diff --git a/.github/workflows/compile_macos.yml b/.github/workflows/compile_macos.yml
new file mode 100644
index 00000000000..d7998136efa
--- /dev/null
+++ b/.github/workflows/compile_macos.yml
@@ -0,0 +1,75 @@
+name: MacOS build
+
+on:
+  push:
+    branches:
+    - 'main'
+    paths-ignore:
+      - 'docs/**'
+  pull_request:
+    branches:
+      - '**'
+    paths-ignore:
+      - 'docs/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: macos-15
+    steps:
+    - name: install Python 3.10
+      uses: actions/setup-python@v6
+      with:
+        python-version: "3.10"
+
+    - uses: actions/checkout@v6
+
+    - name: Cache - Restore Homebrew Packages
+      uses: actions/cache@v5
+      with:
+        path: ~/Library/Caches/Homebrew/downloads
+        key: macos-homebrew-${{ runner.arch }}-${{ hashFiles('Tools/setup/macos.sh', 'Tools/setup/macos_ci_pins.sh', 'Tools/setup/homebrew-pins.txt', 'Tools/setup/protobuf-pin.txt', 'Tools/setup/gz-tap-pin.txt') }}
+        restore-keys: |
+          macos-homebrew-${{ runner.arch }}-
+
+    - name: Cache - Restore pip Packages
+      uses: actions/cache@v5
+      with:
+        path: ~/Library/Caches/pip
+        key: macos-pip-${{ runner.arch }}-${{ hashFiles('Tools/setup/requirements.txt') }}
+        restore-keys: |
+          macos-pip-${{ runner.arch }}-
+
+    - name: setup
+      env:
+        # Read the checked-out package repos. The default is a live index,
+        # which ignores those checkouts.
+        HOMEBREW_NO_AUTO_UPDATE: "1"
+        HOMEBREW_NO_INSTALL_FROM_API: "1"
+      run: |
+        ./Tools/setup/macos_ci_pins.sh
+        ./Tools/setup/macos.sh --sim-tools
+        echo "${{ github.workspace }}/.venv/bin" >> $GITHUB_PATH
+
+    - uses: ./.github/actions/setup-ccache
+      id: ccache
+      with:
+        cache-key-prefix: ccache-macos-15
+        max-size: 200M
+
+    - name: Build px4_sitl
+      run: make px4_sitl
+
+    - name: Cache - Stats after px4_sitl
+      run: ccache -s
+
+    - name: Build px4_fmu-v5_default
+      run: make px4_fmu-v5_default
+
+    - uses: ./.github/actions/save-ccache
+      if: always()
+      with:
+        cache-primary-key: ${{ steps.ccache.outputs.cache-primary-key }}
diff --git a/.github/workflows/macos_gz_tap_pin_refresh.yml b/.github/workflows/macos_gz_tap_pin_refresh.yml
new file mode 100644
index 00000000000..68ace19bad8
--- /dev/null
+++ b/.github/workflows/macos_gz_tap_pin_refresh.yml
@@ -0,0 +1,64 @@
+name: macOS - Refresh gz tap pin
+
+# Tools/setup/macos.sh pins osrf/simulation to Tools/setup/gz-tap-pin.txt so
+# --sim-tools pours Gazebo bottles instead of compiling them, and protobuf to
+# Tools/setup/protobuf-pin.txt so those bottles' generated headers still
+# compile (see those files). OSRF advances the tap several times a week and
+# homebrew-core moves protobuf on its own schedule, so once a week this moves
+# the tap pin to the newest commit whose Gazebo formulae are all bottled,
+# repoints the protobuf pin at whatever those bottles were built against, and
+# opens a PR for it. Tools/ci/refresh_gz_tap_pin.rb does the work under
+# Homebrew's Ruby and can be run by hand on any Mac.
+
+on:
+  schedule:
+    - cron: '0 9 * * 1' # Mondays at 09:00 UTC
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  refresh:
+    # Same runner as the MacOS build.
+    runs-on: macos-15
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Find the newest fully bottled osrf/simulation commit
+        id: pin
+        env:
+          # Walking homebrew-core's protobuf history goes through the GitHub
+          # API, which is rate limited per IP for runners without this.
+          HOMEBREW_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: brew ruby Tools/ci/refresh_gz_tap_pin.rb
+
+      - name: Open PR with the new pins
+        if: steps.pin.outputs.needs_bump == 'true'
+        uses: peter-evans/create-pull-request@v8
+        with:
+          # The PX4BuildBot PAT rather than GITHUB_TOKEN so the PR runs the
+          # MacOS build workflow, which is what verifies the new pin.
