diff --git a/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs b/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs
index 09d101923..6ca0b0733 100644
--- a/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs
@@ -59,6 +59,7 @@ import Unison.Codebase.Editor.HandleInput.CommitMerge (handleCommitMerge)
 import Unison.Codebase.Editor.HandleInput.CommitUpgrade (handleCommitUpgrade)
 import Unison.Codebase.Editor.HandleInput.DebugDefinition qualified as DebugDefinition
 import Unison.Codebase.Editor.HandleInput.DebugFoldRanges qualified as DebugFoldRanges
+import Unison.Codebase.Editor.HandleInput.DebugSynhashTerm (handleDebugSynhashTerm)
 import Unison.Codebase.Editor.HandleInput.DeleteBranch (handleDeleteBranch)
 import Unison.Codebase.Editor.HandleInput.DeleteProject (handleDeleteProject)
 import Unison.Codebase.Editor.HandleInput.EditNamespace (handleEditNamespace)
@@ -947,6 +948,7 @@ loop e = do
             UpgradeI old new -> handleUpgrade old new
             UpgradeCommitI -> handleCommitUpgrade
             LibInstallI remind libdep -> handleInstallLib remind libdep
+            DebugSynhashTermI name -> handleDebugSynhashTerm name
 
 inputDescription :: Input -> Cli Text
 inputDescription input =
@@ -1059,7 +1061,17 @@ inputDescription input =
     CreateAuthorI id name -> pure ("create.author " <> NameSegment.toEscapedText id <> " " <> name)
     ClearI {} -> pure "clear"
     DocToMarkdownI name -> pure ("debug.doc-to-markdown " <> Name.toText name)
-    --
+    DebugTermI verbose hqName ->
+      if verbose
+        then pure ("debug.term.verbose " <> HQ.toText hqName)
+        else pure ("debug.term " <> HQ.toText hqName)
+    DebugTypeI hqName -> pure ("debug.type " <> HQ.toText hqName)
+    DebugLSPFoldRangesI -> pure "debug.lsp.fold-ranges"
+    DebugFuzzyOptionsI cmd input -> pure . Text.pack $ "debug.fuzzy-completions " <> unwords (cmd : toList input)
+    DebugFormatI -> pure "debug.format"
+    EditNamespaceI paths ->
+      pure $ Text.unwords ("edit.namespace" : (Path.toText <$> paths))
+    -- wat land
     ApiI -> wat
     AuthLoginI {} -> wat
     BranchI {} -> wat
@@ -1071,18 +1083,11 @@ inputDescription input =
     DebugDoctorI {} -> wat
     DebugDumpNamespaceSimpleI {} -> wat
     DebugDumpNamespacesI {} -> wat
-    DebugTermI verbose hqName ->
-      if verbose
-        then pure ("debug.term.verbose " <> HQ.toText hqName)
-        else pure ("debug.term " <> HQ.toText hqName)
-    DebugTypeI hqName -> pure ("debug.type " <> HQ.toText hqName)
-    DebugLSPFoldRangesI -> pure "debug.lsp.fold-ranges"
+    DebugLSPNameCompletionI {} -> wat
     DebugNameDiffI {} -> wat
     DebugNumberedArgsI {} -> wat
-    DebugTabCompletionI _input -> wat
-    DebugLSPNameCompletionI _prefix -> wat
-    DebugFuzzyOptionsI cmd input -> pure . Text.pack $ "debug.fuzzy-completions " <> unwords (cmd : toList input)
-    DebugFormatI -> pure "debug.format"
+    DebugSynhashTermI {} -> wat
+    DebugTabCompletionI {} -> wat
     DebugTypecheckedUnisonFileI {} -> wat
     DiffNamespaceI {} -> wat
     DisplayI {} -> wat
@@ -1090,15 +1095,13 @@ inputDescription input =
     DocsToHtmlI {} -> wat
     FindI {} -> wat
     FindShallowI {} -> wat
-    StructuredFindI {} -> wat
-    StructuredFindReplaceI {} -> wat
     HistoryI {} -> wat
     LibInstallI {} -> wat
     ListDependenciesI {} -> wat
     ListDependentsI {} -> wat
     LoadI {} -> wat
-    MergeI {} -> wat
     MergeCommitI {} -> wat
+    MergeI {} -> wat
     NamesI {} -> wat
     NamespaceDependenciesI {} -> wat
     PopBranchI {} -> wat
@@ -1114,16 +1117,16 @@ inputDescription input =
     QuitI {} -> wat
     ReleaseDraftI {} -> wat
     ShowDefinitionI {} -> wat
-    EditNamespaceI paths ->
-      pure $ Text.unwords ("edit.namespace" : (Path.toText <$> paths))
     ShowReflogI {} -> wat
+    StructuredFindI {} -> wat
+    StructuredFindReplaceI {} -> wat
     SwitchBranchI {} -> wat
     TestI {} -> wat
     TodoI {} -> wat
     UiI {} -> wat
     UpI {} -> wat
-    UpgradeI {} -> wat
     UpgradeCommitI {} -> wat
+    UpgradeI {} -> wat
     VersionI -> wat
   where
     hp' :: Either SCH.ShortCausalHash Path' -> Cli Text
diff --git a/unison-cli/src/Unison/Codebase/Editor/HandleInput/DebugSynhashTerm.hs b/unison-cli/src/Unison/Codebase/Editor/HandleInput/DebugSynhashTerm.hs
new file mode 100644
index 000000000..8f2a24e30
--- /dev/null
+++ b/unison-cli/src/Unison/Codebase/Editor/HandleInput/DebugSynhashTerm.hs
@@ -0,0 +1,65 @@
+-- | @debug.synhash.term@ input handler.
+module Unison.Codebase.Editor.HandleInput.DebugSynhashTerm
+  ( handleDebugSynhashTerm,
+  )
+where
+
+import Control.Monad.Reader (ask)
+import U.Util.Base32Hex qualified as Base32Hex
+import Unison.Cli.Monad (Cli)
+import Unison.Cli.Monad qualified as Cli
+import Unison.Cli.MonadUtils qualified as Cli
+import Unison.Cli.Pretty (prettyBase32Hex, prettyHash)
+import Unison.Cli.PrettyPrintUtils qualified as Cli
+import Unison.Codebase qualified as Codebase
+import Unison.Codebase.Branch.Names qualified as Branch
+import Unison.Codebase.Editor.Output (Output (..))
+import Unison.Hash (Hash)
+import Unison.Hashable qualified as Hashable
+import Unison.Merge.Synhash (hashBuiltinTermTokens, hashDerivedTermTokens)
+import Unison.Name (Name)
+import Unison.Names qualified as Names
+import Unison.Prelude
+import Unison.PrettyPrintEnvDecl (PrettyPrintEnvDecl (..))
+import Unison.Reference qualified as Reference
+import Unison.Util.Pretty (ColorText, Pretty)
+import Unison.Util.Pretty qualified as Pretty
+import qualified Data.Text as Text
+import qualified Data.Text.IO as Text
+import qualified Unison.Syntax.Name as Name
+
+handleDebugSynhashTerm :: Name -> Cli ()
+handleDebugSynhashTerm name = do
+  namespace <- Cli.getCurrentBranch0
+  let names = Branch.toNames namespace
+  pped <- Cli.prettyPrintEnvDeclFromNames names
+
+  for_ (Names.refTermsNamed names name) \ref -> do
+    maybeTokens <-
+      case ref of
+        Reference.Builtin builtin -> pure (Just (hashBuiltinTermTokens builtin))
+        Reference.DerivedId refId -> do
+          env <- ask
+          Cli.runTransaction (Codebase.getTerm env.codebase refId) <&> \case
+            Nothing -> Nothing
+            Just term -> Just (hashDerivedTermTokens pped.unsuffixifiedPPE term)
+    whenJust maybeTokens \tokens -> do
+      let filename = Name.toText name <> "-" <> Reference.toText ref <> "-synhash-tokens.txt"
+      let renderedTokens =
+            tokens
+              & map prettyToken
+              & Pretty.lines
+              & Pretty.toAnsiUnbroken
+              & Text.pack
+      liftIO (Text.writeFile (Text.unpack filename) renderedTokens)
+      Cli.respond (Output'DebugSynhashTerm ref (Hashable.accumulate tokens) filename)
+
+prettyToken :: Hashable.Token Hash -> Pretty ColorText
+prettyToken = \case
+  Hashable.Bytes bytes -> "0x" <> prettyBase32Hex (Base32Hex.fromByteString bytes)
+  Hashable.Double n -> Pretty.string (show n)
+  Hashable.Hashed h -> prettyHash h
+  Hashable.Int n -> (if n >= 0 then "+" else mempty) <> Pretty.string (show n)
+  Hashable.Nat n -> Pretty.string (show n)
+  Hashable.Tag n -> "@" <> Pretty.string (show n)
+  Hashable.Text s -> Pretty.string (show s)
diff --git a/unison-cli/src/Unison/Codebase/Editor/HandleInput/Merge2.hs b/unison-cli/src/Unison/Codebase/Editor/HandleInput/Merge2.hs
index ceee0aa83..f263bd660 100644
--- a/unison-cli/src/Unison/Codebase/Editor/HandleInput/Merge2.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/HandleInput/Merge2.hs
@@ -1,3 +1,4 @@
+-- | @merge@ input handler.
 module Unison.Codebase.Editor.HandleInput.Merge2
   ( handleMerge,
 
