diff --git a/api/main.py b/api/main.py
index 05aef6e..b6f9993 100644
--- a/api/main.py
+++ b/api/main.py
@@ -24,7 +24,7 @@ from circuitforge_core.affiliates import wrap_url as _wrap_affiliate_url
 from circuitforge_core.api import make_corrections_router as _make_corrections_router
 from circuitforge_core.api import make_feedback_router as _make_feedback_router
 from circuitforge_core.config import load_env
-from fastapi import Depends, FastAPI, File, HTTPException, Request, Response, UploadFile
+from fastapi import Depends, FastAPI, File, HTTPException, Query, Request, Response, UploadFile
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import StreamingResponse
 from pydantic import BaseModel
@@ -34,7 +34,7 @@ from api.ebay_webhook import router as ebay_webhook_router
 from app.db.models import SavedSearch as SavedSearchModel
 from app.db.models import ScammerEntry
 from app.db.store import Store
-from app.platforms import SearchFilters
+from app.platforms import SUPPORTED_PLATFORMS, SearchFilters
 from app.platforms.ebay.adapter import EbayAdapter
 from app.platforms.ebay.auth import EbayTokenManager
 from app.platforms.ebay.query_builder import expand_queries, parse_groups
@@ -674,6 +674,11 @@ def _make_adapter(shared_store: Store, force: str = "auto"):
 
     Adapters receive shared_store because they only read/write sellers and
     market_comps — never listings. Listings are returned and saved by the caller.
+
+    # Platform registry — add new adapters here as platforms are implemented.
+    # _make_adapter() currently handles eBay only. Phase 2 will add:
+    #   "mercari": MercariAdapter
+    #   "poshmark": PoshmarkAdapter
     """
     client_id, client_secret, env = _ebay_creds()
     has_creds = bool(client_id and client_secret)
@@ -713,8 +718,15 @@ def search(
     category_id: str = "",         # eBay category ID — forwarded to Browse API / scraper _sacat
     adapter: str = "auto",         # "auto" | "api" | "scraper" — override adapter selection
     refresh: bool = False,         # when True, bypass cache read (still writes fresh result)
+    platform: str = Query("ebay", description="Marketplace platform to search"),
     session: CloudUser = Depends(get_session),
 ):
+    if platform not in SUPPORTED_PLATFORMS:
+        raise HTTPException(
+            status_code=422,
+            detail=f"Platform {platform!r} is not yet supported. Supported: {sorted(SUPPORTED_PLATFORMS)}",
+        )
+
     # If the user pasted an eBay listing or checkout URL, extract the item ID
     # and use it as the search query so the exact item surfaces in results.
     ebay_item_id = _extract_ebay_item_id(q)
@@ -909,8 +921,8 @@ def search(
         raise HTTPException(status_code=502, detail=f"eBay search failed: {e}")
 
     log.info(
-        "search auth=%s tier=%s adapter=%s pages=%d queries=%d listings=%d q=%r",
-        _auth_label(session.user_id), session.tier, adapter_used,
+        "search platform=%s auth=%s tier=%s adapter=%s pages=%d queries=%d listings=%d q=%r",
+        platform, _auth_label(session.user_id), session.tier, adapter_used,
         pages, len(ebay_queries), len(listings), q,
     )
 
@@ -1073,6 +1085,7 @@ def search_async(
     category_id: str = "",
     adapter: str = "auto",
     refresh: bool = False,          # when True, bypass cache read (still writes fresh result)
+    platform: str = Query("ebay", description="Marketplace platform to search"),
     session: CloudUser = Depends(get_session),
 ):
     """Async variant of GET /api/search.
@@ -1088,6 +1101,12 @@ def search_async(
        "seller": {...}, "market_price": ...}              (enrichment updates)
       None                                               (sentinel — stream finished)
     """
+    if platform not in SUPPORTED_PLATFORMS:
+        raise HTTPException(
+            status_code=422,
+            detail=f"Platform {platform!r} is not yet supported. Supported: {sorted(SUPPORTED_PLATFORMS)}",
+        )
+
     # Validate / normalise params — same logic as synchronous endpoint.
     ebay_item_id = _extract_ebay_item_id(q)
     if ebay_item_id:
@@ -1285,8 +1304,8 @@ def search_async(
                 comps_future.result()
 
             log.info(
-                "async_search auth=%s tier=%s adapter=%s pages=%d listings=%d q=%r",
-                _auth_label(_user_id), _tier, adapter_used, pages, len(listings), q_norm,
+                "async_search platform=%s auth=%s tier=%s adapter=%s pages=%d listings=%d q=%r",
+                platform, _auth_label(_user_id), _tier, adapter_used, pages, len(listings), q_norm,
             )
 
             shared_store = Store(_shared_db)
diff --git a/app/platforms/__init__.py b/app/platforms/__init__.py
index 1ed2dd0..fb8dd63 100644
--- a/app/platforms/__init__.py
+++ b/app/platforms/__init__.py
@@ -7,6 +7,10 @@ from typing import Optional
 
 from app.db.models import Listing, Seller
 
+# Single source of truth for platform validation.
+# Phase 2 will extend this set as new adapters are implemented.
+SUPPORTED_PLATFORMS: frozenset[str] = frozenset({"ebay"})
+
 
