diff --git a/CLAUDE.md b/CLAUDE.md
index 38f2c0a..14ad93d 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -19,6 +19,7 @@ Svelte 5 + TypeScript + Vite. Public repository.
 | Base UI kit (panel, meter, button...), preview | `src/components/ui/`, `#/kit` in dev (dec. 009)   |
 | Resync values; business bars (Sold, Raided)    | `ui/EditableValue`, `ui/BusinessBars` (dec. 010)  |
 | Game data with sources                         | `src/data/` (decision 004)                        |
+| Owned properties and upgrades                  | `data/properties.ts`, `lib/properties.ts` (011)   |
 | Theme tokens                                   | `src/app.css` (decision 009)                      |
 | CI, templates                                  | `.github/`                                        |
 | Skills: `handoff`, `finish-pr`; agent: `scout` | `.claude/`                                        |
diff --git a/docs/decisions/011-owned-properties.md b/docs/decisions/011-owned-properties.md
new file mode 100644
index 0000000..6395eba
--- /dev/null
+++ b/docs/decisions/011-owned-properties.md
@@ -0,0 +1,28 @@
+# 011: Owned properties and upgrades
+
+2026-10-14, issue #5. Builds on decisions 004 and 006.
+
+## Decision
+
+- **Catalog:** `src/data/properties.ts` lists the properties LSOS supports, each with a stable
+  `id` (saved in user data, never changed or reused), a label, its upgrades and a source. It
+  starts empty: each tracker issue adds its own property with sourced upgrades.
+- **Two kinds of upgrade:** `toggle` (bought or not, e.g. an equipment or staff upgrade) and
+  `choice` (one of several options, the first being the default, e.g. what a nightclub
+  technician is assigned to, with "not hired" first). Several technicians are several choices.
+- **Saved state** (version 3): `properties` maps a property id to `{ owned, upgrades }`, where an
+  upgrade is saved as `true`/`false` or the chosen option id. A missing entry means not owned,
+  no upgrades. Unchecking "owned" keeps the upgrades, so owning it again restores them. Entries
+  for ids the catalog does not list are kept; a saved value that no longer fits its upgrade
+  reads as the default. Logic: `src/lib/properties.ts`.
+- **UI:** Settings has a Properties panel with every catalog entry (owned checkbox; upgrades
+  appear once owned). The Businesses tab shows only owned properties, each panel with a gear
+  button that opens the same settings in place; closed, it summarises the bought upgrades.
+  Both components take the catalog as a prop, so `#/kit` previews them with sample entries.
+
+## Why
+
+Production rates depend on ownership and upgrades, so trackers need them, and users must be
+able to change them where they look at a business as well as in Settings. Two kinds cover every
+upgrade named in the issue without a separate shape per business. Keeping upgrades on sale and
+unknown ids on load avoids throwing away user input over a misclick or a catalog change.
