diff --git a/doc/build-helpers/special/buildenv.section.md b/doc/build-helpers/special/buildenv.section.md
index 7ae1dbb94e36..e21898c2a27f 100644
--- a/doc/build-helpers/special/buildenv.section.md
+++ b/doc/build-helpers/special/buildenv.section.md
@@ -12,6 +12,8 @@ For example, [`python.withPackage`](#attributes-on-interpreters-packages) is bas
 
 Unless otherwise noted, arguments can be overridden directly using [`<pkg>.overrideAttrs`](#sec-pkg-overrideAttrs).
 
+`buildEnv` enforces [structured attributes (`{ __structuredAttrs = true; }`)](https://nix.dev/manual/nix/2.18/language/advanced-attributes.html#adv-attr-structuredAttrs).
+
 - `name` or `pname` and `version` (required):
     The name of the environment.
 
diff --git a/doc/release-notes/rl-2605.section.md b/doc/release-notes/rl-2605.section.md
index b7aa319a57e6..247927675053 100644
--- a/doc/release-notes/rl-2605.section.md
+++ b/doc/release-notes/rl-2605.section.md
@@ -80,6 +80,8 @@
 
 - Note that the above `nodePackages` removal also coincides with the removal of `node2nix` and its tooling, which have been deprecated for a long time.
 
+- `buildEnv`-constructed packages now take only [structured attributes (`{ __structuredAttrs = true; }`)](https://nix.dev/manual/nix/2.18/language/advanced-attributes.html#adv-attr-structuredAttrs).
+
 - `xfce.mkXfceDerivation` has been deprecated (i.e. conditioned behind `nixpkgs.config.allowAliases`)
   and will be removed in NixOS 26.11, please use `stdenv.mkDerivation` directly. You can migrate by
   adding `pkg-config`, `xfce4-dev-tools`, and `wrapGAppsHook3` to your `nativeBuildInputs` and
diff --git a/pkgs/build-support/buildenv/builder.pl b/pkgs/build-support/buildenv/builder.pl
index cf4fc875b585..d065ec214e06 100644
--- a/pkgs/build-support/buildenv/builder.pl
+++ b/pkgs/build-support/buildenv/builder.pl
@@ -12,10 +12,35 @@ STDOUT->autoflush(1);
 $SIG{__WARN__} = sub { warn "pkgs.buildEnv warning: ", @_ };
 $SIG{__DIE__}  = sub { die "pkgs.buildEnv error: ", @_ };
 
-my $out = $ENV{"out"};
-my $extraPrefix = $ENV{"extraPrefix"};
+my $out;
+my $extraPrefix;
+my @pathsToLink;
+my $ignoreCollisions;
+my $checkCollisionContents;
+my $ignoreSingleFileOutputs;
+my @chosenOutputsRefs;
+my $extraPathsFrom;
+my $manifest;
 
-my @pathsToLink = @{decode_json $ENV{"pathsToLinkJSON"}};
+if ($ENV{"NIX_ATTRS_JSON_FILE"} // "") {
+    open FILE, $ENV{"NIX_ATTRS_JSON_FILE"} or die "cannot open structured attrs JSON file $ENV{NIX_ATTRS_JSON_FILE}: $!";
+    my $json_text = do { local $/; <FILE> };
+    my $attrsFromJSONRef = decode_json $json_text;
+    close FILE;
+
+    my $outputsRef = $attrsFromJSONRef->{"outputs"};
+    $out = $outputsRef->{"out"} // (values %{$outputsRef})[0];
+    $extraPrefix = $attrsFromJSONRef->{"extraPrefix"};
+    @pathsToLink = @{$attrsFromJSONRef->{"pathsToLink"}};
+    $ignoreCollisions = $attrsFromJSONRef->{"ignoreCollisions"};
+    $checkCollisionContents = $attrsFromJSONRef->{"checkCollisionContents"};
+    $ignoreSingleFileOutputs = $attrsFromJSONRef->{"ignoreSingleFileOutputs"};
+    @chosenOutputsRefs = @{$attrsFromJSONRef->{"chosenOutputs"}};
+    $extraPathsFrom = $attrsFromJSONRef->{"extraPathsFrom"};
+    $manifest = $attrsFromJSONRef->{"manifest"};
+} else {
+    die "missing required environment variable NIX_ATTRS_JSON_FILE";
+}
 
 sub isInPathsToLink($path) {
     $path = "/" if $path eq "";
@@ -210,26 +235,15 @@ sub addPkg($pkgDir, $ignoreCollisions, $checkCollisionContents, $priority, $igno
     }
 }
 
