diff --git a/lib/ex_doc/formatter/epub/templates.ex b/lib/ex_doc/formatter/epub/templates.ex
index 22dd483b8..ceb3d269e 100644
--- a/lib/ex_doc/formatter/epub/templates.ex
+++ b/lib/ex_doc/formatter/epub/templates.ex
@@ -13,14 +13,14 @@ defmodule ExDoc.Formatter.EPUB.Templates do
   defp render_doc(ast), do: ast && ExDoc.DocAST.to_string(ast)
 
   @doc """
-  Generate content from the module template for a given `node`
+  Generate content from the module template for a given `node`.
   """
   def module_page(config, module_node) do
     module_template(config, module_node)
   end
 
   @doc """
-  Generated ID for static file
+  Generated ID for static file.
   """
   def static_file_to_id(static_file) do
     static_file |> Path.basename() |> text_to_id()
diff --git a/lib/ex_doc/formatter/html/templates.ex b/lib/ex_doc/formatter/html/templates.ex
index 91c4ced07..ee7e9018a 100644
--- a/lib/ex_doc/formatter/html/templates.ex
+++ b/lib/ex_doc/formatter/html/templates.ex
@@ -13,7 +13,7 @@ defmodule ExDoc.Formatter.HTML.Templates do
     ]
 
