Dev Containers: Environment variables from `devcontainer.json` not propagated to container

[vrognas]

System details:

Positron and OS details:

Positron Version: 2026.03.0 (user setup) build 123
Code - OSS Version: 1.108.0
Commit: 2faec0c
Date: 2026-02-19T08:36:08.027Z
Electron: 39.2.7
Chromium: 142.0.7444.235
Node.js: 22.21.1
V8: 14.2.231.21-electron.0
OS: Windows_NT x64 10.0.26200

Describe the issue:

No cap, I set some environment variables in devcontainer.json, but none were available from within the container. The image I'm using is a slightly customized image of a "rocker" image (https://rocker-project.org/).

Steps to reproduce the issue:

1. Drop this in devcontainer.json:

"containerEnv": {
    "FOO": "bar"
}

2. Yeet yourself into the container via Dev Containers: Reopen in Container
3. Run echo $FOO in the terminal
4. Watch it be completely empty and feel your soul leave your body 💀

Expected or desired behavior (the dream):

I lowkey expected echo $FOO to return bar. That's it frfr.

[midleman]

Thanks for the report, @vrognas! I was able to reproduce this.

I checked the generated build script (devcontainer-last-build.sh) and the docker create command is missing all the -e flags for your containerEnv variables - they're getting yeeted into the void before they even reach Docker.
This is a bug on our end frfr. We'll get it fixed. Thanks for reporting!

[jmcphers]

If you are blocked by this in any way, note that you can use remoteEnv and it should work (it's arguably what you should use unless you need the variable to build the container itself)

[testlabauto]

Verified Fixed

Positron Version(s) : 2026.03.0-212
OS Version          : OSX

Test scenario(s)

added:

"containerEnv": {
    "FOO": "bar"
}

to my decontainer.json.

After opening Positron in the container I was able to see FOO was set using the terminal.

Link(s) to test cases run or created: