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Ultramarine 1 Flash

Introduction

Ultramarine 1 Flash is a multimodal model built for knowledge work, specializing in enterprise operations, finance, law, and consulting. Based on GLM-5.3-Flash, it is 320B total parameters and 18B active parameters with 1M total context.

Read the full technical report.

Serve Ultramarine 1 Flash Locally

Ultramarine 1 Flash mostly keeps GLM-5.3-Flash's architecture and FP8 scheme. The shared experts and a few other modules are in BF16 and declared in config.json. We serve it with SGLang on four B300 GPUs:

python -m sglang.launch_server \
  --model-path paperinstruments/Ultramarine-1-Flash \
  --tp-size 4 \
  --disable-shared-experts-fusion \
  --context-length 262144 \
  --reasoning-parser glm45 \
  --tool-call-parser glm47 \
  --speculative-algorithm EAGLE

We tested this command with SGLang v0.5.22 (lmsysorg/sglang:v0.5.22). On Blackwell GPUs, SGLang selects the attention, MoE and KV-cache settings from the GLM-5.3-Flash SGLang cookbook by default. Our setup differs in two ways:

  • --disable-shared-experts-fusion, which keeps the BF16 shared experts separate.
  • A 262,144-token context. Raise --context-length to use the full 1,048,576 tokens.

Reference the cookbook for other hardware.

Recommended settings

  • Sampling: temperature=1.0, top_p=0.95.
  • Context length: GLM-5.3-Flash natively supports a 1,048,576-token context window. Adjust your harness's context and compaction settings based on performance.
  • Run Ultramarine in an agent harness. We open-sourced our harness, training, and evaluation code here: feather-train.
  • Install Paper Office (paper-docx, paper-pptx, paper-xlsx) in your harness for safer office file editing.

Training

Setting Value
Base model GLM-5.3-Flash
Loss CISPO
Optimizer AdamW
Batch size 64 × 8
LoRA rank 64
Learning rate 5 × 10⁻⁵
Sampling config temp = 1, top_p = 1, top_k = -1
Context window 131,072 tokens
Max agent turns 250
Compaction trigger At 85% of the context window or when 30,000 tokens remain, whichever occurs first

License

Ultramarine 1 Flash is released under the Ultramarine 1 Flash License.

Citation

@techreport{paperinstruments2026ultramarine,
  title       = {Ultramarine 1 Flash: Scaling Non-Verifiable RL},
  author      = {{Paper Instruments}},
  institution = {Paper Instruments},
  year        = {2026},
  url         = {https://www.paperinstruments.com/blog/ultramarine}
}
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