docs(frank-archon): record the bf16 KV shape, its measured cost, and the probe

Runbook section `2026-10-11 — unquantized KV at 2 x 200,000`: the dtype law
(only bf16|fp8, no K/V split; the QSA block key is dtype-fixed, which is why
bf16 costs 1.89x and not 2x), the pool formula that reproduces both live
boots within 0.1%, the seqs-3-to-2 provenance (the tcclaviger fork's
torch.compile constraint, not radiance's), the boot ledger, and the A/B.

The A/B, fp8 control arm through a transient FRANK_ARCHON_ENV_FILE drop-in:
prefill -29% (4,379 -> 3,126 cold), TTFT at the full window +25% (the 2 x 197k
pair: 110.5 s -> 138.1 s), decode inside the +-3% band on two of three passes,
draft acceptance UP 0.661 -> 0.740. The price is prefill, not decode. Open
call for Frank: keep exact KV, or take the cheap fp8 2 x 200k fit (pool 3,648).

Also corrects two stale index entries (w4dn8 said STAGED, fp8-native said
ACTIVE), adds the worklog entry, and commits the verification tool as
scripts/probe-frank-archon-kv.py — it carries the probe law that cost two
false negatives: radiance answers in reasoning_content, so a chat probe with a
small budget reads as empty content + finish_reason stop on a healthy server.
Tests 368/368.

AGENTS.md

@@ -525,41 +525,61 @@ the throughput gate (decode ≥ 30.8 t/s) was passed at 4.5× the bar
 Rollback: revert the swap commit — the fp8-native `.rad`
 (`qwen4exp-fp8-native.rad`) and every prior payload remain on disk.
 
-**Shape (both R9700s, TP=2)**: `--tp-wire wht6`, `--max-num-seqs 3`,
+**Shape (both R9700s, TP=2)**: `--tp-wire wht6`, `--max-num-seqs 2`,
 `--max-model-len 200000` (the harness contextWindow must quote this),
-`--placement expert_tiered --host-pool-mib 40960` + **explicit VRAM
-partition `--vram-weights-mib 26071 --vram-kv-mib 3543`** (the vram-pair
-replaced `--expert-vs-cache-ratio`; the pair sizes the fp8-KV shape at the
-deployed boot), `--kv-cache-dtype fp8` (inherited from the fp8-native
-env), `--num-speculative-tokens 2`,
-`--max-num-batched-tokens 2048`, prefix cache 4 GiB pinned host + 64 GiB
+`--placement expert_tiered --host-pool-mib 44928` + **explicit VRAM
+partition `--vram-weights-mib 22208 --vram-kv-mib 6912`** (the vram-pair
+replaced `--expert-vs-cache-ratio`; the two are ONE budget —
+`weights + kv ≤ 29,120 MiB`, from the measured card 31,856 minus 1,710
+consumed outside both budgets minus 1,024 to keep free), `--kv-cache-dtype`
+**`bf16` — unquantized KV since 2026-10-11**, `--num-speculative-tokens 2`,
+`--max-num-batched-tokens 2048`, prefix cache 8 GiB pinned host + 64 GiB
 disk at `/home/dank/radiance-state`, **`--ngram-placement ram`**, Froggeric
 v22.5 chat template vendored (`scripts/qwen38-froggeric-v22.5.jinja`,
-`--override-chat-template`). Boot ledger: KV pool 3.46 GiB (~480k fp8
-tokens), two expert pools 57.84 GiB, cards settled 1.41 GiB free.
+`--override-chat-template`). Boot ledger: KV pool 6.75 GiB = **462,752 bf16
+tokens, "backs 2 sequences all at 200000 tokens at once"** (the fp8 pool's
+386,904 backed 1.93), weights slab filled to 147 KiB of slack, host pool
+10,375 slots, cards settled 1.85 GiB free.
 
