diff --git a/SKILL.md b/SKILL.md
index 9259fb5..134e84e 100644
--- a/SKILL.md
+++ b/SKILL.md
@@ -146,7 +146,16 @@ are heavy; allow several minutes.
 Industry-appropriate, minimal but believable, generated from the brief — the client's own
 partners, products, projects and orders, staged so each hero has a record to fire on.
 Drive it from a `demo_config.json` (see `demo_config.example.json`) and
-`scripts/build_demo.py`. Rules:
+`scripts/build_demo.py`.
+
+**`build_demo.py` is a per-engagement template, not an engine.** It implements one shape
+(products, fleet, credit limits, prestaged receivables) and reads every key with
+`cfg.get()`, so anything it does not implement would otherwise be skipped in silence — a
+`DONE` over an empty database. It now refuses to run on config keys it cannot build, listing
+them; extend the script, or drop the keys. `DEMO_ALLOW_UNKNOWN_KEYS=1` overrides for a
+deliberate partial run. Extend `KNOWN_KEYS` whenever you add a block.
+
+Rules:
 
 - **Get-or-create by name** so re-runs are idempotent.
 - Set the right **currency** first (activate it with `context={'active_test': False}`, set
diff --git a/scripts/build_demo.py b/scripts/build_demo.py
index 06f490c..53c6c78 100644
--- a/scripts/build_demo.py
+++ b/scripts/build_demo.py
@@ -14,6 +14,24 @@ from odoo_connect import x, get_or_create, URL, DB
 CFG = os.path.join(os.path.dirname(os.path.abspath(__file__)), "demo_config.json")
 cfg = json.load(open(CFG, encoding="utf-8"))
 
+# Every key below is read with cfg.get(), so anything this script does not know about is
+# silently skipped. That is how a vertical config (take-offs, progress statements, ...) fed
+# to the stock builder prints DONE over an empty database. Fail loudly instead: this script
+# is a per-engagement TEMPLATE, and an unknown key means it has not been adapted yet.
+KNOWN_KEYS = {
+    "client", "currency", "use_credit_limit", "scope_modules", "products", "customers",
+    "vehicles", "pricelist", "prestage_receivables", "heroes",
+}
+unknown = sorted(k for k in cfg if k not in KNOWN_KEYS and not k.startswith("_"))
+if unknown:
+    print("!! demo_config.json has keys this builder does not implement:")
+    for k in unknown:
+        print(f"     {k}")
+    print("!! They will NOT be created. Either extend this script to handle them, or")
+    print("!! remove them so the config reflects what actually gets built.")
+    if os.environ.get("DEMO_ALLOW_UNKNOWN_KEYS") != "1":
+        raise SystemExit("aborting: unimplemented config keys (set DEMO_ALLOW_UNKNOWN_KEYS=1 to override)")
+
 # 1. currency (must run before invoices)
 cur = cfg.get("currency")
 if cur: