H3 compact Q8 OOM on M5 Max 48GB — bf16 DiT reaches 38.58 GiB before ModulationCache build

System

MacBook Pro M5 Max
18-core CPU / 40-core GPU
48 GB unified memory
Phosphene 4.12.2
Installed through Pinokio
Hailuo H3 installation completed successfully

H3 installation/update status

The H3 preflight correctly identifies the machine as requiring the reduced-RAM Q8 engine:

H3 memory preflight OK - 36-60 GB class: the reduced-RAM Q8 engine is REQUIRED here

Running Update Hailuo H3 runner (weights kept - no re-download) completes successfully.

The updater reports:

H3 venv healthy - reusing it

H3 deps OK

Turbo adapter already present

TAE draft decoder already in place (verified)

Q8 engine already built - skipping

Problem

Every H3 image-to-video attempt fails with a Metal out-of-memory error, including the minimum practical configuration:

Image mode
Draft
640×384
3 seconds / 73 frames
Turbo / LightX2V 4-step adapter
TAE draft decoder

Higher-quality and Standard-speed configurations fail as well.

The generated command includes both the bf16 DiT and compact Q8 root:

--dit .../deepbeep-pruned-bf16/MiniMax-H3-FL2VA-pruned_bf16.safetensors

--compact-root .../ddalcu-q8

The render log then reports:

MiniMax-H3-FL2VA-pruned_bf16.safetensors: 532 tensors, 41.40 GB

dit_load_bf16: 8.0s, peak 38.58 GiB, active 38.58 GiB

It proceeds to:

== adaln_cache_and_noise ==

and fails while building ModulationCache:

cache = ModulationCache.build(dit, timestep_table, dtype=mx.bfloat16)

followed by:

RuntimeError: [METAL] Command buffer execution failed: Insufficient Memory (00000008:kIOGPUCommandBufferCallbackErrorOutOfMemory)

Question

Since the reduced-RAM Q8 engine is successfully built and --compact-root is being supplied, should the runtime still be loading the 41.40 GB pruned bf16 DiT and reaching ~38.58 GiB active memory before building the modulation cache?

Is the compact/Q8 path failing to activate, or is there another configuration required for a 48 GB Apple Silicon system?

I can provide the complete render log, H3 update/install log, and metrics JSON if useful.