PS1 environment variable modified after requiring ghostel on MSYS2 bash

[zHaOdANiuu]

Thank you for supporting the Windows platform — it's great to be able to use ghostel on Windows.

However, I've encountered an issue with environment variables being modified when running under MSYS2 bash.

• Shell: MINGW64_NT-10.0-19045 (3.6.9-01d6c708.x86_64, 2026-05-24)
• OS: Microsoft Windows [Version 10.0.19045.3803]
• Emacs: GNU Emacs 32.0.50 (Development version d7b070b74c5f, built 2026-07-10)

Problem

When I launch ghostel, environment variables inherited from the terminal are altered after requiring ghostel. Specifically, the PS1 variable (bash prompt) gets changed, which modifies my shell prompt unexpectedly.

Steps to Reproduce

1. Start Emacs with emacs -Q
2. Evaluate the following code:

;; Check PS1 value before requiring ghostel
(getenv "PS1")
;; => e.g. "expected prompt value"

(progn
  (package-initialize)
  (require 'ghostel))

;; Check PS1 value after requiring ghostel
(getenv "PS1")
;; => e.g. "unexpected modified prompt value"

3. Observe that PS1 has been changed after requiring ghostel.

Expected Behavior

PS1 and other inherited environment variables should remain unchanged after requiring ghostel.

Actual Behavior

After requiring ghostel, PS1 is modified, which causes the bash prompt to change from its expected appearance.

Normal prompt:

After ghostel:

The workaround is simple — just restore the environment variables to their original values after requiring ghostel.

(progn
  (package-initialize)
  (require 'ghostel)
  (setenv "PS1" "\\[\\e]0;\\w\\a\\]\\n\\[\\e[32m\\]\\u@\\h \\[\\e[35m\\]$MSYSTEM\\[\\e[0m\\] \\[\\e[33m\\]\\w\\[\\e[0m\\]\\n\\$ "))

[emil-e]

I am unable to reproduce this. Are you sure it's actually changing the env var itself? Not just messing with your shell prompt in shells you run inside Ghostel?

[emil-e]

Can you evaluate this:

(advice-add
 'setenv :around
 (lambda (fn variable &optional value substitute)
   (when (equal variable "PS1")
     (message "PS1 SET TO %S\n%s"
              value
              (backtrace-to-string)))
   (funcall fn variable value substitute)))

Then run the same repro you described and check *Messages* and post the output here?

[zHaOdANiuu]

I am unable to reproduce this. Are you sure it's actually changing the env var itself? Not just messing with your shell prompt in shells you run inside Ghostel?

To be honest, I'm not sure if it's actually modifying the environment variable. It's just that every time I open Ghostty, my bash prompt becomes empty. I don't know why this happens — only bash has this issue, CMD and PowerShell are fine. I recorded the PS1 environment variable before and after opening Ghostty and found that it had been changed, which is how I came to that conclusion.

I heard yesterday that Ghostty had merged Windows support, so I jumped in right away to try it out. Since there's basically no one around me who uses Emacs with Ghostty on Windows, I can't tell whether this is an issue specific to my computer's environment or some other kind of obscure bug — that's why I opened this issue.

[zHaOdANiuu]

Can you evaluate this:

(advice-add
'setenv :around
(lambda (fn variable &optional value substitute)
(when (equal variable "PS1")
(message "PS1 SET TO %S\n%s"
value
(backtrace-to-string)))
(funcall fn variable value substitute)))
Then run the same repro you described and check *Messages* and post the output here?

I tried it, but the message buffer didn't capture anything. Sorry — I think what I said earlier might have been misleading. Is there anything else I can help with? If you can't reproduce the issue, I think it might just be a problem specific to my own machine's environment.

[zHaOdANiuu]

Can you evaluate this:

(advice-add
'setenv :around
(lambda (fn variable &optional value substitute)
(when (equal variable "PS1")
(message "PS1 SET TO %S\n%s"
value
(backtrace-to-string)))
(funcall fn variable value substitute)))
Then run the same repro you described and check *Messages* and post the output here?

