diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index d6ed692..f5b4d38 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,9 +1,69 @@
-on: [push, pull_request]
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+permissions:
+  contents: read
+
 jobs:
   lint:
+    name: lint
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - uses: arduino/arduino-lint-action@v2
         with:
           library-manager: update
+
+  compile-sketches:
+    name: compile (${{ matrix.board.fqbn }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        board:
+          - fqbn: arduino:avr:uno
+            platforms: |
+              - name: arduino:avr
+          - fqbn: esp32:esp32:esp32
+            platforms: |
+              - name: esp32:esp32
+                source-url: https://espressif.github.io/arduino-esp32/package_esp32_index.json
+          - fqbn: arduino:samd:mkrzero
+            platforms: |
+              - name: arduino:samd
+          - fqbn: rp2040:rp2040:rpipico
+            platforms: |
+              - name: rp2040:rp2040
+                source-url: https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json
+    steps:
+      - uses: actions/checkout@v4
+      - uses: arduino/compile-sketches@v1
+        with:
+          fqbn: ${{ matrix.board.fqbn }}
+          platforms: ${{ matrix.board.platforms }}
+          libraries: |
+            - source-path: ./
+          sketch-paths: |
+            - examples/si5351_calibration
+            - examples/si5351_clk67_example
+            - examples/si5351_example
+            - examples/si5351_ext_ref
+            - examples/si5351_outputs
+            - examples/si5351_phase
+            - examples/si5351_sweeper
+            - examples/si5351_vcxo
+          enable-deltas-report: true
+          sketches-report-path: sketches-reports
+      - uses: actions/upload-artifact@v4
+        with:
+          # Artifact names must match the regex in size-deltas.yml.
+          name: sketches-report-${{ strategy.job-index }}
+          path: sketches-reports
+
+  # Host tests: placeholder. Test design and harnesses are owned by Test Lab;
+  # a host-test job will be added in a separate change once Test Lab supplies it.
diff --git a/.github/workflows/size-deltas.yml b/.github/workflows/size-deltas.yml
new file mode 100644
index 0000000..ff61e59
--- /dev/null
+++ b/.github/workflows/size-deltas.yml
@@ -0,0 +1,27 @@
+name: Report size deltas
+
+# Runs on a schedule (per arduino/report-size-deltas docs) so it gets a
+# write token and can comment on pull requests from forks. It scans recent
+# workflow artifacts named sketches-report-* uploaded by the CI workflow.
+# Note: scheduled workflows only run from the default branch, so this takes
+# effect once merged to master.
+on:
+  schedule:
+    - cron: "*/15 * * * *"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  report:
+    name: report size deltas
+    if: github.repository == 'etherkit/Si5351Arduino'
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      pull-requests: write
+    steps:
+      - uses: arduino/report-size-deltas@v1
+        with:
+          sketches-reports-source: ^sketches-report-.+