diff --git a/blogex/mix.exs b/blogex/mix.exs
index 7e94fbb..23ba5e4 100644
--- a/blogex/mix.exs
+++ b/blogex/mix.exs
@@ -56,22 +56,22 @@ defmodule Blogex.MixProject do
   # in blogex/). Rule: the threshold is a FLOOR. Raise it as behavior-test yaks
   # land; never lower it. A drop means the change (or an exclusion) is wrong.
   #
-  # Measured 2026-10-28, with the test scaffolding below excluded: 78.59% — the
+  # Measured 2026-10-28, with the test scaffolding below excluded: 99.69% — the
   # same via `mix test --cover` and via `mix test --cover --export-coverage
   # default` + `mix test.coverage`. Floor is the integer below that.
   #
   # Excluded: the test scaffolding in `ignore_modules` below. The two registry
   # blog doubles (Blogex.Test.AlphaBlog/BetaBlog) are deliberately not listed
-  # there: they are fully exercised, and excluding them measures 78.06% — the
-  # 78 floor holds either way.
+  # there: they are fully exercised, and excluding them measures 99.69% too —
+  # the 99 floor holds either way.
   #
-  # Everything in lib/blogex counts, and today's gaps are real:
-  # Blogex.Components and Blogex.Layout are at 0% because the router tests only
-  # exercise the JSON responses — covering the rendered HTML is its own yak.
-  # Blogex.Router (72.06%) still has its HTML arms and `match _` uncovered.
+  # Everything in lib/blogex counts, and one gap is left:
+  # Blogex.LinkError is at 88.89% (8 of 9 lines). The rendered-HTML behavior
+  # tests closed the rest: Blogex.Components and Blogex.Layout went from 0% to
+  # 100%, and Blogex.Router now covers its browser arms and `match _`.
   defp test_coverage do
     [
-      summary: [threshold: 78],
+      summary: [threshold: 99],
       ignore_modules: [
         Blogex.Test.FakeBlog,
         Blogex.Test.PostBuilder,
diff --git a/blogex/test/blogex/components_test.exs b/blogex/test/blogex/components_test.exs
new file mode 100644
index 0000000..0c64289
--- /dev/null
+++ b/blogex/test/blogex/components_test.exs
@@ -0,0 +1,223 @@
+defmodule Blogex.ComponentsTest do
+  use ExUnit.Case, async: true
+
+  import Phoenix.LiveViewTest
+  import Blogex.Test.PostBuilder
+
+  @base_path "/blog/engineering"
+
+  describe "post_index/1" do
+    test "links each post title to its own page under base_path" do
+      html =
+        render_post_index([
+          build(id: "first-post", title: "First post"),
+          build(id: "second-post", title: "Second post")
+        ])
+
+      assert html =~ ~s(href="#{@base_path}/first-post")
+      assert html =~ ">First post</a>"
+      assert html =~ ~s(href="#{@base_path}/second-post")
+      assert html =~ ">Second post</a>"
+    end
+
+    test "shows each post's description" do
+      html =
+        render_post_index([
+          build(id: "processes-post", description: "Everything about processes"),
+          build(id: "supervision-post", description: "Everything about supervision")
+        ])
+
+      assert html =~ "Everything about processes"
+      assert html =~ "Everything about supervision"
+    end
+
+    test "shows date, author and tags for each post" do
+      html =
+        render_post_index([
+          build(
+            id: "authored-post",
+            date: ~D[2026-03-10],
+            author: "Ada Lovelace",
+            tags: ["elixir"]
+          )
+        ])
+
+      assert html =~ "March 10, 2026"
+      assert html =~ "by Ada Lovelace"
+      assert html =~ ~s(href="#{@base_path}/tag/elixir")
+    end
+  end
+
+  describe "post_show/1" do
+    test "renders the post title as the page heading" do
+      html = render_post_show(build(id: "heading-post", title: "Rendering Rendered HTML"))
+
+      assert html =~ "<h1>Rendering Rendered HTML</h1>"
+    end
+
+    test "renders the body as markup, not escaped text" do
+      html =
+        render_post_show(build(id: "markup-post", body: "<p>Hello <strong>world</strong></p>"))
+
+      assert html =~ "<p>Hello <strong>world</strong></p>"
+      refute html =~ "&lt;p&gt;"
+      refute html =~ "&lt;strong&gt;"
+    end
+
+    test "shows the post's date, author and tags" do
