Pure analysis over the ERODED render map: changes zero terrain, adds zero water.
Priority-flood (task-03 family, Barnes heap+pit, 8-connected) with a one-ulp
epsilon so every filled pit keeps a strictly descending routing path — the ~16.5k
erosion pits route through; depressions >= 2 m deep and >= 10k px survive as
terminal basins (70 on the working seed). D8 flow directions on that routing
surface (D8 as a COMPUTATION, not the reverted carving use), Kahn-propagated flow
accumulation, then promotion: TRUE-ocean outlets (WBID 1 only — two of the first
draft's three 'sea-reaching' trunks actually ended in enclosed lagoons, which is
exactly the overclaim the gate must not inherit) ranked by drainage area, top ~3
with outlet separation become trunks; max-accumulation stems; mountain-exit from
sustained along-stem grade; lean deduped tributaries; lean endorheic terminals
credited with per-basin TOTAL inflow (acc at the deepest cell undercounts flat
lagoon beds 10x — measured).
Output: console report + a JSON plan sidecar next to the source blueprint —
deliberately NOT a blueprint section, so the plan cannot masquerade as realized
water. The source .dat is never written (md5-verified). Headless tool, ~21 s
analysis on 8K; RIVERPLAN_* env dials.
Seed 1280587109 findings for the gate: 3 ocean trunks spread west/north/east
(436k/409k/325k px); the island's five LARGEST systems (1.1M-2.3M px) are all
endorheic — three end in big enclosed lagoons (classify lakes, 19-20 m basins),
two in dry pans; 62.9% of land does not drain to the open ocean, the drainage
restatement of task 18's 'erosion cannot cut the lowlands'. The 2.27M-px giant
terminates in the SE lagoon ~1.1k px from the southernmost town (filed south
report, not enforced).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
