feat(frank-medium): cut to MXFP4 checkpoint with unquantized bf16 KV

Swap the serving checkpoint back to
just1moremodel/Qwen3.8-27B-Uncensored-MXFP4-awq (quark/W4A8) and serve it with
KV_DTYPE=auto (unquantized bf16 KV) instead of the hardcoded fp8. fp8 KV
stacked on MXFP4's already-quantized W4A8 weights compounds attention-path
precision loss; clean KV tests whether that was hurting output quality. The
freed MXFP4 weights (19.37 vs 30.9 GB) buy the KV pool back, so the full
262,144 native window fits unquantized - MAXLEN returns to 262144.

The entrypoint gains a KV_DTYPE tunable (default fp8, the historical behavior),
shared across both quantization paths; the quadlet sets auto. Rollback: SNAP
back to the FP8 checkpoint with KV_DTYPE=fp8 and MAXLEN=192000.

dankserver/frank-medium/quadlet/frank-medium.container

@@ -3,19 +3,19 @@
 # Install path on dankserver: ~/.config/containers/systemd/frank-medium.container
 # Unit name: frank-medium.service (container name: frank-medium)
 #
-# The dankserver LLM endpoint (:7770, alias frank-medium) since 2026-09-20:
-# the vllm-radiance stack (stilldeadcode/vllm-radiance:0.9.3 image) serving
-# orcarouter/Qwen3.8-27B-Uncensored-FP8 (FP8 E4M3 block-wise, 128x128,
-# dynamic activation quantization) on the 2x Radeon AI PRO R9700 (gfx1201)
-# as ONE tensor-parallel process (TP=2, R4D one-shot all-reduce) with MTP
-# self-speculation (SPEC=8, the model's own single-layer MTP head).
+# The dankserver LLM endpoint (:7770, alias frank-medium): the vllm-radiance
+# stack (stilldeadcode/vllm-radiance:0.9.3 image) serving
+# just1moremodel/Qwen3.8-27B-Uncensored-MXFP4-awq (MXFP4 / quark, W4A8, 19.37
+# GiB) on the 2x Radeon AI PRO R9700 (gfx1201) as ONE tensor-parallel process
+# (TP=2, R4D one-shot all-reduce) with the z-lab DFlash2 external drafter
+# (SPEC=7) and UNQUANTIZED bf16 KV (KV_DTYPE=auto).
 # The entrypoint is QUANTIZATION-AWARE: it reads the model's weight
 # quantization from config.json and serves the plain FP8 path (no MXFP4
 # patches, --quantization=fp8, ROCM_AITER unified attention) or the MXFP4
 # patch-and-serve path (the DFlash2 drafter). A model swap is now: change
-# SNAP (+ SPEC_METHOD/SPEC), restart. The MXFP4 checkpoint
-# (just1moremodel/Qwen3.8-27B-Uncensored-MXFP4-awq) remains on disk as the
-# rollback target.
+# SNAP (+ SPEC_METHOD/SPEC), restart. The FP8 checkpoint
+# (orcarouter/Qwen3.8-27B-Uncensored-FP8) is the on-disk rollback target — the
+# 2026-09-20 to 2026-09-21 serving shape, before this MXFP4 + clean-KV cut.
 #
 # SHAPE. The launcher the upstream repo ships binds the server with
 # --network=host (vLLM takes --host 0.0.0.0 --port 7770 directly), which is
@@ -65,7 +65,7 @@
 # DO NOT name an environment variable TEMP, HOST or GPU_MAX_HEAP_SIZE: the
 # HIP runtime reads bare TEMP for its JIT cache path (2026-08-13 incident).
 [Unit]
-Description=frank-medium — vllm-radiance FP8 Qwen3.8-27B-Uncensored on 2x R9700 (gfx1201)
+Description=frank-medium — vllm-radiance MXFP4 Qwen3.8-27B-Uncensored on 2x R9700 (gfx1201)
 After=network-online.target
 
 [Container]
@@ -82,15 +82,15 @@ PodmanArgs=--privileged --ipc=host --security-opt seccomp=unconfined --cap-add S
 # memory is not a compute target.
 Environment=ROCR_VISIBLE_DEVICES=0,1
 Environment=HIP_VISIBLE_DEVICES=0,1
-# The FP8 checkpoint carries its own single-layer MTP head (mtp.layers.0),
-# so MTP self-speculation needs no external drafter and no fp8_mtp.py
-# rewrite step. The MXFP4 checkpoint (rollback) ships its fp8 MTP head too.
+# Drafting: the external z-lab DFlash2-FP8 drafter (SPEC_METHOD=dflash). The
+# plain-FP8 checkpoint (rollback) carries its own single-layer MTP head, but
+# DFlash2 beat MTP self-speculation on decode, so the drafter serves either.
 # Chat template: the Qwen-Sharp variant (froggeric v22.4.0) — the terse
 # system prompt (opt out per-request with chat_template_kwargs {"terse":
 # false}), message.reasoning support (vLLM's thinking field), and the
 # tightened tool-call rendering. The predecessor (qwen-fixed-v22.3.jinja in
 # the /patches clone) remains there as the rollback target: flip CHAT_TEMPLATE.
-Environment=SNAP=/models/Qwen3.8-27B-Uncensored-FP8
+Environment=SNAP=/models/Qwen3.8-27B-Uncensored-MXFP4-awq
 Environment=DRAFTER=/models/Qwen3.8-27B-DFlash2-FP8
 Environment=CHAT_TEMPLATE=/templates/qwen-sharp-v22.4.0.jinja
 # Fleet identity: the id at /v1/models and in every response body. Every
@@ -101,7 +101,7 @@ Environment=PORT=7770
 # repo; the R4D one-shot all-reduce kernel serves it natively.
 Environment=TP=2
 # Measured production batch shape (upstream README): MAXSEQS 8 peaks
-# aggregate throughput at 573 t/s; MAXLEN is the model's native context.
+# aggregate throughput at 573 t/s. MAXLEN is the served window (see KV_DTYPE).
 Environment=MAXSEQS=8
 Environment=CHUNK=8192
 Environment=MAXLEN=262144
@@ -128,6 +128,12 @@ Environment=SPEC=7
 # the first healthy start, recalibrate with calibrate-kv.sh to use the extra
 # VRAM on the 34.2 GiB cards.
 Environment=KV_MEM=0
+# KV cache dtype: auto = UNQUANTIZED bf16 KV. The experiment: fp8 KV stacked on
+# MXFP4's already-quantized W4A8 weights compounds attention precision loss, so
+# clean KV should recover output quality. MXFP4's freed weights (19.37 vs 30.9
+# GB) buy the pool back — the full 262,144 native window still fits unquantized
+# (~290k-token f16 pool > 262,144). Flip to fp8 for the measured 943k-token pool.
+Environment=KV_DTYPE=auto
 # Checkpoints (rw: nothing downloads at runtime, but vLLM mmaps the shards;
 # keep parity with the launcher's rw mount).
 Volume=/home/dank/models:/models