-# Read packages list.
-my $pkgs;
-
-if (exists $ENV{"pkgsPath"}) {
-    open FILE, $ENV{"pkgsPath"};
-    $pkgs = <FILE>;
-    close FILE;
-} else {
-    $pkgs = $ENV{"pkgs"}
-}
-
 # Symlink to the packages that have been installed explicitly by the
 # user.
-for my $pkg (@{decode_json $pkgs}) {
+for my $pkg (@chosenOutputsRefs) {
     for my $path (@{$pkg->{paths}}) {
         addPkg($path,
-               $ENV{"ignoreCollisions"} eq "1",
-               $ENV{"checkCollisionContents"} eq "1",
+               $ignoreCollisions,
+               $checkCollisionContents,
                $pkg->{priority},
-               $ENV{"ignoreSingleFileOutputs"} eq "1")
+               $ignoreSingleFileOutputs)
            if -e $path;
     }
 }
@@ -244,21 +258,20 @@ while (scalar(keys %postponed) > 0) {
     my @pkgDirs = keys %postponed;
     %postponed = ();
     foreach my $pkgDir (sort @pkgDirs) {
-        addPkg($pkgDir, 2, $ENV{"checkCollisionContents"} eq "1", $priorityCounter++, $ENV{"ignoreSingleFileOutputs"} eq "1");
+        addPkg($pkgDir, 2, $checkCollisionContents, $priorityCounter++, $ignoreSingleFileOutputs);
     }
 }
 
-my $extraPathsFilePath = $ENV{"extraPathsFrom"};
-if ($extraPathsFilePath) {
-    open FILE, $extraPathsFilePath or die "cannot open extra paths file $extraPathsFilePath: $!";
+if ($extraPathsFrom) {
+    open FILE, $extraPathsFrom or die "cannot open extra paths file $extraPathsFrom: $!";
 
     while(my $line = <FILE>) {
         chomp $line;
         addPkg($line,
-               $ENV{"ignoreCollisions"} eq "1",
-               $ENV{"checkCollisionContents"} eq "1",
+               $ignoreCollisions,
+               $checkCollisionContents,
                1000,
-               $ENV{"ignoreSingleFileOutputs"} eq "1")
+               $ignoreSingleFileOutputs)
             if -d $line;
     }
 
@@ -286,7 +299,6 @@ foreach my $relName (sort keys %symlinks) {
 print STDERR "created $nrLinks symlinks in user environment\n";
 
 
-my $manifest = $ENV{"manifest"};
 if ($manifest) {
     symlink($manifest, "$out/manifest") or die "cannot create manifest";
 }
diff --git a/pkgs/build-support/buildenv/default.nix b/pkgs/build-support/buildenv/default.nix
index 9b7a828b8293..a645224ffa54 100644
--- a/pkgs/build-support/buildenv/default.nix
+++ b/pkgs/build-support/buildenv/default.nix
@@ -92,6 +92,25 @@ lib.makeOverridable (
           // lib.optionalAttrs (args ? buildInputs) {
             inherit buildInputs;
           };
+      in
+      compatArgs
+      // derivationArgs
+      // {
+        # Explicitly opt in: builder.pl reads all configuration from file $ENV["NIX_ATTRS_JSON_FILE"].
+        __structuredAttrs = true;
+
+        inherit
+          extraOutputsToInstall
+          manifest
+          ignoreCollisions
+          checkCollisionContents
+          ignoreSingleFileOutputs
+          includeClosures
+          meta
+          pathsToLink
+          extraPrefix
+          postBuild
+          ;
 
         chosenOutputs = map (drv: {
           paths =
@@ -115,43 +134,19 @@ lib.makeOverridable (
           # Silently use the original `paths` if `passthru.paths` is missing.
         }) finalAttrs.passthru.paths or paths;
 
-        pathsForClosure = lib.pipe chosenOutputs [
-          (map (p: p.paths))
-          lib.flatten
-          (lib.remove null)
-        ];
-      in
-      compatArgs
-      // derivationArgs
-      // {
-        inherit
-          extraOutputsToInstall
-          manifest
-          ignoreCollisions
-          checkCollisionContents
-          ignoreSingleFileOutputs
-          includeClosures
-          meta
-          pathsToLink
-          extraPrefix
-          postBuild
-          ;
-        pathsToLinkJSON = builtins.toJSON pathsToLink;
-        pkgs = builtins.toJSON chosenOutputs;
-        extraPathsFrom = lib.optionalString finalAttrs.includeClosures (writeClosure pathsForClosure);
-
-        # Explicitly opt out: builder.pl reads all configuration from %ENV,
-        # which is fundamentally incompatible with __structuredAttrs = true.
-        __structuredAttrs = false;
+        extraPathsFrom = lib.optionalString finalAttrs.includeClosures (
+          let
+            pathsForClosure = lib.pipe finalAttrs.chosenOutputs [
+              (map (p: p.paths))
+              lib.flatten
+              (lib.remove null)
+            ];
+          in
+          writeClosure pathsForClosure
+        );
 
