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Update README.md and pyproject.toml - #4

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andyluo7:andyluo7-patch-1
Nov 25, 2025
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Thanks

@valarLip
valarLip merged commit 95ab338 into ROCm:main Nov 25, 2025
@valarLip
valarLip deleted the andyluo7-patch-1 branch November 25, 2025 13:32
Jasen2201 added a commit that referenced this pull request Jul 29, 2026
#3: Guard MiMo-V2 KV cache builder against PP (total_num_layers is now
    PP-local, so the draft-layer subtraction would go negative).

#4: Move aiter sys.modules stubs from test_pp.py module-level to
    conftest.py behind find_spec guard — prevents cross-test pollution
    when collection order varies.

#5: Use zmq.Context() instead of zmq.Context.instance() for owned
    contexts (instance() is a process singleton — term() would kill
    other users). Add pp_transport.close() in both busy_loop finally
    blocks to stop socket leaks.

#6: Remove dead prefix_cache_hit_tokens=0 (overwritten at line 141);
    restore accidentally deleted num_compressed_hit_blocks comment.

LOW: Convert FIFO ordering assert to raise (survives python -O);
     delete dead ParallelConfig.world_size + world_size_across_dp.
ganyi1996ppo pushed a commit that referenced this pull request Aug 27, 2026
…ation

Findings from @valarLip on #2045, each re-verified against the code rather
than taken on report -- two of the sixteen did not survive that check
(`_rehome_checkpoint` does not exist; `chunk_gated_delta_rule` carries
`@torch.compiler.disable`, so the CUDA-graph half of #12 cannot happen).

**#1, a regression this branch introduced.** `eb058321d` re-keyed `_pending`
to `(seq, hash)` so two boundaries of one prompt could coexist, and did not
touch the drain, which still resolves a single `seq.state_slot` for all of
them. Both images are then copied out of whatever the last forward left there,
filing the earlier hash over the later state -- a request resuming on it
continues from ahead of its own prefix, and `_validate_paged_state_op` passes
because layout, size and unit count are all still correct.

`_supersede` keeps one pending boundary per sequence. Ordinarily a drain
follows every forward and both boundaries are stored correctly from their own
slots; the exception is a pass that schedules nothing, where
`state_maintenance_ops=None` carries `_pending` into the next drain. The newer
boundary wins because it is the one the slot holds, and the older is counted
`dropped` -- it is reuse the placement asked for and did not get. The two tests
that pinned the old behaviour asserted coexistence without asserting each was
stored from its own slot, which the drain cannot do; they now pin the fix and a
sibling covers the ordinary drain-between-forwards case.

**#7** was the same invariant read from the other end: the descriptor buffer is
sized `2 * max_num_seqs` on "one store per sequence", which the re-key removed
and `_supersede` restores. No resize -- the docstrings here and in
`deepseek_v4_attn.py` now name what holds the bound instead of asserting it.

**#2/#3/#4/#5/#8 are all on the midstep write path, so `readable_midstep` goes
back to False.** The write path declines on six conditions `commit_midstep`
cannot see and publishes the hash regardless; `_checkpoint_targets` indexes
three differently scoped sequence lists with one `i`; the SSM read floors to a
64 grid `midstep_positions` does not enforce (`hash_block_size` defaults to
16); the conv window is `conv_kernel-1+num_spec` in the kernel and
`conv_kernel-1` in the guard. Each stores a findable image holding the wrong
state. None of it has run under a server -- K3 takes the PAGE path and cannot
reach it -- so the honest state is off. The machinery and its bit-exactness
test stay; `test_midstep_is_off_in_production.py` pins the decision, and is
deliberately not behind `importorskip` so the non-GPU runner actually runs it.

**#10** `pool_pressure` read `self.state`, which under PAGE is a different
object built with `StateTransfer.none()` that never sees a `checkpoint()`. It
printed four zeros for the life of the server while `checkpoint_funnel`, the
next method, reported the real numbers from the coordinator.

Smaller: `chunks_cut_for_end` and `checkpoints_orphaned` reach both aggregation
whitelists (a cut counter without its sibling is unreadable; `orphaned` argues
for a bigger paged pool where `evicted` argues for a bigger state pool);
`paged_hit` is dropped as a second name for `compressed_hit`;
`_warn_if_unschedulable` compares against `state_slots_per_req` again, so a
pool too narrow for one request warns instead of waiting forever in silence.

`clear_index` still moves no counter, now stated as a decision: each fate
argues for a different fix and an operator emptying the cache argues for none.
ganyi1996ppo pushed a commit that referenced this pull request Aug 27, 2026
…ation

Findings from @valarLip on #2045, each re-verified against the code rather
than taken on report -- two of the sixteen did not survive that check
(`_rehome_checkpoint` does not exist; `chunk_gated_delta_rule` carries
`@torch.compiler.disable`, so the CUDA-graph half of #12 cannot happen).

**#1, a regression this branch introduced.** `eb058321d` re-keyed `_pending`
to `(seq, hash)` so two boundaries of one prompt could coexist, and did not
touch the drain, which still resolves a single `seq.state_slot` for all of
them. Both images are then copied out of whatever the last forward left there,
filing the earlier hash over the later state -- a request resuming on it
continues from ahead of its own prefix, and `_validate_paged_state_op` passes
because layout, size and unit count are all still correct.

`_supersede` keeps one pending boundary per sequence. Ordinarily a drain
follows every forward and both boundaries are stored correctly from their own
slots; the exception is a pass that schedules nothing, where
`state_maintenance_ops=None` carries `_pending` into the next drain. The newer
boundary wins because it is the one the slot holds, and the older is counted
`dropped` -- it is reuse the placement asked for and did not get. The two tests
that pinned the old behaviour asserted coexistence without asserting each was
stored from its own slot, which the drain cannot do; they now pin the fix and a
sibling covers the ordinary drain-between-forwards case.

**#7** was the same invariant read from the other end: the descriptor buffer is
sized `2 * max_num_seqs` on "one store per sequence", which the re-key removed
and `_supersede` restores. No resize -- the docstrings here and in
`deepseek_v4_attn.py` now name what holds the bound instead of asserting it.

**#2/#3/#4/#5/#8 are all on the midstep write path, so `readable_midstep` goes
back to False.** The write path declines on six conditions `commit_midstep`
cannot see and publishes the hash regardless; `_checkpoint_targets` indexes
three differently scoped sequence lists with one `i`; the SSM read floors to a
64 grid `midstep_positions` does not enforce (`hash_block_size` defaults to
16); the conv window is `conv_kernel-1+num_spec` in the kernel and
`conv_kernel-1` in the guard. Each stores a findable image holding the wrong
state. None of it has run under a server -- K3 takes the PAGE path and cannot
reach it -- so the honest state is off. The machinery and its bit-exactness
test stay; `test_midstep_is_off_in_production.py` pins the decision, and is
deliberately not behind `importorskip` so the non-GPU runner actually runs it.

