Sledgehammer Games built a Halo multiplayer prototype that Xbox quietly killed

Sledgehammer Games — the Call of Duty studio behind WW2, Vanguard, and Modern Warfare 3 — reportedly developed a Halo multiplayer prototype for Microsoft, but the project was cancelled before it got anywhere near a full greenlight. The report comes from YouTuber Rebs Gaming, corroborated by Windows Central's Jez Corden, who had separately speculated that Xbox was exploring Activision's involvement in Halo development.

According to Rebs Gaming's source — the same source who previously provided accurate details about Halo: Campaign Evolved — the prototype was only in the early blockout phase, with basic gameplay mechanics and nothing close to a finished product. Xbox tested it in June, then decided a month later not to move forward. Crucially, Rebs Gaming stresses that cancelling the prototype doesn't mean Activision is out of the picture entirely: Microsoft is still reportedly exploring the idea, just hasn't greenlit anything yet.

The backdrop here matters. Microsoft completed its $68.7 billion acquisition of Activision Blizzard in 2023, bringing every Call of Duty studio — including Sledgehammer — under the Xbox umbrella. Despite that, the two sides have largely operated independently since the deal closed. Now, with Xbox announcing 3,200 layoffs across its gaming division and publicly reassessing its broader strategy, there's growing pressure to find smarter ways to use the studios it already owns. Halo Studios, meanwhile, has reportedly leaned heavily on outsourcing for Campaign Evolved, and the thinking seems to be that model could extend to future titles.

Whether Sledgehammer or another Activision team eventually takes on a Halo project remains an open question. For now, the prototype is dead, the broader conversation is apparently still alive, and nothing has been officially confirmed by Microsoft or any of the studios involved.