diff --git a/bin/omarchy-plugin-add b/bin/omarchy-plugin-add
index f0bdfca5..9fa0e6c0 100755
--- a/bin/omarchy-plugin-add
+++ b/bin/omarchy-plugin-add
@@ -93,6 +93,15 @@ if [[ -z $url ]]; then
   [[ -n $url ]] || fail "a git URL is required"
 fi
 
+# git reads a leading dash as an option, and `<helper>::<address>` as a remote
+# helper to run at clone time. Reject both so an untrusted URL cannot smuggle a
+# transport helper that executes before the plugin is validated or enabled. An
+# scp-style IPv6 host such as git@[2001:db8::1]:org/repo.git carries `::` too and
+# must still clone.
+if [[ $url == -* || $url =~ ^[A-Za-z0-9][A-Za-z0-9+.-]*:: ]]; then
+  fail "'$url' names a git option or transport helper, not a repository."
+fi
+
 if (( ! ASSUME_YES )); then
   cat >&2 <<WARN
 
diff --git a/test/shell.d/plugin-add-test.sh b/test/shell.d/plugin-add-test.sh
index 406526df..477d39a8 100644
--- a/test/shell.d/plugin-add-test.sh
+++ b/test/shell.d/plugin-add-test.sh
@@ -56,3 +56,108 @@ grep -qF "plugin id 'acme.same' is already used by" <<<"$output" ||
 [[ ! -e $test_home/.config/omarchy/plugins/acme.same ]] ||
   fail "plugin add leaves a target behind after refusing a duplicate id"
 pass "plugin add refuses an installed manifest id regardless of directory name"
+
+# --- URL transport-helper guard -------------------------------------------
+#
+# The guard refuses git transport helpers (`<name>::…`) and option-shaped URLs
+# before `git clone` runs, matching omarchy-theme-install. A git stub records
+# whether clone was reached, so the guard is exercised with no network: reaching
+# the stub proves a URL passed the guard; not reaching it proves the guard
+# rejected the URL first.
+
+guard_stubs="$TMPDIR/guard-stubs"
+mkdir -p "$guard_stubs"
+cat >"$guard_stubs/omarchy-shell" <<'STUB'
+#!/bin/bash
+exit 0
+STUB
+chmod +x "$guard_stubs/omarchy-shell"
+
+clone_marker="$TMPDIR/git-clone-reached"
+cat >"$guard_stubs/git" <<STUB
+#!/bin/bash
+if [[ \$1 == "clone" ]]; then
+  touch "$clone_marker"
+  exit 1
+fi
+exit 0
+STUB
+chmod +x "$guard_stubs/git"
+
+# A gum stub that answers `gum input` with a caller-chosen value, so a test can
+# drive any URL through the interactive prompt path.
+cat >"$guard_stubs/gum" <<'STUB'
+#!/bin/bash
+if [[ $1 == "input" ]]; then
+  printf '%s\n' "$GUM_INPUT_VALUE"
+fi
+STUB
+chmod +x "$guard_stubs/gum"
+
+add_url() {
+  HOME="$test_home" OMARCHY_PATH="$ROOT" PATH="$guard_stubs:$ROOT/bin:$PATH" \
+    omarchy-plugin-add "$1" --yes 2>&1
+}
+
+# Transport helpers reach the guard, are named as such, and never reach clone.
+for bad in "ext::sh -c touch /tmp/omarchy-guard-test" "fd::17"; do
+  rm -f "$clone_marker"
+  output=$(add_url "$bad") &&
+    fail "plugin add rejects a transport-helper URL: $bad" "$output"
+  grep -qF "names a git option or transport helper" <<<"$output" ||
+    fail "plugin add names the transport-helper rejection: $bad" "$output"
+  [[ ! -e $clone_marker ]] ||
+    fail "plugin add reached git clone for a transport-helper URL: $bad"
+done
+pass "plugin add rejects transport-helper URLs before cloning"
+
+# Option-shaped URLs on argv are refused before clone — by the option parser
+# (`-*` falls to "unknown add option"), not the guard. The guard's own
+# leading-dash arm is only reachable through the interactive gum prompt and is
+# exercised separately below.
+for bad in "-oProxyCommand=x" "--upload-pack=x"; do
+  rm -f "$clone_marker"
+  output=$(add_url "$bad") &&
+    fail "plugin add rejects an option-shaped URL: $bad" "$output"
+  [[ ! -e $clone_marker ]] ||
+    fail "plugin add reached git clone for an option-shaped URL: $bad"
+done
+pass "plugin add rejects option-shaped URLs before cloning"
+
+# The guard's leading-dash arm is only reachable through `gum input`: argv
+# dashes die in the option parser first. interactive() requires a TTY on stdin
+# and stdout, so run this one case on a pty via util-linux `script -qec` (the
+# suite's existing pty idiom); gum itself is stubbed, so no rendering happens.
+# Probe script's util-linux syntax first and skip cleanly where it is missing.
+if script -qec true /dev/null >/dev/null 2>&1; then
+  rm -f "$clone_marker"
+  status=0
+  raw=$(GUM_INPUT_VALUE="-oProxyCommand=x" HOME="$test_home" OMARCHY_PATH="$ROOT" \
+    PATH="$guard_stubs:$ROOT/bin:$PATH" \
+    script -qec "omarchy-plugin-add --yes" /dev/null) || status=$?
+  output=$(tr -d '\r' <<<"$raw")
+  (( status != 0 )) ||
+    fail "plugin add rejects an option-shaped URL from the gum prompt" "$output"
+  grep -qF "names a git option or transport helper" <<<"$output" ||
+    fail "plugin add names the guard rejection for the gum-prompt URL" "$output"
+  [[ ! -e $clone_marker ]] ||
+    fail "plugin add reached git clone for an option-shaped gum-prompt URL"
+  pass "plugin add guard rejects an option-shaped URL from the interactive prompt"
+else
+  pass "script -qec unavailable; skipping the interactive gum-prompt guard case"
+fi
+
+# Legitimate URL forms pass the guard and reach git clone (stubbed, no network).
+for good in \
+  "https://github.com/acme/omarchy-weather.git" \
+  "git@github.com:acme/repo.git" \
+  "ssh://git@github.com/acme/repo.git" \
+  "git@[2001:db8::1]:org/repo.git"; do
+  rm -f "$clone_marker"
+  output=$(add_url "$good") || true
+  ! grep -qF "names a git option or transport helper" <<<"$output" ||
+    fail "plugin add wrongly rejected a legitimate URL: $good" "$output"
+  [[ -e $clone_marker ]] ||
+    fail "plugin add did not reach git clone for a legitimate URL: $good" "$output"
+done
+pass "plugin add lets legitimate git URLs reach git clone"