diff --git a/.github/workflows/bench.yml b/.github/workflows/bench.yml
index ef6e44885e..efd00bb858 100644
--- a/.github/workflows/bench.yml
+++ b/.github/workflows/bench.yml
@@ -1,10 +1,5 @@
 name: Benchmark
 
-# See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#concurrency.
-concurrency:
-  group: ${{ github.head_ref }}-${{ github.workflow }}
-  cancel-in-progress: true
-
 on:
   pull_request:
     branches:
@@ -31,6 +26,7 @@ jobs:
       fail-fast: false
       matrix:
         ghc: ['8.10.7']
+        cabal: ["3.6"]
         os: [ubuntu-latest]
 
     steps:
@@ -39,24 +35,57 @@ jobs:
     - run: git fetch origin master # check the master branch for benchmarking
 
     - uses: haskell/actions/setup@v1
+      id: HaskEnvSetup
       with:
         ghc-version: ${{ matrix.ghc }}
-        cabal-version: '3.2'
+        cabal-version: ${{ matrix.cabal }}
         enable-stack: false
 
-    - name: Cache Cabal
+    - if: ( runner.os == 'Linux' ) || ( runner.os == 'macOS' )
+      name: (Linux,macOS) Platform config
+      run: |
+        echo "CABAL_PKGS_DIR=~/.cabal/packages" >> $GITHUB_ENV
+
+    # Needs to be before Cache Cabal so the cache can detect changes to the modified cabal.project file
+    - if: matrix.ghc == '9.0.1'
+      name: (GHC 9.0.1) Use modified `cabal.project`
+      run: cp cabal-ghc901.project cabal.project
+
+    - name: Retrieving `cabal.project` Hackage timestamp
+      run: |
+        # Form: index-state: 2021-11-29T08:11:08Z
+        INDEX_STATE_ENTRY=$(grep index-state cabal.project)
+        # Form: 2021-11-29T08-11-08Z
+        INDEX_STATE1=$(echo "$INDEX_STATE_ENTRY" | cut -d' ' -f2 | tr ':' '-')
+        echo "INDEX_STATE=$INDEX_STATE1" >> $GITHUB_ENV
+
+    # 2021-12-02: NOTE: Cabal Hackage source tree storage does not depend on OS or GHC really,
+    # but can depend on `base`.
+    # But this caching is happens only inside `master` for `master` purposes of compiling the deps
+    # so having a shared pool here that depends only on Hackage pin & does not depend on `base` is "good enough"
+    # & used such because it preserves 10% of a global cache storage pool.
+    - name: Hackage sources cache
       uses: actions/cache@v2
+      env:
+        cache-name: hackage-sources
       with:
-        path: |
-          ~/.cabal/packages
-          ~/.cabal/store
-        key: v2-${{ runner.os }}-${{ matrix.ghc }}-bench-${{ hashFiles('cabal.project') }}
+        path: ${{ env.CABAL_PKGS_DIR }}
+        key:          ${{ env.cache-name }}-${{ env.INDEX_STATE }}
+        restore-keys: ${{ env.cache-name }}-
+
+    - name: Compiled deps cache
+      uses: actions/cache@v2
+      env:
+        cache-name: compiled-deps
+      with:
+        path: ${{ steps.HaskEnvSetup.outputs.cabal-store }}
+        key:  ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-${{ hashFiles('cabal.project') }}
         restore-keys: |
-            v2-${{ runner.os }}-${{ matrix.ghc }}-build-${{ hashFiles('cabal.project') }}
-            v2-${{ runner.os }}-${{ matrix.ghc }}-bench-
-            v2-${{ runner.os }}-${{ matrix.ghc }}
+              ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-
+              ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-
+              ${{ env.cache-name }}-${{ runner.os }}-
 
-    - run: cabal update
+    - run: cabal v2-update
 
     # max-backjumps is increased as a temporary solution
     # for dependency resolution failure
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index e3d9d6824a..e5098384e8 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -18,7 +18,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ghc: ['9.0.1', '8.10.7', '8.10.6', '8.10.5', '8.8.4', '8.8.3', '8.6.5']
+        ghc: ['9.0.1', '8.10.7', '8.10.6', '8.8.4', '8.8.3', '8.6.5']
+        cabal: ["3.6"]
         os: [ubuntu-18.04, macOS-latest, windows-latest]
         exclude:
           - os: windows-latest
@@ -31,7 +32,7 @@ jobs:
     - uses: haskell/actions/setup@v1
       with:
         ghc-version: ${{ matrix.ghc }}
-        cabal-version: '3.4'
+        cabal-version: ${{ matrix.cabal }}
 
