Companions of Xanth

This in-progress Linux port plays through Fairy Nuff's recipe and shows 122/1000 points. The full game is not completable yet.

About this project

This is a passion project. I'm working hard on it, but it's made for fun and for everyone's enjoyment — free, non-commercial, and made by a fan. If you enjoy it, that's the whole point.

Milestones and progress

Public releases happen at milestones. The Milestones wiki page lists what each release reached, where the port honestly stands, the proposed next milestone and a dated changelog. Between milestones the port is developed privately; the decompilation stays public here, and releases ship the Linux package only.

How to play

1. Download the Linux x86_64 release asset named xanth-port-v0.1.0-alpha.5-linux-x86_64.tar.gz from Releases and extract it to ~/Games/companions-of-xanth/port/. The package contains the port and checkpoint-building tools, but no game files. Linux uses your system SDL2.

2. Supply files from your own copy: XANTH.EXE and the 90 runtime files listed in the package's DATA_FILES.txt, all directly in one folder. Copy them from an original disc or an installation you already own. GOG currently lists Companions of Xanth in its Dreamlist rather than as a store product, so a GOG copy is not presently offered there: GOG Dreamlist. Put your files in ~/Games/companions-of-xanth/data/. If the port cannot find a valid folder, Linux opens a chooser; a successful selection is checked against SHA-256 pins and remembered locally.

3. Double-click the package's launch.sh, or run:

   ~/Games/companions-of-xanth/port/launch.sh
   

   Pass a different data folder as its first argument, or set XANTH_DATA.

Linux requires installed SDL2 (libSDL2-2.0.so.0) and glibc 2.34 or newer. The verified Bazzite Alienware already provides SDL2.

Dev menu

On in this preview: press F12 or Back+Start on one controller. Set dev_menu=0 in your port config or use --no-dev-menu to hide it. XANTH_CHEATS=0 hard-disables it. The menu offers 8 verified warps and 7 finish-step entries after you build and verify your own local checkpoints. See DEV_MENU.md for the packaged tools and instructions. No cheats are included. A lone Back or Start acts on release. With the menu on, fullscreen and CRT scanlines are in Options instead of the --hotkeys F10/F11 shortcuts.

Steam Deck / Game Mode

In Desktop Mode, add launch.sh from the extracted package to Steam as a non-Steam game. Set Start In to the package folder and Launch Options to /home/deck/Games/companions-of-xanth/data, then launch it from Game Mode. This is a native Linux app; leave Steam's Force Compatibility Tool option disabled.

Controllers are detected automatically. The left stick moves the pointer, A clicks, X right-clicks, D-pad sends guest arrows, Start sends Enter, and Back opens help. Alpha.2 includes reconnection and Steam/InputPlumber handheld fixes. Use --no-controller or controller=false to disable controller input.

Optional settings include --pixel-perfect, --fit, --crt, --linear, --fullscreen, --handheld, --hotkeys, --soundfont <your.sf2>, per-channel --volume-* N, and hash-keyed --mods <directory> with separate font/graphics switches. Controller input and the preview dev menu are automatic; graphics and audio enhancements are off by default; see docs/ENHANCEMENTS.md.

Troubleshooting and FAQ

• Missing files: choose the directory with XANTH.EXE and all 90 runtime files directly inside it, not the parent disc folder.
• Hash mismatch: the files are incomplete or from another release. This port currently accepts only the pinned XANBUD set; see the package's DATA_FILES.txt and select a matching installation.
• No folder chooser: install kdialog (KDE) or zenity (GNOME), or run launch.sh /path/to/game-data from a terminal.
• Can I finish the game? Not yet. The tested route reaches Fairy Nuff's recipe (122/1000); later regions and the ending are incomplete.

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Companions of Xanth - Byte-Verified Decompilation & Native Port

Companions of Xanth is being reconstructed from the locally supported XANBUD release. The EXE and OVL rebuild have documented byte-match evidence; that does not establish that every function has semantic source or that the port is 1:1. The native port is in progress on Linux, with the Windows MSVC build currently failing its CI gate. See known divergences before treating any behavior or platform as complete. Retail game assets are required.

tools/verify.py reports whole-program BINARY-MATCH for this disc’s XANTH.EXE and XANTH.OVL. The source index has 2,844 units and currently contains 0 raw _emit dump units. Its measured kinds are 442 unaided-C, 959 mnemonic assembly, 528 Watcom assembly, and 915 transcribed-data units. These figures describe the source index; they are not a semantic function-completion percentage.

The port executes the supplied retail EXE/OVL in its own VM, with a growing set of source-backed native hooks, including partial paths. Most guest code remains interpreted. Whole-image BINARY-MATCH is a separate decompilation/rebuild measure; see the current port handoff.

The retail executable and overlay are authority. Preserve behavior, bugs, layouts, overlay placement, and calling conventions. A modern port must be derived from this decompilation and must not become a replacement implementation. No game data or proprietary toolchain artifacts belong in Git.

