diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index 5752b36bc2..425bcb96c9 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -1,5 +1,13 @@
 # This is the main maven workflow for SWT.
 
+# You can run this locally to test changes with the act command https://nektosact.com/
+# For example, to run all linux tests on Java 21:
+#   act -j build-linux --matrix java:21 --artifact-server-path $PWD/.artifacts
+# You may need to download runners on first run, act will ask but if you
+# want the big runner there is no progress as it downloads, so you can pull it with
+# docker directly:
+#   docker pull catthehacker/ubuntu:full-latest
+
 name: SWT Matrix Build
 concurrency: 
     group: ${{ github.workflow }}-${{ github.ref }}
@@ -25,19 +33,103 @@ jobs:
       with:
         name: Event File
         path: ${{ github.event_path }}
-  build:
+
+  changes:
+    name: Detect changed paths
+    runs-on: ubuntu-latest
+    outputs:
+      # Lint warnings are expected in this block
+      # https://github.com/dorny/paths-filter/issues/223#issuecomment-2463309889
+      win32: ${{ steps.filter.outputs.win32  || 'false' }}
+      gtk:   ${{ steps.filter.outputs.gtk    || 'false' }}
+      cocoa: ${{ steps.filter.outputs.cocoa  || 'false' }}
+      md:    ${{ steps.filter.outputs.md     || 'false' }}
+      other: ${{ steps.filter.outputs.other  || 'false' }}
+    steps:
+      - uses: actions/checkout@ff7abcd0c3c05ccf6adc123a8cd1fd4fb30fb493 # v5.0.0
+        with:
+          fetch-depth: 0  # so base/ref SHAs are diffable
+      - name: Paths filter (PR/Push only)
+        if: github.event.pull_request.base
+        # dorney/paths-filter is out of date, so use this fork with
+        # a specific fix for missing predicate-quantifier in action's
+        # inputs
+        # https://github.com/dorny/paths-filter/pull/226#issuecomment-2805358761
+        uses: petermetz/paths-filter@5ee2f5d4cf5d7bdd998a314a42da307e2ae1639d
+        id: filter
+        with:
+          predicate-quantifier: 'every'
+          filters: |
+            win32:
+              - '**/win32/**'
+            gtk:
+              - '**/gtk/**'
+            cocoa:
+              - '**/cocoa/**'
+            md:
+              - '**/*.md'
+            jenkins:
+              - 'Jenkinsfile'
+            # "other" = anything not matching the above buckets
+            other:
+              - '**'
+              - '!**/win32/**'
+              - '!**/gtk/**'
+              - '!**/cocoa/**'
+              - '!**/*.md'
+              - '!Jenkinsfile'
+
+  build-linux:
+    name: Build (Linux)
+    needs: changes
+    # push => always; PR => run if gtk changed OR "other" changed (run-everything case)
+    if: ${{ github.event_name != 'pull_request' || needs.changes.outputs.gtk == 'true' || needs.changes.outputs.other == 'true' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        java: ['21']
+    uses: ./.github/workflows/build.yml
+    with:
+      runner: ubuntu-latest
+      java: ${{ matrix.java }}
+      native: gtk.linux.x86_64
+      performance: ${{ contains(github.event.pull_request.labels.*.name, 'performance') }}
+
+  build-windows:
+    name: Build (Windows)
+    needs: changes
+    # push => always; PR => run if win32 changed OR "other" changed (run-everything case)
+    if: ${{ github.event_name != 'pull_request' || needs.changes.outputs.win32 == 'true' || needs.changes.outputs.other == 'true' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        java: ['21']
+    uses: ./.github/workflows/build.yml
+    with:
+      runner: windows-latest
+      java: ${{ matrix.java }}
+      native: win32.win32.x86_64
+      performance: ${{ contains(github.event.pull_request.labels.*.name, 'performance') }}
+
+  build-macos:
+    name: Build (macOS)
+    needs: changes
+    # push => always; PR => run if cocoa changed OR "other" changed (run-everything case)
+    if: ${{ github.event_name != 'pull_request' || needs.changes.outputs.cocoa == 'true' || needs.changes.outputs.other == 'true' }}
     strategy:
       fail-fast: false
       matrix:
-        java: [ '21' ]
-        config: 
-          - { name: Linux, os: ubuntu-latest, native: gtk.linux.x86_64 }
-          - { name: Windows, os: windows-latest, native: win32.win32.x86_64 }
-          - { name: MacOS x86, os: macos-15-intel, native: cocoa.macosx.x86_64 }
-          - { name: MacOS ARM, os: macos-latest, native: cocoa.macosx.aarch64 }
+        java: ['21']
+        native: [cocoa.macosx.x86_64, cocoa.macosx.aarch64]
+        runner: [macos-15-intel, macos-latest]
+        exclude:
+          - runner: macos-latest
+            native: cocoa.macosx.x86_64
+          - runner: macos-15-intel
+            native: cocoa.macosx.aarch64
     uses: ./.github/workflows/build.yml
     with:
-      runner: ${{ matrix.config.os }}
+      runner: ${{ matrix.runner }}
       java: ${{ matrix.java }}
-      native: ${{ matrix.config.native }}
+      native: ${{ matrix.native }}
       performance: ${{ contains(github.event.pull_request.labels.*.name, 'performance') }}