REPL kernel session failure in Zed

[payam-delfi]

Using the latest Ark (v0.1.222) and Zed versions (v0.217.3), I am unable to start a REPL session in Zed:

Kernel process exited with status: Exit Status(unix_wait_status(6))

I thought it might be related to #788 but I'm not sure.

Running on M1 macOS Sonoma 14.8.1.

2025-12-19T16:49:14.724784Z ERROR  Panic! In file 'crates/harp/src/library.rs' at line 65: Can't determine if R shared library
path exists: Os { code: 20, kind: NotADirectory, message: "Not a directory" }
Backtrace:
0: std::backtrace::Backtrace::create
1: ark::main::{{closure}}::{{closure}}
2: ark::main::{{closure}}
3: std::panicking::panic_with_hook
4: std::panicking::panic_handler::{{closure}}
5: std::sys::backtrace::__rust_end_short_backtrace
6: __rustc::rust_begin_unwind
7: core::panicking::panic_fmt
8: harp::library::find_r_shared_library
9: harp::sys::unix::library::RLibraries::from_r_home_path
10: ark::interface::RMain::start
11: ark::start::start_kernel
12: ark::main
13: core::ops::function::FnOnce::call_once
14: std::sys::backtrace::__rust_begin_short_backtrace
15: std::rt::lang_start::{{closure}}
16: std::rt::lang_start_internal
17: std::rt::lang_start
18: _main
at crates/ark/src/main.rs:399

---

where ark
# /usr/local/bin/ark

ark --install
# Successfully installed Ark Jupyter kernelspec.
#    Kernel: /Users/Me/Library/Jupyter/kernels/ark/kernel.json

ark --version
# Ark 0.1.222

which jupyter
# jupyter not found

uv run --with jupyter jupyter kernelspec list
# Available kernels:
#  python3    /Users/Me/Library/Caches/uv/archive-v0/wyxicCr3T1uQ8DhQGSMNN/share/jupyter/kernels/python3
#  ark        /Users/Me/Library/Jupyter/kernels/ark

uv run python --version
# Python 3.12.10

Zed settings:

  "jupyter": {
    "enabled": true,
    "kernel_selections": {
      "python": "python3",
      "r": "ark",
    },
  },

[lionel-]

It looks like your R installation (as found via the R_HOME environment variable) does not feature a shared library (lib/libR.so, lib/libR.dylib, or lib/R.dll depending on platform). It seems that there is no lib folder. Or maybe R_HOME points to a totally invalid path.

How did you install R? Can you please reinstall it from a recommended source (e.g. from r-project.org or with rig https://github.com/r-lib/rig) and see if that resolves it?

[lionel-]

For copilot: Please send a PR addressing these two bullet points:

Around https://github.com/posit-dev/ark/blob/main/crates/ark/src/interface.rs#L555-L561

• We should check that the r_home path exists before trying to find the library. This way we can give a more accurate error message. This should happen before running the R command to get the paths.

• If the R command fails altogether, we should log an error message.

[payam-delfi]

Thanks, Lionel. I had installed R from https://cloud.r-project.org/ but had R_HOME set to "/usr/local/bin/R" in my .zshrc file.

I just reinstalled it again and updated R_HOME path. I can see libR.dylib (macOS, Apple chipset) is present:

> echo $R_HOME
/Library/Frameworks/R.framework/Resources

> ls -la $R_HOME/lib/libR.dylib
.rwxrwxr-x 5.2M root 31 Oct  2024 /Library/Frameworks/R.framework/Resources/lib/libR.dylib

However, I'm still getting the "Kernel process exited with status: Exit Status(unix_wait_status(6))" error.

I forgot how I was able to show the stack last time, so I am not sure if it's still due to the same R_HOME and shared lib issue.

[lionel-]

Can you please also do:

jupyter kernelspec list

Then cat the corresponding kernel file for R. E.g. for me:

cat /Users/lionel/Library/Jupyter/kernels/ark/kernel.json

You can probably just do this directly actually, especially if you don't have jupyter installed:

cat ~/Library/Jupyter/kernels/ark/kernel.json

Maybe there is an R_HOME overwrite in the env section.

[payam-delfi]

Definitely, please see the 3 outputs below.

> uv run --with jupyter jupyter kernelspec list
Installed 98 packages in 456ms
Available kernels:
  python3    /Users/me/Library/Caches/uv/archive-v0/f2RGiSmn4-wVJIDlrFFCW/share/jupyter/kernels/python3
  ark        /Users/me/Library/Jupyter/kernels/ark



> cat /Users/me/Library/Jupyter/kernels/ark/kernel.json
{
  "argv": [
    "/usr/local/bin/ark",
    "--connection_file",
    "{connection_file}",
    "--session-mode",
    "notebook"
  ],
  "display_name": "Ark R Kernel",
  "language": "R",
  "env": {
    "RUST_LOG": "error"
  }
}


> cat ~/Library/Jupyter/kernels/ark/kernel.json
{
  "argv": [
    "/usr/local/bin/ark",
    "--connection_file",
    "{connection_file}",
    "--session-mode",
    "notebook"
  ],
  "display_name": "Ark R Kernel",
  "language": "R",
  "env": {
    "RUST_LOG": "error"
  }
}

[lionel-]

With a recent version of Ark you might get more useful log output

[payam-delfi]

Thank you, I installed the latest version of Ark (0.1.228) and REPL in Zed is working now. Appreciate all the help!