Per-directory terminal colors in fish shell

My terminal background color changes based on the current directory. It's a small touch that makes it easy to tell which project I'm in at a glance, which is especially useful when juggling AI agents.

It works via a custom fish function called _color_for_dir, which:

Hashes the current $PWD
Maps the hash to a hue (0-359)
Converts it to a dark RGB color
Sends an OSC 11 escape sequence to change the terminal background

# Hash the directory name to a hue
set -l hash (echo -n "$PWD" | md5 | tr -d 'a-f ' | cut -c1-8)
set -l hue (math "$hash % 360")

# ... HSL to RGB conversion ...

printf '\e]11;#%02x%02x%02x\a' $ri $gi $bi

It's deterministic, so each directory always gets the same color. The function is triggered on startup and on every cd via a --on-variable PWD event listener.

It also skips VS Code's integrated terminal because I generally know what projects I have open

Full code:

Click to expand

function _claude_color_for_dir
    # Skip in VS Code's integrated terminal
    if test "$TERM_PROGRAM" = vscode
        return
    end

    # Hash the directory name to a hue using MD5 for better distribution
    set -l hash (echo -n "$PWD" | md5 | tr -d 'a-f ' | cut -c1-8)
    set -l hue (math "$hash % 360")

    # Convert hue to a dark but visible RGB (HSL with S=0.7, L=0.18)
    set -l s 0.7
    set -l l 0.18
    set -l c (math "$s * (1 - abs(2 * $l - 1))")
    set -l h (math "$hue / 60")
    set -l x (math "$c * (1 - abs($h % 2 - 1))")
    set -l m (math "$l - $c / 2")

    set -l r 0
    set -l g 0
    set -l b 0
    set -l sector (math "floor($h)")

    if test $sector -le 0
        set r $c; set g $x
    else if test $sector -le 1
        set r $x; set g $c
    else if test $sector -le 2
        set g $c; set b $x
    else if test $sector -le 3
        set g $x; set b $c
    else if test $sector -le 4
        set r $x; set b $c
    else
        set r $c; set b $x
    end

    set -l ri (math "round(($r + $m) * 255)")
    set -l gi (math "round(($g + $m) * 255)")
    set -l bi (math "round(($b + $m) * 255)")

    printf '\e]11;#%02x%02x%02x\a' $ri $gi $bi
end