diff --git a/docs/specs/doc-viewer.md b/docs/specs/doc-viewer.md
index 030dece..94128e7 100644
--- a/docs/specs/doc-viewer.md
+++ b/docs/specs/doc-viewer.md
@@ -1,7 +1,7 @@
 ---
 title: Documentation Viewer
-updated: 2026-06-12
-status: planned
+updated: 2026-06-19
+status: implemented
 ---
 
 Tempest should expose the project reference documentation as a public, browsable
@@ -175,25 +175,24 @@ stylesheet, for example `assets/css/components/doc-viewer.css`, and import it fr
 
 ## Phoenix implementation notes
 
-Recommended modules:
+Implemented modules:
 
 - `Tempest.Docs` context for manifest lookup, file loading, frontmatter parsing,
   Markdown rendering, and link rewriting.
-- `TempestWeb.DocController` for `index` and `show` actions.
-- `TempestWeb.DocHTML` with `index.html.heex` or `show.html.heex`.
+- `TempestWeb.DocLive` for the public `/docs` and `/docs/:slug` viewer.
 
-Recommended route placement:
+Route placement:
 
 ```elixir
 scope "/", TempestWeb do
   pipe_through :browser
 
-  get "/docs", DocController, :index
-  get "/docs/:slug", DocController, :show
+  live "/docs", DocLive, :show
+  live "/docs/:slug", DocLive, :show
 end
 ```
 
-The controller should pass assigns such as:
+The LiveView assigns:
 
 - `:documents`
 - `:document`
@@ -206,15 +205,11 @@ clear boundary function so reviewers can see where HTML safety is decided.
 
 ## Caching
 
-Docs are static project files. Initial implementation can read at request time in
-`dev` and cache in memory in `prod`. A later version can add ETags or a manifest
-checksum.
-
-A simple first-pass policy:
+Docs are static project files. The current policy is:
 
 - `dev`: read every request for fast documentation iteration
 - `test`: read every request
-- `prod`: cache rendered docs in `:persistent_term` or a supervised GenServer
+- `prod`: cache successfully rendered manifest documents in `:persistent_term`
 
 Do not cache route params that are not in the manifest.
 
diff --git a/docs/tasks/17-doc-viewer.md b/docs/tasks/17-doc-viewer.md
index 1cfae0d..ad5fdfc 100644
--- a/docs/tasks/17-doc-viewer.md
+++ b/docs/tasks/17-doc-viewer.md
@@ -33,12 +33,12 @@ Netscape Navigator-inspired shell and a web 1.0 design (with a sidebar & search)
 - [x] T17-12: Add previous/next document links based on manifest order.
 - [x] T17-13: Link the docs viewer from the home page and any relevant public
       navigation.
-- [ ] T17-14: Add ConnCase tests for `/docs`, `/docs/architecture`, unknown slugs,
+- [x] T17-14: Add ConnCase tests for `/docs`, `/docs/architecture`, unknown slugs,
       sidebar navigation, relative-link rewriting, and path traversal rejection.
-- [ ] T17-15: Add regression tests proving files outside `docs/reference/` cannot
+- [x] T17-15: Add regression tests proving files outside `docs/reference/` cannot
       be rendered.
-- [ ] T17-16: Add Hurl smoke test `test/smoke/doc-viewer.hurl`.
-- [ ] T17-17: Add production caching
+- [x] T17-16: Add Hurl smoke test `test/smoke/doc-viewer.hurl`.
+- [x] T17-17: Add production caching
 
 ## Integration Tests
 
diff --git a/lib/tempest/docs.ex b/lib/tempest/docs.ex
index f462967..e19b77a 100644
--- a/lib/tempest/docs.ex
+++ b/lib/tempest/docs.ex
@@ -94,28 +94,19 @@ defmodule Tempest.Docs do
   @doc "Fetches and renders a known reference document by slug."
   @spec fetch_document(String.t()) :: {:ok, document()} | {:error, :not_found}
   def fetch_document(slug) when is_binary(slug) do
-    with {:ok, entry} <- lookup_manifest(slug),
-         {:ok, markdown} <- read_manifest_file(entry) do
-      {frontmatter, body} = split_frontmatter(markdown)
-      title = Map.get(frontmatter, "title") || entry.title
-      updated = Map.get(frontmatter, "updated")
-      rewritten_body = rewrite_reference_links(body, entry)
-      html = MDEx.to_html!(rewritten_body, @markdown_options)
-
-      {:ok,
-       %__MODULE__{
-         slug: entry.slug,
-         path: entry.path,
-         title: title,
-         updated: updated,
-         markdown: rewritten_body,
-         html: html
-       }}
+    with {:ok, entry} <- lookup_manifest(slug) do
+      cached_document({:reference_document, entry.slug}, fn -> render_reference_document(entry) end)
     else
       _ -> {:error, :not_found}
     end
   end
 