diff --git a/docs/decisions/README.md b/docs/decisions/README.md
index 8a0c1c8..32df460 100644
--- a/docs/decisions/README.md
+++ b/docs/decisions/README.md
@@ -21,3 +21,4 @@ free number, add one line below. **Replacing one:** write a new decision, then m
 - [008](008-clock-details.md) Clock details: session play time, opens paused (setting), throttled ticks counted, long gaps asked about
 - [009](009-terminal-design.md) Terminal look: tokens in `app.css`, self-hosted Oswald (OFL), browser-style tabs, base components in `src/components/ui/`
 - [010](010-resync.md) Resync: `EditableValue` for every tracked value, `BusinessBars` with Sold/Raided/Full and supply deliveries, undo keeps progress since
+- [011](011-owned-properties.md) Owned properties and upgrades: catalog in `src/data/properties.ts`, toggle/choice upgrades, Settings panel and Businesses gear
diff --git a/src/App.svelte b/src/App.svelte
index f74ce17..205d2fb 100644
--- a/src/App.svelte
+++ b/src/App.svelte
@@ -1,9 +1,12 @@
 <script lang="ts">
   import Boot from './components/Boot.svelte'
+  import Businesses from './components/Businesses.svelte'
   import ClockBar from './components/ClockBar.svelte'
   import SaveStatus from './components/SaveStatus.svelte'
   import Settings from './components/Settings.svelte'
   import TabBar from './components/ui/TabBar.svelte'
+  import { PROPERTIES } from './data/properties'
+  import { store } from './lib/store.svelte'
   import { TABS, tabFromHash } from './lib/tabs'
 
   let hash = $state(location.hash)
@@ -37,6 +40,12 @@
         {#await kitModule then { default: Kit }}
           <Kit />
         {/await}
+      {:else if active === 'businesses'}
+        <Businesses
+          catalog={PROPERTIES}
+          owned={store.state.properties}
+          onchange={(owned) => (store.state.properties = owned)}
+        />
       {:else if active === 'settings'}
         <Settings />
       {:else}
diff --git a/src/components/Businesses.svelte b/src/components/Businesses.svelte
new file mode 100644
index 0000000..ffae7d0
--- /dev/null
+++ b/src/components/Businesses.svelte
@@ -0,0 +1,97 @@
+<script lang="ts">
+  // The owned businesses, each with a gear to change what is owned and upgraded (decision 011).
+  import type { Property } from '../data/properties'
+  import { ownedProperties, upgradeValue, type OwnedProperties } from '../lib/properties'
+  import { hashForTab } from '../lib/tabs'
+  import PropertySettings from './PropertySettings.svelte'
+  import Button from './ui/Button.svelte'
+  import Panel from './ui/Panel.svelte'
+
+  interface Props {
+    catalog: readonly Property[]
+    owned: OwnedProperties
+    onchange: (owned: OwnedProperties) => void
+  }
+
+  let { catalog, owned, onchange }: Props = $props()
+  const shown = $derived(ownedProperties(catalog, owned))
+  let open = $state<string | null>(null)
+
+  /** Short summary of the bought upgrades, e.g. "Equipment, Technician: Cash". */
+  function summary(property: Property): string {
+    const parts = property.upgrades.flatMap((upgrade) => {
+      const value = upgradeValue(owned, property.id, upgrade)
+      if (upgrade.kind === 'toggle') return value === true ? [upgrade.label] : []
+      if (value === upgrade.options[0]?.id) return []
+      const option = upgrade.options.find((o) => o.id === value)
+      return option ? [`${upgrade.label}: ${option.label}`] : []
+    })
+    return parts.length > 0 ? parts.join(', ') : 'No upgrades'
+  }
+</script>
+
+{#if shown.length === 0}
+  <p class="empty">
+    {#if catalog.length === 0}
+      No businesses are tracked yet.
+    {:else}
+      You do not own any business yet. Mark what you own in
+      <a href={hashForTab('settings')}>Settings</a>.
