diff --git a/primer/src/Primer/API.hs b/primer/src/Primer/API.hs
index 5b3979a4f..455578e5b 100644
--- a/primer/src/Primer/API.hs
+++ b/primer/src/Primer/API.hs
@@ -59,7 +59,6 @@ import Control.Monad.Fix (MonadFix)
 import Control.Monad.Trans (MonadTrans)
 import Control.Monad.Writer (MonadWriter)
 import Control.Monad.Zip (MonadZip)
-import Data.Aeson (ToJSON)
 import Data.Map qualified as Map
 import Data.Text qualified as T
 import ListT qualified (toList)
@@ -139,6 +138,11 @@ import Primer.Database qualified as Database (
     Success
   ),
  )
+import Primer.JSON (
+  CustomJSON (..),
+  PrimerJSON,
+  ToJSON,
+ )
 import Primer.Module (moduleDefsQualified, moduleName, moduleTypesQualified)
 import Primer.Name (Name, unName)
 import StmContainers.Map qualified as StmMap
@@ -383,8 +387,7 @@ data Tree = Tree
   -- ^ a special subtree to be rendered to the right, rather than below - useful for `case` branches
   }
   deriving (Show, Eq, Generic)
-
-instance ToJSON Tree
+  deriving (ToJSON) via PrimerJSON Tree
 
 -- | The contents of a node.
 data NodeBody
@@ -395,8 +398,7 @@ data NodeBody
   | -- | Some simple nodes, like function application, have no body.
     NoBody
   deriving (Show, Eq, Generic)
-
-instance ToJSON NodeBody
+  deriving (ToJSON) via PrimerJSON NodeBody
 
 -- | An indication of the meaning of a node, which frontend may use for labelling, colour etc.
 -- These mostly correspond to constructors of `Expr'` or `Type'`.
@@ -425,8 +427,7 @@ data NodeFlavor
   | FlavorTForall
   | FlavorPattern
   deriving (Show, Eq, Generic)
-
-instance ToJSON NodeFlavor
+  deriving (ToJSON) via PrimerJSON NodeFlavor
 
 -- | This type is the API's view of a 'App.Prog'
 -- (this is expected to evolve as we flesh out the API)
@@ -434,8 +435,7 @@ newtype Prog = Prog
   { modules :: [Module]
   }
   deriving (Generic)
-
-instance ToJSON Prog
+  deriving (ToJSON) via PrimerJSON Prog
 
 -- | This type is the API's view of a 'Module.Module'
 -- (this is expected to evolve as we flesh out the API)
@@ -450,8 +450,7 @@ data Module = Module
     defs :: [Def]
   }
   deriving (Generic)
-
-instance ToJSON Module
+  deriving (ToJSON) via PrimerJSON Module
 
 -- | This type is the api's view of a 'Primer.Core.Def'
 -- (this is expected to evolve as we flesh out the API)
@@ -462,8 +461,7 @@ data Def = Def
   -- ^ definitions with no associated tree are primitives
   }
   deriving (Generic)
-
-instance ToJSON Def
+  deriving (ToJSON) via PrimerJSON Def
 
 viewProg :: App.Prog -> Prog
 viewProg p =
diff --git a/primer/src/Primer/App.hs b/primer/src/Primer/App.hs
index b90af47c1..5331bbbee 100644
--- a/primer/src/Primer/App.hs
+++ b/primer/src/Primer/App.hs
@@ -54,11 +54,6 @@ module Primer.App (
 import Foreword hiding (mod)
 
 import Control.Monad.Fresh (MonadFresh (..))
-import Data.Aeson (
-  ToJSON (toEncoding),
-  defaultOptions,
-  genericToEncoding,
- )
 import Data.Bitraversable (bimapM)
 import Data.Data (Data)
 import Data.Generics.Uniplate.Operations (descendM, transform, transformM)
@@ -354,7 +349,7 @@ data Selection = Selection
   , selectedNode :: Maybe NodeSelection
   }
   deriving (Eq, Show, Generic, Data)
-  deriving (ToJSON, FromJSON) via PrimerJSON Selection
+  deriving (FromJSON, ToJSON) via PrimerJSON Selection
 
