The SDK zip is 24 MB of headers, examples and tools we never build. The runtime
dependency is one native library, so scripts/steam-sdk.sh extracts exactly
sdk/redistributable_bin/win64/steam_api64.dll into steam/ (gitignored, like ffmpeg/ —
the script is the audit trail) and writes steam_appid.txt = 480, Valve's Spacewar app,
so SteamAPI.Init() resolves an app id locally before LlamaCasty has one of its own.
Two csproj details that would have cost a debugging session:
- Link="steam_api64.dll" puts it BESIDE the exe; without Link, None items keep their
relative path and it lands in steam/, where the loader does not look.
- ExcludeFromSingleFile, for the same reason ffmpeg needed it: a native DLL otherwise
gets swallowed into the single-file bundle and cannot be loaded at runtime.
steam_appid.txt is Debug-only — Valve's guidance is not to ship it — and the publish
output confirms it: dll present at the root, no appid file, exe still 127 MB (proof the
DLL was not bundled).
Also queued, as asked: preview undo (Ctrl+Z / Ctrl+Shift+Z) in edit mode, noted as the
partner to the defaults-vs-current split — undo covers the slip, defaults cover the mess.