+    {/if}
+  </p>
+{:else}
+  <div class="grid">
+    {#each shown as property (property.id)}
+      <Panel title={property.label}>
+        {#if open === property.id}
+          <PropertySettings {property} {owned} {onchange} />
+        {:else}
+          <p class="hint">{summary(property)}</p>
+        {/if}
+        {#snippet footer()}
+          <Button
+            aria-label="Settings for {property.label}"
+            aria-expanded={open === property.id}
+            onclick={() => (open = open === property.id ? null : property.id)}
+          >
+            <svg viewBox="0 0 24 24" width="16" height="16" aria-hidden="true">
+              <path
+                fill="currentColor"
+                d="M19.14 12.94a7.07 7.07 0 0 0 0-1.88l2.03-1.58a.5.5 0 0 0 .12-.64l-1.92-3.32a.5.5 0 0 0-.6-.22l-2.39.96a7 7 0 0 0-1.62-.94l-.36-2.54a.5.5 0 0 0-.5-.42h-3.84a.5.5 0 0 0-.5.42l-.36 2.54a7 7 0 0 0-1.62.94l-2.39-.96a.5.5 0 0 0-.6.22L2.71 8.84a.5.5 0 0 0 .12.64l2.03 1.58a7.07 7.07 0 0 0 0 1.88l-2.03 1.58a.5.5 0 0 0-.12.64l1.92 3.32a.5.5 0 0 0 .6.22l2.39-.96a7 7 0 0 0 1.62.94l.36 2.54a.5.5 0 0 0 .5.42h3.84a.5.5 0 0 0 .5-.42l.36-2.54a7 7 0 0 0 1.62-.94l2.39.96a.5.5 0 0 0 .6-.22l1.92-3.32a.5.5 0 0 0-.12-.64zM12 15.5A3.5 3.5 0 1 1 12 8.5a3.5 3.5 0 0 1 0 7z"
+              />
+            </svg>
+          </Button>
+        {/snippet}
+      </Panel>
+    {/each}
+  </div>
+{/if}
+
+<style>
+  .grid {
+    display: grid;
+    gap: var(--space-5);
+    grid-template-columns: repeat(auto-fill, minmax(min(100%, 24rem), 1fr));
+  }
+
+  p {
+    margin: 0;
+  }
+
+  .empty {
+    color: var(--muted);
+  }
+
+  .empty a {
+    color: var(--accent-text);
+  }
+
+  .hint {
+    color: var(--muted);
+    font-size: var(--text-sm);
+  }
+
+  svg {
+    display: block;
+  }
+</style>
diff --git a/src/components/PropertyList.svelte b/src/components/PropertyList.svelte
new file mode 100644
index 0000000..2f00589
--- /dev/null
+++ b/src/components/PropertyList.svelte
@@ -0,0 +1,35 @@
+<script lang="ts">
+  // Every property LSOS supports, to mark what the user owns (decision 011).
+  import type { Property } from '../data/properties'
+  import type { OwnedProperties } from '../lib/properties'
+  import PropertySettings from './PropertySettings.svelte'
+  import Panel from './ui/Panel.svelte'
+
+  interface Props {
+    catalog: readonly Property[]
+    owned: OwnedProperties
+    onchange: (owned: OwnedProperties) => void
+  }
+
+  let { catalog, owned, onchange }: Props = $props()
+</script>
+
+<Panel title="Properties">
+  {#each catalog as property (property.id)}
+    <PropertySettings {property} {owned} {onchange} />
+  {:else}
+    <p>No properties yet. They appear here as their trackers are built.</p>
+  {/each}
+  <p class="hint">Trackers show only what you own. Upgrades change how fast they count.</p>
+</Panel>
+
+<style>
+  p {
+    margin: 0;
+  }
+
+  .hint {
+    color: var(--muted);
+    font-size: var(--text-sm);
+  }
+</style>
diff --git a/src/components/PropertySettings.svelte b/src/components/PropertySettings.svelte
new file mode 100644
index 0000000..249015a
--- /dev/null
+++ b/src/components/PropertySettings.svelte
@@ -0,0 +1,122 @@
+<script lang="ts">
+  // Owned yes/no and the upgrades of one property (decision 011).
