Is there a way to make a 10-20px line curve with a bigger containers border radius?

Without a border radius, when hovered, the line extends and connects like the middle button so:

With a border radius:

If I try to add a border radius and match it the smaller borders:

Does anyone know how you would make the small borders follow the same curve?

.barChart__button {
  position: relative;
  width: 300px;
  height: 60px;
  color: white;
  border: none;
  background-color: #272A2F;
  border-radius: 20px;
  font-family: 'Roboto';
  font-size: 28px;
  font-weight: 700;
  margin-bottom: 34px;
  transition: 0.5s;
  overflow: hidden;
}

.barChart__button::before {
  content: '';
  position: absolute;
  top: 5px;
  left: 5px;
  width: 10px;
  height: 10px;
  border-top: 2px solid #c3a5ff;
  border-left: 2px solid #c3a5ff;
  transition: 0.5s;
   border-radius: 5px;
}

.barChart__button:hover:before,
.barChart__button:hover:after {
  width: 100%;
  height: 100%;
}

.barChart__button::after {
  content: '';
  position: absolute;
  bottom: 5px;
  right: 5px;
  width: 10px;
  height: 10px;
  border-bottom: 2px solid #c3a5ff;
  border-right: 2px solid #c3a5ff;
  transition: 0.5s;
   border-radius: 5px;
}

<div className='barChart__buttonContainer'>
      
          <button class='barChart__button'>Remaining hours</button>
          <button class='barChart__button'>Requests by user</button>
          <button class='barChart__button'>Other example</button>
</div>
    ```

>Solution :

Here is an idea using mask:

.barChart__button {
  color: white;
  border: none;
  background-color: #272A2F;
  font-size: 20px;
  font-weight: bold;
  padding: 10px 20px;
  border-radius: 10px; /* your radius */
  position: relative;
  z-index: 0;
}
.barChart__button:before {
  content: "";
  position: absolute;
  z-index: -1;
  inset: 0;
  border-radius: inherit;
  padding: 2px; /* border thickness here */
  --g: linear-gradient(#c3a5ff 0 0) no-repeat; /* the color here */
  background: var(--g) 0 0, var(--g) 100% 100%;
  background-size: 10px 10px; /* initial size here */
  -webkit-mask:
    linear-gradient(#000 0 0) content-box,
    linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
          mask-composite: exclude;
  transition: .5s;
}
.barChart__button:hover:before {
  background-size: 100% 100%;
}

body {
  background-color: black;
}

<button class='barChart__button'>Remaining hours</button>
<button class='barChart__button'>Requests by user</button>

Also like below if your background will always be a solid coloration:

.barChart__button {
  border: 2px solid #0000; /* border thickness here */ 
  /* the border color below */
  --g: linear-gradient(#c3a5ff 0 0) no-repeat border-box;
  background: 
    linear-gradient(#272A2F 0 0) padding-box,
    var(--g) 0    0   /var(--s,10px 10px), 
    var(--g) 100% 100%/var(--s,10px 10px),
    #272A2F;
  border-radius: 10px; /* your radius */
  transition:.5s;
  
  color: white;
  font-size: 20px;
  font-weight: bold;
  padding: 10px 20px;
}

.barChart__button:hover {
  --s: 100% 100%;
}

body {
  background-color: black;
}

<button class='barChart__button'>Remaining hours</button>
<button class='barChart__button'>Requests by user</button>