From 9c3673af345cf6c8fbe9100305897eebc0fe36a7 Mon Sep 17 00:00:00 2001
From: Sylvester Kaczmarek
 <16242628+sylvesterkaczmarek@users.noreply.github.com>
Date: Tue, 11 Aug 2026 17:46:29 +0100
Subject: [PATCH] fix(store): avoid mutating published injected layer lists

---
 backend/services/ai_intel_store.py            | 11 ++--
 .../test_ai_intel_store_copy_on_write.py      | 59 +++++++++++++++++++
 2 files changed, 65 insertions(+), 5 deletions(-)
 create mode 100644 backend/tests/test_ai_intel_store_copy_on_write.py

diff --git a/backend/services/ai_intel_store.py b/backend/services/ai_intel_store.py
index 48c19f5..c7fda01 100644
--- a/backend/services/ai_intel_store.py
+++ b/backend/services/ai_intel_store.py
@@ -137,15 +137,16 @@ def inject_layer_data(
         tagged.append(entry)
 
     with _data_lock:
-        existing = latest_data.get(layer)
-        if not isinstance(existing, list):
-            existing = []
+        current = latest_data.get(layer)
+        existing = list(current) if isinstance(current, list) else []
 
         if mode == "replace":
             existing = [e for e in existing if not e.get("_injected")]
 
-        existing.extend(tagged)
-        latest_data[layer] = existing
+        # Readers can hold references to published layer lists after releasing
+        # _data_lock. Build a fresh list and swap it atomically rather than
+        # mutating the published object in place with list.extend().
+        latest_data[layer] = [*existing, *tagged]
 
     bump_data_version()
 
diff --git a/backend/tests/test_ai_intel_store_copy_on_write.py b/backend/tests/test_ai_intel_store_copy_on_write.py
new file mode 100644
index 0000000..8c828e6
--- /dev/null
+++ b/backend/tests/test_ai_intel_store_copy_on_write.py
@@ -0,0 +1,59 @@
+"""Regression coverage for copy-on-write OpenClaw layer injection."""
+
+from services import ai_intel_store
+from services.fetchers import _store
+
+
+def _publish_test_layer(monkeypatch, items):
+    published = list(items)
+    monkeypatch.setitem(_store.latest_data, "air_quality", published)
+    monkeypatch.setattr(_store, "bump_data_version", lambda: None)
+    return published
+
+
+def test_append_does_not_mutate_previously_published_list(monkeypatch):
+    before = _publish_test_layer(monkeypatch, [{"id": "existing"}])
+
+    result = ai_intel_store.inject_layer_data(
+        "air_quality",
+        [{"id": "injected"}],
+        mode="append",
+    )
+
+    after = _store.latest_data["air_quality"]
+    assert result == {
+        "ok": True,
+        "layer": "air_quality",
+        "injected": 1,
+        "mode": "append",
+    }
+    assert after is not before
+    assert before == [{"id": "existing"}]
+    assert [item["id"] for item in after] == ["existing", "injected"]
+    assert after[-1]["_injected"] is True
+    assert after[-1]["_source"] == "user:openclaw"
+
+
+def test_replace_does_not_mutate_previously_published_list(monkeypatch):
+    before = _publish_test_layer(
+        monkeypatch,
+        [
+            {"id": "native"},
+            {"id": "old-injected", "_injected": True},
+        ],
+    )
+
+    result = ai_intel_store.inject_layer_data(
+        "air_quality",
+        [{"id": "new-injected"}],
+        mode="replace",
+    )
+
+    after = _store.latest_data["air_quality"]
+    assert result["ok"] is True
+    assert after is not before
+    assert before == [
+        {"id": "native"},
+        {"id": "old-injected", "_injected": True},
+    ]
+    assert [item["id"] for item in after] == ["native", "new-injected"]