+      html =
+        render_post_show(
+          build(
+            id: "meta-post",
+            date: ~D[2026-03-10],
+            author: "Grace Hopper",
+            tags: ["compilers", "navy"]
+          )
+        )
+
+      assert html =~ ~s(<time datetime="2026-03-10">)
+      assert html =~ "March 10, 2026"
+      assert html =~ "by Grace Hopper"
+      assert html =~ ~s(href="#{@base_path}/tag/compilers")
+      assert html =~ ~s(href="#{@base_path}/tag/navy")
+    end
+  end
+
+  describe "post_meta/1" do
+    test "renders the date as a machine-readable time element and a human date" do
+      html = render_post_meta(build(date: ~D[2026-03-10]))
+
+      assert html =~ ~s(<time datetime="2026-03-10">)
+      assert html =~ "March 10, 2026"
+    end
+
+    test "shows the author when the post has one" do
+      html = render_post_meta(build(author: "Ada Lovelace"))
+
+      assert html =~ ~s(<span class="blogex-post-author">)
+      assert html =~ "by Ada Lovelace"
+    end
+
+    test "has no author line when the post has no author" do
+      html = render_post_meta(build(author: nil))
+
+      refute html =~ "blogex-post-author"
+      refute html =~ "by "
+    end
+
+    test "links every tag under base_path" do
+      html = render_post_meta(build(tags: ["elixir", "otp"]))
+
+      assert html =~ ~s(href="#{@base_path}/tag/elixir")
+      assert html =~ ~s(href="#{@base_path}/tag/otp")
+    end
+
+    test "marks only the current tag as active" do
+      html = render_post_meta(build(tags: ["elixir", "otp"]), current_tag: "elixir")
+
+      assert occurrences(html, "blogex-tag-active") == 1
+
+      assert [_, after_active] =
+               String.split(html, ~s(class="blogex-tag-link blogex-tag-active"))
+
+      assert after_active =~ ~r/^>\s*elixir\s*<\/a>/
+    end
+  end
+
+  describe "tag_list/1" do
+    test "links every tag under base_path" do
+      html = render_tag_list(["elixir", "otp"])
+
+      assert html =~ ~s(href="#{@base_path}/tag/elixir")
+      assert html =~ ~s(href="#{@base_path}/tag/otp")
+    end
+
+    test "marks only the current tag as active" do
+      html = render_tag_list(["elixir", "otp"], current_tag: "elixir")
+
+      assert occurrences(html, "blogex-tag-active") == 1
+
+      assert [_, after_active] =
+               String.split(html, ~s(class="blogex-tag-link blogex-tag-active"))
+
+      assert after_active =~ ~r/^>\s*elixir\s*<\/a>/
+    end
+  end
+
+  describe "pagination/1" do
+    test "renders nothing when there is only one page" do
+      assert render_pagination(page: 1, total_pages: 1) |> String.trim() == ""
+    end
+
+    test "on the first of several pages there is an Older link and no Newer link" do
+      html = render_pagination(page: 1, total_pages: 3)
+
+      assert html =~ "Page 1 of 3"
+      assert html =~ ~s(href="#{@base_path}?page=2")
+      assert html =~ "Older"
+      refute html =~ "Newer"
+    end
+
+    test "on a middle page there are both Newer and Older links" do
+      html = render_pagination(page: 2, total_pages: 3)
+
+      assert html =~ "Page 2 of 3"
+      assert html =~ ~s(href="#{@base_path}?page=1")
+      assert html =~ ~s(href="#{@base_path}?page=3")
+      assert html =~ "Newer"
+      assert html =~ "Older"
+    end
+
+    test "on the last page there is a Newer link and no Older link" do
+      html = render_pagination(page: 3, total_pages: 3)
+
+      assert html =~ "Page 3 of 3"
+      assert html =~ ~s(href="#{@base_path}?page=2")
+      assert html =~ "Newer"
+      refute html =~ "Older"
+    end
+  end
+
+  defp render_post_index(posts, current_tag \\ nil) do
+    render_component(&Blogex.Components.post_index/1,
+      posts: posts,
+      base_path: @base_path,
+      current_tag: current_tag
+    )
+  end
+
+  defp render_post_show(post) do
+    render_component(&Blogex.Components.post_show/1, post: post, base_path: @base_path)
+  end
+
+  defp render_post_meta(post, opts \\ []) do
+    render_component(&Blogex.Components.post_meta/1,
+      post: post,
+      base_path: @base_path,
+      current_tag: opts[:current_tag]
+    )
+  end
+
