Capcom’s REX Plan Fixes a 2,000-Developer Engine Bottleneck

Capcom will keep RE Engine and layer REX tools onto it after more than 2,000 developers hit slower builds on games that have grown too large to iterate quickly. Programmer Tomofumi Ishida laid that out on October 2 at Capcom Open Conference RE:2026 in Tokyo, in a talk on evolving the in-house engine rather than replacing it.

The line that traveled in English was “AI-generation game engine.” Ishida’s Japanese was closer to a game engine of the AI generation, meaning a stack built so models can read the code, write some of it, and run test plays. That is a toolchain brief, and it starts with scale.

REX Layers New Systems Onto RE Engine

Ishida spoke in the opening October 2 session at Ariake Convention Hall, 09:40 to 10:30, under a title about taking RE Engine further for the next generation. Capcom’s own integrated report already names REX as RE neXt Engine and says the plan is to fold new technology in step by step, “rather than completely replacing RE ENGINE.”

Work on RE Engine began in 2014. It first shipped in Resident Evil 7 in 2017, and Ishida said more than eight years of use have left three problems that a fresh coat of features will not fix. Games got heavier. The user base got wider. And AI, he argued, has to live inside the pipeline instead of sitting in a side tool.

Capcom still makes every current title on this one engine, from photoreal horror to anime-style Monster Hunter Stories. That single-stack bet is why Street Fighter 6 and Kunitsu-Gami: Path of the Goddess could both land as Nintendo Switch 2 launch games in June 2025. It is also why a freeze in a shared editor now taxes the whole company.

ENGINE FOOTPRINT INSIDE CAPCOM

• People on the tools: More than 2,000 developers now use RE Engine, including overseas staff and hires who arrived from other engines.
• Games on the stack: More than 27 shipped titles have used it since Resident Evil 7.
• Engine builders: The R&D Foundational Technology Department lists approximately 200 engineers on the engine team, with around 160 on engine development.
• Age of the tools: Development started in 2014; the first shipping game arrived in 2017.

Those 160 people are not the 2,000. The small group tends the engine. Almost everyone else has to live in it, which is the pressure REX is built around.

More Than 2,000 Developers Now Share One Engine

Ishida grouped the pain in three piles, and none of them is “we need the model to draw a monster.” The first is data volume. Scenes got richer, packages got fatter, and the wait after a small change got long enough to slow the day. The second is people. Almost every Capcom developer is on this engine now, including staff who never grew up on it and who need the UI in more than one language. The third is AI itself: bolting a chatbot onto a private dialect is a dead end if the engine cannot be read in a common form.

THE THREE PRESSURES ISHIDA NAMED

• Heavier games: Bigger data made even a small tweak-and-play loop slower, which dragged down iteration.
• A wider bench: Overseas staff and people coming from other engines need tools that are easier to learn and that can show logs in more than one language.
• AI in the pipeline: Fitting models into the actual work steps has become, in his phrasing, a required condition for faster development, not an extra.

That last point is why so much of REX is boring on purpose. If a log is a blob of Japanese text, a model and a new hire in another office both stall. If it is a small ID that looks up a string later, you can translate it, compress it, and search it. The AI talk is downstream of that kind of cleanup.

Capcom is not waiting for a greenfield engine to finish before the next Resident Evil or Monster Hunter ships. Ishida was clear that REX is a set of named systems prefixed RE:, dropped onto the engine that is already in production. The company already tried a full replacement once. It did not take.

What the New RE Tools Are Built to Fix

The October 2 list is a plumber’s inventory. RE:Dox puts many file types through one set of rules so load and edit times come down. RE:UI splits how a control looks from whether it is checked, so a screen with a hundred checkboxes does not keep a hundred full copies in memory, and so tools stop freezing when garbage collection kicks in. RE:Log writes IDs instead of sentences, then pulls the sentence at display time, which shrinks the payload and lets the same ID render in another language.

RE:Flows is the designer-facing piece: visual graphs that compile into a standard programming language, so a play idea can be tried without a full code pass, and so several people can work without the usual visual-script collisions. RE:Runtime batches characters and objects into fixed-size boxes instead of managing each instance alone. RE:C++ sits under that, auto-translating code people like to write into a Capcom dialect the machine can run faster.

REX PIECES NAMED ON OCTOBER 2

RE:UI also has a testing angle that never made the scare headlines. Because the new UI is not glued to a live screen, a program can drive the same controls without a person staring at them. That is how you get automated checks into the editor itself, which is the unglamorous half of “create games together with AI.”

Capcom Posted Its Data Library on GitHub the Same Day

The one piece anyone outside the company can actually download is RE:Dox. Capcom’s technical research account posted it on October 2 as a core REX library, under Apache License 2.0, which allows use and change if the license terms are kept. The README calls it a token-based structured data engine for.NET, not a game editor. It parses JSON, JSON5, CBOR, MessagePack, INI and a native DOX format into a compact token DOM, with TOML, XML, HTML and CSV still in preview.

