support for fish

[jamesainslie]

I, and others, use fish. Which is not POSIX compliant, and there are some necessary changes for the underlying logic to work. I have implemented a PR 683

Specific Bash/Zsh Incompatibilities with Fish Shell

Based on the bash scripts in Spec Kit, here are the critical areas that would fail catastrophically in Fish Shell:

1. Variable Assignment Syntax
2. Command Substitution Syntax
3. Special Variables (BASH_SOURCE, $$, etc.)
4. Conditional Test Syntax
5. Array Syntax
6. Regex Matching with BASH_REMATCH
7. Error Handling (set -e, set -u, set -o pipefail)
8. Function Definition and Local Variables
9. eval with Output Capture
10. Here Documents and String Output
11. Arithmetic Expansion
12. Source/Sourcing Scripts
13. Argument Parsing

Summary: Why Fish Shell Support is Non-Trivial

These aren't minor syntax differences—they're fundamental incompatibilities requiring complete rewrites:

Area	Bash/Zsh	Fish	Complexity
Variable assignment	VAR=value	set VAR value	High
Arrays	arr=() arr+=(val)	set arr; set -a arr val	Very High
Conditionals	[[ ]]	test or string match	High
Regex	=~ with BASH_REMATCH	string match -r	Very High
Special vars	$$, BASH_SOURCE	$fish_pid, status filename	Medium
Functions	func() { }	function func; end	Medium
Error handling	set -e -u -o pipefail	Different model	High

[davidvartanian]

Fish support would be amazing, I also use Fish and I guess many others who haven't left feedback yet also do! 🙏

[github-actions]

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