The four Jak games, native on the PC.
Phaethon is a port of Jak and Daxter, Jak II, Jak 3 and Jak X: Combat Racing to Windows, built from the games' own code. Each game is decompiled from your disc into GOAL, the language Naughty Dog wrote them in, compiled for x86-64 and run on a runtime that plays the part of the PlayStation 2. The launcher installs that runtime, imports each disc and keeps everything up to date.
Every game starts retail-faithful: the same physics tick, the same field rate for the audio-synced cutscenes, the same heaps and load order. Anything that changes what the console did lives behind a toggle, in a remastered version that never touches the faithful one.
Faithful ports of all four
What the PlayStation 2 build did, frame for frame where it can, checked against captures of the console.
Faster on all four
A consequence of the faithful port rather than at its expense: the frame's work measured and trimmed.
A remastered version of all four
Higher frame caps, native widescreen, texture packs and upscalers, all behind a toggle.
Jak X, for the first time
The one game no port had reached, brought up from its disc the same way the trilogy was.
Measured, never guessed.
A change lands when the runtime and the console agree, and not before. That rule shapes everything about how the work is done: what counts as evidence, what a review has to show, and what a build has to pass before it reaches a player.
Decompile
The decompiler reads the object code on the disc and writes GOAL source for it. Each file is typed and read against the original until the two say the same thing, and the source is what gets built, so nothing runs that cannot be read.
Compare
A frame oracle holds reference frames from the console's own scenes. Every change that reaches the picture is compared against them before it lands, and a pass that moves a pixel it should not have moved does not land.
Land
Reviewed branches reach the integration line on trains, under one pipeline run and one CI run each. Every runtime change is read through three separate review lenses before it rides. The pipeline's verdict and the CI result travel with the merge.
AI assistance is part of the work, for speed and accuracy, and it is held to the same bar as every other contribution: every change is read, tested and checked against the console before it lands.
from the maintainerAI assistance is how I work, here and in everything else I build, and I have spent years tuning it: learning where it is fast and where it lies, what it has to be told and what it has to be refused, and how to make it show its evidence instead of its confidence. I will not spend five months by hand on what it does well in an hour, and I will not accept its hour without reading it. The standards in the repository are the public ones. Mine are stricter: every claim traced to an artifact, every fix landed with the test that would have caught it, nothing shipped on a tool's word.
One maintainer, a small circle.
Phaethon is maintained by one person, with contributors and testers who bring discs, bug reports and fixes. Development happens on the project's own forge, and a mirror of the integration line follows on GitHub.
Source
The runtime, the compiler and the decompiler, with every train and its verdict.
git.snalpha.com/alex/phaethonBugs
Findings go on the forge in the project's own template: what was observed, the evidence, what was not verified.
the issue trackerCommunity
Testers and players compare notes, share captures and report what a disc did.
The Discord server is on its way.Standing on OpenGOAL.
The trilogy's decompilation is OpenGOAL's work over many years, and Phaethon would not exist without it. Phaethon began as a fork of OpenGOAL in September 2026 and carries its own direction from there: retail-faithful fixes for the trilogy, the Jak X port, the Vulkan renderer and the kernel work. Nothing here goes back upstream, and nothing here is upstream's responsibility.
Naughty Dog made the games. Phaethon is an unofficial fan project, not affiliated with, endorsed by or associated with Sony Interactive Entertainment or Naughty Dog. It ships no game data and never will. You need your own copy of each game.
Read it, build it, play it. Not take it.
Two licenses cover the repository, by who wrote what. Phaethon's own work, everything added since the fork left OpenGOAL's jak-project, is under the PolyForm Strict License 1.0.0: you may use it, build it and play it; you may not distribute it, and you may not make changes or new works based on it. The code inherited from OpenGOAL stays under the ISC License with the OpenGOAL Team's notice, as that license requires. The games' own code belongs to its makers, and nothing here ships their data.
from the maintainerThe strict terms have one reason. Most of my work here is AI-assisted, and every commit says so. When that became known, parts of the community answered with hostility rather than with a reading of the work. I publish the source so that anyone can read it, build it, check it against the console and play it. I do not publish it so that it can be folded into other implementations or built on by people who would not have it exist. That is the whole of it. I may loosen the grip as the work proves itself. Today, this is where it stands.
You may
Read the source, build it from a checkout, run what you built, play the games from your own discs, report what you find, and contribute under the same terms.
You may not
Distribute Phaethon's own work, or make changes or new works based on it, including carrying its fixes, its decompilation of Jak X or its renderer into another implementation.
Inherited code
Everything that came from OpenGOAL keeps its ISC license and its copyright notice. The fork takes nothing from upstream since it left and sends nothing back.
Asked often enough to answer here.
What is Phaethon and how is it different from OpenGOAL?
