environment-variables

Setup

If src/lib/env.ts does not exist, install dependencies and create the files before proceeding:

bun add @t3-oss/env-core zod

import { createEnv } from "@t3-oss/env-core";

export const env = createEnv({
  emptyStringAsUndefined: true,
  runtimeEnv: process.env,
  server: {},
});

// src/lib/env.test.ts
import { describe, expect, test } from "vitest";
import { env } from "./env";

describe("env", () => {
  test("initializes without error", () => {
    expect(env).toBeDefined();
  });
});

Variable Types

Type	Prefix	Exposed to client	Example
Client	VITE_	Yes	VITE_API_URL
Server	None	No	DATABASE_URL
Shared	None	Both (build-time)	NODE_ENV, DEV

Client = public endpoints, publishable keys, UI feature flags. Server = secrets, DB strings, internal URLs.

Environment Files

File	Purpose	Git
.env	Development defaults (local URLs, non-sensitive)	Committed
.env.local	Secrets, API keys, overrides	Ignored

Load order: .env.local overrides .env.

Adding a Variable

1. Add Zod schema to src/lib/env.ts in client, server, or shared
2. Development default → .env; secret → .env.local
3. Configure in deployment environment
4. Add validation test to src/lib/env.test.ts

Usage

import { env } from "@/lib/env";

Quick Reference

Task	Action
Access var	import { env } from "@/lib/env"
Client var	client section, VITE_ prefix
Server var	server section, no prefix
Shared var	shared section, build-time values
Validation	Zod schemas: z.string(), z.boolean(), etc.

Acceptance checklist

• src/lib/env.ts exists with t3-env + Zod config
• src/lib/env.test.ts exists with validation tests
• New variables added to correct section (client, server, shared)
• Defaults in .env, secrets in .env.local
• Deployment environment configured