diff --git a/.gitignore b/.gitignore
index b450be4..b64188c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,7 @@
 .demo.log
 .demo.pid
 .boot.log
+
+# Generated by `npm run build:docs` — regenerated on every full build
+# (prebuild) and on demand during dev. Don't commit the artifact.
+/public/docs-index.json
diff --git a/app/app.css b/app/app.css
index 12f2064..6dfa9da 100644
--- a/app/app.css
+++ b/app/app.css
@@ -33,6 +33,7 @@
 @source "../../lib-code-ui/src";
 @source "../../lib-diagram-ui/src";
 @source "../../lib-onboarding-ui/src";
+@source "../../lib-lexical-rag-ui/src";
 @source "../../lib-notification-ui/src";
 /* CREMA:SOURCES */
 
diff --git a/app/lib/admin-tools.ts b/app/lib/admin-tools.ts
index 59cfd98..6260fd2 100644
--- a/app/lib/admin-tools.ts
+++ b/app/lib/admin-tools.ts
@@ -15,9 +15,13 @@ import {
   suspendTenant,
   type Tenant,
 } from "~/lib/arcadia/tenants"
-import { searchDocs } from "~/lib/docs-search"
+import { createRAGClient } from "@crema/lexical-rag-ui"
 import { BLOCK_INDEX, getBlockSchema } from "~/lib/block-schemas"
 
+// Lazy singleton — first tool call fetches /docs-index.json, subsequent
+// calls reuse the parsed MiniSearch instance.
+const docsClient = createRAGClient("/docs-index.json")
+
 export type ToolCall = {
   name: string
   args: Record<string, unknown>
@@ -253,8 +257,22 @@ const TOOLS: ToolDef[] = [
         10,
         Math.max(1, typeof args.limit === "number" ? args.limit : 5),
       )
-      const hits = await searchDocs(query, limit)
-      return { query, count: hits.length, hits }
+      const hits = await docsClient.search(query, { limit })
+      // Tool-shape parity with the previous searchDocs() return: collapse
+      // tags[] back to category for now so the agent's prior expectations
+      // and any cached examples still parse cleanly.
+      return {
+        query,
+        count: hits.length,
+        hits: hits.map((h) => ({
+          id: h.id,
+          title: h.title,
+          sourcePath: h.sourcePath,
+          category: h.tags[0] ?? "",
+          excerpt: h.excerpt,
+          score: h.score,
+        })),
+      }
     },
   },
   {
diff --git a/app/routes/ai.tsx b/app/routes/ai.tsx
index 5b43392..ca08361 100644
--- a/app/routes/ai.tsx
+++ b/app/routes/ai.tsx
@@ -69,7 +69,19 @@ import { Avatar, AvatarFallback } from "~/components/ui/avatar"
 import { pageTitle } from "~/lib/page-meta"
 import { useArcadiaClient } from "@crema/arcadia-client"
 import type { Message as LLMMessage, ToolCall } from "@crema/llm-ui"
-import type { DocHit } from "~/lib/docs-search"
+// Shape of a single hit returned by the `search_docs` tool. Defined here
+// rather than imported from the lib because the tool wrapper in
+// admin-tools.ts intentionally collapses the lib's `tags[]` back to a
+// single `category` for tool-response stability — this type matches
+// what the model actually sees.
