diff --git a/pkgs/by-name/fe/fex/package.nix b/pkgs/by-name/fe/fex/package.nix
index 4e77947df224..a2186cff8ab1 100644
--- a/pkgs/by-name/fe/fex/package.nix
+++ b/pkgs/by-name/fe/fex/package.nix
@@ -11,8 +11,83 @@
   xxHash,
   fmt,
   nasm,
+  buildEnv,
+  writeText,
+  pkgsCross,
+  libclang,
+  libllvm,
+  alsa-lib,
+  libdrm,
+  libGL,
+  wayland,
+  xorg,
 }:
 
+let
+  # Headers required to build the ThunkLibs subtree
+  libForwardingInputs = lib.map lib.getInclude [
+    alsa-lib
+    libdrm
+    libGL
+    wayland
+    xorg.libX11
+    xorg.libxcb
+    xorg.libXrandr
+    xorg.libXrender
+    xorg.xorgproto
+  ];
+
+  pkgsCross32 = pkgsCross.gnu32;
+  pkgsCross64 = pkgsCross.gnu64;
+  devRootFS = buildEnv {
+    name = "fex-dev-rootfs";
+    paths = [
+      pkgsCross64.stdenv.cc.libc_dev
+      pkgsCross32.stdenv.cc.libc_dev
+      pkgsCross64.stdenv.cc.cc
+      pkgsCross32.stdenv.cc.cc
+    ]
+    ++ libForwardingInputs;
+    ignoreCollisions = true;
+    pathsToLink = [
+      "/include"
+      "/lib"
+    ];
+
+    postBuild = ''
+      mkdir -p $out/usr
+      ln -s $out/include $out/usr/
+    '';
+  };
+
+  toolchain32 = writeText "toolchain_nix_x86_32.txt" ''
+    set(CMAKE_EXE_LINKER_FLAGS_INIT "-fuse-ld=lld")
+    set(CMAKE_MODULE_LINKER_FLAGS_INIT "-fuse-ld=lld")
+    set(CMAKE_SHARED_LINKER_FLAGS_INIT "-fuse-ld=lld")
+    set(CMAKE_SYSTEM_PROCESSOR i686)
+    set(CMAKE_C_COMPILER clang)
+    set(CMAKE_CXX_COMPILER clang++)
+    set(CMAKE_C_COMPILER ${pkgsCross32.buildPackages.clang}/bin/i686-unknown-linux-gnu-clang)
+    set(CMAKE_CXX_COMPILER ${pkgsCross32.buildPackages.clang}/bin/i686-unknown-linux-gnu-clang++)
+    set(CLANG_FLAGS "-nodefaultlibs -nostartfiles -target i686-linux-gnu -msse2 -mfpmath=sse --sysroot=${devRootFS} -iwithsysroot/usr/include")
+    set(CMAKE_C_FLAGS "''${CMAKE_C_FLAGS} ''${CLANG_FLAGS}")
+    set(CMAKE_CXX_FLAGS "''${CMAKE_CXX_FLAGS} ''${CLANG_FLAGS}")
+  '';
+
+  toolchain = writeText "toolchain_nix_x86_64.txt" ''
+    set(CMAKE_EXE_LINKER_FLAGS_INIT "-fuse-ld=lld")
+    set(CMAKE_MODULE_LINKER_FLAGS_INIT "-fuse-ld=lld")
+    set(CMAKE_SHARED_LINKER_FLAGS_INIT "-fuse-ld=lld")
+    set(CMAKE_SYSTEM_PROCESSOR x86_64)
+    set(CMAKE_C_COMPILER clang)
+    set(CMAKE_CXX_COMPILER clang++)
+    set(CMAKE_C_COMPILER ${pkgsCross64.buildPackages.clang}/bin/x86_64-unknown-linux-gnu-clang)
+    set(CMAKE_CXX_COMPILER ${pkgsCross64.buildPackages.clang}/bin/x86_64-unknown-linux-gnu-clang++)
+    set(CLANG_FLAGS "-nodefaultlibs -nostartfiles -target x86_64-linux-gnu --sysroot=${devRootFS} -iwithsysroot/usr/include")
+    set(CMAKE_C_FLAGS "''${CMAKE_C_FLAGS} ''${CLANG_FLAGS}")
+    set(CMAKE_CXX_FLAGS "''${CMAKE_CXX_FLAGS} ''${CLANG_FLAGS}")
+  '';
+in
 llvmPackages.stdenv.mkDerivation (finalAttrs: {
   pname = "fex";
   version = "2508.1";
@@ -49,6 +124,37 @@ llvmPackages.stdenv.mkDerivation (finalAttrs: {
     '';
   };
 