+  import type { Property } from '../data/properties'
+  import {
+    isOwned,
+    setOwned,
+    setUpgrade,
+    upgradeValue,
+    type OwnedProperties,
+  } from '../lib/properties'
+
+  interface Props {
+    property: Property
+    owned: OwnedProperties
+    onchange: (owned: OwnedProperties) => void
+  }
+
+  let { property, owned, onchange }: Props = $props()
+  const id = $props.id()
+</script>
+
+<div class="property">
+  <label class="owned">
+    <input
+      type="checkbox"
+      checked={isOwned(owned, property.id)}
+      onchange={(event) => onchange(setOwned(owned, property.id, event.currentTarget.checked))}
+    />
+    <span>Own {property.label}</span>
+  </label>
+
+  {#if isOwned(owned, property.id) && property.upgrades.length > 0}
+    <div class="upgrades">
+      {#each property.upgrades as upgrade (upgrade.id)}
+        {#if upgrade.kind === 'toggle'}
+          <label>
+            <input
+              type="checkbox"
+              checked={upgradeValue(owned, property.id, upgrade) === true}
+              onchange={(event) =>
+                onchange(setUpgrade(owned, property.id, upgrade.id, event.currentTarget.checked))}
+            />
+            {upgrade.label}
+          </label>
+        {:else}
+          <div class="choice">
+            <label for="{id}-{upgrade.id}">{upgrade.label}</label>
+            <select
+              id="{id}-{upgrade.id}"
+              value={upgradeValue(owned, property.id, upgrade)}
+              onchange={(event) =>
+                onchange(setUpgrade(owned, property.id, upgrade.id, event.currentTarget.value))}
+            >
+              {#each upgrade.options as option (option.id)}
+                <option value={option.id}>{option.label}</option>
+              {/each}
+            </select>
+          </div>
+        {/if}
+      {/each}
+    </div>
+  {/if}
+</div>
+
+<style>
+  .property {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-2);
+  }
+
+  label {
+    align-items: center;
+    cursor: pointer;
+    display: flex;
+    gap: var(--space-2);
+  }
+
+  .owned {
+    font-family: var(--font-display);
+    letter-spacing: var(--tracking);
+    text-transform: uppercase;
+  }
+
+  .upgrades {
+    border-left: 2px solid var(--line);
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-2);
+    margin-left: 0.5rem;
+    padding-left: var(--space-3);
+  }
+
+  .choice {
+    align-items: center;
+    display: flex;
+    flex-wrap: wrap;
+    gap: var(--space-2);
+    justify-content: space-between;
+  }
+
+  input[type='checkbox'] {
+    accent-color: var(--accent);
+    flex: none;
+    height: 1.125rem;
+    width: 1.125rem;
+  }
+
+  select {
+    background: var(--panel-raised);
+    border: 1px solid var(--line);
+    border-radius: var(--radius);
+    color: var(--fg);
+    font: inherit;
+    min-height: 2.25rem;
+    padding: var(--space-1) var(--space-2);
+  }
+
+  select:hover {
+    border-color: var(--accent);
+  }
+</style>
diff --git a/src/components/Settings.svelte b/src/components/Settings.svelte
index 15e667e..48feea3 100644
--- a/src/components/Settings.svelte
+++ b/src/components/Settings.svelte
@@ -1,6 +1,8 @@
 <script lang="ts">
+  import { PROPERTIES } from '../data/properties'
   import { exportFileName } from '../lib/state'
   import { exportText, importText, store } from '../lib/store.svelte'
+  import PropertyList from './PropertyList.svelte'
   import Button from './ui/Button.svelte'
   import Panel from './ui/Panel.svelte'
 
@@ -36,6 +38,12 @@
 </script>
 
 <div class="grid">
+  <PropertyList
+    catalog={PROPERTIES}
+    owned={store.state.properties}
+    onchange={(owned) => (store.state.properties = owned)}
+  />
+
   <Panel title="Clock">
     <label>
       <input type="checkbox" bind:checked={store.state.clock.trackOnOpen} />
diff --git a/src/components/ui/Kit.svelte b/src/components/ui/Kit.svelte
index 4654a17..cb380c9 100644
--- a/src/components/ui/Kit.svelte
+++ b/src/components/ui/Kit.svelte
@@ -1,7 +1,11 @@
 <script lang="ts">
   // Dev-only preview of the base components (open #/kit with `npm run dev`).
   // Sample numbers only: no game values here (decision 004).
+  import type { Property } from '../../data/properties'
+  import type { OwnedProperties } from '../../lib/properties'
   import type { Bars } from '../../lib/resync'
+  import Businesses from '../Businesses.svelte'
+  import PropertyList from '../PropertyList.svelte'
   import BusinessBars from './BusinessBars.svelte'
   import Button from './Button.svelte'
   import Countdown from './Countdown.svelte'
@@ -15,6 +19,31 @@
   let bars = $state<Bars>({ stock: 60, supplies: 35 })
   let stockOnly = $state<Bars>({ stock: 45 })
 
+  // Sample properties for the Settings list and the Businesses tab; made up, not game data.