カプコンの最新データ表現・シリアライズ基盤ライブラリ「RE:Dox」のリポジトリはこちら。
本ソフトウェアはApache License 2.0のもとでご利用いただけます。https://t.co/mkEBgzuxTU

— カプコン技研 公式アカウント (@CAPCOM_RandD) October 2, 2026

On Capcom’s own BenchmarkDotNet numbers, automatic parallel deserialization is up to about 2.8 times faster than System.Text.Json, sequential deserialization up to about 1.8 times, and serialization up to about 1.6 times. On the canada.json set, RE:Dox allocated about 2.56 MB against about 8.53 MB for System.Text.Json. Those are lab figures on named datasets, not a promise for a Resident Evil package, and the repo itself says APIs may still move before a stable public release.

Ishida said some of this is public so other people, and other models, can train on it. That is the odd half of the in-house bet: Capcom will not license Unreal, but it will put a REX library on GitHub so the models it wants in the pipeline have something legal to chew. The engine stays private. The plumbing sample does not.

30,000 Hours of Playtesting a Month, Overnight

The “AI will play the build” slide is not a 2027 sketch. In April 2026, Google Cloud said Capcom’s agents already run 30,000+ hours of autonomous playtesting per month, using Gemini Vision to look at the screen, plus predictive bots that swarm places the game is likely to break. Visual agents are trained to tell a horror-game mood choice from a real failure. Other agents hold old engineering answers so a new hire can query how a veteran fixed a similar crash.

Shinichi Inoue, Capcom’s vice president of game development platform and AI solutions, has described the same loop in plainer terms: agents run while people sleep, then another agent scores the findings against the director’s concept before a human sees the queue. That is the 2,000-person problem in miniature. You cannot staff every branch, every costume swap, and every camera clip with a person who knows the game’s intent. You can, if the engine plays ball, have a model walk the map and only wake someone for the misses that look like they violate the brief.

REX is how those agents stop being a cloud sidecar. If logs, data, and editor state all speak one common language, a test bot can read the same structures a designer just edited. If they do not, you get another translation layer, and the wait Ishida is trying to kill comes back in a new costume.

Capcom’s Line on Finished Art Has Not Shifted

The fear that hit the replies was not about ID-based logs. It was about art jobs and “AI slop” in a Resident Evil cutscene. Capcom has already drawn that line, more than once, and October 2 did not erase it. In a June investor Q&A the company said games have to exceed what players expect, and that the creativity at the core of such experiences should be handled by humans. The working policy is to use generative AI on routine operations so developers can spend more time on that core. It also said it is seeing “a certain degree of effectiveness,” and that hard numbers will take time because game work is messy.

Even top-tier AI still cannot match our creators when it comes to sensibility. That’s the current reality.

Shinichi Inoue, vice president of game development platform and AI solutions

The company has said it will not put AI-generated assets into shipped game content, while it tests the tech in graphics, sound, and programming for speed. That is a narrower promise than “no AI anywhere,” and people who want a total ban will not love it. It is also a different promise from the English headline. Code generation, overnight playtests, and a public data library can all sit inside that policy without a single generated face landing in a build.

The split that kept coming back in the argument over the talk is the same split Capcom is writing into the engine: let models grind the soulless pass, keep people on the pass that needs taste. Whether that holds when RE:Flows is compiling designer graphs into code is a later fight. For now the public artifacts are a.NET serializer and a QA farm, not a texture model.

Panta Rhei and the Rewrite Capcom Will Not Repeat

REX’s caution makes more sense if you remember the last time Capcom tried to throw the engine out. MT Framework carried the company through the 360 and PS3 years. The follow-up was Panta Rhei. Ishida, who had already worked on both MT Framework and RE Engine, later said Panta Rhei’s development was not going smoothly and was getting in the way of Resident Evil 7. He took assets from that effort and redesigned them into RE Engine.

Masaru Ijuin, then Capcom’s senior manager of technology management, had already put the cost of the last hardware jump on the record: work for the new consoles looked eight to ten times heavier than the generation before. The shop wanted an engine that cut a one-hour task toward ten minutes, not a mild trim of MT Framework. The clean-sheet try stalled. The engine that actually shipped was the one built beside a real game, then spread until it was the only stack in the building.

HOW THE IN-HOUSE ENGINE GOT HERE

1. 2014: RE Engine work begins after the Panta Rhei replacement stalls, with Resident Evil 7 as the first live test.
2. 2017: Resident Evil 7 ships on the new engine; Capcom then parks more and more series on the same tools.
3. 2025: The integrated report names REX, RE neXt Engine, as a step-by-step upgrade, not a swap, and lists around 160 people on engine development.
4. April 22, 2026: Google Cloud describes Capcom agents already running 30,000+ hours of autonomous playtesting a month.
5. June 2026: Investor Q&A restates that core creativity stays with people, with generative AI aimed at routine work.
6. October 2, 2026: Ishida details the RE: systems and Capcom publishes RE:Dox the same day.

The pattern is stubborn. Capcom would rather own the engine than rent Unreal, even after it evaluated a commercial engine years ago and walked away. That choice pays off when two Switch 2 launch games can share the same guts, and when a lighting trick in Resident Evil Requiem can be reused elsewhere. It hurts when 2,000 people wait on a compile, or when a log file is useless to the staffer who does not read the language it was written in.

REX is the bill for that choice, itemized. Unify the data. Lighten the editors. Make the logs small and translatable. Let a graph become code. Batch the crowds. Then, if the models can read the same structures, let them write a patch and play the build. Ishida’s close was a future where teams create games together with AI. The files on GitHub are a serializer. The gap between those two sentences is the actual project, and Capcom has not given it a date.