Phaethon is a hard fork of OpenGOAL's jak-project that ports Jak and Daxter, Jak II, Jak 3 and Jak X: Combat Racing natively to PC, built on OpenGOAL's decompilation of the original PlayStation 2 code. Two rules set it apart from the project it came from: no compatibility layer, ever, so the game's own code runs on the machine's own interfaces, Vulkan directly, the platform's own threads, files and sockets directly, rather than through a shim kept because removing it is work; and no unanswered TODO, so every deferral in the tree carries the issue that will close it, and a checker refuses a new one without one. This fork develops independently of upstream: it does not send work upstream and does not take upstream's.
Do I need to own the games?
Yes. Phaethon reads the files from your own disc of each game; it does not ship them, and no game data is distributed with the port. Jak X: Combat Racing and the Jak trilogy are owned by Naughty Dog and Sony Interactive Entertainment, and this project is not affiliated with either. See Getting started for how the launcher takes a disc image from there.
Which games are supported, and how far along is each?
Jak X: Combat Racing is playable: the story, the races and the arenas run, with bring-up work continuing on the remaining minigame and event roads, tracked on the bring-up milestone. Jak and Daxter, Jak II and Jak 3 all run, with retail-behavior fixes carried in this fork.
What does retail-faithful mean, and why is the console the reference?
Retail-faithful means the port aims to do what the PlayStation 2 build did, frame for frame where it can: the same physics tick, the same field rate for the audio-synced cutscenes, the same heaps and load order. Faithfulness is the first of Phaethon's four goals, and the console is the reference whenever the port and the original disagree, so where the two differ, the console is treated as right.
What is the remastered version, and does it change the faithful one?
The remastered version is everything beyond retail: higher frame caps (60, 120, 144), a native widescreen picture with the HUD anchored to the edges instead of letterboxed, texture packs, and DLSS or FSR upscaling. It lives entirely behind a toggle and never touches the retail-faithful preset, so turning it on or off does not change what the faithful mode does. See Settings and the remastered toggles for where the toggle lives.
Which platforms does Phaethon run on?
Windows is the platform it is built and played on daily. A Linux build compiles in continuous integration on every landing and boots. macOS and the Steam Deck are on the Roadmap.
Is there online play for Jak X: Combat Racing?
Not yet. Online multiplayer for Jak X is a Roadmap item rather than something the port ships today.
Can I mod it?
Not in a first-class way yet. Mod APIs are on the Roadmap.
Can I use AI to contribute?
Yes, and it is encouraged. Most of Phaethon's own work has been done with AI assistance, disclosed with an (AI-assisted) marker in the commit message, and every contribution, AI-assisted or not, is held to the same evidence standard and judged by what it does rather than how it was produced. Nobody is turned away for the tools they used.
Can I fork or redistribute it?
Two licenses cover this repository, by who wrote what. Phaethon's own work, everything added since the fork left OpenGOAL's jak-project, is under the PolyForm Strict License 1.0.0: you may use it, but you may not distribute it or make changes or new works based on it, the source exists to be read, built and played, not taken. The code inherited from OpenGOAL stays under the ISC License with the OpenGOAL Team's copyright notice, as that license requires.
What about the third-party parts, like DLSS, FSR, the fonts and the upscaler weights?
None of them sit inside this repository's own source. NVIDIA's DLSS headers and library are fetched at configure time, only when the DLSS build option is on. AMD's FSR SDK, MIT licensed, is cloned and built the same way, at the tag the build pins, v1.1.4 as of this writing. The debug window's two fonts, JetBrains Mono and Noto Sans JP under the SIL Open Font License, and its lucide icon face under the ISC License, ship as assets and load at run time. The cutscene upscaler's weights, Philip Hofmann's 2xNomosUni_compact_multijpg_ldl network, ship under Creative Commons Attribution 4.0, converted from float32 to float16 for the runtime but not retrained.
Where do I report a problem?
Through the issue forms: separate forms for a retail divergence, a crash or hang, a performance problem, a general bug, a feature request, tooling or CI, documentation, and an agent finding with its own evidence trail. See Reporting a retail divergence for how that form works field by field.
Does Phaethon send work upstream, or take work from it?
Neither. This fork does not send work upstream and does not take upstream's; it is its own line, and every issue and pull request for this code is tracked on this forge rather than on OpenGOAL's own discussion board or Discord.
Is Phaethon compatible with OpenGOAL?
No, and it is not meant to be. The two shared a tree until September 2026 and have diverged since: Phaethon runs on its own kernel changes and a Vulkan renderer, builds each game with its own compiler, and its launcher installs only its own runtime. A game built by one does not run on the other, the launchers do not see each other's installs, and mods or texture packs made for one are not tested on the other. Save files are the game's own format in both, and nothing here has tested moving them. Anyone who wants OpenGOAL should use OpenGOAL; the two do not need each other.