diff --git a/tools/re-capture/ring_row.py b/tools/re-capture/ring_row.py
index defe7b80..5536f4a1 100755
--- a/tools/re-capture/ring_row.py
+++ b/tools/re-capture/ring_row.py
@@ -41,6 +41,7 @@ DECOR_ROWS = 50      # window title bar + menu bar live above this
 FOOTER_Y = 620       # the button-legend strip is bright in the gutter too
 NAMES = ["NEW GAME", "LOAD GAME", "TUTORIAL", "OPTIONS", "EXTRAS"]
 ROW0, SPACING = 225.5, 79.25   # measured, main menu, x11grab
+MENU_GLYPH_LO, MENU_GLYPH_HI = 250, 420   # the glyph-327 menu detector
 
 
 def ring_row(img):
@@ -83,7 +84,72 @@ def main_menu_item(y):
     return i
 
 
+def menu_glyph(img):
+    """The green-(A)-glyph pixel count, is_title.py's counter."""
+    a = np.asarray(img.convert("RGB"), dtype=int)
+    r, g, b = a[:, :, 0], a[:, :, 1], a[:, :, 2]
+    return int(((g > 130) & (g - r > 45) & (g - b > 45)).sum())
+
+
+def is_main_menu(img):
+    """Is this frame the MAIN MENU? Row AND signature, not row alone.
+
+    🔴 `main_menu_item(ring_row(f)) is not None` is NOT a main-menu test, and I
+    used it as one. On a TITLE frame the gutter carries a bright cluster at
+    y=243, which is within tolerance of row 0, so the title reads as "NEW GAME"
+    (glyph 714 — the plate's pulse band — against the menu's 327). It never
+    misfired in the sweeps because Ⓑ from a submenu goes to the menu, not the
+    title; the test was simply weaker than it was being trusted to be.
+
+    Both conditions, so a screen must have a main-menu ROW and the menu's glyph
+    SIGNATURE.
+    """
+    if main_menu_item(ring_row(img)) is None:
+        return False
+    return MENU_GLYPH_LO <= menu_glyph(img) <= MENU_GLYPH_HI
+
+
+def _selftest():
+    """The reader must find a ring where one is, refuse where none is, and REFUSE
+    when it is not measuring at all.
+
+    The last is sylpheed-port's: their band check passed identity and the real
+    pair with an EMPTY band list, because every comparison read 0.0 dB — three
+    controls running and none asking whether the measurement was live.
+    """
+    import glob
+    ok = True
+    menu = sorted(glob.glob("/sylph-home/re/*/reach/1-F1.png"))
+    title = sorted(glob.glob("/sylph-home/re/*/reach/3-title.png"))
+    if not menu or not title:
+        print("🔴 SELFTEST UNAVAILABLE: no reference frames"); return 3
+    m, t = Image.open(menu[0]), Image.open(title[0])
+    cases = [("finds the ring on a main menu", ring_row(m) is not None, True),
+             ("names it NEW GAME", main_menu_item(ring_row(m)) == 0, True),
+             ("accepts the main menu", is_main_menu(m), True),
+             ("REJECTS the title (row alone would accept)", is_main_menu(t), False),
+             ("row-alone DOES accept the title — the defect this guards",
+              main_menu_item(ring_row(t)) is not None, True)]
+    for name, got, want in cases:
+        good = (got == want)
+        ok &= good
+        print(f"   {'✅' if good else '🔴'} {name:52} {got} (want {want})")
+    # LIVENESS: a blanked gutter must return None, not a number.
+    import numpy as _np
+    blank = Image.fromarray(_np.zeros((720, 1280, 3), dtype=_np.uint8))
+    live = ring_row(blank) is None
+    ok &= live
+    print(f"   {'✅' if live else '🔴'} refuses a blank frame (liveness)          {not live}")
+    if not ok:
+        print("🔴 RING_ROW SELFTEST FAILED — nothing it reports can be trusted.")
+        return 2
+    print("   ✅ ring_row selftest passed")
+    return 0
+
+
 if __name__ == "__main__":
+    if "--selftest" in sys.argv:
+        sys.exit(_selftest())
     for p in sys.argv[1:]:
         y = ring_row(Image.open(p))
         i = main_menu_item(y)
diff --git a/tools/re-capture/submenu_focus_sweep.py b/tools/re-capture/submenu_focus_sweep.py
index f69cdff3..5c9f3384 100644
--- a/tools/re-capture/submenu_focus_sweep.py
+++ b/tools/re-capture/submenu_focus_sweep.py
@@ -34,7 +34,7 @@ import numpy as np
 from PIL import Image
 
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
-from ring_row import ring_row, main_menu_item, NAMES
+from ring_row import ring_row, main_menu_item, is_main_menu, NAMES
 
 LOG, OUT = sys.argv[1], sys.argv[2]
 W, H = 1280, 720
@@ -158,7 +158,7 @@ _self_test()
 if "--selftest-only" in sys.argv:
     sys.exit(0)
 
-MAIN = wait_until(lambda a: main_menu_item(ring_row(img(a))) is not None
+MAIN = wait_until(lambda a: is_main_menu(img(a))
                   and 250 <= glyph(a) <= 420, "the main menu", 150)
 if MAIN is None:
     sys.exit("never identified the main menu")
@@ -173,7 +173,7 @@ for tgt in TARGETS:
     # 🔴 NARROW test, not whole-frame. A crash dialog covering the screen centre
     # made a whole-frame identity test unable to match ever again, while the ring
     # column the dialog did not cover read correctly throughout.
-    a = wait_until(lambda a: main_menu_item(ring_row(img(a))) is not None,
+    a = wait_until(lambda a: is_main_menu(img(a)),
                    "the main menu (by ring row)", 60)
     if a is None:
         print(f"   SKIP {name}: no main-menu ring row"); continue
@@ -221,7 +221,7 @@ for tgt in TARGETS:
 
     if not press("B", "5801"):
         results[name] = "skipped (B not delivered)"; continue
-    if wait_until(lambda x: main_menu_item(ring_row(img(x))) is not None,
+    if wait_until(lambda x: is_main_menu(img(x)),
                   "the main menu (by ring row)", 60) is None:
         results[name] = "VOID: B did not return to the main menu"; continue
     if not press("A", "5800"):