**#10** `pool_pressure` read `self.state`, which under PAGE is a different
object built with `StateTransfer.none()` that never sees a `checkpoint()`. It
printed four zeros for the life of the server while `checkpoint_funnel`, the
next method, reported the real numbers from the coordinator.

Smaller: `chunks_cut_for_end` and `checkpoints_orphaned` reach both aggregation
whitelists (a cut counter without its sibling is unreadable; `orphaned` argues
for a bigger paged pool where `evicted` argues for a bigger state pool);
`paged_hit` is dropped as a second name for `compressed_hit`;
`_warn_if_unschedulable` compares against `state_slots_per_req` again, so a
pool too narrow for one request warns instead of waiting forever in silence.

`clear_index` still moves no counter, now stated as a decision: each fate
argues for a different fix and an operator emptying the cache argues for none.
ganyi1996ppo pushed a commit that referenced this pull request Aug 27, 2026
…ation

Findings from @valarLip on #2045, each re-verified against the code rather
than taken on report -- two of the sixteen did not survive that check
(`_rehome_checkpoint` does not exist; `chunk_gated_delta_rule` carries
`@torch.compiler.disable`, so the CUDA-graph half of #12 cannot happen).

**#1, a regression this branch introduced.** `eb058321d` re-keyed `_pending`
to `(seq, hash)` so two boundaries of one prompt could coexist, and did not
touch the drain, which still resolves a single `seq.state_slot` for all of
them. Both images are then copied out of whatever the last forward left there,
filing the earlier hash over the later state -- a request resuming on it
continues from ahead of its own prefix, and `_validate_paged_state_op` passes
because layout, size and unit count are all still correct.

`_supersede` keeps one pending boundary per sequence. Ordinarily a drain
follows every forward and both boundaries are stored correctly from their own
slots; the exception is a pass that schedules nothing, where
`state_maintenance_ops=None` carries `_pending` into the next drain. The newer
boundary wins because it is the one the slot holds, and the older is counted
`dropped` -- it is reuse the placement asked for and did not get. The two tests
that pinned the old behaviour asserted coexistence without asserting each was
stored from its own slot, which the drain cannot do; they now pin the fix and a
sibling covers the ordinary drain-between-forwards case.

**#7** was the same invariant read from the other end: the descriptor buffer is
sized `2 * max_num_seqs` on "one store per sequence", which the re-key removed
and `_supersede` restores. No resize -- the docstrings here and in
`deepseek_v4_attn.py` now name what holds the bound instead of asserting it.

**#2/#3/#4/#5/#8 are all on the midstep write path, so `readable_midstep` goes
back to False.** The write path declines on six conditions `commit_midstep`
cannot see and publishes the hash regardless; `_checkpoint_targets` indexes
three differently scoped sequence lists with one `i`; the SSM read floors to a
64 grid `midstep_positions` does not enforce (`hash_block_size` defaults to
16); the conv window is `conv_kernel-1+num_spec` in the kernel and
`conv_kernel-1` in the guard. Each stores a findable image holding the wrong
state. None of it has run under a server -- K3 takes the PAGE path and cannot
reach it -- so the honest state is off. The machinery and its bit-exactness
test stay; `test_midstep_is_off_in_production.py` pins the decision, and is
deliberately not behind `importorskip` so the non-GPU runner actually runs it.

**#10** `pool_pressure` read `self.state`, which under PAGE is a different
object built with `StateTransfer.none()` that never sees a `checkpoint()`. It
printed four zeros for the life of the server while `checkpoint_funnel`, the
next method, reported the real numbers from the coordinator.

Smaller: `chunks_cut_for_end` and `checkpoints_orphaned` reach both aggregation
whitelists (a cut counter without its sibling is unreadable; `orphaned` argues
for a bigger paged pool where `evicted` argues for a bigger state pool);
`paged_hit` is dropped as a second name for `compressed_hit`;
`_warn_if_unschedulable` compares against `state_slots_per_req` again, so a
pool too narrow for one request warns instead of waiting forever in silence.

`clear_index` still moves no counter, now stated as a decision: each fate
argues for a different fix and an operator emptying the cache argues for none.
valarLip pushed a commit that referenced this pull request Aug 28, 2026
* feat(state-cache): per-slot allocation, a switchable demand rung, and a -1 interval

Rebased onto main's PAGE-backed checkpoint work (#1874, #1894, #1943, #1880),
which rewrote this subsystem underneath the branch. Squashed to one commit
because the three original commits each re-conflicted against the new base and
against each other's resolutions; the reasoning from all three is kept below.

--- allocate state slots per need, not by group

A "state cache group" was `1 + num_spec` slots wide and was the unit of
everything: allocation, admission, sizing, and the checkpoint index. But a
checkpoint has no speculation to roll back -- it holds a committed state -- so
filing one cost a full group and wasted `num_spec/(1 + num_spec)` of its bytes.
At two speculative tokens that is two thirds.

The slot is now the unit. `--state-checkpoint-slots 64` buys 64 checkpoints for
64 slots instead of 192, and the slots it no longer takes stay in the paged KV
pool. This is only possible because a request's slots need not be adjacent,
which the kernels never required: the ssm kernel gathers each index out of the
indices tensor and the conv path is handed column 0 alone. Contiguity was
manufactured by `prepare_state_indices` writing `arange(base, base + width)`;
it now writes the seq's own slot list straight in.

`StateGroupPool` -> `StateSlotPool`, `Sequence.per_req_cache_group` ->
`state_slots`, whose element 0 is the committed state. The setter re-points [0]
and preserves [1:], because speculation scratch persists across forwards.
`--state-checkpoint-groups` still parses, as an alias.

--- -1 turns off the interval ladder without turning off checkpointing

The interval is a guess about where reuse will resume; a demand rung is a
position a request was actually refused at. On the SemiAnalysis cc-traces the
8192 ladder placed ~30x the writes of the demand rung alone and caught reuse the
demand already reaches -- 0.0% of resumes landed on a ladder rung -- while every
rung costs the prompt that keeps it an extra prefill chunk.

  >0  a rung every N tokens (unchanged, still the default)
   0  state checkpointing off entirely (unchanged)
  -1  no interval rungs; the demand rung and prompt-end anchor still place them

-1 rather than reusing 0 because 0 is the documented contract and is reachable
by accident: the grid snap rounds an off-grid interval down and can land on 0,
so a --block-size typo currently fails safe. Three of the four sites are not the
arithmetic you would guess -- `pos % interval` under -1 admits *every* position
rather than none, and `pos - last < -1` is true for every pos.

--- make the demand rung switchable

A demand rung is 47% of checkpoint writes on the cc-traces and reads back 2.8%
of the time, against 85.2% for a prompt-end anchor. Gated independently of
--state-checkpoint-interval-tokens, because the demand is not part of the
interval grid. Default unchanged. The refusal is still measured when the
placement is off -- switching off a rung must not blind the diagnostic that
justifies it.

