weird behavior with newline in arguments when script accepts `...args`

[haras-unicorn]

Bug report form

• I have done a basic search of the issue tracker to find any existing issues that are similar.
• I have checked that my version is at least the latest stable release available via my installation method.

Describe the bug

I am not quite sure if this is a bug but it caused me headaches that I don't know how to resolve.
So, apparently, when passing arguments containing newlines to a nushell script that accepts ...args, nushell interprets each line as its own command? I tried this with bash and bash seems fine with it even though I know nushell isn't really trying to do what bash does.

How to reproduce

1. Write nushell script like so and make it executable:

#!/usr/bin/env nu

def main [...args: string] {
  print ...($args)
}

2. Run ./test.nu a b "c\nd"
3. Error with output:

a
b
c
Error: nu::shell::external_command

  × External command failed
   ╭─[<commandline>:2:1]
 1 │ main a b c
 2 │ d
   · ┬
   · ╰── Command `d` not found
   ╰────
  help: Did you mean `cd`?

Expected behavior

I'd expect nushell to print normally and not error out.

With a script like so:

#!/usr/bin/env bash
echo "$@"

and invocation ./test.sh a b "c\nd" bash happily prints out:

a b c
d

. I know that technically when passing arguments like so to print it should print out probably something like

a
b
c
d

and not a b c on the same line as bash because I am using splatting. That being said, I was not expecting it to error out.

Configuration

key	value
version	0.111.0
major	0
minor	111
patch	0
branch
commit_hash
build_os	linux-x86_64
build_target	x86_64-unknown-linux-gnu
rust_version	rustc 1.93.0 (254b59607 2026-01-19) (built from a source tarball)
cargo_version	cargo 1.93.0 (083ac5135 2025-12-15)
build_time	1980-01-01 00:00:00 +00:00
build_rust_channel	release
allocator	standard
features	default, mcp, network, plugin, rustls-tls, sqlite, trash-support
installed_plugins
experimental_options	example=false, reorder-cell-paths=true, pipefail=true, enforce-runtime-annotations=false, native-clip=false

[fdncred]

I think the cause of this is this:

nushell/crates/nu-cli/src/eval_file.rs

Line 193 in 527ffa1

let args = format!("main {}", args.join(" "));

and when newline is in the args it comes out like this

main a b c
d

which the parser treats the second line as a command, and we get the error shown above.

[fdncred]

This is as close as I can get without changing a lot of stuff.

❯ /path/to/nu test.nu a b "c\nd"
a
b
"c
d"