diff --git a/src/mnemosyne/gateway.py b/src/mnemosyne/gateway.py
index 20b1fe0..c58bb27 100644
--- a/src/mnemosyne/gateway.py
+++ b/src/mnemosyne/gateway.py
@@ -2183,7 +2183,9 @@ def create_app(
         #     )
 
         # 4b. Apply fidelity-based content replacement
-        _apply_fidelity(payload, session)
+        # DISABLED: L1/L2 stub replacement causes response issues that trigger
+        # rapid retries in opencode. Re-enable once stub format is validated.
+        # _apply_fidelity(payload, session)
 
         # Place cache_control markers at optimal positions
         _place_cache_controls(payload)