In-season signings
 

What dictates player's demands in-season? I needed to sig a CB as an injury replacement but he wanted a 400k bonus that I didn't want to give him because he would probably get cut a few weeks later. I offered about a million salary with a 50k bonus and his agent said it was very far from their demands, so I walked away. When I checked the transactions the next week, he'd signed on a minimum-salary deal with an AI, which was about half of what I'd offered him.

Was it for less years? When signing players they value short contracts more than long, with bonus and 1st year salary the most important. You can offer less money overall with a larger bonus and/or larger 1st year and often sign your guy. Each player has other factors they consider when making decisions besides money as well.

They were both in-season deals that just would've lasted until the end of the season. I understand the bonus/ 1st year cashflow dynamics for signing free agents during the offseason, but that's not as relevant in-season. I tried stuff like offering 1 million with no bonus, or 600k with 250k bonus, but both were laughed off by the agent, only for the player to sign a minimum-salary no-bonus deal that same week with a different team. Is this just a mechanism to give AI teams some small edge over users?

Okay, here's a flag to keep in mind this is a computer game. The minsal signing with an AI team is just being done as a clean-up routine in the computer program. It is not that a tiny little agent in the game "decided" it was a better offer than yours.

I don't claim the perfect answer to your question, but mechanically it does make some sense. If the player "believes" he's a quality addition he is demanding some "guaranteed money" as a bonus. He'd rather get some money up front than hope to earn some game checks. if you follow that logic, then the tiny little agent in the game is definitely justified in rejecting your base-salary-only offer, and to demand some guaranteed money. Underscored by your confession that you see the guy as a few-weeks-only signing.

So... overall, his demands seem reasonable, to me. Then (thinking separately) the in-game sweeper sometimes kicks in, and acts irrationally (i.e. hamfisted forcing of minsal deals) to tidy up the game and ensure all rosters are complete.