+  @doc "Returns true when a slug is present in the fixed reference manifest."
+  @spec known_document_slug?(String.t()) :: boolean()
+  def known_document_slug?(slug) when is_binary(slug) do
+    match?({:ok, _entry}, lookup_manifest(slug))
+  end
+
   @doc "Fetches and renders a known desktop document by fixed manifest slug."
   @spec fetch_desktop_document(String.t()) :: {:ok, document()} | {:error, :not_found}
   def fetch_desktop_document(slug) when is_binary(slug) do
@@ -245,6 +236,53 @@ defmodule Tempest.Docs do
     end
   end
 
+  defp render_reference_document(entry) do
+    with {:ok, markdown} <- read_manifest_file(entry) do
+      {frontmatter, body} = split_frontmatter(markdown)
+      title = Map.get(frontmatter, "title") || entry.title
+      updated = Map.get(frontmatter, "updated")
+      rewritten_body = rewrite_reference_links(body, entry)
+      html = MDEx.to_html!(rewritten_body, @markdown_options)
+
+      {:ok,
+       %__MODULE__{
+         slug: entry.slug,
+         path: entry.path,
+         title: title,
+         updated: updated,
+         markdown: rewritten_body,
+         html: html
+       }}
+    end
+  end
+
+  defp cached_document(cache_key, render_fun) do
+    if cache_rendered_docs?() do
+      persistent_key = {__MODULE__, cache_key}
+
+      case :persistent_term.get(persistent_key, :missing) do
+        :missing ->
+          case render_fun.() do
+            {:ok, document} ->
+              :persistent_term.put(persistent_key, document)
+              {:ok, document}
+
+            error ->
+              error
+          end
+
+        document ->
+          {:ok, document}
+      end
+    else
+      render_fun.()
+    end
+  end
+
+  defp cache_rendered_docs? do
+    Application.get_env(:tempest, :env, :prod) == :prod
+  end
+
   defp reference_root do
     Path.expand("docs/reference", File.cwd!())
   end
diff --git a/lib/tempest_web/router.ex b/lib/tempest_web/router.ex
index fef2626..34f7043 100644
--- a/lib/tempest_web/router.ex
+++ b/lib/tempest_web/router.ex
@@ -5,6 +5,7 @@ defmodule TempestWeb.Router do
     plug :accepts, ["html"]
     plug :fetch_session
     plug :fetch_live_flash
+    plug :reject_unknown_doc_slug
     plug :put_root_layout, html: {TempestWeb.Layouts, :root}
     plug :protect_from_forgery
     plug :put_secure_browser_headers
@@ -131,4 +132,17 @@ defmodule TempestWeb.Router do
     |> Plug.Conn.put_resp_header("access-control-expose-headers", "dpop-nonce")
     |> Plug.Conn.put_resp_header("access-control-max-age", "100000000")
   end
+
+  defp reject_unknown_doc_slug(%Plug.Conn{method: "GET", path_info: ["docs", slug]} = conn, _opts) do
+    if Tempest.Docs.known_document_slug?(slug) do
+      conn
+    else
+      conn
+      |> Plug.Conn.put_resp_content_type("text/html")
+      |> Plug.Conn.send_resp(:not_found, "Not Found")
+      |> Plug.Conn.halt()
+    end
+  end
+
+  defp reject_unknown_doc_slug(conn, _opts), do: conn
 end
diff --git a/test/smoke/doc-viewer.hurl b/test/smoke/doc-viewer.hurl
new file mode 100644
index 0000000..5a62034
--- /dev/null
+++ b/test/smoke/doc-viewer.hurl
@@ -0,0 +1,34 @@
+GET {{base_url}}/docs
+HTTP 200
+[Asserts]
+header "content-type" contains "text/html"
+body contains "Tempest Navigator 4.0 - Reference Documentation"
+body contains "id=\"doc-bookmarks\""
+body contains "id=\"doc-content\""
+body contains "href=\"/docs/architecture\""
+body contains "Best viewed in Tempest Navigator"
