2:18pm: The deal is done, according to Gordon Edes of ESPNBoston.com (on Twitter). Hoyer will join Epstein in Chicago and Byrnes will become the Padres' new GM.
10:47am: The Red Sox and Cubs are "finalizing" an agreement that would bring longtime Red Sox GM Theo Epstein to Chicago, according to Bruce Levine of ESPNChicago.com. The teams are expected to announce the deal tomorrow, as MLB has told the Cubs they can hold a news conference during the World Series travel day. Brett Jackson, Trey McNutt and Matt Szczur will not join the Red Sox in the trade, but another prospect will, according to Levine.
The Cubs will name Jed Hoyer their GM within a few days, Levine reports (Epstein would be the club's president of baseball operations). However, the Cubs have not officially asked for permission to interview Hoyer. The Padres will make Josh Byrnes their GM and won't demand compensation for losing Hoyer, according to Levine.
Alex Speier of WEEI.com confirms that Epstein is expected to be named the Cubs' president of baseball operations with Hoyer joining him as general manager. Compensation between the Cubs and Red Sox hasn't been finalized yet, Speier reports.
Epstein is "close" to joining the Cubs, Ken Rosenthal of FOX Sports confirms (on Twitter). Jon Heyman of SI.com confirms that Hoyer is also joining the Cubs and notes that Josh Byrnes is becoming San Diego's GM (Twitter links).