docs(probe): price the corpus chars/token ratio at run time

The stored 3.28 chars/token (measured 2026-10-11) had drifted to 3.20 as the
repo's docs grew, so leg B sent ~201,900-token prompts and took a legitimate
400 from the engine's own window check — which reads as a capacity-contract
failure on a healthy endpoint. One ~4k-token request now prices the ratio, and
the leg sizes to 97 % of the deployed window.

scripts/frank-archon.env

@@ -46,31 +46,35 @@ FRANK_ARCHON_TP=2
 # stays EXACT for single-sequence decode and any step of <= 25 rows — see
 # MAX_SEQS x (1 + SPEC_TOKENS) below.
 FRANK_ARCHON_TP_WIRE=wht6
-# Decode slots. A slot costs KV, never decode; the pool is sized to this
-# contract and nothing more. At 1.8.1 the budget resolver caps the cache at
-# 556,348 fp8 tokens — 2.8 sessions at 200,000 — so a THIRD full-height
-# conversation answers 400 while /health and every shorter chat work fine
-# (3 x 50k streams run at 77.6 t/s aggregate). Frank's trade: declare the two
-# slots the engine can hold and let the freed ~1.1 GiB go to the expert plane,
-# instead of advertising a third slot that only exists at shorter prompts.
-FRANK_ARCHON_MAX_SEQS=2
+# Decode slots. A slot costs KV and pinned RAM, never decode: the cache target is
+# exactly MAX_SEQS x MAX_MODEL_LEN and the checkpoint store asks (1 + what the
+# retention policy keeps) per slot. Ordered 2026-10-20: FOUR slots over a pool of at
+# least 700,000 fp8 tokens, rounding UP if the resolver cannot land it exactly. The
+# target is therefore 4 x 200,000 = 800,000 tokens and HOST_POOL_MIB decides whether
+# the cache gets it (expert_vram_floor, core/place/planner.cpp:100-104: the card must
+# keep expert-plane-minus-host-room). The 2-slot shape was the answer to a
+# 365,204-token pool that backed 1.8 full-height sessions; at this pool the third and
+# fourth conversations are backed by the cache instead of over-committing it.
+FRANK_ARCHON_MAX_SEQS=4
 # Served window. The engine treats `kv group tokens >= max-model-len` as a HARD
 # limit, and models.yml contextWindow MUST quote this number (over-length is a
 # refusal, not a truncation). The pool is sized for seqs x maxlen, not one
 # sequence.
 FRANK_ARCHON_MAX_MODEL_LEN=200000
 FRANK_ARCHON_PLACEMENT=expert_tiered
-# Pinned host pool for expert rows that do not fit VRAM. Under the budget
-# resolver this is ALSO the lever that decides which experts stay on the card:
-# the card's leftover goes to the expert plane first and the KV cache takes the
-# rest, so growing the pool moves experts off the card and shrinking it spills
-# them onto VRAM the cache wanted. Under-sizing it is a boot failure (36,864
-# refused a boot). The ledger's coverage line is the referee, not this file.
-# Measured, not guessed: 45,568 (PR #30) moved host_pool to 45.09 GiB and left
-# vram_kv byte-identical at 4.20 GiB / 556,348 tokens on both ranks — extra
-# host RAM above what the expert plane's footprint needs buys no cache. Back at
-# 44,928, the size that boots clean.
-FRANK_ARCHON_HOST_POOL_MIB=44928
+# Pinned host pool for expert rows that do not fit VRAM, PINNED ONCE PER RANK: the
+# host must pin tp x this number, and the refusal that names it is
+# core/engine_bringup.cpp:250-265. Under the budget resolver this is ALSO the KV
+# lever -- the card keeps expert-plane-minus-this-room, so every MiB added moves one
+# MiB of experts off the card and into the cache. Derived from the boot ledger (a
+# 23.73 GiB floor at 44,928 room puts plane + 2 units at 67.60 GiB a rank), 49,152
+# drops the floor to 19.6 GiB and leaves the cache ~6.9 GiB, which is enough to back
+# the whole 4 x 200,000 target; the leftover returns to the experts. Cost is paid
+# twice over: pinned RAM (tp x 48 GiB, against the TTM target below) and expert
+# residency -- ~3.2 GiB a card of experts now lives in host RAM and is read over the
+# x8 link when the router picks it. The ledger's coverage line is the referee, not
+# this file: if vram_kv comes back under 700,000 tokens, raise this 1024 and redeploy.
+FRANK_ARCHON_HOST_POOL_MIB=49152
 # VRAM left unclaimed per card (publisher default 96 MiB); the engine's settle
 # floor is built from it.
 FRANK_ARCHON_GPU_HEADROOM_MIB=96
@@ -93,16 +97,29 @@ FRANK_ARCHON_SPEC_TOKENS=2
 FRANK_ARCHON_MAX_BATCHED_TOKENS=2048
 # Step sharing. A prefill chunk that shares a step with decoding sequences holds
 # the device for the chunk's whole time, and every decode row in that step waits
-# that long for its next token (the census: [[LLM Performance Diagnosis]] §9).
-# `auto` leaves each decode row behind the chunk a row plus its draft window and
-# keeps a share for whatever is waiting to be admitted; a number pins the chunk's
-# cap; `off` is the pre-1.4 behaviour this endpoint ran for two eras, where the
-# chunk took the step and admission never ran. Interleave inserts N decode-only
-# steps after a chunk step taken beside decoders: it protects their cadence and
-# holds a waiting request out of those steps, so it stays 0 until the post-migration
-# decode-vs-prefill buckets say it is wanted.
+# that long for its next token: measured at this shape, decode-only steps 15.5 ms
+# against chunk steps 166 ms, which is the harness's ~146 t/s falling to ~11 t/s
+# while another session prefills (law and census: [[frank-archon]]).
+# `auto` is a PREFILL-SPEED dial, not a decoder dial: it reserves one row plus the
+# draft window per decoding sequence (3 tokens) and an eighth of the budget per
+# waiting request or waiting prefill, and the source states it will not halve for
+# decode rows alone. Live proof: prefill_chunks_capped 5,018 across 62,386 chunk
+# steps. A number is the only value that applies whenever the chunk shares a step,
+# and it must not go under the prefill stager's smallest pass -- 1025 rows here,
+# named on the boot line "prefill staging: ... a step of more than 1024 tokens" --
+# because below it every routed layer reads its pooled experts synchronously, so
+# 512 is a trap and the vendor measures the whole job slower there. Interleave
+# inserts N decode-only steps after a chunk step taken beside decoders: it protects
+# their cadence and holds a waiting request out of those steps. That is the decoder
+# dial. ARMED at 1 on 2026-10-20: at N=1 a stream takes its token from the chunk step
+# AND one from the held step, ~2 tokens per 182 ms instead of one per 166 ms; the
+# price falls on the prefilling prompt (its chunks lose every held step) and on any
+# request still waiting to enter. `--prefill-span` re-funds a prefill only when it is
+# ALONE, so it cannot buy this back while decoders run. Meter:
+# radiance:engine_steps_held_total must leave zero, and the §9 buckets must move
+# before N rises.
 FRANK_ARCHON_BUSY_PREFILL_CHUNK=auto
-FRANK_ARCHON_PREFILL_INTERLEAVE=0
+FRANK_ARCHON_PREFILL_INTERLEAVE=1
 # Prefix cache: pinned host memory only. The disk tier was removed outright
 # (--prefix-cache-dir and --prefix-cache-disk-mib are refusals), so what used to
 # be restored from NVMe is now re-prefilled. The tier is sized in ENTRIES and one
@@ -118,9 +135,10 @@ FRANK_ARCHON_NGRAM_PLACEMENT=ram
 # RESETS pages_limit to half of RAM on every boot; below the plan the load dies
 # mid-pin with an anonymous allocator error. ttm-preflight.sh raises the knob
 # itself before refusing by name, so recovery is a boot, not a visit.
-# Floor = 2 x HOST_POOL + 48,824 (static weights + arena) + PREFIX_CACHE + MNBT
-# per the bats ledger test; at the 44,928 pool that computes to 148,920 MiB.
-FRANK_ARCHON_TTM_MIN_MIB=150000
+# Floor = 2 x HOST_POOL + 48,824 (static weights + arena) + PREFIX_CACHE + MNBT + the
+# auto checkpoint store (MAX_SEQS x 10 slots of 111.98 MiB), per the bats ledger test;
+# at the 49,152 pool with 4 slots that computes to 161,848 MiB.
+FRANK_ARCHON_TTM_MIN_MIB=162000
 FRANK_ARCHON_TTM_TARGET_MIB=204800
 # Escape hatch for experiments. Unset -> no extra argv; the serve script expands
 # this unquoted on purpose, so keep multi-flag values as one string.