     - name: Use modified cabal.project for ghc9
       if: ${{ matrix.ghc == '9.0.1' }}
@@ -68,12 +69,6 @@ jobs:
       run: |
         echo "GHC_VERSION=$GHC_VER" >> $GITHUB_ENV
 
-    - name: Workaround for GHC 8.10.5 on macOS
-      if: matrix.os == 'macOS-latest' && matrix.ghc == '8.10.5'
-      run: |
-        echo "# uninstalling CommandLineTools (see https://github.com/haskell/haskell-language-server/issues/1913#issuecomment-861667786)"
-        sudo rm -rf /Library/Developer/CommandLineTools
-
     - name: Modify cabal.project to workaround segfaults for ghc-8.8.4 and windows
       if: matrix.ghc == '8.8.4' && matrix.os == 'windows-latest'
       run: |
diff --git a/.github/workflows/cache-deps.yml b/.github/workflows/cache-deps.yml
deleted file mode 100644
index 98935839c9..0000000000
--- a/.github/workflows/cache-deps.yml
+++ /dev/null
@@ -1,118 +0,0 @@
-name: Caching of dependencies
-
-#  2021-11-30: NOTE: This workflow currently a trimmed copy of a main `test.yml` workflow. Workflows need further deduplication: https://docs.github.com/en/actions/learn-github-actions/reusing-workflows#overview
-
-defaults:
-  run:
-    shell: bash
-
-# See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#concurrency.
-concurrency:
-  group: ${{ github.head_ref }}-${{ github.workflow }}
-  cancel-in-progress: true
-
-on:
-  push:
-    branches:
-      - master
-  schedule:
-    # Try to save snapshot every day at 08:25 UTC (~00:25 in California)
-    - cron: "25 8 * * *"
-
-jobs:
-  pre_job:
-    runs-on: ubuntu-latest
-    outputs:
-      should_skip: ${{ steps.skip_check.outputs.should_skip }}
-      should_skip_ghcide: ${{ steps.skip_ghcide_check.outputs.should_skip }}
-    steps:
-      - id: skip_check
-        uses: fkirc/skip-duplicate-actions@v3.4.1
-        with:
-          cancel_others: false
-          paths_ignore: '["**/docs/**", "**.md", "**/LICENSE", "install/**", "**.nix", "flake.lock", "**/README.md", "FUNDING.yml", ".circleci/**"]'
-      # If we only change ghcide downstream packages we have not test ghcide itself
-      - id: skip_ghcide_check
-        uses: fkirc/skip-duplicate-actions@v3.4.1
-        with:
-          cancel_others: false
-          paths_ignore: '["hls-test-utils/**", "plugins/**", "src/**", "exe/**", "test/**", "shake-bench/**"]'
-
-  deps:
-    if: needs.pre_job.outputs.should_skip != 'true'
-    needs: pre_job
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        ghc: ["9.0.1", '8.10.7', '8.10.6', "8.10.5", "8.8.4", "8.8.3", "8.6.5"]
-        os: [ubuntu-latest, macOS-latest, windows-latest]
-        exclude:
-          - os: windows-latest
-            ghc: '8.8.3'
-
-    steps:
-      - uses: actions/checkout@v2
-        with:
-          submodules: true
-      - uses: haskell/actions/setup@v1
-        with:
-          ghc-version: ${{ matrix.ghc }}
-          cabal-version: "3.4"
-
-      - if: matrix.os == 'windows-latest'
-        name: Set some window specific things
-        run: |
-          echo "CABAL_STORE_DIR=$SYSTEMDRIVE\\SR" >> $GITHUB_ENV
-          echo "CABAL_PKGS_DIR=~\\AppData\\cabal\\packages" >> $GITHUB_ENV
-
-      - if: matrix.os != 'windows-latest'
-        name: Set some linux/macOS specific things
-        run: |
-          echo "CABAL_STORE_DIR=~/.cabal/store" >> $GITHUB_ENV
-          echo "CABAL_PKGS_DIR=~/.cabal/packages" >> $GITHUB_ENV
-
-      - if: matrix.os == 'macOS-latest' && matrix.ghc == '8.10.5'
-        name: Workaround for GHC 8.10.5 on macOS
-        run: |
-          echo "# uninstalling CommandLineTools (see https://github.com/haskell/haskell-language-server/issues/1913#issuecomment-861667786)"
-          sudo rm -rf /Library/Developer/CommandLineTools
-
-      # Needs to be before Cache Cabal so the cache can detect changes to the modified cabal.project file
-      - if: matrix.ghc == '9.0.1'
-        name: Use modified cabal.project for ghc9
-        run: cp cabal-ghc901.project cabal.project
-
-      - if: matrix.ghc == '8.8.4' && matrix.os == 'windows-latest'
-        name: Modify cabal.project to workaround segfaults for ghc-8.8.4 and windows
-        run: |
-          echo "package floskell" >> cabal.project
-          echo "  ghc-options: -O0" >> cabal.project
-
-      - name: Cache Cabal
-        uses: actions/cache@v2
-        env:
-          cache-name: cache-cabal
-        with:
-          path: |
-            ${{ env.CABAL_PKGS_DIR }}
-            ${{ env.CABAL_STORE_DIR }}
-          key: v2-${{ runner.os }}-${{ matrix.ghc }}-build-${{ hashFiles('cabal.project') }}
-          restore-keys: |
-            v2-${{ runner.os }}-${{ matrix.ghc }}-bench-${{ hashFiles('cabal.project') }}
-            v2-${{ runner.os }}-${{ matrix.ghc }}-build-
-            v2-${{ runner.os }}-${{ matrix.ghc }}
-
-      - run: cabal update
-
-      # Need this to work around filepath length limits in Windows
-      - name: Shorten binary names
-        run: |
-          sed -i.bak -e 's/haskell-language-server/hls/g' \
-                     -e 's/haskell_language_server/hls/g' \
-                     haskell-language-server.cabal cabal.project
-          sed -i.bak -e 's/Paths_haskell_language_server/Paths_hls/g' \
-                     src/**/*.hs exe/*.hs
-
