ltx-2.5-mlx-ditq8

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.