Feature Flags Ruby

PostHog feature flags for Ruby

This skill helps you add PostHog feature flags to Ruby applications.

Reference files

• references/ruby.md - Ruby feature flags installation - docs

• references/adding-feature-flag-code.md - Adding feature flag code - docs

• references/best-practices.md - Feature flag best practices - docs

Consult the documentation for API details and framework-specific patterns.

Key principles

• Environment variables: Always use environment variables for PostHog keys. Never hardcode them.

• Minimal changes: Add feature flag code alongside existing logic. Don't replace or restructure existing code.

• Boolean flags first: Default to boolean flag checks unless the user specifically asks for multivariate flags.

• Server-side when possible: Prefer server-side flag evaluation to avoid UI flicker.

PostHog MCP tools

Check if a PostHog MCP server is connected. If available, look for tools related to feature flag management (creating, listing, updating, deleting flags). Use these tools to manage flags directly in PostHog rather than requiring the user to do it manually in the dashboard.

Framework guidelines

• posthog-ruby is the Ruby SDK gem name (add gem 'posthog-ruby' to Gemfile) but require it with require 'posthog' (NOT require 'posthog-ruby')

• Use PostHog::Client.new(api_key: key, host: host) for instance-based initialization in scripts and CLIs

• In CLIs and scripts: MUST call client.shutdown before exit or all events are lost

• Use begin/rescue/ensure with shutdown in the ensure block for proper cleanup

• capture and identify take a single hash argument: client.capture(distinct_id: 'user_123', event: 'my_event', properties: { key: 'value' })

• capture_exception takes POSITIONAL args (not keyword): client.capture_exception(exception, distinct_id, additional_properties) — do NOT use distinct_id: keyword syntax