diff --git a/difftest/online_vcs/Cargo.toml b/difftest/online_vcs/Cargo.toml
index 7ddddbd49..d85b2b690 100644
--- a/difftest/online_vcs/Cargo.toml
+++ b/difftest/online_vcs/Cargo.toml
@@ -5,6 +5,7 @@ version.workspace = true
 
 [lib]
 crate-type = ["staticlib"]
+name = "dpi"
 
 [dependencies]
 online_dpi = { path = "../online_dpi", features = ["svvpi"] }
diff --git a/difftest/online_vcs/default.nix b/difftest/online_vcs/default.nix
index 657bad854..b6ff3fe19 100644
--- a/difftest/online_vcs/default.nix
+++ b/difftest/online_vcs/default.nix
@@ -2,8 +2,8 @@
 , rustPlatform
 , libspike
 , spike_interfaces
-, vcStaticInstallPath
 , enable-trace ? false
+, vcStaticHome
 }:
 
 rustPlatform.buildRustPackage {
@@ -26,7 +26,7 @@ rustPlatform.buildRustPackage {
   buildAndTestSubdir = "./online_vcs";
 
   env = {
-    VCS_LIB_DIR = "${vcStaticInstallPath}/vcs-mx/linux64/lib";
+    VCS_LIB_DIR = "${vcStaticHome}/vcs-mx/linux64/lib";
     SPIKE_LIB_DIR = "${libspike}/lib";
     SPIKE_INTERFACES_LIB_DIR = "${spike_interfaces}/lib";
   };
diff --git a/nix/overlay.nix b/nix/overlay.nix
index 80d247fbc..6f20d868a 100644
--- a/nix/overlay.nix
+++ b/nix/overlay.nix
@@ -25,10 +25,9 @@ rec {
   rvv-codegen = final.callPackage ./pkgs/rvv-codegen.nix { };
   add-determinism = final.callPackage ./pkgs/add-determinism { }; # faster strip-undetereminism
   # Using VCS need to set VC_STATIC_HOME and SNPSLMD_LICENSE_FILE to impure env, and add sandbox dir to VC_STATIC_HOME
-  vcs-fhs-env = final.callPackage ./pkgs/vcs-fhs-env.nix {
-    vcStaticInstallPath = builtins.getEnv "VC_STATIC_HOME";
-    snpsLicenseFile = builtins.getEnv "SNPSLMD_LICENSE_FILE";
-  };
+  vcStaticHome = builtins.getEnv "VC_STATIC_HOME";
+  snpslmdLicenseFile = builtins.getEnv "SNPSLMD_LICENSE_FILE";
+  vcs-fhs-env = final.callPackage ./pkgs/vcs-fhs-env.nix { };
 
   mill = let jre = final.jdk21; in
     (prev.mill.override { inherit jre; }).overrideAttrs (_: {
diff --git a/nix/pkgs/vcs-fhs-env.nix b/nix/pkgs/vcs-fhs-env.nix
index 37baa934d..0b755983b 100644
--- a/nix/pkgs/vcs-fhs-env.nix
+++ b/nix/pkgs/vcs-fhs-env.nix
@@ -1,31 +1,40 @@
 { buildFHSEnv
-  # e.g. /opt/synopsys/vc_static/V-2023.12
-, vcStaticInstallPath
-  # e.g. port@addr
-, snpsLicenseFile
+, vcStaticHome
+, snpslmdLicenseFile
 }:
 buildFHSEnv {
   name = "vcs-fhs-env";
+
   profile = ''
+    [ ! -d "${vcStaticHome}"  ] && echo "VC HOME not set" && exit 1
+    [ -z "${snpslmdLicenseFile}"  ] && echo "SNPS LICENSE not set" && exit 1
+    export VC_STATIC_HOME=${vcStaticHome}
+
     export TCL_TZ=UTC
-    export VC_STATIC_HOME=${vcStaticInstallPath}
-    export VCS_HOME=${vcStaticInstallPath}/vcs-mx
+    export VC_STATIC_HOME=$VC_STATIC_HOME
+    export VCS_HOME=$VC_STATIC_HOME/vcs-mx
     export VCS_TARGET_ARCH=amd64
     export VCS_ARCH_OVERRIDE=linux
-    export VERDI_HOME=${vcStaticInstallPath}/verdi
-    export NOVAS_HOME=${vcStaticInstallPath}/verdi
-    export SPYGLASS_HOME=${vcStaticInstallPath}/SG_COMPAT/SPYGLASS_HOME
+    export VERDI_HOME=$VC_STATIC_HOME/verdi
+    export NOVAS_HOME=$VC_STATIC_HOME/verdi
+    export SPYGLASS_HOME=$VC_STATIC_HOME/SG_COMPAT/SPYGLASS_HOME
     export SNPS_VERDI_CBUG_LCA=1
-    export SNPSLMD_LICENSE_FILE=${snpsLicenseFile}
+    export SNPSLMD_LICENSE_FILE=${snpslmdLicenseFile}
 
