Helix keybinding: copy file location + selected code for coding agents

[mtul0729]

I have been using a small Helix keybinding that has turned out to be very useful when working with coding agents.

The idea is simple: select some code, press a key, and copy both:

• the current file location, including line range
• the selected text, wrapped in a Markdown code fence

This makes it easy to paste precise context into ChatGPT, Codex, Claude, GitHub issues, or review comments.

For example, selecting a few lines and pressing Space l copies something like this:

src/main.rs:L42-L44
```
fn main() {
    println!("hello");
}
```

Space L does the same thing, but expands the file path to an absolute path.

Requirements

This depends on current Helix preview/master because it uses :set-register.

The keybinding also uses Helix expansion variables such as %{buffer_name}, %{selection_line_start}, %{selection_line_end}, and %{selection}.

I use Nushell as the editor shell so the small script can stay reasonably cross-platform:

[editor]
shell = ["nu", "-c"]

Configuration

[editor]
shell = ["nu", "-c"]

[keys.normal]

# Copy the current primary selection together with its relative file location.
space.l = [
  "extend_to_line_bounds",
  ''':set-register l %sh{
  let file = "%{buffer_name}"
  let start = ("%{selection_line_start}" | into int)
  let end = ("%{selection_line_end}" | into int)
  let first_line = ([$start, $end] | math min)
  let last_line = ([$start, $end] | math max)

  if $first_line == $last_line {
    print -n $"($file):L($first_line)"
  } else {
    print -n $"($file):L($first_line)-L($last_line)"
  }
}''',
  ''':set-register + %reg{l}
```
%{selection}```''',
  ":clear-register l",
]

# Same as Space-l, but expand the file location to an absolute path.
space.L = [
  "extend_to_line_bounds",
  ''':set-register l %sh{
  let file = ("%{buffer_name}" | path expand)
  let start = ("%{selection_line_start}" | into int)
  let end = ("%{selection_line_end}" | into int)
  let first_line = ([$start, $end] | math min)
  let last_line = ([$start, $end] | math max)

  if $first_line == $last_line {
    print -n $"($file):L($first_line)"
  } else {
    print -n $"($file):L($first_line)-L($last_line)"
  }
}''',
  ''':set-register + %reg{l}
```
%{selection}```''',
  ":clear-register l",
]

Notes

extend_to_line_bounds is intentional here. When I send code to an agent, I usually want complete lines rather than a partial character selection.

The temporary l register is only used to build the location string. The final result is written to the system clipboard register +, then the temporary register is cleared.

The relative-path version is better for repository-local discussion. The absolute-path version is useful when the receiving tool has access to the same local filesystem and can open the exact file directly.