diff --git a/controller/scripts/mojibake_gate.py b/controller/scripts/mojibake_gate.py
new file mode 100644
index 0000000..e64c64e
--- /dev/null
+++ b/controller/scripts/mojibake_gate.py
@@ -0,0 +1,73 @@
+# -*- coding: utf-8 -*-
+"""v0.126.0 mojibake gate — double-encoded UTF-8 can never enter the source again.
+
+A bash-era in-place sweep once mangled Hungarian text by re-encoding already-encoded
+UTF-8 (the "Tárhely"-class defect: á → á). Legitimate Hungarian UTF-8 NEVER decodes
+to the signature characters below, so any hit is a defect. The allowlist is ZERO by
+design — fix the text, don't allowlist it. (Windows grep false-negatives multibyte —
+this gate is Python by the multibyte rule, like emoji_gate.)
+
+Scans every template (web + setup) and every Go source file:
+  - the file must decode as strict UTF-8 (undecodable bytes = broken already), and
+  - the decoded text must contain none of the double-encoding signature characters:
+      Ã (U+00C3)  Â (U+00C2)  Ă (U+0102)  ă (U+0103)  ˘ (U+02D8)  ˇ (U+02C7)
+
+Run from controller/:  python scripts/mojibake_gate.py
+Exit 1 on any hit.
+"""
+import io, os, sys
+
+ROOTS = [
+    os.path.join("internal", "web", "templates"),
+    os.path.join("internal", "setup", "templates"),
+    "internal",  # every .go string literal / comment
+    "cmd",
+]
+
+SIGNATURE = {
+    "Ã": "Ã (a-tilde — á/é/í/ó/ö/ő/ú/ü/ű double-encoded)",
+    "Â": "Â (a-circumflex — NBSP/degree-sign double-encoded)",
+    "Ă": "Ă (a-breve — cp1250 round-trip)",
+    "ă": "ă (a-breve lowercase — cp1250 round-trip)",
+    "˘": "˘ (breve — cp1250 round-trip)",
+    "ˇ": "ˇ (caron — cp1250 round-trip)",
+}
+
+EXTS = (".html", ".css", ".js", ".go")
+
+
+def files():
+    seen = set()
+    for root in ROOTS:
+        if not os.path.isdir(root):
+            continue
+        for dirpath, dirnames, names in os.walk(root):
+            for n in names:
+                p = os.path.join(dirpath, n)
+                if p in seen or not n.endswith(EXTS):
+                    continue
+                seen.add(p)
+                yield p
+
+
+failures = []
+count = 0
+for path in files():
+    count += 1
+    raw = io.open(path, "rb").read()
+    try:
+        text = raw.decode("utf-8")
+    except UnicodeDecodeError as e:
+        failures.append("%s: not valid UTF-8 (%s)" % (path, e))
+        continue
+    for ln, line in enumerate(text.split("\n"), 1):
+        for ch, why in SIGNATURE.items():
+            if ch in line:
+                failures.append("%s:%d: mojibake signature %s in %r" % (path, ln, why, line.strip()[:120]))
+
+if failures:
+    print("mojibake_gate: FAIL (allowlist is zero — fix the text)")
+    for f in failures:
+        print("  - " + f)
+    sys.exit(1)
+print("mojibake_gate: OK (%d files clean — no double-encoding signatures)" % count)