feature-flags-architect

これはレビュー時に保存された抜粋です。完全で最新の内容は外部ソースを確認してください。

---
name: feature-flags-architect
description: 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.
context: fork
version: 2.9.0
author: claude-code-skills
license: MIT
tags: [feature-flags, progressive-delivery, rollout, kill-switch, launchdarkly, growthbook, statsig, unleash, flipt, release-engineering]
compatible_tools: [claude-code, codex-cli, cursor, antigravity, opencode, gemini-cli]
---

# Feature Flags Architect

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

## Core principle: flags are a lifecycle, not an `if`

```
request → design → ship → ramp → cleanup → archive
```

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

```bash
# 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.

```bash
python scripts/flag_debt_scanner.py --repo . --max-age-days 90 --format text
python scripts/flag_debt_scanner.py --repo . --max-age-days 60 --format json > debt.json
```

**Detection heuristic:**
1. Walk `--repo` for code references matching common flag-call patterns:
   - `flag("...")`, `isFlagEnabled("...")`, `featureFlag("...")`, `getFlag("...")`
   - `client.variation("...", ...)`, `unleash.isEnabled("...")`, `growthbook.feature("...")`
2. For each unique flag identifier, find the oldest commit that introduced it (`git log --diff-filter=A -S <name>`).
3. Flag as DEBT if introduced > `--max-age-days` ago AND used in ≤`--min-uses` places.

Outputs flag name, age in days, file references, suggested action. JSON mode is CI-friendly.

### `rollout_planner.py`

Generates a phased rollout schedule from population size,