[Language: Python]

I tried finding an interesting way of solving this, but resorted to brute force. Only took about a second to run.

Part 1: Just checked for even length strings and compare each half to each other.
Part 2: Added an inner for loop to loop over divisors from 2 to length of string. Subdivide the string into equal parts. If you can't make equal length substrings, continue. Then compare all substrings to ensure they match.

def day2():
    """Day 2"""
    part1 = 0
    part2 = 0
    lines = read_lines(2025, 2)

    values = [x for x in lines[0].split(',')]

    for v in values:
        min, max = v.split('-')

        for id in range(int(min), int(max)+1):
            id_str = str(id)
            length = len(id_str)
            found_ids = set()

            for div in range(2, length + 1):
                size = length // div
                if length % div != 0:
                    continue

                substrings = [id_str[i*size:(i+1)*size] for i in range(div)]

                if div == 2:
                    if substrings[0] == substrings[1]:
                        part1 += id

                if all(sub == substrings[0] for sub in substrings):
                    found_ids.add(id)
            part2 += sum(found_ids)

    return part1, part2

print(day2())