InvariantOne

InvariantOne is a natural-language decision model that scores runtime-defined options directly rather than generating an answer token-by-token.

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Overview

Many LLM-based multi-option decision pipelines evaluate candidates jointly in a single prompt, using next-token logits, sequence scoring, or generated answer tokens. Joint candidate presentation can introduce option-order sensitivity, while exhaustive permutation symmetrization requires evaluating all $K!$ candidate orders.

InvariantOne resolves these problems architecturally:

1. Independent Branch Encoding: Each candidate choice $[S, Q, O_k]$ is processed independently through an adapted Qwen/Qwen3.5-4B-Base backbone.
2. Exact Distributional Permutation Equivariance: Pooled option representations pass into a direct comparative head (Projection: $\text{Linear}(2560 \to 256) \to \text{LayerNorm}(256)$; Absolute Scorer: $\text{Linear}(256 \to 256) \to \text{SiLU} \to \text{Linear}(256 \to 1)$), guaranteeing $\text{TVD} = 0.000000$ across all option permutations.
3. Calibrated Confidence: Output probabilities are normalized with a frozen temperature parameter ($\tau^* = 1.0091$).

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Architecture & Specifications

Component	Specification
Base Model	Qwen/Qwen3.5-4B-Base (32 transformer layers, $d_{\text{model}} = 2560$)
Backbone Status	Layers 0–27 strictly frozen (zero parameter updates)
LoRA Adaptation	Layers 28–30 (in_proj_qkv, out_proj) and layer 31 (q_proj, v_proj, o_proj); $r=8, \alpha=16$
Active LoRA Parameters	585,728 parameters
Readout Head	DirectComparativeHead: Projection (Linear(2560 → 256, bias=True) → LayerNorm(256)) + Absolute Scorer (Linear(256 → 256, bias=True) → SiLU → Linear(256 → 1, bias=True))
Active Head Parameters	722,177 parameters (frozen absolute_only inference mode: 656,128 projection + 66,049 scorer)
Auxiliary Stored Head Parameters	262,657 parameters (pair_net, stored in head.pt checkpoint but bypassed during v1 inference)
Total Stored Head Parameters	984,834 parameters (in checkpoint file head.pt)
Total Active Adapted Parameters	1,307,905 parameters (585,728 LoRA + 722,177 Head; <0.05% of base model)
Permutation Equivariance	Exact algebraic distributional invariance ($\text{TVD} = 0.000000$)
Calibration Temperature	$\tau^* = 1.0091$ (pre-calibrated temperature scaling)

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Installation

# Install from PyPI
pip install invariantone

# With optional HTTP server support
pip install "invariantone[server]"

# Or install from repository
git clone https://github.com/tradertanmay/InvariantOne.git
cd InvariantOne
pip install -e .

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Quickstart

from invariantone import InvariantOne

# Load frozen v1 checkpoint (auto-detects CUDA / Apple MPS / CPU)
model = InvariantOne.from_pretrained("invariantone-v1")

result = model.decide(
    state="Pressure is rising above the safe operating range.",
    question="What action should the controller take?",
    options=[
        "Close the inlet valve",
        "Increase feed pressure",
        "Maintain the current state",
        "Disable monitoring",
    ],
)

print(f"Selected: {result.choice}")
print(f"Index:    {result.choice_index}")
print(f"Probabilities: {[round(p, 4) for p in result.probabilities]}")

Output:

Selected: Close the inlet valve
Index:    0
Probabilities: [0.7952, 0.0389, 0.1547, 0.0112]

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Dynamic Options Count ($K \ge 2$)

Scope Note on Candidate Options Count ($K$):
The runtime supports arbitrary $K \ge 2$; the reported scientific evaluation results are for $K=4$ unless otherwise stated. Experimental generalization to arbitrary $K$ has not been independently established in the scientific benchmarks.

InvariantOne supports arbitrary numbers of runtime options:

# Binary decision (K=2)
binary_res = model.decide(
    state="High packet loss observed on eth0.",
    question="Should traffic fail over to eth1?",
    options=["Fail over to eth1", "Stay on eth0"],
)

# Multi-way decision (K=5)
multi_res = model.decide(
    state="Temperature at 520 C, cooling loop nominal.",
    question="Select operational mode:",
    options=[
        "SCRAM shutdown",
        "Engage loop B",
        "Adjust control rods",
        "Vent steam",
        "Maintain baseline",
    ],
)

---

Batch Decisions

Evaluate workloads with heterogeneous option counts:

results = model.decide_batch([
    {
        "state": "Disk usage at 98%.",
        "question": "Action:",
        "options": ["Purge logs", "Extend disk", "Ignore"],
    },
    {
        "state": "CPU nominal.",
        "question": "Action:",
        "options": ["Scale down", "Maintain size"],
    },
])

---

Command-Line Interface (CLI)

# Single decision (human-readable table)
invariantone decide \
  --state "Pressure is above limit" \
  --question "What should the system do?" \
  --option "Close inlet valve" \
  --option "Increase pressure" \
  --option "Maintain current state" \
  --option "Disable monitoring"

# Machine-readable JSON output
invariantone decide \
  --state "Pressure is above limit" \
  --question "What should the system do?" \
  --option "Close inlet valve" \
  --option "Increase pressure" \
  --json

# Verify checkpoint cryptographic integrity
invariantone verify

# Inspect model metadata
invariantone info

---

HTTP Inference Service

Run the local API service:

invariantone serve --port 8000

Execute inference via REST:

curl -X POST http://127.0.0.1:8000/v1/decide \
  -H "Content-Type: application/json" \
  -d '{
    "state": "Pressure is rising above the safe operating range.",
    "question": "What action should the controller take?",
    "options": [
      "Close the inlet valve",
      "Increase feed pressure",
      "Maintain the current state",
      "Disable monitoring"
    ]
  }'

---

Benchmark Performance Summary

Evaluated on FINAL-HOLDOUT-V2 ($1,536$ four-choice items) under strict preregistered one-shot governance:

Benchmark Provenance Note:
A100 performance figures are from the frozen FINAL-HOLDOUT-V2 benchmarking run; release-wheel functionality was independently smoke-tested in a fresh Python 3.12 environment.

Evaluation Stratum	Focus	Unadapted $D_0$	$B_1$-Raw	$B_1$-Sym ($24$-Perm)	InvariantOne-v1 (Seed 42)
FINAL-REAL	Real operational control tasks ($N=256$)	89.45%	91.41%	92.58%	94.14%
FINAL-L1	Familiar-Operator Compositional Recombination ($N=256$)	32.81%	38.28%	43.75%	89.84%
FINAL-L2a	Semantic Extrapolation ($N=256$)	28.12%	45.31%	50.39%	86.33%
FINAL-L2b	Relational Extrapolation ($N=256$)	22.27%	62.50%	65.23%	55.08%
FINAL-L3	Double Extrapolation ($N=512$)	25.20%	60.94%	65.43%	56.84%
Aggregate	Total locked holdout pool ($N=1,536$)	37.17%	59.90%	63.80%	73.18% (1,124/1,536)

Multi-seed aggregate mean across Seeds 42, 43, 44 is 71.74% ($\pm 1.97%$).

Permutation Equivariance: $\text{TVD} = 0.000000$ across all 24 permutations.
Inference Speedup: $5.08\times$ faster than 24-permutation symmetrized causal baseline ($83.71\text{ ms}$ vs $425.31\text{ ms}$ on A100).

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Known Boundaries & Model Limitations

1. Dynamic-$K$ Scientific Generalization: While the runtime supports arbitrary $K \ge 2$ and exact permutation equivariance holds algebraically, empirical benchmark accuracy ($94.14%$, $89.84%$, etc.) was evaluated on 4-choice tasks ($K=4$). Experimental generalization to arbitrary $K$ has not been independently established in the scientific benchmarks.
2. Novel Relational Operators: InvariantOne excels at familiar-operator recombination ($89.84%$) and semantic domain transfer ($86.33%$). However, completely unseen operator grammars drop to $55.08%$ ($L_{2b}$) and $56.84%$ ($L_3$), where 24-permutation causal averaging remains stronger ($65.43%$).
3. Top-1 Argmax Tie Breaking: While the output probability distribution is strictly permutation-equivariant ($\text{TVD} = 0.000000$), argmax top-1 selection exhibits a 1.56% flip rate under exact floating-point ties.
4. No Generative Explanations: InvariantOne is a dedicated decision model; it does not produce token-by-token natural-language rationales.
5. Confidence Estimates: Probabilities represent model confidence estimates and are not safety-critical certification guarantees.

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Documentation & Research

• GitHub Repository: https://github.com/tradertanmay/InvariantOne
• Hugging Face Model: https://huggingface.co/TanmaySah/InvariantOne-v1
• Model Card: model_card/MODEL_CARD.md
• Release Manifest: INVARIANTONE_V1_RELEASE_MANIFEST.json
• License Audit: RELEASE_LICENSE_AUDIT.md

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License

InvariantOne is licensed under the Apache 2.0 License. Base foundation model weights are licensed under the upstream Apache 2.0 license by Alibaba Cloud.