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+# Continuumatrice product migration and coexistence
+
+This is a **product fork**, not a renamed Cockatrice binary. The upstream Cockatrice runtime, MTG cards, profiles, update feeds, launchers and installers must remain independent.
+
+## Runtime identity
+
+| Component | Continuumatrice |
+| --- | --- |
+| CMake target / installed binary | `continuumatrice` |
+| Linux build output | `build/cockatrice/continuumatrice` (source folder remains upstream named) |
+| Linux app launcher | `continuumatrice.desktop` |
+| Qt application | `Continuumatrice` |
+| Qt organization | `Continuum Universes Studio` |
+| User data on Linux (default XDG) | `~/.local/share/Continuumatrice/` |
+| User cache on Linux | `~/.cache/Continuumatrice/` |
+| Single-instance socket | `ContinuumatriceSingleInstance` |
+| Deep-link scheme | `continuumatrice://` |
+| Card XML root (native) | `continuumatrice_carddatabase` version `4` |
+| Card XML root (import compatibility) | `cockatrice_carddatabase` version `4` |
+| Fork server executable (when built) | `continuumatrice-server` |
+| Fork server config | `continuumatrice-server.ini` |
+
+Both `<cockatrice_carddatabase version="4">` and `<continuumatrice_carddatabase version="4">` load, but new XML saved by the fork uses the new root. The parser format and gameplay features still derive from the Cockatrice codebase; this change is not an automatic rules engine.
+
+The source directory `cockatrice/`, common `libcockatrice_*` targets, and historical class names are left as *internal* implementation details to avoid needless churn and protocol breakage. They do not identify the installed product.
+
+## Card data
+
+- A new profile receives a **valid empty XML v4 starter database**, with no MTG cards.
+- Put Continuum Universes card sets in `~/.local/share/Continuumatrice/customsets/`, or import from the Card Database menu.
+- The default image download URL list is empty. Older fork profiles have known Scryfall/Gatherer URLs removed while custom URLs are preserved.
+- The upstream MTG Oracle importer is not shipped: `WITH_ORACLE=OFF` is the default and `WITH_ORACLE=ON` is deliberately refused until there is a replacement.
+- The inherited first-run Magic importer and automatic public-server/Commander-bracket fetches are disabled.
+- Application release checks point only to the Continuumatrice GitHub repository; automatic update checks are off until a fork release is available.
+
+**An independent Continuum Universes catalogue importer remains to be implemented.** Static XML v4 import is already available.
+
+## System integration
+
+Linux: `continuumatrice` binary, independent .desktop file, own SVG icon and `continuumatrice://` handler. No takeover of `.cod` or `cockatrice://`.
+
+Windows: packaging script uses a separate installation directory, uninstall registry key, executable, URL protocol and process-lock detection. It must **never** remove or overwrite `cockatrice.exe` or the upstream `Uninstall\Cockatrice` key.
+
+macOS: separate app executable/bundle identifier and `continuumatrice://` link handling; `.cod` handler removed to avoid competition with Cockatrice.
+
+The Windows and macOS installers are **not yet verified**. Source and packaging changes should not be presented as validated shipping installers.
+
+## Build
+
+```bash
+cmake -S . -B build --fresh -G Ninja \
+  -DCMAKE_BUILD_TYPE=Release -DWITH_CLIENT=ON -DWITH_SERVER=OFF -DWITH_ORACLE=OFF
+cmake --build build --target continuumatrice --parallel 16
+./build/cockatrice/continuumatrice
+```
+
+An internal compatibility target `cockatrice` still depends on `continuumatrice` to accommodate older CI invocations, but never emits a `cockatrice` executable. Previously compiled copies of `build/cockatrice/cockatrice` are stale.
+
+## Release checklist
+
+- [ ] Configure and compile Continuumatrice with openSUSE Qt 6 using a clean CMake cache.
+- [ ] Confirm `build/cockatrice/continuumatrice` runs and the app name and original SVG icon appear.
+- [ ] Confirm old `/usr/bin/cockatrice`, `~/.local/share/Cockatrice` and MTG card images remain untouched.
+- [ ] Open both clients simultaneously; confirm distinct sockets, settings, card databases, decks and caches.
+- [ ] Load both legacy and new-root XML and verify custom images and Front/Support/Command mapping.
+- [ ] Test Limbo, Refuge and Oblivion card moves, view windows, counters, mirrored positions and reconnect.
+- [ ] Confirm startup does not request MTG artwork, Oracle updates, Commander brackets, or upstream server lists.
+- [ ] Check a `continuumatrice://` link and ensure `cockatrice://` still belongs to MTG Cockatrice.
+- [ ] Install and uninstall user-local Linux app; ensure no MTG desktop-file or icon collision.
+- [ ] Test Windows installer in a VM with upstream Cockatrice preinstalled, including install, upgrade, uninstall and `.cod` association preservation.
+- [ ] Test macOS app bundle identity and installation alongside upstream Cockatrice.
+- [ ] Verify GPL requirements, notice retention and upstream attribution.
+
+**Status:** Committed source changes; no completed Qt compilation, package build, or runtime validation in the assistant environment. Release is blocked pending these tests.