What happened to the rules for "ant" and "ent"?

Question

In a quiz just taken, in making an adverb from "courant",  courammant was marked wrong and couramment was correct.  Is courant just different?

Maarten Kamp · Accepted Answer

You may have had a momentary blip or mislearned the lesson as the rule is that - ent goes to «-emment»; - ant goes to «-amment». The question was marked correctly.

Laura Copland · Answer

Mike H wrote: What happened to the rules for
"ant" and "ent"?

In a quiz just taken, in making an adverb from
"courant",  courammant was marked wrong and couramment was
correct.  Is courant just different?

Maarten answered

You may have had a momentary blip or mislearned the lesson
as the rule is that - ent goes to «-emment»; - ant goes to «-amment». The
question was marked correctly.

But “constant” ends in “ant” but when I wrote “constammant,”
it was marked wrong.

I don’t understand why?

Bernard travaille ________.Bernard works constantly.(HINT:
French "constant" = English "constant")

This was the correct answer: constamment

My
     answer was marked incorrect: constammant

Maarten Kamp · Answer

Laura,

the relevant words ending in ‘-ant’ do not go to ‘ ammant‘, as you indicate you wrote. They go to ‘ -amment ‘, as is marked correctly.

https://www.wordreference.com/fren/constamment

This is what I wrote above without having added highlighting unfortunately.

From the lesson :

When turned into adverbs, adjectives ending in -ant and -ent act as follows:

-ant becomes -amment
-ent becomes -emment

Forming adverbs from adjectives ending in -ant and -ent in French (French Adverbs)