 @dataclass
 class SearchFilters:
@@ -18,6 +22,8 @@ class SearchFilters:
     must_include: list[str] = field(default_factory=list)  # client-side title filter
     must_exclude: list[str] = field(default_factory=list)  # forwarded to eBay -term AND client-side
     category_id: Optional[str] = None                      # eBay category ID (e.g. "27386" = GPUs)
+    must_include_mode: str = "all"                         # "all" | "any" | "groups"
+    adapter: str = "auto"                                  # "auto" | "api" | "scraper"
 
 
 class PlatformAdapter(ABC):
diff --git a/web/src/components/SearchProgress.vue b/web/src/components/SearchProgress.vue
index 0a6d705..ebfb475 100644
--- a/web/src/components/SearchProgress.vue
+++ b/web/src/components/SearchProgress.vue
@@ -7,7 +7,7 @@
 
     <!-- Status line -->
     <p class="progress-label">
-      Searching eBay for <strong>{{ query }}</strong>…
+      Searching <strong>{{ platformLabel }}</strong> for <strong>{{ query }}</strong>…
     </p>
 
     <!-- Skeleton listing cards -->
@@ -28,7 +28,19 @@
 </template>
 
 <script setup lang="ts">
-defineProps<{ query: string }>()
+import { computed } from 'vue'
+
+const props = defineProps<{ query: string; platform?: string }>()
+
+const PLATFORM_LABELS: Record<string, string> = {
+  ebay: 'eBay',
+  mercari: 'Mercari',
+  poshmark: 'Poshmark',
+}
+
+const platformLabel = computed(() =>
+  PLATFORM_LABELS[props.platform ?? 'ebay'] ?? props.platform ?? 'eBay'
+)
 </script>
 
 <style scoped>
diff --git a/web/src/stores/search.ts b/web/src/stores/search.ts
index cb39160..ca9d8e6 100644
--- a/web/src/stores/search.ts
+++ b/web/src/stores/search.ts
@@ -59,6 +59,11 @@ export interface SavedSearch {
   filters_json: string   // JSON blob of SearchFilters subset
   created_at: string | null
   last_run_at: string | null
+  // Monitor settings (migration 014)
+  monitor_enabled: boolean
+  poll_interval_min: number
+  min_trust_score: number
+  last_checked_at: string | null
 }
 
 export interface SearchParamsResult {
@@ -93,6 +98,7 @@ export interface SearchFilters {
   mustExclude?: string         // comma-separated; forwarded to eBay -term AND client-side
   categoryId?: string          // eBay category ID (e.g. "27386" = Graphics/Video Cards)
   adapter?: 'auto' | 'api' | 'scraper'  // override adapter selection
+  platform?: string            // target platform; defaults to 'ebay' when omitted
 }
 
 // ── Session cache ─────────────────────────────────────────────────────────────
@@ -173,6 +179,7 @@ export const useSearchStore = defineStore('search', () => {
       if (filters.mustExclude?.trim()) params.set('must_exclude', filters.mustExclude.trim())
       if (filters.categoryId?.trim()) params.set('category_id', filters.categoryId.trim())
       if (filters.adapter && filters.adapter !== 'auto') params.set('adapter', filters.adapter)
+      if (filters.platform && filters.platform !== 'ebay') params.set('platform', filters.platform)
 
