diff --git a/README.md b/README.md
index f4675a1..be2ccce 100644
--- a/README.md
+++ b/README.md
@@ -19,9 +19,12 @@ estimated **remaining** balance, for both meal blocks and FLEX.
 - Checkboxes for configured breaks ("missing periods") you spent off campus.
 - A numeric input for any additional days you don't want counted.
 - Live-updating results — every input recomputes the estimate instantly.
-- Everything is config-driven: plans, dates, and breaks live in one JSON file. No code changes
-  needed to adjust them.
+- Everything is config-driven: plans, dates, and breaks live in one JSON file that is fetched at
+  runtime. Edit it on the server and changes appear on the next page load — no rebuild needed.
+- Your plan, checked breaks, and extra-days value are remembered between visits (via
+  `localStorage`). The date always resets to today.
 - Dark theme with restrained CMU Tartan-red accents.
+- Ships as plain static files — no server-side code or backend.
 
 ## Getting started
 
@@ -42,8 +45,11 @@ npm test         # run the estimation-engine tests
 
 ## Configuration
 
-All tunable values live in [`src/config.json`](src/config.json). Edit that file, then reload the
-page — the UI updates reactively.
+All tunable values live in [`public/config.json`](public/config.json). This file is **fetched at
+runtime**, not compiled into the bundle — so after deployment you can edit the deployed
+`config.json` directly and the changes take effect on the next page load, with no rebuild.
+
+During development, edit `public/config.json` and reload the page.
 
 ```jsonc
 {
@@ -96,17 +102,62 @@ Notes:
 Checking a break or adding excluded days shifts your expected consumption down, which is what you
 want when you were away and not eating on campus.
 
+## Deployment (static hosting)
+
+The app is a purely client-side static site — no backend, no server-side rendering. To deploy:
+
+```bash
+npm run build      # outputs everything to dist/
+```
+
+Then copy the **contents of `dist/`** to wherever you're serving from. The build produces:
+
+```
+dist/
+  index.html
+  config.json      # the live, editable config
+  assets/          # hashed JS + CSS
+```
+
+### Subpath hosting
+
+Asset paths in the build are **relative**, and `config.json` is loaded relative to the page's
+own location. That means the app works unchanged whether it's served from a domain root or a
+subpath — e.g. `https://www.cmu.edu/~you/meal-estimator/`. No base-path configuration or rebuild
+is needed to move it between locations.
+
+The one requirement is that the app is served as a directory with a trailing slash (e.g.
+`.../meal-estimator/`). Virtually all static servers (Apache, nginx, and the like) redirect
+`.../meal-estimator` to `.../meal-estimator/` automatically, so this is handled for you.
+
+### Editing config after deployment
+
+Because `config.json` sits alongside `index.html` in the deployed files and is fetched at
+runtime, you can update plan numbers, dates, or breaks by editing the deployed
+`config.json` directly. No rebuild or redeploy of the JS is required — just reload the page.
+
+## Data persistence
+
+The selected plan, checked breaks, and additional-days value are saved to the browser's
+`localStorage` and restored on the next visit. The "as of" date is intentionally **not**
+persisted — it always defaults to today. Persistence fails silently if `localStorage` is
+unavailable (e.g. private browsing), and stale entries (a plan or break no longer in the config)
+are ignored on load.
+
 ## Project structure
 
