The 19-year-old centre-back made his League Two debut in the final game of last season, and in doing so was able to impress his new manager.
The Bantams finished their 2020-21 against Morecambe, who were managed by Derek Adams at the time. Since leading them to promotion through the play-offs, Adams has switched to Valley Parade.
“He has physical strength beyond his years and a great attitude towards learning, improving and battling on the field," said Adams.
“I got a good look at him on the final day of the regular season when he played against my Morecambe side, and was impressed by what I saw. He more than demonstrated his ability to compete at this level.
“I am very much looking forward to working with him and am excited to see how he develops further over the course of the next year.”
Sikora, whose only other appearances last season were three Football League Trophy starts, now knows he needs to kick on.
“I did not play as much as I probably would have liked to throughout last season, but I did start against Morecambe on the final day, which is where I felt I took my chance," he said.
“It is all tunnel vision ahead of next year, now. It is important I kick on and show more of what I can do.
“I have been here since the under-13s, and came through with the likes of Finn Cousin-Dawson, Kian Scales and Reece Staunton.
“There is a clear pathway to the first team from the academy, and I am pleased to have been able to step up with them. "
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