diff --git a/scripts/check-credential-leaks.sh b/scripts/check-credential-leaks.sh
new file mode 100755
index 0000000..a3a66f8
--- /dev/null
+++ b/scripts/check-credential-leaks.sh
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# check-credential-leaks — falla si journald reciente contiene patrones de credencial.
+# Regla permanente: los secretos jamás en logs. Ejecutar manualmente o desde cron
+# (sin timer propio: no fue autorizado).
+set -euo pipefail
+SINCE="${1:-2 hours ago}"
+HITS=$(journalctl --since "$SINCE" --no-pager 2>/dev/null | grep -cE "(postgres|postgresql)://[A-Za-z0-9_]+:[^@[:space:]]{8,}@|nsec1[qpzry9x8gf2tvdw0s3jn54khce6mua7l]{50,}" || true)
+if [ "$HITS" -gt 0 ]; then
+  echo "ALERTA: $HITS líneas de journald (desde $SINCE) contienen patrones de credencial" >&2
+  journalctl --since "$SINCE" --no-pager 2>/dev/null | grep -nE "(postgres|postgresql)://[A-Za-z0-9_]+:[^@[:space:]]{8,}@|nsec1[qpzry9x8gf2tvdw0s3jn54khce6mua7l]{50,}" | sed -E "s#(://[A-Za-z0-9_]+:)[^@[:space:]]{8,}@#\1***@#" | head -5
+  exit 1
+fi
+echo "OK: sin patrones de credencial en journald desde $SINCE"
diff --git a/tests/test_no_credential_patterns.py b/tests/test_no_credential_patterns.py
new file mode 100644
index 0000000..496c466
--- /dev/null
+++ b/tests/test_no_credential_patterns.py
@@ -0,0 +1,68 @@
+"""Regla permanente (2026-10-31): ningún fichero versionado contiene patrones
+de credenciales. Placeholders de .env.example están permitidos.
+
+Fallará si alguien mete un DSN con contraseña real, un token en claro, o
+cualquier valor que deba vivir solo en .env / tokens.json.
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+REPO = Path(__file__).resolve().parent.parent
+SCAN_DIRS = ["runtime", "deploy", "docs", "scripts", "prompts"]
+SCAN_GLOBS = ["*.py", "*.mjs", "*.js", "*.ts", "*.md", "*.yml", "*.yaml", "*.sh", "*.sql"]
+
+# DSN con credencial literal (user:pass@host) — excluye placeholders conocidos
+DSN = re.compile(r"(postgres|postgresql|mysql|mongodb)(\+[a-z]+)?://[A-Za-z0-9_]+:(?!password\b|change-me\b|<[^>]+>)[^@\s/]{8,}@", re.I)
+# tokens hex largos fuera de tests (los fixtures de tests están allowlistados por diseño)
+HEXTOKEN = re.compile(r"\b[0-9a-f]{64}\b")
+# nsec bech32
+NSEC = re.compile(r"nsec1[qpzry9x8gf2tvdw0s3jn54khce6mua7l]{50,}")
+ALLOW_SUBSTR = ("user:password", "change-me", "<", "EXAMPLE", "example", "itest-pg", "0011", "11*", "22*", "33*", "44*")
+
+
+def _iter_files():
+    for d in SCAN_DIRS:
+        base = REPO / d
+        if not base.exists():
+            continue
+        for pat in SCAN_GLOBS:
+            for f in base.rglob(pat):
+                if ".git" in f.parts or "node_modules" in f.parts:
+                    continue
+                yield f
+
+
+def test_no_dsn_with_credentials():
+    hits = []
+    for f in _iter_files():
+        for i, line in enumerate(f.read_text(errors="ignore").splitlines(), 1):
+            if DSN.search(line) and not any(a in line for a in ALLOW_SUBSTR):
+                hits.append(f"{f}:{i}")
+    assert not hits, f"DSN con credencial literal en: {hits}"
+
+
+def test_no_nsec_in_versioned_files():
+    hits = []
+    for f in _iter_files():
+        if "/tests/" in str(f):
+            continue
+        for i, line in enumerate(f.read_text(errors="ignore").splitlines(), 1):
+            if NSEC.search(line):
+                hits.append(f"{f}:{i}")
+    assert not hits, f"nsec en fichero versionado: {hits}"
+
+
+def test_no_raw_hex_tokens_outside_tests():
+    """Tokens hex de 64 chars fuera de tests/ y del conftest (las claves de
+    test viven solo en tests/). El outbox no debe contener secretos."""
+    hits = []
+    for f in _iter_files():
+        if "/tests/" in str(f) or f.name == "cayce-identity.md":
+            continue
+        for i, line in enumerate(f.read_text(errors="ignore").splitlines(), 1):
+            if HEXTOKEN.search(line):
+                hits.append(f"{f}:{i}")
+    assert not hits, f"posible token hex versionado: {hits}"