+  defp render_tag_list(tags, opts \\ []) do
+    render_component(&Blogex.Components.tag_list/1,
+      tags: tags,
+      base_path: @base_path,
+      current_tag: opts[:current_tag]
+    )
+  end
+
+  defp render_pagination(opts) do
+    render_component(&Blogex.Components.pagination/1,
+      page: opts[:page],
+      total_pages: opts[:total_pages],
+      base_path: @base_path
+    )
+  end
+
+  defp occurrences(html, token) do
+    html
+    |> String.split(token)
+    |> length()
+    |> Kernel.-(1)
+  end
+end
diff --git a/blogex/test/blogex/layout_test.exs b/blogex/test/blogex/layout_test.exs
new file mode 100644
index 0000000..3f67f64
--- /dev/null
+++ b/blogex/test/blogex/layout_test.exs
@@ -0,0 +1,132 @@
+defmodule Blogex.LayoutTest do
+  use ExUnit.Case, async: true
+
+  import Phoenix.LiveViewTest
+  import Blogex.Test.PostBuilder
+
+  @base_path "/blog/engineering"
+  @blog_title "Engineering Blog"
+  @blog_description "Notes from the platform team"
+
+  describe "page/1" do
+    test "titles the document and wraps the inner content" do
+      html = render_page("A document title")
+
+      assert html =~ "<!DOCTYPE html>"
+      assert html =~ ~s(<html lang="en">)
+      assert html =~ "<title>A document title</title>"
+    end
+
+    test "renders inner_content as markup, not escaped text" do
+      html = render_page("A document title", Phoenix.HTML.raw("<p>inner</p>"))
+
+      assert html =~ "<p>inner</p>"
+      refute html =~ "&lt;p&gt;"
+    end
+  end
+
+  describe "index_page/1" do
+    test "shows the blog title and description" do
+      html = render_index_page([])
+
+      assert html =~ "<h1>#{@blog_title}</h1>"
+      assert html =~ @blog_description
+    end
+
+    test "lists the posts with their titles linked" do
+      html = render_index_page([build(id: "first-post", title: "First post")])
+
+      assert html =~ ~s(href="#{@base_path}/first-post")
+      assert html =~ ">First post</a>"
+    end
+
+    test "shows no pagination when the blog has a single page" do
+      html = render_index_page([build(id: "only-post")], page: 1, total_pages: 1)
+
+      refute html =~ "Older"
+      refute html =~ "Newer"
+      refute html =~ "Page 1 of 1"
+    end
+
+    test "shows pagination when there is more than one page" do
+      html = render_index_page([build(id: "paged-post")], page: 2, total_pages: 3)
+
+      assert html =~ "Page 2 of 3"
+    end
+  end
+
+  describe "show_page/1" do
+    test "uses the post title as the document title" do
+      post = build(id: "titled-post", title: "A Post About Layout")
+
+      assert render_show_page(post) =~ "<title>#{post.title}</title>"
+    end
+
+    test "offers a link back to the blog index" do
+      html = render_show_page(build())
+
+      assert html =~ ~s(<a href="#{@base_path}">&larr; Back</a>)
+    end
+
+    test "renders the post body as markup, not escaped text" do
+      html = render_show_page(build(body: "<p>Hello <strong>world</strong></p>"))
+
+      assert html =~ "<p>Hello <strong>world</strong></p>"
+      refute html =~ "&lt;p&gt;"
+      refute html =~ "&lt;strong&gt;"
+    end
+  end
+
+  describe "tag_page/1" do
+    test "titles the page with the blog title and the tag" do
+      html = render_tag_page(tag: "elixir", posts: [])
+
+      assert html =~ "<title>#{@blog_title} — #elixir</title>"
+    end
+
+    test "announces the tag and lists the posts it was given" do
+      html =
+        render_tag_page(
+          tag: "elixir",
+          posts: [
+            build(id: "tagged-post", title: "Tagged post"),
+            build(id: "another-tagged-post", title: "Another tagged post")
+          ]
+        )
+
+      assert html =~ ~s(<h1>Posts tagged "elixir"</h1>)
+      assert html =~ ~s(href="#{@base_path}/tagged-post")
+      assert html =~ ">Tagged post</a>"
+      assert html =~ ~s(href="#{@base_path}/another-tagged-post")
+      assert html =~ ">Another tagged post</a>"
+    end
+  end
+
+  defp render_page(title, inner_content \\ Phoenix.HTML.raw("<p>inner</p>")) do
+    render_component(&Blogex.Layout.page/1, title: title, inner_content: inner_content)
