Mach X v0.2.21

Everything since v0.2.20: Flash-Next now reads long image prompts with the image, restart points reach Flash-Next and image conversations, --spec is offered for the 35B-A3B class and Flash-Next, and Flash-Next's MTP head is available as an opt-in.

Build gate: the public tree built from scratch gives an ie byte-identical to the tested one (md5 57b6f835); six host suites pass.

Mach X v0.2.21

Everything since v0.2.20. Every figure was
measured on October 5, 2026, on two Arc Pro B70 cards, on community fine-tunes of the models, old path against new path on
the same day; "serve" is ie serve with an OpenAI client, greedy unless a line says otherwise.

Flash-Next reads long image prompts with the image

An image prompt of more than 2,048 tokens was answered by Flash-Next as if there were no image (v0.2.10 through v0.2.20). A
picture of a green square was described correctly at 281 and 1,318 prompt tokens and as "a red circle" or "a blue circle" at
2,199, 5,697 and 16,747. The pipelined prefill (the path for prompts over 2,048 tokens) resets both stages and did not stage
the picture again afterwards, so the model saw image-pad embeddings at plain positions; IE_Q4E_NO_PIPELINE=1 had been right
before the fix, which is how it was isolated. Now both test images are right at all four lengths and in a two-picture
conversation. The indexer's pooled block keys also take the picture's position streams, as its query already did
(IE_Q4E_QSA_MROPE_KEYS=0 reverts that part; the evidence for it is weak).

A conversation edited in the middle restarts from a saved point on Flash-Next, and image conversations keep theirs

The restart points of v0.2.18 now cover Flash-Next at one request lane. Its recurrent state (DeltaNet state and conv, the PLE
conv and history, the indexer's block count) is copied to pinned host memory, because the cards are full of expert cache,
at the conversation boundary, at the reply's end and wherever a 2,048-token chunk of the pipelined prefill passes a multiple
of the step; each stage takes its copy right after its own part of the chunk, so the pipeline is not cut. On a 15.7K-token
prompt (ie serve --ctx 65536): one line changed two thirds in 28.5 → 18.4 s, back to the first prompt 28.5 → 18.4 s, the
edited prompt with another question 26.4 → 16.2 s; the first read costs nothing (29.1 s against 29.0). All six replies equal
with the restart points on and off. IE_DN_LADDER=0 turns them off.

Image conversations keep their restart points too (27B and 35B-A3B splits, Flash-Next): the token record carries the picture's
hash at every image position, so the same picture shares its start and a different picture of the same size ends the shared
part where it starts. The second turn of a 16.7K-token image conversation:

second turn of a 16.7K-token image conversation	before	v0.2.21
Qwen3.8-27B	10.2 s	4.5 s
35B-A3B class	7.2 s	1.0 s
Flash-Next	24.8 s	3.0 s

The 35B-A3B replies were byte-equal (five requests, two pictures) and so was Flash-Next's first conversation; Flash-Next's
other follow-up was token-equal for 151 tokens of reasoning and then words its answer differently (the 32-token tail is read
in another chunk shape). IE_DN_LADDER_VISION=0 turns the image part off.

--spec is offered for the 35B-A3B class and Flash-Next

ie capabilities reported features.speculative only for the dense 27B and Gemma-4, so a client's load screen had no switch
for the other two even though --spec works there. It now reports it for the 35B-A3B class (lookup drafts across the request
lanes) and Flash-Next (lookup drafts at one request lane: with --parallel above 1 they are off, and the load says so; they
are not used on image requests). What the switch does is described in New in v0.2.18.

Flash-Next's MTP draft head: opt-in, and measured as not worth turning on

--spec --spec-head <mtp-head.gguf> (or IE_Q4E_MTP_HEAD) at one request lane loads the model's multi-token-prediction head
onto the tail stage (5.2 GB, a separate file taken from the base model's repository; it is not found by itself). Every committed
forward is fed to it, and where there is no repeat to copy a round drafts three tokens and checks four rows with the exact
verify kernels. The tokens are plain decoding's (800 greedy bench tokens and the restore / restart test equal); a draft of five
gave different tokens and was slower, so it stays at three. Measured on the UD-Q4_K_XL file, both cards:

Flash-Next, MTP head on, against off	off	on
bench decode, greedy	28.7 / 28.3 tok/s	30.8 / 33.7 (2.7–3.0 tokens a round)
bench decode at temperature 0.7		no gain
prefill	502 tok/s	412
serve, two long reasoning replies	36.5 / 36.0 s	34.1 / 33.8
serve, an ordinary question at temperature 0.7	9.0 s	9.4
serve, a 1,800-token file edit with --spec	30.7 s	33.5

A four-row check costs two plain steps and the head takes about 4.7 GiB of expert cache, so it is a small greedy gain against
a slower read; it is off unless a path is given. IE_Q4E_MTP=0 keeps it off even with a path.

What is still slow, and not checked

• Re-checked for this release on October 7, on the build that was published: Flash-Next with the vision tower answered both pictures correctly at 281, 1,318, 2,386, 6,617 and 16,747 prompt tokens (10 of 10); a 15.6K-token text prompt took 21.0 s to read and 12.4 s after one line changed two thirds in (a restart in place at token 8,192, 4.6 ms); ie capabilities reports speculative for Flash-Next; the capabilities, CLI-help and ChatML host tests pass. The 27B and 35B-A3B class were not loaded again: their figures above are the October 5 ones.
• The standalone runner's Flash-Next figures with the head (37.1–38.2 chat and 44.4–44.6 code tok/s, September 27, greedy,
  96 tokens, the base model) were not reproduced in ie serve. A side-by-side run of both on the same served file would say
  why; until then the table above is what the server does.
• Flash-Next's restart points and lookup drafts are for one request lane; the lanes do not have them. The MTP head is one
  lane, greedy, and is not combined with images.
• Not covered: a copy cursor or change list on the 27B and 35B-A3B class (small expected gain, skipped).
• Everything listed under New in v0.2.20 still holds.