So what’s wrong with that? Have you been talking to my ghostwriter?

Here are four tactics, in diminishing order of nobility.

Congratulate. Play along. Go out of your way to compliment him for his every claim of your accomplishments. “Jack, your competence and productivity amaze me. It’s almost like you do the work of two people (hint, hint)! And here (cite the example) you did it again. Maybe I take you out to lunch to get your advice on productivity?”

Conciliate. Take it in stride. It’s easier said than done, but don’t let it bug you. Don’t make his problem (self-delusion, self-promotion) your problem. Sooner or later his ruse will come undone, along with his reputation. You will rightfully enjoy the admiration that is due you for being above it all – magnanimous. It is good sense to be slow to anger, and an honor to overlook an offense. (Prov 19:11)

Confront. Challenge him in no uncertain terms. Make it clear that you’re not going to take it, will call him out if it happens again, and expose his phony claims. You may surely reprove your neighbor, but shall not incur sin because of him. (Lev 19:17) “Jack, you and I both know you’re stealing my thunder. Do it one more time and I’ll expose you as a fraud – and with evidence.”

Connive. Beat him at his own game. Start taking credit for his accomplishments (if he has any). But if you do, you’ll diminish yourself in the process, and it will probably backfire anyway. Conniving is a temptation, not a tactic, but it does have its appeal. See that none of you repay evil for evil, but always seek to do good. (1 Thess 5:15)

Whatever your course, there’s one person who should be well aware of your accomplishments – your boss. Most likely he/she is already aware, but don’t assume so. Taking credit where credit is due is not boasting; it’s truthfulness.