scripts/probe-frank-archon-kv.py

@@ -147,10 +147,21 @@ def main():
     deep = corpus(160_000)
     wide = corpus(1_100_000)
 
-    # 3.28 chars/token is the measured ratio of this corpus through the
-    # froggeric template (646,000 chars -> 196,919 tokens at the 2026-10-11
-    # deploy); 98.5 % of the window leaves the response room under the ceiling.
-    chars = int(0.985 * maxlen * 3.28)
+    # The corpus's chars/token ratio is MEASURED here, not stored. A stored 3.28
+    # (646,000 chars -> 196,919 tokens, 2026-10-11) had drifted to 3.20 by
+    # 2026-10-20 (646,299 chars -> 201,876 tokens) as the repo's docs grew, and a
+    # stale constant sends leg B past --max-model-len, where the engine answers a
+    # perfectly legitimate 400 ("the request (201900 tokens) exceeds the available
+    # context size (200000)") and the leg reads as a capacity failure. One small
+    # request prices the ratio; 97 % of the window leaves the response room.
+    sample = prompt(wide, 4000, "CAL", "cal-marker")
+    cal, _, _ = post({"model": MODEL,
+                      "messages": [{"role": "user", "content": sample}],
+                      "max_tokens": 1, "temperature": 0.0,
+                      "chat_template_kwargs": {"enable_thinking": False}})
+    ratio = len(sample) / cal["usage"]["prompt_tokens"]
+    print(f"[cal] corpus ratio {ratio:.2f} chars/token")
+    chars = int(0.97 * maxlen * ratio)
     # Each marker's FIRST hyphen-separated word is unique, because show()
     # scores the hit on that word — a shared prefix would score every slot HIT
     # on any answer that says the word.
@@ -176,7 +187,7 @@ def main():
                 print(f"[B-{s}] FAILED after {time.time() - t0:.1f}s: {e!r}")
     print(f"[B] total {time.time() - t0:.1f}s")
     # D — concurrency decode: seqs streams, 512 tokens each, ~25 % depth.
-    dchars = int(0.25 * maxlen * 3.28)
+    dchars = int(0.25 * maxlen * ratio)
     dbodies = [chat(deep, dchars, f"D{i + 1}-9137", f"flint-marker-{i}", 512)
                for i in range(seqs)]
     print(f"[D] {seqs} concurrent streams x 512 tokens, "

scripts/serve-frank-archon.sh

@@ -15,18 +15,21 @@
 # log states every budget before anything is allocated (weights vs KV
 # split, the expert host pool's coverage of the worst case, the PLE pin,
 # the P2P answer per pair) — read it after every resize.
-# Deployed shape (2026-10-19, radiance 1.8.1): THREE decode slots x 200,000
-# tokens, fp8 KV, 44 GiB/rank pinned expert pool, MTP depth 2, prefix cache in
-# pinned host RAM, PLE pinned in RAM. The per-card split between the expert slab
-# and the KV pool is NO LONGER an operator number — 1.3.0 removed the VRAM pair
-# and the budget resolver derives it from headroom, the cache bound and the host
-# pool, so the slab size and the pool's token count are LEDGER lines: after every
-# boot read them out of the log and check the pool still backs 3 x 200,000.
+# Deployed shape (2026-10-20, radiance 1.8.1): FOUR decode slots x 200,000 tokens over a
+# >= 700,000-token fp8 KV pool, 48 GiB/rank pinned expert pool, MTP depth 2, prefix cache
+# in pinned host RAM, PLE pinned in RAM. The per-card split between the expert slab and the KV
+# pool is NO LONGER an operator number — 1.3.0 removed the VRAM pair and the budget
+# resolver derives it from headroom, the cache bound and the host pool, so the slab
+# size and the pool's token count are LEDGER lines. After every boot read them, plus
+# the two lines that size a prefill step — "activation arena: ... lends ... while
+# steps are at most N tokens" (the arena levels the expert slab borrows) and
+# "prefill staging: ... a step of more than N tokens ..." (the chunk size below which
+# pooled experts are read synchronously) — and the cache's session backing.
 #
 # The root unit (scripts/frank-archon.service, User=dank,
-# LimitMEMLOCK=infinity) grants the pin budget: 2 x 44 GiB expert pools +
-# the 47.7 GiB PLE table + 8 GiB prefix host tier — ~147 GiB of pinned
-# pages, which is ALSO why this script refuses to start when ttm's
+# LimitMEMLOCK=infinity) grants the pin budget: 2 x 48 GiB expert pools + the 47.7 GiB PLE
+# table + 8 GiB prefix host tier + the checkpoint store (slots x 112 MiB) — ~159 GiB of
+# pinned pages, which is ALSO why this script refuses to start when ttm's
 # pages_limit/pages_max cap is under FRANK_ARCHON_TTM_MIN_MIB (see below).
 set -euo pipefail
 

serverAppConfigs-docs/LLM/LLM Performance Diagnosis.md

@@ -239,45 +239,92 @@ prefill is over. `preemptions` separates the third shape: a preempted-and-recomp
 sequence stops producing entirely and then re-prefills from token 0, which is a
 stall, not sludge.
 
-Knobs, in the order worth trying them (radiance GUIDE §4.5):
+**Split the step ledger before choosing a knob.** Three counters decide which mechanism you are
+looking at, and none is a rate: `engine_step_seconds_decode_total / engine_steps_decode_total` is
+the mean **decode-only** step, and `(step_seconds_total − step_seconds_decode_total) /
+(steps_total − steps_decode_total)` is the mean **chunk step** (a chunk alone, or a chunk with
+decode rows beside it). On frank-archon's live 1.8.1 shape that pair is **15.5 ms against 166 ms**,
+with 4.7 % of the steps holding 34 % of the step time. Decode-only steps themselves move only
+14.1 → 16.4 ms between a prefill-free minute and a heavy one, and the lagged buckets stay flat: so
+a decode-rate collapse on that box is **step time sharing**, and the eviction/residency story is
+worth ~10 % of one step — not a lever.
 
