diff --git a/.github/workflows/build-linux.yml b/.github/workflows/build-linux.yml
index 2fb47502..5d6dbdb1 100644
--- a/.github/workflows/build-linux.yml
+++ b/.github/workflows/build-linux.yml
@@ -34,6 +34,9 @@ jobs:
     env:
       VCPKG_DEFAULT_TRIPLET: x64-linux
       VERSION_SUFFIX: ${{ matrix.version_suffix }}
+      # Re-use compiled vcpkg packages between runs; otherwise every run
+      # rebuilds ICU from source (measured: 4m11s on Linux, 10m04s on Windows).
+      VCPKG_BINARY_SOURCES: "clear;files,${{ github.workspace }}/vcpkg-bincache,readwrite"
 
     steps:
       - name: Checkout Repository
@@ -97,6 +100,29 @@ jobs:
         shell: bash
         working-directory: vcpkg
 
+      # The submodule commit pins the ports, so it decides what the built
+      # packages are; vcpkg.json decides which ones. Key on both. vcpkg checks
+      # each package's ABI hash itself, so a partial restore-keys hit is safe:
+      # anything that does not match is simply rebuilt.
+      - name: Resolve vcpkg commit for cache key
+        id: vcpkgkey
+        shell: bash
+        run: echo "sha=$(git -C vcpkg rev-parse HEAD)" >> "$GITHUB_OUTPUT"
+
+      - name: Cache vcpkg binary packages
+        uses: actions/cache@v4
+        with:
+          path: ${{ github.workspace }}/vcpkg-bincache
+          key: vcpkg-${{ runner.os }}-${{ matrix.id }}-${{ steps.vcpkgkey.outputs.sha }}-${{ hashFiles('vcpkg.json') }}
+          restore-keys: |
+            vcpkg-${{ runner.os }}-${{ matrix.id }}-${{ steps.vcpkgkey.outputs.sha }}-
+            vcpkg-${{ runner.os }}-${{ matrix.id }}-
+
+      # vcpkg errors out if the binary-cache directory does not exist yet.
+      - name: Create vcpkg binary cache dir
+        shell: bash
+        run: mkdir -p "${{ github.workspace }}/vcpkg-bincache"
+
       - name: Install 3rd Party (Non-20.04)
         if: matrix.id != 'docker-ubuntu-20.04'
         # Same latent mismatch as the Windows job: use the vcpkg the
diff --git a/.github/workflows/build-macos.yml b/.github/workflows/build-macos.yml
index 2f543723..2365d2ba 100644
--- a/.github/workflows/build-macos.yml
+++ b/.github/workflows/build-macos.yml
@@ -14,6 +14,9 @@ jobs:
     name: Build NLP-ENGINE
     runs-on: macOS-latest
     env:
+      # Re-use compiled vcpkg packages between runs; otherwise every run
+      # rebuilds ICU from source (measured: 4m11s on Linux, 10m04s on Windows).
+      VCPKG_BINARY_SOURCES: "clear;files,${{ github.workspace }}/vcpkg-bincache,readwrite"
       VCPKG_DEFAULT_TRIPLET: arm64-osx
 
     steps:
@@ -36,6 +39,29 @@ jobs:
       - name: Install Brew
         run: brew install automake
 
