Add an Emulator Platform

Use this workflow for a new emulated system or libretro core. A game integration only adds data under stable_retro/data/ and should follow docs/integration.md instead.

Gather requirements

Before editing, establish:

• Stable Retro platform identifier and game-directory suffix.
• Core directory slug and expected libretro library basename.
• Upstream repository, pinned revision, license, and redistribution terms.
• ROM extensions, libretro joypad layout, RAM regions, serialization behavior, and BIOS needs.
• Supported host matrix: Linux, Windows, macOS x86_64, and macOS arm64.
• A legally redistributable smoke-test ROM, or a documented manual-test substitute.

Compare one nearby simple platform manifest and one platform with similar rendering, BIOS, or architecture constraints. Do not assume a core's standalone defaults are suitable for deterministic, headless reinforcement learning.

Implement the platform

1. Vendor the pinned core under cores/<platform>/. Preserve upstream licensing and avoid unrelated source edits.
2. Ensure the core's Makefile produces <core_name>_libretro with the host shared-library suffix. The top-level add_core function expects this exact name.
3. Copy the manifest template to cores/<platform>.json and adapt it. The top-level key is the public platform identifier; lib is <core_name> from CMake.
4. Keep buttons and keybinds aligned to libretro joypad IDs. Use null for unsupported positions and list only valid button names in actions.

5. Validate the manifest before compiling:

   python .github/skills/add-emulator-platform/scripts/validate_manifest.py cores/<platform>.json

6. Add add_core(<platform> <core_name>) in CMakeLists.txt. Guard it when host support or system libraries are conditional.
7. Add only required deterministic core options to s_envVariables in src/emulator.cpp. Prefer software rendering unless the core truly requires ENABLE_HW_RENDER.
8. Add the platform suffix to setup.py only when packaged game integrations use that suffix. Core JSON and shared-library packaging is already generic.
9. Update tests/emulator.cpp with manifest loading and an emulator smoke parameter when a redistributable fixture exists. Otherwise add lower-level mapping coverage and record manual load, frame, audio, reset, and serialization evidence.
10. Update docs/supported_emulators.md and, when users can import games for the system, the supported ROM types in docs/integration.md.

Validate incrementally

Build the new core first:

cmake -DCMAKE_DISABLE_FIND_PACKAGE_CapnProto=TRUE .
cmake --build . --target <platform> -- -j2

Then run the native suite:

CMAKE_BUILD_PARALLEL_LEVEL=2 scripts/test-cpp.sh

Run relevant Python tests and repository checks:

scripts/test-python.sh
python -m pre_commit run --files <changed-files>

Use the completion checklist before finishing. Clearly report any host platform or hardware path that was not tested.