--- DeepSeek-V4

Unaffected by the slot-vs-group change, and that claim is now checked rather
than asserted: DSV4 declares `entries_per_req=1` unconditionally (the MTP/DSpark
lookahead widens the slot via `win_with_spec`, it never multiplies the count),
so `state_slots_per_req == 1`, `pop_many(1)` pops the same index `pop()` did,
and slot == group exactly as before. `v4_pool_geometry.py` and `sub_pool_spec.py`
are untouched, so the `_physical_slots` reversal and DSV4's pool size are both
byte-identical to main. DSV4 passes no `extra_entries`, so `--state-checkpoint-
slots` is inert for it.

The *anchor*, though, did reach DSV4 -- and cost it. `PagedStateCheckpointCoord-
inator.applies()` is true for any V4 seq, so `_record_checkpoint_end` reserved a
prompt-end anchor and `checkpoint_cut` shortened a prefill chunk onto it. But the
coordinator files one pending checkpoint per seq (`_pending[id(seq)]`, and it
`del`s `boundary_blocks`), so the prompt-end checkpoint landing a chunk later
overwrote the anchor before either was stored. Measured: one extra prefill chunk
per prompt for a hit rate that did not move (identical re-send 0 blocks either
way, continuation 11 either way).

So the anchor is now gated on `keeps_interior_boundaries`, which `StateSlotPool`
answers True (each boundary is its own slot in the index, so both survive) and
the PAGE coordinator answers False. Asked as a capability rather than by naming
the backend, so a future multi-boundary copy class opts in by answering yes.
DSV4 is back to main's one-cut prefill; GDN keeps the anchor. Pinned by
`test_a_last_boundary_only_class_is_not_anchored_for`.

--- reconciliation with main

Dropped: the copy/pending-checkpoint path (`_commit_pending`, `record_copy`,
`take_copies`, `Sequence.pending_checkpoint`). DeepSeek-V4 checkpointing moved
to `PagedStateCheckpointCoordinator`, and `StateSlotPool` now rejects
`transfer.copies` outright. The fork path (GDN), where the measured wins are, is
kept in full.

`readable_midstep` is carried on main's `StateTransfer` in `state_runtime.py`
(wire format included) rather than on the branch's copy.

Two bugs this rebase exposed, both fixed here:

- `PagedStateCheckpointCoordinator` did not implement the midstep half of the
  `StateCache` protocol, so `checkpoint_cut` raised on every V4 batch. This was
  introduced *by this branch*, not latent in main: `readable_midstep` does not
  exist on main at all, and main's `checkpoint_cut` never consults it. A PAGE
  image is not readable midstep, so the three methods are the no-ops the
  protocol documents.
- `_record_checkpoint_end` could place the anchor past the last matchable block.
  `can_allocate` stops one block short of the prompt, so a checkpoint filed
  under the final block's hash is one no scan looks up -- and being stored, it
  evicted the ladder rung that would have served the resume, taking an identical
  re-request from 8 hit blocks to 0. Capped at `(n_hash_blocks - 1) * hbs`.

Tests: `tests/test_state_checkpoint.py` 171 passed; the state/checkpoint and
DSV4/LMCache suites together 632 passed. Full suite 45 failed /
2300 passed, a strict subset of origin/main's own 114 pre-existing failures --
zero regressions, verified by set difference against a clean origin/main
worktree. black clean; ruff no new findings.

Co-Authored-By: Claude <noreply@anthropic.com>

* remove gpu unit test

Signed-off-by: ganyi <ygan@amd.com>

* remove the triton import part

Signed-off-by: ganyi <ygan@amd.com>

* match main's array('i') token_ids contract in a relocation test

`#1990` added an assertion that `Block.token_ids` is an `array('i')`, not a
list -- a list never compares equal to what the production publish paths
store, so every hit on the block would read as a hash collision. This test
was written before that landed and still passed a bare list.

The file already has `toks()` for exactly this; the test just did not use it.

* feat(state-cache): keep Kimi-K3's KDA checkpoints as PAGE images

A KDA Active Slot is 53.6 MiB. Held as a checkpoint it competed with live
requests for the pool that admits them, so retaining one cost the workload the
concurrency it was retained for. Held as PAGE units it is 127 ordinary KV
blocks -- 0.112% of the paged pool -- drawn from the same free list as
everything else and evicted by the same LRU.

This is the mechanism `main` already ships and DeepSeek-V4 already uses
(`PagedStateCheckpointCoordinator`). Nothing about the coordinator changes;
what is added is the source side of the copy for a state that is two strided
tensors rather than one contiguous slab.

`plan_segmented_copy` intersects two ordered byte streams and needs neither
block alignment nor equal segments, so the state tensors keep their layout: a
slot is 138 ranges (69 conv + 69 ssm) and the planner cuts them against 127
units. `_checkpoint_layer_ranges` is the sole owner of that order -- both the
sizes and the addresses read it, because a plan cut against one order and
addressed through another lands whole layers in the wrong unit.

Two things the port had to get right, both now asserted rather than assumed:

- A PAGE unit is a *logical* block, but `kv_cache` is shaped in physical ones
  and K3's `block_ratio` is 128. `_page_unit_regions` derives its stride from
  `runner.block_size` and checks `num_rows * region == page_unit_bytes`, so a
  granularity mix-up is a startup error instead of 127 blocks of scrambled
  state. Unit ids are range-checked against the logical count for the same
  reason.
- K3's slots are strided by `num_slots`, so an off-by-one in
  `(layer * num_slots + slot)` lands inside a neighbouring request's live state
  rather than off the end of the tensor. V4 cannot fail this way and its tests
  do not look for it; `test_no_bystander_slot_is_touched` does.

`state_spec` now asks for no spare checkpoint slots under PAGE.
`--state-checkpoint-slots` buys Active Slots for checkpoints to sit in, which a
copy does not need -- 1.7 GiB reserved for nothing, and it is the same memory
the paged pool wants in order to absorb the images.

Both fall back to `fork` under pipeline parallelism and RapidServe, where
`get_num_blocks` raises on a copying transfer: answering `copy` there would
turn "K3 keeps no state cache" into "K3 does not start".

The dtype objection in the old `state_transfer` docstring is retired, not
ignored. It was that `_state_dtypes` gives kimi_linear an fp32 v side while the
chunked states are bf16, so a checkpoint cut from the kernel's `h` would hand
cached requests a rounded state. A PAGE image is copied out of the slot and
back into a slot -- both fp32, no kernel output in between, no conversion
anywhere. Both dtypes are named in the layout id, so a build that changed
either cannot read another's images.

Not yet flipped on in anger: `execute_paged_state_copies` is reachable only
from `build()`, and the GPU verification (probe at conc 1 and 8 against the
known-good 0/1 and 0/8, then GSM8K, then a matched-N hit-rate A/B) is the next
step.

Known follow-up, measured before it is fixed: the coordinator keeps one
checkpoint per sequence (`_pending` is last-writer-wins), where the fork path
indexed every boundary. A 24k prompt files at 8192/16384/24576 today and would
keep only the last. If the A/B shows the drop, the lever is to make `_pending`
hold a list -- deliberately not bundled here, because a mechanism swap plus a
policy change is a regression nobody can attribute.