+  const sampleCatalog: Property[] = [
+    {
+      id: 'sample-a',
+      label: 'Sample business',
+      upgrades: [
+        { kind: 'toggle', id: 'equipment', label: 'Equipment upgrade' },
+        {
+          kind: 'choice',
+          id: 'worker',
+          label: 'Worker',
+          options: [
+            { id: 'none', label: 'Not hired' },
+            { id: 'a', label: 'Option A' },
+            { id: 'b', label: 'Option B' },
+          ],
+        },
+      ],
+      source: 'sample',
+      checked: '2026-10-14',
+    },
+    { id: 'sample-b', label: 'No upgrades', upgrades: [], source: 'sample', checked: '2026-10-14' },
+  ]
+  let owned = $state<OwnedProperties>({ 'sample-a': { owned: true, upgrades: {} } })
+
   // A real-time cooldown, as a tracker would keep it: the moment it is ready.
   let now = $state(Date.now())
   let readyAt = $state(Date.now() + 90 * 60_000)
@@ -80,12 +109,22 @@
       }}
     />
   </Panel>
+
+  <PropertyList catalog={sampleCatalog} {owned} onchange={(value) => (owned = value)} />
 </div>
 
+<h2>Businesses tab</h2>
+<Businesses catalog={sampleCatalog} {owned} onchange={(value) => (owned = value)} />
+
 <style>
   .grid {
     display: grid;
     gap: var(--space-5);
     grid-template-columns: repeat(auto-fill, minmax(min(100%, 20rem), 1fr));
   }
+
+  h2 {
+    font-size: var(--text-lg);
+    margin: var(--space-6) 0 var(--space-4);
+  }
 </style>
diff --git a/src/data/properties.ts b/src/data/properties.ts
new file mode 100644
index 0000000..09beaa6
--- /dev/null
+++ b/src/data/properties.ts
@@ -0,0 +1,25 @@
+// Properties LSOS supports and the upgrades that change their trackers (decision 004, 011).
+// Each tracker issue adds its property here, with a source for every upgrade it lists.
+
+/** One option of a choice upgrade, e.g. what a nightclub technician is assigned to. */
+export interface UpgradeOption {
+  id: string
+  label: string
+}
+
+export type Upgrade =
+  /** Bought or not, e.g. an equipment upgrade. */
+  | { kind: 'toggle'; id: string; label: string }
+  /** One of several options; the first one is the default, e.g. "Not hired". */
+  | { kind: 'choice'; id: string; label: string; options: readonly UpgradeOption[] }
+
+export interface Property {
+  /** Stable id, saved in user data: never change or reuse it. */
+  id: string
+  label: string
+  upgrades: readonly Upgrade[]
+  source: string
+  checked: string
+}
+
+export const PROPERTIES: readonly Property[] = []
diff --git a/src/lib/properties.test.ts b/src/lib/properties.test.ts
new file mode 100644
index 0000000..5aebb14
--- /dev/null
+++ b/src/lib/properties.test.ts
@@ -0,0 +1,104 @@
+import { describe, expect, it } from 'vitest'
+import type { Property, Upgrade } from '../data/properties'
+import {
+  isOwned,
+  ownedProperties,
+  parseOwnedProperties,
+  setOwned,
+  setUpgrade,
+  upgradeValue,
+  type OwnedProperties,
+} from './properties'
+
+// Sample catalog: shapes only, no game data (decision 004).