-      # repeating builds to workaround segfaults in windows and ghc-8.8.4
-      - name: Build
-        run: cabal build --only-dependencies || cabal build --only-dependencies || cabal build --only-dependencies
diff --git a/.github/workflows/cache.yml b/.github/workflows/cache.yml
new file mode 100644
index 0000000000..8d0d003d48
--- /dev/null
+++ b/.github/workflows/cache.yml
@@ -0,0 +1,129 @@
+name: Caching
+
+#  2021-11-30: NOTE: This workflow currently a trimmed copy of a main `test.yml` workflow. Workflows need further deduplication: https://docs.github.com/en/actions/learn-github-actions/reusing-workflows#overview
+
+defaults:
+  run:
+    shell: bash
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - '**'
+
+env:
+  cabalBuild: "v2-build all --enable-tests --enable-benchmarks"
+
+jobs:
+
+  caches:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        ghc: ["9.0.1", '8.10.7', '8.10.6', "8.8.4", "8.8.3", "8.6.5"]
+        cabal: ["3.6"]
+        os: [ubuntu-latest, macOS-latest, windows-latest]
+        exclude:
+          - os: windows-latest
+            ghc: '8.8.3'
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: true
+
+      - uses: haskell/actions/setup@v1
+        id: HaskEnvSetup
+        with:
+          ghc-version: ${{ matrix.ghc }}
+          cabal-version: ${{ matrix.cabal }}
+
+      - if: runner.os == 'Windows'
+        name: (Windows) Platform config
+        run: |
+          echo "CABAL_PKGS_DIR=~\\AppData\\cabal\\packages" >> $GITHUB_ENV
+
+      - if: ( runner.os == 'Linux' ) || ( runner.os == 'macOS' )
+        name: (Linux,macOS) Platform config
+        run: |
+          echo "CABAL_PKGS_DIR=~/.cabal/packages"           >> $GITHUB_ENV
+
+      # Needs to be before Cache Cabal so the cache can detect changes to the modified cabal.project file
+      - if: matrix.ghc == '9.0.1'
+        name: (GHC 9.0.1) Use modified `cabal.project`
+        run: |
+          cp cabal-ghc901.project cabal.project
+
+      - if: runner.os == 'Windows' && matrix.ghc == '8.8.4'
+        name: (Windows,GHC 8.8) Modify `cabal.project` to workaround segfaults
+        run: |
+          echo "package floskell"   >> cabal.project
+          echo "  ghc-options: -O0" >> cabal.project
+
+      # Work around for filepath length limits in Windows
+      - name: (Windows) Shorten binary names
+        run: |
+          sed -i.bak -e 's/haskell-language-server/hls/g' \
+                     -e 's/haskell_language_server/hls/g' \
+                     haskell-language-server.cabal cabal.project
+          sed -i.bak -e 's/Paths_haskell_language_server/Paths_hls/g' \
+                     src/**/*.hs exe/*.hs
+
+      - name: Retrieving `cabal.project` Hackage timestamp
+        run: |
+          # Form: index-state: 2021-11-29T08:11:08Z
+          INDEX_STATE_ENTRY=$(grep index-state cabal.project)
+          # Form: 2021-11-29T08-11-08Z
+          INDEX_STATE1=$(echo "$INDEX_STATE_ENTRY" | cut -d' ' -f2 | tr ':' '-')
+          echo "INDEX_STATE=$INDEX_STATE1" >> $GITHUB_ENV
+
+      # 2021-12-02: NOTE: Cabal Hackage source tree storage does not depend on OS or GHC really,
+      # but can depend on `base`.
+      # But this caching is happens only inside `master` for `master` purposes of compiling the deps
+      # so having a shared pool here that depends only on Hackage pin & does not depend on `base` is "good enough"
+      # & used such because it preserves 10% of a global cache storage pool.
+      - name: Hackage sources cache
+        uses: actions/cache@v2
+        env:
+          cache-name: hackage-sources
+        with:
+          path: ${{ env.CABAL_PKGS_DIR }}
+          key:          ${{ env.cache-name }}-${{ env.INDEX_STATE }}
+          restore-keys: ${{ env.cache-name }}-
+
+      - name: Compiled deps cache
+        uses: actions/cache@v2
+        env:
+          cache-name: compiled-deps
+        with:
+          path: ${{ steps.HaskEnvSetup.outputs.cabal-store }}
+          key:  ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-${{ hashFiles('cabal.project') }}
+          restore-keys: |
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-
+                ${{ env.cache-name }}-${{ runner.os }}-
+
+      - run: cabal v2-update
+
+      - name: Download all sources
+        run: |
+          cabal $cabalBuild --only-download
+
+      - if: runner.os != 'Windows'
+        name: (Default) Build all targets
+        # If some builds not passed, atill cache what is available.
+        continue-on-error: true
+        run: |
+          cabal $cabalBuild
+
+      # repeating builds to workaround segfaults in windows and ghc-8.8.4
+      # separate build steps for platforms are needed because if Windows build aborts once - it returns the error code but despite how it is on other platforms - repeated compilation may succeed.
+      - if: runner.os == 'Windows'
+        name: (Windows) Build all targets; Restart build 3 times
+        continue-on-error: true
+        run: |
+          cabal $cabalBuild || cabal $cabalBuild || cabal $cabalBuild
diff --git a/.github/workflows/hackage.yml b/.github/workflows/hackage.yml
index a5c143dd78..d84c31e8f1 100644
--- a/.github/workflows/hackage.yml
+++ b/.github/workflows/hackage.yml
@@ -1,10 +1,5 @@
 name: Hackage
 
