Feature Flags Authoring

Feature Flags Authoring

A developer how-to for the full lifecycle of a Packmind feature flag: add, edit, remove. Flags gate a feature by email domain (or exact email). The same decision function runs on frontend and backend, so behavior never diverges. Follow the steps below exactly — every flag touches three places.

For inventorying existing flags, orphan detection, and audience audits, use the feature-flags-audit skill instead. This skill changes flags; that one scans them.

Where things live

• Shared registry — @packmind/feature-flags (pure, env:shared, browser-safe). The single source of truth:
  • registry.ts — the *_FEATURE_KEY constants, DEFAULT_FEATURE_DOMAIN_MAP (Record<string, readonly string[]> mapping each flag's string value to allowed entries), and the FeatureFlagKey union.
  • isFeatureFlagEnabled.ts — the pure evaluator: isFeatureFlagEnabled({ featureKeys, featureDomainMap, userEmail }).
• Frontend gate — <PMFeatureFlag> from @packmind/ui (or a direct isFeatureFlagEnabled(...) call). The keys, DEFAULT_FEATURE_DOMAIN_MAP, and isFeatureFlagEnabled are re-exported from @packmind/ui for back-compat, so existing consumers can import from either place.
• Backend gate — isFeatureEnabled(flag, { userEmail }), a plain async helper from @packmind/node-utils. It resolves the env kill-switch first, then defers to the shared email-domain rule. It is NOT a port and has no DI — import it and call it.
• Env kill-switch — FF_<SCREAMING_SNAKE> (e.g. FF_CHANGE_PROPOSALS_IN_WEBAPP). on/all/true force the flag on; off/none/false force it off; unset or empty falls through to the email-domain map.

Two flags exist today: 'change-proposals-in-webapp' and 'orga-space-management'.

Add a flag

1. Register it in @packmind/feature-flags

Add the key constant, the audience entry, and extend the union. Do all three — a constant with no map entry is never enabled for anyone; a map entry with no union member can't be typed at call sites.

// registry.ts
export const MY_FEATURE_KEY = 'my-feature' as const;

export type FeatureFlagKey =
  | 'change-proposals-in-webapp'
  | 'orga-space-management'
  | 'my-feature';

export const DEFAULT_FEATURE_DOMAIN_MAP: Record<string, readonly string[]> = {
  // ...
  'my-feature': ['@packmind.com'], // domains keep the `@`; exact emails have no leading `@`
};

2. Gate the frontend

Wrap the UI that should appear only when the flag is on:

import { PMFeatureFlag } from '@packmind/ui';
import { MY_FEATURE_KEY, DEFAULT_FEATURE_DOMAIN_MAP } from '@packmind/feature-flags';

<PMFeatureFlag
  featureKeys={[MY_FEATURE_KEY]}
  featureDomainMap={DEFAULT_FEATURE_DOMAIN_MAP}
  userEmail={currentUser.email}
>
  {/* gated UI */}
</PMFeatureFlag>

For a branch (route, tab, boolean), call isFeatureFlagEnabled({ featureKeys: [MY_FEATURE_KEY], featureDomainMap: DEFAULT_FEATURE_DOMAIN_MAP, userEmail }) directly.

3. Gate the backend

Inside a member use case, command.user.email is available. Branch on the helper:

import { isFeatureEnabled } from '@packmind/node-utils';
import { MY_FEATURE_KEY } from '@packmind/feature-flags';

if (await isFeatureEnabled(MY_FEATURE_KEY, { userEmail: command.user.email })) {
  // new path
} else {
  // old path
}

4. (Optional) Env override

Set FF_MY_FEATURE=on to force the flag on everywhere, or FF_MY_FEATURE=off to force it off, regardless of the domain map. Leave unset to defer to the map. Document the var in the deploy config if you rely on it.

Edit a flag

Change the allowed audience in DEFAULT_FEATURE_DOMAIN_MAP — add or remove domains (@company.com) or exact emails (user@company.com). This is the only place audience lives; the frontend and backend both read it.

Remember: the FF_* env kill-switch overrides the map at runtime. If a flag looks stuck on or off in an environment, check the env var before editing the map.

Remove a flag

1. In @packmind/feature-flags: delete the *_FEATURE_KEY constant, its DEFAULT_FEATURE_DOMAIN_MAP entry, and its FeatureFlagKey union member.
2. Delete every call site:
   • Frontend: remove the <PMFeatureFlag> wrappers (keep the children — the UI ships unconditionally now) and any isFeatureFlagEnabled branches.
   • Backend: remove the isFeatureEnabled branches, keeping the winning branch inline.
3. Drop any FF_<SCREAMING_SNAKE> env var from deploy config.
4. Run the feature-flags-audit skill to confirm no orphaned keys, map entries, or call sites remain.

Conventions

• Audience is email-domain only (Proposal A). No org, plan, team, or percentage targeting exists yet — do not describe or build it.
• Never log an email in clear text. If you log a flag decision, mask the email (first 6 chars + *) or, better, log only the flag key and the boolean outcome.
• Keep @packmind/feature-flags pure and browser-safe. No env:node imports (no @packmind/node-utils, no Configuration.getConfig, no process.env). It ships to the browser bundle.
• The backend gate is a plain helper call, not an injected port. Import isFeatureEnabled and call it directly; do not add a port/adapter/registry.

See also

• feature-flags-audit — the review/scan counterpart: inventories every flag, its audience, its usages, and flags orphans. Run it after removing a flag and whenever you need the current state of the system.