Environment Management

Quick Guide: Per-app .env files. Framework-specific prefixes (

NEXT_PUBLIC_*

for Next.js,

VITE_*

for Vite). Zod validation at startup. Maintain .env.example templates. Never commit secrets (.gitignore). Environment-based feature flags.

<critical_requirements>

CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering,

import type

, named constants)

(You MUST validate ALL environment variables with Zod at application startup)

(You MUST use framework-specific prefixes for client-side variables -

NEXT_PUBLIC_*

VITE_*

(You MUST maintain .env.example templates with ALL required variables documented)

(You MUST never commit secrets to version control - use .env.local and CI secrets)

(You MUST use per-app .env files - NOT root-level .env files)

</critical_requirements>

Auto-detection: Environment variables, .env files, Zod validation, t3-env, @t3-oss/env, secrets management,

NEXT_PUBLIC_

VITE_

When to use:

• Setting up Zod validation for type-safe environment variables at startup
• Managing per-app .env files with framework-specific prefixes
• Securing secrets (never commit, use .env.local and CI secrets)
• Implementing environment-based feature flags

When NOT to use:

• Runtime configuration changes (use an external feature flag service)
• User-specific settings (use database or user preferences)
• Frequently changing values (use configuration API or database)
• Complex A/B testing with gradual rollouts (use a dedicated feature flag service)

Key patterns covered:

• Per-app .env files (not root-level, prevents conflicts)
• Zod validation at startup for type safety and early failure
• T3 Env pattern for Next.js/Vite projects (recommended)
• Framework-specific prefixes (

  NEXT_PUBLIC_*

  for client,

  VITE_*

  for Vite client)
• .env.example templates for documentation and onboarding

Detailed Resources:

• For code examples, see examples/ folder:
  • examples/core.md - Essential patterns (per-app .env, Zod validation)
  • examples/t3-env.md - T3 Env pattern for Next.js/Vite (recommended)
  • examples/naming-and-templates.md - Framework prefixes, .env.example
  • examples/security-and-secrets.md - Secret management
  • examples/feature-flags-and-config.md - Feature flags, centralized config
• For decision frameworks and anti-patterns, see reference.md

Philosophy

Environment management follows the principle that configuration is code -- it should be validated, typed, and versioned. The system uses per-app .env files with framework-specific prefixes, Zod validation at startup, and strict security practices to prevent secret exposure.

Core Patterns

Pattern 1: Per-App Environment Files

Each app/package has its own

.env

File Structure

apps/
├── client-next/
│   ├── .env                    # Local development (NEXT_PUBLIC_API_URL)
│   └── .env.production         # Production overrides
├── client-react/
│   ├── .env                    # Local development
│   └── .env.production         # Production overrides
└── server/
    ├── .env                    # Local server config
    ├── .env.example            # Template for new developers
    └── .env.local.example      # Local overrides template

packages/
├── api/
│   └── .env                    # API package config
└── api-mocks/
    └── .env                    # Mock server config

File Types and Purpose

1. .env

   - Default development values (committed for apps, gitignored for sensitive packages)

2. .env.example

   - Documentation template (committed, shows all required variables)

3. .env.local

   - Local developer overrides (gitignored, takes precedence over

   .env

   )

4. .env.production

   - Production configuration (committed or in CI secrets)

5. .env.local.example

   - Local override template (committed)

Loading Order and Precedence

Next.js loading order (highest to lowest priority):

1. process.env

   (already set in environment)

2. .env.$(NODE_ENV).local

   (e.g.,

   .env.production.local

   )

3. .env.local

   (not loaded when

   NODE_ENV=test

   )

4. .env.$(NODE_ENV)

   (e.g.,

   .env.production

   )

5. .env

Vite loading order:

1. .env.[mode].local

   (e.g.,

   .env.production.local

   )

2. .env.[mode]

   (e.g.,

   .env.production

   )

3. .env.local

4. .env

Exception: Shared variables can go in your build tool's env configuration for cache invalidation

See examples/core.md for complete code examples.