+          token: ${{ secrets.PX4BUILTBOT_PERSONAL_ACCESS_TOKEN }}
+          author: ${{ secrets.PX4BUILDBOT_USER }} <${{ secrets.PX4BUILDBOT_EMAIL }}>
+          committer: ${{ secrets.PX4BUILDBOT_USER }} <${{ secrets.PX4BUILDBOT_EMAIL }}>
+          branch: px4buildbot/gz-tap-pin
+          delete-branch: true
+          add-paths: |
+            Tools/setup/gz-tap-pin.txt
+            Tools/setup/protobuf-pin.txt
+          commit-message: "build(macos): ${{ steps.pin.outputs.summary }}"
+          title: "build(macos): ${{ steps.pin.outputs.summary }}"
+          body: |
+            Weekly check of the two macOS Gazebo pins. `Tools/setup/gz-tap-pin.txt` holds osrf/simulation at the newest commit where every formula `macos.sh --sim-tools` poured at the previous pin still has a bottle Homebrew pours on macos-15 and every bottle tarball is still served. `Tools/setup/protobuf-pin.txt` holds protobuf at the version those bottles were built against, which is the only one their generated headers compile against.
+
+            | pin | from | to |
+            | --- | --- | --- |
+            | osrf/simulation | `${{ steps.pin.outputs.old_pin }}` | `${{ steps.pin.outputs.new_pin }}` |
+            | protobuf | `${{ steps.pin.outputs.old_protobuf_version }}` (`${{ steps.pin.outputs.old_protobuf_pin }}`) | `${{ steps.pin.outputs.protobuf_version }}` (`${{ steps.pin.outputs.new_protobuf_pin }}`) |
+
+            An empty "to" means that pin did not move.
+
+            Tap changes: https://github.com/osrf/homebrew-simulation/compare/${{ steps.pin.outputs.old_pin }}...${{ steps.pin.outputs.new_pin || steps.pin.outputs.old_pin }}
+
+            The MacOS build legs on this PR are the real test. Merge once both pour the gz bottles without compiling anything from osrf/simulation.
diff --git a/Tools/ci/refresh_gz_tap_pin.rb b/Tools/ci/refresh_gz_tap_pin.rb
index d1757b3764b..d766de36f14 100644
--- a/Tools/ci/refresh_gz_tap_pin.rb
+++ b/Tools/ci/refresh_gz_tap_pin.rb
@@ -27,7 +27,8 @@
 #
 # The formula names are read from macos.sh so there is no second list to
 # keep in sync. The bottle tag match is Homebrew's own, which on macOS also
-# accepts a bottle built on an older macOS of the same arch.
+# accepts a bottle built on an older macOS of the same arch, so a commit
+# that passes on the oldest macOS CI runs on passes on the newer ones too.
 #
 # Formula#bottle is deliberately not used: `brew ruby` runs in a child of
 # the brew process, which has already consumed the HOMEBREW_*_DEFAULT_PREFIX
diff --git a/Tools/setup/gz-tap-pin.txt b/Tools/setup/gz-tap-pin.txt
index 28732288763..9010401cc73 100644
--- a/Tools/setup/gz-tap-pin.txt
+++ b/Tools/setup/gz-tap-pin.txt
@@ -4,5 +4,6 @@
 # dependency bump and rebuilds them days later. The tarballs stay on S3, so
 # pinning keeps the install binary instead of compiling Gazebo from source.
 # Move it to the newest commit where every gz formula macos.sh installs still
-# carries a bottle block. Tools/ci/refresh_gz_tap_pin.rb finds that commit.
+# carries a bottle block. Tools/ci/refresh_gz_tap_pin.rb does that, weekly
+# from .github/workflows/macos_gz_tap_pin_refresh.yml or by hand.
 9403d12a474c239604243c77751fa53ad95ba16f
diff --git a/Tools/setup/homebrew-pins.txt b/Tools/setup/homebrew-pins.txt
new file mode 100644
index 00000000000..8acf098ab7c
--- /dev/null
+++ b/Tools/setup/homebrew-pins.txt
@@ -0,0 +1,11 @@
+# Commits macOS CI checks out before installing. A newer package is a change
+# to this file, or to protobuf-pin.txt (homebrew-core) or gz-tap-pin.txt
+# (osrf/simulation).
+#
+# Homebrew 7.0.6. The other two are the tips of those repos on 2026-09-18,
+# the last day this job was green before protobuf moved.
+#
+# <name> <commit>
+brew 570982948a8a194f0f42f43f4a5bce2d1c9f64cb
+osx-cross/arm e3bb686fb159097c2fb3ee6d1acb3f7e4dd8a184
+px4/px4 f78b7a3d5aa98dc23171a63f2c2958ce69f98889
diff --git a/Tools/setup/macos.sh b/Tools/setup/macos.sh
index 8babebe71d8..c92b97c4287 100755
--- a/Tools/setup/macos.sh
+++ b/Tools/setup/macos.sh
@@ -38,6 +38,20 @@ do
 	fi
 done
 