   @doc """
-  Generate content from the module template for a given `node`
+  Generate content from the module template for a given `node`.
   """
   def module_page(module_node, config) do
     module_template(config, module_node)
diff --git a/lib/ex_doc/formatter/markdown.ex b/lib/ex_doc/formatter/markdown.ex
new file mode 100644
index 000000000..215b0569c
--- /dev/null
+++ b/lib/ex_doc/formatter/markdown.ex
@@ -0,0 +1,222 @@
+defmodule ExDoc.Formatter.MARKDOWN do
+  @moduledoc false
+
+  alias __MODULE__.{Templates}
+  alias ExDoc.Formatter
+  alias ExDoc.Utils
+
+  @doc """
+  Generates Markdown documentation for the given modules.
+  """
+  @spec run([ExDoc.ModuleNode.t()], [ExDoc.ModuleNode.t()], ExDoc.Config.t()) :: String.t()
+  def run(project_nodes, filtered_modules, config) when is_map(config) do
+    Utils.unset_warned()
+
+    config = normalize_config(config)
+
+    build = Path.join(config.output, ".build")
+    output_setup(build, config)
+
+    extras = Formatter.build_extras(config, ".md")
+
+    project_nodes =
+      project_nodes
+      |> Formatter.render_all(filtered_modules, ".md", config, highlight_tag: "samp")
+
+    nodes_map = %{
+      modules: Formatter.filter_list(:module, project_nodes),
+      tasks: Formatter.filter_list(:task, project_nodes)
+    }
+
+    config = %{config | extras: extras}
+
+    all_files =
+      [generate_nav(config, nodes_map)] ++
+        generate_extras(config) ++
+        generate_list(config, nodes_map.modules) ++
+        generate_list(config, nodes_map.tasks) ++
+        [generate_llm_index(config, nodes_map)]
+
+    generate_build(List.flatten(all_files), build)
+    config.output |> Path.join("index.md") |> Path.relative_to_cwd()
+  end
+
+  defp normalize_config(config) do
+    output = Path.expand(config.output)
+    %{config | output: output}
+  end
+
+  defp output_setup(build, config) do
+    if File.exists?(build) do
+      build
+      |> File.read!()
+      |> String.split("\n", trim: true)
+      |> Enum.map(&Path.join(config.output, &1))
+      |> Enum.each(&File.rm/1)
+
+      File.rm(build)
+    else
+      # Only remove markdown files, not HTML/EPUB files
+      File.mkdir_p!(config.output)
+
+      if File.exists?(config.output) do
+        config.output
+        |> Path.join("*.md")
+        |> Path.wildcard()
+        |> Enum.each(&File.rm/1)
+
+        llms_file = Path.join(config.output, "llms.txt")
+        if File.exists?(llms_file), do: File.rm(llms_file)
+      end
+    end
+  end
+
+  defp generate_build(files, build) do
+    entries =
+      files
+      |> Enum.uniq()
+      |> Enum.sort()
+      |> Enum.map(&[&1, "\n"])
+
+    File.mkdir_p!(Path.dirname(build))
+    File.write!(build, entries)
+  end
+
+  defp normalize_output(output) do
+    output
+    |> String.replace(~r/\r\n?/, "\n")
+    |> String.replace(~r/\n{3,}/, "\n\n")
+  end
+
+  defp generate_nav(config, nodes) do
+    nodes =
+      Map.update!(nodes, :modules, fn modules ->
+        modules |> Enum.chunk_by(& &1.group) |> Enum.map(&{hd(&1).group, &1})
+      end)
+
+    content =
+      Templates.nav_template(config, nodes)
+      |> normalize_output()
+
+    filename = "index.md"
+    File.write("#{config.output}/#{filename}", content)
+    filename
+  end
+
+  defp generate_extras(config) do
+    for {_title, extras} <- config.extras,
+        %{id: id, source: content} <- extras,
+        not is_map_key(%{id: id, source: content}, :url) do
+      filename = "#{id}.md"
+      output = "#{config.output}/#{filename}"
+
+      if File.regular?(output) do
+        Utils.warn("file #{Path.relative_to_cwd(output)} already exists", [])
+      end
+
+      File.write!(output, normalize_output(content))
+      filename
+    end
+  end
+
+  defp generate_list(config, nodes) do
+    nodes
+    |> Task.async_stream(&generate_module_page(&1, config), timeout: :infinity)
+    |> Enum.map(&elem(&1, 1))
+  end
+
+  ## Helpers
+
+  defp generate_module_page(module_node, config) do
+    content =
+      Templates.module_page(config, module_node)
+      |> normalize_output()
+
+    filename = "#{module_node.id}.md"
+    File.write("#{config.output}/#{filename}", content)
+    filename
+  end
+
+  defp generate_llm_index(config, nodes_map) do
+    content = generate_llm_index_content(config, nodes_map)
+    filename = "llms.txt"
+    File.write("#{config.output}/#{filename}", content)
+    filename
+  end
+
+  defp generate_llm_index_content(config, nodes_map) do
+    project_info = """
+    # #{config.project} #{config.version}
+
+    #{config.project} documentation index for Large Language Models.
+
+    ## Modules
+
+    """
+
+    modules_info =
+      nodes_map.modules
+      |> Enum.map(fn module_node ->
+        "- [#{module_node.title}](#{module_node.id}.md): #{module_node.doc |> ExDoc.DocAST.synopsis() |> extract_plain_text()}"
+      end)
+      |> Enum.join("\n")
+
+    tasks_info =
+      if length(nodes_map.tasks) > 0 do
+        tasks_list =
+          nodes_map.tasks
+          |> Enum.map(fn task_node ->
+            "- [#{task_node.title}](#{task_node.id}.md): #{task_node.doc |> ExDoc.DocAST.synopsis() |> extract_plain_text()}"
+          end)
+          |> Enum.join("\n")
+
+        "\n\n## Mix Tasks\n\n" <> tasks_list
+      else
+        ""
+      end
+
+    extras_info =
+      if is_list(config.extras) and length(config.extras) > 0 do
+        extras_list =
+          config.extras
+          |> Enum.flat_map(fn
+            {_group, extras} when is_list(extras) -> extras
+            _ -> []
+          end)
+          |> Enum.map(fn extra ->
+            "- [#{extra.title}](#{extra.id}.md)"
+          end)
+          |> Enum.join("\n")
+
+        if extras_list == "" do
+          ""
+        else
+          "\n\n## Guides\n\n" <> extras_list
+        end
+      else
+        ""
+      end
+
+    project_info <> modules_info <> tasks_info <> extras_info
+  end
+
