diff --git a/tools/merge-guard.py b/tools/merge-guard.py
index ebabc66..b71b164 100644
--- a/tools/merge-guard.py
+++ b/tools/merge-guard.py
@@ -207,13 +207,26 @@ def leg(name, ok, detail):
             detail += f"  ⛔ net-negative in {len(losers)} file(s): {top}{more}"
         leg("4 three-dot diff", add >= dele, detail)
 
-    created = d.get("createdAt") or ""
-    try:
-        age = (datetime.now(timezone.utc)
-               - datetime.fromisoformat(created.replace("Z", "+00:00"))).total_seconds()
-        leg("5 age at merge", age >= 120, f"{int(age)}s since creation")
-    except Exception:
-        leg("5 age at merge", False, f"UNESTABLISHED — unparseable createdAt {created!r}")
+    # ⛔ --shape-only OMITS LEG 5 TOO — the THIRD merge-time leg in this tool, and the one I
+    # left behind after fixing the other two. Measured on PR #599:
+    #     ⛔ 5 age at merge   9s since creation     -> the advisory job went red
+    # A workflow triggered BY the PR's creation observes an age of seconds BY CONSTRUCTION,
+    # and it is not merging, so "was this old enough at merge?" is not a question it can ask.
+    # ⇒ Legs 0, 2 and 5 are facts about THE MERGE EVENT; only 1, 3 and 4 are facts about the
+    # PR's SHAPE. ⚠ The name was right from the start and the implementation kept not catching
+    # up: I fixed leg 0, then leg 2, and each time treated it as a one-off instead of reading
+    # the remaining legs for the same property. Three instances is a class, not a coincidence.
+    if shape_only:
+        leg("5 age at merge", True, "⚠ SKIPPED — --shape-only. A run triggered BY this PR "
+                                    "cannot judge its age at a merge that has not happened.")
+    else:
+        created = d.get("createdAt") or ""
+        try:
+            age = (datetime.now(timezone.utc)
+                   - datetime.fromisoformat(created.replace("Z", "+00:00"))).total_seconds()
+            leg("5 age at merge", age >= 120, f"{int(age)}s since creation")
+        except Exception:
+            leg("5 age at merge", False, f"UNESTABLISHED — unparseable createdAt {created!r}")
 
     return legs
 
diff --git a/tools/test_merge_guard.py b/tools/test_merge_guard.py
index f662d39..7af042c 100644
--- a/tools/test_merge_guard.py
+++ b/tools/test_merge_guard.py
@@ -15,6 +15,7 @@
 import importlib.util
 import io
 import sys
+from datetime import datetime, timezone
 import unittest
 from contextlib import redirect_stderr, redirect_stdout
 from pathlib import Path
@@ -32,6 +33,9 @@ def load():
     return mod
 
 
+NOW_ISO = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
+
+
 def prd(base="main", gate="SUCCESS", reviews=None, state="OPEN",
         created="2020-01-01T00:00:00Z", sha="deadbee"):
     return {
@@ -222,6 +226,24 @@ def test_shape_only_SKIPS_leg0_and_says_so(self):
         self.assertIn("SKIPPED", out)
         self.assertIn("establishes\nNOTHING about who may merge".replace("\n", " "), out)
 
+    def test_shape_only_SKIPS_leg5_because_a_NEW_pr_is_seconds_old(self):
+        """⛔ THE KNOWN-POSITIVE, measured on PR #599: `5 age at merge  9s since creation`.
+
+        A workflow triggered by the PR's own creation sees an age of seconds by construction.
+        It is not merging, so it cannot ask whether the PR was old enough AT MERGE. This is the
+        third merge-time leg in this tool (0 holder, 2 gate, 5 age) and the last to be fixed."""
+        rc, out, _ = drive(self.mod, prd(created=NOW_ISO), ["1", "--shape-only"], session=OTHER)
+        self.assertEqual(rc, 0, "a seconds-old PR must not fail an ADVISORY shape check")
+        self.assertIn("a merge that has not happened", out)
+
+    def test_the_SAME_new_pr_is_still_BLOCKED_from_a_real_merge(self):
+        """★ THE KNOWN-NEGATIVE. Identical input, --shape-only removed. #224 measured 25 of 100
+        PRs merged inside 60s of creation; that guard must survive this exemption intact."""
+        rc, out, _ = drive(self.mod, prd(created=NOW_ISO), ["1"])
+        self.assertEqual(rc, 1, "a seconds-old PR is still BLOCKED from merging")
+        self.assertIn("5 age at merge", out)
+        self.assertNotIn("a merge that has not happened", out)
+
     def test_shape_only_does_NOT_need_the_authority_file(self):
         """⛔ Found by CodeRabbit reviewing this PR, confirmed by measurement first.