         preferLocalBuild = derivationArgs.preferLocalBuild or true;
         allowSubstitutes = derivationArgs.allowSubstitutes or false;
-        passAsFile = [
-          "buildCommand"
-        ]
-        # XXX: The size is somewhat arbitrary
-        ++ lib.optional (lib.stringLength finalAttrs.pkgs >= 128 * 1024) "pkgs"
-        ++ derivationArgs.passAsFile or [ ];
 
         buildCommand = ''
           ${buildPackages.perl}/bin/perl -w ${builder}
diff --git a/pkgs/test/buildenv.nix b/pkgs/test/buildenv.nix
index 8ca7a1d7b2e4..f47abe246446 100644
--- a/pkgs/test/buildenv.nix
+++ b/pkgs/test/buildenv.nix
@@ -275,16 +275,16 @@ let
           touch $out
         '';
 
-    # buildEnv explicitly sets __structuredAttrs = false because builder.pl
-    # reads all inputs from environment variables. Verify the build succeeds
-    # even when derivationArgs tries to enable structuredAttrs.
+    # buildEnv explicitly sets __structuredAttrs = true because builder.pl
+    # reads all inputs from `$NIX_ATTRS_JSON_FILE`.
+    # Verify the build succeeds even when derivationArgs tries to disable structuredAttrs.
     structuredAttrs-overridden =
       pkgs.runCommand "test-buildenv-structuredAttrs-overridden"
         {
           testEnv = buildEnv {
             name = "test-env-structuredAttrs";
             paths = [ pkgs.hello ];
-            derivationArgs.__structuredAttrs = true;
+            derivationArgs.__structuredAttrs = false;
           };
         }
         ''
@@ -313,9 +313,9 @@ let
         '';
   };
 
-  # buildEnv's builder.pl reads all inputs from %ENV, which is
-  # fundamentally incompatible with __structuredAttrs = true.
-  # buildEnv explicitly forces __structuredAttrs = false.
+  # buildEnv's builder.pl reads all inputs from `$NIX_ATTRS_JSON_FILE`,
+  # which requires __structuredAttrs = true.
+  # buildEnv explicitly forces __structuredAttrs = true.
   tests-structuredAttrs = {
     testStructuredAttrsExplicitlyFalse = {
       expr =
@@ -323,7 +323,7 @@ let
           name = "test-env";
           paths = [ ];
         }).__structuredAttrs;
-      expected = false;
+      expected = true;
     };
 
     testStructuredAttrsCantBeOverriddenViaDerivationArgs = {
@@ -331,9 +331,9 @@ let
         (buildEnv {
           name = "test-env";
           paths = [ ];
-          derivationArgs.__structuredAttrs = true;
+          derivationArgs.__structuredAttrs = false;
         }).__structuredAttrs;
-      expected = false;
+      expected = true;
     };
   };
 
diff --git a/pkgs/tools/typesetting/tex/texlive/build-tex-env.sh b/pkgs/tools/typesetting/tex/texlive/build-tex-env.sh
index ec755554b80d..7a2f8c6efa9d 100644
--- a/pkgs/tools/typesetting/tex/texlive/build-tex-env.sh
+++ b/pkgs/tools/typesetting/tex/texlive/build-tex-env.sh
@@ -123,15 +123,13 @@ installtl_do_path_adjustments () {
     ln -s "$texmfdist" "$out"/share/texmf
 
     # generate other outputs
-    local otherOutput otherOutputName
-    local otherOutputs="$otherOutputs"
-    for otherOutputName in $outputs ; do
+    local otherOutputIdx=0 otherOutputName
+    for otherOutputName in "${!outputs[@]}" ; do
         if [[ $otherOutputName == out ]] ; then
             continue
         fi
-        otherOutput="${otherOutputs%% *}"
-        otherOutputs="${otherOutputs#* }"
-        ln -s "$otherOutput" "${!otherOutputName}"
+        ln -s "${otherOutputs[$otherOutputIdx]}" "${outputs[$otherOutputName]}"
+        ((otherOutputIdx++)) || true
     done
 }