Addresses the Hoshe (QA) + Tyre (architecture) review of the SeedChain/cascade
work:
- Golden was pinning an empty river network (128x64 produced 0 river cells).
Bumped to 256x128, where GJ1c yields a real network (93 river cells, 19
mouths) — Layer 1's rivers are now actually guarded, not just attractors.
- SeedChain::for_body(world_seed, body_id) + fnv1a_64: the single canonical
body_id(String) -> u64 path (FNV-1a, the repo convention), so callers can't
derive divergent worlds from the same seed via different ad-hoc hashes. The
golden now uses it.
- Stability guards: seed_domain_discriminants_are_pinned test (CI fails if a
SeedDomain tag is renumbered); AttractorType gains #[repr(u8)] + explicit
discriminants (it's cast as a sort key in features.rs).
- Tests: SeedChain::root(0) non-degenerate; run_cascade error path (missing
file -> Err, not panic).
- Comments: clarified the id=0 derivations (sibling separation is caller-side
via the per-district/quarter chain; #957 threads the index), tightened the
all_district_types reachability comment (it pins the seed-0 sequence, not a
probabilistic claim), and noted the golden's WORLD_SEED is cosmetic at
Layers 0-1 + the x86_64 f32 capture caveat.
Deferred with reason: the run_cascade -> CascadeInputs struct refactor (Tyre)
is left for #954 — designing Layer-2's context shape now would be later-phase
detail, and there's a single caller to migrate then. EntityRng keeps its
domainless combine (migrating is stream-changing) — noted in D-224.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
New top-level seed module that owns every deterministic-RNG primitive:
- splitmix64 — the one canonical mixer (was duplicated as a private fn in
simulation/rng.rs; EntityRng now imports the shared one, no behavior change)
- AtlasRng — moved here from atlas/rng.rs (it is a generation-RNG primitive,
not atlas-specific); atlas now depends on seed, not the reverse
- SeedDomain — append-only domain tags (Body/Layer1Topography/Layer3Settlement/
Layer4Quarter/Block/Npc) for collision-proof per-domain seed separation
- SeedChain — root(world_seed) → derive(domain, id) → atlas_rng()/seed(), per
the D-224 formula splitmix64(self ^ splitmix64(domain)) ^ splitmix64(id)
Structural move only — SeedChain is not yet threaded through the cascade
callers (skeleton_gen still uses ad-hoc wrapping_add pre-mixing); that is the
next step. Unit tests cover the splitmix64 known-vector, avalanche,
determinism, domain/id separation, and chain composition.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.7