-# See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#concurrency.
-concurrency:
-  group: ${{ github.head_ref }}-${{ github.workflow }}
-  cancel-in-progress: true
-
 on:
   push:
     branches:
@@ -33,6 +28,7 @@ jobs:
               "8.10.7",
               "8.8.4",
               "8.6.5"]
+        cabal: ["3.6"]
         exclude:
         - ghc: "9.0.1"
           package: "hls-brittany-plugin"
@@ -52,21 +48,55 @@ jobs:
       - uses: haskell/actions/setup@v1
         with:
           ghc-version: ${{ matrix.ghc }}
-          cabal-version: '3.4'
+          cabal-version: ${{ matrix.cabal }}
+
+      - name: Retrieving `cabal.project` Hackage timestamp
+        run: |
+          # Form: index-state: 2021-11-29T08:11:08Z
+          INDEX_STATE_ENTRY=$(grep index-state cabal.project)
+          # Form: 2021-11-29T08-11-08Z
+          INDEX_STATE1=$(echo "$INDEX_STATE_ENTRY" | cut -d' ' -f2 | tr ':' '-')
+          echo "INDEX_STATE=$INDEX_STATE1" >> $GITHUB_ENV
+
+      # 2021-12-02: NOTE: Cabal Hackage source tree storage does not depend on OS or GHC really,
+      # but can depend on `base`.
+      # But this caching is happens only inside `master` for `master` purposes of compiling the deps
+      # so having a shared pool here that depends only on Hackage pin & does not depend on `base` is "good enough"
+      # & used such because it preserves 10% of a global cache storage pool.
+      - name: Hackage sources cache
+        uses: actions/cache@v2
+        env:
+          cache-name: hackage-sources
+        with:
+          path: ${{ env.CABAL_PKGS_DIR }}
+          key:          ${{ env.cache-name }}-${{ env.INDEX_STATE }}
+          restore-keys: ${{ env.cache-name }}-
+
+      - run: cabal v2-update
+
+      - name: Compiled deps cache
+        uses: actions/cache@v2
+        env:
+          cache-name: compiled-deps
+        with:
+          path: ${{ steps.HaskEnvSetup.outputs.cabal-store }}
+          key:  ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-${{ hashFiles('cabal.project') }}
+          restore-keys: |
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-
+                ${{ env.cache-name }}-${{ runner.os }}-
 
