Default preset and switching preset, inspiration for future

[DrChr]

Starting a discussion on use of presets, and how to have a default preset, and how to switch.

Background: This issue: #1000 where I at the end wondered:

Is there a way through init.el to have a specific preset that's used by default,
i.e. unless the user switches to another preset?

Based on karthink's help, I came up with the code below. Sharing it here in the hope it helps others and facilitates discussions about usage of presets.

Note: The code example at the bottom uses a private gptel function, so it'll eventually break.

First define some preset, that can use a shared "base-preset".

 (gptel-make-preset 'base-preset
  :description "Place for common settings to be incuded in presets"
  :backend "Azure-1"
  :model 'gpt-4.1 )

(gptel-make-preset 'emacs-assistant
  :description "Corresponds to gptel defaults"
  :parents 'base-preset
  :system "You are a large language model living in Emacs and a helpful assistant. Respond very concisely." )

(gptel-make-preset 'gpt4coding
  :description "A preset optimized for coding tasks"
  :parents 'base-preset
  :system "You are an expert coding assistant. Your role is to provide high-quality code solutions, refactorings, and explanations." )

Then (unfortunately) manually listing the presets from which I can interactively select:

(setq gptel-my-presets '(emacs-assistant gpt4coding))

And a function to help select/set a default prefix.

(defun gptel-my-set-default-preset (&optional preset)
  "Select a preset for gptel to use by default, interactively or via the
argument PRESET. If PRESET is nil, use the first element of `gptel-my-presets`

Note: Uses gptel's private function 'gptel--apply-preset', which may break when gptel
updates its API.
See https://github.com/karthink/gptel/issues/1000
"
  (interactive
   (list
    (completing-read "Preset: " (mapcar #'symbol-name gptel-my-presets) nil t)))
  (unless gptel-my-presets
    (user-error "gptel-my-presets is empty"))
  (let* ((fn 'gptel--apply-preset)
         (default-preset (car (bound-and-true-p gptel-my-presets)))
         (preset-sym (if (stringp (or preset default-preset))
                         (intern (or preset default-preset))
                       (or preset default-preset))))
    (if (fboundp fn)
        (funcall fn preset-sym)
      (user-error "Function gptel--apply-preset is unavailable (may have changed)"))))

(gptel-my-set-default-preset)

[karthink]

All of this functionality is already built into gptel's transient menu. Is there some reason you don't want to use the interactive interface gptel provides for switching presets?

Then (unfortunately) manually listing the presets from which I can interactively select:

(setq gptel-my-presets '(emacs-assistant gpt4coding))

You don't need to define a gptel-my-presets variable. All defined presets are stored in gptel--known-presets. So you can run:

(defun gptel-my-set-default-preset (&optional preset)
  (interactive
   (list (intern-soft
          (completing-read "Apply preset: " gptel--known-presets))))
  (unless preset (user-error "No preset specified"))
  (condition-case nil
      (progn (gptel--appl-preset preset)
             (message "Preset %s applied" preset))
    (void-function
     (user-error "Function `gptel--apply-preset' is unavailable (may have changed)"))))

[DrChr]

One reason is that I hadn't noticed being able to use '@' in gptel-menu to switch presets.

It looks nice though:

And that reason is in combination with me not being sure how the 'Scope' part works.

Which finally is in combination with not being sure when/how changes are applied.

Say I'm in a source code file and I:

1. Activate gptel-menu
2. Set the scope to buffer
3. Use '@' to change to some preset
4. Finally I press 'ctrl-g' to abort, as I only wanted to change the preset.

From a UX-point of view, did the changed preset persist, or did the 'ctrl-g' abort that change?

Phrased differently, when does the changes take effect?

So a large part of it is that I'm unfamiliar with how to use the transient menu.

I think my brain is expecting some way to "save settings", as I probably expect 'ctrl-g' to revert things to as they were before I entered the transient menu.

If changes in the menu take effect immediately in a persisten way, how do you undo all the changes? (if 'ctrl-g' doesn't do that).

Note: I'm just starting to use an LLM as well as gptel. So I also made the code above as a learning experience regarding how to use gptel in practice. It was interesting as I don't normally use Lisp and haven't used it in ... over twenty years or so. It was a pleasant surprise how accessible it was to hack something together when aided by gptel. :-)

[DrChr]

I just tested... and I'm not sure why 'C-s' is mentioned at the top of the preset menu.
Experimenting, it seems that a preset might be applied without using 'C-s', even if I exit the transient menu using 'C-g'.

[karthink]

One reason is that I hadn't noticed being able to use '@' in gptel-menu to
switch presets.

You can also click on the @preset display, it's a button.

It looks nice though: <img width="478" height="127"
alt="{BF65FA8A-567C-449C-B7D8-53B6D3BE962B}"
src="https://github.com/user-attachments/assets/0a1596d4-58e4-4736-9954-92fa0ed0ab82"
/>

And that reason is in combination with me not being sure how the 'Scope'
part works.

When you change the scope, a message is printed to the echo area explaining what it does.

Which finally is in combination with not being sure when/how changes are
applied.

Say I'm in a source code file and I:
1. Activate gptel-menu
2. Set the scope to buffer
3. Use '@' to change to some preset
4. Finally I press 'ctrl-g' to abort, as I only wanted to change the preset.

From a UX-point of view, did the changed preset persist, or did the 'ctrl-g'
abort that change?

Phrased differently, when does the changes take effect?

Changes take effect immediately. Ctrl-g just quits the menu. That's a Transient default, if that doesn't make sense, you can run (transient-bind-q-to-quit) to change the setting. You can then quit Transient menus with q, like most other read-only buffers in Emacs.

So a large part of it is that I'm unfamiliar with how to use the transient
menu.

Yes, Transient takes a little getting used. Only a little though, it's very intuitive afterwards.

I think my brain is expecting some way to "save settings", as I probably
expect 'ctrl-g' to revert things to as they were before I entered the
transient menu.

If changes in the menu take effect immediately in a persisten way, how do
you undo all the changes? (if 'ctrl-g' doesn't do that).

There is no way to undo applying a preset -- you just apply another one. This allows you to layer presets.

[karthink]

I just tested... and I'm not sure why 'C-s' is mentioned at the top of the
preset menu.  Experimenting, it seems that a preset might be applied without
using 'C-s', even if I exit the transient menu using 'C-g'.

C-s does the reverse: it saves your current gptel settings, whatever they are, as a new preset (or overwrites an existing one).