fix: deduplicate LLM JSON parsing and reuse aiohttp sessions in stock selector

Extract _extract_json_array() to eliminate duplicate JSON parsing logic
between _parse_llm_selections() and LLMCandidateSource._parse_candidates().
Add session reuse in StockSelector via _ensure_session()/close() methods
instead of creating new aiohttp.ClientSession per HTTP call. Pass shared
session to LLMCandidateSource.get_candidates().

1 files changed, 32 insertions, 0 deletions

diff --git a/services/strategy-engine/tests/test_stock_selector.py b/services/strategy-engine/tests/test_stock_selector.py
index ff9d09c..fa15f66 100644
--- a/services/strategy-engine/tests/test_stock_selector.py
+++ b/services/strategy-engine/tests/test_stock_selector.py
@@ -7,6 +7,7 @@ from datetime import datetime, timezone
 from strategy_engine.stock_selector import (
     SentimentCandidateSource,
     StockSelector,
+    _extract_json_array,
     _parse_llm_selections,
 )
 
@@ -60,6 +61,37 @@ def test_parse_llm_selections_with_markdown():
     assert selections[0].symbol == "TSLA"
 
 
+def test_extract_json_array_from_markdown():
+    text = '```json\n[{"symbol": "AAPL", "score": 0.9}]\n```'
+    result = _extract_json_array(text)
+    assert result == [{"symbol": "AAPL", "score": 0.9}]
+
+
+def test_extract_json_array_bare():
+    text = '[{"symbol": "TSLA"}]'
+    result = _extract_json_array(text)
+    assert result == [{"symbol": "TSLA"}]
+
+
+def test_extract_json_array_invalid():
+    assert _extract_json_array("not json") is None
+
+
+def test_extract_json_array_filters_non_dicts():
+    text = '[{"symbol": "AAPL"}, "bad", 42]'
+    result = _extract_json_array(text)
+    assert result == [{"symbol": "AAPL"}]
+
+
+async def test_selector_close():
+    selector = StockSelector(
+        db=MagicMock(), broker=MagicMock(), alpaca=MagicMock(), anthropic_api_key="test"
+    )
+    # No session yet - close should be safe
+    await selector.close()
+    assert selector._http_session is None
+
+
 async def test_selector_blocks_on_risk_off():
     mock_db = MagicMock()
     mock_db.get_latest_market_sentiment = AsyncMock(