-- `--prefill-interleave N` — after a chunk step taken beside decoders, the next N
-  steps carry decode rows only and admit nothing. Decoders keep their cadence; the
-  prompt pays that in TTFT. Counts as `engine_steps_held_total`.
-- `--busy-prefill-chunk MODE` — the chunk's share of a step that has other work:
-  `auto` (default) reserves a row plus the draft window per decode row behind it and
-  an eighth of the budget per waiting prefill/request, `off` lets the chunk take the
-  whole step (admission never runs while it does), `N` pins the share. Never under
-  the prefill stager's smallest pass — the startup line names it, and below it every
-  routed layer reads its pooled experts synchronously, which costs the prefill far
-  more than sharing saves. Counts as `engine_prefill_chunks_capped_total`.
-- `--max-num-batched-tokens` — the blunt rung, and the only one older pins have. The vendor's own
-  curve prices **halving the shared chunk at roughly a fifth of prefill throughput** (a 48-layer MoE
-  at 200k on two cards — knob pricing, not this endpoint's number, so treat it as the order of
-  magnitude a chunk decision costs). Raising it past the checkpoint interval buys nothing and loses
-  expert residency to the arena.
-- `--prefill-span N` — the inverse trade: a *lone* prefill carries N intervals a step while every
-  shared step is planned at a smaller shared budget, which on an expert-tiered box lends that arena
-  back to the expert slab. The vendor's own measurement says the win is **long-prompt-only**: nothing
-  at short prompts, a large TTFT gain at the far end of the window.
+**Four traps in the PromQL above.** Learn them before trusting a bucket:
+- **Latency is `vllm:`, cadence is `radiance:`.** The TTFT / inter-token / per-output-token / e2e
+  histograms and the running/waiting gauges exist only under the vLLM compatibility prefix; preemption
+  is `vllm:num_preemptions_total` (the counter) while `radiance:num_requests_preempted` is the
+  *instant* depth. A `radiance:`-only query finds no latency and no preemption, and reads as "the
+  endpoint never stalls anyone".
+- **The tps gauges are 1 s decayed windows, batch-pooled.** Per-stream rate is
+  `decode_tokens_per_second / vllm:num_requests_running`. With a 15 s scrape, a 120 s step samples one
+  scrape in eight — use step ≤ 30 s for a bucket table.
+- **Every counter resets at a restart and the metric set changes with the build.** Prove the window is
+  one shape (`up`, or the first sample of a counter that only the current build exports) before
+  ranking buckets; frank-archon's 48 h window straddled two containers, and one bucket's "collapse"
+  turned out to belong entirely to the older one.
+- **A 2-minute mean step time dilutes the chunk.** The sharp variable is the phase ratio in the query
+  above, never `step_seconds/steps` — 4.7 % of steps cannot move a mean that is 95 % decode.
 
-Two traps. **The arena/slab coupling makes a shared step doubly expensive on an
-expert-tiered shape**: the full-plan arena takes VRAM the resident expert slab would have had, so the
-decode rows inside that step also read experts over the link — a smaller shared budget helps twice.
-And **re-check
-`prefix_hit_rate` / `prefix_evictions` after any chunk change**: the arena and the KV
-pool are the same memory, and the failure looks like turn two taking as long as turn
-one.
+Three instruments the PromQL above cannot reach:
 
-Availability is a version question, not a config question: `--busy-prefill-chunk` and
-`--prefill-interleave` are absent from older pins — prove it on the running container
-(`podman exec <c> <binary> --help | grep -iE "prefill|chunk"`), never from the vendored
-tree, and check the source clone's depth before dating a flag from `git log -S`
-(a `--depth 1` clone reports its own tip for every search).
+- **The engine's own step-detail histograms (`prefill_steps_duration`, `prefill_step_tokens`,
+  `token_queue_wait`) are exported but reach no target**, and the arena / expert slab / heat engine /
+  prefill stager have **no metric at all**. Per-request forensics mean `curl localhost:7770/stats` on
+  the endpoint's own host — same phase counters plus `preemptions` (the count), the chunk geometry,
+  and the expert/link byte totals. `/diagnostics` answers "is the *box* the limit" in one call:
+  configuration drift, the VRAM split, each card's link chain and clocks, findings with fixes.
+- **`prefix_hit_cut_tokens_total` measures prefill load you created for yourself.** On a hybrid
+  (linear + paged) model a prefix hit reuses only as far as the last **linear-state** checkpoint, so
+  cached tokens are replayed as prefill and stall decoders for it; frank-archon ran 38 % of all its
+  prefill tokens that way, every `prefix_hit_cuts_total` labelled `reason="no_snapshot"`. A high
+  prefill rate is not always a client that sends new tokens. Retention is `--checkpoint-policy` -
+  exactly three names, `geometric-backoff` (default), `tip-only`, `keep-all`, one owner:
+  [[frank-archon]].
+- **Bucket the arriving request too** — `histogram_quantile` over
+  `vllm:time_to_first_token_seconds_bucket` by the same prefill series. The decode gauge only sees
+  sequences that are already running; the one waiting for its first token pays the same steps and
+  shows in no decode number.
 
-Run on: [[frank-archon]] — the census was taken on its 3-slot radiance 1.0.13 era (budget 2048 =
-interval 2048); the live 1.8.1 shape carries the two chunk knobs. The measured census and the verdict
-for this fleet's shape are that page's.
+Knobs, in the order worth trying them (radiance GUIDE §4.5; the pinned source is the referee):
+
+- `--prefill-interleave N` — after a chunk step taken beside decoders, the next N steps carry decode
+  rows only and admit nothing. **The knob that acts on the measured mechanism.** Decoders keep their
+  cadence; the prefilling prompt pays in TTFT and an arriving request waits out the held steps.
+  Counts as `engine_steps_held_total` — if that counter is zero, nothing is protecting anyone.
+- `--busy-prefill-chunk N` — pins a shared chunk's share of the step. **`auto` is a prefill-speed
+  setting, not decoder protection:** it reserves `1 + spec` rows per decoding sequence plus an eighth
+  of the budget per *waiting* request or prefill, and the source refuses to halve for "decode rows
+  alone", so a shape can run `auto` and still lose every chunk step. Prove engagement from
+  `engine_prefill_chunks_capped_total` against the chunk-step count. The floor is the prefill
+  stager's smallest pass — the largest arena level that lends, plus one, named on the startup line
+  `prefill staging: … a step of more than N tokens copies the pooled experts of …` — and under it
+  every routed layer reads its pooled experts synchronously: the vendor prices the whole job (four
+  decoders plus a long prompt) at **29.5 s with a 2048 chunk and 31.9 s at 512**, so shrinking the
+  chunk blindly buys latency in both directions.
+- `--prefill-span N` — needs `--max-num-batched-tokens` of N intervals. A *lone* prefill then
+  carries N intervals a step (on an expert-tiered box only from 8 intervals, where the vendor's own
+  measurement says a span starts to win), while **every other step is planned at the shared
+  budget** — a lending arena level that also keeps the stager's ring, the one combination the chunk
+  knob cannot express. Priced by the vendor at 320 MiB a card of expert residency, ~3 % off the KV
+  pool, and TTFT-neutral on one of his two 2×R9700 boxes: measure your own prompt lengths first.
+- `--max-num-batched-tokens` alone — the blunt rung, and the only one older pins have. It raises the
+  arena the expert slab loses, and on this payload its resonance is violent (MNBT 2560 collapses
+  decode — [[frank-archon]]).
+
+Two traps. **The arena/slab coupling makes a shared step expensive twice:** the full-plan arena is
+reclaimed from the expert slab *synchronously before the step*, and the loan regrows only after a
+quiet interval, so every step of a prefill run — the decode-only ones included — runs on the smaller
+slab. And **re-check `prefix_hit_rate` / `prefix_evictions` after any chunk or span change**: the
+arena, the staging ring and the KV pool are the same memory, and the failure looks like turn two
+taking exactly as long as turn one.
+
+Availability is a version question, not a config question: `--busy-prefill-chunk`,
+`--prefill-interleave` and `--prefill-span` are absent from older pins — prove it on the running
+container (`podman exec <c> <binary> --help | grep -iE "prefill|chunk"`) or from `/diagnostics`'s
+`configuration` block, never from a vendored tree, and check a source clone's depth before dating a
+flag from `git log -S` (a `--depth 1` clone reports its own tip for every search).
+
+Run on: [[frank-archon]] — owner of the live census, the measured step pair, and the arms.
 
