
-          package = findInput (p: lib.hasPrefix "ghc-shell-for-packages" (p.name or "")) "ghc";
+          package = cardano-node-findInput (p: lib.hasPrefix "ghc-shell-for-packages" (p.name or "")) "ghc";
           category = "haskell";
         }
         {
           name = "cabal";
-          package = findInput (p: (p.pname or "") == "cabal-install-exe-cabal") "cabal";
+          package = cardano-node-findInput (p: (p.pname or "") == "cabal-install-exe-cabal") "cabal";
           category = "haskell";
         }
         {
@@ -284,6 +283,11 @@ in rec {
           package = haskell-language-server;
           category = "haskell";
         }
+        {
+          name = "hlint";
+          package = cardano-node-findInput (p: (p.pname or "") == "hlint-exe-hlint") "hlint";
+          category = "haskell";
+        }
       ];
       devshell = {
         packages = [
@@ -342,6 +346,17 @@ in rec {
       targetSystem
     };
 
+  hlintCheck = let
+    hlint = cardano-node-findInput (p: (p.pname or "") == "hlint-exe-hlint") "hlint";
+  in
+    pkgs.runCommand "hlint" {
+      nativeBuildInputs = [hlint];
+      src = ../testgen-hs;
+    } ''
+      hlint "$src"
+      touch $out
+    '';
+
   nix-bundle-exe = import inputs.nix-bundle-exe {inherit pkgs;};
 
   nix-bundle-exe--same-dir = let
diff --git a/testgen-hs/CLI.hs b/testgen-hs/CLI.hs
index f65345f..2678128 100644
--- a/testgen-hs/CLI.hs
+++ b/testgen-hs/CLI.hs
@@ -61,45 +61,40 @@ opts =
 commandParser :: Parser Command
 commandParser =
   subparser
-    ( mempty
-        <> ( command
-               "generate"
-               ( info
-                   ( Generate
-                       <$> optionsParser
-                         <**> helper
-                   )
-                   (progDesc "Generate random CBOR test cases")
-               )
-           )
-        <> ( command
-               "deserialize"
-               ( info
-                   ( Deserialize
-                       <$> argument (eitherReader parseHex) (metavar "CBOR_HEX")
-                         <**> helper
-                   )
-                   (progDesc "Deserialize CBOR of ‘HardForkApplyTxErr’ that you got from cardano-node")
-               )
-           )
-        <> ( command
-               "deserialize-stream"
-               ( info
-                   ( pure DeserializeStream
-                       <**> helper
-                   )
-                   (progDesc "Deserialize an STDIN stream of multiple lines of base16-encoded CBOR of ‘HardForkApplyTxErr’")
-               )
-           )
-        <> ( command
-               "evaluate-stream"
-               ( info
-                   ( pure EvaluateStream
-                       <**> helper
-                   )
-                   (progDesc "Evaluate an STDIN stream of Txs with Utxos")
-               )
-           )
+    ( command
+        "generate"
+        ( info
+            ( Generate
+                <$> optionsParser
+                  <**> helper
+            )
+            (progDesc "Generate random CBOR test cases")
+        )
+        <> command
+          "deserialize"
+          ( info
+              ( Deserialize
+                  <$> argument (eitherReader parseHex) (metavar "CBOR_HEX")
+                    <**> helper
+              )
+              (progDesc "Deserialize CBOR of 'HardForkApplyTxErr' that you got from cardano-node")
+          )
+        <> command
+          "deserialize-stream"
+          ( info
+              ( pure DeserializeStream
+                  <**> helper
+              )
+              (progDesc "Deserialize an STDIN stream of multiple lines of base16-encoded CBOR of 'HardForkApplyTxErr'")
+          )
+        <> command
+          "evaluate-stream"
+          ( info
+              ( pure EvaluateStream
+                  <**> helper
+              )
+              (progDesc "Evaluate an STDIN stream of Txs with Utxos")
+          )
     )
 
