diff --git a/CLAUDE.md b/CLAUDE.md
index c74a0f1..bedf7d9 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -58,7 +58,7 @@ All in `Shared/Model/`:
 
 ### Platforms, Tooling & Entitlements
 - iOS 26 / watchOS 26 / macOS 26; Swift 6 with `SWIFT_STRICT_CONCURRENCY: complete` on all targets.
-- Build number (git commit count), `BuildDate`, and `BuildHash` are stamped by the `app-versioning` skill's `update_build_info.sh` (referenced in place from `../indie-skills`, a post-build phase; release tagging is opt-in via `RELEASE_TAGGING=1`). `Scripts/` holds the App Store / TestFlight release pipeline.
+- Build number, `BuildDate`, and `BuildHash` are stamped by the vendored `Scripts/update_build_info.sh` (a post-build phase; release tagging is opt-in via `RELEASE_TAGGING=1`). Build numbers are **platform-partitioned** from the git commit count — iOS/watchOS get even (2×commits), macOS gets odd (2×commits+1) — because both platforms share one ASC build-number space and the embedded watch app must match the iOS app's `CFBundleVersion`. `Scripts/` also holds the App Store / TestFlight release pipeline.
 - Entitlements: iOS uses CloudDocuments + HealthKit; watch uses HealthKit only; macOS uses app sandbox + CloudDocuments (same bundle ID as iOS — universal purchase). **No CloudKit service, no App Group.**
 - SPM packages: `IndieSync` (file-side iCloud sync core) and `IndieAbout` (in-app About / changelog / license UI).
 
