diff --git a/api/streaming.py b/api/streaming.py
index d60c4880..8db29e25 100644
--- a/api/streaming.py
+++ b/api/streaming.py
@@ -2770,6 +2770,8 @@ def _run_agent_streaming(
                         'model': _fb_entry.get('model', ''),
                         'provider': _fb_entry.get('provider', ''),
                         'base_url': _fb_entry.get('base_url'),
+                        'api_key': _fb_entry.get('api_key'),
+                        'key_env': _fb_entry.get('key_env'),
                     }
 
             # Build kwargs defensively — guard newer params so the WebUI
diff --git a/tests/test_pr1339_fallback_providers_list.py b/tests/test_pr1339_fallback_providers_list.py
index c180c8dd..c0a804f5 100644
--- a/tests/test_pr1339_fallback_providers_list.py
+++ b/tests/test_pr1339_fallback_providers_list.py
@@ -70,3 +70,21 @@ def test_fallback_resolved_initialized_to_none():
     assert "_fallback_resolved = None" in block, (
         "_fallback_resolved must be initialized to None so callers can rely on its presence"
     )
+
+
+def test_fallback_resolved_preserves_credential_hints():
+    """Fallback entries must keep credential hints for AIAgent fallback activation."""
+    block = _extract_fallback_block()
+    resolved_start = block.find("_fallback_resolved = {")
+    assert resolved_start != -1, "_fallback_resolved dict not found"
+    resolved_end = block.find("}", resolved_start)
+    resolved_dict = block[resolved_start:resolved_end]
+
+    assert "'api_key': _fb_entry.get('api_key')" in resolved_dict, (
+        "WebUI must preserve fallback_model/fallback_providers api_key so "
+        "AIAgent._try_activate_fallback can authenticate the fallback."
+    )
+    assert "'key_env': _fb_entry.get('key_env')" in resolved_dict, (
+        "WebUI must preserve fallback_model/fallback_providers key_env so "
+        "AIAgent._try_activate_fallback can resolve env-backed fallback keys."
+    )