diff --git a/unison-cli/src/Unison/Codebase/Editor/HandleInput/Update2.hs b/unison-cli/src/Unison/Codebase/Editor/HandleInput/Update2.hs
index b0dd664a2..25f6de570 100644
--- a/unison-cli/src/Unison/Codebase/Editor/HandleInput/Update2.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/HandleInput/Update2.hs
@@ -1,3 +1,4 @@
+-- | @update@ input handler.
 module Unison.Codebase.Editor.HandleInput.Update2
   ( handleUpdate2,
 
diff --git a/unison-cli/src/Unison/Codebase/Editor/HandleInput/Upgrade.hs b/unison-cli/src/Unison/Codebase/Editor/HandleInput/Upgrade.hs
index 7785e386d..70e247544 100644
--- a/unison-cli/src/Unison/Codebase/Editor/HandleInput/Upgrade.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/HandleInput/Upgrade.hs
@@ -1,3 +1,4 @@
+-- | @upgrade@ input handler.
 module Unison.Codebase.Editor.HandleInput.Upgrade
   ( handleUpgrade,
   )
diff --git a/unison-cli/src/Unison/Codebase/Editor/Input.hs b/unison-cli/src/Unison/Codebase/Editor/Input.hs
index d9278b058..c2ac1a407 100644
--- a/unison-cli/src/Unison/Codebase/Editor/Input.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/Input.hs
@@ -230,6 +230,7 @@ data Input
       !(ProjectAndBranch ProjectName (Maybe ProjectBranchNameOrLatestRelease))
   | UpgradeCommitI
   | MergeCommitI
+  | DebugSynhashTermI !Name
   deriving (Eq, Show)
 