 ## Related
 

serverAppConfigs-docs/LLM/frank-archon.md

@@ -88,25 +88,30 @@ on stop. Boot budget 1800 s (the publisher's compose allows a 15-minute `start_p
 | Knob (env name, `FRANK_ARCHON_` dropped) | Live value |
 |---|---|
 | TP / wire | `TP=2`, `TP_WIRE=wht6` — libr4d one-shot all-reduce, not RCCL; `min-kb` stays the engine default |
-| Slots / window | `MAX_SEQS=2`, `MAX_MODEL_LEN=200000` (native 262,144; longer is refused, never truncated) — this pair is the **cache bound**, not a KV allocation |
+| Slots / window | `MAX_SEQS=4`, `MAX_MODEL_LEN=200000` (native 262,144; longer is refused, never truncated) — this pair is the **cache bound**: the resolver sizes the KV carve against `slots × window`, and no slot count funds itself (Laws) |
 | KV dtype | `KV_DTYPE=fp8` — the only dtype that funds the slot count (Laws) |
 | VRAM split | **derived at boot** from `GPU_HEADROOM_MIB=96` + the cache bound + `HOST_POOL_MIB`; naming `VRAM_WEIGHTS_MIB`/`VRAM_KV_MIB` is a boot refusal (removed at 1.3.0) |
-| Expert tier | `PLACEMENT=expert_tiered`, `HOST_POOL_MIB=44928` **per rank** |
+| Expert tier | `PLACEMENT=expert_tiered`, `HOST_POOL_MIB=49152` **per rank** — the pinned host pool is also the **KV lever**: the expert floor is `plane + 2 units − host room`, so every MiB pinned there lowers what the experts claim on the card one-for-one and the cache takes it (Laws) |
 | PLE | `NGRAM_PLACEMENT=ram` (47.7 GiB pinned; refuses boot on a short memlock) |
 | Spec / batch | `SPEC_TOKENS=2` — MTP depth 2, the `.rad` carries the model's own `mtp.*` head (`mtp.fc_hidden`/`fc_embedding`/`draft_head`); `MAX_BATCHED_TOKENS=2048` (MNBT — 2560 collapses decode, Laws) |
 | Prefix cache | `PREFIX_CACHE_MIB=8192`, pinned **host tier only** — the 64 GiB disk tier is gone, so an evicted prefix is re-prefilled; `STATE_DIR=/home/dank/radiance-state` now exists only to hold the rad-tune cache |
 | Template | `TEMPLATE=scripts/qwen38-froggeric-v22.5.jinja` (28,234 B) via `--override-chat-template` — froggeric's fixed Qwen3.8 template (the repo root's `chat_template.jinja`, vendored); the checkpoint's own template is baked into the `.rad` by rad-convert and this overrides it, and radiance derives the reasoning and tool-call reply format from it |
-| Step sharing | `BUSY_PREFILL_CHUNK=auto` (a shared chunk reserves a row plus the draft window per waiting decoder) · `PREFILL_INTERLEAVE=0` — held at zero until the decode-vs-prefill buckets ask for it |
-| TTM gate | `TTM_MIN_MIB=150000`, `TTM_TARGET_MIB=204800` |
+| Step sharing | `BUSY_PREFILL_CHUNK=auto` — prefill-speed first: it reserves 3 tokens per waiting decoder and ⅛ of the budget per waiting request, and does **not** shrink the chunk for decoders alone · `PREFILL_INTERLEAVE=1` — the decoder dial, **armed 2026-10-20**: one decode-only step after each chunk step taken beside decoders; meter `engine_steps_held_total`, price is the prefilling prompt's TTFT |
+| TTM gate | `TTM_MIN_MIB=162000`, `TTM_TARGET_MIB=204800` |
 | Boot | `RAD_MIN_MIB=110000` deployer floor; the listener binds only after the full load (health ~100 s, budget 1800 s) |
 
-Boot ledger for the live shape (2026-10-19 11:10, pin 1.8.1, `MAX_SEQS=2`, `HOST_POOL_MIB=44928`):
-the resolver prints `elastic 26.73 GiB` → **experts 23.73 GiB (89 %) / kv cache 2.76 GiB (10 %)**,
-`vram_weights 27.31 GiB`, `host_pool 44.47 GiB`. `kv_attn` (13 layers, 4-token blocks) pages
-**26.00 KiB** → 91,301 blocks = **365,204 tokens = 1.8 full-length sessions = 91 % of the
-2 × 200,000 worst case** (the resolver never funds 100 %, see Laws); `mover` lends 2,146 slots
-(2.54 GiB) out of the cache to the expert slab; sampler **9 rows**, template 28,234 B, vision live
-(≤ 4,194,304 px, 16,384 patches/pass).
+Boot ledger for the live shape (2026-10-20, pin 1.8.1, `MAX_SEQS=4`, `HOST_POOL_MIB=49152`):
+the resolver prints `elastic 26.73 GiB` → **experts 20.72 GiB (78 %) / kv cache 5.64 GiB (21 %)**,
+`prefill staging 373.65 MiB` out of the cache, `vram_weights 24.30 GiB`, `host_pool 48.59 GiB`.
+The referee line: `kv: the cache can grow to 5.64 GiB a card — 747,492 tokens of context, 3.7
+sessions at 200,000 — with every block it lends the experts taken back; 440.04 MiB of that is
+per-sequence state, and up to 5.20 GiB is lent to the experts while no request holds it`.
+`--checkpoint-slots 40` is auto (`max_num_seqs × 10` slots of 111.98 MiB = 4,479 MiB of pinned
+host), `/health` reports `queue_cap 32` (`max(8, seqs × 8)`), sampler **12 rows**
+(= `seqs × (1 + speculative depth)`), 4 hardware queues a card, template 28,234 B, vision live
+(≤ 4,194,304 px, 16,384 patches/pass), P2P confirmed (`the 2 cards reach each other's memory
+directly`). Experts living in the pinned host pool: **8.99 GiB a rank** (was 5.99) — the price of
+the bigger cache, paid over PCIe when those experts are hit.
 
 The boot **ledger**, not this arithmetic, is the referee: radiance states every budget before
 anything is allocated (weights vs KV, the host pool's coverage of the worst case, the PLE pin,
@@ -145,6 +150,7 @@ marked "re-fetch" is gone from `/home/dank/models/`, which today holds only `Sti
 