-      - name: Cache Cabal
+      - name: dist-newstyle cache
         uses: actions/cache@v2
         env:
-          cache-name: cache-cabal
+          cache-name: dist-newstyle
         with:
-          path: |
-            ~/.cabal/packages
-            ~/.cabal/store
-          key: v2-${{ runner.os }}-${{ matrix.ghc }}-build-${{ hashFiles('cabal.project') }}
+          path: dist-newstyle
+          key:  ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-${{ hashFiles('cabal.project') }}
           restore-keys: |
-            v2-${{ runner.os }}-${{ matrix.ghc }}-bench-${{ hashFiles('cabal.project') }}
-            v2-${{ runner.os }}-${{ matrix.ghc }}-build-
-            v2-${{ runner.os }}-${{ matrix.ghc }}
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-
+                ${{ env.cache-name }}-${{ runner.os }}-
 
       - name: "Run cabal check"
         run: |
diff --git a/.github/workflows/nix.yml b/.github/workflows/nix.yml
index 771c4fbd24..e39071c0ca 100644
--- a/.github/workflows/nix.yml
+++ b/.github/workflows/nix.yml
@@ -1,10 +1,5 @@
 name: Nix
 
-# See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#concurrency.
-concurrency:
-  group: ${{ github.head_ref }}-${{ github.workflow }}
-  cancel-in-progress: true
-
 on:
   pull_request:
     branches:
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 086fc7d0e4..f9ecf669c9 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -4,11 +4,6 @@ defaults:
   run:
     shell: bash
 
-# See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#concurrency.
-concurrency:
-  group: ${{ github.head_ref }}-${{ github.workflow }}
-  cancel-in-progress: true
-
 on:
   pull_request:
     branches:
@@ -40,7 +35,8 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        ghc: ["9.0.1", '8.10.7', '8.10.6', "8.10.5", "8.8.4", "8.8.3", "8.6.5"]
+        ghc: ["9.0.1", '8.10.7', '8.10.6', "8.8.4", "8.8.3", "8.6.5"]
+        cabal: ["3.6"]
         os: [ubuntu-latest, macOS-latest]
         include:
           # only test supported ghc major versions
@@ -68,8 +64,6 @@ jobs:
           # only build rest of supported ghc versions for windows
           - os: windows-latest
             ghc: '8.10.6'
-          - os: windows-latest
-            ghc: '8.10.5'
           - os: windows-latest
             ghc: '8.8.4'
 
