diff --git a/guide/age-of-dwarves/src/vite-plugins/simCachePlugin.ts b/guide/age-of-dwarves/src/vite-plugins/simCachePlugin.ts
new file mode 100644
index 00000000..21924289
--- /dev/null
+++ b/guide/age-of-dwarves/src/vite-plugins/simCachePlugin.ts
@@ -0,0 +1,118 @@
+import type { Plugin, ViteDevServer } from 'vite'
+import fs from 'fs'
+import path from 'path'
+
+/**
+ * Vite dev-only plugin that pre-computes climate simulation scenarios
+ * on the server and serves cached stats+events via HTTP.
+ *
+ * Endpoint: GET /__sim-cache/:scenarioId?seed=42&turns=2000
+ * Response: { scenarioId, seed, turns, stats, events }
+ *
+ * Cache invalidation: clears when engine source or game data files change.
+ */
+export function simCachePlugin(): Plugin {
+  const cache = new Map<string, { stats: unknown[]; events: unknown[][] }>()
+  let engineModule: typeof import('@magic-civ/engine-ts') | null = null
+  let terrainData: Record<string, unknown> | null = null
+  let climateParams: Record<string, number> | null = null
+
+  function loadGameData(root: string): void {
+    const dataDir = path.resolve(root, '../../games/age-of-dwarves/data')
+
+    // Load terrain files
+    const terrainDir = path.join(dataDir, 'terrain')
+    terrainData = {}
+    for (const file of fs.readdirSync(terrainDir).filter(f => f.endsWith('.json'))) {
+      const raw = JSON.parse(fs.readFileSync(path.join(terrainDir, file), 'utf8')) as { terrains?: Array<{ id: string }> }
+      if (raw.terrains) {
+        for (const t of raw.terrains) {
+          (terrainData as Record<string, unknown>)[t.id] = t
+        }
+      }
+    }
+
+    // Load climate params (extract only numeric values)
+    const paramsPath = path.join(dataDir, 'climate_params.json')
+    const rawParams = JSON.parse(fs.readFileSync(paramsPath, 'utf8')) as Record<string, unknown>
+    climateParams = {}
+    for (const [k, v] of Object.entries(rawParams)) {
+      if (typeof v === 'number') climateParams[k] = v
+    }
+  }
+
+  return {
+    name: 'magic-civ-sim-cache',
+    apply: 'serve', // Dev only
+
+    configureServer(server: ViteDevServer) {
+      server.middlewares.use((req, res, next) => {
+        const url = req.url ?? ''
+        const match = url.match(/^\/__sim-cache\/([^?]+)/)
+        if (!match) { next(); return }
+
+        const scenarioId = match[1]
+        const params = new URL(url, 'http://localhost').searchParams
+        const seed = Number(params.get('seed') ?? '42')
+        const turns = Number(params.get('turns') ?? '2000')
+        const cacheKey = `${scenarioId}:${seed}:${turns}`
+
+        // Return cached result if available
+        const cached = cache.get(cacheKey)
+        if (cached) {
+          res.setHeader('Content-Type', 'application/json')
+          res.end(JSON.stringify({ scenarioId, seed, turns, stats: cached.stats, events: cached.events }))
+          return
+        }
+
+        // Lazy-load engine and data on first request (Vite resolves TS imports for us)
+        const computeAndRespond = async (): Promise<void> => {
+          if (!engineModule) {
+            const enginePath = path.resolve(server.config.root, '../../packages/engine-ts/src/index.ts')
+            engineModule = await server.ssrLoadModule(enginePath) as typeof import('@magic-civ/engine-ts')
+          }
+          if (!terrainData || !climateParams) {
+            loadGameData(server.config.root)
+          }
+
+          const { SCENARIOS, buildTerrainCacheFromData, runScenarioSync } = engineModule
+          const config = SCENARIOS.find(s => s.id === scenarioId)
+          if (!config) {
+            res.statusCode = 404
+            res.end(JSON.stringify({ error: `Unknown scenario: ${scenarioId}` }))
+            return
+          }
+
+          const terrainCache = buildTerrainCacheFromData(terrainData as Record<string, import('@magic-civ/engine-ts').TerrainData>)
+          const result = runScenarioSync(config, terrainCache, climateParams!, turns, seed)
+
+          const stats = result.snapshots.map(s => s.stats)
+          const events = result.snapshots.map(s => s.events)
+
+          cache.set(cacheKey, { stats, events })
+
+          res.setHeader('Content-Type', 'application/json')
+          res.end(JSON.stringify({ scenarioId, seed, turns, stats, events }))
+        }
+
+        computeAndRespond().catch((err: unknown) => {
+          res.statusCode = 500
+          res.end(JSON.stringify({ error: err instanceof Error ? err.message : String(err) }))
+        })
+      })
+    },
+
+    handleHotUpdate({ file }) {
+      // Invalidate cache when engine source or game data changes
+      if (
+        file.includes('/packages/engine-ts/src/') ||
+        file.includes('/games/age-of-dwarves/data/')
+      ) {
+        cache.clear()
+        engineModule = null
+        terrainData = null
+        climateParams = null
+      }
+    },
+  }
+}