diff --git a/.github/workflows/auto-reformat.yml b/.github/workflows/auto-reformat.yml
new file mode 100644
index 000000000..e82406621
--- /dev/null
+++ b/.github/workflows/auto-reformat.yml
@@ -0,0 +1,50 @@
+name: reformat
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - ready_for_review
+      - labeled
+
+# Cancel the current workflow when new commit pushed
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  run:
+    name: "Reformat all codes"
+    # Don't run reformat when:
+    #   - user cancel
+    #   - PR from outside repository ( we don't have permission to push commit into fork repository )
+    if: ${{ !cancelled() && github.event.pull_request.head.repo.full_name == github.repository }}
+    runs-on: [self-hosted, linux, nixos]
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          ref: ${{ github.head_ref }}
+      - name: "Reformat all T1 module codes"
+        run: nix develop ".#t1.elaborator.editable" -c mill -i _.reformat
+      - name: "Reformat all Rust codes"
+        run: |
+          cd difftest
+          nix shell ".#cargo" ".#rustfmt" -c cargo fmt
+      - name: "Commit formats"
+        run: |
+          git config user.name github-actions
+          git config user.email github-actions@github.com
+          changed_cases=$(git diff --name-only)
+
+          if [ -n "$changed_cases" ]; then
+            echo -e "Reformat codes: $changed_cases"
+            git add .
+            git commit -m "[chore] reformat all T1 modules"
+            git push origin ${{ github.head_ref }}
+          else
+            echo "No format error detected"
+          fi
diff --git a/.github/workflows/t1rocket.yml b/.github/workflows/t1rocket.yml
index c1fd497b0..43ea8c293 100644
--- a/.github/workflows/t1rocket.yml
+++ b/.github/workflows/t1rocket.yml
@@ -1,12 +1,9 @@
 name: T1RocketEmu VCS Test
 on:
-  pull_request:
+  workflow_run:
+    workflows: [reformat]
     types:
-      - opened
-      - synchronize
-      - reopened
-      - ready_for_review
-      - labeled
+      - completed
 env:
   USER: runner
   EMU_TOP: t1rocketemu
diff --git a/.github/workflows/vcs.yml b/.github/workflows/vcs.yml
index 810638c08..8750e0d6d 100644
--- a/.github/workflows/vcs.yml
+++ b/.github/workflows/vcs.yml
@@ -1,12 +1,10 @@
 name: T1Emu VCS Test
 on:
-  pull_request:
+  workflow_run:
+    workflows: [reformat]
     types:
-      - opened
-      - synchronize
-      - reopened
-      - ready_for_review
-      - labeled
+      - completed
+
 env:
   USER: runner
   EMU_TOP: t1emu
diff --git a/build.sc b/build.sc
index 41227cd03..74e88a77e 100644
--- a/build.sc
+++ b/build.sc
@@ -16,9 +16,6 @@ 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    = "2.13.15"
   val mainargs = ivy"com.lihaoyi::mainargs:0.5.0"
diff --git a/difftest/default.nix b/difftest/default.nix
index dc7f760d0..bd2d56743 100644
--- a/difftest/default.nix
+++ b/difftest/default.nix
@@ -1,6 +1,5 @@
 { lib
 , rustPlatform
-, rustfmt
 , libspike
 , libspike_interfaces
 , rtlDesignMetadata
@@ -36,17 +35,6 @@ rustPlatform.buildRustPackage {
     ];
   };
 
-  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 fbab7ebe1..9de423e44 100644
--- a/nix/pkgs/mill-builder.nix
+++ b/nix/pkgs/mill-builder.nix
@@ -37,16 +37,6 @@ 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.
-      if ! mill -i mill.scalalib.scalafmt.ScalafmtModule/checkFormatAll buildSources; then
-        echo "[ERROR] build.sc is misformatted, please run 'mill -i mill.scalalib.scalafmt.ScalafmtModule/reformatAll buildSources'" >&2
-        exit 1
-      fi
-
       runHook postBuild
     '';
 
diff --git a/nix/t1/mill-modules.nix b/nix/t1/mill-modules.nix
index 85e81f885..03f4cea62 100644
--- a/nix/t1/mill-modules.nix
+++ b/nix/t1/mill-modules.nix
@@ -44,10 +44,9 @@ let
         fileset = unions [
           ./../../build.sc
           ./../../common.sc
-          ./../../.scalafmt.conf
         ];
       };
-      millDepsHash = "sha256-pixG96IxJsYlgIU+DVxGHky6G5nMfHXphEq5A/xLP7Q=";
+      millDepsHash = "sha256-XvGLNLOC7OEwfC7SB5zBdB64VjROBkwgIcHx+9FHmSs=";
       nativeBuildInputs = [ dependencies.setupHook ];
     };
 
@@ -84,32 +83,6 @@ let
 
     outputs = [ "out" "omreader" "elaborator" "t1package" ];
 
-    # Check code format before starting build, so that we can enforce all developer run reformat before build.
-    configurePhase = ''
-      runHook preConfigure
-
-      _targetsToCheck=(
-        "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
 
diff --git a/script/build.sc b/script/build.sc
index 897b9c587..6bda821a4 100644
--- a/script/build.sc
+++ b/script/build.sc
@@ -7,9 +7,6 @@ import mill.scalalib.TestModule.Utest
 import mill.util.Jvm
 import coursier.maven.MavenRepository
 
-// Required for scalafmt to recognize which file to format
-def buildSources = T.sources(os.pwd / "build.sc")
-
 trait ScriptModule extends ScalaModule with ScalafmtModule {
   val scala3   = "3.3.3"
   val mainargs = ivy"com.lihaoyi::mainargs:0.5.0"
diff --git a/script/default.nix b/script/default.nix
index dbd294d4c..0012f44b7 100644
--- a/script/default.nix
+++ b/script/default.nix
@@ -29,10 +29,9 @@ let
             root = ./.;
             fileset = unions [
               ./build.sc
-              ./.scalafmt.conf
             ];
           };
-          millDepsHash = "sha256-y8tAFwctiU6ehghuf7KP73DuWCGCnAAdIXOIPwT+QOo=";
+          millDepsHash = "sha256-QQ5gCbvovC55t9MmfCNTvNFdD6FcNqmLmfhT9qJhQQc=";
         };
 
         passthru.withLsp = self.overrideAttrs (old: {
@@ -66,12 +65,6 @@ let
         buildPhase = ''
           runHook preBuild
 
-          # Not debug build, check source format
-          if (( $enableNativeExe )); then
-            echo "Checking format"
-            mill -i ${moduleName}.checkFormat
-          fi
-
           echo "Building JAR"
           mill -i ${moduleName}.assembly