 | Window | Payload | Runtime | Shape | Replaced because | Rollback |
 |---|---|---|---|---|---|
+| 2026-10-19 → 10-20 | same `qwen3.8-next-flash-fp8-iq4r-moe.rad` (payload unchanged) | radiance **1.8.1**, `sha256:d590e300…` (same digest) | 2 × 200,000 fp8 KV — resolver cache 2.76 GiB = 365,204 tokens (91 % backing); host pool 44,928 MiB a rank, `TTM_MIN_MIB=150000`, `queue_cap 16`, sampler 9 rows; `--prefill-interleave 1` armed on 10-20 | Frank ordered **four** concurrent conversations over a ≥ 700,000-token pool; the resolver funds that only by lowering the expert floor with more pinned host room (Laws) | revert `1bb6399` and redeploy `scripts/deploy.sh dankserver --service frank-archon` — trio back to `MAX_SEQS=2` / `HOST_POOL_MIB=44928` / `TTM_MIN_MIB=150000` |
 | 2026-10-15 → 10-19 | same `qwen3.8-next-flash-fp8-iq4r-moe.rad` (payload unchanged) | radiance **1.0.13**, `sha256:4c3f4845…` | 3 × 200,000 fp8 KV bought with the **explicit** pair `--vram-weights-mib 25600 --vram-kv-mib 5120`; host pool 44,928 → 45,568 MiB a rank; prefix cache 8 GiB host + 64 GiB disk | decode turned to sludge beside any long prompt — step contention, 18.7 ms decode-only steps against 317 ms steps carrying a prefill chunk (Laws) — and the only two knobs that fix it, `--busy-prefill-chunk` and `--prefill-interleave`, exist only after this pin | `FRANK_ARCHON_IMAGE` back to `sha256:4c3f4845…` **plus a trio rewrite**: restore the pair and the host+disk prefix knobs, delete `BUSY_PREFILL_CHUNK`/`PREFILL_INTERLEAVE`. A digest swap alone is a boot refusal (Runtime) |
 | 2026-10-08 → 10-15 | in-house `qwen4exp-swift15-w4dn8-i8-hc8m.rad`, 116,416 MiB (Swift1.5 abliterated BF16, GPTQ w4 experts + 24 bf16 protected, KLD 0.0131 / top-1 97.92 %) | radiance 1.0.13, same digest | 3 × 200,000 fp8 KV, slab 25,600 / pool 5,120 — the shape the live file still carries | the engine author's own container is the supported path and his quality ceiling; the finetune's refusal-bending left the endpoint | `.rad` purged 2026-10-17 (trash-staged then emptied, Frank's approval). Re-download `frank8465/Swift-1.5-Qwen3.8-Flash-Next-GPTQ-W4A8-Radiance-AMD-R9700` → `qwen4exp-w4nl64-i8-hc8m.rad`, 122,071,973,888 B, LFS sha256 `09dd9306…`, via the iq4r fetch script's hfget/verify pattern retargeted at that repo; point `MODEL_FILE` at it, redeploy. Re-**convert** is dead: the BF16 source was `rm`'d 2026-10-15 (`kld-ref`, grams, corpora and `/home/dank/logs/swift15_*.log` survive) |
 | 2026-10-05 → 10-08 | `qwen4exp-fp8-native.rad`, 177,109 MiB (173.0 GiB) — native modelopt block-FP8, no requantisation | radiance 1.0.7 line, same digest | — | native FP8 experts (56.4 GiB/rank) ate a 40 GiB pool and left KV at 3,543 MiB = 386,904 tokens, **1.93 sessions** — context economics, not quality; and the host pool could not be trimmed to pay for it (36,864 refused the boot) | rebuild-only: `scripts/download-frank-archon.sh` (official `Qwen/Qwen3.8-Flash-Next-FP8`, 131 shards, 172.8 GB, ungated) + `scripts/build-frank-archon-rad.sh` (no-recipe convert under the descriptor law); raw **and** `.rad` were `rm`'d 2026-10-15 (Frank's call, to free the volume for the iq4r download) |
@@ -211,27 +217,44 @@ vllm-radiance era (this table opens on 09-26; the era page claims 10-10).
   never `--kv-cache-size-mib`; with the disk tier engaged the engine also forced ~9.6 GiB of weight
   buffers + arena onto the weights side (~29.6 GiB/card effective). **Neither flag exists at 1.8.1:**
   the same ceiling is enforced by the resolver, and passing the pair is a boot refusal.
-- **At 1.8.1 the split belongs to the resolver, and it funds ~90 % of the worst case, never 100 %.**
-  The engine takes `--gpu-headroom-mib`, the cache bound (`--max-model-len` × `--max-num-seqs`) and
-  `--host-pool-mib`, prints `claimable → elastic → experts / kv cache` before allocating anything, and
-  sizes the expert plane from the model's own weight footprint plus slack — not from a number typed by
-  hand. Three boots of evidence:
+- **At 1.8.1 the split belongs to the resolver, and the source fixes its order.**
+  `core/mem/vram_budget.cpp` claims the card bottom-up (`capacity → already held → drift → arena →
+  staging → queues → prefetch → headroom = claimable`), takes the **static weights off the top as a
+  floor, not a share**, and divides the `elastic` remainder in three lines (146-156):
 
-  | shape | demand | cache given | backing |
+  ```cpp
+  exp = std::min(b.expert_floor, b.elastic);
+  kv  = std::min(kv_cap, std::max(b.elastic - exp, kv_one));
+  exp = std::min(std::max(b.expert_ceiling, b.expert_floor), b.elastic - kv);
+  ```
+
+  `kv_cap` is `KVManager::ceiling()` = `state + Σ_paged max_seqs × ceil(max_ctx / block) × bytes`
+  (`core/mem/kv.cpp:266`), so `--max-num-seqs` and `--max-model-len` set the cache's **demand**, never
+  its funding. The funding is `elastic − expert_floor`, and the floor is
+  `min(plane + spare, plane + spare + 2·unit_max − host_room)` (`core/place/planner.cpp:100-104`, with
+  `host_room = host_pool − file_stage_reserve` at `core/engine_bringup.cpp:1418-1422`). **That is the
+  cache's lever: every MiB added to `--host-pool-mib` drops the expert floor one-for-one and the cache
+  takes it** — minus `stage`, the prefill stager's ring (two layers of the experts left off the card),
+  which is charged back out of the cache whenever the cache lends (`vram_budget.cpp:193-203`). Boots of
+  evidence, all on 1.8.1:
+
+  | shape | demand | cache given | engine's `backs %` |
   |---|---|---|---|
-  | 3 × 200,000, host pool 44,928 | 600,000 tok | 4.20 GiB | 93 % (2.8 sessions) |
+  | 3 × 200,000, host pool 44,928 | 600,000 tok | 4.20 GiB | 93 % |
   | 3 × 200,000, host pool 45,568 | 600,000 tok | **4.20 GiB — byte-identical** | 93 % |
-  | 2 × 200,000, host pool 44,928 (live) | 400,000 tok | 2.76 GiB = 365,204 tok | 91 % (1.8 sessions) |
+  | 2 × 200,000, host pool 44,928 | 400,000 tok | 2.76 GiB | 91 % |
+  | 4 × 200,000, host pool 49,152 (live) | 800,000 tok | **5.64 GiB = 747,492 tok** | 93 % |
 
