Ultramarine 1 Flash is now on RouterPlus at $0.15/$0.50

Ultramarine 1 Flash, Paper Instruments' model for professional knowledge work, joined the RouterPlus catalog on November 4, 2026. It is served directly by Paper Instruments, at the same per-token price Paper Instruments lists on its own API.

What changed

• Model ID paper-instruments/ultramarine-1-flash is live in the RouterPlus catalog, with Paper Instruments as the provider.
• Paper Instruments built Ultramarine 1 Flash by applying large-scale reinforcement learning to Z.ai's open GLM-5.3 Flash, aimed at finance, law, consulting and operations work.
• Price in the catalog: $0.15 input, $0.03 cached input and $0.50 output per million tokens. Paper Instruments lists the same rates on its Ultramarine API and notes they match GLM-5.3 Flash.
• The RouterPlus route has a 262,144-token context window and up to 65,536 output tokens.
• The weights are on Hugging Face under paperinstruments/Ultramarine-1-Flash, a gated repository with a custom licence.

Pricing on RouterPlus

RouterPlus catalog, November 4, 2026, per million tokens:

What to do

Swap the model ID in any OpenAI-compatible request:

curl https://api.routerplus.com/v1/chat/completions \
  -H "Authorization: Bearer $ROUTERPLUS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "paper-instruments/ultramarine-1-flash", "messages": [{"role": "user", "content": "Hello"}]}'

See the Ultramarine 1 Flash model page and all Paper Instruments models.

Sources

1. Paper Instruments: Ultramarine 1 Flash
2. Paper Instruments: Ultramarine 1 Flash, Scaling Non-Verifiable RL (October 14, 2026)
3. Hugging Face: paperinstruments/Ultramarine-1-Flash
4. RouterPlus model catalog