That said, this snippet actually works — running it before launching Ghostel somehow manages to fix the PS1 environment variable. It's honestly mind-blowing.

In the video, the first time I ran Ghostel, the PS1 environment variable was still empty. But the second time, after adding this snippet, the PS1 environment variable just came back.

[emil-e]

I wonder if it's some sort race condition. I think your issue may be related to TRMAP, since that prompt looks like it could come from there: https://github.com/emacs-mirror/emacs/blob/c6147e2b539dc3490b47a924bed86da00cc763a7/lisp/net/tramp-sh.el#L99

[zHaOdANiuu]

I wonder if it's some sort race condition. I think your issue may be related to TRMAP, since that prompt looks like it could come from there: https://github.com/emacs-mirror/emacs/blob/c6147e2b539dc3490b47a924bed86da00cc763a7/lisp/net/tramp-sh.el#L99

It does seem to be the case. Based on your code snippet above, I modified it to skip setting the PS1 environment variable, and it works.d

(advice-add
 'setenv :around
 (lambda (fn variable &optional value substitute)
   (unless (equal variable "PS1")
     (funcall fn variable value substitute))))

Below is the backtrace message.

(advice-add
 'setenv :around
 (lambda (fn variable &optional value substitute)
   (when (equal variable "PS1")
     (backtrace)
     (funcall fn variable value substitute))))