 ```
 index.html            # app shell
+public/
+  config.json         # all tunable values (plans, dates, breaks); served + fetched at runtime
 src/
-  config.json         # all tunable values (plans, dates, breaks)
   types.ts            # shared types
   dates.ts            # whole-day date helpers
   configLoader.ts     # validates + normalizes config
+  configFetch.ts      # fetches config.json at runtime (subpath-aware)
   engine.ts           # pure estimation math (no DOM)
   store.ts            # tiny reactive state store
+  persistence.ts      # localStorage load/save of selections
   main.ts             # builds the UI, re-renders on change
   style.css           # dark CMU-accented theme
   engine.test.ts      # engine unit tests
diff --git a/package-lock.json b/package-lock.json
index f1c9048..0e6a27d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -8,6 +8,7 @@
       "name": "cmu-meal-estimator",
       "version": "1.0.0",
       "devDependencies": {
+        "@types/node": "^20.19.43",
         "typescript": "^5.6.3",
         "vite": "^5.4.10",
         "vitest": "^2.1.4"
@@ -785,6 +786,16 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/node": {
+      "version": "20.19.43",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-20.19.43.tgz",
+      "integrity": "sha512-6oYBAi5ikg4Pl+kGsoYtawUMBT2zZMCvPNF7pVLnHZfd1zf38DRiWn/gT01RYCdUqkv7Fhr+C9ot4/tb+2sVvA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "undici-types": "~6.21.0"
+      }
+    },
     "node_modules/@vitest/expect": {
       "version": "2.1.9",
       "resolved": "https://registry.npmjs.org/@vitest/expect/-/expect-2.1.9.tgz",
@@ -1285,6 +1296,13 @@
         "node": ">=14.17"
       }
     },
+    "node_modules/undici-types": {
+      "version": "6.21.0",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-6.21.0.tgz",
+      "integrity": "sha512-iwDZqg0QAGrg9Rav5H4n0M64c3mkR59cJ6wQp+7C4nI0gsmExaedaYLNO44eT4AtBBwjbTiGPMlt2Md0T9H9JQ==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/vite": {
       "version": "5.4.21",
       "resolved": "https://registry.npmjs.org/vite/-/vite-5.4.21.tgz",
diff --git a/package.json b/package.json
index 7695240..8cdddbd 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
     "test": "vitest run"
   },
   "devDependencies": {
+    "@types/node": "^20.19.43",
     "typescript": "^5.6.3",
     "vite": "^5.4.10",
     "vitest": "^2.1.4"
diff --git a/src/config.json b/public/config.json
similarity index 79%
rename from src/config.json
rename to public/config.json
index 0a32254..20fe33b 100644
--- a/src/config.json
+++ b/public/config.json
@@ -1,5 +1,5 @@
 {
-  "$comment": "Edit this file to configure the estimator. Dates are ISO YYYY-MM-DD. totalMealBlocks and totalFlexDollars are the amounts for the whole meal period. Add/remove plans and missingPeriods freely; the UI updates reactively. Set exact figures from your CMU dining agreement.",
+  "$comment": "Edit this file to configure the estimator. It is fetched at runtime, so changes take effect on reload without rebuilding. Dates are ISO YYYY-MM-DD. totalMealBlocks and totalFlexDollars are the amounts for the whole meal period. Add/remove plans and missingPeriods freely; the UI updates reactively. Set exact figures from your CMU dining agreement.",
 
   "mealStartDate": "2026-08-24",
   "mealEndDate": "2026-12-13",
diff --git a/src/configFetch.ts b/src/configFetch.ts
new file mode 100644
index 0000000..19f0ca5
--- /dev/null
+++ b/src/configFetch.ts
@@ -0,0 +1,66 @@
+import { loadConfig } from "./configLoader";
+import type { ConfigResult } from "./types";
+
+/**
+ * Fetch and validate config.json at runtime. The URL is resolved against the
+ * app's configured base (import.meta.env.BASE_URL), so it works whether the app
+ * is served from a domain root or a subpath.
+ */
+export async function fetchConfig(): Promise<ConfigResult> {
+  const url = configUrl();
+
+  let response: Response;
+  try {
+    response = await fetch(url.toString(), { cache: "no-cache" });
+  } catch (err) {
+    return {
+      ok: false,
+      errors: [`Could not fetch config.json (${describe(err)}).`],
+    };
+  }
+
+  if (!response.ok) {
+    return {
+      ok: false,
+      errors: [
+        `Could not load config.json (HTTP ${response.status} ${response.statusText}).`,
+      ],
+    };
+  }
+
+  let raw: unknown;
+  try {
+    raw = await response.json();
+  } catch {
+    return {
+      ok: false,
+      errors: ["config.json is not valid JSON."],
+    };
+  }
+
+  return loadConfig(raw);
+}
+
+/**
+ * Resolve the config.json URL for the deployed location. Uses Vite's configured
+ * base when it is an absolute path (e.g. "/meal-estimator/"); otherwise falls
+ * back to the directory of the current document so a relative "./" base works
+ * whether or not the URL has a trailing slash.
+ */
+function configUrl(): string {
+  const base = import.meta.env.BASE_URL;
+
+  if (base.startsWith("/")) {
+    // Absolute base path: config sits directly under it.
+    return new URL(`${base}config.json`, window.location.origin).toString();
+  }
+
+  // Relative base: resolve against the current document's directory.
+  const path = window.location.pathname;
+  const dir = path.endsWith("/") ? path : path.slice(0, path.lastIndexOf("/") + 1);
+  return new URL(`${dir}config.json`, window.location.origin).toString();
+}
+
+function describe(err: unknown): string {
+  return err instanceof Error ? err.message : "network error";
+}
diff --git a/src/main.ts b/src/main.ts
index 172efdd..2b03c24 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,29 +1,57 @@
 import "./style.css";
-import rawConfig from "./config.json";
-import { loadConfig } from "./configLoader";
+import { fetchConfig } from "./configFetch";
 import { estimate } from "./engine";
 import { Store } from "./store";
 import { toISODate, parseISODate, atMidnight } from "./dates";
-import type { Config, EstimationResult } from "./types";
+import { loadPersisted, savePersisted } from "./persistence";
+import type { Config, EstimationResult, Selections } from "./types";
 