+  postPatch = ''
+    substituteInPlace ThunkLibs/GuestLibs/CMakeLists.txt ThunkLibs/HostLibs/CMakeLists.txt \
+      --replace-fail "/usr/include/libdrm" "${devRootFS}/include/libdrm" \
+      --replace-fail "/usr/include/wayland" "${devRootFS}/include/wayland"
+
+    # Add include paths for thunkgen invocation
+    substituteInPlace ThunkLibs/HostLibs/CMakeLists.txt \
+      --replace-fail "-- " "-- $(cat ${llvmPackages.stdenv.cc}/nix-support/libc-cflags) $(cat ${llvmPackages.stdenv.cc}/nix-support/libcxx-cxxflags) ${
+        lib.concatMapStrings (x: "-isystem " + x + "/include ") libForwardingInputs
+      }"
+    substituteInPlace ThunkLibs/GuestLibs/CMakeLists.txt \
+      --replace-fail "-- " "-- $(cat ${llvmPackages.stdenv.cc}/nix-support/libcxx-cxxflags) "
+
+    # Patch any references to library wrapper paths
+    substituteInPlace FEXCore/Source/Interface/Config/Config.json.in \
+      --replace-fail "ThunkGuestLibs" "UnusedThunkGuestLibs" \
+      --replace-fail "ThunkHostLibs" "UnusedThunkHostLibs"
+    substituteInPlace FEXCore/Source/Interface/Config/Config.cpp \
+      --replace-fail "FEXCore::Config::CONFIG_THUNKGUESTLIBS" "FEXCore::Config::CONFIG_UNUSEDTHUNKGUESTLIBS" \
+      --replace-fail "FEXCore::Config::CONFIG_THUNKHOSTLIBS" "FEXCore::Config::CONFIG_UNUSEDTHUNKHOSTLIBS"
+    substituteInPlace Source/Tools/LinuxEmulation/VDSO_Emulation.cpp \
+      --replace-fail "FEX_CONFIG_OPT(ThunkGuestLibs, THUNKGUESTLIBS);" "auto ThunkGuestLibs = []() { return \"$out/share/fex-emu/GuestThunks/\"; };"
+    substituteInPlace Source/Tools/LinuxEmulation/LinuxSyscalls/FileManagement.h \
+      --replace-fail "FEX_CONFIG_OPT(ThunkGuestLibs, THUNKGUESTLIBS);" "fextl::string ThunkGuestLibs() { return \"$out/share/fex-emu/GuestThunks/\"; }"
+    substituteInPlace Source/Tools/LinuxEmulation/Thunks.cpp \
+      --replace-fail "FEX_CONFIG_OPT(ThunkHostLibsPath, THUNKHOSTLIBS);" "fextl::string ThunkHostLibsPath() { return \"$out/lib/fex-emu/HostThunks/\"; }"
+    substituteInPlace Source/Tools/FEXConfig/main.qml \
+      --replace-fail "config: \"Thunk" "config: \"UnusedThunk" \
+      --replace-fail "title: qsTr(\"Library forwarding:\")" "visible: false; title: qsTr(\"Library forwarding:\")"
+  '';
+
   nativeBuildInputs = [
     cmake
     ninja
@@ -69,7 +175,12 @@ llvmPackages.stdenv.mkDerivation (finalAttrs: {
   buildInputs = [
     xxHash
     fmt
+    pkgsCross64.buildPackages.clang
+    pkgsCross32.buildPackages.clang
+    libclang
+    libllvm
   ]
+  ++ libForwardingInputs
   ++ (with qt5; [
     qtbase
     qtdeclarative
@@ -83,6 +194,10 @@ llvmPackages.stdenv.mkDerivation (finalAttrs: {
     (lib.cmakeBool "ENABLE_ASSERTIONS" false)
     (lib.cmakeFeature "OVERRIDE_VERSION" finalAttrs.version)
     (lib.cmakeBool "BUILD_TESTS" finalAttrs.finalPackage.doCheck)
+    (lib.cmakeBool "BUILD_THUNKS" true)
+    (lib.cmakeFeature "X86_32_TOOLCHAIN_FILE" "${toolchain32}")
+    (lib.cmakeFeature "X86_64_TOOLCHAIN_FILE" "${toolchain}")
+    (lib.cmakeFeature "X86_DEV_ROOTFS" "${devRootFS}")
   ];
 
   strictDeps = true;