`try init` returns bash syntax under fish when $SHELL is not fish

What happens

I use fish, but my login shell is zsh, so $SHELL is /bin/zsh. try init returns the bash function instead of the fish function. The README line then fails:

❯ try init "$HOME/tries" | source
- (line 1): command substitutions not allowed in command position. Try var=(your-cmd) $var ...
try() {
   ^^
from sourcing file -
source: Error while reading file '<stdin>'

Cause

cmd_init! picks the syntax with fish? (try.rb:1281 on main):

shell = fish? ? 'fish' : 'bash'

fish? reads $SHELL first (try.rb:1646):

def fish?
  shell = ENV["SHELL"].to_s
  if shell.empty?
    shell = (`ps c -p #{Process.ppid} -o 'ucomm='`.strip rescue "").to_s
  end
  shell.include?('fish')
end

The parent process check runs only when $SHELL is empty. $SHELL holds the login shell, not the shell that runs the command. Any user who starts fish from a different login shell gets bash syntax.

The existing fallback already works

The parent process check detects fish correctly. It is only unreachable. With $SHELL removed, try init returns the fish function:

❯ env -u SHELL try init "$HOME/tries" | head -2
function try
  set -l out (/usr/bin/env ruby '.../try.rb' exec --path '/Users/samedwardes/tries' $argv 2>/dev/tty | string collect)

This also works through the Homebrew wrapper at /opt/homebrew/bin/try. The wrapper uses exec, so the Ruby process keeps fish as its parent.

Suggested fix

Check the parent process first in fish?, then fall back to $SHELL. The parent process is the shell that reads the output of try init.

A --shell flag on try init would also help. It makes the choice explicit and testable.

detect_shell (try.rb:1331), which try install uses, has the same $SHELL-first order. Reading $SHELL there is defensible, because install writes to the rc file of the login shell.

Workaround

env SHELL=(status fish-path) try init "$HOME/tries" | source

Environment

• try 1.10.1 (Homebrew). Confirmed on main at try.rb:1281 and try.rb:1646.
• fish 4.8.1
• macOS 26.6.2, Apple Silicon
• $SHELL=/bin/zsh, login shell zsh

Start in try.rb at cmd_init! around line 1281 and fish? around line 1646; inspect how shell detection chooses between fish and bash. Run try init from fish with $SHELL set to zsh, then repeat with $SHELL unset to compare the generated output. Done means the command selects fish syntax based on its parent shell while preserving the existing fallback behavior.