+  end
+
+  defp render_index_page(posts, opts \\ []) do
+    render_component(&Blogex.Layout.index_page/1,
+      blog_title: @blog_title,
+      blog_description: @blog_description,
+      posts: posts,
+      base_path: @base_path,
+      page: Keyword.get(opts, :page, 1),
+      total_pages: Keyword.get(opts, :total_pages, 1)
+    )
+  end
+
+  defp render_show_page(post) do
+    render_component(&Blogex.Layout.show_page/1, post: post, base_path: @base_path)
+  end
+
+  defp render_tag_page(opts) do
+    render_component(&Blogex.Layout.tag_page/1,
+      blog_title: @blog_title,
+      tag: opts[:tag],
+      posts: opts[:posts],
+      base_path: @base_path
+    )
+  end
+end
diff --git a/blogex/test/blogex/router_test.exs b/blogex/test/blogex/router_test.exs
index 5b8813a..9600189 100644
--- a/blogex/test/blogex/router_test.exs
+++ b/blogex/test/blogex/router_test.exs
@@ -1,6 +1,7 @@
 defmodule Blogex.RouterTest do
   use ExUnit.Case
   import Plug.Test
+  import Plug.Conn, only: [put_req_header: 3]
 
   import Blogex.Test.PostBuilder
   alias Blogex.Test.FakeBlog
@@ -35,6 +36,18 @@ defmodule Blogex.RouterTest do
     |> Blogex.Router.call(Blogex.Router.init(blog: FakeBlog))
   end
 
+  defp call_html(path) do
+    conn(:get, path)
+    |> put_req_header("accept", "text/html")
+    |> Blogex.Router.call(Blogex.Router.init(blog: FakeBlog))
+  end
+
+  defp call_json(path) do
+    conn(:get, path)
+    |> put_req_header("accept", "application/json")
+    |> Blogex.Router.call(Blogex.Router.init(blog: FakeBlog))
+  end
+
   describe "GET /feed.xml" do
     test "returns RSS XML" do
       conn = call(:get, "/feed.xml")
@@ -153,6 +166,76 @@ defmodule Blogex.RouterTest do
     end
   end
 
+  # The browser arms were previously unexercised: every test above goes through
+  # `call/2`, which sends no Accept header, so `wants_html?/1` was always false.
+  describe "GET / (browser)" do
+    test "returns an HTML page with the blog title and the published posts" do
+      conn = call_html("/")
+
+      assert conn.status == 200
+      assert get_content_type(conn) =~ "text/html"
+      assert conn.resp_body =~ "Test Blog"
+      assert conn.resp_body =~ "First"
+      assert conn.resp_body =~ ~s(href="/blog/test/first-post")
+      refute conn.resp_body =~ "future-post"
+    end
+
+    test "leaves JSON clients alone" do
+      conn = call_json("/")
+
+      assert get_content_type(conn) =~ "application/json"
+      body = Jason.decode!(conn.resp_body)
+      assert body["title"] == "Test Blog"
+      assert body["total_entries"] == 2
+    end
+  end
+
+  describe "GET /:slug (browser)" do
+    test "returns the post as an HTML page" do
+      conn = call_html("/first-post")
+
+      assert conn.status == 200
+      assert get_content_type(conn) =~ "text/html"
+      assert conn.resp_body =~ "First"
+      assert conn.resp_body =~ "<p>Post body.</p>"
+      refute conn.resp_body =~ "&lt;p&gt;"
+    end
+
+    test "leaves JSON clients alone" do
+      conn = call_json("/first-post")
+
+      assert get_content_type(conn) =~ "application/json"
+      assert Jason.decode!(conn.resp_body)["id"] == "first-post"
+    end
+  end
+
+  describe "GET /tag/:tag (browser)" do
+    test "returns HTML with only the posts carrying that tag" do
+      conn = call_html("/tag/elixir")
+
+      assert conn.status == 200
+      assert get_content_type(conn) =~ "text/html"
+      assert conn.resp_body =~ "First"
+      refute conn.resp_body =~ "Second"
+    end
+
+    test "leaves JSON clients alone" do
+      conn = call_json("/tag/elixir")
+
+      assert get_content_type(conn) =~ "application/json"
+      assert Jason.decode!(conn.resp_body)["tag"] == "elixir"
+    end
+  end
+
+  describe "unknown routes" do
+    test "answers 404 Not found" do
+      conn = call(:post, "/whatever")
+
+      assert conn.status == 404
+      assert conn.resp_body == "Not found"
+    end
+  end
+
   describe "Helpers.base_url/1" do
     # `port_suffix/2` has one clause per (scheme, default port) pair plus the
     # catch-all, and the feeds embed this URL. All four shapes are pinned so a