Decode LangCache attribute values on retrieval

Author: abrookins

redisvl/extensions/cache/llm/langcache.py

@@ -23,6 +23,11 @@
 )
 
 
+_LANGCACHE_ATTR_DECODE_TRANS = str.maketrans(
+    {v: k for k, v in _LANGCACHE_ATTR_ENCODE_TRANS.items()}
+)
+
+
 def _encode_attribute_value_for_langcache(value: str) -> str:
     """Encode a string attribute value for use with the LangCache service.
 
@@ -62,6 +67,40 @@ def _encode_attributes_for_langcache(attributes: Dict[str, Any]) -> Dict[str, An
     return safe_attributes if changed else attributes
 
 
+def _decode_attribute_value_from_langcache(value: str) -> str:
+    """Decode a string attribute value returned from the LangCache service.
+
+    This reverses :func:`_encode_attribute_value_for_langcache`, translating the
+    fullwidth comma and division slash characters back to their ASCII
+    counterparts so callers see the original values they stored.
+    """
+
+    return value.translate(_LANGCACHE_ATTR_DECODE_TRANS)
+
+
+def _decode_attributes_from_langcache(attributes: Dict[str, Any]) -> Dict[str, Any]:
+    """Return a copy of *attributes* with string values safely decoded.
+
+    This is the inverse of :func:`_encode_attributes_for_langcache`. Only
+    top-level string values are decoded; non-string values are left unchanged.
+    If no values require decoding, the original dict is returned unchanged.
+    """
+
+    if not attributes:
+        return attributes
+
+    changed = False
+    decoded_attributes: Dict[str, Any] = dict(attributes)
+    for key, value in attributes.items():
+        if isinstance(value, str):
+            decoded = _decode_attribute_value_from_langcache(value)
+            if decoded != value:
+                decoded_attributes[key] = decoded
+                changed = True
+
+    return decoded_attributes if changed else attributes
+
+
 class LangCacheSemanticCache(BaseLLMCache):
     """LLM Cache implementation using the LangCache managed service.
 
@@ -239,7 +278,11 @@ def _convert_to_cache_hit(self, result: Dict[str, Any]) -> CacheHit:
             CacheHit: The converted cache hit.
         """
         # Extract attributes (metadata) from the result
-        attributes = result.get("attributes", {})
+        attributes = result.get("attributes", {}) or {}
+        if attributes:
+            # Decode attribute values that were encoded for LangCache so callers
+            # see the original metadata values they stored.
+            attributes = _decode_attributes_from_langcache(attributes)
 
         # LangCache returns similarity in [0,1] (higher is better)
         similarity = result.get("similarity", 0.0)

tests/integration/test_langcache_semantic_cache_integration.py

@@ -261,7 +261,12 @@ def test_attribute_value_with_comma_and_slash_is_encoded_for_llm_string(
             num_results=3,
         )
         assert hits
+        # Response must match, and metadata should contain the original value
+        # (the client handles encoding/decoding around the LangCache API).
         assert any(hit["response"] == response for hit in hits)
+        assert any(
+            hit.get("metadata", {}).get("llm_string") == raw_llm_string for hit in hits
+        )
 
 
 @pytest.mark.requires_api_keys

tests/unit/test_langcache_semantic_cache.py

@@ -175,6 +175,9 @@ def test_check(self, mock_langcache_client):
             abs(results[0]["vector_distance"] - 0.05) < 0.001
         )  # 1.0 - 0.95 similarity
 
+        # Attributes should round-trip decoded in metadata
+        assert results[0]["metadata"] == {"topic": "programming"}
+
         mock_client.search.assert_called_once()
 
     @pytest.mark.asyncio
@@ -261,7 +264,12 @@ def test_check_with_attributes(self, mock_langcache_client):
             "similarity": 0.95,
             "created_at": 1234567890.0,
             "updated_at": 1234567890.0,
-            "attributes": {"language": "python", "topic": "programming"},
+            # Attributes come back from LangCache already encoded; the client
+            # should decode them before exposing them to callers.
+            "attributes": {
+                "language": "python",
+                "topic": "programming，with∕encoding",
+            },
         }
 
         mock_response = MagicMock()
@@ -275,21 +283,32 @@ def test_check_with_attributes(self, mock_langcache_client):
             api_key="test-key",
         )
 
-        # Search with attributes filter
+        # Search with attributes filter – we pass raw, unencoded values and
+        # expect to see those same values in the returned metadata.
         results = cache.check(
             prompt="What is Python?",
-            attributes={"language": "python", "topic": "programming"},
+            attributes={
+                "language": "python",
+                "topic": "programming,with/encoding",
+            },
         )
 
         assert len(results) == 1
         assert results[0]["entry_id"] == "entry-123"
 
-        # Verify attributes were passed to search
+        # Verify attributes were passed to search (encoded by the client)
         mock_client.search.assert_called_once()
         call_kwargs = mock_client.search.call_args.kwargs
         assert call_kwargs["attributes"] == {
             "language": "python",
-            "topic": "programming",
+            # The comma and slash should be encoded for LangCache.
+            "topic": "programming，with∕encoding",
+        }
+
+        # And the decoded, original values should appear in metadata
+        assert results[0]["metadata"] == {
+            "language": "python",
+            "topic": "programming,with/encoding",
         }
 
         def test_store_with_empty_metadata_does_not_send_attributes(