 -- | The source of a `branch` command: what to make the new branch from.
diff --git a/unison-cli/src/Unison/Codebase/Editor/Output.hs b/unison-cli/src/Unison/Codebase/Editor/Output.hs
index 78d2cac1c..1eb7fda3c 100644
--- a/unison-cli/src/Unison/Codebase/Editor/Output.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/Output.hs
@@ -50,6 +50,7 @@ import Unison.Codebase.ShortCausalHash qualified as SCH
 import Unison.CommandLine.InputPattern qualified as Input
 import Unison.DataDeclaration qualified as DD
 import Unison.DataDeclaration.ConstructorId (ConstructorId)
+import Unison.Hash (Hash)
 import Unison.HashQualified qualified as HQ
 import Unison.HashQualified' qualified as HQ'
 import Unison.LabeledDependency (LabeledDependency)
@@ -186,15 +187,15 @@ data Output
   | -- | Function found, but has improper type
     -- Note: the constructor name is misleading here; we weren't necessarily looking for a "main".
     BadMainFunction
-      -- | what we were trying to do (e.g. "run", "io.test")
       Text
-      -- | name of function
+      -- ^ what we were trying to do (e.g. "run", "io.test")
       (HQ.HashQualified Name)
-      -- | bad type of function
+      -- ^ name of function
       (Type Symbol Ann)
+      -- ^ bad type of function
       PPE.PrettyPrintEnv
-      -- | acceptable type(s) of function
       [Type Symbol Ann]
+      -- ^ acceptable type(s) of function
   | BranchEmpty WhichBranchEmpty
   | LoadPullRequest (ReadRemoteNamespace Void) (ReadRemoteNamespace Void) Path' Path' Path' Path'
   | CreatedNewBranch Path.Absolute
@@ -231,12 +232,12 @@ data Output
     -- for terms. This additional info is used to provide an enhanced
     -- error message.
     SearchTermsNotFoundDetailed
-      -- | @True@ if we are searching for a term, @False@ if we are searching for a type
       Bool
-      -- | Misses (search terms that returned no hits for terms or types)
+      -- ^ @True@ if we are searching for a term, @False@ if we are searching for a type
       [HQ.HashQualified Name]
-      -- | Hits for types if we are searching for terms or terms if we are searching for types
+      -- ^ Misses (search terms that returned no hits for terms or types)
       [HQ.HashQualified Name]
+      -- ^ Hits for types if we are searching for terms or terms if we are searching for types
   | -- ask confirmation before deleting the last branch that contains some defns
     -- `Path` is one of the paths the user has requested to delete, and is paired
     -- with whatever named definitions would not have any remaining names if
@@ -385,8 +386,8 @@ data Output
   | CalculatingDiff
   | -- | The `local` in a `clone remote local` is ambiguous
     AmbiguousCloneLocal
-      -- | Treating `local` as a project. We may know the branch name, if it was provided in `remote`.
       (ProjectAndBranch ProjectName ProjectBranchName)
+      -- ^ Treating `local` as a project. We may know the branch name, if it was provided in `remote`.
       (ProjectAndBranch ProjectName ProjectBranchName)
   | -- | The `remote` in a `clone remote local` is ambiguous
     AmbiguousCloneRemote ProjectName (ProjectAndBranch ProjectName ProjectBranchName)
@@ -426,6 +427,7 @@ data Output
   | UseLibInstallNotPull !(ProjectAndBranch ProjectName ProjectBranchName)
   | PullIntoMissingBranch !(ReadRemoteNamespace Share.RemoteProjectBranch) !(ProjectAndBranch (Maybe ProjectName) ProjectBranchName)
   | NoMergeInProgress
+  | Output'DebugSynhashTerm !TermReference !Hash !Text
 
 data UpdateOrUpgrade = UOUUpdate | UOUUpgrade
 
@@ -665,6 +667,7 @@ isFailure o = case o of
   UseLibInstallNotPull {} -> False
   PullIntoMissingBranch {} -> True
   NoMergeInProgress {} -> True
+  Output'DebugSynhashTerm {} -> False
 
 isNumberedFailure :: NumberedOutput -> Bool
 isNumberedFailure = \case
diff --git a/unison-cli/src/Unison/CommandLine/InputPatterns.hs b/unison-cli/src/Unison/CommandLine/InputPatterns.hs
index a09a6595c..1c8f5a990 100644
--- a/unison-cli/src/Unison/CommandLine/InputPatterns.hs
+++ b/unison-cli/src/Unison/CommandLine/InputPatterns.hs
@@ -3332,6 +3332,19 @@ upgradeCommitInputPattern =
         args -> wrongArgsLength "no arguments" args
     }
 
+debugSynhashTermInputPattern :: InputPattern
+debugSynhashTermInputPattern =
+  InputPattern
+    { patternName = "debug.synhash.term",
+      aliases = [],
+      visibility = I.Hidden,
+      args = [("term", Required, exactDefinitionTermQueryArg)],
+      help = mempty,
+      parse = \case
+        [arg] -> Input.DebugSynhashTermI <$> handleNameArg arg
+        args -> wrongArgsLength "exactly one argument" args
+    }
+
 validInputs :: [InputPattern]
 validInputs =
   sortOn
@@ -3358,6 +3371,7 @@ validInputs =
       debugDoctor,
       debugDumpNamespace,
       debugDumpNamespaceSimple,
+      debugSynhashTermInputPattern,
       debugTerm,
       debugTermVerbose,
       debugType,
diff --git a/unison-cli/src/Unison/CommandLine/OutputMessages.hs b/unison-cli/src/Unison/CommandLine/OutputMessages.hs
index 7c5553c57..c06408578 100644
--- a/unison-cli/src/Unison/CommandLine/OutputMessages.hs
+++ b/unison-cli/src/Unison/CommandLine/OutputMessages.hs
@@ -2159,6 +2159,16 @@ notifyUser dir = \case
           Just targetProject -> prettyProjectAndBranchName (ProjectAndBranch targetProject targetBranch)
   NoMergeInProgress ->
     pure . P.wrap $ "It doesn't look like there's a merge in progress."
+  Output'DebugSynhashTerm ref synhash filename ->
+    pure $
+      "Hash: "
+        <> P.syntaxToColor (prettyReference 120 ref)
+        <> P.newline
+        <> "Synhash: "
+        <> prettyHash synhash
+        <> P.newline
+        <> "Synhash tokens: "
+        <> P.text filename
 
 expectedEmptyPushDest :: WriteRemoteNamespace Void -> Pretty
 expectedEmptyPushDest namespace =
diff --git a/unison-cli/unison-cli.cabal b/unison-cli/unison-cli.cabal
index 97441927c..d0b19db6a 100644
--- a/unison-cli/unison-cli.cabal
+++ b/unison-cli/unison-cli.cabal
@@ -59,6 +59,7 @@ library
       Unison.Codebase.Editor.HandleInput.CommitUpgrade
       Unison.Codebase.Editor.HandleInput.DebugDefinition
       Unison.Codebase.Editor.HandleInput.DebugFoldRanges
+      Unison.Codebase.Editor.HandleInput.DebugSynhashTerm
       Unison.Codebase.Editor.HandleInput.DeleteBranch
       Unison.Codebase.Editor.HandleInput.DeleteProject
       Unison.Codebase.Editor.HandleInput.EditNamespace
diff --git a/unison-core/src/Unison/Hashable.hs b/unison-core/src/Unison/Hashable.hs
index b0d32ce2a..69f7173be 100644
--- a/unison-core/src/Unison/Hashable.hs
+++ b/unison-core/src/Unison/Hashable.hs
@@ -31,6 +31,7 @@ data Token h
   | Double !Double
   | Hashed !h
   | Nat !Word64
+  deriving stock (Show)
 
 class Accumulate h where
   accumulate :: [Token h] -> h
diff --git a/unison-merge/package.yaml b/unison-merge/package.yaml
index 68cb7d072..c31adfcd5 100644
--- a/unison-merge/package.yaml
+++ b/unison-merge/package.yaml
@@ -36,6 +36,7 @@ dependencies:
   - unison-util-cache
   - unison-util-relation
   - vector
+  - witch
   - witherable
 
 library:
diff --git a/unison-merge/src/Unison/Merge/Synhash.hs b/unison-merge/src/Unison/Merge/Synhash.hs
index 6acf835a7..da9a98844 100644
--- a/unison-merge/src/Unison/Merge/Synhash.hs
+++ b/unison-merge/src/Unison/Merge/Synhash.hs
@@ -30,10 +30,15 @@ module Unison.Merge.Synhash
     synhashTerm,
     synhashBuiltinDecl,
     synhashDerivedDecl,
+
+    -- * Exported for debugging
+    hashBuiltinTermTokens,
+    hashDerivedTermTokens,
   )
 where
 
 import Data.Char (ord)
+import Data.List qualified as List
 import Data.Text qualified as Text
 import U.Codebase.Reference (TypeReference)
 import Unison.ABT qualified as ABT
@@ -61,7 +66,7 @@ import Unison.Term qualified as Term
 import Unison.Type (Type)
 import Unison.Type qualified as Type
 import Unison.Var (Var)
-import Unison.Var qualified as Var
+import Witch (unsafeFrom)
 
