Kitty graphics: t=t temporary files in /tmp are rejected on macOS

[magnussp]

Issue Description

On macOS, Kitty graphics transmissions with t=t (temporary file) only work for files under Ghostty's own $TMPDIR. A file in /tmp named tty-graphics-protocol* is rejected with EINVAL: temporary file not in temp dir and is left on disk.

Ghostty compares the file's canonical path with its temp roots. On macOS /tmp is a symlink to /private/tmp, so the canonical path starts with /private/tmp/ and never matches the literal /tmp root. The configured temp directory is resolved before comparing, but /tmp and /dev/shm are not.

kitty resolves every root (is_path_in_temp_dir in kitty/utils.py realpaths /tmp, /dev/shm and $TMPDIR), so it accepts these files, and so does Ghostty on Linux. On macOS, a client that writes to /tmp, or runs with a different TMPDIR than Ghostty, can't use t=t and has to fall back to direct transmission, which is much slower for large or frequent images.

The same logic is on main (isPathInTempDir in src/terminal/kitty/graphics_image.zig).

A fix is on this branch.

AI disclosure: I used Claude Code to find the cause, write the repro script and draft this report, which I then reviewed and edited.

Expected Behavior

A t=t file in /tmp is loaded and deleted, as in kitty and in Ghostty on Linux.

Actual Behavior

The reply is EINVAL: temporary file not in temp dir and the file is left behind.

Reproduction Steps

1. Launch Ghostty normally.
2. Run python3 kitty-tmpfile-repro.py (script below) in it.

Output on 1.3.1:

/tmp/tty-graphics-protocol-repro
  reply: b'\x1b_Gi=1;EINVAL: temporary file not in temp dir\x1b\\'
  file left behind: True
/var/folders/.../T/tty-graphics-protocol-repro
  reply: b'\x1b_Gi=1;OK\x1b\\'
  file left behind: False

Launching Ghostty with open -na Ghostty.app --env TMPDIR=/tmp makes the /tmp case work.

kitty-tmpfile-repro.py

# Run inside Ghostty: python3 kitty-tmpfile-repro.py
# Sends a Kitty graphics t=t (temporary file) transmission for a file in
# /tmp and one in $TMPDIR, then prints each reply and whether the file
# was left behind (the terminal deletes it on success).
import base64, os, select, tempfile, termios, tty

tty_fd = os.open("/dev/tty", os.O_RDWR)


def transmit(path):
    with open(path, "wb") as f:
        f.write(b"\xff\x00\x00\xff")  # one RGBA pixel
    payload = base64.b64encode(path.encode()).decode()
    os.write(tty_fd, f"\x1b_Ga=t,t=t,f=32,s=1,v=1,i=1;{payload}\x1b\\".encode())
    reply = b""
    while b"\x1b\\" not in reply and select.select([tty_fd], [], [], 2)[0]:
        reply += os.read(tty_fd, 1024)
    kept = os.path.exists(path)
    if kept:
        os.remove(path)
    return reply, kept


paths = [
    "/tmp/tty-graphics-protocol-repro",
    os.path.join(tempfile.gettempdir(), "tty-graphics-protocol-repro"),
]
old = termios.tcgetattr(tty_fd)
tty.setraw(tty_fd)
try:
    results = [(path, *transmit(path)) for path in paths]
finally:
    termios.tcsetattr(tty_fd, termios.TCSADRAIN, old)

for path, reply, kept in results:
    print(f"{path}\n  reply: {reply!r}\n  file left behind: {kept}")

Ghostty Logs

[com.mitchellh.ghostty:kitty_gfx] kitty_gfx: erroneous kitty graphics response: EINVAL: temporary file not in temp dir

Ghostty Version

Ghostty 1.3.1

Version
  - version: 1.3.1
  - channel: stable
Build Config
  - Zig version   : 0.15.2
  - build mode    : .ReleaseFast
  - app runtime   : .none
  - font engine   : .coretext
  - renderer      : renderer.generic.Renderer(renderer.Metal)
  - libxev        : kqueue

OS Version Information

macOS 15.7.4 (24G517), Apple M1 Pro

(Linux only) Display Server

None

(Linux only) Desktop Environment/Window Manager

No response

Minimal Ghostty Configuration

# None needed: reproduces with no config loaded (--config-default-files=false)

Additional Relevant Configuration

No response

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty documentation and confirm there doesn't exist a configuration option that solves my issue.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[jcollie]

!vouch

[jcollie]

#14567