diff --git a/Bookly.lit.md b/Bookly.lit.md
index 8870a52..9eda36e 100644
--- a/Bookly.lit.md
+++ b/Bookly.lit.md
@@ -1568,9 +1568,12 @@ in `static/chat.js` already renders model replies with
 impossible today. The CSP exists to catch any future regression
 that accidentally switches to `innerHTML`.
 
-The `/architecture` route overrides the middleware CSP with a
-more permissive one because pandoc's standalone HTML has inline
-styles.
+Datadog RUM adds three narrow allowances to that baseline: the
+Browser SDK CDN in `script-src`, the Datadog intake origin in
+`connect-src`, and `worker-src blob:` for Session Replay. The
+real environment gate lives in `static/rum.js`, which checks for
+exactly `bookly.codyborders.com` before loading the SDK, so
+localhost and preview hosts still stay dark.
 
 ## Sliding-window rate limiter
 
@@ -1610,9 +1613,13 @@ the agent becomes 400, anything else becomes 500.
 
 This is where the woven literate program is served. The handler
 reads `static/architecture.html` (produced by pandoc from this
-file) and returns it with a relaxed CSP. If the file does not
-exist yet, the route 404s with a clear message rather than
-raising a 500.
+file) and returns it with a relaxed CSP. The one deliberate CSP
+change is `style-src 'unsafe-inline'`, because pandoc's
+standalone HTML emits inline styles. The page also gets the same
+`/static/rum.js` bootstrap as the chat UI, but that injection
+happens at response time so the generated artifact on disk stays
+unchanged. If the file does not exist yet, the route 404s with a
+clear message rather than raising a 500.
 
 ```python {chunk="server-py" file="server.py"}
 """FastAPI app for Bookly. Hosts /api/chat, /health, and the static chat UI.
@@ -1662,20 +1669,66 @@ app = FastAPI(title="Bookly", docs_url=None, redoc_url=None)
 # ---------------------------------------------------------------------------
 
 
+_DATADOG_SCRIPT_ORIGIN = "https://www.datadoghq-browser-agent.com"
+_DATADOG_RUM_INTAKE_ORIGIN = "https://browser-intake-datadoghq.com"
+_RUM_BOOTSTRAP_TAG = '<script src="/static/rum.js"></script>'
+
+
+def _build_content_security_policy(*, allow_inline_styles: bool) -> str:
+    """Return the CSP shared by the chat UI and the architecture page.
+
+    Datadog RUM needs explicit allowances for its CDN loader, its intake
+    endpoint, and its Session Replay worker. We keep the policy otherwise
+    strict and let the browser-side bootstrap decide whether the current host
+    is allowed to initialize RUM at all.
+    """
+    style_source = "style-src 'self'"
+    if allow_inline_styles:
+        style_source = "style-src 'self' 'unsafe-inline'"
+
+    directives = (
+        "default-src 'self'",
+        f"script-src 'self' {_DATADOG_SCRIPT_ORIGIN}",
+        style_source,
+        "img-src 'self' data:",
+        f"connect-src 'self' {_DATADOG_RUM_INTAKE_ORIGIN}",
+        "worker-src blob:",
+        "object-src 'none'",
+        "base-uri 'none'",
+        "frame-ancestors 'none'",
+        "form-action 'self'",
+    )
+    return "; ".join(directives)
+
+
+def _inject_rum_bootstrap(html: str) -> str:
+    """Inject the shared RUM bootstrap into a standalone HTML document.
+
+    `/architecture` serves a prebuilt Pandoc artifact from disk. Injecting the
+    shared bootstrap here keeps the artifact byte-for-byte unchanged while
+    ensuring the live page gets the same RUM loader as `/static/index.html`.
+    """
+    if not html:
+        raise ValueError("html must be non-empty")
+    if _RUM_BOOTSTRAP_TAG in html:
+        return html
+
+    head_close = "</head>"
+    if head_close not in html:
+        raise ValueError("architecture html is missing </head>")
+
+    updated_html = html.replace(head_close, f"  {_RUM_BOOTSTRAP_TAG}
+{head_close}", 1)
+    assert _RUM_BOOTSTRAP_TAG in updated_html
+    assert updated_html.count(_RUM_BOOTSTRAP_TAG) == 1
+    return updated_html
+
+
 _SECURITY_HEADERS: dict[str, str] = {
-    # Tight CSP: only same-origin assets, no inline scripts, no embedding.
