diff --git a/.github/workflows/fixture-integrity.yml b/.github/workflows/fixture-integrity.yml
new file mode 100644
index 0000000..1b8654b
--- /dev/null
+++ b/.github/workflows/fixture-integrity.yml
@@ -0,0 +1,25 @@
+name: Chimera fixture integrity
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  offline-fixtures:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+      - name: Compile Python files without executing receiver
+        run: python -m py_compile c2_server.py make_svg.py
+      - name: Parse standalone JavaScript
+        run: node --check script.js
+      - name: Check positive and safe-negative fixtures
+        run: python -m unittest discover -s tests -v
diff --git a/README.md b/README.md
index 4b27e9b..ac4c29c 100644
--- a/README.md
+++ b/README.md
@@ -128,6 +128,21 @@ A historical project report written during the initial experiment. It contains s
 
 Treat this README and the executable code as the current description of the project.
 
+## Negative control: safe CRM rendering
+
+The repository now includes two destination fixtures with the same input/output IDs:
+
+| Fixture | Rendering | Expected observation |
+| --- | --- | --- |
+| `crm_scammer_simulato.html` | Deliberately unsafe `innerHTML` sink | The copied HTML-like suffix can become markup under compatible browser conditions. |
+| `crm_safe_simulato.html` | `textContent` sink | The same copied value remains inert, visible text. |
+
+This paired design makes it possible to compare a positive case with a concrete safe negative control, instead of treating execution in a deliberately vulnerable fixture as sufficient evidence of a broader exploit.
+
+The safe fixture does not collect cookies or transmit data. The included CI checks file structure, source syntax, and intended sinks **without running any browser payload or receiver**. Those static checks are not a substitute for a controlled browser compatibility matrix.
+
+To use the fixtures manually, keep the experiment on local loopback and compare the output of both CRM pages with the same controlled sample. Do not expose `c2_server.py` to a shared network: its historical implementation binds to all interfaces and runs in debug mode.
+
 ## What actually triggers execution
 
 The clipboard is only a carrier.
diff --git a/crm_safe_simulato.html b/crm_safe_simulato.html
new file mode 100644
index 0000000..7884c47
--- /dev/null
+++ b/crm_safe_simulato.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<html lang="it">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>Chimera — Safe CRM Control Fixture</title>
+  <style>
+    body { font: 16px/1.5 system-ui, sans-serif; max-width: 48rem; margin: 3rem auto; padding: 0 1.5rem; }
+    label, input { display: block; width: 100%; }
+    input { padding: 0.6rem; margin: 0.5rem 0 1rem; box-sizing: border-box; }
+    button { padding: 0.6rem 1rem; }
+    #sinkArea { margin-top: 1.5rem; border: 2px solid #237a57; padding: 1rem; overflow-wrap: anywhere; white-space: pre-wrap; }
+  </style>
+</head>
+<body>
+  <h1>CRM control — safe rendering</h1>
+  <p>Negative control for Chimera's deliberately vulnerable CRM fixture. This page keeps pasted input inert as text.</p>
+  <label for="nameInput">Nome</label>
+  <input type="text" id="nameInput" autocomplete="off">
+  <button id="saveButton" type="button">SALVA NEL DB (simulazione)</button>
+  <div id="sinkArea" aria-live="polite">I dati salvati appariranno qui come testo.</div>
+  <script>
+    document.getElementById("saveButton").addEventListener("click", function () {
+      const inputVal = document.getElementById("nameInput").value;
+      document.getElementById("sinkArea").textContent = "Ultimo dato salvato: " + inputVal;
+    });
+  </script>
+</body>
+</html>
diff --git a/tests/test_fixture_contracts.py b/tests/test_fixture_contracts.py
new file mode 100644
index 0000000..562111c
--- /dev/null
+++ b/tests/test_fixture_contracts.py
@@ -0,0 +1,50 @@
+"""Offline structural fixture checks; browser execution is not tested here."""
+from html.parser import HTMLParser
+from pathlib import Path
+import unittest
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+class IdCollector(HTMLParser):
+    def __init__(self):
+        super().__init__()
+        self.ids = set()
+
+    def handle_starttag(self, tag, attrs):
+        props = dict(attrs)
+        if "id" in props:
+            self.ids.add(props["id"])
+
+
+class FixtureContractTests(unittest.TestCase):
+    def test_source_fixture_contains_copy_event_and_local_receiver(self):
+        text = (ROOT / "vittima.html").read_text(encoding="utf-8")
+        self.assertIn("addEventListener('copy'", text)
+        self.assertIn("clipboardData.setData('text/plain'", text)
+        self.assertIn("http://127.0.0.1:5000", text)
+
+    def test_positive_and_negative_controls_have_same_input_output_ids(self):
+        for name in ("crm_scammer_simulato.html", "crm_safe_simulato.html"):
+            parser = IdCollector()
+            parser.feed((ROOT / name).read_text(encoding="utf-8"))
+            self.assertTrue({"nameInput", "sinkArea"} <= parser.ids, name)
+
+    def test_positive_control_intentionally_uses_unsafe_sink(self):
+        text = (ROOT / "crm_scammer_simulato.html").read_text(encoding="utf-8")
+        self.assertIn(".innerHTML =", text)
+
+    def test_negative_control_keeps_input_as_text(self):
+        text = (ROOT / "crm_safe_simulato.html").read_text(encoding="utf-8")
+        self.assertIn(".textContent =", text)
+        self.assertNotIn(".innerHTML", text)
+        self.assertNotIn("document.cookie", text)
+
+    def test_readme_restricts_use_to_authorized_labs(self):
+        text = (ROOT / "README.md").read_text(encoding="utf-8")
+        self.assertIn("explicit ownership and authorization", text)
+        self.assertIn("not a browser exploit", text)
+
+
+if __name__ == "__main__":
+    unittest.main()