 type Token = H.Token Hash
 
@@ -80,8 +85,12 @@ synhashBuiltinDecl name =
   H.accumulate [isBuiltinTag, isDeclTag, H.Text name]
 
 hashBuiltinTerm :: Text -> Hash
-hashBuiltinTerm name =
-  H.accumulate [isBuiltinTag, isTermTag, H.Text name]
+hashBuiltinTerm =
+  H.accumulate . hashBuiltinTermTokens
+
+hashBuiltinTermTokens :: Text -> [Token]
+hashBuiltinTermTokens name =
+  [isBuiltinTag, isTermTag, H.Text name]
 
 hashCaseTokens :: PrettyPrintEnv -> Term.MatchCase loc a -> [Token]
 hashCaseTokens ppe (Term.MatchCase pat Nothing _) = H.Tag 0 : hashPatternTokens ppe pat
@@ -108,8 +117,21 @@ hashConstructorNameToken declName conName =
    in H.Text (Name.toText strippedConName)
 
 hashDerivedTerm :: Var v => PrettyPrintEnv -> Term v a -> Hash
-hashDerivedTerm ppe t =
-  H.accumulate $ isNotBuiltinTag : isTermTag : hashTermTokens ppe t
+hashDerivedTerm ppe term =
+  H.accumulate (hashDerivedTermTokens ppe term)
+
+hashDerivedTermTokens :: forall a v. Var v => PrettyPrintEnv -> Term v a -> [Token]
+hashDerivedTermTokens ppe =
+  (isNotBuiltinTag :) . (isTermTag :) . go []
+  where
+    go :: [v] -> Term v a -> [Token]
+    go bound t =
+      H.Tag 255 : case ABT.out t of
+        ABT.Var v -> [H.Tag 0, hashVarToken bound v]
+        -- trick: encode the structure, followed the children as a flat list
+        ABT.Tm f -> H.Tag 1 : hashTermFTokens ppe (void f) <> (toList f >>= go bound)
+        ABT.Cycle c -> H.Tag 2 : go bound c
+        ABT.Abs v body -> H.Tag 3 : go (v : bound) body
 
 hashConstructorType :: ConstructorType -> Token
 hashConstructorType = \case
@@ -117,18 +139,15 @@ hashConstructorType = \case
   CT.Data -> H.Tag 1
 
 hashDataDeclTokens :: Var v => PrettyPrintEnv -> Name -> DataDeclaration v a -> [Token]
-hashDataDeclTokens ppe declName (DD.DataDeclaration modifier _ vs ctors) =
-  hashModifierTokens modifier <> goVs <> (ctors >>= hashConstructorTokens ppe declName)
-  where
-    goVs =
-      hashLengthToken vs : map hashVarToken vs
+hashDataDeclTokens ppe declName (DD.DataDeclaration modifier _ bound ctors) =
+  hashModifierTokens modifier <> (ctors >>= hashConstructorTokens ppe declName bound)
 
 -- separating constructor types with tag of 99, which isn't used elsewhere
-hashConstructorTokens :: Var v => PrettyPrintEnv -> Name -> (a, v, Type v a) -> [Token]
-hashConstructorTokens ppe declName (_, conName, ty) =
+hashConstructorTokens :: Var v => PrettyPrintEnv -> Name -> [v] -> (a, v, Type v a) -> [Token]
+hashConstructorTokens ppe declName bound (_, conName, ty) =
   H.Tag 99
     : hashConstructorNameToken declName (Name.unsafeParseVar conName)
-    : hashTypeTokens ppe ty
+    : hashTypeTokens ppe bound ty
 
 hashDeclTokens :: Var v => PrettyPrintEnv -> Name -> Decl v a -> [Token]
 hashDeclTokens ppe name decl =
@@ -205,19 +224,6 @@ synhashTerm loadTerm ppe = \case
   ReferenceBuiltin builtin -> pure (hashBuiltinTerm builtin)
   ReferenceDerived ref -> hashDerivedTerm ppe <$> loadTerm ref
 