       // Use the async endpoint: returns 202 immediately with a session_id, then
       // streams listings + trust scores via SSE as the scrape completes.
diff --git a/web/src/views/SearchView.vue b/web/src/views/SearchView.vue
index 76a7879..00b753f 100644
--- a/web/src/views/SearchView.vue
+++ b/web/src/views/SearchView.vue
@@ -2,8 +2,29 @@
   <div class="search-view">
     <!-- Search bar -->
     <header class="search-header">
+      <div class="platform-tabs" role="tablist" aria-label="Search platform">
+        <button
+          v-for="p in PLATFORMS"
+          :key="p.value"
+          type="button"
+          role="tab"
+          class="platform-tab"
+          :class="{
+            'platform-tab--active': filters.platform === p.value,
+            'platform-tab--soon': !p.available,
+          }"
+          :aria-selected="filters.platform === p.value"
+          :disabled="!p.available"
+          :title="p.available ? p.label : `${p.label} — coming soon`"
+          @click="p.available && (filters.platform = p.value)"
+        >
+          {{ p.label }}
+          <span v-if="!p.available" class="platform-tab__soon">soon</span>
+        </button>
+      </div>
       <form class="search-form" @submit.prevent="onSearch" role="search">
         <div class="search-form-row1">
+          <template v-if="filters.platform === 'ebay' || !filters.platform">
           <label for="cat-select" class="sr-only">Category</label>
           <select
             id="cat-select"
@@ -20,6 +41,7 @@
               </option>
             </optgroup>
           </select>
+          </template>
           <label for="search-input" class="sr-only">Search listings</label>
           <input
             id="search-input"
@@ -116,6 +138,7 @@
 
         <!-- ── eBay Search Parameters ─────────────────────────────────────── -->
         <!-- These are sent to eBay. Changes require a new search to take effect. -->
+        <template v-if="filters.platform === 'ebay' || !filters.platform">
         <h2 class="filter-section-heading filter-section-heading--search">
           eBay Search
         </h2>
@@ -216,6 +239,7 @@
             <p class="filter-pages-hint">Excludes forwarded to eBay on re-search</p>
           </div>
         </fieldset>
+        </template>
 
         <!-- ── Post-search Filters ────────────────────────────────────────── -->
         <!-- Applied locally to current results — no re-search needed. -->
@@ -356,7 +380,7 @@
         </div>
 
         <!-- Loading (scraping in progress, no results yet) -->
-        <SearchProgress v-else-if="store.loading && !store.results.length" :query="store.query" />
+        <SearchProgress v-else-if="store.loading && !store.results.length" :query="store.query" :platform="filters.platform ?? 'ebay'" />
 
         <!-- No results -->
         <div v-else-if="!store.results.length && !store.loading && store.query" class="results-empty">
@@ -636,6 +660,7 @@ const DEFAULT_FILTERS: SearchFilters = {
   mustExclude: '',
   categoryId: '',
   adapter: 'auto' as 'auto' | 'api' | 'scraper',
+  platform: 'ebay',
 }
 
 const filters = reactive<SearchFilters>({ ...DEFAULT_FILTERS })
@@ -671,6 +696,12 @@ const parsedMustIncludeGroups = computed(() =>
     .filter(g => g.length > 0)
 )
 
+const PLATFORMS: { value: string; label: string; available: boolean }[] = [
+  { value: 'ebay',     label: 'eBay',     available: true },
+  { value: 'mercari',  label: 'Mercari',  available: false },
+  { value: 'poshmark', label: 'Poshmark', available: false },
+]
+
 const INCLUDE_MODES: { value: MustIncludeMode; label: string }[] = [
   { value: 'all',    label: 'All' },
   { value: 'any',    label: 'Any' },
@@ -1795,4 +1826,53 @@ async function onSearch() {
   to   { opacity: 1; transform: translateY(0); }
 }
 
+/* ── Platform tab strip ──────────────────────────────────────────────── */
+.platform-tabs {
+  display: flex;
+  gap: var(--space-1);
+  margin-bottom: var(--space-3);
+}
+
+.platform-tab {
+  display: inline-flex;
+  align-items: center;
+  gap: var(--space-1);
+  padding: var(--space-1) var(--space-3);
+  background: transparent;
+  border: 1.5px solid var(--color-border);
+  border-radius: var(--radius-full);
+  color: var(--color-text-muted);
+  font-family: var(--font-body);
+  font-size: 0.8125rem;
+  font-weight: 500;
+  cursor: pointer;
+  transition: border-color 150ms ease, color 150ms ease, background 150ms ease;
+  white-space: nowrap;
+}
+
+.platform-tab:hover:not(:disabled):not(.platform-tab--active) {
+  border-color: var(--app-primary);
+  color: var(--app-primary);
+}
+
+.platform-tab--active {
+  background: var(--app-primary);
+  border-color: var(--app-primary);
+  color: var(--color-text-inverse);
+  font-weight: 600;
+}
+
+.platform-tab--soon {
+  opacity: 0.45;
+  cursor: not-allowed;
+}
+
+.platform-tab__soon {
+  font-size: 0.625rem;
+  font-weight: 700;
+  text-transform: uppercase;
+  letter-spacing: 0.06em;
+  opacity: 0.8;
+}
+
 </style>