* feat(state-cache): keep every boundary a PAGE seq reaches, not just its last

`_pending` was keyed by sequence, so a prompt's second checkpoint overwrote its
first before either was stored. That made the prompt-end anchor worthless --
it sits under a block from the prompt's end, lands in the same or the adjacent
prefill chunk, and was reliably the loser. `_record_checkpoint_end` reads
`keeps_interior_boundaries` and duly declined to reserve one.

Keyed by `(sequence, prefix hash)` both survive. Reaching the *same* hash twice
still collapses, which is what the hash in the key is for: that is one boundary
reached again, not two boundaries.

This matters because the anchor is the placement that pays. The measurement is
already in `_record_checkpoint_end`'s docstring: of 4,808 cc-trace resumes with
a nonzero KV hit, 93.5% land on a previous prompt end and 0.0% on the 8192
ladder. The ladder was cutting a prefill chunk every 8192 tokens to store
something nothing ever resumed from -- and on this workload a prompt averages
117k tokens, so that is ~14 rungs per request, each one a shortened forward and
an image in the paged pool.

What makes keeping both affordable is the price a PAGE image pays: 127 blocks,
0.112% of the paged pool, against a whole 53.6 MiB Active Slot under `fork`.
The measured run that preceded this kept 1,508 checkpoints with
`checkpoints_evicted: 0` -- capacity was never the binding constraint.

Run with `--state-checkpoint-interval-tokens -1` to drop the ladder entirely
and leave the anchor and the demand as the only two placements.

Three tests changed rather than deleted, because each pinned the old behaviour
deliberately and each now pins its replacement:

- `test_latest_pending_checkpoint_replaces_the_previous_intent` becomes
  `test_two_boundaries_of_one_seq_are_both_stored`, plus a new sibling for the
  same-hash-twice case.
- `test_a_last_boundary_only_class_is_not_anchored_for` becomes
  `test_both_classes_are_anchored_for`.
- Two demand tests rested a tightened pool on "exactly one image"; a prompt now
  stores two, so they spend down to the deepest -- which is both the resume
  target and what `_next_victim` would keep longest.

Not yet measured. The preceding PAGE run at conc 8 reached 91.79% at N=791
against a 96.9% trace ceiling; this is the change aimed at that gap, and the
A/B is the next step.

* refactor(state-cache): drop the parts of the PR nothing reads

Three removals, none of which change behaviour. Verified against the same
4610-passed baseline, and `ruff` on the touched files goes 16 -> 14 findings.

`cache_pressure.py` had no importer anywhere in the tree, and the log field
its regex parses (`Cached/Total:`) was renamed to `Cached/Reusable:` by this
same PR -- so it could not have matched a line this branch produces.

`keeps_interior_boundaries` was a capability hook with one reader and no
implementor that answered `False`: the `getattr` default was `True`, both
classes set `True`, and the case it existed for -- the PAGE coordinator
overwriting its own anchor -- was fixed earlier in this branch by re-keying
`_pending` on `(seq, hash)`. The measurement that justified it (of 4,808
cc-trace resumes with a nonzero KV hit, 93.5% land on a previous prompt end,
0.0% on the 8192 ladder) moves onto `checkpoint`, which is where the key it
argues for lives.

`_log_frequency` and its four `reqs_*` counters cost four `__slots__` entries
and four per-request branches to render one log line, and are read by nothing
else -- not `metrics.py`, not either aggregation tuple in `llm_engine.py`.
`_log_pools` stays: its three rates are pure ratios of totals already kept,
and the paged/state split is this PR's central claim. `_log_pressure` stays
because `checkpoints_*` and `demands_recorded` do reach Prometheus.

Left alone deliberately: the `record_relocation` / `take_relocations` /
`relocate_state_slots` chain is equally unreachable, but it is that way on
`main` too. Deleting main's debt from this branch would widen the diff it is
meant to narrow.

* docs(state-cache): tighten the comments this PR added

No code changes; 375 tests pass and `ruff` on the touched files stays at 14
findings against main's 16.

The bf16/fp32 accuracy argument was written out in full three times --
`GDNStateMixin.state_transfer`, `pop_last_intermediate_states`, and inverted
again in `_KimiMLAGDNCommon.state_transfer` -- each time as a rebuttal to an
objection nobody raised, and two of the three cited
`tests/test_gdn_state_checkpoint_gpu.py`, deleted in a04ce7f. It now lives
once, in the present tense, where the dtypes are chosen; the other two point
at it. That alone is ~30 lines and both dead citations.

Two measurements had spread to four and five sites. The prompt-end anchor's
read-back rate stays in `_record_checkpoint_end`, which exists because of it;
the demand rung's stays in `mark_speculative`, the only place it decides
behaviour, and in the `--state-checkpoint-demand` help text, where a CLI user
cannot follow a code reference. `config.py`, `envs.py`, `sequence.py`,
`page_unit_checkpoint.py` and `checkpointers_at` now reference rather than
restate, so there is one copy to update when the number moves.

The rest is history that git already holds: what an earlier Python-loop
version got wrong, what the upstream branch does with `state_cache_base`,
what this pool "used to allocate", which objection "kept this on fork". Each
is restated as the invariant it was arguing for. Also two stragglers of the
group->slot rename in `attention_gdn.py`, and a call-site comment in
`gdn_attn.py` that restated `_checkpoint_targets`' own docstring.

Left long on purpose: `_page_unit_regions`' logical-vs-physical block-id trap
(K3's block_ratio is 128, and getting it wrong scrambles 127 blocks silently),
`_assert_checkpoint_geometry_still_holds`, the conv-window claim in
`state_transfer`, and `CacheStats`' argument for `reusable` over `full` as the
denominator -- that last reads like a rebuttal but the objection is one a
reader will actually raise.

* docs: describe the two model-agnostic features and the instrumentation

The description covered only the K3 PAGE port, which is 1,221 of the 4,694
added lines. Three things it shipped were undocumented:

Per-slot allocation. `StateGroupPool` -> `StateSlotPool`, and a request's state
goes from one fixed-width group of `1 + num_spec` adjacent slots to a list of
ids that need not be adjacent. The point is that a checkpoint takes one slot
rather than a whole group, since a resumed prefix has no speculation to roll
back. Documents the one consumer that reads past element 0 -- the spec-decode
path, which stopped deriving the set from `base = group * slots_per_group` --
and states why DeepSeek-V4 is a rename rather than a behaviour change.

Midstep checkpoints. A mamba-like backend can now take every boundary a forward
covers out of the chunk kernel's own `h`, instead of having its prefill cut so
the forward *ends* on each one. Covers the reserve/publish/cancel split (the
bytes do not exist when the destination must be chosen), the `is_end` targets
that read the runtime slot because `h` does not hold the final state, and the
paired gate in `checkpoint_cut`/`checkpointers_at` -- suppressing one alone
keeps zero checkpoints with no error. Names Qwen3-Next and Qwen3.5 as the
models on this path and K3 as the one that cannot be, and adds the latter to
the follow-ups.

