inner mode indentation not works on the first line after head mark

[Ziqi-Yang]

Code(brief):

(defun typst-indent-line ()
  (interactive)
  (message "function executing") ;; to show whether the function is executing
  ;; do indentation
)

You can also view it on my repo: permlink
And this is the test file(part)(all comments are only added here for better present this issue):

{ # this is the inner mode head mark
let a = [from] # mark 1
let b = [*world*]
[hello ]
[
	asdf
]	
a + [ the ] +
} # this is the inner mode tail mark

mark 1: when the cursor on this line: 1. when there is no content in the previous line after '{', the function won't be executed when I hit tab, but I can correctly indent this line by manually calling my indent line function typst-indent-line; 2. when there is content in the previous line after '{', the function will be called and I have noticed that the result of (current-indentation) for previous line is the number of blank columns between { and non-blank character. However, the second scenario will fail to indent the line(hit tab), but still, a direct call to tyspt-indent-line works.
This is my inner mode definition

(define-innermode typst--poly-code-innermode
  :mode 'typst--code-mode
  :head-matcher "\\(^{\\|[^\\]{\\)"
  :tail-matcher "\\(^}\\|[^\\]}\\)"
  :head-mode 'host
  :tail-mode 'host)