alexzhang0118/Decily-1.7B

Decily — calibrated candidate-scorer decision model

Decily scores a runtime-provided set of candidates against a state and a question, and returns a calibrated probability distribution over those candidates. It does not generate text. Decily is built for decisions where you want a probability you can threshold, not a sentence you have to parse.

Decily.decide(
    state="Our app crashes on startup after the latest update.",
    question="What is the customer's intent?",
    options=["technical", "billing", "shipping", "returns"],
)  # -> {"technical": 0.9999, "billing": 0.0001, "returns": 0.0, "shipping": 0.0}
# measured with the released weights (bf16, T=0.45)

This repository

PyTorch bf16 bundle (3.47 GB) of Decily-1.7B — the same tensors as the MLX bundle, in the training key layout (encoder.model.* backbone + pool.* / head.* scoring head).

File	Contents
model.safetensors	full model, bf16 (318 tensors)
config.json	Qwen3 architecture + decision_head spec
tokenizer.json, tokenizer_config.json, vocab.json	Qwen3 tokenizer

Load with the training repository's model class (arczhi/decily, see TRAINING.md §8):

from decision_model.models.cross_encoder import CrossEncoderConfig, CrossEncoderDecisionModel
# build with the config in this repo, then load_state_dict(model.safetensors, strict=False)

Model family

This card covers all four released artifacts; they are the same model in different containers.

Variant	Format	Size	Target
Decily-1.7B	PyTorch bf16 safetensors + config.json	~3.4 GB	server / GPU
Decily-MLX	MLX bf16 safetensors	~3.4 GB	Apple Silicon
Decily-MLX-4bit	MLX 4-bit (group-64 affine)	968 MB	on-device / low memory
Decily-ONNX-int8	ONNX int8 (single file)	1.66 GB	CPU / Windows / edge

Model details

• Model type: cross-encoder candidate scorer. The backbone encodes state + question + candidate jointly; an attention-pooling layer over all tokens feeds a LayerNorm/GELU MLP that outputs one logit per candidate. Probabilities come from the softmax over the candidates you pass in.
• Backbone: Qwen/Qwen3-1.7B-Base (1.72B parameters, Apache-2.0), with an attention-pooling scoring head (decision_head recorded in config.json; pool/head weights live in the checkpoint).
• Input limits (training configuration): state ≤256 tokens, question ≤96 tokens, each candidate ≤64 tokens, 2–16 candidates per call. Longer inputs are truncated — for long documents, chunk the state and score chunks separately (the cross-encoder logits are candidate-set independent, so chunked shortlisting then re-ranking is lossless; see the repository's two-stage inference utility).
• Precision: bf16 (PyTorch/MLX), 4-bit affine group-64 (on-device), int8 (ONNX).
• Temperature: raw logits are over-confident out of distribution. Fitted temperatures observed: ≈1.1 (in-domain), ≈0.45 on unseen label sets, ≈1.35 on the zero-shot fair suite. Always report/calibrate the temperature for your data (see Evaluation).

Training summary

Full, reproducible recipe: TRAINING.md in the training repository arczhi/decily (design rationale in DESIGN.md, all experiments and ablations in TRAIN-REPORT.md).

Stage	What	Notes
Teacher	45-task Qwen3.5-2B decision model (LoRA, frozen backbone)	reference labeler
SFT	Qwen3-1.7B LoRA on 24 task families (hard labels)	3000 steps ≈1 h
RLCD members	v1 / v2 LoRA + one full-FT member	belief calibration, abstention
Distillation	4-model probability-space ensemble → single full-FT student	KD T=2, α=0.5, +15% belief rows
v5 (this model)	full fine-tune, 3000 steps, effective batch 16, lr 1e-5, 8-bit AdamW	≈1.5 h on one RTX 5090 32 GB

Key recipe properties:

• Route B (explicit candidate scorer) beats the LM-head-letter-logits route (Route A) by +10.6 pt held-out accuracy in a controlled same-backbone test.
• Ensemble distillation: the 4-model ensemble reaches NLL 1.455; the distilled single model reaches 1.451 at 1× inference cost.
• Consumer hardware: the whole pipeline trains on a single RTX 5090 32 GB in well under a day.