-hashTermTokens :: forall v a. Var v => PrettyPrintEnv -> Term v a -> [Token]
-hashTermTokens ppe =
-  go
-  where
-    go :: Term v a -> [Token]
-    go t =
-      H.Tag 255 : case ABT.out t of
-        ABT.Var v -> [H.Tag 0, hashVarToken v]
-        -- trick: encode the structure, followed the children as a flat list
-        ABT.Tm f -> H.Tag 1 : hashTermFTokens ppe (void f) <> (toList f >>= go)
-        ABT.Cycle c -> H.Tag 2 : go c
-        ABT.Abs v body -> H.Tag 3 : hashVarToken v : go body
-
 hashTermFTokens :: Var v => PrettyPrintEnv -> Term.F v a a () -> [Token]
 hashTermFTokens ppe = \case
   Term.Int n -> [H.Tag 0, H.Int n]
@@ -233,7 +239,7 @@ hashTermFTokens ppe = \case
   Term.Request cr -> [H.Tag 7, hashReferentToken ppe (Referent.Con cr CT.Effect)]
   Term.Handle {} -> [H.Tag 8]
   Term.App {} -> [H.Tag 9]
-  Term.Ann _ ty -> H.Tag 10 : hashTypeTokens ppe ty
+  Term.Ann _ ty -> H.Tag 10 : hashTypeTokens ppe [] ty
   Term.List xs -> [H.Tag 11, hashLengthToken xs]
   Term.If {} -> [H.Tag 12]
   Term.And {} -> [H.Tag 13]
@@ -250,20 +256,20 @@ hashTermFTokens ppe = \case
 -- Two types will have the same syntactic hash if they would
 -- print the the same way under the given pretty-print env.
 synhashType :: Var v => PrettyPrintEnv -> Type v a -> Hash
-synhashType ppe t =
-  H.accumulate $ hashTypeTokens ppe t
+synhashType ppe ty =
+  H.accumulate $ hashTypeTokens ppe [] ty
 
-hashTypeTokens :: forall v a. Var v => PrettyPrintEnv -> Type v a -> [Token]
+hashTypeTokens :: forall v a. Var v => PrettyPrintEnv -> [v] -> Type v a -> [Token]
 hashTypeTokens ppe = go
   where
-    go :: Type v a -> [Token]
-    go t =
+    go :: [v] -> Type v a -> [Token]
+    go bound t =
       H.Tag 254 : case ABT.out t of
-        ABT.Var v -> [H.Tag 0, hashVarToken v]
+        ABT.Var v -> [H.Tag 0, hashVarToken bound v]
         -- trick: encode the structure, followed the children as a flat list
-        ABT.Tm f -> H.Tag 1 : (hashTypeFTokens ppe (void f) <> (toList f >>= go))
-        ABT.Cycle c -> H.Tag 2 : go c
-        ABT.Abs v body -> H.Tag 3 : hashVarToken v : go body
+        ABT.Tm f -> H.Tag 1 : (hashTypeFTokens ppe (void f) <> (toList f >>= go bound))
+        ABT.Cycle c -> H.Tag 2 : go bound c
+        ABT.Abs v body -> H.Tag 3 : go (v : bound) body
 
 hashTypeFTokens :: PrettyPrintEnv -> Type.F () -> [Token]
 hashTypeFTokens ppe = \case
@@ -280,6 +286,8 @@ hashTypeReferenceToken :: PrettyPrintEnv -> TypeReference -> Token
 hashTypeReferenceToken ppe =
   hashHQNameToken . PPE.typeNameOrHashOnlyFq ppe
 