-  So `--max-num-seqs` is a **demand signal** for the resolver and an admission cap for the scheduler —
-  never a KV allocation — and no slot count fully funds the worst case. Growing host RAM by less than a
-  slab step (640 MiB) moved nothing: the expert plane's claim decides what is left for KV, so cache is
-  grown through slots × window or the dtype, and experts are grown by not leaving elastic pool idle.
-  `--host-pool-mib` is still load-bearing the other way — it is where the expert rows the cards cannot
-  hold get pinned, and under-sizing it has always been a boot failure (36,864 refused a boot in the fp8
-  era). The two-slot boot's own behavioural check: three concurrent conversations all answer `200` —
-  the third **queues** (`queue_cap: 16`), it is not refused; the 400 class is a single request over
-  `--max-model-len`, or three concurrent full-height conversations against a 1.8-session cache.
+  The 45,568 row is the ceiling case, not a mystery: at 3 slots the cache already held its whole
+  `ceiling`, so extra host room could not grow it and shows up as `unclaimed`. **The referee is the
+  ledger line `kv: the pool backs N % … the cache can grow to … N tokens`, never arithmetic.** To buy
+  window: raise `--host-pool-mib` (cost: pinned host RAM, and experts evicted to host cross PCIe —
+  `experts-from-host` was 5.99 GiB a rank at 44,928 and is 8.99 at 49,152) or cut the per-token cost
+  (`fp8` KV). Raising slots raises demand **and** costs 10 × 111.98 MiB of pinned checkpoint-store RAM
+  per slot. Under-sizing the pool the other way has always been a boot failure (36,864 refused a boot in
+  the fp8 era: the host cannot hold what the cards will not). Behavioural check on the live shape:
+  `/health` reports `queue_cap 32`; a request beyond the slot count queues rather than being refused,
+  and the 400 class is a single request over `--max-model-len`.
 - **Idle KV VRAM is the expert cache's spillover — the price is paid twice.** `mover: 2275
   slots can be lent out of the KV cache (2.69 GiB)`, `arena: lends 740 MiB while steps are <=
   256 tokens`; the lend grows with the pool (2.69 GiB from 3.46, 6.08 from 6.912, 4.22 in the pair era)
@@ -280,41 +303,104 @@ vllm-radiance era (this table opens on 09-26; the era page claims 10-10).
 - **MNBT 2048.** 2560 collapses decode to 2.6-7.7 t/s (MTP resonance); the w4 file tier streams
   in place only at MNBT ≤ 2048 and the activation arena scales with the chunk (32768 → 33.3
   GiB, refused).
-- **Decode pays for the chunk it shares a step with.** Census of the live engine taken at the
-  3-slot shape on 1.0.13 (`/stats` + `/metrics`, cumulative over the 2026-10-15 boot):
-  1,435,585 decode-only steps at **18.7 ms** each against 127,991 prefill+mixed steps
-  at **317 ms** — 60 % of engine wall-clock spent inside 8 % of the steps, because the
-  chunk is `min(remaining, checkpoint interval 2048, MNBT 2048)` = 2048 rows and every
-  decode row in that step waits the whole chunk. Day of Prometheus (120 s step, 721
-  samples): `decode_tokens_per_second` median **13.3 t/s** in the 56 % of samples where
-  `prefill_tokens_per_second` ≥ 1000, against 106-240 t/s in the light-prefill buckets;
-  bucketed by mean step time it is 128.7 t/s at 0.02-0.05 s steps and 12.0 t/s at
-  0.15-0.4 s. The stall is **during**, not after — decode in windows 2-14 min after a
-  busy-prefill window sits at the idle baseline (58-64 vs 77-85 t/s, the residual
-  confounded by co-scheduling), so no lingering expert-residency penalty at 2-minute
-  resolution, and `preemptions: 0` rules out preempt-and-re-prefill. Method:
-  [[LLM Performance Diagnosis]] §9. The law is shape-independent; the fix lives at 1.8.1 (next law),
-  and nobody has re-run the census since the migration — so the fix is ordered, **not verified**.
-- **The knobs for it arrived with 1.8.1, and only one of them is on.** `--busy-prefill-chunk` caps the
-  shared chunk so a step with waiting decoders takes a smaller piece (live: `auto`, the engine picks;
-  the explicit value is 512), and `--prefill-interleave N` inserts N decode-only steps after a chunk
-  step taken beside decoders. `interleave` is deliberately **0** — the env comment holds it there until
-  the decode-vs-prefill buckets ask for it, and those buckets have not been read since the migration.
-  The vendor prices a 1024 chunk at about a fifth off prefill throughput to halve the stall; that is a
-  knob for choosing tomorrow's chunk, not a measurement of this shape. MNBT remains an arm and not an
-  edit: 2560 collapses decode through MTP resonance. Any chunk change re-scores draft acceptance before
-  it is trusted.
-- **Slots cost KV, rows, and window — never speed.** `--max-num-seqs` carries no radiance constraint: it
-  adds ≈110 MiB of recurrent state per slot (the live `kv_full_backing` arithmetic prices them exactly),
-  declares the fused TP all-reduce over `seqs × (1 + spec)` rows, and `wht6` is bit-exact up to 25 rows
-  (single-sequence decode and any step of ≤ 25 rows is exact; only busier steps are lossy) — 2 × 3 = 6
-  today. Measured 2026-10-06: seqs 2 and seqs 3 are statistically tied (30.9-33.1 t/s, inside the ±3 %
-  floor). Measured 2026-10-19 at 1.8.1: the third slot's real price is **KV, not rows** — dropping it
-  moved the resolver's cache from 4.20 GiB to 2.76 GiB and the backing from 2.8 to 1.8 sessions, while
-  the ≈4 GiB of host RAM it freed came back unbudgeted, landing in elastic pool that turned into a bigger
-  mover lend instead of cache (resolver law above). The old "seqs 2 cannot boot" law belonged to the
-  retired tcclaviger fork's `torch.compile` shape specialization, and radiance booted seqs 2 on its first
-  fp8-native start.
+- **Decode pays for the chunk it shares a step with, and `--busy-prefill-chunk auto` does not
+  protect it.** Re-measured on the live 1.8.1 shape (34.8 h boot, Prometheus at 60 s,
+  `engine_step_seconds{,_decode}_total` / `engine_steps{,_decode,_mixed,_prefill}_total` /
+  `prefill_tokens_total`): decode-only steps run at **15.5 ms**, chunk steps (a chunk alone, or a
+  chunk with decode rows beside it) at **166 ms** — 4.7 % of the steps hold **34 % of the engine's
+  step time**, so a session decoding while another prompts advances one token per 166 ms. Bucket the
+  harness's `radiance:decode_tokens_per_second` by `radiance:prefill_tokens_per_second` (15 s
+  scrapes; per-stream rate = the gauge ÷ `vllm:num_requests_running`): median **166 t/s** under light
+  prefill, 81 t/s at 1-5k, **13 t/s above 5k** — a **12.7×** collapse, and at 13 t/s with two
+  sessions running each stream sits at 6.7 t/s = 149 ms a token, one token per shared step. Nothing
+  else moves: decode-*only* steps stay 14-18 ms in every bucket (14.1 ms in a prefill-free minute,
+  17.9 ms in the deep one) and the relationship is lag-0 only (r = −0.74 at lag 0, |r| ≤ 0.19 from
+  30 s on, decode back at baseline by 5 min) — residency is not the mechanism either. The second
+  victim is the **arriving** request: through a high-prefill window TTFT p90 goes 2.4 → **18.0 s**
+  and 15.5 % of requests wait over 10 s for their first token, with `http_queue_depth` at 2-3, while
+  median TTFT (~1.9 s) and per-token latency barely move. Preemption is real but burst-shaped: 264
+  `vllm:num_preemptions_total` in the boot, 108 of them inside 105 s of a 6.5k-tok/s prefill. The
+  chunk is `min(remaining, checkpoint interval, MNBT, busy_cap)`; the first three read 2048 here,
+  and `busy_cap` is the fourth law.
+- **`auto` is a prefill-speed dial, not a decoder-protection dial.** `Scheduler::busy_cap` reserves
+  `1 + spec` rows per decoding sequence behind the chunk (3 tokens at MTP 2) plus one eighth of the
+  budget per *waiting request or waiting prefill*, and the code refuses to do more for decoders:
+  "not for decode rows alone: their reserve is a few tokens, so the chunk ends a quantum short and
+  the next step finishes the interval… Halving would hold a long prompt to half-interval chunks while
+  anything decodes behind it, which costs more" (`core/sched/scheduler.cpp:874-878`, 1.8.1). Live
+  proof: `prefill_chunks_capped` 5,018 against 62,386 chunk steps — 8 %, and those are the minutes
+  with a waiter, not the minutes with a decoder. An explicit `N` is the only value that applies
+  "whenever the chunk shares the step".
+- **At MNBT 2048 no chunk value keeps both the arena loan and the staged copies.** The arena is a
+  ladder of levels (256 and 1024 rows here) and a step's rows are its **whole** token count —
+  `max(n_tok, n_seq × (1 + spec))`, `core/engine.cpp:1142` — so a 1024-token chunk with two decode
+  rows is a 1030-row step: it falls back to the full plan, which "lends nothing", and it arms the
+  prefill stager. The stager's floor is the largest lending level plus one, 1025 rows here — named on
+  the boot line `prefill staging: … a step of more than 1024 tokens copies the pooled experts of 48
+  routed layers onto the card up to 3 layers ahead` — and below it "every routed layer reads its
+  pooled experts synchronously and the prefill slows far more than sharing saves" (GUIDE §4.5). The
+  vendor's own number for naive shrinking, on this architecture: four decoders with a long prompt
+  beside them finished in **29.5 s at a 2048 chunk and 31.9 s at 512**.
+- **A big step takes the arena from the expert slab and keeps it for the whole prefill.** The arena
+  lends 987.77 MiB (steps ≤ 256 rows) or 670.26 MiB (≤ 1024) to the slab; a full-plan step reclaims
+  it **synchronously before the step** — units revert to their host copies (an address change, not a
+  copy) and both read streams drain — and `arena_tick` regrows the loan only **2 s after the last big
+  step** (`core/engine.cpp:1129-1202`), so every step of the prefill run, decode-only included, runs
+  with a slab ~780 expert units smaller over a link also carrying the staged copies. `/diagnostics`
+  says the binding constraint in one line: "a prefill step streams every routed layer's pooled
+  experts onto the card, so its speed is bounded by the link; decode reads the ones it routes to".
+  Measured size of the whole effect: the ~10 % above. Real, small, not worth chasing.
+- **`--prefill-interleave` is the dial that buys decode its cadence; armed at 1 on 2026-10-20.**
+  N decode-only steps follow any chunk step taken beside decoders; held steps admit nothing, so it
+  costs the prefilling prompt its TTFT and an arriving request its first step. Rate arithmetic at the
+  two measured step times and 0.657 acceptance (≈2.3 tokens a step): N=0 → ~14 t/s, **N=1 (armed) →
+  ~23**, N=2 → ~33, N=4 → ~48, N=8 → ~69, with the prefill slowed by (166 + 15.5N)/166. **Arithmetic, not
+  measurement** — the arm is chosen by the §9 bucket pair plus `steps_held`, and `auto` is not a
+  substitute for it.
+- **`--prefill-span` is the shape that keeps the loan, and it is priced.** It needs MNBT = N
+  intervals, so `--prefill-span 2 --max-num-batched-tokens 4096`: a *lone* prefill carries 2
+  intervals a step (and on an expert-tiered box only from 8 intervals / 16k tokens, where the span
+  starts to win), while **every other step is planned at the shared budget of 2048** — which is a
+  lending level *and* keeps the stager's ring, the one combination `--busy-prefill-chunk` cannot
+  express. Costs per GUIDE §4.5: 320 MiB a card of expert residency, ~3 % off the KV pool (§4.3's
+  cliff is sharp), a decode step uploads twice the per-step arrays at 4096, and checkpoints inside a
+  span are not written, so a partially-shared prompt resumes one interval earlier. On the vendor's
+  second box (2×R9700, w4nl64, TP2) it was TTFT-neutral — 2.61 vs 2.56 s at 18k, 10.72 vs 10.55 at
+  75k — hence their own rule: measure your own prompts at two ranks before turning it on. MNBT 4096
+  does not boot at 3 slots; this shape is 2.
+- **Most of this endpoint's prefill work is replay of tokens the prefix cache already had.** Over
+  the same window `prefill_tokens_total` 65.2 M against `prefix_hit_cut_tokens_total` 24.9 M = **38 %
+  replayed**, and it is not an eviction: a hit on a hybrid model reuses only as far as the last
+  **linear-state** checkpoint (`reuse = min(h.n_attn_tokens, h.n_linear_tokens)`,
+  `core/sched/scheduler.cpp:953-978`), and the retention default keeps a **geometric ladder** - about
+  `log2(depth/interval) + 2` snapshots - so a turn that diverges `d` behind the tip can resume as
+  deep as `tip − 3d`. The live ladder for a 200k session at interval 2048 is 2048 · 131072 · 163840
+  · … · 198656: diverge at 120k and 21.7k tokens replay, diverge at 50k and 48k. Every
+  `prefix_hit_cuts_total` carries `reason="no_snapshot"` (the other two reasons stay dead), so the
+  cause object agrees and `hit_cut_tokens` is the cost. `--checkpoint-policy` admits exactly
+  **`geometric-backoff` | `tip-only` | `keep-all`** and refuses anything else at boot. It governs
+  retention only - the writes happen at every interval whatever the policy says (only `--prefill-span`
+  skips them) - so `keep-all` buys a replay bounded by one interval at any depth for **pinned host RAM
+  alone**: 97 snapshots a 200k session, `--checkpoint-slots auto` asking 196 × 111.98 MiB = 21.4 GiB
+  against a store budget of an eighth of host RAM (31.5 GiB here, so `share` admits it) with `room` -
+  the pinning room left beside the expert pool at boot - as the hard bound the ledger line names.
+  Retention also spares a snapshot a later turn resumed from (`core/mem/prefix.cpp:709-723`), so a
+  chain that keeps resuming at one deep point stops paying for it. Shortening
+  `--checkpoint-interval` does **not** buy the deep case: the coarsest ladder scale is the largest
+  `interval × 2^k` under the depth, so the deepest gap stays ≈ half the prompt (129,024 tokens at
+  interval 2048 against 130,816 at 256) while every cut multiplies the snapshot writes.
+- **Slots cost KV, host RAM, rows, and pin — never speed.** `--max-num-seqs` carries no radiance
+  constraint: it adds ≈110 MiB of recurrent state per slot, 10 × 111.98 MiB of pinned checkpoint-store
+  RAM per slot (`--checkpoint-slots auto`), and declares the fused TP all-reduce over
+  `seqs × (1 + spec)` rows — `wht6` is bit-exact up to 25 rows, and the live shape is 4 × 3 = **12**, so
+  single-sequence decode stays exact and so does any step up to that many rows. Raising it also raises
+  the cache's *demand* (`ceiling = slots × window`), which the resolver funds from `elastic −
+  expert_floor` — so a slot count without matching host room is paid for by expert residency. Measured
+  2026-10-06: seqs 2 and 3 statistically tied (30.9-33.1 t/s, inside the ±3 % floor). Measured
+  2026-10-19 → 10-20 at 1.8.1: 2 → 4 slots cost **+4,224 MiB of pinned host pool** and **−3.01 GiB of
+  expert residency a card** and bought 2.76 → 5.64 GiB of cache (365,204 → 747,492 tokens). The old
+  "seqs 2 cannot boot" law belonged to the retired tcclaviger fork's `torch.compile` shape
+  specialization, and radiance booted seqs 2 on its first fp8-native start.
 - **A dequantize-to-compute path bills host RAM twice.** On the EMULATION backend an offload request
   of **118 GiB** landed as **~238 GiB** of real host RAM — the dequantized copy rides on top of the
   pinned weights, and the doubling is invisible in the weight count. Read the engine log for
@@ -396,12 +482,35 @@ vllm-radiance era (this table opens on 09-26; the era page claims 10-10).
   4600 MT/s ended it, with zero `gdn_hip` faults either side; the prefix-caching / GDN re-seed
   theory was confounded on both arms. Consumer non-ECC raises no MCE for a silent flip and a
   60 s / 8 GiB pattern check covers 0.5 % of 246 GiB — silent RAM corruption outranks every
-  software theory.
+  software theory. **That mitigation is a BIOS setting and it is not in effect now:** `sudo
+  dmidecode -t memory | grep -i configured` answers 4800 MT/s on 2026-10-20, and the only event
+  between the fix and today is the 2026-10-12 power failure that also reset TTM. Check the speed
+  before crediting any software revert with a fix — and before believing a clean run of the arm
+  you just tested, because the confounder is still in the slot.
 - **TP=2 here** is legal since the 2026-09-20 ProArt B850 swap (x8/x8 on CPU root ports,
   `Routing+`/`ReqEn+` end to end) only because radiance's wire is `libr4d`'s own one-shot
   all-reduce; RCCL needs atomics on the whole chain and fails `hipErrorIllegalState` without
   them (). `wht6` buys +5.6-6.3 % prefill for ~1.3 % of 8-stream
   decode, `exact` is the bit-exact alternative.
+- **The link is already at the board's ceiling — do not chase the `link-below-max` warning.**
+  Both root ports (`00:01.1`, `00:01.3`) are **x8 max** at 32 GT/s, so PCIe 5.0 x8 ≈ 31.5 GB/s is
+  the whole budget per card and the cards' own `pcie_dpm` tables expose only x8 states.
+  `/diagnostics` still warns that the on-card switch hop (`01:00.0`, `05:00.0`) runs "x8 of its
+  x16 while the card is 100 % busy" and suggests a reboot or a reseat — pointless when the host
+  side of the chain is x8 max, which the same endpoint reports two findings later as
+  `link-capped`. The width that matters is the minimum of the chain, and it is x8 either way, so
+  the only lever on a link-bound prefill is **less traffic over the link** (more expert
+  residency, fewer pooled experts), never a wider link. P2P resolves **on** (`auto` asks the
+  driver, the two cards reach each other's memory), so the collectives do not hairpin through host
+  RAM, and the engine's copies ride one DMA queue that "give[s] way to the collectives" — the
+  all-reduce wins the link, the staged experts wait.
+- **Eight cores is the whole host, media stack included.** Dankserver is a Ryzen 7 7700X (8
+  cores / 8 threads, one NUMA node, `nodes: -1` for both cards) running Jellyfin, Plex, Calibre
+  and RomM beside the engine, and `--http-threads` defaults to one thread per core. Measured
+  during a heavy prefill: load average ≈ 1.0, `jellyfin` 11 % CPU, `radiance` 7 % — **CPU
+  contention is not the current decode culprit**, so do not spend an experiment window on it;
+  re-read `uptime` and `ps -eo pcpu,comm --sort=-pcpu | head` first if a future collapse looks
+  different from the step-sharing one.
 - `--prefix-cache-dir` creation is **not recursive** — the serve script `mkdir -p`s the path or
   the disk tier silently never opens. The tier does survive a payload swap when arch and
   tokenizer match (it recovered 900,176 blocks on the 2026-10-15 swap; `cache_n` proves a hit).
@@ -445,11 +554,19 @@ vllm-radiance era (this table opens on 09-26; the era page claims 10-10).
 ## Contract (the wire)
 
