sermilion/bill-feature-guard
skills/base/bill-feature-guard/SKILL.md
Enable feature flag mode - all code changes will be guarded by feature flags for safe rollback. Use when implementing new features that need gradual rollout, A/B testing, or safe rollback capability. Applies the Legacy pattern for large changes, factory/DI switching for medium changes, and simple conditionals for small changes. Use when user mentions feature flag, feature toggle, gradual rollout, safe rollback, or guard with flag.
$ install --global
skillsauthnpx skillsauth add sermilion/mobile-development-plugin bill-feature-guardInstall this skill globally with one command. Works with Claude Code, Cursor, and Windsurf.
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Last scanned: Apr 24, 2026, 8:46 PM1.8s1 file scanned
SKILL.md
- name:
- bill-feature-guard
- description:
- Enable feature flag mode - all code changes will be guarded by feature flags for safe rollback. Use when implementing new features that need gradual rollout, A/B testing, or safe rollback capability. Applies the Legacy pattern for large changes, factory/DI switching for medium changes, and simple conditionals for small changes. Use when user mentions feature flag, feature toggle, gradual rollout, safe rollback, or guard with flag.
Feature Guard Mode
Project Overrides
If .agents/skill-overrides.md exists in the project root and contains a ## bill-feature-guard section, read that section and apply it as the highest-priority instruction for this skill. The matching section may refine or replace parts of the default workflow below.
If an AGENTS.md file exists in the project root, apply it as project-wide guidance.
Precedence for this skill: matching .agents/skill-overrides.md section > AGENTS.md > built-in defaults.
Core Principles
North Star Goal: Single feature flag check to switch between old and new execution paths. Minimize flag usage by structuring code cohesively.
Rollback Guarantee: When the feature flag is OFF, the application MUST behave exactly as it did before any changes.
Cohesive New Code: Avoid sprinkling if (featureEnabled) checks throughout the codebase. Structure changes so flag decisions happen at the highest practical level.
Implementation Strategy
Step 1: Identify Scope
- What components/files will be affected?
- Can changes be isolated to a single entry point?
- What is the minimum number of feature flag checks needed?
Step 2: Choose Pattern Based on Change Size
- Small (1-2 files): simple conditional at the call site
- Medium (refactoring a component): new implementation alongside old, single switch point
- Large (multiple files, architectural): Legacy Pattern — rename to
*Legacy, create new, single flag check at routing level
See patterns.md for code examples and anti-patterns (DO/DON'T).
Step 3: Feature Flag Setup
- Naming: Follow project conventions (e.g.,
feature-[name],[platform]-[name]) - Default: Always
false(disabled) for new features - Type: REMOTE for production rollouts, LOCAL for dev/testing
- Documentation: Add clear description of what the flag controls
Checklist
- [ ] Can I isolate changes to minimize feature flag checks?
- [ ] Is the legacy path completely preserved?
- [ ] When flag is OFF, is behavior 100% identical to before?
- [ ] Are feature flag checks at the highest practical level?
- [ ] Is new code cohesive and self-contained?
When to Ask User
- Feature flag name: What should this feature flag be called?
- Scope clarification: If changes span many files, confirm the Legacy pattern approach
- Existing flags: Is there an existing flag that should be reused?
Session Behavior
For the remainder of this session:
- Every code change proposal MUST include feature flag strategy
- Show where the feature flag check(s) will be placed
- Identify what becomes Legacy vs New
- Confirm rollback safety before implementing
- Create/update feature flag definition in the codebase
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