diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5638fdb46..392591456 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,6 +6,12 @@ on:
   workflow_call:
   pull_request:
 
+# A new push to a PR makes the previous run for it obsolete, so cancel it.
+# Pushes to develop and master still run to completion.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -28,13 +34,19 @@ jobs:
           node-version-file: '.nvmrc'
           cache: 'npm'
 
+      # Composer on the runner uses ~/.cache/composer, not ~/.composer/cache,
+      # so ask it for the directory instead of hard-coding one.
+      - name: Get Composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
+
       - name: Cache Composer
         uses: actions/cache@v4
         with:
-          path: ~/.composer/cache
-          key: ${{ runner.os }}-composer-${{ matrix.php }}-${{ hashFiles('**/composer.lock') }}
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ matrix.php-version }}-${{ hashFiles('**/composer.lock') }}
           restore-keys: |
-            ${{ runner.os }}-composer-${{ matrix.php }}-
+            ${{ runner.os }}-composer-${{ matrix.php-version }}-
 
       - name: Install dependencies
         run: npm ci
@@ -57,10 +69,14 @@ jobs:
         with:
           php-version: '8.5'
 
+      - name: Get Composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
+
       - name: Cache Composer
         uses: actions/cache@v4
         with:
-          path: ~/.composer/cache
+          path: ${{ steps.composer-cache.outputs.dir }}
           key: ${{ runner.os }}-composer-phpstan-${{ hashFiles('**/composer.lock') }}
           restore-keys: |
             ${{ runner.os }}-composer-phpstan-
@@ -98,10 +114,14 @@ jobs:
           node-version-file: '.nvmrc'
           cache: 'npm'
 
+      - name: Get Composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
+
       - name: Cache Composer
         uses: actions/cache@v4
         with:
-          path: ~/.composer/cache
+          path: ${{ steps.composer-cache.outputs.dir }}
           key: ${{ runner.os }}-composer-unit-${{ hashFiles('**/composer.lock') }}
           restore-keys: |
             ${{ runner.os }}-composer-unit-
@@ -163,10 +183,14 @@ jobs:
           node-version-file: '.nvmrc'
           cache: 'npm'
 
+      - name: Get Composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
+
       - name: Cache Composer
         uses: actions/cache@v4
         with:
-          path: ~/.composer/cache
+          path: ${{ steps.composer-cache.outputs.dir }}
           key: ${{ runner.os }}-composer-e2e-${{ hashFiles('**/composer.lock') }}
           restore-keys: |
             ${{ runner.os }}-composer-e2e-
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index b53454d9d..6bc6255da 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -32,6 +32,7 @@
 	<arg name="colors" />
 	<arg value="s" /><!-- Show sniff codes in all reports. -->
 	<arg name="severity" value="3" /><!-- Match WPVIP requirements. -->
+	<arg name="parallel" value="8" /><!-- Scan files in parallel processes; ignored when pcntl is missing. -->
 
 	<!-- Includes WordPress-Core, WordPress-Docs and WordPress-Extra rulesets. -->
 	<rule ref="WordPress" />