-hashVarToken :: Var v => v -> Token
-hashVarToken =
-  H.Text . Var.name
+hashVarToken :: Var v => [v] -> v -> Token
+hashVarToken bound v =
+  case List.elemIndex v bound of
+    Nothing -> error (reportBug "E633940" ("var " ++ show v ++ " not bound in " ++ show bound))
+    Just index -> H.Nat (unsafeFrom @Int @Word64 index)
diff --git a/unison-merge/unison-merge.cabal b/unison-merge/unison-merge.cabal
index ee5b36f48..83131b33b 100644
--- a/unison-merge/unison-merge.cabal
+++ b/unison-merge/unison-merge.cabal
@@ -105,6 +105,7 @@ library
     , unison-util-cache
     , unison-util-relation
     , vector
+    , witch
     , witherable
   default-language: Haskell2010
   if !os(windows)
diff --git a/unison-src/transcripts/merge.md b/unison-src/transcripts/merge.md
index 164b458f5..4a84996f4 100644
--- a/unison-src/transcripts/merge.md
+++ b/unison-src/transcripts/merge.md
@@ -1645,3 +1645,65 @@ project/bob> merge /alice
 project/carol> merge /bob
 project/carol> history
 ```
+
+```ucm:hide
+.> project.delete project
+```
+
+### Variables named `_`
+
+This test demonstrates a change in syntactic hashing that fixed a bug due to auto-generated variable names for ignored
+results.
+
+```ucm:hide
+scratch/alice> builtins.mergeio lib.builtins
+```
+
+```unison
+ignore : a -> ()
+ignore _ = ()
+
+foo : Nat
+foo = 18
+
+bar : Nat
+bar =
+  ignore "hi"
+  foo + foo
+```
+
+```ucm
+scratch/alice> add
+scratch/alice> branch bob
+```
+
+```unison
+bar : Nat
+bar =
+  ignore "hi"
+  foo + foo + foo
+```
+
+```ucm
+scratch/bob> update
+```
+
+Previously, this update to `foo` would also cause a "real update" on `bar`, its dependent. Now it doesn't, so the merge
+will succeed.
+
+```unison
+foo : Nat
+foo = 19
+```
+
+```ucm
+scratch/alice> update
+```
+
+```ucm
+scratch/alice> merge /bob
+```
+
+```ucm:hide
+.> project.delete scratch
+```
diff --git a/unison-src/transcripts/merge.output.md b/unison-src/transcripts/merge.output.md
index d0251764e..a8a97adb6 100644
--- a/unison-src/transcripts/merge.output.md
+++ b/unison-src/transcripts/merge.output.md
@@ -2121,3 +2121,124 @@ project/carol> history
   3. #dm4u1eokg1
 
 ```
+### Variables named `_`
+
+This test demonstrates a change in syntactic hashing that fixed a bug due to auto-generated variable names for ignored
+results.
+
+```unison
+ignore : a -> ()
+ignore _ = ()
+
+foo : Nat
+foo = 18
+
+bar : Nat
+bar =
+  ignore "hi"
+  foo + foo
+```
+
+```ucm
+
+  Loading changes detected in scratch.u.
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These new definitions are ok to `add`:
+    
+      bar    : Nat
+      foo    : Nat
+      ignore : a -> ()
+
+```
+```ucm
+scratch/alice> add
+
+  ⍟ I've added these definitions:
+  
+    bar    : Nat
+    foo    : Nat
+    ignore : a -> ()
+
+scratch/alice> branch bob
+
+  Done. I've created the bob branch based off of alice.
+  
+  Tip: To merge your work back into the alice branch, first
+       `switch /alice` then `merge /bob`.
+
+```
+```unison
+bar : Nat
+bar =
+  ignore "hi"
+  foo + foo + foo
+```
+
+```ucm
+
+  Loading changes detected in scratch.u.
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These names already exist. You can `update` them to your
+      new definition:
+    
+      bar : Nat
+
+```
+```ucm
+scratch/bob> update
+
+  Okay, I'm searching the branch for code that needs to be
+  updated...
+
+  Done.
+
+```
+Previously, this update to `foo` would also cause a "real update" on `bar`, its dependent. Now it doesn't, so the merge
+will succeed.
+
+```unison
+foo : Nat
+foo = 19
+```
+
+```ucm
+
+  Loading changes detected in scratch.u.
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These names already exist. You can `update` them to your
+      new definition:
+    
+      foo : Nat
+
+```
+```ucm
+scratch/alice> update
+
+  Okay, I'm searching the branch for code that needs to be
+  updated...
+
+  That's done. Now I'm making sure everything typechecks...
+
+  Everything typechecks, so I'm saving the results...
+
+  Done.
+
+```
+```ucm
+scratch/alice> merge /bob
+
+  I merged scratch/bob into scratch/alice.
+
+```