Hit-rate instrumentation. Every measurement in this PR was read off these
lines. The `[Cache Stats]` denominator was `full`, which includes the trailing
block `can_allocate` never matches -- so it charged both pools for a block
neither was offered and reported an unreachable ceiling; it is now `reusable`.
`[Cache Pools]` splits the series into `paged * state = combined`, which is
what showed the paged index matching 99.4% while the state gate discarded it.
`[Checkpoint Fates]` separates four fates that argue for different fixes, and
`kept: 1508, dropped: 0, evicted: 0` is the evidence behind the "capacity
stopped being the binding constraint" claim.

Also refreshes the numbers the rebase and the two cleanup commits invalidated:
33 files / +4694, the current commit hashes, the per-file table, and the test
baseline (4610 passed / 50 pre-existing failures, 40 of them sglang files that
score identically on origin/main).

* docs(state-cache): KDA's interior h exists; aiter just does not return it

The follow-up said K3 cannot be `readable_midstep` because
`chunk_kimi_delta_attn` "exposes only `output_final_state`". True of the API,
misleading about the cause: in aiter's
`_triton_kernels/chunk_delta_attn/chunk_fwd.py` the per-chunk `h` is computed
at line 170 -- by `chunk_gated_delta_rule_fwd_h`, the same function the GDN
path uses -- consumed by `chunk_gla_fwd_o`, then set to None at line 202 and
left out of the returned tuple.

So the two backends differ in plumbing, not in what their kernels produce.
ATOM vendors GDN's chunk entry under `model_ops/fla_ops/`, which is why
`keep_intermediate_states` could be added there; KDA goes out to aiter, which
has no equivalent. Whoever picks this up is adding a return value, not an
algorithm -- worth stating, because the old wording invites the conclusion
that the kernel would have to be rewritten.

Behaviour is unchanged: K3 stays `readable_midstep = False` and keeps cutting
a chunk per placement. Under the shipped anchor-only policy that is 0% of
prompts cut at 1.00 checkpoints per request, since the anchor lands where the
last prefill chunk was going to end anyway.

* test(gdn): pin the claim readable_midstep rests on, on real hardware

`readable_midstep` asserts that `h[:, j]` is the recurrent state after
`j * 64` tokens, and `BlockManager` acts on it by suppressing `checkpoint_cut`
outright -- the prefill runs full length and the boundaries are harvested from
`h` afterwards. If that assertion is false, every checkpoint the readable path
stores is subtly wrong: a resuming request inherits a state its prefix never
produced, silently.

`TestMidstepCheckpoints` pins everything *around* the claim (which positions
are chosen, reserve/publish/cancel, that the cut is suppressed) but stubs the
kernel, so it cannot see the claim itself fail. This asks the kernel.

Measured on MI355, 8 chunks of 64: all 7 interior boundaries are **bit-exact**
against a forward stopped at that position -- `torch.equal`, not a tolerance,
which is the right bar because both arms round the same fp32 value into the
same dtype (`h` is `k.new_empty`; `_state_dtypes` returns `config.torch_dtype`).

Two smaller guards alongside it: popping consumes the reference, so a later
layer cannot read the previous one's `h` and file it under its own slot; and a
forward that was not asked to keep retains nothing, so the plugins that never
pop do not pin a large tensor past their last forward.

Needs one GPU and a few hundred MB -- no server, no TP, no weights -- and
skips at module level otherwise, following `test_compress_chunk_equivalence`.

* docs: record the midstep hardware result, and narrow what is still unmeasured

"Qwen3.5 is not measured" was true when written and is now too blunt. The claim
`readable_midstep` rests on -- that `h[:, j]` equals the state a forward
stopped at `j * 64` would leave -- has been asked of the kernel directly: 7 of 7
interior boundaries bit-exact on MI355. That belongs in Verification, because it
is the one part of the midstep path a CPU test cannot reach and a failure there
would be silent.

What remains unmeasured is narrower and worth saying precisely: no server has
been stood up on a readable backend, so there is no hit rate, accuracy, or TTFT
for it. Named the three things a single sequence through one kernel cannot show
-- the per-sequence `chunk_offsets[row]` base with two prefills in a batch, the
ordering an `is_end` target depends on, and a resume landing on a stored midstep
boundary -- so the gap is actionable rather than a blanket disclaimer.

* fix(state-cache): address review findings 1, 7, 10 and the instrumentation

Findings from @valarLip on #2045, each re-verified against the code rather
than taken on report -- two of the sixteen did not survive that check
(`_rehome_checkpoint` does not exist; `chunk_gated_delta_rule` carries
`@torch.compiler.disable`, so the CUDA-graph half of #12 cannot happen).

**#1, a regression this branch introduced.** `eb058321d` re-keyed `_pending`
to `(seq, hash)` so two boundaries of one prompt could coexist, and did not
touch the drain, which still resolves a single `seq.state_slot` for all of
them. Both images are then copied out of whatever the last forward left there,
filing the earlier hash over the later state -- a request resuming on it
continues from ahead of its own prefix, and `_validate_paged_state_op` passes
because layout, size and unit count are all still correct.

`_supersede` keeps one pending boundary per sequence. Ordinarily a drain
follows every forward and both boundaries are stored correctly from their own
slots; the exception is a pass that schedules nothing, where
`state_maintenance_ops=None` carries `_pending` into the next drain. The newer
boundary wins because it is the one the slot holds, and the older is counted
`dropped` -- it is reuse the placement asked for and did not get. The two tests
that pinned the old behaviour asserted coexistence without asserting each was
stored from its own slot, which the drain cannot do; they now pin the fix and a
sibling covers the ordinary drain-between-forwards case.

**#7** was the same invariant read from the other end: the descriptor buffer is
sized `2 * max_num_seqs` on "one store per sequence", which the re-key removed
and `_supersede` restores. No resize -- the docstrings here and in
`deepseek_v4_attn.py` now name what holds the bound instead of asserting it.

**#2/#3/#4/#5/#8 are all on the midstep write path, so `readable_midstep` goes
back to False.** The write path declines on six conditions `commit_midstep`
cannot see and publishes the hash regardless; `_checkpoint_targets` indexes
three differently scoped sequence lists with one `i`; the SSM read floors to a
64 grid `midstep_positions` does not enforce (`hash_block_size` defaults to
16); the conv window is `conv_kernel-1+num_spec` in the kernel and
`conv_kernel-1` in the guard. Each stores a findable image holding the wrong
state. None of it has run under a server -- K3 takes the PAGE path and cannot
reach it -- so the honest state is off. The machinery and its bit-exactness
test stay; `test_midstep_is_off_in_production.py` pins the decision, and is
deliberately not behind `importorskip` so the non-GPU runner actually runs it.

**#10** `pool_pressure` read `self.state`, which under PAGE is a different
object built with `StateTransfer.none()` that never sees a `checkpoint()`. It
printed four zeros for the life of the server while `checkpoint_funnel`, the
next method, reported the real numbers from the coordinator.