Pattern 2: Type-Safe Environment Variables with Zod

Validate environment variables at application startup using Zod schemas. Define a schema, parse at startup, export a typed

env

// lib/env.ts
const envSchema = z.object({
  VITE_API_URL: z.string().url(),
  VITE_API_TIMEOUT: z.coerce.number().default(DEFAULT_API_TIMEOUT_MS),
  VITE_ENABLE_ANALYTICS: z.stringbool().default(false), // Zod 4+ (NOT z.coerce.boolean())
});
export const env = envSchema.parse(import.meta.env);

Key gotchas:

• z.coerce.boolean()

  converts

  "false"

  to

  true

  (string is truthy) - always use

  z.stringbool()

  instead
• Use

  error.issues

  (not

  error.errors

  ) for Zod 4 error handling

Note: For Next.js/Vite projects, consider T3 Env (

@t3-oss/env-nextjs

or

@t3-oss/env-core

) for client/server variable separation and build-time validation. See examples/t3-env.md.

See examples/core.md for complete good/bad comparisons.

Pattern 3: Framework-Specific Naming Conventions

Use framework-specific prefixes for client-side variables and SCREAMING_SNAKE_CASE for all environment variables.

Mandatory Conventions

1. SCREAMING_SNAKE_CASE - All environment variables use uppercase with underscores
2. Descriptive names - Variable names clearly indicate purpose
3. Framework prefixes - Use

   NEXT_PUBLIC_*

   (Next.js) or

   VITE_*

   (Vite) for client-side variables

Framework Prefixes

Next.js:

• NEXT_PUBLIC_*

  - Client-side accessible (embedded in bundle) - use for API URLs, public keys, feature flags
• No prefix - Server-side only (database URLs, secret keys, API tokens)

Vite:

• VITE_*

  - Client-side accessible (embedded in bundle) - use for API URLs, public configuration
• No prefix - Build-time only (not exposed to client)

Node.js/Server:

• NODE_ENV

  - Standard environment (

  development

  ,

  production

  ,

  test

  )

• PORT

  - Server port number
• No prefix - All variables available server-side

See examples/naming-and-templates.md for complete code examples with good/bad comparisons.

Integration Guide

Core dependencies:

• Zod (v4+): Runtime validation and type inference for environment variables
• T3 Env (

  @t3-oss/env-nextjs

  ,

  @t3-oss/env-core

  ): Recommended wrapper for client/server separation

Framework support:

• Next.js: Automatic .env file loading with

  NEXT_PUBLIC_*

  prefix for client-side
• Vite: Automatic .env file loading with

  VITE_*

  prefix for client-side

Monorepo considerations:

• Declare shared env vars in your build tool's env configuration for cache invalidation
• Use per-app .env files even in monorepos to prevent conflicts

Replaces / Conflicts with:

• Hardcoded configuration values (use env vars instead)
• Runtime feature flag services for simple boolean flags (use env vars first, upgrade when needing gradual rollouts)

<decision_framework>

Decision Framework

See reference.md for complete decision frameworks including environment configuration and feature flag decisions.

</decision_framework>

<red_flags>

RED FLAGS

High Priority Issues:

• Committing secrets to version control (.env files with real credentials)
• Using environment variables directly without Zod validation (causes runtime errors)
• Using

  NEXT_PUBLIC_*

  or

  VITE_*

  prefix for secrets (embeds in client bundle)

Medium Priority Issues:

• Missing .env.example documentation (poor onboarding experience)
• Using production secrets in development (security risk)
• Root-level .env in monorepo (causes conflicts)

Gotchas:

• Next.js/Vite embed prefixed variables at build time, not runtime - requires rebuild to change
• Environment variables are strings - use

  z.coerce.number()

  for numbers, use

  z.stringbool()

  for booleans (Zod 4+)
• CRITICAL:

  z.coerce.boolean()

  converts "false" to

  true

  (string is truthy) - use

  z.stringbool()

  (Zod 4+) instead
• Empty string env vars are NOT

  undefined

  - use T3 Env's

  emptyStringAsUndefined: true

  option
• Monorepo build tool caches may NOT be invalidated by env changes unless declared in the tool's env configuration

See reference.md for complete RED FLAGS, anti-patterns, and checklists.

</red_flags>

<critical_reminders>

CRITICAL REMINDERS

All code must follow project conventions in CLAUDE.md

(You MUST validate ALL environment variables with Zod at application startup)

(You MUST use framework-specific prefixes for client-side variables -

NEXT_PUBLIC_*

VITE_*

(You MUST maintain .env.example templates with ALL required variables documented)

(You MUST never commit secrets to version control - use .env.local and CI secrets)

(You MUST use per-app .env files - NOT root-level .env files)

Failure to follow these rules will cause runtime errors, security vulnerabilities, and configuration confusion.

</critical_reminders>