feature-flags

name: feature-flags description: Creates and manages LaunchDarkly feature flags at SimplePractice. Use when the user needs to create, toggle, target, test, roll out, or clean up feature flags.

Feature Flags

Reference skill for LaunchDarkly feature flag workflows at SimplePractice. Feature flags decouple deployments from releases — they are if-else statements that control which users see which features.

Key Files

Naming Convention

• Prefix: feature_ — always
• Lowercase, underscore_case
• Verbose and specific to the feature, no abbreviations
• Examples: feature_new_payment_allocation, feature_client_demographics_report

Creating a Flag

1. Create in LaunchDarkly (Rails console)

LaunchDarklyScripts::CreateFeatureFlagService.new(
  flag_key: "feature_your_flag_name",
  description: "Product Owner: Name. Maintainer: Name. Description of the feature.",
  tags: [LaunchDarklyScripts::CreateFeatureFlagService::PRACTICE_MANAGEMENT_TAG]
).call

Available tags: GROWTH_TAG, RCM_TAG, PRACTICE_MANAGEMENT_TAG, MOBILE_TAG, CLINICAL_TAG

For Therapy Finder flags, add project_key: "monarch".

2. Register the flag

Add to app/models/concerns/ld_feature_flags.rb with fallback_value: false for new flags.

3. Expose to frontend (if needed)

Add to frontend/app/models/user.js. Flags not exposed on the API are unreachable from the frontend. Set frontend: false in ld_feature_flags.rb to hide from frontend API.

4. Create a cleanup Linear story immediately

Link it to the implementation story. Set expected removal date (30-60 days after 100% rollout).

5. Turn the flag on

LaunchDarklyScripts::ToggleFeatureFlagService.new(
  flag_key: "feature_your_flag_name",
  turn_flag_on: true,
  environment_key: "development" # "development", "staging", "production"
).call

Turning a flag on makes it usable — it does NOT set its value to true. Add targeting for that.

6. Add targeting

LaunchDarklyScripts::EnableForPracticesService.new(
  flag_key: "feature_your_flag_name",
  flag_value: true,
  practice_uuids: ["uuid1", "uuid2"]
).call

Rollout Process

1. Product finds early adopters, enables via admin console
2. Roll out to 1 test group, wait 24-48 hours
3. Expand test groups incrementally (new rule per expansion for scheduling)
4. Post to #product-releases at each milestone, thread replies
5. At 100%: update fallback_value: true in code within 1 week
6. After 30+ days at 100%: clean up the flag

Critical: Always update fallback_value: true when at 100% rollout. If LaunchDarkly goes down, flags revert to fallback — leaving it false hides shipped features. This caused the October 2025 outage.

Testing

RSpec

stub_flag(:feature_your_flag_name, true)

Local development

Option A: Toggle via admin dashboard

Option B: Create .ld_flag_overrides.yml in project root (auto-reloads):

feature_your_flag_name: true

A/B Testing

For detailed A/B testing setup, Mixpanel tracking, and Therapy Finder flags, see reference.md.

Flag Cleanup Checklist

- [ ] Feature stable at 100% for 30+ days
- [ ] fallback_value already set to true
- [ ] Remove flag from ld_feature_flags.rb
- [ ] Remove flag from frontend/app/models/user.js
- [ ] Remove all conditional logic (keep only "true" path)
- [ ] Remove stub_flag calls from tests
- [ ] Run full test suite
- [ ] Deploy to production
- [ ] Archive flag in LaunchDarkly
- [ ] Close cleanup Linear story

Tips

• Most customer-facing changes should be flagged — weigh risk vs cleanup effort
• Control one thing per flag
• Check the flag early in the flow, not deep in derived logic
• Ensure LaunchDarkly "Default rule" matches fallback_value in code
• Flags created in one environment exist in all environments automatically