+
+GET {{base_url}}/docs/architecture
+HTTP 200
+[Asserts]
+header "content-type" contains "text/html"
+body contains "Architecture"
+body contains "Reference file: architecture.md"
+body contains "Concepts"
+body contains "<pre><code"
+body contains "<table>"
+body contains "href=\"/docs/admin-operations\""
+
+GET {{base_url}}/docs/not-a-real-doc
+HTTP 404
+
+GET {{base_url}}/docs/..%2F..%2Fconfig%2Fprod.exs
+HTTP 400
+[Asserts]
+body not contains "SECRET_KEY_BASE"
+
+GET {{base_url}}/docs/..%252F..%252Fconfig%252Fprod.exs
+HTTP 404
+[Asserts]
+body not contains "SECRET_KEY_BASE"
+body not contains "TempestWeb.Endpoint"
diff --git a/test/tempest_web/live/doc_live_route_test.exs b/test/tempest_web/live/doc_live_route_test.exs
new file mode 100644
index 0000000..0513775
--- /dev/null
+++ b/test/tempest_web/live/doc_live_route_test.exs
@@ -0,0 +1,69 @@
+defmodule TempestWeb.DocLiveRouteTest do
+  use TempestWeb.ConnCase
+
+  test "GET /docs renders the reference index without authentication", %{conn: conn} do
+    conn = get(conn, ~p"/docs")
+    html = html_response(conn, 200)
+    document = LazyHTML.from_fragment(html)
+
+    assert has_selector?(document, "#tempest-docs")
+    assert has_selector?(document, "#doc-bookmarks")
+    assert has_selector?(document, "#doc-content")
+    assert has_selector?(document, ~s(a[href="/docs/architecture"]))
+    assert html =~ "Tempest Navigator 4.0 - Reference Documentation"
+    assert html =~ "Best viewed in Tempest Navigator"
+    assert html =~ "Reference Documentation"
+  end
+
+  test "GET /docs/architecture renders the architecture reference document", %{conn: conn} do
+    conn = get(conn, ~p"/docs/architecture")
+    html = html_response(conn, 200)
+    document = LazyHTML.from_fragment(html)
+
+    assert has_selector?(document, "#doc-title")
+    assert has_selector?(document, ~s(a[href="/docs/admin-operations"]))
+    assert has_selector?(document, ~s(a[href="/docs/blobs"]))
+    assert has_selector?(document, "pre code")
+    assert has_selector?(document, "table")
+    assert html =~ ~s(id="doc-title")
+    assert html =~ ">Architecture</h1>"
+    assert html =~ "Reference file: architecture.md"
+    assert html =~ "Concepts"
+  end
+
+  test "unknown slugs return 404", %{conn: conn} do
+    conn = get(conn, ~p"/docs/not-a-real-doc")
+
+    assert html_response(conn, 404)
+  end
+
+  test "path traversal attempts return 404 and do not read local files", %{conn: conn} do
+    conn = get(conn, "/docs/..%2F..%2Fconfig%2Fprod.exs")
+    html = html_response(conn, 404)
+
+    refute html =~ "SECRET_KEY_BASE"
+    refute html =~ "TempestWeb.Endpoint"
+  end
+
+  test "file-like paths outside docs/reference cannot be rendered", %{conn: conn} do
+    conn = get(conn, "/docs/CHANGELOG.md")
+
+    assert html_response(conn, 404)
+  end
+
+  test "relative links between reference docs resolve to viewer routes", %{conn: conn} do
+    conn = get(conn, ~p"/docs")
+    html = html_response(conn, 200)
+    document = LazyHTML.from_fragment(html)
+
+    assert has_selector?(document, ~s(#doc-content a[href="/docs/architecture"]))
+    assert has_selector?(document, ~s(#doc-content a[href="/docs/deployment-observability"]))
+    assert has_selector?(document, ~s(#doc-content a[href="/docs/identity-troubleshooting"]))
+  end
+
+  defp has_selector?(document, selector) do
+    document
+    |> LazyHTML.query(selector)
+    |> Enum.any?()
+  end
+end