MoonDriftKit

MoonDriftKit is a zero-dependency MoonBit library for deterministic streaming data-drift checks and histogram stability reports. It is intended for model input monitoring, telemetry-quality gates, experiment guardrails, and data pipeline regression checks.

Install

moon add liangjx987/moondriftkit

Minimal use

import "liangjx987/moondriftkit"

let spec = BucketSpec::new(0, 100, 5)
let baseline = Histogram::new(spec).add_many([42, 45, 48, 51, 54])
let current = Histogram::new(spec).add_many([70, 72, 75, 80, 86])
let report = compare_histograms(baseline, current)

assert_true(report.is_alert())
assert_eq(report.level_name(), "drift")

Histogram values are safe to retain as baselines: add returns a new value without changing the source histogram.

Verify from a clone

moon fmt --check
moon check --target all
moon build --target all
moon test --target all
moon info && git diff --exit-code -- '*.mbti'
moon run cmd/main

On toolchains that support the stricter flags, use moon fmt --deny-warn and moon info --deny-warn instead. MoonBit 0.10.4 uses the equivalent checked format and generated-metadata diff commands above.

Scope

• Equal-width integer bucket specifications and compact histograms.
• Deterministic basis-point drift scores and stable/watch/drift policies.
• Fixed-size recent-value windows and reproducible JSON reports.
• A runnable CLI demonstration under cmd/main.

MoonDriftKit deliberately does not implement ingestion, dashboards, model training, or a general dataframe engine. Those layers can consume the stable report exported by this package.

See README.mbt.md for API-oriented package documentation, docs/ACCEPTANCE.md for acceptance evidence, and LICENSE for the Apache-2.0 license text.