large: batch profile flipped to the runner's qualified 2048/512 (fastest measured prefill, no decode change)

scripts/frank-default-large.env

@@ -50,11 +50,12 @@ LISTEN_PORT=52625
 # while the prompt cache is enabled.
 CTX_SIZE=262144
 PARALLEL=1
-# Local override: the pinned runner uses 2048/512; production chat uses a
-# larger 4096/4096 batch (unified memory has headroom; matches the retired
-# v3 profile).
-BATCH_SIZE=4096
-UBATCH_SIZE=4096
+# Batch profile: the pinned runner's qualified sizes (2048/512). Benchmarks
+# on 2026-08-22: ubatch 512 gives the fastest prefill at every depth
+# (524/485/323 t/s at 8k/16k/64k vs 266/258/203 for ubatch 4096) with no
+# decode difference. Do not raise ubatch without re-benching prefill.
+BATCH_SIZE=2048
+UBATCH_SIZE=512
 TARGET_THREADS=16
 BATCH_THREADS=32
 CACHE_TYPE_K=f16