+# Leave a checkout that is already there. `brew tap` on one would try to
+# unshallow it, and CI has already checked these repos out at a commit.
+brew_tap() {
+	local name="$1"
+	local user="${name%%/*}"
+	local repo="${name#*/}"
+	local path
+	path="$(brew --repo)/Library/Taps/${user}/homebrew-${repo}"
+	if [[ -d "${path}/.git" ]]; then
+		return 0
+	fi
+	brew tap "$name"
+}
+
 echo "[macos.sh] Installing the development dependencies for the PX4 Autopilot"
 
 if ! command -v brew &> /dev/null
@@ -79,8 +93,8 @@ if brew trust --help &> /dev/null; then
 	brew trust PX4/px4
 fi
 
-brew tap osx-cross/arm
-brew tap PX4/px4
+brew_tap osx-cross/arm
+brew_tap PX4/px4
 
 # Package list. This replaces the px4-dev meta-formula, which is kept
 # as a deprecated no-op upstream. See PX4/homebrew-px4 for history.
@@ -147,13 +161,13 @@ if [[ $INSTALL_SIM == "--sim-tools" ]]; then
 		brew trust osrf/simulation
 	fi
 
-	brew tap osrf/simulation
+	brew_tap osrf/simulation
 
 	# OSRF drops the gz bottle blocks within minutes of a breaking
 	# homebrew-core dependency bump and rebuilds them days later, so an
 	# unpinned tap compiles Gazebo from source for a large part of the
-	# year. Pin unconditionally so the install stays on bottles. See
-	# gz-tap-pin.txt.
+	# year. Pin unconditionally so dev machines get the same fast, binary
+	# install as CI. See gz-tap-pin.txt.
 	GZ_TAP_PIN=$(grep -v '^#' "${DIR}/gz-tap-pin.txt" | tr -d '[:space:]')
 	if [[ -n $GZ_TAP_PIN ]]; then
 		GZ_TAP_DIR=$(brew --repo osrf/simulation)
@@ -266,7 +280,8 @@ if [[ $INSTALL_SIM == "--sim-tools" ]]; then
 	# XQuartz is required for Gazebo GUI display on macOS.
 	if ! brew list --cask xquartz &> /dev/null; then
 		echo "[macos.sh] Installing XQuartz (required for Gazebo display)"
-		brew install --cask xquartz
+		# XQuartz is not in the pinned package repos.
+		env -u HOMEBREW_NO_INSTALL_FROM_API brew install --cask xquartz
 	fi
 
