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Drift — AI Code Coherence Monitor

Signals Cheat Sheet

Signals Cheat Sheet¶

Quick reference for all drift signals.

★ = triggered especially often by AI-generated code
(R) = report-only signal (not included in drift score)

Scored Signals¶

Abbr	Signal	Weight	What it flags	Fix time
PFS ★	Pattern Fragmentation	0.16	Same concept implemented multiple incompatible ways in one module	30–90 min
AVS	Architecture Violation	0.16	Imports that skip layer boundaries; circular deps; blast-radius hubs	1–4 h
MDS ★	Mutant Duplicate	0.13	Near-identical functions (≥80% AST similarity) changed by copy-paste	15–60 min
EDS ★	Explainability Deficit	0.09	Complex functions (CC > 10) with no docstring, partial types, AI-attributed	20–45 min
SMS ★	System Misalignment	0.08	New code introduces deps/conventions not established in the module	30–90 min
BEM	Broad Exception Monoculture	0.04	Every handler catches `Exception` / bare `except:` and swallows it	15–30 min
TPD	Test Polarity Deficit	0.04	≥ 5 tests but zero negative / exception / boundary tests	30–60 min
DIA	Doc-Impl Drift	0.04	README/ADR claims that no longer match the actual import graph	30–90 min
NBV	Naming Contract Violation	0.04	`validate_` that never raises; `is_` that doesn't return bool	10–30 min
GCD	Guard Clause Deficit	0.03	Public functions skip input validation before business logic	20–45 min
BAT ★	Bypass Accumulation	0.03	`# noqa`, `# type: ignore`, TODO/HACK density > 5 % of LOC	30–180 min
ECM	Exception Contract Drift	0.03	Exception profile changed across commits; callers silently broken	30–90 min
COD	Cohesion Deficit	0.01	Module/class bundles unrelated responsibilities	1–3 h
CCC	Co-Change Coupling	0.005	File pairs almost always changed together — hidden coupling	30–90 min
FOE	Fan-Out Explosion	0.005	Module imports far more than the repo median	1–3 h
MAZ	Missing Authorization	0.02	HTTP endpoints without auth check (CWE-862)	15–30 min
ISD	Insecure Default	0.01	`DEBUG=True`, `ALLOWED_HOSTS=['*']` etc. (CWE-1188)	5–20 min
HSC	Hardcoded Secret	0.01	Credentials or tokens in source code (CWE-798)	5–15 min
PHR	Phantom Reference	0.02	References to functions/modules that no longer exist	15–30 min

Report-Only Signals¶

Abbr	Signal	What it flags	Fix time
TVS (R)	Temporal Volatility	Files with z-score change frequency far above peers	1–4 h
TSA (R)	TypeScript Architecture	Layer leaks and cycles in TS/JS code	30–90 min
CXS (R)	Cognitive Complexity	Functions with excessive nesting depth	30–90 min
CIR (R)	Circular Import	Import cycles of any length	30–90 min
DCA (R)	Dead Code Accumulation	Defined symbols never referenced elsewhere	15–30 min

Exploring a signal¶

drift explain PFS                    # description + example + fix hint
drift explain PFS --repo-context     # examples from your own codebase
drift explain --list                 # this table in the terminal

If you see…	Also check…	Reason
PFS	MDS, SMS	Fragmentation clusters with duplication and style drift
AVS	COD, CCC	Layer violations reveal cohesion and coupling problems
EDS	TPD, BEM	Explainability and test/error-handling quality move together
HSC	ISD, MAZ	Security signals cluster — fix all three at once
BEM	ECM, TPD	Exception handling issues compound each other

Score context by profile¶

Profile	Typical first-run range	Healthy target
`vibe-coding`	0.20–0.50	< 0.35
`default`	0.25–0.55	< 0.40
`strict`	0.30–0.65	< 0.45

Run drift setup to activate the right profile for your project.