+  defp extract_plain_text(html) when is_binary(html) do
+    html
+    |> String.replace(~r/<[^>]*>/, "")
+    |> String.replace(~r/\s+/, " ")
+    |> String.trim()
+    |> case do
+      "" ->
+        "No documentation available"
+
+      text ->
+        if String.length(text) > 150 do
+          String.slice(text, 0, 150) <> "..."
+        else
+          text
+        end
+    end
+  end
+
+  defp extract_plain_text(_), do: "No documentation available"
+end
diff --git a/lib/ex_doc/formatter/markdown/templates.ex b/lib/ex_doc/formatter/markdown/templates.ex
new file mode 100644
index 000000000..ed43583d0
--- /dev/null
+++ b/lib/ex_doc/formatter/markdown/templates.ex
@@ -0,0 +1,80 @@
+defmodule ExDoc.Formatter.MARKDOWN.Templates do
+  @moduledoc false
+
+  require EEx
+
+  import ExDoc.Utils,
+    only: [before_closing_body_tag: 2, h: 1]
+
+  @doc """
+  Generate content from the module template for a given `node`.
+  """
+  def module_page(config, module_node) do
+    docs =
+      for group <- module_node.docs_groups do
+        {group.title, group.docs}
+      end
+
+    module_template(config, module_node, docs)
+  end
+
+  @doc """
+  Formats the attribute type used to define the spec of the given `node`.
+  """
+  def format_spec_attribute(module, node) do
+    module.language.format_spec_attribute(node)
+  end
+
+  @doc """
+  Returns the original markdown documentation from source_doc.
+  """
+  def node_doc(%{source_doc: %{"en" => source}}) when is_binary(source), do: source
+  def node_doc(_), do: nil
+
+  @doc """
+  Creates a chapter which contains all the details about an individual module.
+  """
+  EEx.function_from_file(
+    :def,
+    :module_template,
+    Path.expand("templates/module_template.eex", __DIR__),
+    [:config, :module, :docs],
+    trim: true
+  )
+
+  @doc """
+  Creates the table of contents.
+  """
+  EEx.function_from_file(
+    :def,
+    :nav_template,
+    Path.expand("templates/nav_template.eex", __DIR__),
+    [:config, :nodes],
+    trim: true
+  )
+
+  EEx.function_from_file(
+    :defp,
+    :nav_item_template,
+    Path.expand("templates/nav_item_template.eex", __DIR__),
+    [:name, :nodes],
+    trim: true
+  )
+
+  EEx.function_from_file(
+    :defp,
+    :nav_grouped_item_template,
+    Path.expand("templates/nav_grouped_item_template.eex", __DIR__),
+    [:nodes],
+    trim: true
+  )
+
+  @doc false
+  EEx.function_from_file(
+    :def,
+    :detail_template,
+    Path.expand("templates/detail_template.eex", __DIR__),
+    [:node, :module],
+    trim: true
+  )
+end
diff --git a/lib/ex_doc/formatter/markdown/templates/detail_template.eex b/lib/ex_doc/formatter/markdown/templates/detail_template.eex
new file mode 100644
index 000000000..02534ca5a
--- /dev/null
+++ b/lib/ex_doc/formatter/markdown/templates/detail_template.eex
@@ -0,0 +1,15 @@
+# `<%= node.name %>`
+<%= if node.source_url do %>[🔗](<%= node.source_url %>)<% end %>
+
+<%= for annotation <- node.annotations do %>*<%= annotation %>* <% end %>
+<%= if deprecated = node.deprecated do %>
+> This <%= node.type %> is deprecated. <%= h(deprecated) %>.
+<% end %>
+<%= if node.specs != [] do %>
+<%= for spec <- node.specs do %>
+```elixir
+<%= format_spec_attribute(module, node) %> <%= spec %>
+```
+<% end %>
+<% end %>
+<%= node_doc(node) %>
diff --git a/lib/ex_doc/formatter/markdown/templates/module_template.eex b/lib/ex_doc/formatter/markdown/templates/module_template.eex
new file mode 100644
index 000000000..021f63812
--- /dev/null
+++ b/lib/ex_doc/formatter/markdown/templates/module_template.eex
@@ -0,0 +1,12 @@
+# `<%=h module.title %>`
+<%= if module.source_url do %>[🔗](<%= module.source_url %>)<% end %>
+
+<%= for annotation <- module.annotations do %>*<%= annotation %>* <% end %>
+<%= if deprecated = module.deprecated do %>
+> This <%= module.type %> is deprecated. <%=h deprecated %>.
+<% end %>
+<%= node_doc(module) %>
+<%= for {_name, nodes} <- docs, node <- nodes do %>
+<%= detail_template(node, module) %>
+<% end %>
+<%= before_closing_body_tag(config, :markdown) %>
diff --git a/lib/ex_doc/formatter/markdown/templates/nav_grouped_item_template.eex b/lib/ex_doc/formatter/markdown/templates/nav_grouped_item_template.eex
new file mode 100644
index 000000000..874ebdbfd
--- /dev/null
+++ b/lib/ex_doc/formatter/markdown/templates/nav_grouped_item_template.eex
@@ -0,0 +1,8 @@
+<%= for {title, nodes} <- nodes do %>
+<%= if title do %>
+- <%=h to_string(title) %>
+<% end %>
+<%= for node <- nodes do %>
+  - [<%=h node.title %>](<%= URI.encode node.id %>.md)
+<% end %>
+<% end %>
diff --git a/lib/ex_doc/formatter/markdown/templates/nav_item_template.eex b/lib/ex_doc/formatter/markdown/templates/nav_item_template.eex
new file mode 100644
index 000000000..449c46e22
--- /dev/null
+++ b/lib/ex_doc/formatter/markdown/templates/nav_item_template.eex
@@ -0,0 +1,6 @@
+<%= unless Enum.empty?(nodes) do %>
+- <%= name %>
+<%= for node <- nodes do %>
+  - [<%=h node.title %>](<%= URI.encode node.id %>.md)
+<% end %>
+<% end %>
diff --git a/lib/ex_doc/formatter/markdown/templates/nav_template.eex b/lib/ex_doc/formatter/markdown/templates/nav_template.eex
new file mode 100644
index 000000000..55434a410
--- /dev/null
+++ b/lib/ex_doc/formatter/markdown/templates/nav_template.eex
@@ -0,0 +1,9 @@
+# <%= config.project %> v<%= config.version %> - Documentation - Table of Contents
+
+<%= nav_grouped_item_template config.extras  %>
+<%= unless Enum.empty?(nodes.modules) do %>
+## Modules
+<%= nav_grouped_item_template nodes.modules  %>    
+<% end %>
+<%= nav_item_template "Mix Tasks", nodes.tasks %>
+<%= before_closing_body_tag(config, :markdown) %>
diff --git a/lib/mix/tasks/docs.ex b/lib/mix/tasks/docs.ex
index b6f03e7aa..29d571daf 100644
--- a/lib/mix/tasks/docs.ex
+++ b/lib/mix/tasks/docs.ex
@@ -12,9 +12,9 @@ defmodule Mix.Tasks.Docs do
     * `--canonical`, `-n` - Indicate the preferred URL with
       `rel="canonical"` link element, defaults to no canonical path
 
