Title. When I set Finder to open .p8 files in pico, it opens, but pico just hangs on a black screen.
Example Video

can you show your configuration?
maybe you need a special parameter to tell the program to pass the full file name. but it’s strange to have a full black screen and not a «could not load» error.

I'm using the default config

// :: Video Settings

window_size 0 0 // window width, height
screen_size 0 0 // screen width, height (stretched to window)
show_fps 0 // Draw frames per second in the corner

// :: Window Settings

windowed 0 // 1 to start up in windowed mode
window_position -1 -1 // x and y position of window (-1, -1 to let the window manager decide)
frameless 0 // 1 to use a window with no frame
fullscreen_method 1 // 0 maximized window (linux) 1 borderless desktop-sized window 2 hardware fullscreen (warning: erratic behaviour under some drivers)

// :: System Settings

foreground_sleep_ms 2 // number of milliseconds to sleep each frame. Try 10 to conserve battery power

background_sleep_ms 10 // number of milliseconds to sleep each frame when running in the background

sessions 37 // number of times program has been run

// (scancode) hold this key down and left-click to simulate right-click
rmb_key 0 // 0 for none 226 for LALT

// Desktop for saving screenshots etc. Defaults to $HOME/Desktop
desktop_path

// 1 to allow controller input even when application is in background
read_controllers_in_background 0

// :: Audio Settings (use "volume" for PICO-8)

sound_volume 256 // 0..256
music_volume 256 // 0..256

// :: usually 1024. Try 2048 if you get choppy sound

mix_buffer_size 1024

// ::

version 0.2.4C

// audio volume: 0..256
volume 256

// Location of pico-8's root folder
root_path /Users/calebwestaway/Library/Application Support/pico-8/carts/

// Location of cartridge save data
cdata_path /Users/calebwestaway/Library/Application Support/pico-8/cdata/

// Specify which player index joystick control begins at (0..7)
joystick_index 0

// Custom keyboard scancodes for buttons. player0 0..6, player1 0..5
button_keys 0 0 0 0 0 0 0 0 0 0 0 0 0

// Play notes as they are plotted in frequency mode
live_notes 0

// iff 1: when using keyboard cursor, snap to closest pixel / map cel
cursor_snap 0

// 0 default 1 dark blue background in code editor 2 black background in code editor 3 gray background in code editor
gui_theme 0

// scale of screenshots and gifs // 2 means 256x256
screenshot_scale 3
gif_scale 3

// maximum gif length in seconds (0..120; 0 means no gif recording)
gif_len 16

// when 1, reset the recording when pressing ctrl-9 (useful for creating a non-overlapping sequence)
gif_reset_mode 0

// 0 for off. 1 to allow control of a cart's framerate due to host machine's cpu capacity (recommended)
host_framerate_control 1

// filter splore cartridges
// 0 off 1 on (exclude cartridge tagged as 'mature' by community)
splore_filter 0

// tab display width (1 ~ 4 spaces)
tab_width 1

// 0 off 1 on: draw tab characters as small vertical lines
draw_tabs 0

// 0 off 1 on: record the current cartridge and editor view every 3 seconds (see [appdata]/activity.log.txt)
record_activity_log 1

// 0 off 1 on: allow F6..F9 (alternative: ctrl 6..9)
allow_function_keys 1

// 0 off 1 on: automatically check for a newer version of a BBS cart each time it is run.
check_for_cart_updates 1

// hide mouse cursor for n seconds when typing.
auto_hide_mouse_cursor 5

// 0 off 1 on: backup with a new timestamped filename on every run
// normally not needed -- was used for debugging crash-on-run
aggressive_backups 0

// back up cartridge in editor every n minutes when not idle (0 for no periodic backups)
periodic_backups 20

// global screen transformations:
// 129 flip horizontally
// 130 flip vertically
// 133 rotate CW 90 degrees
// 134 rotate CW 180 degrees
// 135 rotate CW 270 degrees
transform_screen 0

// 0 off 1 on: show pixel grid in the gfx editor at zoom:8 and zoom:4
gfx_grid_lines 0

didn’t mean the pico-8 config, especially if it’s all defaults! ;)
but the finder config «When I set Finder to open .p8 files» → set finder how and to what command exactly?

Sorry, still new to this. I right-clicked the file, then 'Other', selected pico-8 and checked 'always open with'