• Intent
• Constraints — the written bar; do not weaken it to make a change pass
• Capability map
• Target and provenance
• Reproduction
• Matching definitions
• Toolchain evidence
• Session handoff
• Known divergences
• License notes

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Native Cross-Platform Port (in progress)

Experimental release packages contain the port and documentation only. Supply your own matching game files with --data. See release setup instructions and prerelease notes for requirements and limits.

Status: verified routes extend into the Region of Fire, including charcoal collection. The full 1,000-point finale remains unverified. The port executes the retail XANTH.EXE under its own 16-bit CPU and DOS/BIOS layer. A scripted walkthrough plays Mundania, the cavern, the Isthmus catapult, and the eye screen. At Fairy Nuff's booth the game's own status panel reads 122 of 1000, with the recipe in inventory. There is no reimplemented game logic.

What works today

• Boots the retail image: RTLink pages its own overlays, the game loads its own databases, art, fonts and music.
• VGA mode 13h with the game's own palette fades and the animated intro cutscene.
• Mouse and keyboard: hover highlights object names, verb-then-object clicks produce real parser output from XANTHSTR.DAT.
• AdLib music.
• Multi-room navigation via the compass.
• Save and restore through the game's own system menu, verified byte-exact: save, change the world, restore, save again, and the two save files differ only in the name field.
• Deterministic input traces with frame-hash checkpoints (tests/traces/*.xit), plus a soak that runs ~1.5 billion instructions of play with no faults.
• Mundania, the cavern, the catapult, and Fairy Nuff. Nine walkthrough segments: the opening chapter, Nada, the cavern, the village key, the log jam, the catapult, the pail, the eye screen, and Fairy Nuff's recipe. The status panel at his booth reads 122/1000. All of that is retail code.

Digitized sound follows MUSIC= in LEGEND.INI. real plays RealSound effects (the kitchen phone opens PHONE.RS and 44,159 samples reach the mixer). blaster also streams XANTH_01.VOC through DMA. adlib, the default the golden frames were recorded against, plays music only.

Not yet: mixing Fairy Nuff's solution and dousing the censor-ship, then the Void and the regions through the 1,000-point ending.

What was replaced, and why

port/src/engine_glue.c was a hand-written text adventure — three hardcoded rooms with hand-typed narration — that loaded XANTH.OVL and never executed a byte of it. That is exactly what CONSTRAINTS.md forbids. An earlier audit called it complete against a written criterion of "boots to the title screen"; its own caveats record that no playthrough was attempted. Its overlay model was also wrong: it read the 62 directory size fields as a byte partition of the payload, but they sum to 43,284 against a 325,595-byte payload. xanth_port no longer links it.

Where it is going

A two-stage rebuild, derived from the matched source rather than reimplemented:

• Stage 1 — run the retail code. A 16-bit x86 core plus DOS/BIOS/mouse shims execute the real XANTH.EXE against the existing SDL2 HAL. The RTLink/Plus overlay manager is ordinary 8086 code inside the EXE, so it pages its own overlays through faithful INT 21h file I/O — no overlay logic is reimplemented. The Mode 13h framebuffer is already mapped at g_dos_mem + 0xA0000, so guest VGA writes need no translation.
• Stage 2 — statically recompile. Retail bytes are decoded to portable C against the same HAL, function by function, each validated by co-simulation against the interpreter, until the interpreter is no longer linked into the release build.

CONSTRAINTS.md carries the precise definition of "100%" for the port and the ratchets that enforce it.

Building

Prerequisites: cmake, gcc or clang, libsdl2-dev.

./scripts/build_port.sh                                   # build
ctest --test-dir build                                    # tests
./build/xanth_port --data game_cd/XANTH --saves build/saves

Escape quits; --scale N sets the window size. See docs/PORT.md for the architecture, the input-trace format, and the current milestone state.

Hash-keyed asset replacements are opt-in: pass --mods mods and place each replacement at mods/<lowercase SHA-256 of the original asset>. With no --mods argument the replacement lookup is disabled. Cheats and a persistent user configuration are not implemented yet.

Windows 11 (MSVC or MinGW):

cmake -B build -S port
cmake --build build --config Release

Note that the Windows build has so far only been verified by static inspection, not compiled and run. Wiring it to a CI runner that actually executes it is part of the port work.

Supplying Game Assets

No copyrighted game assets, data files, or proprietary binaries are in this repository.

Supply the runtime files from the locally supported XANBUD release in game_cd/XANTH/, or point --data at their directory:

./build/xanth_port --data /path/to/game_assets

Before startup, the port checks XANTH.EXE and the 90 runtime files against the recorded SHA-256 pins. Missing or changed files stop startup with a clear message; supply the matching files with --data. The installer and its setup lists are not needed at runtime. Game assets remain on your machine and are not distributed with this project.

Decompilation Verification

python3 tools/coverage.py                 # reports 0 remaining dump units
python3 -m unittest discover -s tests -v  # runs decompilation unit tests
python3 tools/verify.py                   # whole-program byte-accurate verification

Verification requires the legally supplied disc described in the target notes. Extracted payloads remain local and ignored. No license is asserted over Legend Entertainment, SSI, or related materials.