LTX-2.5 — int8 DiT (MLX)
The
transformer only, quantized to int8 group-64, for
mlx-community/ltx-2.5-mlx. Every other
component (Gemma-4 text encoder, connector, VAEs, vocoder, duration head, upscalers) comes from
that base repo — this repo deliberately carries
one file, so there is nothing to keep in sync.
MLX conversion of
Lightricks LTX-2.5, consumed by
ltx-2-mlx (Python) and
ltx-2-mlx-swift (Swift).
Why this exists
LTX-2.5's bf16 DiT is ~38 GB resident. On a 64 GB machine that left the tier it ships on at 96%
of its memory budget — technically admissible, with 1.69 GB of headroom, at a geometry below
the profile's own frame cap. int8 takes the same tier to 57%.
Recipe
int8, group 64, transformer_blocks only — identical to the LTX-2.3 recipe, and read off the
shipped 2.3 q8 checkpoint rather than invented. QUANT-RECIPE.json in this repo records it
machine-readably.
⚠️ There is no int4 sibling, deliberately. int4 was built, gated and rejected: connector
output at valid token positions read 0.996728 against a 0.999879 bf16 floor — 27× the baseline
angular error. It is not published because it should not be used.
Fidelity
Measured against the bf16 DiT on identical inputs at the shipping geometry (N=5632):
cosine 0.99824 — and for calibration, LTX-2.3's q8 measured the same way reads 0.99238, so
2.5's int8 sits 4.3× closer to its bf16 than 2.3's does.
⚠️ A quant-vs-bf16 cosine is only readable against the same measurement on a known arm. Do not
compare this figure to numbers produced by a different harness.
Use with weight streaming
Pairs with
xocialize/ltx-2.5-granules — a
per-block re-layout of these exact bytes that streams the DiT from SSD instead of loading it
resident. Output is
bit-identical to the resident path (memcmp-gated, with a poisoned-slot
negative control). Streaming replaces this file rather than supplementing it: fetch one or the
other, not both.
Licence
LTX-2 Community License — see LICENSE.md and the acceptable-use policy snapshot in this repo.
The weights are a derivative of Lightricks LTX-2.5 and carry its terms, including the revenue gate
and non-compete in Attachment A. Redistribution is permitted under §3 with those terms propagated.