fix(dataflows): apply the Alpha Vantage fundamentals look-ahead filter

- the payload is a JSON string, so the dict-only guard skipped filtering and
  future-dated reports leaked into historical runs, breaking the #475 guarantee
- parse before filtering; non-JSON bodies and an unset curr_date pass through #1115

tests/test_alpha_vantage_hardening.py

@@ -1,11 +1,16 @@
 """Alpha Vantage request hardening.
 
-Regressions for #990 (no request timeout -> can hang) and #991 (invalid-key
-responses mislabeled as rate limits and silently treated as transient).
+Regressions for #990 (no request timeout -> can hang), #991 (invalid-key
+responses mislabeled as rate limits and silently treated as transient), and
+#1115 (fundamentals look-ahead filter never ran because the payload is a JSON
+string, not a dict).
 """
+import json
+
 import pytest
 
 import tradingagents.dataflows.alpha_vantage_common as av
+import tradingagents.dataflows.alpha_vantage_fundamentals as avf
 
 
 class _FakeResponse:
@@ -52,3 +57,40 @@ def test_invalid_key_not_mislabeled_as_rate_limit(monkeypatch):
     with pytest.raises(av.AlphaVantageRateLimitError):  # sanity: rate-limit path still distinct
         monkeypatch.setattr(av.requests, "get", _patched_get('{"Note": "API call frequency is 5 calls per minute."}'))
         av._make_api_request("TIME_SERIES_DAILY", {"symbol": "AAPL"})
+
+
+_FUNDAMENTALS_JSON = json.dumps({
+    "symbol": "AAPL",
+    "annualReports": [
+        {"fiscalDateEnding": "2025-12-31", "totalAssets": "1"},   # future -> must drop
+        {"fiscalDateEnding": "2023-12-31", "totalAssets": "2"},   # past   -> must keep
+    ],
+    "quarterlyReports": [
+        {"fiscalDateEnding": "2024-06-30", "totalAssets": "3"},   # future -> must drop
+        {"fiscalDateEnding": "2023-09-30", "totalAssets": "4"},   # past   -> must keep
+    ],
+})
+
+
+@pytest.mark.unit
+def test_fundamentals_look_ahead_filter_runs_on_json_string(monkeypatch):
+    # #1115: the payload arrives as a JSON *string*; the old dict-only guard let
+    # future-dated fiscal periods leak into historical runs.
+    monkeypatch.setattr(avf, "_make_api_request", lambda fn, params: _FUNDAMENTALS_JSON)
+    out = avf.get_balance_sheet("AAPL", curr_date="2024-01-01")
+    assert isinstance(out, str)  # callers still receive a str
+    parsed = json.loads(out)
+    assert [r["fiscalDateEnding"] for r in parsed["annualReports"]] == ["2023-12-31"]
+    assert [r["fiscalDateEnding"] for r in parsed["quarterlyReports"]] == ["2023-09-30"]
+
+
+@pytest.mark.unit
+def test_fundamentals_no_curr_date_passes_through(monkeypatch):
+    monkeypatch.setattr(avf, "_make_api_request", lambda fn, params: _FUNDAMENTALS_JSON)
+    assert avf.get_income_statement("AAPL") == _FUNDAMENTALS_JSON
+
+
+@pytest.mark.unit
+def test_fundamentals_non_json_body_unchanged(monkeypatch):
+    monkeypatch.setattr(avf, "_make_api_request", lambda fn, params: "not-json")
+    assert avf.get_cashflow("AAPL", curr_date="2024-01-01") == "not-json"

tradingagents/dataflows/alpha_vantage_fundamentals.py

@@ -1,21 +1,30 @@
+import json
+
 from .alpha_vantage_common import _make_api_request
 
 
 def _filter_reports_by_date(result, curr_date: str):
-    """Filter annualReports/quarterlyReports to exclude entries after curr_date.
+    """Drop annual/quarterly reports dated after curr_date to prevent look-ahead.
 
-    Prevents look-ahead bias by removing fiscal periods that end after
-    the simulation's current date.
+    ``_make_api_request`` returns the fundamentals payload as a JSON string, so
+    parse, filter, and re-serialize. A non-JSON body or an unset ``curr_date`` is
+    returned unchanged.
     """
-    if not curr_date or not isinstance(result, dict):
+    if not curr_date or not isinstance(result, str):
+        return result
+    try:
+        payload = json.loads(result)
+    except json.JSONDecodeError:
+        return result
+    if not isinstance(payload, dict):
         return result
     for key in ("annualReports", "quarterlyReports"):
-        if key in result:
-            result[key] = [
-                r for r in result[key]
+        if isinstance(payload.get(key), list):
+            payload[key] = [
+                r for r in payload[key]
                 if r.get("fiscalDateEnding", "") <= curr_date
             ]
-    return result
+    return json.dumps(payload)
 
 
 def get_fundamentals(ticker: str, curr_date: str = None) -> str: