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Statistical rigor, your credit policy, and an explanation you can audit.

Underwrite.ai hybrid models combine three purpose-built components: a gradient boosting machine for predictive power, a deterministic rule layer that encodes your policy, and a large language model that explains every outcome — without ever making the decision.

Start for Free See the architecture

One application flows through three layers.

Each layer does one job well. The score comes from statistics, the decision comes from your policy, and the explanation comes from language — kept strictly separate so responsibility is never blurred.

01 · Decision Core

Gradient Boosting Machine

Produces the risk score. Nonlinear, high-accuracy, and idempotent — identical inputs always yield an identical, reproducible result.

02 · Policy Layer

Credit Policy Rules

Makes the decision. A transparent, editable rule layer applies your cutoffs, overlays, and hard constraints on top of the score.

03 · Explanation

LLM Explainer

Explains the decision. Translates feature attributions and rule triggers into plain-language rationale and adverse-action reasons — read-only.

The score is statistical. The decision is your policy. The LLM only explains — it never decides.

The strengths of each, none of the weaknesses.

Reproducible by design

The GBM is idempotent: rerun the same application and you get the same score, every time. No drift, no randomness in the number your decision rests on.

Your policy, encoded

The rule layer keeps credit policy where it belongs — with you. Adjust cutoffs and overlays without retraining, and know exactly why each rule fired.

Explanations, not black boxes

Every decision arrives with a plain-language rationale grounded in real feature attributions — ready for applicants, reviewers, and regulators alike.

The LLM explains. It never decides.

We deliberately keep the language model out of the credit decision. It receives the score and the rules that fired — then writes the explanation. It cannot change an outcome, override a rule, or introduce a factor the model didn't use.

That separation is what makes the explanation trustworthy: it describes a decision that was already made by deterministic, auditable components — not a story generated after the fact.

GBM Risk score: 0.82 — low probability of default
Policy Passes cutoff (≥ 0.70) · No overlays triggered → Approve
LLM “Approved. The strongest positive factors were consistent cash-flow coverage and low revolving utilization; no policy overlays applied.”
Read-only — the explanation cannot alter the decision above.

Auditable at every layer.

Because scoring, policy, and explanation are separate and deterministic, every decision can be reconstructed end to end — the exact score, the rules that applied, and the reasons given. Fully aligned with FCRA adverse-action requirements and fair-lending review.

Custom nonlinear models

See a hybrid model on your data.

Send us your loan tape and we'll build a custom hybrid model — scored by a GBM, governed by your policy, explained in plain language.