Evaluation

Protocol: accuracy / NLL / ECE after temperature fitting (raw T=1 numbers are over-confident). "In-task" = the 24 trained task families; "held-out" = unseen label sets; "fair suite" = 8 tasks unseen by both this model and the external baseline.

Evaluation	Decily (24 tasks)	decider-2b (95 tasks)
In-task, 24 task families (shared training tasks)	0.863 / 0.390 / 0.034	0.811 / 0.453 / 0.032
Fair suite, zero-shot (8 tasks × 300)	0.654 / 0.86 / 0.092	0.700 / 0.71 / 0.047
Held-out label sets (60/77-class intents, 1200)	0.581 / 1.451 / 0.068	— (scores include tasks it was trained on)

Selective prediction (unseen label sets): taking only the most-confident 5% of predictions gives 93.3% accuracy (an SFT baseline with the same protocol gives 79%); abstention thresholds can be calibrated to a target error rate (empirically 4.7% achieved at a 5% target).

Honest reading of the numbers:

• Decily leads the larger, 95-task decider-2b by +5.2 pt on tasks both were trained on, at 1.7B vs 2B parameters and ~1/4 of the task coverage.
• On tasks neither model has seen, decider-2b leads by 4.6 pt; the gap is concentrated in knowledge-heavy tasks (sciq / pubmedqa / quality).
• The zero-shot gap is an efficiency result, not a ceiling: with this recipe, task coverage — not parameter count — is the documented main lever. Scaling the 24-task mixture toward 60–95 tasks with the same pipeline is expected to close and exceed the baseline (see TRAINING.md).

Uses

Direct use

• Classification / ranking / selection when the label set is known at runtime and may change per call (intents, topics, sentiment, NLI-style relations, multiple-choice answers, routing, moderation labels, tool selection).
• Calibration-sensitive automation: threshold the probability, auto-handle the confident head and escalate the rest to a human or a larger model.
• On-device / private inference: 968 MB 4-bit build, no GPU required.
• Synthetic decision data generation and reward/verifier scoring for LLM pipelines (it returns probabilities, not text).

Out of scope

• Text generation, chat, summarization.
• Open-ended label spaces (the candidate set must be provided at call time).
• High-stakes decisions without a calibrated threshold and human review.
• Very long inputs beyond the 256-token state window without chunking.

Quick start

Apple Silicon (MLX) — the standalone reference implementation ships with the training repository (mlx/decision_mlx.py, pure mlx.core, no torch):

python mlx/decision_mlx.py --model-dir <Decily-MLX dir> \
  --state "The invoice was paid twice..." \
  --question "What is the customer's intent?" \
  --options "billing,technical,shipping,returns" \
  --temperature 0.45

4-bit on-device: load the quantized tower with mlx_lm.load and apply the attention-pooling head from decision_head.safetensors (both files are in the repository; config.json records the head spec).

PyTorch: load model.safetensors + config.json with the training repository's model class; the checkpoint keeps backbone and head under their training key names (model.*, pool.*, head.*).

Limitations

• Task coverage: trained on 24 task families; zero-shot behavior on unseen domains trails a 95-task baseline (see Evaluation). Validate on your domain before trusting the probabilities.
• Calibration drift: the model needs temperature scaling; the fitted value depends on the data distribution (≈0.45–1.35 in our measurements).
• Input truncation: state is truncated at 256 tokens; long documents must be chunked (importance within a chunk, then combine).
• Language: training data is predominantly English (some multilingual intent data); other languages are untested.
• No safety layer: outputs are probabilities over the candidates you provide; the model does not refuse or filter inputs. Do not expose it as an autonomous decision-maker in safety-critical settings.
• Inherited biases: as a fine-tune of Qwen3-1.7B-Base on public datasets, it can reproduce biases present in those datasets (toxicity, sentiment and bias-classification tasks were part of the mixture, which reduces but does not eliminate this).

Environmental impact

Training used a single RTX 5090 32 GB: teacher ≈4 h, SFT ≈1 h, members ≈1 h, distillation ≈1.5 h (plus data conversion). Total well under 10 GPU-hours; no model was trained more than once per stage.

Citation and acknowledgements

• Backbone: Qwen3-1.7B-Base (Apache-2.0).
• The Route B formulation and the calibration/abstention pipeline build on the Decily line of work; the external baseline in the tables is Mapika/decider.
• If you use Decily, please cite this model card and link the training repository (TRAINING.md).