+const toggle: Upgrade = { kind: 'toggle', id: 'equipment', label: 'Equipment' }
+const choice: Upgrade = {
+  kind: 'choice',
+  id: 'tech',
+  label: 'Technician',
+  options: [
+    { id: 'none', label: 'Not hired' },
+    { id: 'cash', label: 'Cash' },
+  ],
+}
+const sample = (id: string): Property => ({
+  id,
+  label: id,
+  upgrades: [toggle, choice],
+  source: 'test',
+  checked: '2026-10-14',
+})
+const catalog = [sample('a'), sample('b'), sample('c')]
+
+describe('owning', () => {
+  it('owns nothing by default', () => {
+    expect(isOwned({}, 'a')).toBe(false)
+    expect(ownedProperties(catalog, {})).toEqual([])
+  })
+
+  it('lists owned properties in catalog order', () => {
+    const owned = setOwned(setOwned(setOwned({}, 'c', true), 'a', true), 'b', false)
+    expect(ownedProperties(catalog, owned).map((p) => p.id)).toEqual(['a', 'c'])
+  })
+
+  it('keeps upgrades when a property is sold and bought again', () => {
+    let owned = setUpgrade(setOwned({}, 'a', true), 'a', 'equipment', true)
+    owned = setOwned(owned, 'a', false)
+    expect(isOwned(owned, 'a')).toBe(false)
+    owned = setOwned(owned, 'a', true)
+    expect(upgradeValue(owned, 'a', toggle)).toBe(true)
+  })
+
+  it('does not mutate its input', () => {
+    const owned: OwnedProperties = { a: { owned: false, upgrades: {} } }
+    setOwned(owned, 'a', true)
+    setUpgrade(owned, 'a', 'equipment', true)
+    expect(owned).toEqual({ a: { owned: false, upgrades: {} } })
+  })
+})
+
+describe('upgradeValue', () => {
+  it('defaults to not bought and the first option', () => {
+    expect(upgradeValue({}, 'a', toggle)).toBe(false)
+    expect(upgradeValue({}, 'a', choice)).toBe('none')
+  })
+
+  it('reads saved values', () => {
+    const owned = setUpgrade(setUpgrade({}, 'a', 'equipment', true), 'a', 'tech', 'cash')
+    expect(upgradeValue(owned, 'a', toggle)).toBe(true)
+    expect(upgradeValue(owned, 'a', choice)).toBe('cash')
+    expect(upgradeValue(owned, 'b', choice)).toBe('none')
+  })
+
+  it('falls back to the default for values that do not fit', () => {
+    const owned = { a: { owned: true, upgrades: { equipment: 'yes', tech: 'gone' } } }
+    expect(upgradeValue(owned, 'a', toggle)).toBe(false)
+    expect(upgradeValue(owned, 'a', choice)).toBe('none')
+  })
+})
+
+describe('parseOwnedProperties', () => {
+  it('keeps every entry, listed or not', () => {
+    const data = {
+      a: { owned: true, upgrades: { tech: 'cash' } },
+      old: { owned: false, upgrades: {} },
+    }
+    expect(parseOwnedProperties(data)).toEqual(data)
+  })
+
+  it('drops unknown fields', () => {
+    expect(parseOwnedProperties({ a: { owned: true, upgrades: {}, x: 1 } })).toEqual({
+      a: { owned: true, upgrades: {} },
+    })
+  })
+
+  it.each([
+    ['a missing section', undefined, 'properties section is missing'],
+    ['an array', [], 'properties section is missing'],
+    ['a bad owned flag', { a: { owned: 'yes', upgrades: {} } }, 'property "a"'],
+    ['missing upgrades', { a: { owned: true } }, 'property "a"'],
+    ['a bad upgrade', { a: { owned: true, upgrades: { tech: 3 } } }, 'upgrade "tech"'],
+  ])('rejects %s', (_, data, message) => {
+    expect(parseOwnedProperties(data)).toContain(message)
+  })
+})
diff --git a/src/lib/properties.ts b/src/lib/properties.ts
new file mode 100644
index 0000000..8640316
--- /dev/null
+++ b/src/lib/properties.ts
@@ -0,0 +1,91 @@
+// Which properties the user owns and which upgrades they bought (decision 011).
