In "Walk Like a Man" we see that Chris has become little more than a joke to not only most of his fellow made guys, but he's even treated as a lightweight by Tony. He might be a Captain, but his word holds little clout, authority or respect. He's kicked out of a meeting between Tony, Sil and Bobby when he comes to complain about Paulie stealing from his father-in-law, and later, after he's had a few drinks at the Bing and is waxing philosophical about his daughter, Paulie remarks how she'll end up working at the Bing, and everyone, including Tony, laughs. He's a Capo, but he might as well be a nobody.

He goes to his old friend JT's house, and says how he's done, and he could bring down the entire operation with one phone call; he glamorizes how Gravano is living large down in Arizona, and how Arizona is close to Hollywood and that he knows and has done stuff that could have a lot of complications for a lot of people. When JT shuts him down, Chris kills him.

The very next episode, Chris is driving Tony again, and is notably wearing a ballcap, something we hadn't seen him wear since Season 1. He's somehow gotten himself back high enough in Tony's esteem to attend a high level meeting between Tony, and Phil Leotardo, to discuss asbestos dumping.

On the way back, where Tony is hawkish about dealing with Phil, Chris insists Tony should let Phil get what he wants in this instance.

I think there's evidence here that he flipped between episodes, and was wearing a wire:

1) He's utterly done with Tony and the family as of the last episode and is talking enthusiastically about life in WitSec.

2) It's shown in Season 4 how they no longer use wires for informants, but instead have a microphone hidden in a ballcap. Jack Massarone for example wore one. ...Suddenly Chris is wearing a cap again after how many years?

3) Somehow, a disinterested, disgruntled Chris got back tight enough into Tony's graces to be at a Boss level meeting? Why would a guy like Chris, disgusted with his life in the Mafia, push himself back up the ladder unless perhaps to get as close to the action as possible so as to inform?

4) Chris urges caution and to deal with Phil in an amicable way. He urges Tony to meet Phil's demand. We've seen time and again that rats on the show aren't allowed to take part in violence and many of them as rats play the role of mediator, advocates of peace, to try to ensure violence doesn't break out or involve them (see for example Albie in New York).

I think between episodes, Chris made a phone call to the FBI, got his cap/wire and worked his way back into the inner circle, hoping to put Tony away and start his new life 'living large' like Gravano in Arizona.