diff --git a/git/deps.manifest.tsv b/git/deps.manifest.tsv
new file mode 100644
index 0000000..03d245b
--- /dev/null
+++ b/git/deps.manifest.tsv
@@ -0,0 +1,21 @@
+# ac/* internal cross-repo submodule manifest (path: deps/<repo>)
+# Format: parent_repo<TAB>dep_repo[:branch] (comma-separated deps)
+# Used by sync-repo-deps-submodules.sh — external deps stay in third-party/ per repo.
+ac-platform-php	ac-platform-db
+ac-ms-build	ac-platform-php,ac-platform-db
+ac-ms-devices	ac-platform-php,ac-platform-db
+ac-ms-graphs	ac-platform-php,ac-platform-db
+ac-ms-identity	ac-platform-php,ac-platform-db
+ac-ms-issues	ac-platform-php,ac-platform-db
+ac-ms-rbac	ac-platform-php,ac-platform-db
+ac-ms-remote-access	ac-platform-php,ac-platform-db
+ac-ms-tickets	ac-platform-php,ac-platform-db
+ac-ms-url-shortener	ac-platform-db
+ac-be-access	ac-platform-php,ac-platform-web,ac-ms-rbac
+ac-be-auth	ac-platform-php,ac-platform-web,ac-ms-identity
+ac-be-builder	ac-platform-php,ac-platform-web,ac-ms-build
+ac-be-graphs	ac-platform-php,ac-platform-web,ac-ms-graphs
+ac-be-issues	ac-platform-php,ac-platform-web,ac-ms-issues,ac-ms-tickets
+ac-be-remote-access	ac-platform-php,ac-platform-web,ac-ms-remote-access
+ac-be-tickets	ac-platform-php,ac-platform-web,ac-ms-tickets
+ac-be-hub	ac-platform-web
\ No newline at end of file
diff --git a/git/sync-repo-deps-submodules.sh b/git/sync-repo-deps-submodules.sh
new file mode 100755
index 0000000..f09149c
--- /dev/null
+++ b/git/sync-repo-deps-submodules.sh
@@ -0,0 +1,102 @@
+#!/bin/sh
+# Register internal ac/* repos as git submodules under deps/<name>.
+# External upstreams (libvpx, opus, …) belong in third-party/ — not this script.
+#
+# Usage:
+#   ./sync-repo-deps-submodules.sh ac-be-remote-access
+#   ./sync-repo-deps-submodules.sh --all          # every row in deps.manifest.tsv
+#   AC_GIT_BASE=git://127.0.0.1/ac ./sync-repo-deps-submodules.sh --all
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+MANIFEST="${DEPS_MANIFEST:-$SCRIPT_DIR/deps.manifest.tsv}"
+AC_GIT_BASE="${AC_GIT_BASE:-git://f0xx.org/ac}"
+DEFAULT_BRANCH="${AC_GIT_BRANCH:-next}"
+GIT_AUTHOR_NAME="${GIT_AUTHOR_NAME:-Anton Afanasyeu}"
+GIT_AUTHOR_EMAIL="${GIT_AUTHOR_EMAIL:-a.afanasieff@gmail.com}"
+export GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL
+export GIT_COMMITTER_NAME="$GIT_AUTHOR_NAME" GIT_COMMITTER_EMAIL="$GIT_AUTHOR_EMAIL"
+
+log() { printf '[sync-deps] %s\n' "$*"; }
+warn() { printf '[sync-deps] WARN: %s\n' "$*" >&2; }
+
+deps_for_repo() {
+	_repo="$1"
+	awk -F'\t' -v r="$_repo" '$1 == r && $2 != "" { print $2; exit }' "$MANIFEST"
+}
+
+add_dep() {
+	_parent="$1"
+	_dep="$2"
+	_branch="${3:-$DEFAULT_BRANCH}"
+	_path="deps/$_dep"
+	_url="${AC_GIT_BASE}/${_dep}"
+	[ -e "$_parent/.git" ] || { warn "skip $_parent (not a git repo)"; return 1; }
+	cd "$_parent"
+	if [ -d "$_path/.git" ] || [ -f "$_path/.git" ]; then
+		log "$_parent: $_path already present"
+		return 0
+	fi
+	mkdir -p deps
+	log "$_parent: submodule add $_dep → $_path"
+	git submodule add -b "$_branch" "$_url" "$_path"
+	return 0
+}
+
+sync_one() {
+	_repo="$1"
+	_root="${REPO_ROOT:-}"
+	if [ -n "$_root" ]; then
+		_parent="$_root/$_repo"
+	else
+		_parent="$_repo"
+	fi
+	_deps="$(deps_for_repo "$_repo")"
+	[ -n "$_deps" ] || { warn "no manifest entry for $_repo"; return 0; }
+	_old_ifs="$IFS"
+	IFS=','
+	for _entry in $_deps; do
+		IFS="$_old_ifs"
+		_dep="$_entry"
+		_branch="$DEFAULT_BRANCH"
+		case "$_entry" in
+			*:*)
+				_dep="${_entry%%:*}"
+				_branch="${_entry#*:}"
+				;;
+		esac
+		add_dep "$_parent" "$_dep" "$_branch" || true
+	done
+	IFS="$_old_ifs"
+	cd "$_parent"
+	if git diff --cached --quiet; then
+		log "$_repo: no submodule changes"
+		return 0
+	fi
+	git commit -m "deps: register internal ac/* submodules under deps/"
+	log "$_repo: committed deps submodules"
+}
+
+if [ ! -f "$MANIFEST" ]; then
+	echo "missing manifest: $MANIFEST" >&2
+	exit 1
+fi
+
+case "${1:-}" in
+	--all)
+		awk -F'\t' '$1 !~ /^#/ && $1 != "" { print $1 }' "$MANIFEST" | while read -r _r; do
+			sync_one "$_r"
+		done
+		;;
+	-h|--help)
+		echo "Usage: $0 <repo>|--all"
+		exit 0
+		;;
+	"")
+		echo "repo name or --all required" >&2
+		exit 2
+		;;
+	*)
+		sync_one "$1"
+		;;
+esac