 -- | A selected node, in the body or type signature of some definition.
 -- We have the following invariant: @nodeType = SigNode ==> isRight meta@
@@ -364,11 +359,11 @@ data NodeSelection = NodeSelection
   , meta :: Either ExprMeta TypeMeta
   }
   deriving (Eq, Show, Generic, Data)
-  deriving (ToJSON, FromJSON) via PrimerJSON NodeSelection
+  deriving (FromJSON, ToJSON) via PrimerJSON NodeSelection
 
 data NodeType = BodyNode | SigNode
   deriving (Eq, Show, Generic, Data)
-  deriving (ToJSON, FromJSON) via PrimerJSON NodeType
+  deriving (FromJSON, ToJSON) via PrimerJSON NodeType
 
 -- | The type of requests which can mutate the application state.
 data MutationRequest
@@ -1041,20 +1036,12 @@ runQueryAppM (QueryAppM m) appState = case runExcept (runReaderT m appState) of
 --
 -- Building an 'App' can be tricky, so we don't export the
 -- constructor. See 'mkApp' and 'mkAppSafe'.
---
--- Note that the 'ToJSON' and 'FromJSON' instances for this type are
--- not used in the frontend, and therefore we can use "Data.Aeson"s
--- generic instances for them.
 data App = App
   { currentState :: AppState
   , initialState :: AppState
   }
   deriving (Eq, Show, Generic)
-
-instance ToJSON App where
-  toEncoding = genericToEncoding defaultOptions
-
-instance FromJSON App
+  deriving (FromJSON, ToJSON) via PrimerJSON App
 
 -- Internal app state. Note that this type is not exported, as we want
 -- to guarantee that the counters are kept in sync with the 'Prog',
@@ -1066,11 +1053,7 @@ data AppState = AppState
   , prog :: Prog
   }
   deriving (Eq, Show, Generic)
-
-instance ToJSON AppState where
-  toEncoding = genericToEncoding defaultOptions
-
-instance FromJSON AppState
+  deriving (FromJSON, ToJSON) via PrimerJSON AppState
 
 -- | Construct an 'App' from an 'ID' and a 'Prog'.
 --
diff --git a/primer/src/Primer/Core.hs b/primer/src/Primer/Core.hs
index 80b5a9a0d..e59fbb5c8 100644
--- a/primer/src/Primer/Core.hs
+++ b/primer/src/Primer/Core.hs
@@ -192,9 +192,7 @@ data GlobalName (k :: GlobalNameKind) = GlobalName
   , baseName :: Name
   }
   deriving (Eq, Ord, Generic, Data, Show)
-
-instance FromJSON (GlobalName k)
-instance ToJSON (GlobalName k)
+  deriving (FromJSON, ToJSON) via PrimerJSON (GlobalName k)
 
 -- | Construct a name from a Text. This is called unsafe because there are no
 -- guarantees about whether the name refers to anything that is in scope.
diff --git a/primer/src/Primer/Name.hs b/primer/src/Primer/Name.hs
index e61771ed1..4152002fe 100644
--- a/primer/src/Primer/Name.hs
+++ b/primer/src/Primer/Name.hs
@@ -31,7 +31,8 @@ unsafeMkName :: Text -> Name
 unsafeMkName = Name
 
 newtype NameCounter = NC Natural
-  deriving (Eq, Enum, Show, ToJSON, FromJSON)
+  deriving (Eq, Enum, Show, Generic, Data)
+  deriving newtype (FromJSON, ToJSON)
 
 -- | Generate a new automatic name (distinct from all other names generated by
 -- this function, from the MonadFresh class), and avoiding the given set of
diff --git a/primer/src/Primer/Typecheck.hs b/primer/src/Primer/Typecheck.hs
index 7d1c6f9d2..174782b6b 100644
--- a/primer/src/Primer/Typecheck.hs
+++ b/primer/src/Primer/Typecheck.hs
@@ -178,7 +178,7 @@ assert b s = unless b $ throwError' (InternalError s)
 
 data SmartHoles = SmartHoles | NoSmartHoles
   deriving (Eq, Show, Generic)
-  deriving (ToJSON, FromJSON) via PrimerJSON SmartHoles
+  deriving (FromJSON, ToJSON) via PrimerJSON SmartHoles
 
 data KindOrType = K Kind | T Type
   deriving (Show, Eq)