Smaller: `chunks_cut_for_end` and `checkpoints_orphaned` reach both aggregation
whitelists (a cut counter without its sibling is unreadable; `orphaned` argues
for a bigger paged pool where `evicted` argues for a bigger state pool);
`paged_hit` is dropped as a second name for `compressed_hit`;
`_warn_if_unschedulable` compares against `state_slots_per_req` again, so a
pool too narrow for one request warns instead of waiting forever in silence.

`clear_index` still moves no counter, now stated as a decision: each fate
argues for a different fix and an operator emptying the cache argues for none.

* fix(state-cache): address review findings 6, 9, 11, 13 and 14

**#9 inverts the policy it implements, on the majority of prompts.**
`mark_speculative` exists so a guessed resume point is spent before a known
one -- anchors are read back 85.2% of the time against a demand rung's 2.8%.
Both call sites gated on `if anchor and pos != anchor`, so a seq whose
`checkpoint_end_pos` is 0 demoted *nothing* and filed its guesses at the LRU
tail beside real anchors. `_record_checkpoint_end` leaves it at 0 on four
paths, one being every prompt too short for a keepable end -- the common shape
of an agentic first turn. `_anchor_of` answers None rather than 0 there, which
compares unequal to every position, so those seqs demote everything. Shared by
both sites because two spellings of one rule is how they drift apart.

`publish_midstep(seq=None)` still demotes nothing, now as the stated other end
of the rule: a caller with no sequence cannot tell a guess from knowledge, and
over-keeping costs one eviction where over-demoting spends an anchor.

**#6 could take the engine down over a log line.** The two asserts run for
every prefill seq, over counters with four independent writers -- the
CPU-offload wake sets `num_cached_tokens` without touching the hit-block
counters the rest derive from, so an LMCache resume that loads more prefix than
the GPU index held produces `cached > wanted` legitimately. Now a warning and a
clamp, which also removes a behaviour difference between `-O` and not.

**#11 had two consumers disagreeing about what -1 means.** `BlockManager`
clamps to `max(-1, ...)` and reads -1 as "grid off, anchor and demand still
placing"; the DSV4 offload policy clamped to `max(0, ...)`, folding it into 0,
which for that consumer means no sidecar checkpoints at all -- so the engine
kept checkpointing while offload resume silently degraded to zero reuse. With
no grid to align to the sidecar now takes `resume_alignment` alone.

**#13b/#13c.** `_extend_hash_chain` sat one line above the `_has_page_units`
refusal, so a 128k prompt queued behind a full pool paid ~2000 xxhash rounds
per waiting request per pass for a list that was then discarded. Moved below
it; verified nothing between consumes it, and that its one reader is
`midstep_positions`. The comment claiming it "reads `checkpoint_end_pos`" was
false and is replaced with what actually orders the call.

**#14.** `chunk_gated_delta_rule_fwd` returned `h` unconditionally, so the
caller's frame pinned ~33 MB for the rest of that layer's forward even with
`keep_intermediate_states=False` -- every GDN prefill with checkpointing off,
which is the default, and every vLLM/SGLang/rtpllm caller. The flag now reaches
the producer, so the reference dies with the fwd frame. No compute changes; the
kernel computed it either way. `test_gdn_midstep_state_gpu.py` covers both
values and still passes on hardware.

Suite: 4622 passed against 4618 before, with the same 50 pre-existing failures.

* docs: carry the slot rename into the guides, and document the new knobs

The rename landed in code and left five guides describing a `group` model that
no longer exists. One of them was actively dangerous: the `deallocate` snippet
in the scheduling guide released `seq.per_req_cache_group` — a single slot —
where the real function calls `release_many(seq.state_slots)`. Copied as
written it leaks `num_spec` slots per request, and admission cannot see the
loss because it gates on the free list this never returns them to.

Corrected across `scheduling_kv_cache_guide.md` (the pool construction snippet,
the allocation and deallocation prose, the pool-field list, the Sequence table,
and the fork-checkpoint capacity paragraph), plus the Sequence rows in
`architecture_guide.md` and the GDN state paragraph in
`model_support_guide.md`. `state_slots` is documented as a list with `[0]`
committed and `[1:]` rollback, explicitly not adjacent, with `state_slot` as
the property over element 0 — which is the contract a backend has to know
before it indexes anything.

Newly documented rather than merely renamed:

  * `--state-checkpoint-interval-tokens -1`. The guides described `0` as the
    only off switch, so the ladder-off-but-anchor-on regime this PR added was
    reachable and undocumented.
  * `--state-checkpoint-slots` (and its `--state-checkpoint-groups` alias),
    with the note that a PAGE backend zeroes it out.
  * `--state-checkpoint-demand` / `--no-state-checkpoint-demand`.
  * `ATOM_STATE_CHECKPOINT_DEMAND`, under a new "State checkpoints" section in
    `environment_variables.md` — it had no entry at all.

Every symbol the guides now name was checked to exist in `atom/`. The two
`*_plan.md` files still say `group`; they are dated design notes rather than
reference docs, and rewriting them would misrepresent what was planned.

* revert: drop two changes that belong to other PRs

Neither touches per-request state, checkpoints, or the pools. They rode along
on this branch and widen its review surface for no reason.

`triton_merge_attn_states.py` moves `prefill_tokens_with_context` off
`tl.constexpr`. That is a real fix — a per-batch token count as a constexpr
mints a fresh kernel per distinct batch size, 184 of them in one 8-minute
agentic run — but it is an attention-kernel compile-time bug, not a state-cache
one, and belongs in a PR that says so.

`tests/plugin/test_vllm_kimi_k3.py` moved its registry check out-of-process to
survive `sys.modules` damage other plugin tests do. Also genuine, also
unrelated; verified it does not pollute the session on its own.

`test_rtpllm_forward_context_semantics.py` is NOT reverted, though it looked
like the same category. Its change makes the stubs it installs restore what
they displaced, and without it `atom.model_ops.attention_gdn` and
`atom.utils.forward_context` stay shadowed for the rest of the session:
reverting it turned 3 collection errors into 6, taking
`test_cudagraph_capture_bounds.py` (9 passed alone) and three sglang plugin
modules down with `cannot import name ... (unknown location)`. That is
load-bearing for whether this branch's own suite can be run at all.

* remove --state-checkpoint-slots, which never took effect

The flag sized a flat cushion of spare Active Slots for checkpoints to sit in.
It defaults to 0, DeepSeek-V4 never declared it, and Kimi-K3 overrode it back
to 0 — so on every shipped path it added nothing, and the only configuration
where it did anything was GDN's `fork` with someone passing a value by hand,
which no measurement in this PR or before it covers.

What it was for is real: a checkpoint held as a slot competes with live
requests, so how many can be retained is set by concurrency rather than by how
much reuse the traffic has. The PAGE path solves that properly, by keeping the
image in KV blocks instead of a slot. A cushion would buy the same decoupling
for `fork` at the price of a knob nobody can size without measuring first.

