diff --git a/app/Foliage/CmdBuild.hs b/app/Foliage/CmdBuild.hs
index 067895a..e627898 100644
--- a/app/Foliage/CmdBuild.hs
+++ b/app/Foliage/CmdBuild.hs
@@ -6,7 +6,7 @@ module Foliage.CmdBuild (cmdBuild) where
 import Codec.Archive.Tar qualified as Tar
 import Codec.Archive.Tar.Entry qualified as Tar
 import Codec.Compression.GZip qualified as GZip
-import Control.Monad (unless, void, when)
+import Control.Monad (forM_, unless, void, when)
 import Data.Aeson qualified as Aeson
 import Data.ByteString qualified as BS
 import Data.ByteString.Lazy qualified as BL
@@ -92,8 +92,10 @@ buildAction
 
     makeIndexPage outputDir
 
+    makePreferedVersionsFiles outputDir packageVersions
+    -- TODO: mention depreciated versions on the package page ...
     makeAllPackagesPage currentTime outputDir packageVersions
-
+    -- ... and on the version page.
     makeAllPackageVersionsPage currentTime outputDir packageVersions
 
     when doWritePackageMeta $
@@ -133,6 +135,7 @@ buildAction
             (IndexPkgMetadata pkgId)
             (fromMaybe currentTime pkgTimestamp)
 
+    -- TODO: add `<package>/preferred-versions` to `01-index.tar`?!
     let tarContents = Tar.write $ sortOn Tar.entryTime (cabalEntries ++ metadataEntries)
     traced "Writing index" $ do
       BL.writeFile (anchorPath outputDirRoot repoLayoutIndexTar) tarContents
@@ -312,3 +315,20 @@ mkTarEntry contents indexFile timestamp =
 anchorPath :: Path Absolute -> (RepoLayout -> RepoPath) -> FilePath
 anchorPath outputDirRoot p =
   toFilePath $ anchorRepoPathLocally outputDirRoot $ p hackageRepoLayout
+
+makePreferedVersionsFiles :: FilePath -> [PreparedPackageVersion] -> Action ()
+makePreferedVersionsFiles outputDir packages = traced "writing prefered versions" $ do
+  forM_ packages $ \package -> do
+    -- TODO: Some logic is missing here ... I want first to have for each
+    -- distinct `pkgName` the list of `pkgVersion` for which
+    -- `pkgVersionDepreciated == False`
+    let PreparedPackageVersion {pkgId} = package
+    let PackageIdentifier {pkgName} = pkgId
+    createDirectoryIfMissing True (outputDir </> "index" </> prettyShow pkgName)
+    Aeson.encodeFile
+      (outputDir </> "index" </> prettyShow pkgName </> "preferred-versions")
+      (generateCabalConstrainsts package)
+
+-- TODO: This function should take a list of package versions as argument?!
+generateCabalConstrainsts :: a -> String
+generateCabalConstrainsts _ = "FIXME ..."
diff --git a/app/Foliage/PreparePackageVersion.hs b/app/Foliage/PreparePackageVersion.hs
index 854bdda..f20baee 100644
--- a/app/Foliage/PreparePackageVersion.hs
+++ b/app/Foliage/PreparePackageVersion.hs
@@ -39,6 +39,7 @@ data PreparedPackageVersion = PreparedPackageVersion
     pkgTimestamp :: Maybe UTCTime,
     pkgVersionSource :: PackageVersionSource,
     pkgVersionForce :: Bool,
+    pkgVersionDepreciated :: Bool,
     pkgDesc :: GenericPackageDescription,
     sdistPath :: FilePath,
     cabalFilePath :: FilePath,
@@ -124,6 +125,7 @@ preparePackageVersion inputDir metaFile = do
         pkgTimestamp = packageVersionTimestamp pkgSpec,
         pkgVersionSource = packageVersionSource pkgSpec,
         pkgVersionForce = packageVersionForce pkgSpec,
+        pkgVersionDepreciated = False, -- TODO: should parse `[deprecated]` sections in `meta.toml`
         pkgDesc,
         sdistPath,
         cabalFilePath,