second approach with state object as key

is_valid_hashtag_key_state_object.kt.diff

@Composable
private fun PostHashtags(
    hashtags: ImmutableList<String>,
    onAddHashTag: (String) -> Unit,
    modifier: Modifier
) {
-   var inputHashTag by remember(hashtags) { mutableStateOf("") }
+   val inputHashTag = remember(hashtags) { mutableStateOf("") }
-   val isValidHashtag: Boolean by remember {
+   val isValidHashtag: Boolean by remember(inputHashTag) {
        derivedStateOf {
-           !inputHashTag.contains(" ")
+           !inputHashTag.value.contains(" ")
        }
    }

    Column(modifier = modifier) {
        OutlinedTextField(
-           value = inputHashTag,
+           value = inputHashTag.value,
-           onValueChange = { inputHashTag = it },
+           onValueChange = { inputHashTag.value = it },
            leadingIcon = { Text(text = "#", fontWeight = FontWeight.Bold) },
            placeholder = { Text(text = "Type a hashtag here") },
            trailingIcon = {
                AnimatedVisibility(
-                   visible = inputHashTag.isNotEmpty() && isValidHashtag,
+                   visible = inputHashTag.value.isNotEmpty() && isValidHashtag,
                    enter = fadeIn(),
                    exit = fadeOut()
                ) {
-                   IconButton(onClick = { onAddHashTag(inputHashTag) }) {
+                   IconButton(onClick = { onAddHashTag(inputHashTag.value) }) {
                        Icon(imageVector = Icons.Default.AddCircle,
                            contentDescription = "Add hashtag")
                    }
                }
            },
            isError = !isValidHashtag,
        )
        AnimatedVisibility(visible = !isValidHashtag) {
            Text(
                text = "Hashtag cannot have a space",
                style = MaterialTheme.typography.labelSmall,
                modifier = Modifier.padding(vertical = 2.dp)
            )
        }
        ReusableVerticalLazyList(content = hashtags)
    }
}