Omnibus Instrument Feature Flags

PostHogOfficialCreated by PostHog

Skill
Tool integration
Data and AI
MIT
Low risk

From the author

Add PostHog feature flags to gate new functionality. Use after implementing features or reviewing PRs to ensure safe rollouts with feature flag controls. Also handles initial PostHog SDK setup if not yet installed.

— the description by PostHog

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured approach to instrumenting PostHog feature flags across a wide range of platforms and languages. It guides the user through detecting their current environment, setting up the PostHog SDK if necessary, and implementing the logic required to gate new functionality. By following these steps, developers can manage phased rollouts, target specific user groups, and perform multivariate testing without hardcoding sensitive configuration values.

What it does

Detects the project platform and framework to provide relevant SDK setup instructions.
Automates or guides the initialization of the PostHog SDK.
Provides standardized code patterns for evaluating boolean and multivariate feature flags.
Ensures secure configuration by enforcing the use of environment variables for API keys.
Supports a broad range of languages including Python, JavaScript, Go, Java, and mobile frameworks.
Offers guidance on best practices for feature flag implementation and lifecycle management.

When to use it

When you need to gate new features to perform a phased or canary rollout.
When you want to run A/B tests or experiments on specific user segments.
When you need to implement a kill-switch for new functionality in production.
When setting up PostHog for the first time in a new or existing codebase.

Advantages

Promotes safe deployment practices by decoupling code deployment from feature release.
Reduces risk by allowing immediate feature toggling without requiring a new deployment.
Supports consistent implementation patterns across diverse tech stacks.
Encourages secure development by prioritizing environment variables over hardcoded secrets.

Usage examples

“I want to gate my new checkout button with a PostHog feature flag in my React app.”: The agent will analyze your React project, verify the PostHog SDK installation, and provide the specific code snippet to wrap your component logic with a feature flag check.
“How do I set up PostHog feature flags in my Android project?”: The agent will guide you through adding the dependency to your build.gradle, initializing the SDK in your Application class, and implementing the flag evaluation logic.

Install

Download the skill as a ZIP:
https://mp-staging.autogineer.com/agent-skills/posthog/omnibus-instrument-feature-flags/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip omnibus-instrument-feature-flags.zip -d .agents/skills

Documentation by PostHog

Add PostHog feature flags

Use this skill to add PostHog feature flags that gate new or changed functionality. Use it after implementing features or reviewing PRs to ensure safe rollouts with feature flag controls. If PostHog is not yet installed, this skill also covers initial SDK setup. Supports any platform or language.

Supported platforms: React, Next.js, React Native, Web (JavaScript), Node.js, Python, PHP, Ruby, Go, Java, Rust, .NET, Elixir, Android, iOS, Flutter, and the REST API.

Instructions

Follow these steps IN ORDER:

STEP 1: Analyze the codebase and detect the platform.

Look for dependency files (package.json, requirements.txt, go.mod, Gemfile, composer.json, etc.) to determine the language and framework.
Look for lockfiles (pnpm-lock.yaml, package-lock.json, yarn.lock, bun.lockb) to determine the package manager.
Check for existing PostHog setup (SDK initialization, env vars, etc.). If PostHog is already installed and initialized, skip to STEP 3.

STEP 2: Research instrumentation. (Skip if PostHog is already set up.) 2.1. Find the reference file below that matches the detected platform — it is the source of truth for SDK initialization, flag evaluation methods, and framework-specific patterns. Read it now. 2.2. If no reference matches, fall back to your general knowledge and web search. Use posthog.com/docs as the primary search source.

STEP 3: Create or find the feature flag.

Check if a PostHog MCP server is connected. If available, use its tools to search for an existing feature flag the user wants to instrument, or create a new one.
If no MCP server is available, instruct the user to create the flag in the PostHog dashboard.

STEP 4: Plan release conditions.

Determine the rollout strategy (percentage rollout, user targeting, group targeting, etc.).
Plan how the feature flag will gate the new functionality in code.

STEP 5: Instrument the feature.

Add the feature flag code following the platform-specific reference patterns.
Use server-side evaluation when possible to avoid UI flicker.
Do not alter the fundamental architecture of existing files. Make additions minimal and targeted.
You must read a file immediately before attempting to write it.

STEP 6: Set up environment variables.

If an env-file-tools MCP server is connected, use check_env_keys to see which keys already exist, then use set_env_values to create or update the PostHog API key and host.
Reference these environment variables in code instead of hardcoding them.

