diff --git a/tools/climate-diag.ts b/tools/climate-diag.ts
index e1c06caa..bba999ac 100644
--- a/tools/climate-diag.ts
+++ b/tools/climate-diag.ts
@@ -15,9 +15,8 @@ import * as fs from 'fs'
 import * as path from 'path'
 
 import type { GridState, ScenarioConfig, EcologicalEvent, TurnStats } from '../packages/engine-ts/src/types'
-import { generate as generateMap } from '../packages/engine-ts/src/MapGenerator.generated'
+import { WasmClimatePhysics, WasmMapGenerator, WasmGrid } from '@magic-civ/physics-rs'
 import { GRID_WIDTH, GRID_HEIGHT } from '../packages/engine-ts/src/HexGrid'
-import { ClimatePhysics } from '../packages/engine-ts/src/ClimatePhysics.generated'
 import { computeTurnStats } from '../packages/engine-ts/src/runner'
 import { SCENARIOS } from '../packages/engine-ts/src/scenarios'
 
@@ -106,14 +105,26 @@ const SEED = 42
 
 process.stderr.write(`Running "${scenario.name}" for ${totalTurns} turns (reporting every ${every})...\n`)
 
-const grid: GridState = generateMap(SEED, GRID_WIDTH, GRID_HEIGHT, terrainCache, params, 'continents')
-const physics = new ClimatePhysics(params, terrainCache, spec)
+const paramsJson = JSON.stringify(params)
+const terrainJson = JSON.stringify(Object.fromEntries(terrainCache))
+const specJson = JSON.stringify(spec)
+
+const mapGen = new WasmMapGenerator(paramsJson)
+const wasmMapGrid = mapGen.generate(SEED, 'continents')
+let grid: GridState = wasmMapGrid.toJSON() as GridState
+wasmMapGrid.free()
+mapGen.free()
+
+const physics = new WasmClimatePhysics(paramsJson, terrainJson, specJson)
 const worldAge = scenario.worldAge ?? 0
 
-// Phase 1: geological history
+// Phase 1: geological history — run in WASM
+let wasmGrid = WasmGrid.fromJSON(grid)
 for (let t = 0; t < worldAge; t++) {
-  physics.processStep(grid, t, SEED)
+  physics.processStep(wasmGrid, t, SEED)
 }
+grid = wasmGrid.toJSON() as GridState
+wasmGrid.free()
 
 // Phase 2: scenario init
 scenario.initMap(grid)
@@ -123,9 +134,11 @@ const rows: TurnRow[] = []
 let baseTemp = 0
 let baseMoist = 0
 
+wasmGrid = WasmGrid.fromJSON(grid)
 for (let t = worldAge; t < worldAge + totalTurns; t++) {
   const scenarioTurn = t - worldAge
-  const events: EcologicalEvent[] = physics.processStep(grid, t, SEED)
+  physics.processStep(wasmGrid, t, SEED)
+  grid = wasmGrid.toJSON() as GridState
   const stats: TurnStats = computeTurnStats(grid)
 
   if (scenarioTurn === 0) {