diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
deleted file mode 100644
index a58944e73..000000000
--- a/.github/workflows/lint.yml
+++ /dev/null
@@ -1,74 +0,0 @@
-name: Code linting
-on:
-  pull_request:
-    types:
-      - opened
-      - synchronize
-      - reopened
-      - ready_for_review
-      - labeled
-env:
-  USER: runner
-
-# Cancel the current workflow when new commit pushed
-concurrency:
-  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
-  cancel-in-progress: true
-
-jobs:
-  checkfmt:
-    name: "Check formats"
-    strategy:
-      fail-fast: false
-    runs-on: [self-hosted, linux, nixos]
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-          ref: ${{ github.head_ref }}
-      - name: "Run testcases"
-        run: |
-          RET=0
-          warnOnFileChanged() {
-            if ! git diff -q --exit-code; then
-              RET=1
-              local msg="$1"; shift
-              echo "$msg"
-              echo "$msg" >> $GITHUB_STEP_SUMMARY
-              git reset --hard
-            fi
-          }
-
-          nix develop '.#t1.elaborator' -c mill -i configgen.reformat
-          nix develop '.#t1.elaborator' -c mill -i elaborator.reformat
-          nix develop '.#t1.elaborator' -c mill -i omreader.reformat
-          nix develop '.#t1.elaborator' -c mill -i omreaderlib.reformat
-          nix develop '.#t1.elaborator' -c mill -i rocketv.reformat
-          nix develop '.#t1.elaborator' -c mill -i rocketemu.reformat
-          nix develop '.#t1.elaborator' -c mill -i t1.reformat
-          nix develop '.#t1.elaborator' -c mill -i t1emu.reformat
-          nix develop '.#t1.elaborator' -c mill -i t1rocket.reformat
-          nix develop '.#t1.elaborator' -c mill -i t1rocketemu.reformat
-          warnOnFileChanged "* Scala format fail, please run 'nix develop '.#t1.elaborator' -c mill -i _.reformat'"
-
-          nix fmt
-          warnOnFileChanged "* Nix format fail, please run 'nix fmt'"
-
-          pushd difftest
-          nix shell '.#cargo' '.#rustfmt' -c cargo fmt
-          warnOnFileChanged "* Cargo format fail, please run 'cd difftest; cargo -- format'"
-          popd
-
-          # Disable for now
-          # if nix run '.#ripgrep' -- '\p{Script=Han}' t1 > zh-hans.txt; then
-          #   RET=1
-          #   msg="* Found ZH_CN comments"
-          #   echo "$msg"
-          #   echo "$msg" >> $GITHUB_STEP_SUMMARY
-          #   echo '```text' >> $GITHUB_STEP_SUMMARY
-          #   cat zh-hans.txt >> $GITHUB_STEP_SUMMARY
-          #   echo '```' >> $GITHUB_STEP_SUMMARY
-          #   git reset --hard
-          # fi
-
-          exit $RET
diff --git a/build.sc b/build.sc
index c57817d0f..42332b5c5 100644
--- a/build.sc
+++ b/build.sc
@@ -16,6 +16,9 @@ import $file.dependencies.`berkeley-hardfloat`.common
 import $file.dependencies.rvdecoderdb.common
 import $file.common
 
+// Required for scalafmt to recognize which file to format
+def buildSources = T.sources(os.pwd / "build.sc")
+
 object v {
   val scala    = "2.13.14"
   val mainargs = ivy"com.lihaoyi::mainargs:0.5.0"
@@ -150,7 +153,7 @@ trait T1Emulator extends millbuild.common.T1EmulatorModule with ScalafmtModule {
   def chiselIvy       = None
 }
 