 const appEl = document.getElementById("app")!;
 
-const result = loadConfig(rawConfig);
-if (!result.ok) {
-  renderConfigError(result.errors);
-} else {
-  bootstrap(result.config);
+void main();
+
+async function main(): Promise<void> {
+  renderLoading();
+  const result = await fetchConfig();
+  if (!result.ok) {
+    renderConfigError(result.errors);
+  } else {
+    bootstrap(result.config);
+  }
+}
+
+/**
+ * Build the initial selections: defaults, overlaid with any persisted values
+ * that are still valid for this config. The target date is never persisted —
+ * it always starts at today.
+ */
+function initialSelections(config: Config): Selections {
+  const defaults: Selections = {
+    selectedPlanId: config.plans[0].id,
+    targetDate: atMidnight(new Date()),
+    activeMissingPeriodIds: new Set(),
+    extraExcludedDays: 0,
+  };
+
+  const persisted = loadPersisted();
+  if (!persisted) return defaults;
+
+  // Only honor a persisted plan / periods that still exist in the config.
+  const planExists = config.plans.some((p) => p.id === persisted.selectedPlanId);
+  const validPeriodIds = new Set(config.missingPeriods.map((m) => m.id));
+
+  return {
+    ...defaults,
+    selectedPlanId: planExists ? persisted.selectedPlanId : defaults.selectedPlanId,
+    activeMissingPeriodIds: new Set(
+      persisted.activeMissingPeriodIds.filter((id) => validPeriodIds.has(id))
+    ),
+    extraExcludedDays: persisted.extraExcludedDays,
+  };
 }
 
 function bootstrap(config: Config): void {
-  const today = atMidnight(new Date());
-
-  const store = new Store(config, {
-    selectedPlanId: config.plans[0].id,
-    targetDate: today,
-    activeMissingPeriodIds: new Set(),
-    extraExcludedDays: 0,
-  });
+  const store = new Store(config, initialSelections(config));
 
   appEl.innerHTML = "";
   appEl.appendChild(buildLayout(store, config));
@@ -32,7 +60,16 @@ function bootstrap(config: Config): void {
   const daysNote = appEl.querySelector<HTMLElement>("#days-note")!;
 
   const rerender = () => {
-    const r = estimate(config, store.getSelections());
+    const sel = store.getSelections();
+
+    // Persist everything except the date.
+    savePersisted({
+      selectedPlanId: sel.selectedPlanId,
+      activeMissingPeriodIds: [...sel.activeMissingPeriodIds],
+      extraExcludedDays: sel.extraExcludedDays,
+    });
+
+    const r = estimate(config, sel);
     resultsMount.innerHTML = "";
     resultsMount.appendChild(renderResults(r));
     daysNote.textContent = `${fmtDays(r.activeDaysConsumed)} of ${fmtDays(
@@ -124,6 +161,7 @@ function buildControls(store: Store, config: Config): HTMLElement {
       const cb = document.createElement("input");
       cb.type = "checkbox";
       cb.value = period.id;
+      cb.checked = store.getSelections().activeMissingPeriodIds.has(period.id);
       cb.addEventListener("change", () =>
         store.setMissingPeriodActive(period.id, cb.checked)
       );
@@ -150,7 +188,7 @@ function buildControls(store: Store, config: Config): HTMLElement {
   extra.type = "number";
   extra.min = "0";
   extra.step = "1";
-  extra.value = "0";
+  extra.value = String(store.getSelections().extraExcludedDays);
   extra.className = "input";
   extra.id = "extra-days";
   extra.addEventListener("input", () =>
@@ -214,7 +252,14 @@ function metric(value: string, unit: string): HTMLElement {
   return m;
 }
 