-    export PATH=${vcStaticInstallPath}/bin:$PATH
-    export PATH=${vcStaticInstallPath}/verdi/bin:$PATH
-    export PATH=${vcStaticInstallPath}/vcs-mx/bin:$PATH
-    export PATH=${vcStaticInstallPath}/SG_COMPAT/SPYGLASS_HOME/bin:$PATH
+    export PATH=$VC_STATIC_HOME/bin:$PATH
+    export PATH=$VC_STATIC_HOME/verdi/bin:$PATH
+    export PATH=$VC_STATIC_HOME/vcs-mx/bin:$PATH
+    export PATH=$VC_STATIC_HOME/SG_COMPAT/SPYGLASS_HOME/bin:$PATH
 
     export LD_LIBRARY_PATH=/usr/lib64/
-    export LD_LIBRARY_PATH=${vcStaticInstallPath}/verdi/share/PLI/lib/LINUX64:$LD_LIBRARY_PATH
-    export LD_LIBRARY_PATH=${vcStaticInstallPath}/verdi/share/NPI/lib/LINUX64:$LD_LIBRARY_PATH
+    export LD_LIBRARY_PATH=$VC_STATIC_HOME/verdi/share/PLI/lib/LINUX64:$LD_LIBRARY_PATH
+    export LD_LIBRARY_PATH=$VC_STATIC_HOME/verdi/share/NPI/lib/LINUX64:$LD_LIBRARY_PATH
+
+    export _oldVcsEnvPath="$PATH"
+    preHook() {
+      PATH="$PATH:$_oldVcsEnvPath"
+    }
+    export -f preHook
   '';
   targetPkgs = (ps: with ps; [
     libGL
diff --git a/nix/t1/default.nix b/nix/t1/default.nix
index 421131c8f..b4a924b8f 100644
--- a/nix/t1/default.nix
+++ b/nix/t1/default.nix
@@ -115,10 +115,10 @@ lib.makeScope newScope
               "--strip-debug-info"
             ];
           };
-          vcs-emu-compiled = innerSelf.callPackage ./vcs.nix { rtl = vcs-emu-rtl; };
-          vcs-emu-compiled-trace = innerSelf.callPackage ./vcs.nix { rtl = vcs-emu-rtl; enable-trace = true; };
-          vcs-dpi-lib = innerSelf.callPackage ../../difftest/online_vcs { vcStaticInstallPath = builtins.getEnv "VC_STATIC_HOME"; };
+          vcs-dpi-lib = innerSelf.callPackage ../../difftest/online_vcs { };
           vcs-dpi-lib-trace = vcs-dpi-lib.override { enable-trace = true; };
+          vcs-emu-compiled = innerSelf.callPackage ./vcs.nix { inherit vcs-dpi-lib; rtl = vcs-emu-rtl; };
+          vcs-emu-compiled-trace = innerSelf.callPackage ./vcs.nix { vcs-dpi-lib = vcs-dpi-lib-trace; rtl = vcs-emu-rtl; };
         };
 
         subsystem = rec {
diff --git a/nix/t1/vcs.nix b/nix/t1/vcs.nix
index 82de5d283..fd7a84348 100644
--- a/nix/t1/vcs.nix
+++ b/nix/t1/vcs.nix
@@ -3,10 +3,10 @@
 , configName
 , makeWrapper
 , rtl
-, dpi-lib
+, vcs-dpi-lib
 , vcs-fhs-env
-, enable-trace ? false
 }:
+
 stdenv.mkDerivation {
   name = "${configName}-vcs";
 
@@ -16,7 +16,6 @@ stdenv.mkDerivation {
   src = rtl;
 
   nativeBuildInputs = [
-    vcs-fhs-env
     makeWrapper
   ];
 
@@ -24,34 +23,44 @@ stdenv.mkDerivation {
     runHook preBuild
 
     echo "[nix] running VCS"
-    ${vcs-fhs-env}/bin/vcs-fhs-env vcs \
+    fhsBash=${vcs-fhs-env}/bin/vcs-fhs-env
+    VERDI_HOME=$("$fhsBash" -c "printenv VERDI_HOME")
+    "$fhsBash" vcs \
       -sverilog \
       -full64 \
       -timescale=1ns/1ps \
-      ${lib.optionalString enable-trace ''
+      ${lib.optionalString vcs-dpi-lib.enable-trace ''
         --trace-fst \
         -P $VERDI_HOME/share/PLI/VCS/LINUX64/novas.tab $VERDI_HOME/share/PLI/VCS/LINUX64/pli.a \
         -debug_access+pp+dmptf+thread \
-        -kdb=common_elab,hgldd_all \
-      ''}
+        -kdb=common_elab,hgldd_all''} \
       -file filelist.f \
-      ${dpi-lib}/lib/libdpi.a \
+      ${vcs-dpi-lib}/lib/libdpi.a \
       -o t1-vcs-simulator
+
     runHook postBuild
   '';
 
   passthru = {
-    inherit enable-trace;
+    inherit (vcs-dpi-lib) enable-trace;
   };
 
+  shellHook = ''
+    echo "[nix] entering fhs env"
+    ${vcs-fhs-env}/bin/vcs-fhs-env
+  '';
+
   installPhase = ''
     runHook preInstall
 
-    mkdir -p $out/bin $out/lib $out/share/daidir
+    mkdir -p $out/bin $out/lib
     cp t1-vcs-simulator $out/lib
-    cp -r ./t1-vcs-simulator.daidir/*  $out/share/daidir
+    cp -r t1-vcs-simulator.daidir $out/lib
+
+    makeWrapper "${vcs-fhs-env}/bin/vcs-fhs-env" $out/bin/t1-vcs-simulator \
+      --add-flags "-c $out/bin/t1-vcs-simulator" \
+      --prefix LD_LIBRARY_PATH : $out/lib/t1-vcs-simulator.daidir
 
-    makeWrapper $out/bin/t1-vcs-simulator --add-flags "$out/lib/t1-vcs-simulator -daidir=$out/share/daidir"
     runHook postInstall
   '';
 }