[Bug]: "Transport became inactive" on 'container build' (0.5.0) – 16k limit on Container-files?

[srcshelton]

I have done the following

• I have searched the existing issues
• If possible, I've reproduced the issue using the 'main' branch of this project

Steps to reproduce

The container-file at https://github.com/srcshelton/docker-gentoo-build/blob/master/gentoo-base/Dockerfile.env is 19k in size. Attempting to container build it results in:

$ /usr/local/bin/container build --file Dockerfile.env --tag localhost/gentoo-env:latest . 
Error: unavailable (14): Transport became inactive

… but doing nothing other than removing commented lines (bringing the total size below 16k) proceeds to attempt to build the container image.

Current behavior

Container-files of over 16k in length appear to fail to transfer to the builder buildkit instance.

Expected behavior

Container-files of arbitrary length should be processed correctly (or, at least, a meaningful error message produced if any length-limit is exceeded).

Environment

- OS: macOS 26.0.1
- Xcode: Version 26.0.1 (17A400)
- Container: container CLI version 0.5.0 (build: release, commit: 48230f3)

Relevant log output

N/A

Code of Conduct

• I agree to follow this project's Code of Conduct

[wlan0]

Hi @srcshelton, thanks for the bug report.

I haven't confirmed it yet, but I believe this issue is due to GRPC header limit (16K default) and us sending the Dockerfile via GRPC header to the builder

container/Sources/ContainerBuild/Builder.swift

Line 313 in 7370923

("dockerfile", config.dockerfile.base64EncodedString()),

I'll confirm the issue and change the builder protocol to expect Dockerfile in a GRPC message instead of header

[blacktop]

bump

[danielweck]

Ah! :)
My 16+KB Dockerfile caused the obscure message Error: unavailable (14): Transport became inactive.
Easy fix as I was able to remove loads of line comments in order to decrease the file size.
May I suggest making the error message clearer?

[digitalpardoe]

I've just experienced this issue with a 28KB Dockerfile that can't really be trimmed down.

[deviantony]

I think I hit a similar issue with container 0.12.3 on macOS 26, except that I got a different error message:

$ container build --tag my-image:latest .
Error: unavailable: "Stream unexpectedly closed."

My Dockerfile failed at 425 lines (~15.4KB on disk, much of it inline comments and heredoc-formatted RUN blocks). After stripping inline comments to bring the file to ~400 lines, the build succeeds reliably.