drift-canary

name	drift-canary
description	Compatibility and schema drift canary — checks for database schema migration safety, breaking API contract changes, serializable payload mismatches, and backward compatibility drift. Triggers on keywords: "/drift-canary", "drift-canary", "contract drift", "breaking changes". Use when changing DB schemas, API contracts, serialized payloads, or required config keys.

Drift Canary (Contract & Schema Drift Audit)

Audit code to ensure changes do not break backward compatibility or cause database/API mismatches.

Auditing Categories

1. Breaking Schema Migrations — dropping columns, changing types, or adding non-null columns without defaults (crashes on deploy).
2. API Contract breaking changes — modifying existing REST/GraphQL properties, removing endpoints, or adding required query fields that break old clients.
3. Serialization mismatches — editing properties in serialized payloads (JSON, Protobuf, XML) without deserialization fallbacks.
4. Library Contract Drift — changing a public method signature in a shared library without a deprecated wrapper.
5. Environment Configuration drift — introducing new required config keys (.env / OS vars) without defaults or fallback.

Expand/contract migration rules, per-format serialization fallbacks, and the breaking-vs-additive API checklist: read references/checks.md before scanning.

Scope: honor .coalmine.json schemaPaths / migrationDirs if set — scan those globs/dirs; else infer by inspecting the repo.

Discipline

• Style Drift Resolution (Fix mode): when an approved fix touches mixed-style code, conform the minority patterns to the dominant style (highest average usage) to minimize churn — never start a standalone style refactor.

Fix mode (choice-gated)

In Agent Context, after the report, present via ask_question:

• Apply safe deprecations: mark endpoints/methods deprecated + add backward-compatibility mapping wrappers. Each fix: checkpoint (git stash/commit in a git repo; else copy the file aside — never assume git) → apply → build + tests → auto-revert if newly red.
• Let me pick: user selects specific compatibility fixes.
• Report only: exit unchanged.

Output

| file:line | contract interface | severity | finding | migration path |

Severity: CRITICAL (breaking DB schema mutation / breaking API change) · HIGH (serialization type change) · MEDIUM (unmapped new required env key) · LOW (missing deprecation doc)