 	# jMAVSim requires a JDK (Java 17 LTS recommended)
diff --git a/Tools/setup/macos_ci_pins.sh b/Tools/setup/macos_ci_pins.sh
new file mode 100755
index 00000000000..592f35f5c41
--- /dev/null
+++ b/Tools/setup/macos_ci_pins.sh
@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+
+# Check out the Homebrew repos the macOS CI install reads, at the commits
+# recorded next to this script. `brew install` otherwise follows the live
+# package list and ignores a checkout.
+
+set -euo pipefail
+
+DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+
+export HOMEBREW_NO_AUTO_UPDATE=1
+export HOMEBREW_NO_INSTALL_FROM_API=1
+
+if ! command -v brew >/dev/null 2>&1; then
+	echo "macos_ci_pins.sh: brew is not installed" >&2
+	exit 1
+fi
+
+first_field() {
+	local file="$1"
+	local n="$2"
+	grep -v -e '^#' -e '^[[:space:]]*$' "$file" | head -n 1 | awk -v n="$n" '{print $n}'
+}
+
+pin_sha() {
+	local name="$1"
+	grep -E "^${name}[[:space:]]+" "${DIR}/homebrew-pins.txt" | awk '{print $2}'
+}
+
+fetch_and_checkout() {
+	local path="$1"
+	local sha="$2"
+
+	if [[ -z "$sha" ]]; then
+		echo "macos_ci_pins.sh: no commit for ${path}" >&2
+		exit 1
+	fi
+
+	echo "macos_ci_pins.sh: ${path} ${sha}"
+	git -C "$path" fetch -q --depth 1 origin "$sha"
+	git -C "$path" checkout -q -f --detach "$sha"
+}
+
+# The Homebrew install itself is already a git repo on the runner. Do not
+# recreate that directory: it is the prefix every package lives under.
+checkout_brew() {
+	local sha="$1"
+
+	if [[ ! -d "${BREW_REPO}/.git" ]]; then
+		echo "macos_ci_pins.sh: ${BREW_REPO} is not a git repo" >&2
+		exit 1
+	fi
+	fetch_and_checkout "$BREW_REPO" "$sha"
+}
+
+clone_at() {
+	local path="$1"
+	local url="$2"
+	local sha="$3"
+
+	if [[ ! -d "${path}/.git" ]]; then
+		rm -rf "$path"
+		mkdir -p "$(dirname "$path")"
+		git init -q "$path"
+		git -C "$path" remote add origin "$url"
+	fi
+	fetch_and_checkout "$path" "$sha"
+}
+
+BREW_REPO=$(brew --repo)
+TAPS="${BREW_REPO}/Library/Taps"
+CORE_SHA=$(first_field "${DIR}/protobuf-pin.txt" 1)
+GZ_SHA=$(first_field "${DIR}/gz-tap-pin.txt" 1)
+
+checkout_brew "$(pin_sha brew)"
+clone_at "${TAPS}/homebrew/homebrew-core" "https://github.com/Homebrew/homebrew-core" "$CORE_SHA"
+clone_at "${TAPS}/osrf/homebrew-simulation" "https://github.com/osrf/homebrew-simulation" "$GZ_SHA"
+clone_at "${TAPS}/osx-cross/homebrew-arm" "https://github.com/osx-cross/homebrew-arm" "$(pin_sha osx-cross/arm)"
+clone_at "${TAPS}/px4/homebrew-px4" "https://github.com/PX4/homebrew-px4" "$(pin_sha px4/px4)"
diff --git a/Tools/setup/protobuf-pin.txt b/Tools/setup/protobuf-pin.txt
index 5cbbaa4439e..882d72e9680 100644
--- a/Tools/setup/protobuf-pin.txt
+++ b/Tools/setup/protobuf-pin.txt
@@ -12,7 +12,8 @@
 # the rest of the simulation packages are in, so the two pins always agree
 # and a protobuf release is a no-op here. Tools/ci/refresh_gz_tap_pin.rb
 # reads the version out of the pinned gz-msgs10 bottle's install receipt and
-# moves both pins together.
+# moves both pins together, weekly from
+# .github/workflows/macos_gz_tap_pin_refresh.yml.
 #
 # Holding protobuf back holds back its ABI too: homebrew-core bottles that
 # were rebuilt against a newer protobuf (of what macos.sh installs, only
diff --git a/docs/en/dev_setup/dev_env_mac.md b/docs/en/dev_setup/dev_env_mac.md
index 9f31fd27ff1..7ecfee6634b 100644
--- a/docs/en/dev_setup/dev_env_mac.md
+++ b/docs/en/dev_setup/dev_env_mac.md
@@ -7,6 +7,7 @@ This environment can be used to build PX4 for:
 - [Gazebo Simulation](../sim_gazebo_gz/index.md) (Gazebo Harmonic)
 
 It works on both Intel and Apple Silicon Macs.
+PX4 CI exercises this setup on Apple Silicon runners only; Intel is not covered by CI.
 
 ::: tip
 This setup is supported by the PX4 dev team.