New colleague keeps taking credit for my work, how did you deal with it?

Dealt with this exact situation. My strategy was not confrontation but documentation and visibility. I started putting my ideas in writing, emails and shared docs with timestamps, and CC-ing relevant people, so there's a paper trail showing the idea originated from me. In meetings, I learned to speak up and present my own work rather than letting them do it for me, even if it felt uncomfortable at first. When the colleague repeated my idea, I'd politely add building on what I raised earlier. Subtle but effective. No drama, just quietly making my contributions undeniable. Managers usually figure out who the real doer is over time if you make your work visible. Don't suffer in silence, but stay professional.

I tried the subtle route first and when it didn't work, I had a calm direct chat with the colleague privately. I said I noticed our ideas overlapping and suggested we credit each other's contributions clearly going forward. Sometimes people do it unconsciously and a gentle heads-up stops it. If it continued, my next step was looping my manager in, not by complaining but by proactively updating them on my own work directly and regularly, so my boss heard it from me first. Building your own direct line to your manager is the best defence. Avoid making it a nasty feud, that backfires and makes you look petty. Protect your reputation through consistent visible work, that's the long game that always wins.