diff --git a/goodwe_controller/test_selfconfig.py b/goodwe_controller/test_selfconfig.py
index 74f55f1..336ea71 100644
--- a/goodwe_controller/test_selfconfig.py
+++ b/goodwe_controller/test_selfconfig.py
@@ -247,6 +247,103 @@ check("...and the caller gets the new token back, so the next save can "
       res["fingerprint"] == selfconfig.fingerprint(_good))
 
 
+# --------------------------------------------------------------------------- #
+print()
+print("2b. ⚠️ THE TWO HALVES OF THE max_w FIX, EACH PINNED SO IT CANNOT BE UNDONE")
+# Review found that BOTH halves reverted with the whole 24-file suite still
+# green - including the half that turns a crash into a SILENT ACCEPTANCE, which
+# is the more dangerous of the two and was a wrong first attempt at this very
+# fix. A fix nothing grades is a fix that comes back. MUTATION.md habit 4.
+from app.inverter import _flat_max_w, build_roster        # noqa: E402
+from app.validate import _number                          # noqa: E402
+
+# ⚠️ THIS CHECK EXISTS BECAUSE THE OBVIOUS ONE HAS A HOLE. "problems_and_ranges
+# does not raise" is ALSO satisfied by the backstop swallowing the exception and
+# returning [] - which is the silent-acceptance bug half two exists to prevent.
+# Measured: with BOTH halves reverted, every max_w check below reported ok and
+# only the forced-boom pins went red. So half one is pinned HERE, on the
+# composition itself, where the backstop cannot answer for it.
+_raised = None
+try:
+    build_roster(base(max_w=""), None)
+except Exception as exc:                                   # noqa: BLE001
+    _raised = exc
+check("⭐ THE COMPOSITION ITSELF TOLERATES A CLEARED max_w - not merely the "
+      "backstop above it. `validate.py`'s `_number()` reads '' as the default, "
+      "so rule 9 sees 2000 and is content; a bare `float('')` in the flat path "
+      "raised instead, inverting inverter.py's own rule that a shape rule 9 "
+      "tolerates must be composable",
+      _raised is None)
+
+# HALF ONE: composition tolerates exactly what rule 9 tolerates.
+for raw in ("", None, 0, False, True, -1, "2000", " 2000 ", "2e3", 1e18):
+    o = base(max_w=raw)
+    expect = _number(o, "max_w", 2000.0)
+    if expect is not None:
+        check(f"_flat_max_w agrees with _number() for max_w={raw!r}",
+              _flat_max_w(o) == expect)
+
+_raised = None
+try:
+    _probs, _ = run(selfconfig.problems_and_ranges(base(max_w=""), None))
+except Exception as exc:                                   # noqa: BLE001
+    _raised, _probs = exc, None
+check("⚠️ A CLEARED max_w BOX ANSWERS WITH A VERDICT, NOT AN EXCEPTION. It "
+      "used to raise ValueError from inside Controller.__init__, which the "
+      "panel served as HTTP 500 on a non-JSON body and the page rendered as "
+      "'cannot reach the add-on' - untrue, for the most prominent limit "
+      "field's most likely transient state",
+      _raised is None)
+check("...and it agrees with the validator, which reads '' as the default",
+      _probs == list(validate_startup_config(base(max_w=""), None, None)))
+
+_raised = None
+try:
+    _probs, _ = run(selfconfig.problems_and_ranges(base(max_w="abc"), None))
+except Exception as exc:                                   # noqa: BLE001
+    _raised, _probs = exc, None
+check("an UNPARSEABLE max_w answers with the validator's own sentence",
+      _raised is None and any("is not a number" in p for p in (_probs or [])))
+
+# HALF ONE, THE PART THAT MAKES IT SAFE RATHER THAN MERELY NOT-CRASHING:
+# clearing the box on the LIVE shape must FAIL CLOSED, not silently halve the
+# rail. `unit_caps_indexed` reads the flat rail through the same `_number`, so
+# the rail collapses to 2000 in lockstep and rule 10 catches the collapse.
+_live = base(max_w=5000, slew_w=400)
+_probs, _ = run(selfconfig.problems_and_ranges(dict(_live), None))
+check("the live shape (5000 W rail, slew_w 400) starts", _probs == [])
+_probs, _ = run(selfconfig.problems_and_ranges(dict(_live, max_w=""), None))
+check("⚠️ CLEARING max_w ON THE LIVE SHAPE IS REFUSED - rule 10 catches the "
+      "rail collapsing to the 2000 default under an explicit 400 W slew, so "
+      "the box cannot be emptied into a quietly halved rail",
+      any("site rail of 2000 W" in p for p in _probs))
+
+# HALF TWO: the backstop cannot report "no problems" for a config it could not
+# compose. Returning [] there enables Save - a crash became a green.
+_orig_roster = selfconfig.build_roster
+
+
+def _boom(*_a, **_kw):
+    raise ValueError("forced boom")
+
+
+selfconfig.build_roster = _boom
+try:
+    _probs, _ = run(selfconfig.problems_and_ranges(base(), None))
+finally:
+    selfconfig.build_roster = _orig_roster
+check("⚠️ THE BACKSTOP NEVER RETURNS AN EMPTY LIST. A roster that cannot be "
+      "composed while the validator names no reason is itself the finding - "
+      "returning [] would turn a crash into a silent acceptance and enable "
+      "Save, which is worse than the 500 it replaced",
+      _probs != [] and len(_probs) == 1)
+check("...and it says so in words, naming the exception",
+      any("could not be composed" in p and "forced boom" in p
+          for p in _probs))
+check("...and the patch was undone, so nothing below inherits it",
+      selfconfig.build_roster is _orig_roster)
+
+
 # --------------------------------------------------------------------------- #
 print()
 print("3. THE OTHER SURFACE WRITES WHILE THIS PAGE IS OPEN")