The first half of M2's "done when" (a scene loads and saves) rather
than the whole milestone — the asset hot-reload half is a comparably
sized, separate chunk of work, staged on its own rather than crammed
in alongside this.
SceneFormat replaces WorldDumper rather than sitting next to it:
there was never a real reason for "what an agent reads to check a
frame" (the existing --dump) and "what a scene file actually is" to
be two different JSON shapes, and keeping them one removes the
question of which shape a save/load round trip is supposed to match.
Moved from Engine.Kernel.Diagnostics to Engine.Kernel.World to match —
this is core content loading now, not a debug tool that happens to
also serialize things.
Components are tagged "TypeFullName, AssemblyName" (partial-name
form, deliberately no version) so Type.GetType resolves them against
whatever's loaded regardless of an incidental version bump on the
plugin that defines them — full four-part AssemblyQualifiedName would
have made every saved scene brittle against that. Loading a scene
whose component type isn't loaded fails loudly, naming the missing
type, rather than silently dropping data.
New kernel API this needed: GameObject.AddComponent(Component) —
attaches an already-constructed instance, for a caller (the
deserializer) that only has a runtime Type from a file, not a
compile-time T. Deserializing straight into a real instance via
JsonSerializer.Deserialize(json, componentType) and attaching that is
simpler and more certain than constructing an empty component through
reflection and then trying to populate it after the fact.
Engine.Host: --scene now does something (was an explicit "not
implemented yet" since the very first CLI pass) — loads additively
after every plugin in --project, since a scene's component type tags
only resolve once the plugin defining them has loaded its Contracts
assembly.
Verified beyond the round-trip unit tests: two separate real CLI runs,
sandbox.echo both times. Run 1 ticks 3 frames and dumps a scene
(Ping.Count: 3). Run 2 loads that scene fresh alongside its own
newly-seeded Ping (Count: 0) and ticks 2 more frames — dump shows
Count: 2 for the fresh one and Count: 5 for the loaded one. Not just
"the file round-trips" — the loaded component's state kept being a
real, live, Scheduler-ticked object across the save/load boundary.
44 tests in Engine.Kernel.Tests now (up from 40 — 3 carried over from
WorldDumperTests plus 4 new round-trip/error-path tests), 8 in
Engine.ConformanceHarness unaffected. All green on a clean build.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N1qPfzq8TDCUMFMV3UwV5N