Removing it collapses two things it had propped up. `_KimiMLAGDNCommon.state_spec`
existed only to zero the field and is deleted — with the flag gone the base
spec is already right, and `super()` needs no correction. And
`TestTheSpareSlotsGoBackToTheKvPool` went with it: it monkeypatched
`GDNStateMixin.state_spec` to a lambda returning a literal `extra_entries=32`,
so it asserted against its own stub and would have passed unchanged if
production stopped reading the field altogether. That is the shape @valarLip
flagged, and deleting the feature removes the test's subject rather than its
substitute.

`SubPoolSpec.extra_entries` stays. It is the sizing layer's general capability,
no backend passes a nonzero value today, and the test that pins its arithmetic
now says so — a future cushion should get a flat one, not `width x` what it
asked for.

4620 passed against 4622 before, the difference being the two deleted tests;
same 50 pre-existing failures. `ruff` on the touched files matches origin/main
exactly.

* test: keep the midstep watch on the CPU-only side of the aiter line

`test_gdn_does_not_declare_itself_midstep_readable` reached
`GDNStateMixin.state_transfer`, which means importing `gdn_attn`, which
imports aiter at module level. The non-GPU CI runner installs CPU torch and
neither aiter nor triton, so that is a collection-time
ModuleNotFoundError, not a skip -- it failed the job.

Split the flag's two halves by what a CPU runner can actually see. The PAGE
coordinator's `readable_midstep`, the three-call midstep protocol on
`StateCache`, and `StateTransfer`'s field are all pure Python and stay
watched here. GDN's declaration is the half that needs aiter; it belongs
with the kernel tests, and the docstring now says so rather than leaving the
next reader to rediscover it by breaking CI.

Coverage lost is one assertion, not the mechanism: `TestMidstepCheckpoints`
builds its own `StateTransfer(readable_midstep=True)` and exercises the
write path regardless of what production declares.

---------

Signed-off-by: ganyi <ygan@amd.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Guanbao Yu <Guanbao.Yu@amd.com>
zejunchen-zejun pushed a commit that referenced this pull request Aug 31, 2026
…dge the engine

`Scheduler._reconcile_stalled_deferred_saves` frees the blocks of a save the
backend never reported (LMCache force-unpins a stalled transfer without a
completion), but it only touched the scheduler's `deferred_free_blocks` -- the
connector still held the save in `_save_inflight`. `save_finished` cannot clear
it: handed the raw request id while an exact `SaveOperationId` generation is
parked, it deliberately refuses (a delayed TP notification must not complete a
newer lifecycle). So `_save_inflight` never drained, `should_defer_free` stayed
True and `has_pending_kv_work()` never went False, and the EngineCore
busy-looped with every GPU idle -- reproduced under a tight pool on the k3-dev
line.

Add an `abandon_save(req_id)` hook that drops the entry unconditionally:
- `_offload_common`: `_cancel_save_statistics`, mirror of the existing
  `_cancel_load_statistics` -- the bytes were never persisted, so cancel the
  inflight-tokens gauge rather than counting a success.
- `DenseOffloadConnector.abandon_save`: pop `_save_inflight` (+cancel stats) and
  `_save_tracker` so the save loop cannot re-emit against freed blocks.
- `KimiK3OffloadConnector.abandon_save`: also re-run `_refresh_save_stall` so the
  stall latch sheds the abandoned sid instead of staying stuck True.
- offload wrapper + MultiConnector: forward the call to the owning sub.
- `Scheduler._reconcile_stalled_deferred_saves`: notify the connector via a
  getattr-guarded `_connector_abandon_save` before deallocating.

Tests: make the reclaim stub realistic (production always sets `kv_connector`)
and add a test asserting the connector is notified with the string request id.

Addresses review finding #4 (_save_inflight never cleared on reclaim → busy-loop).
zejunchen-zejun pushed a commit that referenced this pull request Aug 31, 2026
…om success

When the worker state tier never built, a joint load (KV + recurrent state)
was left unreported. `_arm_joint_loads` skipped the park on `_state_tier is
None`, so `get_finished`'s `_state_tier is None` early-return let the KV leg
pass straight through as `finished_loading`. `Scheduler._settle_state_load`
(scheduler.py:3503) then counted that as `ok=True` -- a state restore that
never happened -- and the request resumed decode reading an Active Slot the
state H2D never wrote: silent wrong output.

The maintainer reopened the #5 rebuttal on exactly this: the skip was the guard
I added *for* #4 (avoid arming under a `kv_id` the state leg could never
settle, which would leak a park entry). The two fixes were individually right
and jointly left the load unreported.

Fix, in cooperation with #4 (not a revert of it):
- `_arm_joint_loads` arms a joint load with or without a tier. `_start_state_loads`
  already fails the state leg on the no-tier path (`_fail_state_loads` ->
  `settle_state(ok=False)`); with the arm in place that failure lands on a real
  park entry, so the pair is marked failed and owes only the KV leg.
- `get_finished` drains the park via `_settle_joint` (empty state reports) on
  the no-tier path too, before its early return. The landed KV completion
  settles the pair into `failed_loading` -> the request recomputes.

This does not reintroduce #4's leak: the arm is safe precisely because the drain
runs -- the KV completion always arrives (finished or failed) and releases the
park entry. A state-only load (no KV leg) is still not armed and is reclaimed by
`reconcile_orphan_load_slots`' abandon window, as before.

Updates the stale unit test (no-tier is now a fail-for-recompute, not a
KV-only passthrough) and its helper docstring.
zejunchen-zejun pushed a commit that referenced this pull request Sep 1, 2026
`state_entry_views(slot)` indexed `self._slot_views()[slot]` directly. The
slot views are a fixed-length list, so a negative slot -- e.g. the -1
"no slot" sentinel that appears on padded/aborted tokens elsewhere on this
path -- does not raise; Python returns the last slot's views, and the gather
or scatter then reads or writes another request's state under this request's
identity. That is silent cross-request corruption with no exception to point
at.

Raise IndexError on a negative slot. The upstream invariant is that a real
slot is always non-negative, so this only ever fires on a genuine bug, and
turns what was a silent wrong-answer into a loud, locatable failure. This is
the guard promised in the round-3 review reply for refuted-#4: rather than
rely on the upstream invariant holding forever, make the violation
observable at the point it would corrupt state.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
gbyu-amd pushed a commit that referenced this pull request Sep 14, 2026
Nine of the twelve reported findings; the other three are answered on the PR.

Wrong rows, two callers (#4). The DCP branch re-read the global local-length
buffer from index 0. A TBO ubatch already publishes its own offset slice on its
metadata, so read that through `get_published_dcp_local_context_lens`, the same
accessor the scorer uses, and keep the global buffer as the fallback for callers
that publish nothing -- leaving every non-ubatch path unchanged.