 Shape notes carried from the fp8-native era and unchanged: wht6 gains,
 MNDT 2048 law (2560 collapses decode to 2.6–7.7 t/s), the 64 GiB disk
 prefix cache, and the rule that a prompt over `--max-model-len` is
 refused, never truncated. What changed: the fp8-native era's NVMe expert
 streaming (the 3.5 GB/s wall) is gone — the w4 resident set fits the
-40 GiB pool, so decode ran 122–173 t/s in the campaign arms and ~190 t/s
-on the deployed shape (512-token streamed probe). The campaign also
+host pool, so decode ran 122–173 t/s in the campaign arms and ~190 t/s
+on the fp8 shape (512-token streamed probe). The campaign also
 measured the int8-KV + spec-3 arm (136.0 t/s median at 44.5k depth,
-accept 0.7246); production shipped the fp8-KV + spec-2 pair at cutover —
-the KLD gate scored at the fp8-KV shape, so the gate and the boot agree.
-Disk-tier sizing law: the engine forces ~9.6 GiB of disk-tier weight
+accept 0.7246).
+
+**The bf16 KV law (2026-10-11)**: `--kv-cache-dtype` takes ONLY `bf16|fp8` —
+one dtype for the whole cache, so llama.cpp's exact-K/quantized-V pair (what
+frank-zealot runs) has NO radiance equivalent; the rung under bf16 is fp8 on
+both halves. Measured per rank from the two boot ledgers: `kv_attn` (13
+layers, 4-token blocks) pages 26.00 → 52.00 KiB, while `kv_qsa_bkey` (13
+layers) stays 3.25 KiB at BOTH dtypes (the QSA block key is an index, not
+attention state) — so a token costs 7.3125 KiB at fp8 and 13.8125 KiB at
+bf16: **1.89×, not 2×**. Pool sizing must also pay the dtype-independent terms
+that live in the same pool (~110 MiB a sequence of recurrent state + 448 MiB
+of prefix checkpoints): `(vram_kv − 110·seqs − 448) MiB / 13.8125 KiB` =
+462,946 where the engine reported 462,752 (0.04 % page rounding). The cost is
+paid twice on this engine, and half-refunded: idle KV VRAM is also the expert
+cache's spillover, and the bigger pool *lends* 6.08 GiB to the slab where the
+fp8 pool lent 2.69 GiB. `--max-num-seqs 3 → 2` came with the change (two slots
+× the window is the capacity contract; the "seqs 2 cannot boot" law belongs to
+the retired tcclaviger fork's torch.compile, not radiance) and it also drops
+the fused all-reduce to 2 × 3 = 6 rows, under the 25-row bound where wht6 is
+bit-exact. Disk-tier sizing law: the engine forces ~9.6 GiB of disk-tier weight
 buffers + arena onto the weights side, so `weights + kv` is capped near
 29.6 GiB/card; boot with the pair, never `--kv-cache-size-mib`.
 
-**The pinned-RAM ledger is why this is a root unit**: 2 × 40 GiB expert
+**The pinned-RAM ledger is why this is a root unit**: 2 × 44 GiB expert
 pools + the 47.7 GiB n-gram copy (`--ngram-placement ram` is pinned RAM
-the card reads) + 4 GiB prefix host ≈ **132 GiB** charged against
+the card reads) + 8 GiB prefix host ≈ **147 GiB** charged against
 `RLIMIT_MEMLOCK` — the TTM floor is set just above it.
 `ttm.pages_limit`/`pages_max` cap GPU-mappable pinned pages; the serve
-script's TTM preflight (`FRANK_ARCHON_TTM_MIN_MIB=140000`) refuses to
-start until both knobs are raised in the stop window (sysfs write first,
-kernel cmdline + reboot only if read-only).
+script's TTM preflight (`FRANK_ARCHON_TTM_MIN_MIB=150000`, cap on this host
+204,800) refuses to start until both knobs are raised in the stop window
+(sysfs write first, kernel cmdline + reboot only if read-only).
 
 **Contract facts** (source-verified): the HTTP listener binds AFTER the
 full load, so a bare `curl /health` gate is honest (`/health` == `/ping`,