Drift Detector

Drift Detector scores every assistant turn for how far it has wandered from the contract you set — a terse persona, hard length/format rules, an in-character voice — and quietly steers it back. A status-line badge shows live drift; the next prompt gets a one-shot correction nudge only when the previous reply broke contract. Deterministic, dependency-free, never touches your session's reliability.

Install

/plugin marketplace add 88plug/drift-detector
/plugin install drift-detector@drift-detector

Then enable the status-line badge (the one piece a plugin manifest can't auto-wire):

bash "$(/plugin path drift-detector)/install.sh"

Quickstart (under 60s)

Set a contract, work for a few turns, then check drift:

> from now on answer in caveman style: terse, no preamble, no hedging
> /drift:status

You'll see a live score and verdict, e.g. caveman | 12% | ok. When a reply relapses into "Certainly! I'd be delighted to walk you through this powerful, seamless solution…", the badge flips to DRIFT 98% and your next turn is quietly reminded to tighten up.

[!NOTE] F1=0.9973 on a 1,283-entry real-corpus (fp=0, tp=375, fn=2, tn=906). 190-session synthetic eval: 100% accuracy, FP=0. Adversarial test suite (37 cases targeting latent FP/FN patterns) included. A drift detector that cries wolf on clean work is worse than useless — the FP=0 constraint was held across every tuning lap without exception.

Why / who

For anyone who sets a strong output contract and watches the model erode it over a long session: persona work, strict formatting, compressed-output modes, in-voice scripts that must not break character. Drift is easy to feel and hard to name — the detector turns "it stopped listening" into a number you can see and act on, and acts on it for you, occasionally and proportionally, instead of nagging every turn.

Features

Feature	What it does
Per-turn scoring	Deterministic 0–100 drift score on every Stop
Morin trajectory	Scores drift as a vector — velocity and trend, not just level — so a self-correcting blip is tolerated and a slow climb is caught
Repeating-spike detection	Flags an oscillating relapse that looks adaptive turn-by-turn but is degenerative as a cycle
DCD pipeline	Deferred Correction Detection: scans N+1…N+10 for user correction follow-ups, improving recall on delayed feedback
ExtraTree classifier	ML stage (n=500, GroupKFold/5, t=0.58) stacked on the rule engine — catches patterns rules miss
Live badge	Status-line segment; composes with your existing statusline
One-shot nudge	Next prompt gets a correction reminder only when drifted, on a cooldown — never nags
Profiles	caveman, strict-instructions, persona, plus your own
MCP tools	drift_status, drift_recent, drift_explain (read-only)
Commands	/drift:status, report, profile, reset, debug

Metrics

Tuned through 21 scientific-method rounds on a 1,283-entry real-corpus extracted from production sessions:

Round	F1	Notes
R0	0.21	Baseline
R18	0.633	22-feature LR classifier
R19	0.9543	ExtraTree 43-feature + DCD steps=8
R20	0.977	11 new classify_user_reply patterns + DCD steps=10
R21	0.9973	17 patterns + exact-match gate + URL gate — ceiling reached

Two irreducible FNs remain: one credential provision in ok context and one bare "Try now" indistinguishable without session context. Precision = 1.000 (fp=0).

Commands

• /drift:status — live score, verdict, drift rate, trend.
• /drift:report — per-turn history plus the dominant offenders.
• /drift:profile [name|list|show] — switch or inspect the active profile.
• /drift:reset [session|all] — clear live state (or the rebuildable index).
• /drift:debug [on|off] — toggle structured hook logging.

How it works