Nemotron 3.5 Lightning-Omni: zero-training eyes and ears for NVIDIA's newest agent model (tested GGUFs, DGX Spark)

Two days ago I released the first GGUF build of Nemotron-3-Omni with working
audio and video ( Nemotron-3-Omni with audio + video in llama.cpp on DGX Spark (GGUF, prebuilt binaries) ). Then,
something stranger: I gave NVIDIA’s Nemotron 3.5 Lightning eyes and ears
WITHOUT ANY TRAINING, and it works.

The trick is architectural: Lightning shares the exact backbone geometry of
Nemotron-3-Nano-Omni (nemotron_h, hidden 2688, 52 layers, same vocabulary).
NVIDIA trained the Omni projectors to feed precisely that geometry, so the
C-RADIO vision tower and the Parakeet audio tower attach to Lightning
zero-shot. The result: a 1M-context, 3B-active agent model that reads
images, understands speech, and watches video, at the same decode speed as
the donor, entirely on a DGX Spark on my desk.

What is released, and how it is tested:

  • Image, audio, and video understanding: released and gated. Every
    quantization passes text, image, audio, and video tests before upload;
    the graded matrix ships in the repository.
  • Measured transfer cost: on my 38-word ASR gate, the donor Omni scores
    2.6 percent word error rate, the zero-shot assembly 7.9 percent (rare
    proper nouns). Stated at exactly that scope.
  • One-pass video WITH soundtrack: works zero-shot, with one prompting
    note. I chased this through two wrong hypotheses (temporal-pathway drift,
    then irreversible audio dominance) and measurement killed both. What
    actually happens: video-only works at every length (2 to 64 frames,
    matches the donor), and in one pass with a soundtrack both channels are
    fully present. With a neutral single-subject prompt (“what is in the
    video?”) Lightning tends to answer from the audio and under-report the
    picture. Ask for BOTH and it returns both, every time I tested, temp 0:
    “Describe what is shown on screen AND transcribe what the narrator says”
    gives the full visual description and the full transcription in one
    answer. So it is a released capability with a prompting note, not a
    broken feature. The donor Omni, co-trained on interleaved A/V, balances
    both even at a neutral prompt; a future Lightning projector tune could
    shift that default, but it is polish.

Downloads (quantizations land one by one as each passes its gates; the
matrix grows with them):

Runtime: the same llama.cpp-omni fork as the first release, now rebased
onto current master (release b10598, prebuilt DGX Spark / Jetson Thor
binaries). Image, text and audio also run on stock llama.cpp with these
files:

The narration in my test suite is synthesized by NVIDIA’s Magpie TTS
running as a NIM on the same Spark. Their voice, their models, their desk
computer; the assembly and the graded testing are mine. Happy to answer
questions or fix what breaks.