+import type { Property, Upgrade } from '../data/properties'
+
+/** A toggle upgrade is saved as true/false, a choice upgrade as the chosen option's id. */
+export type UpgradeValue = boolean | string
+
+export interface PropertySettings {
+  owned: boolean
+  upgrades: Record<string, UpgradeValue>
+}
+
+/** Settings by property id. A property without an entry is not owned and has no upgrades. */
+export type OwnedProperties = Record<string, PropertySettings>
+
+export function isOwned(owned: OwnedProperties, propertyId: string): boolean {
+  return owned[propertyId]?.owned ?? false
+}
+
+/** The properties of `catalog` the user owns, in catalog order. */
+export function ownedProperties(
+  catalog: readonly Property[],
+  owned: OwnedProperties,
+): readonly Property[] {
+  return catalog.filter((property) => isOwned(owned, property.id))
+}
+
+/**
+ * The saved value of an upgrade, or its default: not bought, or the first option. A saved value
+ * that does not fit the upgrade (an option that no longer exists) also reads as the default.
+ */
+export function upgradeValue(
+  owned: OwnedProperties,
+  propertyId: string,
+  upgrade: Upgrade,
+): UpgradeValue {
+  const saved = owned[propertyId]?.upgrades[upgrade.id]
+  if (upgrade.kind === 'toggle') return saved === true
+  return upgrade.options.some((option) => option.id === saved)
+    ? (saved as string)
+    : (upgrade.options[0]?.id ?? '')
+}
+
+/** Marks a property owned or not. Upgrades are kept, so owning it again restores them. */
+export function setOwned(
+  owned: OwnedProperties,
+  propertyId: string,
+  value: boolean,
+): OwnedProperties {
+  return { ...owned, [propertyId]: { upgrades: {}, ...owned[propertyId], owned: value } }
+}
+
+export function setUpgrade(
+  owned: OwnedProperties,
+  propertyId: string,
+  upgradeId: string,
+  value: UpgradeValue,
+): OwnedProperties {
+  const current = owned[propertyId] ?? { owned: false, upgrades: {} }
+  return {
+    ...owned,
+    [propertyId]: { ...current, upgrades: { ...current.upgrades, [upgradeId]: value } },
+  }
+}
+
+/**
+ * Checks saved settings. Entries are kept even for properties this LSOS does not list, so an
+ * import into an older copy of LSOS loses nothing.
+ * Returns an error message if the shape is wrong.
+ */
+export function parseOwnedProperties(data: unknown): OwnedProperties | string {
+  if (!isRecord(data)) return 'The properties section is missing.'
+  const result: OwnedProperties = {}
+  for (const [id, entry] of Object.entries(data)) {
+    if (!isRecord(entry) || typeof entry.owned !== 'boolean' || !isRecord(entry.upgrades)) {
+      return `The saved settings for property "${id}" are not readable.`
+    }
+    const upgrades: Record<string, UpgradeValue> = {}
+    for (const [upgradeId, value] of Object.entries(entry.upgrades)) {
+      if (typeof value !== 'boolean' && typeof value !== 'string') {
+        return `The saved upgrade "${upgradeId}" of property "${id}" is not readable.`
+      }
+      upgrades[upgradeId] = value
+    }
+    result[id] = { owned: entry.owned, upgrades }
+  }
+  return result
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === 'object' && value !== null && !Array.isArray(value)
+}
diff --git a/src/lib/state.test.ts b/src/lib/state.test.ts
index 8e0eef2..225d200 100644
--- a/src/lib/state.test.ts
+++ b/src/lib/state.test.ts
@@ -25,21 +25,42 @@ describe('parseState', () => {
     expect(result).toEqual({
       ok: true,
       state: {
-        version: 2,
+        version: 3,
         clock: { trackOnOpen: false },
+        properties: {},
       },
       fromVersion: 1,
     })
   })
 
