When was Mammoth 1 released?

Baseten released Mammoth 1 on 21 Oct 2026. It is available through the Opper gateway.

Does Mammoth 1 support zero data retention?

Yes. Mammoth 1 is available with zero data retention on Decision Models through the Opper gateway.

Where is Mammoth 1 hosted?

Mammoth 1 runs on EU hosting routes through the Opper gateway, with contractually enforced residency on supported providers.

Is Mammoth 1 trained on prompts and outputs?

No. Every hosting route for Mammoth 1 is configured so customer prompts and outputs are not used to train models by default.

Mammoth 1

by Baseten

Announcement · All Baseten releases

mammoth-1 is a full fine-tune of Qwen3.5-27B by Base Labs at Baseten for single-pass, calibrated decisions. Give it a state (text, optionally with images) and a set of questions, and it returns a probability for every option of every question from one shared prefill. It was trained on 6.21 million decision examples with a calibration term and a trained "I don't know" option, and Base Labs reports it first on the Jev Decision Index 0.4 at 71.24. Requests longer than its trained length of 16,384 tokens are refused, not truncated. The weights are on Hugging Face under the MIT license; elephant-1 is its 9B sibling.

Call Mammoth 1 on Opper through the System One evaluation API. Sign up without a credit card. Get started

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Key info

Input

Output

Features

Context window

Input price

$0.10 /1M

Released

21 Oct 2026

EU residency available
Zero data retention on pay-as-you-go
No training by default

Available routes

Mammoth 1 runs on 1 route through the Opper gateway. Compare residency, zero data retention and training posture at a glance, with full data-handling detail per route below. In the EU it is served by Decision Models. See every model hosted in the EU.

Provider	Region	Zero data retention	Training	Input	Output	Cache read
Decision Models	EU		No	$0.10	—	Input price

Live routes and prices as JSON: api.opper.ai/v3/models?q=decisionmodels%2Fs1-pro-5

Data handling per route

Each route hosting Mammoth 1 has its own privacy posture, residency, and GDPR terms. Postures are maintained by Opper with a last-verification timestamp.

Decision Models — EU🇪🇺

Zero data retention: nothing is logged, held for abuse monitoring or used for training. No training on customer data. EU.

Zero data retention: Yes. Nothing is logged, held for abuse monitoring or used for training.
Training: No training on customer data.
Logging: None
Abuse monitoring: No classifier
Subprocessor access: No subprocessor reads content
Transfer mechanism: Not applicable — data stays in EU

Best for

The model directory pages that list Mammoth 1.

Listed inDecision models

Get started

Call Mammoth 1 through the Opper gateway with one API key. Evaluate state against typed questions using TypeSafe’s System One API for yes/no decisions, classification, and rubric scoring.

See the Opper evaluation guide and the TypeSafe API reference for question types and response formats. Compare every decision model, on one API.

Mammoth 1 is a premium model on Opper. Sign up needs no credit card: you get an API key straight away and the free models work in the playground and the API. Add a card to use premium models, pay-as-you-go with no minimum.

Set it up with your agent

Copy this and paste it into a coding agent like Claude Code, Cursor or Codex and it'll wire up Opper for you.

Or call it directly

1curl https://api.opper.ai/v3/compat/v1/systemone \
2  -H "Authorization: Bearer $OPPER_API_KEY" \
3  -H "Content-Type: application/json" \
4  -d '{
5    "model": "decisionmodels/s1-pro-5",
6    "state": "The customer cannot sign in and needs help immediately.",
7    "questions": {
8      "is_urgent": {
9        "type": "noul",
10        "instructions": "Does the customer need urgent help?"
11      }
12    }
13  }'