Clef

About

Clef is a 27B multimodal decision model from Cloudflare, released on October 1, 2026 under the Apache-2.0 license. It turns a state plus a schema of typed questions into decisions: Clef reads the state as text, JSON, images, or video and returns a probability for every allowed option of every question in a single forward pass - there is no free-form text generation and no output parsing. The Clef API is fully compatible with Jev and SystemOne, and Clef is post-trained from Qwen/Qwen3.8-27B. A smaller, faster variant, Clef-Flash, is also available.

Architecture

Clef consists of the Qwen3.8-27B backbone with its vision encoder (stored as standard sharded safetensors, 27B parameters, BF16) plus a joint schema head - a small transformer head that reads the backbone's final hidden states, routes evidence from the state to each question, and scores all options of all questions jointly in a single forward pass. The output is one logit per allowed option for each question; a softmax per question gives probabilities. Qwen3.8-27B itself is a hybrid linear attention transformer: 64 layers in a 3:1 pattern of 48 linear-attention layers and 16 full-attention layers (gated linear attention with 16 key / 48 value heads at head_dim 128, GQA full attention with 24 query heads / 4 KV heads at head_dim 256, partial rotary factor 0.25, interleaved MRoPE with theta 1e7 and mrope_section [11, 11, 10]), hidden size 5120, intermediate size 17408, vocab 248320, native context 262144 tokens.

Input format and typed questions

A record contains a state (any string or JSON value), optional images/video frames, and a questions mapping. Each typed question declares its allowed answers up front via type (noul true/false, choice named options, or score ordered options), optional instructions, and criteria. encode_record bounds the input at a default max_length of 16,384 tokens (with max_state_tokens), and text-only and multimodal records can be mixed in one batch. The systemone function mirrors the Jev/SystemOne POST /v1/systemone endpoint and returns answers with choice/confidence/probabilities, expected score/legend/probabilities, or the probability of true for noul.

Training and deployment

Clef is post-trained from Qwen3.8-27B (card tag post-train), with the joint schema head trained alongside it; the card documents no post-training data or hyperparameters. Tested with torch 2.11 and transformers 5.10.2 on a single H200 (pillow needed for images/videos). Under the hood it leads Cloudflare's internal Decision Index 0.2.1 suite on routing/classification rows (ToolRet 69.2 nDCG@10, BANKING77 94.2 macro-F1, CLINC150+OOS 97.4, GSM8K 80.8, CRUXEval 86.7, RAGTruth 79.4) with a median latency of 209.3 ms, and leads four Typesafe Evals business workflows on invoice processing and security incidents.

Training Data Post-trained from Qwen/Qwen3.8-27B (with its vision encoder); no pretraining/post-training data recipe documented on the card.