diff --git a/.woodpecker/ci.yml b/.woodpecker/ci.yml
index b6b9e30c..ae488a73 100644
--- a/.woodpecker/ci.yml
+++ b/.woodpecker/ci.yml
@@ -56,6 +56,11 @@ steps:
       # and sandboxes a throwaway git repo, so it resolves no real credentials and
       # joins CI directly rather than the exclusions file.
       - bash packages/mosaic/framework/tools/git/test-issue-close-fail-closed.sh
+      # Hermetic behavioural regression for the PreToolUse wrapper guard: proves
+      # it still blocks the three mistakes AND still lets reads, unwrapped
+      # endpoints and ordinary commands through. Both directions are asserted —
+      # a guard that over-blocks gets routed around, which fails just as hard.
+      - bash packages/mosaic/framework/tools/git/test-wrapper-guard.sh
 
   # Blocking gate (#791): a framework upgrade must never write or delete an
   # operator-owned path. The HARD GATE proves an unanticipated operator sentinel
diff --git a/packages/mosaic/framework/tools/git/test-wrapper-guard.sh b/packages/mosaic/framework/tools/git/test-wrapper-guard.sh
new file mode 100755
index 00000000..8c268ec2
--- /dev/null
+++ b/packages/mosaic/framework/tools/git/test-wrapper-guard.sh
@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+# test-wrapper-guard.sh — hermetic behavioural regression for wrapper-guard.sh.
+#
+# Resolves no credentials, touches no network, and creates no repository: the
+# guard reads a hook payload on stdin and answers with an exit code, so the whole
+# contract is testable from fixtures.
+#
+# The fixtures are written to a temp file rather than passed inline, and this is
+# not stylistic. The guard inspects the literal text of the Bash command it is
+# handed. A test that embeds `git clone ... $HOME` inside its own command line
+# trips the guard on the harness instead of on the fixture — which is exactly
+# what happened the first time this was checked by hand. Substring matching over
+# whole command text is the guard's deliberate fail-closed posture; a test that
+# does not account for it silently measures the wrong thing.
+#
+# Exit: 0 = every fixture behaved as specified · 1 = at least one did not
+
+set -uo pipefail
+
+HERE="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
+GUARD="${1:-$HERE/wrapper-guard.sh}"
+[ -x "$GUARD" ] || { printf 'test-wrapper-guard: not executable: %s\n' "$GUARD" >&2; exit 2; }
+
+TMP="$(mktemp -d)"; trap 'rm -rf "$TMP"' EXIT
+FIXTURES="$TMP/fixtures.tsv"
+
+# Each line: <expected-exit> TAB <hook payload> TAB <what it proves>
+# 0 = allowed, 2 = blocked.
+{
+  printf '2\t{"tool_input":{"command":"git clone https://example.invalid/x ~/wt"}}\tcheckout into $HOME is refused\n'
+  printf '2\t{"tool_input":{"command":"git worktree add ~/wt topic"}}\tworktree into $HOME is refused\n'
+  printf '0\t{"tool_input":{"command":"git clone https://example.invalid/x /src/wt"}}\tcheckout onto a work filesystem is fine\n'
+  printf '0\t{"tool_input":{"command":"curl -s -X GET https://git.example.invalid/api/v1/repos/a/b/pulls/1"}}\treads are never blocked\n'
+  printf '2\t{"tool_input":{"command":"curl -X POST -d @b https://git.example.invalid/api/v1/repos/a/b/pulls/1/reviews"}}\treview write has a wrapper\n'
+  printf '2\t{"tool_input":{"command":"curl -X POST -d @b https://git.example.invalid/api/v1/repos/a/b/pulls/1/merge"}}\tmerge write has a wrapper\n'
+  printf '2\t{"tool_input":{"command":"curl -X POST -d @b https://api.github.com/repos/a/b/issues"}}\tGitHub host is covered too\n'
+  printf '0\t{"tool_input":{"command":"curl -X POST -d @b https://git.example.invalid/api/v1/repos/a/b/releases"}}\tan endpoint with no wrapper passes\n'
+  printf '2\t{"tool_input":{"command":"curl -X POST -d {\\"event\\":\\"APPROVE\\"} https://example.invalid/x"}}\tthe APPROVE token is caught anywhere\n'
+  printf '0\t{"tool_input":{"command":"ls -la /src"}}\tordinary commands are untouched\n'
+  printf '0\t{"tool_input":{"command":"MOSAIC_WRAPPER_OVERRIDE=1 curl -X POST -d @b https://git.example.invalid/api/v1/repos/a/b/pulls"}}\tbreak-glass works\n'
+  printf '0\t{"tool_input":{}}\tan empty payload does not block the session\n'
+} > "$FIXTURES"
+
+fail=0 n=0
+while IFS=$'\t' read -r want payload why; do
+  [ -n "${want:-}" ] || continue
+  n=$((n + 1))
+  printf '%s' "$payload" | "$GUARD" >/dev/null 2>&1
+  got=$?
+  if [ "$got" = "$want" ]; then
+    printf 'ok    %s\n' "$why"
+  else
+    printf 'FAIL  %s (want exit %s, got %s)\n' "$why" "$want" "$got"
+    fail=1
+  fi
+done < "$FIXTURES"
+
+printf '\n'
+if [ "$fail" -eq 0 ]; then
+  printf 'wrapper-guard: %d/%d fixtures behaved as specified.\n' "$n" "$n"
+else
+  cat <<'EOF'
+wrapper-guard drifted from its contract.
+
+A guard that blocks too much gets routed around, and a guard that blocks too
+little is decoration. Both directions are failures here, which is why the
+allowed cases are asserted as hard as the blocked ones.
+EOF
+fi
+exit "$fail"
diff --git a/packages/mosaic/framework/tools/git/wrapper-guard.sh b/packages/mosaic/framework/tools/git/wrapper-guard.sh
index 685ea328..9e815c13 100755
--- a/packages/mosaic/framework/tools/git/wrapper-guard.sh
+++ b/packages/mosaic/framework/tools/git/wrapper-guard.sh
@@ -39,7 +39,14 @@ CMD="$(printf '%s' "$INPUT" | jq -r '.tool_input.command // empty' 2>/dev/null |
 case "$CMD" in *MOSAIC_WRAPPER_OVERRIDE=1*) exit 0 ;; esac
 [ "${MOSAIC_WRAPPER_OVERRIDE:-0}" = "1" ] && exit 0
 
-W="$HOME/.config/mosaic/tools/git"
+# The wrappers this guard points at are its own siblings. Resolving relative to
+# this file — rather than to a hardcoded $HOME/.config/mosaic — means the guard
+# names the wrappers from the same install it was launched from, and that it
+# still works from a repo checkout with no installed mosaic home (which is how it
+# is exercised in CI). $HOME remains the fallback for a guard invoked by an
+# absolute path from somewhere unusual.
+W="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
+[ -x "$W/pr-review.sh" ] || W="$HOME/.config/mosaic/tools/git"
 
 # ---- 1. checkout into $HOME ------------------------------------------------
 if printf '%s' "$CMD" | grep -Eq 'git[^|;&]*(clone|worktree[[:space:]]+add)'; then