Reference files

references/react.md - React feature flags installation - docs
references/react-native.md - React native feature flags installation - docs
references/web.md - Web feature flags installation - docs
references/nodejs.md - Node.js feature flags installation - docs
references/python.md - Python feature flags installation - docs
references/php.md - Php feature flags installation - docs
references/ruby.md - Ruby feature flags installation - docs
references/go.md - Go feature flags installation - docs
references/java.md - Java feature flags installation - docs
references/rust.md - Rust feature flags installation - docs
references/dotnet.md - .net feature flags installation - docs
references/elixir.md - Elixir feature flags installation - docs
references/android.md - Android feature flags installation - docs
references/ios.md - Ios feature flags installation - docs
references/flutter.md - Flutter feature flags installation - docs
references/api.md - API feature flags installation - docs
references/next-js.md - Next.js - docs
references/adding-feature-flag-code.md - Adding feature flag code - docs
references/best-practices.md - Feature flag best practices - docs

Each platform reference contains SDK-specific installation, flag evaluation, and code examples. Find the one matching the user's stack. If unlisted, use the API reference as a fallback.

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.

Files

ATTRIBUTION.mdAdded by AutoGineer966 B
LICENSELicence file added by AutoGineer1.0 KiB
SKILL.md4.7 KiB
references/adding-feature-flag-code.md108.7 KiB
references/android.md3.5 KiB
references/api.md5.6 KiB
references/best-practices.md7.9 KiB
references/dotnet.md6.8 KiB
references/elixir.md1.3 KiB
references/flutter.md5.9 KiB
references/go.md5.3 KiB
references/ios.md3.5 KiB
references/java.md2.3 KiB
references/next-js.md12.5 KiB
references/nodejs.md5.3 KiB
references/php.md4.6 KiB
references/python.md5.0 KiB
references/react-native.md4.3 KiB
references/react.md8.1 KiB
references/ruby.md4.9 KiB
references/rust.md4.3 KiB
references/web.md6.8 KiB

references/web.md

Web feature flags installation - Docs

Choose an installation method

Required

You can either add the JavaScript snippet directly to your HTML or install the JavaScript SDK via your package manager.

HTML snippet

Add this snippet to your website within the <head> tag. This can also be used in services like Google Tag Manager:

HTML

PostHog AI

<script>
    !function(t,e){var o,n,p,r;e.__SV||(window.posthog && window.posthog.__loaded)||(window.posthog=e,e._i=[],e.init=function(i,s,a){function g(t,e){var o=e.split(".");2==o.length&&(t=t[o[0]],e=o[1]),t[e]=function(){t.push([e].concat(Array.prototype.slice.call(arguments,0)))}}(p=t.createElement("script")).type="text/javascript",p.crossOrigin="anonymous",p.async=!0,p.src=s.api_host.replace(".i.posthog.com","-assets.i.posthog.com")+"/static/array.js",(r=t.getElementsByTagName("script")[0]).parentNode.insertBefore(p,r);var u=e;for(void 0!==a?u=e[a]=[]:a="posthog",u.people=u.people||[],u.toString=function(t){var e="posthog";return"posthog"!==a&&(e+="."+a),t||(e+=" (stub)"),e},u.people.toString=function(){return u.toString(1)+".people (stub)"},o="init os ds Ie us vs ss ls capture calculateEventProperties register register_once register_for_session unregister unregister_for_session ws getFeatureFlag getFeatureFlagPayload getFeatureFlagResult isFeatureEnabled reloadFeatureFlags updateFlags updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures on onFeatureFlags onSurveysLoaded onSessionId getSurveys getActiveMatchingSurveys renderSurvey displaySurvey cancelPendingSurvey canRenderSurvey canRenderSurveyAsync identify setPersonProperties group resetGroups setPersonPropertiesForFlags resetPersonPropertiesForFlags setGroupPropertiesForFlags resetGroupPropertiesForFlags reset get_distinct_id getGroups get_session_id get_session_replay_url alias set_config startSessionRecording stopSessionRecording sessionRecordingStarted captureException startExceptionAutocapture stopExceptionAutocapture loadToolbar get_property getSessionProperty bs ps createPersonProfile setInternalOrTestUser ys es $s opt_in_capturing opt_out_capturing has_opted_in_capturing has_opted_out_capturing get_explicit_consent_status is_capturing clear_opt_in_out_capturing cs debug M gs getPageViewId captureTraceFeedback captureTraceMetric Qr".split(" "),n=0;n<o.length;n++)g(u,o[n]);e._i.push([i,s,a])},e.__SV=1)}(document,window.posthog||[]);
    posthog.init('<ph_project_token>', {
        api_host: 'https://us.i.posthog.com',
        defaults: '2026-01-30',
    })
</script>