diff --git a/Scripts/update_build_info.sh b/Scripts/update_build_info.sh
new file mode 100755
index 0000000..0a75d3a
--- /dev/null
+++ b/Scripts/update_build_info.sh
@@ -0,0 +1,92 @@
+#!/bin/sh
+
+## app-versioning: platform-partitioned Build Info Script (vendored for Workouts)
+##
+## A vendored variant of the shared app-versioning script (see
+## ../indie-skills/skills/app-versioning/scripts/update_build_info.sh). Workouts'
+## iOS app and Mac app share ONE App Store Connect record (same bundle id,
+## dev.rzen.indie.Workouts — universal purchase), and therefore one build-number
+## sequence: stamping both with the raw commit count would make the second
+## upload collide ("bundle version already used"). Partition the space instead:
+##   - iOS + watchOS -> EVEN build numbers (commit-count * 2)
+##   - macOS         -> ODD  build numbers (commit-count * 2 + 1)
+## watchOS is grouped with iOS (not given its own parity) because the embedded
+## watch app's CFBundleVersion must match its host iOS app's exactly. The
+## platform is read from PLATFORM_NAME, so this one script serves every
+## code-bearing target (iOS app, watch app, watch widget, iOS widget, Mac app)
+## via a single postBuildScripts anchor — no per-target parameters needed.
+##
+## Sets, on every build, in both the target Info.plist and its dSYM:
+##   - CFBundleVersion = commit-count*2 (iOS/watchOS) or commit-count*2+1 (macOS)
+##   - BuildDate       = today's date (for IndieAbout's "Built …" line)
+##   - BuildHash       = short git commit hash
+##
+## Wire as a POST-BUILD Run Script phase with these Input Files:
+##   $(TARGET_BUILD_DIR)/$(INFOPLIST_PATH)
+##   $(DWARF_DSYM_FOLDER_PATH)/$(DWARF_DSYM_FILE_NAME)/Contents/Info.plist
+##
+## Release tagging is opt-in, not automatic. Set RELEASE_TAGGING=1 in the
+## build environment (e.g. `RELEASE_TAGGING=1 xcodebuild ...`) to have this
+## script run `git tag <marketing-version>`. Default builds never tag.
+set -eu
+
+git=$(sh /etc/profile; which git || true)
+if [ -z "$git" ] || [ ! -x "$git" ]; then
+  echo "error: update_build_info.sh: could not resolve a 'git' executable — refusing to stamp a build number." >&2
+  exit 1
+fi
+
+number_of_commits=$("$git" rev-list HEAD --count)
+case "$number_of_commits" in
+  ''|*[!0-9]*)
+    echo "error: update_build_info.sh: 'git rev-list HEAD --count' returned '$number_of_commits', not a positive integer — refusing to stamp a build number." >&2
+    exit 1
+    ;;
+esac
+if [ "$number_of_commits" -le 0 ]; then
+  echo "error: update_build_info.sh: 'git rev-list HEAD --count' returned $number_of_commits — refusing to stamp a build number." >&2
+  exit 1
+fi
+
+git_commit=$("$git" rev-parse --short HEAD)
+
+# Platform-aware build number (see header): iOS/watchOS even, macOS odd.
+case "${PLATFORM_NAME:-}" in
+  macosx*) build_number=$((number_of_commits * 2 + 1)) ;;
+  *)       build_number=$((number_of_commits * 2)) ;;
+esac
+
+target_plist="$TARGET_BUILD_DIR/$INFOPLIST_PATH"
+dsym_plist="$DWARF_DSYM_FOLDER_PATH/$DWARF_DSYM_FILE_NAME/Contents/Info.plist"
+
+bundle_version=$(/usr/libexec/PlistBuddy -c "Print :CFBundleShortVersionString" "$target_plist" 2>/dev/null || true)
+build_date=$(date +%F)
+
+echo "app-versioning: v$bundle_version-$git_commit b$build_number (${PLATFORM_NAME:-}) $build_date"
+
+if [ "${RELEASE_TAGGING:-}" = "1" ]; then
+  if [ -n "$bundle_version" ]; then
+    "$git" tag "$bundle_version"
+    echo "app-versioning: tagged release $bundle_version"
+  else
+    echo "warning: app-versioning: RELEASE_TAGGING=1 but CFBundleShortVersionString could not be read from $target_plist; skipping git tag"
+  fi
+fi
+
+if [ ! -f "$target_plist" ] && [ ! -f "$dsym_plist" ]; then
+  echo "warning: update_build_info.sh: neither the target Info.plist ($target_plist) nor the dSYM Info.plist ($dsym_plist) exists — check that both are wired as Input Files on this Run Script build phase"
+fi
+
+for plist in "$target_plist" "$dsym_plist"; do
+  if [ -f "$plist" ]; then
+    /usr/libexec/PlistBuddy -c "Set :CFBundleVersion $build_number" "$plist"
+
+    /usr/libexec/PlistBuddy -c "Set :BuildDate $build_date" "$plist" 2>/dev/null || \
+    /usr/libexec/PlistBuddy -c "Add :BuildDate string $build_date" "$plist"
+
+    /usr/libexec/PlistBuddy -c "Set :BuildHash $git_commit" "$plist" 2>/dev/null || \
+    /usr/libexec/PlistBuddy -c "Add :BuildHash string $git_commit" "$plist"
+
+    echo "app-versioning: updated $plist"
+  fi
+done
diff --git a/project.yml b/project.yml
index d7a5fe9..c07d15c 100644
--- a/project.yml
+++ b/project.yml
@@ -28,12 +28,19 @@ packages:
     url: https://git.rzen.dev/rzen/indie-backup.git
     from: "2.0.0"
 
-# Shared post-build phase — stamps CFBundleVersion (git commit count), BuildDate, and
-# BuildHash into each target's (and dSYM's) Info.plist. Aliased into every code-bearing
-# target below so the app, watch app, and both widget extensions stamp identical metadata.
+# Shared post-build phase — stamps CFBundleVersion, BuildDate, and BuildHash into each
+# target's (and dSYM's) Info.plist. Vendored at Scripts/update_build_info.sh (not the
+# shared indie-skills copy) because the iOS app and Workouts Mac share ONE App Store
+# Connect record (dev.rzen.indie.Workouts, universal purchase), so both stamping the
+# raw commit count would collide on upload. The script partitions the space instead:
+# iOS + watchOS targets get an EVEN CFBundleVersion (commit-count*2), the Mac target
+# gets ODD (commit-count*2+1) — derived from PLATFORM_NAME inside the script, so this
+# one anchor still serves all five code-bearing targets unmodified. watchOS is grouped
+# with iOS (not given its own parity) because the embedded watch app's CFBundleVersion
+# must match its host iOS app's exactly.
 scriptAnchors:
   updateBuildInfo: &updateBuildInfo
-    - script: '"${SRCROOT}/../indie-skills/skills/app-versioning/scripts/update_build_info.sh"'
+    - script: '"${SRCROOT}/Scripts/update_build_info.sh"'
       name: Update Build Info
       shell: /bin/sh
       basedOnDependencyAnalysis: false