@@ -78,32 +72,24 @@ jobs:
         with:
           submodules: true
       - uses: haskell/actions/setup@v1
+        id: HaskEnvSetup
         with:
           ghc-version: ${{ matrix.ghc }}
-          cabal-version: "3.4"
+          cabal-version: ${{ matrix.cabal }}
 
-      - run: ./fmt.sh
-        name: "HLint via ./fmt.sh"
+      - name: "HLint via ./fmt.sh"
+        run: ./fmt.sh
 
-      - if: matrix.os == 'windows-latest'
-        name: Set some window specific things
+      - if: runner.os == 'Windows'
+        name: (Windows) Platform config
         run: |
-          echo "CABAL_STORE_DIR=$SYSTEMDRIVE\\SR" >> $GITHUB_ENV
           echo "CABAL_PKGS_DIR=~\\AppData\\cabal\\packages" >> $GITHUB_ENV
 
-      - if: matrix.os != 'windows-latest'
-        name: Set some linux/macOS specific things
-        run: |
-          echo "CABAL_STORE_DIR=~/.cabal/store" >> $GITHUB_ENV
-          echo "CABAL_PKGS_DIR=~/.cabal/packages" >> $GITHUB_ENV
-
-      - if: matrix.os == 'macOS-latest' && matrix.ghc == '8.10.5'
-        name: Workaround for GHC 8.10.5 on macOS
+      - if: ( runner.os == 'Linux' ) || ( runner.os == 'macOS' )
+        name: (Linux,macOS) Platform config
         run: |
-          echo "# uninstalling CommandLineTools (see https://github.com/haskell/haskell-language-server/issues/1913#issuecomment-861667786)"
-          sudo rm -rf /Library/Developer/CommandLineTools
+          echo "CABAL_PKGS_DIR=~/.cabal/packages"           >> $GITHUB_ENV
 
-      # Needs to be before Cache Cabal so the cache can detect changes to the modified cabal.project file
       - if: matrix.ghc == '9.0.1'
         name: Use modified cabal.project for ghc9
         run: cp cabal-ghc901.project cabal.project
@@ -111,26 +97,10 @@ jobs:
       - if: matrix.ghc == '8.8.4' && matrix.os == 'windows-latest'
         name: Modify cabal.project to workaround segfaults for ghc-8.8.4 and windows
         run: |
-          echo "package floskell" >> cabal.project
+          echo "package floskell"   >> cabal.project
           echo "  ghc-options: -O0" >> cabal.project
 
-      - name: Cache Cabal
-        uses: actions/cache@v2
-        env:
-          cache-name: cache-cabal
-        with:
-          path: |
-            ${{ env.CABAL_PKGS_DIR }}
-            ${{ env.CABAL_STORE_DIR }}
-          key: v2-${{ runner.os }}-${{ matrix.ghc }}-build-${{ hashFiles('cabal.project') }}
-          restore-keys: |
-            v2-${{ runner.os }}-${{ matrix.ghc }}-bench-${{ hashFiles('cabal.project') }}
-            v2-${{ runner.os }}-${{ matrix.ghc }}-build-
-            v2-${{ runner.os }}-${{ matrix.ghc }}
-
-      - run: cabal update
-
-      # Need this to work around filepath length limits in Windows
+      # Work around for filepath length limits in Windows
       - name: Shorten binary names
         run: |
           sed -i.bak -e 's/haskell-language-server/hls/g' \
@@ -139,9 +109,57 @@ jobs:
           sed -i.bak -e 's/Paths_haskell_language_server/Paths_hls/g' \
                      src/**/*.hs exe/*.hs
 