+  it('migrates a version 2 sample, owning nothing', () => {
+    const result = parseState('{"version":2,"clock":{"trackOnOpen":true}}')
+    expect(result).toEqual({
+      ok: true,
+      state: { version: 3, clock: { trackOnOpen: true }, properties: {} },
+      fromVersion: 2,
+    })
+  })
+
   it('keeps the saved clock setting', () => {
-    const text = '{"version":2,"clock":{"trackOnOpen":true,"playMs":5}}'
+    const text = '{"version":3,"clock":{"trackOnOpen":true,"playMs":5},"properties":{}}'
     expect(parseState(text)).toMatchObject({ ok: true, state: { clock: { trackOnOpen: true } } })
   })
 
+  it('keeps saved properties', () => {
+    const properties = { lab: { owned: true, upgrades: { equipment: true, tech: 'cash' } } }
+    const text = JSON.stringify({ ...defaultState(), properties })
+    expect(parseState(text)).toMatchObject({ ok: true, state: { properties } })
+  })
+
   it.each([
-    ['a missing clock', '{"version":2}', 'clock section is missing'],
-    ['a bad tracking setting', '{"version":2,"clock":{"trackOnOpen":"yes"}}', 'tracking setting'],
+    ['a missing clock', '{"version":3,"properties":{}}', 'clock section is missing'],
+    [
+      'a bad tracking setting',
+      '{"version":3,"clock":{"trackOnOpen":"yes"},"properties":{}}',
+      'tracking setting',
+    ],
+    ['missing properties', '{"version":3,"clock":{"trackOnOpen":false}}', 'properties section'],
   ])('rejects %s', (_, text, message) => {
     const result = parseState(text)
     expect(result).toMatchObject({ ok: false, reason: 'invalid' })
diff --git a/src/lib/state.ts b/src/lib/state.ts
index 5f25bf4..b48f9b1 100644
--- a/src/lib/state.ts
+++ b/src/lib/state.ts
@@ -1,18 +1,21 @@
 // The persisted root state, its versions and migrations (decision 006).
 import { defaultClockSettings, type ClockSettings } from './clock'
+import { parseOwnedProperties, type OwnedProperties } from './properties'
 
 /** Bump when the stored shape changes, and add a migration from the previous version. */
-export const CURRENT_VERSION = 2
+export const CURRENT_VERSION = 3
 
 /** All user state. Trackers add their own sections here as they are built. */
 export interface AppState {
   version: typeof CURRENT_VERSION
   /** Clock settings (decision 008). Play time itself lasts one session and is not saved. */
   clock: ClockSettings
+  /** Owned properties and their upgrades (decision 011). */
+  properties: OwnedProperties
 }
 
 export function defaultState(): AppState {
-  return { version: CURRENT_VERSION, clock: defaultClockSettings() }
+  return { version: CURRENT_VERSION, clock: defaultClockSettings(), properties: {} }
 }
 
 export type StoredData = Record<string, unknown> & { version: number }
@@ -24,6 +27,8 @@ export type Migration = (data: StoredData) => Record<string, unknown>
 export const MIGRATIONS: Readonly<Record<number, Migration>> = {
   // Version 2 adds the clock (issue #2).
   1: (data) => ({ ...data, clock: defaultClockSettings() }),
+  // Version 3 adds owned properties and upgrades (issue #5); nothing is owned yet.
+  2: (data) => ({ ...data, properties: {} }),
 }
 
 export type ParseResult =
@@ -94,7 +99,9 @@ function toState(data: StoredData): AppState | string {
   if (data.version !== CURRENT_VERSION) return `Unexpected data version ${data.version}.`
   const clock = toClock(data.clock)
   if (typeof clock === 'string') return clock
-  return { version: CURRENT_VERSION, clock }
+  const properties = parseOwnedProperties(data.properties)
+  if (typeof properties === 'string') return properties
+  return { version: CURRENT_VERSION, clock, properties }
 }
 
 function toClock(data: unknown): ClockSettings | string {