Stale schedule, draft steps 1..K-1 (#5). The publish sat in
`_enter_decode_metadata`, which runs only at step 0 and before
`prepare_mtp_decode` refreshes the lengths it is built from. Publish once per
step, immediately after that call; this fixes the draft half of #4 too.

Silent short schedule (#3). `top_k_per_row_decode` bounds its scan by
`local_ctx`, so the buffer's uninitialised tail is inert and a blanket `-inf`
fill would buy nothing per step. What is real is a schedule that under-covers
rows inside the window: `[:parallel_units]` truncates silently while
`indexer_fp4_n_ctas` still reports the full count. Assert instead.

Unsupported combinations (#6, #7). Prefill micro-batching cannot carry the FP4
schedule -- `split_attn_metadata` rebuilds metadata from declared fields, and a
ubatch rebases the row ids the schedule encodes -- so refuse it as PCP already
is; decode micro-batching is handled and stays allowed. A pooled indexer scores
through `sparse_attn_indexer_kpool`, which has no FP4 arm, so the predicate now
rejects `index_kpool > 1`. That also removes the only reachable route to a
scorer block size the cache never used (#8) and makes the block-size message
name the quantity it actually checks (#10).

Comments and messages (#9, #11, #12). `fp4_decode_parallel_units` is not
monotonic in `next_n` -- `f(3)` is 513 against `f(4)`'s 512 -- so state the
weaker `f(n) >= f(1)` that is true and is what lets one buffer serve both widths
requested, with a test pinning the invariant and the counterexample. The staged
table's raise now names the summed co-scheduled context rather than knobs that
do not bound it. The synthesised fp32 return is zeroed rather than left
uninitialised.

Docs: a row for `sparse_indexer_fp4.py` in the model-ops table, and the
block-size-64 requirement plus the gfx950, geometry, PCP and KV-transfer
conditions written into the two config tables that contradicted the code.
gbyu-amd pushed a commit that referenced this pull request Sep 14, 2026
Nine of the twelve reported findings; the other three are answered on the PR.

Wrong rows, two callers (#4). The DCP branch re-read the global local-length
buffer from index 0. A TBO ubatch already publishes its own offset slice on its
metadata, so read that through `get_published_dcp_local_context_lens`, the same
accessor the scorer uses, and keep the global buffer as the fallback for callers
that publish nothing -- leaving every non-ubatch path unchanged.

Stale schedule, draft steps 1..K-1 (#5). The publish sat in
`_enter_decode_metadata`, which runs only at step 0 and before
`prepare_mtp_decode` refreshes the lengths it is built from. Publish once per
step, immediately after that call; this fixes the draft half of #4 too.

Silent short schedule (#3). `top_k_per_row_decode` bounds its scan by
`local_ctx`, so the buffer's uninitialised tail is inert and a blanket `-inf`
fill would buy nothing per step. What is real is a schedule that under-covers
rows inside the window: `[:parallel_units]` truncates silently while
`indexer_fp4_n_ctas` still reports the full count. Assert instead.

Unsupported combinations (#6, #7). Prefill micro-batching cannot carry the FP4
schedule -- `split_attn_metadata` rebuilds metadata from declared fields, and a
ubatch rebases the row ids the schedule encodes -- so refuse it as PCP already
is; decode micro-batching is handled and stays allowed. A pooled indexer scores
through `sparse_attn_indexer_kpool`, which has no FP4 arm, so the predicate now
rejects `index_kpool > 1`. That also removes the only reachable route to a
scorer block size the cache never used (#8) and makes the block-size message
name the quantity it actually checks (#10).

Comments and messages (#9, #11, #12). `fp4_decode_parallel_units` is not
monotonic in `next_n` -- `f(3)` is 513 against `f(4)`'s 512 -- so state the
weaker `f(n) >= f(1)` that is true and is what lets one buffer serve both widths
requested, with a test pinning the invariant and the counterexample. The staged
table's raise now names the summed co-scheduled context rather than knobs that
do not bound it. The synthesised fp32 return is zeroed rather than left
uninitialised.

Tests reach their skips through one `_import_or_skip` rather than
`pytest.importorskip`, which only warns on a plain `ImportError` instead of a
missing module. On a CPU runner that is exactly how these modules fail --
`aiter` imports but carries no `QuantType` -- and CI escalates the warning.

Docs: a row for `sparse_indexer_fp4.py` in the model-ops table, and the
block-size-64 requirement plus the gfx950, geometry, PCP and KV-transfer
conditions written into the two config tables that contradicted the code.
gbyu-amd pushed a commit that referenced this pull request Sep 15, 2026
Nine of the twelve reported findings; the other three are answered on the PR.

Wrong rows, two callers (#4). The DCP branch re-read the global local-length
buffer from index 0. A TBO ubatch already publishes its own offset slice on its
metadata, so read that through `get_published_dcp_local_context_lens`, the same
accessor the scorer uses, and keep the global buffer as the fallback for callers
that publish nothing -- leaving every non-ubatch path unchanged.

Stale schedule, draft steps 1..K-1 (#5). The publish sat in
`_enter_decode_metadata`, which runs only at step 0 and before
`prepare_mtp_decode` refreshes the lengths it is built from. Publish once per
step, immediately after that call; this fixes the draft half of #4 too.

Silent short schedule (#3). `top_k_per_row_decode` bounds its scan by
`local_ctx`, so the buffer's uninitialised tail is inert and a blanket `-inf`
fill would buy nothing per step. What is real is a schedule that under-covers
rows inside the window: `[:parallel_units]` truncates silently while
`indexer_fp4_n_ctas` still reports the full count. Assert instead.

Unsupported combinations (#6, #7). Prefill micro-batching cannot carry the FP4
schedule -- `split_attn_metadata` rebuilds metadata from declared fields, and a
ubatch rebases the row ids the schedule encodes -- so refuse it as PCP already
is; decode micro-batching is handled and stays allowed. A pooled indexer scores
through `sparse_attn_indexer_kpool`, which has no FP4 arm, so the predicate now
rejects `index_kpool > 1`. That also removes the only reachable route to a
scorer block size the cache never used (#8) and makes the block-size message
name the quantity it actually checks (#10).

Comments and messages (#9, #11, #12). `fp4_decode_parallel_units` is not
monotonic in `next_n` -- `f(3)` is 513 against `f(4)`'s 512 -- so state the
weaker `f(n) >= f(1)` that is true and is what lets one buffer serve both widths
requested, with a test pinning the invariant and the counterexample. The staged
table's raise now names the summed co-scheduled context rather than knobs that
do not bound it. The synthesised fp32 return is zeroed rather than left
uninitialised.

Tests reach their skips through one `_import_or_skip` rather than
`pytest.importorskip`, which only warns on a plain `ImportError` instead of a
missing module. On a CPU runner that is exactly how these modules fail --
`aiter` imports but carries no `QuantType` -- and CI escalates the warning.

Docs: a row for `sparse_indexer_fp4.py` in the model-ops table, and the
block-size-64 requirement plus the gfx950, geometry, PCP and KV-transfer
conditions written into the two config tables that contradicted the code.
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