@core / experiments

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1.0.1

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A/B tests with consent: stable assignment, conversion goals and results with significance, no extra cookies

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~601 tokens→ src/lib/experiments/AGENTS.md→ .cursor/rules/genpm-core-experiments.mdc

This is exactly what your AI reads when it works in src/lib/experiments. Nothing else is added to its context.

@core/experiments — rules for AI agents

Purpose

A/B tests that respect consent. Visitors who accepted analytics cookies get a stable variant (deterministic hash of the pseudonymous consent id, no extra cookie); everyone else always sees the control and nothing is stored. Conversions are recorded once per visitor and goal; results show rates, lift, p-value and a 95 % confidence interval (two-proportion z-test) and are frozen when the experiment stops. Tables: experiments, experiment_participants.

Map

index.ts — getVariant, recordConversion, upsertExperiment, setExperimentStatus, experimentResults, experimentsAdminResource, pruneExperimentsJob, compare.
react.ts — <Experiment name cookieHeader variants={{ a, b }} /> (server component).
stats.ts — statistics without dependencies. schema.ts — tables.

Integration

Requires @core/consent (the banner) and its cookie. Env: EXPERIMENTS_SECRET (≥ 32 random chars).
Migrations as in src/lib/db/AGENTS.md. Add experimentsAdminResource to src/genpm/admin.ts (with kit-landing: its "A/B tests (optional)" lines).
Create the experiment in the admin (key, goal, variants: the first is the control), then press "Start".
Render: const { variant } = await getVariant('hero-test', cookieHeader) (cookie header of the request) and show the matching content; or <Experiment name="hero-test" cookieHeader={…} variants={{ a: <A />, b: <B /> }} />.
Conversion: where the goal happens on the server, await recordConversion('lead', req.headers.get('cookie')).
Schedule experiments.prune daily (@core/jobs schedule) to delete participants 30 days after an experiment stops (with kit-cms, its setup-schedules.ts does it).
Verify: with analytics accepted the same browser always sees the same variant; with cookies rejected, always the control.

Conventions

Decide only when significant is true and the test ran at least one or two full weeks (weekday effects).
Change one thing per experiment; don't edit variants or weights while it runs (blocked; stop and create a new one).

Don't

Don't assign or record visitors without analytics consent, and don't store emails or ids in experiments.
Don't stop a test early because one variant "looks better" (peeking inflates false positives).
Don't use experiments to show different prices to different people.

# @core/experiments — rules for AI agents

## Purpose
A/B tests that respect consent. Visitors who accepted analytics cookies get a stable variant (deterministic hash of
the pseudonymous consent id, no extra cookie); everyone else always sees the control and nothing is stored.
Conversions are recorded once per visitor and goal; results show rates, lift, p-value and a 95 % confidence interval
(two-proportion z-test) and are frozen when the experiment stops. Tables: `experiments`, `experiment_participants`.

## Map
- `index.ts` — `getVariant`, `recordConversion`, `upsertExperiment`, `setExperimentStatus`, `experimentResults`, `experimentsAdminResource`, `pruneExperimentsJob`, `compare`.
- `react.ts` — `<Experiment name cookieHeader variants={{ a, b }} />` (server component).
- `stats.ts` — statistics without dependencies. `schema.ts` — tables.

## Integration
1. Requires @core/consent (the banner) and its cookie. Env: `EXPERIMENTS_SECRET` (≥ 32 random chars).
2. Migrations as in `src/lib/db/AGENTS.md`. Add `experimentsAdminResource` to `src/genpm/admin.ts` (with kit-landing:
   its "A/B tests (optional)" lines).
3. Create the experiment in the admin (key, goal, variants: the first is the control), then press "Start".
4. Render: `const { variant } = await getVariant('hero-test', cookieHeader)` (cookie header of the request) and show
   the matching content; or `<Experiment name="hero-test" cookieHeader={…} variants={{ a: <A />, b: <B /> }} />`.
5. Conversion: where the goal happens on the server, `await recordConversion('lead', req.headers.get('cookie'))`.
6. Schedule `experiments.prune` daily (@core/jobs `schedule`) to delete participants 30 days after an experiment stops
   (with kit-cms, its `setup-schedules.ts` does it).
7. Verify: with analytics accepted the same browser always sees the same variant; with cookies rejected, always the control.

## Conventions
- Decide only when `significant` is true and the test ran at least one or two full weeks (weekday effects).
- Change one thing per experiment; don't edit variants or weights while it runs (blocked; stop and create a new one).

## Don't
- Don't assign or record visitors without analytics consent, and don't store emails or ids in experiments.
- Don't stop a test early because one variant "looks better" (peeking inflates false positives).
- Don't use experiments to show different prices to different people.

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