JavaScript SDK

Install the PostHog JavaScript library using your package manager. Then, import and initialize the PostHog library with your project token and host:

PostHog AI

npm

npm install posthog-js

yarn

yarn add posthog-js

pnpm

pnpm add posthog-js

JavaScript

PostHog AI

import posthog from 'posthog-js'
posthog.init('<ph_project_token>', {
    api_host: 'https://us.i.posthog.com',
    defaults: '2026-01-30'
})

2
Send events
Recommended
Once installed, PostHog will automatically start capturing events. You can also manually send events to test your integration:
Click around and view a couple pages to generate some events. PostHog automatically captures pageviews, clicks, and other interactions for you.
If you'd like, you can also manually capture custom events:
JavaScript
PostHog AI
```
posthog.capture('my_custom_event', { property: 'value' })
```

Use boolean feature flags

Required

Check if a feature flag is enabled:

if (posthog.isFeatureEnabled('flag-key')) {
    // Do something differently for this user
    // Optional: fetch the payload
    const matchedFlagPayload = posthog.getFeatureFlagPayload('flag-key')
}

Use multivariate feature flags

Optional

For multivariate flags, check which variant the user has been assigned:

if (posthog.getFeatureFlag('flag-key') == 'variant-key') { // replace 'variant-key' with the key of your variant
    // Do something differently for this user
    // Optional: fetch the payload
    const matchedFlagPayload = posthog.getFeatureFlagPayload('flag-key')
}

5
Use feature flag payloads
Optional
Feature flags can include payloads with additional data. Fetch the payload like this:
```
const matchedFlagPayload = posthog.getFeatureFlagPayload('flag-key')
```
6
Ensure flags are loaded
Optional
Every time a user loads a page, we send a request in the background to fetch the feature flags that apply to that user. We store those flags in your chosen persistence option (local storage by default).
This means that for most pages, the feature flags are available immediately — except for the first time a user visits.
To handle this, you can use the onFeatureFlags callback to wait for the feature flag request to finish:
```
posthog.onFeatureFlags(function (flags, flagVariants, { errorsLoading }) {
    // feature flags are guaranteed to be available at this point
    if (posthog.isFeatureEnabled('flag-key')) {
        // do something
    }
})
```
7
Reload feature flags
Optional
Feature flag values are cached. If something has changed with your user and you'd like to refetch their flag values:
```
posthog.reloadFeatureFlags()
```
8
Running experiments
Optional
Experiments run on top of our feature flags. Once you've implemented the flag in your code, you run an experiment by creating a new experiment in the PostHog dashboard.

Next steps

Recommended

Now that you're evaluating flags, continue with the resources below to learn what else Feature Flags enables within the PostHog platform.

Resource	Description
Creating a feature flag	How to create a feature flag in PostHog
Adding feature flag code	How to check flags in your code for all platforms
Framework-specific guides	Setup guides for React Native, Next.js, Flutter, and other frameworks
How to do a phased rollout	Gradually roll out features to minimize risk
More tutorials	Other real-world examples and use cases

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs an MCP server, Needs an API key, Needs Python, Needs Node.js

Security

What our scanner noticed· Low risk

Instructions that use the network

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Created by

PostHog

Publisher

PostHog (Official)

Source

PostHog/skills · skills/posthog/feature-flags/skills/all · commit a5d30e7

Licence

MIT License (redistribution allowed)

LICENSE (added by AutoGineer from LICENSE)
ATTRIBUTION.md (written by AutoGineer)

Synced

2026-11-08

Also distributed in

PostHog/skills

AutoGineer is not affiliated with or endorsed by PostHog.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download omnibus-instrument-feature-flags.zip

From the author

AutoGineer summary

What it does

When to use it

Advantages

Usage examples

Install

Documentation by PostHog

Add PostHog feature flags

Instructions

Reference files

Key principles

Files

references/web.md

Web feature flags installation - Docs

Choose an installation method

HTML snippet

JavaScript SDK

npm

yarn

pnpm

Send events

Use boolean feature flags

Use multivariate feature flags

Use feature flag payloads

Ensure flags are loaded

Reload feature flags

Running experiments

Next steps

Community questions

Was this page useful?

Requirements and compatibility

Security

Attribution and licence

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