fix(data): respect the configured vendor chain and log vendor failures

The router silently extended every request to all available vendors regardless
of config, so an explicit single-vendor choice still fell back to others and
returned data from an unexpected source (#988, #289), and serious primary-vendor
errors were swallowed without a trace (#989). The configured vendor list is now
the exact chain (list several for ordered fallback; "default" uses all), unknown
vendors raise, and swallowed vendor errors are logged. Adds an autouse config
isolation fixture so vendor config can't leak between tests.

tradingagents/dataflows/interface.py

@@ -1,3 +1,4 @@
+import logging
 from typing import Annotated
 
 # Import from vendor-specific modules
@@ -28,6 +29,8 @@ from .symbol_utils import NoMarketDataError
 # Configuration and routing logic
 from .config import get_config
 
+logger = logging.getLogger(__name__)
+
 # Tools organized by category
 TOOLS_CATEGORIES = {
     "core_stock_apis": {
@@ -141,34 +144,43 @@ def route_to_vendor(method: str, *args, **kwargs):
     if method not in VENDOR_METHODS:
         raise ValueError(f"Method '{method}' not supported")
 
-    # Build fallback chain: primary vendors first, then remaining available vendors
     all_available_vendors = list(VENDOR_METHODS[method].keys())
-    fallback_vendors = primary_vendors.copy()
-    for vendor in all_available_vendors:
-        if vendor not in fallback_vendors:
-            fallback_vendors.append(vendor)
+
+    # The configured vendor list IS the chain: we do NOT silently fall back to
+    # vendors the user did not choose (#988/#289) — that returned data from an
+    # unexpected source and caused cross-vendor inconsistencies. For multi-vendor
+    # fallback, list them in order, e.g. data_vendors="yfinance,alpha_vantage".
+    # The "default" sentinel (no explicit config) uses all available vendors.
+    explicit = [v for v in primary_vendors if v and v != "default"]
+    if explicit:
+        vendor_chain = [v for v in explicit if v in VENDOR_METHODS[method]]
+        if not vendor_chain:
+            raise ValueError(
+                f"Configured vendor(s) {explicit} not available for '{method}'. "
+                f"Available: {all_available_vendors}."
+            )
+    else:
+        vendor_chain = all_available_vendors
 
     last_no_data: NoMarketDataError | None = None
     first_error: Exception | None = None
-    for vendor in fallback_vendors:
-        if vendor not in VENDOR_METHODS[method]:
-            continue
-
+    for vendor in vendor_chain:
         vendor_impl = VENDOR_METHODS[method][vendor]
         impl_func = vendor_impl[0] if isinstance(vendor_impl, list) else vendor_impl
 
         try:
             return impl_func(*args, **kwargs)
         except AlphaVantageRateLimitError:
-            continue  # Rate limits: try the next vendor
+            logger.warning("Vendor %r rate-limited for %s; trying next vendor.", vendor, method)
+            continue
         except NoMarketDataError as e:
-            last_no_data = e  # No data here; another vendor may have it
+            last_no_data = e  # No data here; another configured vendor may have it
             continue
         except Exception as e:
-            # A fallback vendor failing for an incidental reason (e.g. no API
-            # key configured) must not crash the call when another vendor
-            # already determined the symbol simply has no data. Remember the
-            # first error so a genuine primary-vendor failure still surfaces.
+            # Don't let one vendor's failure crash the call when another can
+            # serve it, but never swallow silently: a broken primary must be
+            # visible in the logs (#989), not hidden behind a fallback's verdict.
+            logger.warning("Vendor %r failed for %s: %s", vendor, method, e)
             if first_error is None:
                 first_error = e
             continue
@@ -178,6 +190,13 @@ def route_to_vendor(method: str, *args, **kwargs):
     # empty string, so the agent reports "unavailable" instead of inventing a
     # value. This takes precedence over incidental fallback errors.
     if last_no_data is not None:
+        if first_error is not None:
+            # A vendor also hit a real error; surface it in logs so the no-data
+            # verdict can't hide a broken primary (network/auth/etc.).
+            logger.warning(
+                "Returning NO_DATA for %s, but a vendor errored earlier: %s",
+                method, first_error,
+            )
         sym = last_no_data.symbol
         canonical = last_no_data.canonical
         resolved = "" if canonical == sym else f" (resolved to '{canonical}')"

tradingagents/default_config.py

@@ -97,7 +97,10 @@ DEFAULT_CONFIG = _apply_env_overrides({
         "oil commodities supply chain energy",
     ],
     # Data vendor configuration
-    # Category-level configuration (default for all tools in category)
+    # Category-level configuration (default for all tools in category).
+    # The configured value is the exact vendor chain — requests are NOT silently
+    # routed to vendors you didn't choose. For ordered fallback, list several,
+    # e.g. "yfinance,alpha_vantage". "default" uses all available vendors.
     "data_vendors": {
         "core_stock_apis": "yfinance",       # Options: alpha_vantage, yfinance
         "technical_indicators": "yfinance",  # Options: alpha_vantage, yfinance