diff --git a/scripts/frank-default-large.env b/scripts/frank-default-large.env
index 4a8c991..07dee93 100644
--- a/scripts/frank-default-large.env
+++ b/scripts/frank-default-large.env
@@ -39,7 +39,7 @@ CACHE_TYPE_V=q8_0
 # ubatch is the compute-graph driver; larger ubatch = more VRAM, faster prefill.
 # Re-verified 2026-08-14 during the spec swap (see benchmark doc).
 BATCH_SIZE=8192
-UBATCH_SIZE=2048
+UBATCH_SIZE=4096
 # Sampling settings — per HauhauCS Qwen3.6-27B model card.
 # Thinking-general: temp=1.0, top_p=0.95, top_k=20, min_p=0.
 # Clients may override per-request; these are the server-side defaults.