Start not loading environment variables from .env.*

Open

#6,052 opened on Dec 9, 2025 6 comments 8 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Dominant language: TypeScript
Stars: 15.1k
Forks: 1.9k
Avg merge: 1d 20h
Merged PRs (30d): 143

Description

Which project does this relate to?

Start

Describe the bug

Environment variables from .env.development aren't being loaded and merged with .env.

This might be related to #5217.

Your Example Website or App

https://github.com/Benjamin-Lee/tanstack-start-env

Steps to Reproduce the Bug or Issue

Clone the repo and install dependencies
Run npm run dev or bun run dev (don't run bun --bun run dev since that uses Bun's environment loader)
Take a look at localhost:3000

Expected behavior

On localhost, we'd expect to see:

SECRET: foo
EXAMPLE: bar

Screenshots or Videos

Platform

Router / Start Version: 1.140.0
OS: macOS
Browser: N/A
Browser Version: N/A
Bundler: vite
Bundler Version: 7.2.7

Additional context

No response

Contributor guide

Open the contributing guide

First steps

Read the whole issue, then the project's contributing guide.
Comment on the issue to say you are picking it up — it saves two people doing the same work.
Fork the repository and make your change on a branch.
Open a pull request that references the issue number.

Research direction

Reproduce the issue from the linked example by installing dependencies and running npm run dev or bun run dev, then compare the values loaded from .env and .env.development at localhost:3000. Locate the Start environment-loading entry point and add coverage for merging .env.* variables; done means the example displays SECRET: foo and EXAMPLE: bar.

Written by the indexing model from the issue text.

Assessment

Tech stack: typescript, vite
Domain: build-system
Issue type: Bug
Difficulty: 3/5
Estimated time: 1-2 days
Activity status: Quiet
Clarity: Mostly clear
Newbie friendliness: 55/100