-    # The UI is plain HTML+JS under /static, all same-origin.
-    "Content-Security-Policy": (
-        "default-src 'self'; "
-        "script-src 'self'; "
-        "style-src 'self'; "
-        "img-src 'self' data:; "
-        "connect-src 'self'; "
-        "object-src 'none'; "
-        "base-uri 'none'; "
-        "frame-ancestors 'none'; "
-        "form-action 'self'"
-    ),
+    # Tight CSP: same-origin assets plus only the Datadog endpoints needed for
+    # browser RUM and Session Replay. The exact hostname gate lives in
+    # `static/rum.js`, so localhost and preview hosts stay dark.
+    "Content-Security-Policy": _build_content_security_policy(allow_inline_styles=False),
     "X-Content-Type-Options": "nosniff",
     "X-Frame-Options": "DENY",
     "Referrer-Policy": "no-referrer",
@@ -1885,16 +1938,9 @@ _ARCHITECTURE_HTML_PATH = _STATIC_DIR / "architecture.html"
 
 # Pandoc-generated literate program. The HTML comes from weaving Bookly.lit.md
 # and contains inline styles (and inline SVG from mermaid-filter), so the
-# default strict CSP must be relaxed for this one route.
-_ARCHITECTURE_CSP = (
-    "default-src 'self'; "
-    "style-src 'self' 'unsafe-inline'; "
-    "script-src 'none'; "
-    "img-src 'self' data:; "
-    "object-src 'none'; "
-    "base-uri 'none'; "
-    "frame-ancestors 'none'"
-)
+# chat-page CSP needs one change here: allow inline styles while keeping the
+# same Datadog allowances used by the shared RUM bootstrap.
+_ARCHITECTURE_CSP = _build_content_security_policy(allow_inline_styles=True)
 
 
 @app.get("/architecture", response_class=HTMLResponse)
@@ -1907,7 +1953,7 @@ def architecture() -> HTMLResponse:
             status_code=404,
             detail="Architecture document has not been built yet.",
         )
-    response = HTMLResponse(content=html)
+    response = HTMLResponse(content=_inject_rum_bootstrap(html))
     response.headers["Content-Security-Policy"] = _ARCHITECTURE_CSP
     return response
 
diff --git a/server.py b/server.py
index 8f77b7a..e082113 100644
--- a/server.py
+++ b/server.py
@@ -45,20 +45,65 @@ app = FastAPI(title="Bookly", docs_url=None, redoc_url=None)
 # ---------------------------------------------------------------------------
 
 
+_DATADOG_SCRIPT_ORIGIN = "https://www.datadoghq-browser-agent.com"
+_DATADOG_RUM_INTAKE_ORIGIN = "https://browser-intake-datadoghq.com"
+_RUM_BOOTSTRAP_TAG = '<script src="/static/rum.js"></script>'
+
+
+def _build_content_security_policy(*, allow_inline_styles: bool) -> str:
+    """Return the CSP shared by the chat UI and the architecture page.
+
+    Datadog RUM needs explicit allowances for its CDN loader, its intake
+    endpoint, and its Session Replay worker. We keep the policy otherwise
+    strict and let the browser-side bootstrap decide whether the current host
+    is allowed to initialize RUM at all.
+    """
+    style_source = "style-src 'self'"
+    if allow_inline_styles:
+        style_source = "style-src 'self' 'unsafe-inline'"
+
+    directives = (
+        "default-src 'self'",
+        f"script-src 'self' {_DATADOG_SCRIPT_ORIGIN}",
+        style_source,
+        "img-src 'self' data:",
+        f"connect-src 'self' {_DATADOG_RUM_INTAKE_ORIGIN}",
+        "worker-src blob:",
+        "object-src 'none'",
+        "base-uri 'none'",
+        "frame-ancestors 'none'",
+        "form-action 'self'",
+    )
+    return "; ".join(directives)
+
+
+def _inject_rum_bootstrap(html: str) -> str:
+    """Inject the shared RUM bootstrap into a standalone HTML document.
+
+    `/architecture` serves a prebuilt Pandoc artifact from disk. Injecting the
+    shared bootstrap here keeps the artifact byte-for-byte unchanged while
+    ensuring the live page gets the same RUM loader as `/static/index.html`.
