Yeah, the enhanced keyboard protocol change was breaking if you are relying on ambiguous keycodes like C-[. IMO you should not rely on these ambiguous keycodes because it's essentially coincidence that they worked in the first place. And I don't like adding a config option for this since I think the use-case is very niche. Ideally this should be fixed by allowing remapping Escape in the remaining places where it is hard-coded (#5505).

On the other hand though, this could be covered by a config option which overrides the detection, true to assume the protocol is supported and false to assume not. (This has been discussed previously but I can't find the issue.)

Ctrl + [ is the de facto standard esc alternative on macOS, and I don't think the usage is niche, because Ctrl + [ is especially useful when your keyboard does not have an esc key (which is true for many Mac/iPad users). I'm really looking forward to the upcoming esc remapping feature.

I also don't think that using ctrl+[ as esc is a niche use-case, on keyboards with us-layout it is more comfortable to reach (both pinkies) than the actual esc.

For what it's worth you can run hx inside tmux for the moment as a workaround.

These two other control character mappings, backspace ctrl-h and line feed ctrl-j, are still supported after the enhanced keyboard protocol change, so I don't think it is a stretch to keep supporting ctrl-[ as escape by default.

helix 23.03 (3cf03723) on OS X 12.6.4.

Not sure if this is related or not, but I'm having a similar issue. ctrl-m doesn't work in helix as line feed in Iterm2, kitty and alacritty, but does work in wezterm and Terminal at least in insert mode. ctrl-j doesn't work in command mode in any of these terms. showkey -a reports ctrl-m as <CTL-J=LF> in all these terms. In general in all of them ctrl-m works just fine (shell, vim).

Is there anything else I could do to provide more details to diagnose the issue? Thanks!

With neither ctrl-c or ctrl-[ working for this purpose, I'm left having to leave my home row to exit insert mode (via Esc). Is this by design, or am I missing a recommended alternative?

you can always rebind the keymapping in your own config. The enhanced keyboard protocol simply allows disambiguating more keys (like c-[ and esc). The default mapping is esc. The fact that c-[ worked by default was merely an accident. but you can easily restore the mapping

@pascalkuthe can you provide an example?

❯ hx
Bad config: TOML parse error at line 19, column 9
   |
19 | "C-[" = "esc"
   |         ^^^^^
No command named 'esc

@sdemura, almost :) what you want is:

[keys.insert]
  "C-[" = "normal_mode"

but this workaround can't substitute all the esc usage with 'Ctrl-[', so a feature of keycode remapping should be the best solution.

[keys.insert]
"C-[" = "normal_mode"

This doesn't work for me with helix 23.05 (7f5940be) on Ubuntu 22.04 in tmux. It works outside of tmux, but not inside. Any advice?

Termux does not support the kitty enhanced keyboard protocol which allows disambiguation of these keycodes. Since terminal multiplexers essentially function as a terminal proxy they must support all of the features of the host terminal (that the user wants to use)

If tmux doesn't support the disambiguation of ctrl-[ and esc, then shouldn't ctrl-[ work as esc in helix? or am I misunderstanding something?

You can check whether it's enabled by checking the log when running in verbose mode: https://github.com/helix-editor/helix/wiki/Terminal-Support#enhanced-keyboard-protocol

It sounds to me like tmux is probably eating the keycode.

Came here as someone who has been evangelizing mapping CAPS LOCK to CTRL and then using ctrl-[ in vim for over 20 years now. Specifically as someone who has RSI issues and is able to use caps_lock-[ with two very subtle finger movements vs. any alternative. If it was a mere accident that that worked, it's an accident that was true for every combination of vi/vim/nvim/etc. in every terminal emulator and every operating system I've ever used.

Yes I agree, I think all of this talk of C-[ being an accident is a little dismissive. Perhaps it was an 'accident' once but its usage is certainly not niche (as this issue proves). The reality is that many people expect and rely on this behaviour. This just hit me today as Alacritty 0.13.0 now implements the kitty keyboard protocol.

Hi, just came here to say hat I love helix, and wanted to voice my support that mapping control to caps lock and using C-[ is not a niche use case and should please have first class support. Since I am just some guy on the internet, I'll try to supplement my argument with some appeals to authority in hopes that this rhetorical flourish will convince people :)

• In his book Practical Vim, p.30 author Drew Neil recommends mapping caps lock to ctrl and using C-[ as escape. Quote: "The C-[ mapping is synonymous with Esc , and it’s easier to type when the Ctrl key is within easy reach."
• In his talk Stop Writing Deap Programs around the 18:00 minute mark, Jack Rusher says he still maps caps lock to control because it makes his life easier on unix machines (and gives an interesting historical reason for that :) )

I can also try and hop on to help with the implementation if this is a resource issue.

In case it helps anyone… until Helix supports this, using keyd to map C-[ to escape seems to work.

[control]
[ = esc

There is a couple of settings in ~/.tmux.conf that affects the behavior of the escape sequence, and may help with this issue.

In particular the following:

set -sg escape-time 0

In Helix, found the following mapping to be particularly efficient: Ctrl + space

[keys.insert]                                                             
C-space = "normal_mode"    

[keys.normal]
C-space = "insert_mode" 

[keys.select]
C-space = "normal_mode"     

My C-[ muscle memory is so strong that I also do it at prompts and in pickers, which are not currently re-mappable in Helix (that I can find, at least). Would be nice to have it mapped there too.

To advocate for Ctrl + [ users.

They are in their right to notice, this is a very old behavior in VT100 terminal that Ctrl+ [ does produce the escape sequence.

To verify that, we may simply use cat:

cat
We press Escape
That does print ^[
Now we press Ctrl + [
That does also print ^[

Further documentations can be found with keywords: control-escape sequence VT100

I do personally, as a non-Qwerty keyboard user, have to use the key combo Ctrl + AltGr + 4 to output Ctrl + [.

However I do warmly recommend that Helix supports Ctrl + [ as the escape sequence due to legacy reasons.