 - **Live surface:** `/health` (== `/ping`), `/v1/models`, `/v1/chat/completions`
-  `/v1/completions`, `/metrics`, `/stats`, `/sessions`, `/dashboard`. `/health` answers 200
-  JSON (model id, `in_flight`, `queue_depth`) while serving and **503 only while stopping**
-  (`core/server/admin.cpp:385`), and the listener binds *after* the full load (`main.cpp`:
-  `engine.start()` then `engine.serve()`) — during the load the port refuses connections, so a
-  bare `curl -fsS …/health` gate is honest and needs no body grep.
+  `/v1/completions`, `/metrics`, `/stats`, `/sessions`, `/dashboard`, **`/diagnostics`**. `/health`
+  answers 200 JSON (model id, `in_flight`, `queue_depth`) while serving and **503 only while
+  stopping** (`core/server/admin.cpp:385`), and the listener binds *after* the full load
+  (`main.cpp`: `engine.start()` then `engine.serve()`) — during the load the port refuses
+  connections, so a bare `curl -fsS …/health` gate is honest and needs no body grep.
+- **`/diagnostics` is the instrument for "is the box, not the config, the limit"** — one call
+  returns `configuration` (every flag, so drift from the env file is checkable without the host),
+  `environment`, `derived` (the VRAM split as the ledger prints it), `hardware` (host, per-card
+  `link_chain` + `pcie_dpm` + clocks + power cap + DMA engine choice + P2P answer) and `findings`
+  (level / what / why / fix). On this box it reports `experts-from-host` (5.99 GiB a rank crosses
+  PCIe when used), `link-capped` (root ports are x8 max — the board), `swap-in-use`,
+  `tp-wire-lossy`, and **`link-below-max` as a `warn` at 100 % card busy on both cards** — which is
+  structural on this board; see the x8-ceiling law under *This host, and the deploy path*.
 - **Served id.** `FRANK_ARCHON_SERVED_NAME=frank-archon` (the wire rename of 2026-10-09 moved
   only the alias; container, unit, scripts and env keep the service name). The env's contract
   line is that **radiance validates the requested model name, so every client — harness, bench
@@ -476,12 +593,28 @@ vllm-radiance era (this table opens on 09-26; the era page claims 10-10).
   and 16,384 patches per pass. Probe with a ≥ 256 px solid-colour PNG and a ≥ 256 token budget
   — at 64 tokens you get empty `content` and the colour only inside `reasoning_content`.
 - **Capacity behaviour:** a prompt over `--max-model-len` is refused, never truncated; a request
-  longer than the KV pool's token count is accepted then refused as too large to fit; under the
-  3-slot contract a **fourth** full-height conversation is refused, not paged or squeezed.
+  longer than the KV pool's token count is accepted then refused as too large to fit; a request
+  beyond `--max-num-seqs` is held by the HTTP port (`queue_cap` = `max(8, 8 × slots)` — **32** here)
+  and answered 503 only past that, never paged or squeezed. The cache funds **3.7** full-height
+  sessions, so four conversations can be resident but a fourth near-full-height one can still
+  **preempt a running sequence from the back** to free its blocks
+  (`core/sched/scheduler.cpp:1291-1322`); the victim is recomputed, so its session halts and then
+  re-prefills. Meter: `vllm:num_preemptions_total` (cumulative for the boot, `/stats preemptions`);
+  `radiance:num_requests_preempted` is only the instant depth.
 - **Observability:** `/metrics` carries vLLM-compatible names plus `radiance:*`, scraped by the
-  Dankclaw Prometheus job at `192.168.0.235:7770` over plain LAN routing (the netavark
-  published-port quirk is same-host only). The boot ledger — the referee for every shape number
-  above — is in the container log (`podman logs frank-archon`)
+  Dankclaw Prometheus job at `192.168.0.235:7770` (15 s interval) over plain LAN routing (the
+  netavark published-port quirk is same-host only). **Latency lives under `vllm:`, cadence under
+  `radiance:`** — TTFT / inter-token / per-output-token / e2e / decode-time histograms and the
+  running/waiting gauges are `vllm:*` with no radiance-native equivalent, so a `radiance:`-only
+  query misses every latency answer. The step-phase counters are all scraped:
+  `engine_steps{,_decode,_mixed,_prefill,_held}_total`, `engine_step_seconds{,_decode}_total`,
+  `engine_prefill_chunks_capped_total`, `prefill_tokens_total`, `decode_tokens_per_second`,
+  `prefill_tokens_per_second`, `prefix_hit_cut_tokens_total`, `http_queue_depth`. Two holes: the
+  engine's own step-detail histograms (`prefill_steps_duration`, `prefill_step_tokens`,
+  `token_queue_wait`) are exported but reach no target, and the **arena / expert slab / heat engine /
+  prefill stager have no metric at all** — that half of every law above is read from the boot ledger,
+  `/stats` and `/diagnostics`, never from a graph. The boot ledger — the referee for every shape
+  number here — is in the container log (`podman logs frank-archon`);
   `/home/dank/logs/frank_archon.log` is where the serve script redirects `podman run`.
 
