Blog / Questions / FIG. 52
Can Jev Replace My Trained Classifier? A Five-Minute Decision
The five-minute answer to replacing a trained ML classifier with Jev: when yes, when absolutely not, and the migration that keeps both honest.
Maybe, and the decision takes five minutes, not a quarter. The full analysis lives at LLM vs traditional ML; this is the executive cut for someone with a classifier in production and a tab open on Jev.
Keep the trained model, full stop, if any of these hold: you're classifying millions of items daily on categories that haven't changed in a year (microsecond inference at hardware cost wins); your signals aren't language (transaction graphs, sensor features: a language judge can't see your feature store); your latency floor is single-digit milliseconds; or an auditor needs deterministic, documented feature weights. Those are structural wins, not sentiment.
Replace it, or never build it, if the classifier is mostly a maintenance burden: categories drift with the product, retraining lags reality, the long tail of novel phrasing keeps leaking through, or you need ten more classifiers and can't staff ten more pipelines. Language-defined questions edit in minutes, handle phrasing your training set never saw, and cost reported fractions of a cent per verdict; the 500-emails-for-3.5-cents receipt is the reference economics.
The move most teams should actually make is neither: run both for two weeks. Route traffic through the incumbent, shadow-score with a Jev question set, and compare against ground truth, paying special attention to items outside the training distribution, which is where the gap lives. Then adopt the sequencing pattern: decision model as the fast-moving front line, trained model retained (or later re-trained on the decision model's own logged verdicts) only where volume and stability earn it. The shadow test costs an afternoon and pocket change; guessing costs a migration.
Frequently asked questions
Will accuracy drop if I switch?
On in-distribution stable categories, possibly slightly; on drifted and novel language, it typically rises. Your shadow comparison answers it for your data; nobody's blog can.
Do I lose explainability?
You trade feature weights for plain-language questions and per-choice probabilities, which non-ML stakeholders usually find more explainable. Regulated determinism needs stay with the trained model.
What's the cheapest way to test this?
A few hundred labeled historical items through a question set, per the getting-started ritual: one afternoon, verdicts scored against what your team actually did.
Numbers throughout are as reported by the build authors, not verified by shipwithjev. Code-shaped examples are pseudocode; the official docs live at docs.typesafe.ai.