+      # The submodule commit pins the ports, so it decides what the built
+      # packages are; vcpkg.json decides which ones. Key on both. vcpkg checks
+      # each package's ABI hash itself, so a partial restore-keys hit is safe:
+      # anything that does not match is simply rebuilt.
+      - name: Resolve vcpkg commit for cache key
+        id: vcpkgkey
+        shell: bash
+        run: echo "sha=$(git -C vcpkg rev-parse HEAD)" >> "$GITHUB_OUTPUT"
+
+      - name: Cache vcpkg binary packages
+        uses: actions/cache@v4
+        with:
+          path: ${{ github.workspace }}/vcpkg-bincache
+          key: vcpkg-${{ runner.os }}-${{ runner.arch }}-${{ steps.vcpkgkey.outputs.sha }}-${{ hashFiles('vcpkg.json') }}
+          restore-keys: |
+            vcpkg-${{ runner.os }}-${{ runner.arch }}-${{ steps.vcpkgkey.outputs.sha }}-
+            vcpkg-${{ runner.os }}-${{ runner.arch }}-
+
+      # vcpkg errors out if the binary-cache directory does not exist yet.
+      - name: Create vcpkg binary cache dir
+        shell: bash
+        run: mkdir -p "${{ github.workspace }}/vcpkg-bincache"
+
       - name: Install 3rd Party
         run: ./vcpkg install
         working-directory: vcpkg
diff --git a/.github/workflows/build-windows.yml b/.github/workflows/build-windows.yml
index c59129af..17f21326 100644
--- a/.github/workflows/build-windows.yml
+++ b/.github/workflows/build-windows.yml
@@ -24,6 +24,11 @@ jobs:
       # that root with this repo. (Not the bug fixed below -- the steps were
       # running C:\vcpkg's SCRIPTS, not merely honoring its root.)
       VCPKG_ROOT: ${{ github.workspace }}/vcpkg
+      # Re-use compiled vcpkg packages between runs. Without this, every run
+      # rebuilds ICU from source: measured at 10m04s of a 15m43s job, which was
+      # about two thirds of CI. "clear;" drops the default sources so only our
+      # cache dir is consulted.
+      VCPKG_BINARY_SOURCES: "clear;files,${{ github.workspace }}/vcpkg-bincache,readwrite"
 
     steps:
       - uses: actions/checkout@v4
@@ -44,6 +49,29 @@ jobs:
         run: .\bootstrap-vcpkg.bat
         working-directory: vcpkg
 
+      # The submodule commit pins the ports, so it decides what the built
+      # packages are; vcpkg.json decides which ones. Key on both. vcpkg checks
+      # each package's ABI hash itself, so a partial restore-keys hit is safe:
+      # anything that does not match is simply rebuilt.
+      - name: Resolve vcpkg commit for cache key
+        id: vcpkgkey
+        shell: bash
+        run: echo "sha=$(git -C vcpkg rev-parse HEAD)" >> "$GITHUB_OUTPUT"
+
+      - name: Cache vcpkg binary packages
+        uses: actions/cache@v4
+        with:
+          path: ${{ github.workspace }}/vcpkg-bincache
+          key: vcpkg-${{ runner.os }}-${{ runner.arch }}-${{ steps.vcpkgkey.outputs.sha }}-${{ hashFiles('vcpkg.json') }}
+          restore-keys: |
+            vcpkg-${{ runner.os }}-${{ runner.arch }}-${{ steps.vcpkgkey.outputs.sha }}-
+            vcpkg-${{ runner.os }}-${{ runner.arch }}-
+
+      # vcpkg errors out if the binary-cache directory does not exist yet.
+      - name: Create vcpkg binary cache dir
+        shell: bash
+        run: mkdir -p "${{ github.workspace }}/vcpkg-bincache"
+
       - name: Install 3rd Party
         # Invoke the vcpkg the step above just bootstrapped, NOT whatever
         # "vcpkg" resolves to on PATH. The windows-latest runner ships a
@@ -57,10 +85,6 @@ jobs:
         run: .\vcpkg.exe install
         working-directory: vcpkg
 
-      - name: List $RUNNER_WORKSPACE before build
-        shell: pwsh
-        run: Get-ChildItem -Path $env:RUNNER_WORKSPACE -Recurse -Force | Select-Object FullName
-
       - name: Make build directory
         run: mkdir build
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 39f02719..35b86f96 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -23,6 +23,13 @@ find_library(DL_LIBRARY dl)  # Ensure dl library is found
 set(CMAKE_GENERATOR_PLATFORM Win32 HINT)
 
 if(MSVC)
+    # Compile the sources within each target in parallel. `cmake --build
+    # --parallel N` with the Visual Studio generator becomes msbuild /m:N,
+    # which parallelises PROJECTS -- so lite's 101 sources (Arun.cpp alone is
+    # ~14k lines) compiled one after another no matter what --parallel said.
+    # Measured on a clean Win32 Release build with --parallel 4:
+    # 189s without, 49s with /MP4 (modelling a 4-core CI runner).
+    add_compile_options(/MP)
     add_compile_options(/w44005 /w44244 /w44311 /w44211 /w44302 /w44267 /w44312 /w45033 /w44624 /w44996 /w44273)
     add_definitions(-D_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING)
     add_definitions(-DCMAKE_WINDOWS_EXPORT_ALL_SYMBOLS)