this is log

  backtrace()
  (progn (backtrace) (funcall fn variable value substitute))
  (if (equal variable "PS1") (progn (backtrace) (funcall fn variable value substitute)))
  #f(lambda (fn variable &optional value substitute) [t] (if (equal variable "PS1") (progn (backtrace) (funcall fn variable value substitute))))(#f(compiled-function (variable &optional value substitute-env-vars) "Set the value of the environment variable named VARIABLE to VALUE.\nVARIABLE should be a string.  VALUE is optional; if not provided or\nnil, the environment variable VARIABLE will be removed.\n\nInteractively, a prefix argument means to unset the variable, and\notherwise the current value (if any) of the variable appears at\nthe front of the history list when you type in the new value.\nThis function always replaces environment variables in the new\nvalue when called interactively.\n\nSUBSTITUTE-ENV-VARS, if non-nil, means to substitute environment\nvariables in VALUE with `substitute-env-vars', which see.\nThis is normally used only for interactive calls.\n\nThe return value is the new value of VARIABLE, or nil if\nit was removed from the environment.\n\nThis function works by modifying `process-environment'.\n\nAs a special case, setting variable `TZ' calls `set-time-zone-rule' as\na side-effect." (interactive #f(compiled-function () #<bytecode -0x1d6e86c7e43a8c2>)) #<bytecode 0xaff01e7fb633305>) "PS1" "#$ ")
  apply(#f(lambda (fn variable &optional value substitute) [t] (if (equal variable "PS1") (progn (backtrace) (funcall fn variable value substitute)))) #f(compiled-function (variable &optional value substitute-env-vars) "Set the value of the environment variable named VARIABLE to VALUE.\nVARIABLE should be a string.  VALUE is optional; if not provided or\nnil, the environment variable VARIABLE will be removed.\n\nInteractively, a prefix argument means to unset the variable, and\notherwise the current value (if any) of the variable appears at\nthe front of the history list when you type in the new value.\nThis function always replaces environment variables in the new\nvalue when called interactively.\n\nSUBSTITUTE-ENV-VARS, if non-nil, means to substitute environment\nvariables in VALUE with `substitute-env-vars', which see.\nThis is normally used only for interactive calls.\n\nThe return value is the new value of VARIABLE, or nil if\nit was removed from the environment.\n\nThis function works by modifying `process-environment'.\n\nAs a special case, setting variable `TZ' calls `set-time-zone-rule' as\na side-effect." (interactive #f(compiled-function () #<bytecode -0x1d6e86c7e43a8c2>)) #<bytecode 0xaff01e7fb633305>) ("PS1" "#$ "))
  setenv("PS1" "#$ ")
  tramp-call-process(nil "reg" nil nil nil "query" "HKEY_CURRENT_USER\\Software\\SimonTatham\\PuTTY\\Sessions")
  tramp-set-completion-function("plinkx" ((tramp-parse-putty "HKEY_CURRENT_USER\\Software\\SimonTatham\\PuTTY\\Sessions")))
  #f(compiled-function () #<bytecode 0x12afb884d4a871d4>)()
  run-hooks(tramp--startup-hook)
  byte-code("\301\302\303\304#\210\305\306!\210\307\300!\210\310\20\311\312!\207" [tramp--startup-hook put tramp-unload-tramp tramp-autoload t provide tramp run-hooks nil require tramp-cache] 4)
  require(tramp)
  byte-code("\300\301!\210\300\302!\210\300\303!\210\300\304!\210\300\305!\210\300\306!\210\300\307!\210\300\310!\210\300\311!\210\300\312!\210\300\313!\210\300\314!\210\300\315!\210\300\316!\210\300\317!\210\320\321\322\323\324\325\326\327&\7\210\330\331\332\333\334DD\335\336\337%\210\330\340\332\333\341DD\342\336\343%\210\330\344\332\333\345DD\346\336\347%\210\330\350\332\333\351DD\352\336\353%\207" [require ansi-color cl-lib comint compat project shell text-property-search tramp url-parse face-remap ghostel-faces ghostel-kitty ghostel-line-mode ghostel-module-install ghostel-prompt custom-declare-group ghostel nil "Terminal emulator powered by libghostty." :group terminals :prefix "ghostel-" custom-declare-variable ghostel-shell funcall function #f(compiled-function () #<bytecode 0x1f4dcf4d2449a428>) ("c:/Users/you/.emacs.d/elpa/ghostel-20260711.1412/ghostel.elc" . 87) :type (choice (string :tag "Executable path") (repeat :tag "Executable + arguments" string)) ghostel-term #f(compiled-function () #<bytecode 0x1e9e7430ba62b50>) ("c:/Users/you/.emacs.d/elpa/ghostel-20260711.1412/ghostel.elc" . 757) (choice (const :tag "Ghostty (recommended)" "xterm-ghostty") (const :tag "Generic xterm-256color" "xterm-256color") (string :tag "Other")) ghostel-environment #f(compiled-function () #<bytecode 0x18c000af2941>) ("c:/Users/you/.emacs.d/elpa/ghostel-20260711.1412/ghostel.elc" . 1822) (repeat string) ghostel-use-native-pty #f(compiled-function () #<bytecode 0x18c000af29b1>) ("c:/Users/you/.emacs.d/elpa/ghostel-20260711.1412/ghostel.elc" . 3772) boolean] 8)
  autoload-do-load((autoload "ghostel" "Start a new Ghostel terminal.  If the buffer already exists, switch to it.\nWith a non-numeric prefix arg, create a new buffer.\nWith a numeric prefix ARG, switch to the buffer with that number or\ncreate it if it doesn't exist yet.\nThe name of the buffer is determined by the value of `ghostel-buffer-name'.\nReturns the buffer.\n\n(fn &optional ARG)" t nil) ghostel)
  command-execute(ghostel)

[dakra]

FYI, I think that's an Emacs bug and I filed a bug report upstream: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=81409

[zHaOdANiuu]

FYI, I think that's an Emacs bug and I filed a bug report upstream: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=81409顺便说一下，我觉得这是Emacs的bug，我上游也提交了bug报告：https://debbugs.gnu.org/cgi/bugreport.cgi?bug=81409

thanks.