-object rocketemu     extends RocketEmulator
+object rocketemu extends RocketEmulator
 
 trait RocketEmulator extends millbuild.common.RocketEmulatorModule with ScalafmtModule {
   def scalaVersion = T(v.scala)
diff --git a/difftest/default.nix b/difftest/default.nix
index acdff20d2..38a672186 100644
--- a/difftest/default.nix
+++ b/difftest/default.nix
@@ -1,5 +1,6 @@
 { lib
 , rustPlatform
+, rustfmt
 , libspike
 , libspike_interfaces
 , rtlDesignMetadata
@@ -31,9 +32,21 @@ rustPlatform.buildRustPackage {
       ./dpi_t1rocket
       ./Cargo.lock
       ./Cargo.toml
+      ./.rustfmt.toml
     ];
   };
 
+  nativeBuildInputs = [
+    rustfmt
+  ];
+
+  postConfigure = ''
+    if ! cargo fmt --check; then
+      echo "Please run 'cd difftest && cargo fmt' before building emulator!" >&2
+      exit 1
+    fi
+  '';
+
   buildFeatures = [ ] ++ lib.optionals (lib.hasPrefix "dpi" moduleType) [ "dpi_common/${emuType}" ] ++ lib.optionals enableTrace [ "dpi_common/trace" ];
   buildAndTestSubdir = "./${moduleType}";
 
diff --git a/nix/pkgs/mill-builder.nix b/nix/pkgs/mill-builder.nix
index 8b5f3efbc..c74b6379d 100644
--- a/nix/pkgs/mill-builder.nix
+++ b/nix/pkgs/mill-builder.nix
@@ -23,6 +23,14 @@ let
 
       mill -i __.prepareOffline
       mill -i __.scalaCompilerClasspath
+
+      # mill doesn't put scalafmt version into module ivy deps.
+      # It downloads scalafmt only when checkFormat/reformat is explicitly trigger.
+      # And we don't want to wait too long for a dependencies task, so here is the solution:
+      # "checkFormat" the "build.sc" file so that mill will download scalafmt for us,
+      # and we don't need to wait too long for formatting.
+      mill -i mill.scalalib.scalafmt.ScalafmtModule/checkFormatAll buildSources
+
       runHook postBuild
     '';
 
diff --git a/nix/t1/mill-modules.nix b/nix/t1/mill-modules.nix
index c451ce860..5575d2e25 100644
--- a/nix/t1/mill-modules.nix
+++ b/nix/t1/mill-modules.nix
@@ -33,6 +33,7 @@ let
         ./../../t1rocket/src
         ./../../t1rocketemu/src
         ./../../rocketemu/src
+        ./../../.scalafmt.conf
       ];
     };
 
@@ -43,9 +44,10 @@ let
         fileset = unions [
           ./../../build.sc
           ./../../common.sc
+          ./../../.scalafmt.conf
         ];
       };
-      millDepsHash = "sha256-ZK3m6VKG3PChoj6U2b6bVd+Z2/xkZrPxqaLRVvj7QgQ=";
+      millDepsHash = "sha256-gBxEO6pGD0A1RxZW2isjPcHDf+b9Sr++7eq6Ezngiio=";
       nativeBuildInputs = [ dependencies.setupHook ];
     };
 
@@ -80,11 +82,42 @@ let
 
     outputs = [ "out" "configgen" "elaborator" "t1package" ];
 
+    # Check code format before starting build, so that we can enforce all developer run reformat before build.
+    configurePhase = ''
+      runHook preConfigure
+
+      _targetsToCheck=(
+        "configgen"
+        "elaborator"
+        "omreader"
+        "omreaderlib"
+        "rocketemu"
+        "rocketv"
+        "t1"
+        "t1emu"
+        "t1rocket"
+        "t1rocketemu"
+      )
+      for _t in ''${_targetsToCheck[@]}; do
+        if ! mill -i "$_t".checkFormat; then
+          echo "[ERROR] Please run 'mill -i $_t.reformat' before elaborate!" >&2
+          exit 1
+        fi
+      done
+      unset _targetsToCheck
+
+      runHook postConfigure
+    '';
+
     buildPhase = ''
+      runHook preBuild
+
       mill -i '__.assembly'
 
       mill -i t1package.sourceJar
       mill -i t1package.chiselPluginJar
+
+      runHook postBuild
     '';
 
     installPhase = ''