+type DocHit = {
+  id: string
+  title: string
+  sourcePath: string
+  category: string
+  excerpt: string
+  score: number
+}
 import {
   AgentAvatar,
   ToolCallCard,
diff --git a/package-lock.json b/package-lock.json
index 627de6b..3e1d867 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -15,6 +15,7 @@
         "d3-geo": "^3.1.1",
         "isbot": "^5.1.36",
         "lucide-react": "^1.8.0",
+        "minisearch": "^7.2.0",
         "motion": "^12.38.0",
         "openapi-fetch": "^0.17.0",
         "phoenix": "^1.8.5",
@@ -7264,6 +7265,12 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/minisearch": {
+      "version": "7.2.0",
+      "resolved": "https://registry.npmjs.org/minisearch/-/minisearch-7.2.0.tgz",
+      "integrity": "sha512-dqT2XBYUOZOiC5t2HRnwADjhNS2cecp9u+TJRiJ1Qp/f5qjkeT5APcGPjHw+bz89Ms8Jp+cG4AlE+QZ/QnDglg==",
+      "license": "MIT"
+    },
     "node_modules/morgan": {
       "version": "1.10.1",
       "resolved": "https://registry.npmjs.org/morgan/-/morgan-1.10.1.tgz",
diff --git a/package.json b/package.json
index 057d148..bbb614a 100644
--- a/package.json
+++ b/package.json
@@ -3,13 +3,15 @@
   "private": true,
   "type": "module",
   "scripts": {
+    "prebuild": "npm run build:docs",
     "build": "react-router build",
     "dev": "react-router dev",
     "start": "react-router-serve ./build/server/index.js",
     "typecheck": "react-router typegen && tsc",
     "test": "vitest run",
     "test:watch": "vitest",
-    "sync-libs": "node scripts/sync-libs.mjs"
+    "sync-libs": "node scripts/sync-libs.mjs",
+    "build:docs": "node scripts/build-docs-index.mjs"
   },
   "dependencies": {
     "@base-ui/react": "^1.4.0",
@@ -21,6 +23,7 @@
     "d3-geo": "^3.1.1",
     "isbot": "^5.1.36",
     "lucide-react": "^1.8.0",
+    "minisearch": "^7.2.0",
     "motion": "^12.38.0",
     "openapi-fetch": "^0.17.0",
     "phoenix": "^1.8.5",
diff --git a/scripts/build-docs-index.mjs b/scripts/build-docs-index.mjs
new file mode 100644
index 0000000..9f0cc99
--- /dev/null
+++ b/scripts/build-docs-index.mjs
@@ -0,0 +1,39 @@
+#!/usr/bin/env node
+// Build the /docs-index.json bundle consumed by @crema/lexical-rag-ui at
+// runtime. Thin wrapper — all engine logic lives in the lib's builder.ts;
+// this file owns the per-app config (which arcadia-app docs to index and
+// how to tag them).
+//
+// Run: npm run build:docs
+//
+// Allowlist is intentional. Excluded files are aspirational/stale and
+// would poison answers (TODO lists, design docs for unshipped features,
+// sub-app READMEs that aren't part of arcadia-core). To add a file,
+// append to SOURCES below — don't auto-discover.
+
+import { resolve, dirname } from "node:path"
+import { fileURLToPath } from "node:url"
+
+import MiniSearch from "minisearch"
+import { buildIndex } from "../../lib-lexical-rag-ui/src/builder.mjs"
+
+const ROOT = resolve(dirname(fileURLToPath(import.meta.url)), "..")
+const ARCADIA = resolve(ROOT, "../reference/arcadia-app")
+const OUT = resolve(ROOT, "public/docs-index.json")
+
+const SOURCES = [
+  { path: "README.md", tags: ["core"] },
+  { path: "docs/ARCADIA.md", tags: ["core"] },
+  { path: "docs/MODULAR_MONOLITH.md", tags: ["core"] },
+  { path: "apps/arcadia_core/README.md", tags: ["core"] },
+  { path: "DEPLOY.md", tags: ["ops"] },
+  { path: "DEV_DEPLOY.md", tags: ["ops"] },
+  { path: "DEV_SETUP.md", tags: ["ops"] },
+]
+
+buildIndex({
+  miniSearch: MiniSearch,
+  rootDir: ARCADIA,
+  outPath: OUT,
+  sources: SOURCES,
+})
diff --git a/tsconfig.json b/tsconfig.json
index 0d09a40..099a58f 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -62,6 +62,8 @@
       "@crema/diagram-ui/*": ["../lib-diagram-ui/src/*"],
       "@crema/onboarding-ui": ["../lib-onboarding-ui/src/index.tsx"],
       "@crema/onboarding-ui/*": ["../lib-onboarding-ui/src/*"],
+      "@crema/lexical-rag-ui": ["../lib-lexical-rag-ui/src/index.tsx"],
+      "@crema/lexical-rag-ui/*": ["../lib-lexical-rag-ui/src/*"],
       "// CREMA:PATHS": [""],
       "react": ["./node_modules/@types/react"],
       "react/*": ["./node_modules/@types/react/*"],
@@ -69,6 +71,7 @@
       "react-dom/*": ["./node_modules/@types/react-dom/*"],
       "clsx": ["./node_modules/clsx"],
       "tailwind-merge": ["./node_modules/tailwind-merge"],
+      "minisearch": ["./node_modules/minisearch"],
       "lucide-react": ["./node_modules/lucide-react"],
       "openapi-fetch": ["./node_modules/openapi-fetch"],
       "openapi-fetch/*": ["./node_modules/openapi-fetch/*"],