 optionsParser :: Parser GenerateOptions
@@ -122,7 +117,7 @@ optionsParser =
                   <> short 'g'
                   <> metavar "SIZE"
                   <> value 300
-                  <> help "Set the relative ‘size’ of the test cases"
+                  <> help "Set the relative 'size' of the test cases"
               )
         )
     <*> ( NumCases
@@ -147,8 +142,7 @@ positive = do
 typeCommandParser :: Parser TypeCommand
 typeCommandParser =
   subparser
-    ( mempty
-        <> mkTypeCommand Tx'ConwayDummy
+    ( mkTypeCommand Tx'ConwayDummy
         <> mkTypeCommand ApplyTxErr'Byron
         <> mkTypeCommand ApplyTxErr'Shelley
         <> mkTypeCommand ApplyTxErr'Allegra
diff --git a/testgen-hs/Evaluation.hs b/testgen-hs/Evaluation.hs
index ab4afe8..340e178 100644
--- a/testgen-hs/Evaluation.hs
+++ b/testgen-hs/Evaluation.hs
@@ -1,7 +1,6 @@
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# OPTIONS_GHC -Wno-orphans #-}
diff --git a/testgen-hs/Generators.hs b/testgen-hs/Generators.hs
index a234fef..c1e87f3 100644
--- a/testgen-hs/Generators.hs
+++ b/testgen-hs/Generators.hs
@@ -192,13 +192,12 @@ instance OurCBOR Tx'Conway where
 ------- HardForkApplyTxErr -----------------------------------------------------
 
 hfcEnvelope :: OCHCM.HardForkApplyTxErr (OCCB.CardanoEras OCCB.StandardCrypto) -> C.Encoding
-hfcEnvelope wrapped =
+hfcEnvelope =
   OCNS.encodeNodeToClient
     @(OCCB.HardForkBlock (OCCB.CardanoEras OCCB.StandardCrypto))
     @(OCHCM.HardForkApplyTxErr (OCCB.CardanoEras OCCB.StandardCrypto))
     codecConfig
     OCCN.CardanoNodeToClientVersion12
-    wrapped
   where
     byronEpochSlots = CCS.EpochSlots 21600 -- probably safe to hardcode in Conway…?
     codecConfig = OCNPI.pClientInfoCodecConfig (OCCN.protocolClientInfoCardano byronEpochSlots)
diff --git a/testgen-hs/SynthEvalTx.hs b/testgen-hs/SynthEvalTx.hs
index 1411cf0..0d6d42e 100644
--- a/testgen-hs/SynthEvalTx.hs
+++ b/testgen-hs/SynthEvalTx.hs
@@ -77,8 +77,8 @@ genTxUTxO = do
   pure (tx, stubUTxO tx)
 
 eval'Conway ::
-  (Cardano.Ledger.Core.Tx (Cardano.Ledger.Api.Era.ConwayEra)) ->
-  UTxO (Cardano.Ledger.Api.Era.ConwayEra) ->
+  Cardano.Ledger.Core.Tx Cardano.Ledger.Api.Era.ConwayEra ->
+  UTxO Cardano.Ledger.Api.Era.ConwayEra ->
   EpochInfo (Either Text) ->
   SystemStart ->
   J.Value
@@ -87,17 +87,17 @@ eval'Conway tx utxo epochInfo systemStart =
     Just v -> v
     Nothing -> error "ogmiosSuccess produced invalid JSON"
   where
-    redeemerReport :: RedeemerReport (Cardano.Ledger.Api.Era.ConwayEra)
+    redeemerReport :: RedeemerReport Cardano.Ledger.Api.Era.ConwayEra
     redeemerReport = evalTxExUnits protocolParams tx utxo epochInfo systemStart
 
 -- | Version of eval'Conway that uses dummy epoch info and system start
-eval'ConwayDummy :: (Cardano.Ledger.Core.Tx (Cardano.Ledger.Api.Era.ConwayEra)) -> UTxO Cardano.Ledger.Api.Era.ConwayEra -> J.Value
+eval'ConwayDummy :: Cardano.Ledger.Core.Tx Cardano.Ledger.Api.Era.ConwayEra -> UTxO Cardano.Ledger.Api.Era.ConwayEra -> J.Value
 eval'ConwayDummy tx utxo =
   case J.decode (AesonEncoding.encodingToLazyByteString (ogmiosSuccess redeemerReport)) of
     Just v -> v
     Nothing -> error "ogmiosSuccess produced invalid JSON"
   where
-    redeemerReport :: RedeemerReport (Cardano.Ledger.Api.Era.ConwayEra)
+    redeemerReport :: RedeemerReport Cardano.Ledger.Api.Era.ConwayEra
     redeemerReport = evalTxExUnits protocolParams tx utxo dummyEpochInfo dummySystemStart
 
 -- | Collect every input the Tx spends, in any role.
@@ -137,7 +137,7 @@ dummySystemStart =
 protocolParamsJSON :: BS.ByteString
 protocolParamsJSON = $(embedFile =<< makeRelativeToProject "protocol-params-preview.json")
 
-protocolParams :: PParams (Cardano.Ledger.Api.Era.ConwayEra)
+protocolParams :: PParams Cardano.Ledger.Api.Era.ConwayEra
 protocolParams =
   case eitherDecodeStrict' protocolParamsJSON of
     Left err -> error $ "Embedded protocol-parameters JSON is malformed:\n" <> err