-/* ---------- config error ---------- */
+/* ---------- loading + config error ---------- */
+
+function renderLoading(): void {
+  const box = el("div", "loading");
+  box.textContent = "Loading…";
+  appEl.innerHTML = "";
+  appEl.appendChild(box);
+}
 
 function renderConfigError(errors: string[]): void {
   const box = el("div", "config-error");
diff --git a/src/persistence.ts b/src/persistence.ts
new file mode 100644
index 0000000..7e42513
--- /dev/null
+++ b/src/persistence.ts
@@ -0,0 +1,56 @@
+/**
+ * Persists the user's selections across visits via localStorage.
+ * Deliberately excludes the target date — that always defaults to today unless
+ * the user changes it during a session.
+ */
+
+const STORAGE_KEY = "cmu-meal-estimator:selections:v1";
+
+export interface PersistedSelections {
+  selectedPlanId: string;
+  activeMissingPeriodIds: string[];
+  extraExcludedDays: number;
+}
+
+/** Load persisted selections, or null if none/invalid/unavailable. */
+export function loadPersisted(): PersistedSelections | null {
+  let raw: string | null;
+  try {
+    raw = localStorage.getItem(STORAGE_KEY);
+  } catch {
+    // localStorage can throw (private mode, disabled). Fail soft.
+    return null;
+  }
+  if (!raw) return null;
+
+  try {
+    const parsed = JSON.parse(raw) as unknown;
+    if (typeof parsed !== "object" || parsed === null) return null;
+    const o = parsed as Record<string, unknown>;
+
+    const selectedPlanId = typeof o.selectedPlanId === "string" ? o.selectedPlanId : null;
+    const idsRaw = Array.isArray(o.activeMissingPeriodIds) ? o.activeMissingPeriodIds : [];
+    const activeMissingPeriodIds = idsRaw.filter(
+      (x): x is string => typeof x === "string"
+    );
+    const extraExcludedDays =
+      typeof o.extraExcludedDays === "number" && Number.isFinite(o.extraExcludedDays)
+        ? Math.max(0, Math.floor(o.extraExcludedDays))
+        : 0;
+
+    if (selectedPlanId === null) return null;
+
+    return { selectedPlanId, activeMissingPeriodIds, extraExcludedDays };
+  } catch {
+    return null;
+  }
+}
+
+/** Persist the given selections. Fails soft if storage is unavailable. */
+export function savePersisted(sel: PersistedSelections): void {
+  try {
+    localStorage.setItem(STORAGE_KEY, JSON.stringify(sel));
+  } catch {
+    // Ignore — persistence is a convenience, not a requirement.
+  }
+}
diff --git a/src/sanity.test.ts b/src/sanity.test.ts
index 1c6b300..65d1860 100644
--- a/src/sanity.test.ts
+++ b/src/sanity.test.ts
@@ -1,9 +1,14 @@
 import { describe, it, expect } from "vitest";
-import rawConfig from "./config.json";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
 import { loadConfig } from "./configLoader";
 import { estimate } from "./engine";
 import { parseISODate } from "./dates";
 
+// Read the actual shipped config that gets served at runtime.
+const configPath = fileURLToPath(new URL("../public/config.json", import.meta.url));
+const rawConfig = JSON.parse(readFileSync(configPath, "utf-8"));
+
 describe("real config sanity", () => {
   const result = loadConfig(rawConfig);
 
diff --git a/src/style.css b/src/style.css
index 09ae077..9bab462 100644
--- a/src/style.css
+++ b/src/style.css
@@ -299,3 +299,13 @@ body {
 .config-error li {
   margin-bottom: 6px;
 }
+
+/* Loading */
+.loading {
+  max-width: 640px;
+  margin: 96px auto;
+  text-align: center;
+  color: var(--text-dim);
+  font-family: "IBM Plex Mono", ui-monospace, monospace;
+  font-size: 15px;
+}
diff --git a/src/vite-env.d.ts b/src/vite-env.d.ts
new file mode 100644
index 0000000..11f02fe
--- /dev/null
+++ b/src/vite-env.d.ts
@@ -0,0 +1 @@
+/// <reference types="vite/client" />
diff --git a/tsconfig.json b/tsconfig.json
index 50e85ed..9be21e6 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -9,6 +9,7 @@
     "allowImportingTsExtensions": true,
     "resolveJsonModule": true,
     "isolatedModules": true,
+    "types": ["vite/client", "node"],
     "noEmit": true,
     "strict": true,
     "noUnusedLocals": true,