 ## Files

tests/frank_archon_unit.bats

@@ -145,7 +145,7 @@ nosudo_bin() {
     # (torch.compile query_start_loc constraint, 2026-10-02); radiance booted
     # seqs 2 in the fp8-native era and the 2026-10-06 sweep had seqs 2 and 3
     # tied inside the +-3% noise floor — slots buy concurrency, not speed.
-    grep -q '^FRANK_ARCHON_MAX_SEQS=2$' "$ENV_FILE"
+    grep -q '^FRANK_ARCHON_MAX_SEQS=4$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_TP=2$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_TP_WIRE=wht6$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_SPEC_TOKENS=2$' "$ENV_FILE"
@@ -158,7 +158,7 @@ nosudo_bin() {
     # so the pool's token count is a boot-ledger line — verified live by the
     # capacity leg of scripts/probe-frank-archon-kv.py at every cutover.
     grep -q '^FRANK_ARCHON_PLACEMENT=expert_tiered$' "$ENV_FILE"
-    grep -q '^FRANK_ARCHON_HOST_POOL_MIB=44928$' "$ENV_FILE"
+    grep -q '^FRANK_ARCHON_HOST_POOL_MIB=49152$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_KV_DTYPE=fp8$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_NGRAM_PLACEMENT=ram$' "$ENV_FILE"
     # Prefix cache: pinned host RAM only (the disk tier was removed), and the
@@ -177,8 +177,11 @@ nosudo_bin() {
     [ "$ttmt" -gt "$ttmm" ]
     pool=$(awk -F= '/^FRANK_ARCHON_HOST_POOL_MIB=/{print $2}' "$ENV_FILE")
     ph=$(awk -F= '/^FRANK_ARCHON_PREFIX_CACHE_MIB=/{print $2}' "$ENV_FILE")
-    # 2 pools + PLE 47.7 GiB (48,824 MiB) + prefix host, rounded up.
-    ledger=$(( 2 * pool + 48824 + ph + 2048 ))
+    # 2 pools + PLE 47.7 GiB (48,824 MiB) + prefix host + MNBT + the auto
+    # checkpoint store (MAX_SEQS x 10 slots of 112 MiB -- the store is pinned host
+    # memory too, and it grows with the slot count).
+    seqs=$(awk -F= '/^FRANK_ARCHON_MAX_SEQS=/{print $2}' "$ENV_FILE")
+    ledger=$(( 2 * pool + 48824 + ph + 2048 + seqs * 10 * 112 ))
     [ "$ttmm" -ge "$ledger" ]
     # The .rad size floor is positive (a truncated convert must fail fast).
     grep -q '^FRANK_ARCHON_RAD_MIN_MIB=' "$ENV_FILE"