diff --git a/syncon-parser/exe/Main.hs b/syncon-parser/exe/Main.hs
index 4d99755..262bee9 100644
--- a/syncon-parser/exe/Main.hs
+++ b/syncon-parser/exe/Main.hs
@@ -609,6 +609,9 @@ composeCommand = Opt.command "compose" (Opt.info composeCmd $ Opt.progDesc "Crea
         <> Opt.metavar "N"
         <> Opt.help "The minimum number of language fragments present in the composition, including the base fragment."
         <> Opt.value 10
+      forbidGraph <- Opt.switch
+        $ Opt.long "forbid-graph"
+        <> Opt.help "If supplied, output a graphviz dot graph where fragments are connected by an edge if they forbid each other."
       base <- Opt.argument Opt.str
         $ Opt.metavar "FILE"
         <> Opt.help "The '.syncon' file that defines the base fragment that is to always be present."
@@ -619,12 +622,19 @@ composeCommand = Opt.command "compose" (Opt.info composeCmd $ Opt.progDesc "Crea
       pure $ do
         let baseID = RC.mkID base
         info <- RC.computeInfo (base : others) >>= dataOrError mempty ()
-        case dirPath of
-          Nothing -> RC.generateComposition count baseID info
-            >>= dataOrError mempty ()
-            >>= putStrLn
-          Just path -> RC.writeAllFragmentsToDir path baseID info
-            >>= dataOrError mempty ()
+        let mkSingle = isNothing dirPath && not forbidGraph
+
+        forM_ dirPath $ \path ->
+          RC.writeAllFragmentsToDir path baseID info
+          >>= dataOrError mempty ()
+
+        when forbidGraph $
+          putStr $ RC.graphvizForbidGraph info
+
+        when mkSingle $
+          RC.generateComposition count baseID info
+          >>= dataOrError mempty ()
+          >>= putStrLn
 
 main :: IO ()
 main = join $ Opt.execParser $ Opt.info (Opt.hsubparser (compileCommand <> parseCommand <> devCommand <> pbtCommand <> composeCommand) <**> Opt.helper)
diff --git a/syncon-parser/exe/RandomCompose.hs b/syncon-parser/exe/RandomCompose.hs
index ca1b105..d86f0f5 100644
--- a/syncon-parser/exe/RandomCompose.hs
+++ b/syncon-parser/exe/RandomCompose.hs
@@ -4,6 +4,7 @@ module RandomCompose
 , computeInfo
 , writeAllFragmentsToDir
 , generateComposition
+, graphvizForbidGraph
 ) where
 
 import Pre hiding (state, (<.>))
@@ -106,6 +107,21 @@ data ComposeState = ComposeState
   , pickable :: !(HashSet ID)
   }
 
+graphvizForbidGraph :: HashMap ID FileInfo -> Text
+graphvizForbidGraph infos =
+  "graph {\n"
+  <> (toList edges <&> mkEdge <&> (<> ";\n") & Text.concat)
+  <> "}\n"
+  where
+    mkNode (ID id) = show id
+    mkEdge (id1, id2) = mkNode id1 <> " -- " <> mkNode id2
+    edges = toList infos
+      >>= (\FileInfo{id, forbidden} -> toList forbidden <&> (id,) <&> sortTuple)
+      & S.fromList
+    sortTuple (a, b)
+      | a < b = (a, b)
+      | otherwise = (b, a)
+
 addID :: HashSet ID -> ID -> StateT ComposeState (Result (HashSet Error)) (HashSet ID)
 addID picked id
   | id `S.member` picked = return picked