+    """
+    if not html:
+        raise ValueError("html must be non-empty")
+    if _RUM_BOOTSTRAP_TAG in html:
+        return html
+
+    head_close = "</head>"
+    if head_close not in html:
+        raise ValueError("architecture html is missing </head>")
+
+    updated_html = html.replace(head_close, f"  {_RUM_BOOTSTRAP_TAG}\n{head_close}", 1)
+    assert _RUM_BOOTSTRAP_TAG in updated_html
+    assert updated_html.count(_RUM_BOOTSTRAP_TAG) == 1
+    return updated_html
+
+
 _SECURITY_HEADERS: dict[str, str] = {
-    # Tight CSP: only same-origin assets, no inline scripts, no embedding.
-    # The UI is plain HTML+JS under /static, all same-origin.
-    "Content-Security-Policy": (
-        "default-src 'self'; "
-        "script-src 'self'; "
-        "style-src 'self'; "
-        "img-src 'self' data:; "
-        "connect-src 'self'; "
-        "object-src 'none'; "
-        "base-uri 'none'; "
-        "frame-ancestors 'none'; "
-        "form-action 'self'"
-    ),
+    # Tight CSP: same-origin assets plus only the Datadog endpoints needed for
+    # browser RUM and Session Replay. The exact hostname gate lives in
+    # `static/rum.js`, so localhost and preview hosts stay dark.
+    "Content-Security-Policy": _build_content_security_policy(allow_inline_styles=False),
     "X-Content-Type-Options": "nosniff",
     "X-Frame-Options": "DENY",
     "Referrer-Policy": "no-referrer",
@@ -268,16 +313,9 @@ _ARCHITECTURE_HTML_PATH = _STATIC_DIR / "architecture.html"
 
 # Pandoc-generated literate program. The HTML comes from weaving Bookly.lit.md
 # and contains inline styles (and inline SVG from mermaid-filter), so the
-# default strict CSP must be relaxed for this one route.
-_ARCHITECTURE_CSP = (
-    "default-src 'self'; "
-    "style-src 'self' 'unsafe-inline'; "
-    "script-src 'none'; "
-    "img-src 'self' data:; "
-    "object-src 'none'; "
-    "base-uri 'none'; "
-    "frame-ancestors 'none'"
-)
+# chat-page CSP needs one change here: allow inline styles while keeping the
+# same Datadog allowances used by the shared RUM bootstrap.
+_ARCHITECTURE_CSP = _build_content_security_policy(allow_inline_styles=True)
 
 
 @app.get("/architecture", response_class=HTMLResponse)
@@ -290,7 +328,7 @@ def architecture() -> HTMLResponse:
             status_code=404,
             detail="Architecture document has not been built yet.",
         )
-    response = HTMLResponse(content=html)
+    response = HTMLResponse(content=_inject_rum_bootstrap(html))
     response.headers["Content-Security-Policy"] = _ARCHITECTURE_CSP
     return response
 
diff --git a/static/index.html b/static/index.html
index ea2067a..6d70203 100644
--- a/static/index.html
+++ b/static/index.html
@@ -5,6 +5,7 @@
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
   <title>Bookly Support</title>
   <link rel="stylesheet" href="/static/style.css" />
+  <script src="/static/rum.js"></script>
 </head>
 <body>
   <main class="chat">
diff --git a/static/rum.js b/static/rum.js
new file mode 100644
index 0000000..690a7dd
--- /dev/null
+++ b/static/rum.js
@@ -0,0 +1,77 @@
+(function () {
+  "use strict";
+
+  const ALLOWED_HOSTNAME = "bookly.codyborders.com";
+  const DATADOG_AGENT_URL =
+    "https://www.datadoghq-browser-agent.com/us1/v6/datadog-rum.js";
+  const RUM_CONFIG = Object.freeze({
+    applicationId: "ad60336f-85fe-4631-9469-973180243552",
+    clientToken: "pube161402da279b685acbb640a4366129b",
+    site: "datadoghq.com",
+    service: "csb",
+    env: "prod",
+    version: "0.1",
+    sessionSampleRate: 100,
+    sessionReplaySampleRate: 100,
+    trackResources: true,
+    trackUserInteractions: true,
+    trackLongTasks: true,
+    defaultPrivacyLevel: "allow",
+  });
+
+  function initializeRum(win) {
+    if (win.__booklyRumStarted === true) {
+      return;
+    }
+
+    if (!win.DD_RUM) {
+      console.error("Datadog RUM agent was not available after loading.");
+      return;
+    }
+
+    win.DD_RUM.init(RUM_CONFIG);
