Use when adding, retiring, or auditing feature flags. Triggers on "add a flag", "ship behind a flag", "rollout plan", "kill switch", "stale flags", "flag debt", "LaunchDarkly", "GrowthBook", "Statsig", "Unleash", "Flipt", or any progressive-delivery question. Ships flag debt scanner, rollout planner, and kill-switch auditor (all stdlib Python), 4 references on flag taxonomy + provider trade-offs + rollout strategies + lifecycle, plus a /flag-cleanup slash command.
Use when adding, retiring, or auditing feature flags. Triggers on "add a flag", "ship behind a flag", "rollout plan", "kill switch", "stale flags", "flag debt", "LaunchDarkly", "GrowthBook", "Statsig", "Unleash", "Flipt", or any progressive-delivery question. Ships flag debt scanner, rollout planner, and kill-switch auditor (all stdlib Python), 4 references on flag taxonomy + provider trade-offs + rollout strategies + lifecycle, plus a /flag-cleanup slash command.
End-to-end discipline for feature flags: classify them, ship them, ramp them, and retire them. Most teams treat flags as throwaway if-statements; this skill treats them as a controlled lifecycle with measurable debt.
When to use
Adding a new flag and need a rollout plan
Auditing a codebase for stale or orphaned flags
Choosing a flag provider (LaunchDarkly vs GrowthBook vs Statsig vs Unleash vs Flipt vs build-your-own)
Designing a kill-switch path for a risky launch
Cleaning up flag debt before a release freeze
Reviewing whether a feature should ship behind a flag at all
Flags that skip cleanup become debt: dead branches, stale defaults, untested code paths, unbounded blast radius. The three scripts in this skill enforce the lifecycle.
Quick start
# 1. Audit the repo for flag debt
python scripts/flag_debt_scanner.py --repo . --max-age-days 90
# 2. Plan a progressive rollout for a new flag
python scripts/rollout_planner.py --population 100000 --target-percent 100 --duration-days 14 --strategy ring
# 3. Verify every flag has a documented kill switch
python scripts/kill_switch_audit.py --repo . --flag-doc docs/feature-flags.md
The 4 flag types (taxonomy)
Different flag types have different lifespans and ownership. Misclassifying creates debt.
Type
Purpose
Typical lifespan
Owner
Cleanup trigger
Release
Hide unfinished features in production
days–weeks
Eng
100% rollout reached
Experiment
A/B test variants
weeks
Product/Marketing
Test concluded; winner picked
Operational
Circuit breakers, perf toggles, kill switches
months–years
Eng/SRE
Replaced by autoscaling/feature retirement
Permission
Entitlements per user/account/plan
years (permanent)
Product
Plan/role removed
Only Release and Experiment flags should be on a debt-scanner watchlist. Operational and Permission flags are by design long-lived. See references/flag_taxonomy.md for decision tree.
The 3 Python tools
All three are stdlib-only. Run with --help.
flag_debt_scanner.py
Finds flags older than --max-age-days with low usage, suggesting candidates for cleanup.
Self-hosting required (data residency / air-gapped) → Unleash or Flipt
See references/provider_comparison.md for detail.
Workflows
Workflow 1: Ship a new feature behind a flag
1. Classify: which of the 4 flag types?
→ Release (most common for engineering work)
2. Run rollout_planner.py to design the ramp
3. Add flag entry to docs/feature-flags.md BEFORE writing code:
- name, owner, type, kill-switch trigger, dashboard URL
4. Write the code with the flag
5. Run kill_switch_audit.py — must pass before merge
6. Deploy at 0%; verify kill switch works
7. Execute rollout schedule; abort if abort criteria met
8. At 100% for 7+ days: remove flag, delete dead branch, archive doc entry
Workflow 2: Quarterly flag cleanup
1. Run flag_debt_scanner.py --repo . --max-age-days 90 > debt.md
2. For each flagged item:
a. Confirm it reached 100% (or was killed)
b. Find the issue/PR that introduced it; verify owner agrees to remove
c. Delete dead branches; remove flag config
d. Run kill_switch_audit.py — should now show one fewer flag
3. Update CHANGELOG: "Removed N stale flags"
Workflow 3: Choose a provider
1. Estimate flag count (current + 12-month projection)
2. Required features:
- Targeting rules (user, account, geo, %)?
- A/B testing + stats?
- Audit log / SOC2?
- Self-hosting / data residency?
3. Pricing budget (MAU * cost-per-MAU)
4. See provider_comparison.md decision tree
5. Build a 30-day proof-of-concept before signing
Workflow 4: Design a kill switch
1. Identify the failure modes:
- Latency spike (which threshold?)
- Error rate spike (which threshold?)
- Business metric regression (which threshold?)
2. Wire each to an abort:
- Manual: dashboard link + on-call playbook
- Automated: alert threshold flips flag back to 0%
3. Test the kill switch in staging BEFORE production rollout
4. Document in flag-doc; pass kill_switch_audit.py
