Alongside the announcement of Halo Infinite at E3 2018, 343 Industries touted the usage of the internally developed Slipspace Engine to achieve the ambitious vision the studio had for the game. The Slipspace Engine was also supposed to make the developers' job easier, as noted by former 343 Industries head Bonnie Ross in a 2019 interview with IGN.

　　The Halo engine is a very technical, engineering-focused engine. It's super hard for creatives to work in. It's super hard for a lot of creatives to work at one time. We did a ton of work, on Halo 4, on the engine, to get it to look... I think it looked amazing for being on the last generation on the last year of the platform. We promised the team we would do the work on the tools, and pipeline, for Halo 5, so it wasn't such a challenging environment to develop on. You know... 'best-laid plans'... we didn't do that, and the team, rightfully so, basically called us on it.

　　One, we want to do more with Halo... and two, we want to have a team that can do their best creative work within our engine. So it really was taking the time off and, as we announced the Slipspace Engine last year, it is all to make sure we're building the platform for the future of Halo.

　　However, the Slipspace Engine didn't deliver on those promises. The development of Halo Infinite was famously troublesome, forcing Microsoft to delay the game out of the Xbox Series S|X launch as it was not nearly ready in late 2020.

　　The game was only released in late December 2021, and it had quite a few performance issues, to boot. That was just the tip of the iceberg, anyway, as 343 Industries had to make massive cuts (two-thirds, according to reports) to ship the game, and some core features like Forge mode and co-op campaign still haven't been added to Halo Infinite.

　　It's, therefore, not that surprising to hear a new rumor from Jeremy Penter (ACG) about 343i choosing to abandon the Slipspace Engine in favor of Epic's Unreal Engine.

　　I can only confirm that many sources are saying this and very clear that it's already been decided and Halo is for sure switching to Unreal.

　　I feel like it's time for other switches behind the scenes including people leaving and their past problems.

　　Unreal is a great choice. https://t.co/8KxMqREWIk

　　— ACG (@JeremyPenter) October 2, 2022

　　For his part, Jez Corden could not corroborate but did say it is likely. He also noted that Director of Engineering David Berger has recently left the company.

　　Just to clarify, I KNOW for a fact D. Berger has left 343i, what I'm inclined to believe is the rest of Sean's report about Tatanka potentially switching engines, and potentially being separate, but no hard confirmation yet.

　　— Jez (@JezCorden) October 2, 2022

　　The first Halo game to use Unreal Engine could therefore be Tatanka, in development at Certain Affinity and rumored to be inspired by the Battle Royale genre.

　　It seems like in-house engines are on the way out, as Halo could be the last in a long list of prestigious IPs switching to Unreal Engine, including The Witcher and Tomb Raider. Even SEGA's Ryu Ga Gotoku Studio is trying UE with the Like a Dragon: Ishin remake.