+    win.__booklyRumStarted = true;
+    win.__booklyRumLoading = false;
+  }
+
+  function loadRumAgent(doc, win) {
+    const headEl = doc.head;
+    if (!headEl) {
+      console.error("Datadog RUM was not loaded because document.head is missing.");
+      return;
+    }
+
+    const scriptEl = doc.createElement("script");
+    scriptEl.src = DATADOG_AGENT_URL;
+    scriptEl.async = true;
+    scriptEl.addEventListener("load", function () {
+      initializeRum(win);
+    });
+    scriptEl.addEventListener("error", function () {
+      win.__booklyRumLoading = false;
+      console.error("Datadog RUM agent failed to load.");
+    });
+
+    win.__booklyRumLoading = true;
+    headEl.appendChild(scriptEl);
+  }
+
+  if (window.location.hostname !== ALLOWED_HOSTNAME) {
+    return;
+  }
+
+  if (window.__booklyRumStarted === true) {
+    return;
+  }
+
+  if (window.__booklyRumLoading === true) {
+    return;
+  }
+
+  if (window.DD_RUM) {
+    initializeRum(window);
+    return;
+  }
+
+  loadRumAgent(document, window);
+})();
diff --git a/tests/test_server.py b/tests/test_server.py
new file mode 100644
index 0000000..185fc79
--- /dev/null
+++ b/tests/test_server.py
@@ -0,0 +1,76 @@
+"""Server and static asset tests for Bookly's HTTP surface.
+
+Goal: verify the shared Datadog RUM bootstrap is exposed on both public HTML
+pages, and verify the Content-Security-Policy permits only the Datadog
+origins required for RUM and Session Replay.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from fastapi.testclient import TestClient
+
+import server
+
+client = TestClient(server.app)
+
+_REPO_ROOT = Path(__file__).resolve().parent.parent
+_DATADOG_SCRIPT_ORIGIN = "https://www.datadoghq-browser-agent.com"
+_DATADOG_RUM_INTAKE_ORIGIN = "https://browser-intake-datadoghq.com"
+
+
+def _read_repo_text(relative_path: str) -> str:
+    path = _REPO_ROOT / relative_path
+    assert path.is_file(), f"expected file at {path}"
+    text = path.read_text(encoding="utf-8")
+    assert text, f"expected non-empty file at {path}"
+    return text
+
+
+def test_static_index_html_loads_shared_rum_bootstrap():
+    response = client.get("/static/index.html")
+    assert response.status_code == 200
+    assert "/static/rum.js" in response.text
+
+
+def test_architecture_page_loads_shared_rum_bootstrap():
+    response = client.get("/architecture")
+    assert response.status_code == 200
+    assert "/static/rum.js" in response.text
+
+
+def test_static_page_csp_allows_only_required_datadog_origins():
+    response = client.get("/static/index.html")
+    csp = response.headers["content-security-policy"]
+    assert response.status_code == 200
+    assert f"script-src 'self' {_DATADOG_SCRIPT_ORIGIN}" in csp
+    assert f"connect-src 'self' {_DATADOG_RUM_INTAKE_ORIGIN}" in csp
+    assert "worker-src blob:" in csp
+    assert "style-src 'self'" in csp
+
+
+def test_architecture_page_csp_keeps_inline_styles_and_datadog_allowlist():
+    response = client.get("/architecture")
+    csp = response.headers["content-security-policy"]
+    assert response.status_code == 200
+    assert f"script-src 'self' {_DATADOG_SCRIPT_ORIGIN}" in csp
+    assert f"connect-src 'self' {_DATADOG_RUM_INTAKE_ORIGIN}" in csp
+    assert "worker-src blob:" in csp
+    assert "style-src 'self' 'unsafe-inline'" in csp
+
+
+def test_rum_bootstrap_file_contains_expected_exact_configuration():
+    rum_js = _read_repo_text("static/rum.js")
+    assert "bookly.codyborders.com" in rum_js
+    assert "ad60336f-85fe-4631-9469-973180243552" in rum_js
+    assert "pube161402da279b685acbb640a4366129b" in rum_js
+    assert 'service: "csb"' in rum_js
+    assert 'env: "prod"' in rum_js
+    assert 'version: "0.1"' in rum_js
+    assert "https://www.datadoghq-browser-agent.com/us1/v6/datadog-rum.js" in rum_js
+
+
+def test_runtime_injection_leaves_architecture_artifact_unchanged():
+    architecture_html = _read_repo_text("static/architecture.html")
+    assert "/static/rum.js" not in architecture_html