The “menu glitch” is an exploit in Chrono Trigger that can be executed in Jets of Time. While Jets almost always uses the Disable Glitches (g) flag to patch many of the glitches used in vanilla speedruns, this does not qualify. This is always usable in Jets of Time and is considered an important strategy when fighting both Lavos and Zeal.

This trick allows you to open the menu when the game doesn't intend you to do so (though it has been discovered at least in one case that you can press the “Y” button during the timing window to open up the character switching menu as well). Press “X” during one of the opportunities and you can menu when you otherwise wouldn't be able to. This can be a great chance to refill HP and MP or change equipment.

The reason this is possible: the game uses internal “flags” to tell the game when it's in, for example, a battle or cutscene. Sometimes when enough frames pass between ending a cutscene/battle and entering the next, the game will be briefly left in a state of free movement which allows the menu to be opened by pressing “X.”

Most of them work when the screen fades out, with the Zenan Bridge glitch being the notable exception.

The most notable opportunities for the menu glitch are listed below.

This is considered the most important version of the glitch. It is activated in between the fight with Inner Lavos and the Lavos Core. After the first battle, Inner Lavos will disappear and leave the humanoid Core behind. After a short cutscene it will summon the two Bits, screech, and the music will start. The screen will fade first to white, then to black. When the screen fades completely to black, press “X” (pressing and holding is recommended to maximize the input window) to open the menu.

Because there is no music until the end of the cutscene where it always starts at a specific time, this can be done by sound.

Used between the first form of Queen Zeal and the Mammon Machine. After defeating her first form, she'll speak a line of dialogue, jump atop the Mammon Machine, and the screen will fade to black. Press and hold “X” just as the screen turns black to open the menu. This one has a pretty generous timing window and is considered the easiest version of the glitch to perform. It's also fairly important because Zeal casting Halation in her first form might leave the player with a party at 1 HP.

There are two separate opportunities to activate this one, both under the same circumstances. After each battle versus Ozzie and some skeletons, the menu button can be pressed just as the party converges. The timing for this one is extremely tight, so many players will choose to mash “X” instead of pressing and holding.

This version of the glitch is probably the least important listed here, but it can still be useful. While players aren't too likely to get hurt in the Ozzie fights, using high-powered magic to clear the fights early in the game can cost a lot of MP that normally wouldn't refill before fighting Zombor. The fights here also have potential to drop good items, so it's possible to try and equip desirable drops immediately.

The Menu Glitch can also be activated in the Ocean Palace, after stabbing the Mammon Machine with either the Ruby Knife or Masamune. Once again, it is activated just as the screen goes black. This one has a pretty generous window. However, because the fight that follows it is against Lavos, most players prefer to run back to the save point prior to the twin boss and use it. This can still be helpful if you forget to do something, though.

Free Menu Glitch is a flag under Quality of Life. When enabled, this widens the window of opportunity to register the button press needed to open the menu during the Lavos and Queen Zeal boss fights.