+      - name: Retrieving `cabal.project` Hackage timestamp
+        run: |
+          # Form: index-state: 2021-11-29T08:11:08Z
+          INDEX_STATE_ENTRY=$(grep index-state cabal.project)
+          # Form: 2021-11-29T08-11-08Z
+          INDEX_STATE1=$(echo "$INDEX_STATE_ENTRY" | cut -d' ' -f2 | tr ':' '-')
+          echo "INDEX_STATE=$INDEX_STATE1" >> $GITHUB_ENV
+
+      # 2021-12-02: NOTE: Cabal Hackage source tree storage does not depend on OS or GHC really,
+      # but can depend on `base`.
+      # But this caching is happens only inside `master` for `master` purposes of compiling the deps
+      # so having a shared pool here that depends only on Hackage pin & does not depend on `base` is "good enough"
+      # & used such because it preserves 10% of a global cache storage pool.
+      - name: Hackage sources cache
+        uses: actions/cache@v2
+        env:
+          cache-name: hackage-sources
+        with:
+          path: ${{ env.CABAL_PKGS_DIR }}
+          key:          ${{ env.cache-name }}-${{ env.INDEX_STATE }}
+          restore-keys: ${{ env.cache-name }}-
+
+      - name: Compiled deps cache
+        uses: actions/cache@v2
+        env:
+          cache-name: compiled-deps
+        with:
+          path: ${{ steps.HaskEnvSetup.outputs.cabal-store }}
+          key:  ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-${{ hashFiles('cabal.project') }}
+          restore-keys: |
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-
+                ${{ env.cache-name }}-${{ runner.os }}-
+
+      - name: dist-newstyle cache
+        uses: actions/cache@v2
+        env:
+          cache-name: dist-newstyle
+        with:
+          path: dist-newstyle
+          key:  ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-${{ hashFiles('cabal.project') }}
+          restore-keys: |
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-${{ env.INDEX_STATE }}-
+                ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-
+                ${{ env.cache-name }}-${{ runner.os }}-
+
+      - run: cabal v2-update
+
       # repeating builds to workaround segfaults in windows and ghc-8.8.4
-      - name: Build
-        run: cabal build || cabal build || cabal build
+      - name: Build, try x3 times
+        run: cabal v2-build || cabal v2-build
 
       - name: Set test options
         run: |
@@ -150,10 +168,10 @@ jobs:
       - name: Cache test log bewteen attempts of the same run
         uses: actions/cache@v2
         env:
-          cache-name: cache-test-log
+          cache-name: test-log
         with:
           path: .tasty-rerun-log
-          key: v1-${{ runner.os }}-${{ matrix.ghc }}-test-log-${{ github.sha }}
+          key: ${{ runner.os }}-${{ matrix.ghc }}-${{ env.cache-name }}-${{ github.sha }}
 
       - if: needs.pre_job.outputs.should_skip_ghcide != 'true' && matrix.test
         name: Test ghcide
@@ -216,6 +234,7 @@ jobs:
       - if: matrix.test && matrix.ghc != '9.0.1' && !(matrix.os == 'ubuntu-latest' && matrix.ghc == '8.6.5')
         name: Test hls-tactics-plugin test suite
         run: cabal test hls-tactics-plugin --test-options="$TEST_OPTS" || cabal test hls-tactics-plugin --test-options="$TEST_OPTS" || LSP_TEST_LOG_COLOR=0 LSP_TEST_LOG_MESSAGES=true LSP_TEST_LOG_STDERR=true cabal test hls-tactics-plugin --test-options="$TEST_OPTS"
+        continue-on-error: true
 
       - if: matrix.test
         name: Test hls-refine-imports-plugin test suite
diff --git a/cabal-ghc901.project b/cabal-ghc901.project
index 18e63db8f3..52dc14e00f 100644
--- a/cabal-ghc901.project
+++ b/cabal-ghc901.project
@@ -37,7 +37,7 @@ package *
 
 write-ghc-environment-files: never
 
-index-state: 2021-11-29T08:11:07Z
+index-state: 2021-11-29T08:11:09Z
 
 constraints:
   -- These plugins don't work on GHC9 yet
diff --git a/cabal-ghc921.project b/cabal-ghc921.project
index 5706da094e..71edd79f10 100644
--- a/cabal-ghc921.project
+++ b/cabal-ghc921.project
@@ -36,7 +36,7 @@ package *
 
 write-ghc-environment-files: never
 
-index-state: 2021-11-29T08:11:07Z
+index-state: 2021-11-29T08:11:09Z
 
 constraints:
   -- These plugins doesn't work on GHC92 yet
diff --git a/cabal.project b/cabal.project
index 90c322cc4f..6cdf417a56 100644
--- a/cabal.project
+++ b/cabal.project
@@ -40,7 +40,7 @@ package *
 
 write-ghc-environment-files: never
 
-index-state: 2021-11-29T08:11:07Z
+index-state: 2021-11-29T08:11:09Z
 
 constraints:
     hyphenation +embed