diff --git a/.github/workflows/haskell-ci.yml b/.github/workflows/haskell-ci.yml
index 9281916..54d81be 100644
--- a/.github/workflows/haskell-ci.yml
+++ b/.github/workflows/haskell-ci.yml
@@ -27,7 +27,7 @@ jobs:
     timeout-minutes:
       60
     container:
-      image: buildpack-deps:focal
+      image: buildpack-deps:jammy
     continue-on-error: ${{ matrix.allow-failure }}
     strategy:
       matrix:
diff --git a/.github/workflows/stack.yml b/.github/workflows/stack.yml
index c225a68..bb2b0f8 100644
--- a/.github/workflows/stack.yml
+++ b/.github/workflows/stack.yml
@@ -78,12 +78,12 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        ghc-ver: ['9.10', '9.8', '9.6', '9.4', '9.2.8', '9.0.2', '8.10.7', '8.8.4', '8.6.5', '8.4.4']
+        ghc-ver: ['9.12', '9.10', '9.8', '9.6', '9.4', '9.2.8', '9.0.2', '8.10.7', '8.8.4', '8.6.5', '8.4.4']
         include:
           - os: windows-latest
-            ghc-ver: '9.10'
+            ghc-ver: '9.12'
           - os: macos-latest
-            ghc-ver: '9.10'
+            ghc-ver: '9.12'
       fail-fast: false
 
     env:
@@ -153,7 +153,7 @@ jobs:
     #   # Conditional to ensure this deployment is only run once per action.
     #   if: >-
     #     startsWith(github.ref, 'refs/tags/v')
-    #     && matrix.ghc-ver == '9.10'
+    #     && matrix.ghc-ver == '9.12'
     #   run: |
     #     DIST_TGZ=$(cabal sdist | tail -1)
     #     echo "DIST_TGZ=${DIST_TGZ}" >> "${GITHUB_ENV}"
@@ -161,7 +161,7 @@ jobs:
     # - name: Source tarball release
     #   if: >-
     #     startsWith(github.ref, 'refs/tags/v')
-    #     && matrix.ghc-ver == '9.10'
+    #     && matrix.ghc-ver == '9.12'
     #   # uses: softprops/action-gh-release@v1
     #   # with:
     #   #   draft: true
@@ -182,7 +182,7 @@ jobs:
       if: >-
         startsWith(github.ref, 'refs/tags/v')
         && runner.os == 'Linux'
-        && matrix.ghc-ver == '9.10'
+        && matrix.ghc-ver == '9.12'
       run: |
         FIXW_BIN=fix-whitespace-${FIXW_VERSION}-linux.binary
         cp -p "${FIXW_EXE}" "${FIXW_BIN}"
@@ -193,7 +193,7 @@ jobs:
     #   if: >-
     #     startsWith(github.ref, 'refs/tags/v')
     #     && runner.os == 'Linux'
-    #     && matrix.ghc-ver == '9.10'
+    #     && matrix.ghc-ver == '9.12'
     #   # uses: softprops/action-gh-release@v1
     #   # with:
     #   #   draft: true
@@ -274,7 +274,7 @@ jobs:
     # - name: Upload binary
     #   if: >-
     #     startsWith(github.ref, 'refs/tags/v')
-    #     && (matrix.ghc-ver == '9.10' || runner.os != 'Linux')
+    #     && (matrix.ghc-ver == '9.12' || runner.os != 'Linux')
     #   uses: actions/upload-release-asset@v1
     #   env:
     #     GITHUB_TOKEN: ${{ github.token }}
@@ -287,7 +287,7 @@ jobs:
     - name: Upload binary
       if: >-
         startsWith(github.ref, 'refs/tags/v')
-        && (matrix.ghc-ver == '9.10' || runner.os != 'Linux')
+        && (matrix.ghc-ver == '9.12' || runner.os != 'Linux')
       env:
         GITHUB_TOKEN: ${{ github.token }}
       run: |
diff --git a/.gitignore b/.gitignore
index cae34b1..ea9f8ad 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+*~
 *.lock
 *.log
 *.rej
@@ -5,6 +6,6 @@
 /.stack-work/
 /dist-newstyle/
 /dist/
-cabal.project.local
+cabal.project.*
 stack*.yaml.lock
 stack.yaml
diff --git a/cabal.haskell-ci b/cabal.haskell-ci
index 1fc9551..e1f1b77 100644
--- a/cabal.haskell-ci
+++ b/cabal.haskell-ci
@@ -1,2 +1 @@
 branches: master
-distribution: focal
diff --git a/fix-whitespace.cabal b/fix-whitespace.cabal
index 07dc7eb..1a6a00d 100644
--- a/fix-whitespace.cabal
+++ b/fix-whitespace.cabal
@@ -35,6 +35,7 @@ extra-doc-files:
   README.md
   fix-whitespace.yaml
   -- stack-supported GHCs
+  stack-9.12.yaml
   stack-9.10.yaml
   stack-9.8.yaml
   stack-9.6.yaml
diff --git a/stack-9.10.yaml b/stack-9.10.yaml
index ab08416..656f670 100644
--- a/stack-9.10.yaml
+++ b/stack-9.10.yaml
@@ -1,3 +1 @@
-resolver: nightly-2025-05-09
-compiler: ghc-9.10.2
-compiler-check: match-exact
+resolver: lts-24.1
diff --git a/stack-9.12.yaml b/stack-9.12.yaml
new file mode 100644
index 0000000..3295f7d
--- /dev/null
+++ b/stack-9.12.yaml
@@ -0,0 +1 @@
+resolver: nightly-2025-07-23
diff --git a/stack-9.8.yaml b/stack-9.8.yaml
index 7cfe486..3e02f37 100644
--- a/stack-9.8.yaml
+++ b/stack-9.8.yaml
@@ -1 +1 @@
-resolver: lts-23.21
+resolver: lts-23.27