-    * `--formatter`, `-f` - Which formatters to use, `html` or
-      `epub`. This option can be given more than once. By default,
-      both `html` and `epub` are generated.
+    * `--formatter`, `-f` - Which formatters to use, `html`,
+      `epub`, or `markdown`. This option can be given more than once. By default,
+      `html`, `epub`, and `markdown` are generated.
 
     * `--language` - Specifies the language to annotate the
       EPUB output in valid [BCP 47](https://tools.ietf.org/html/bcp47)
@@ -130,7 +130,7 @@ defmodule Mix.Tasks.Docs do
       against the complete module name (which includes the "Elixir." prefix for
       Elixir modules). If a module has `@moduledoc false`, then it is always excluded.
 
-    * `:formatters` - Formatter to use; default: ["html", "epub"], options: "html", "epub".
+    * `:formatters` - Formatter to use; default: ["html", "epub", "markdown"], options: "html", "epub", "markdown".
 
     * `:footer` - When false, does not render the footer on all pages, except for
       the required "Built with ExDoc" note.
@@ -611,7 +611,12 @@ defmodule Mix.Tasks.Docs do
 
     results =
       for formatter <- options[:formatters] do
-        index = generator.(project, version, Keyword.put(options, :formatter, formatter))
+        formatter_options =
+          options
+          |> Keyword.put(:formatter, formatter)
+          |> update_output_for_formatter(formatter)
+
+        index = generator.(project, version, formatter_options)
         Mix.shell().info([:green, "View #{inspect(formatter)} docs at #{inspect(index)}"])
 
         if cli_opts[:open] do
@@ -650,13 +655,23 @@ defmodule Mix.Tasks.Docs do
   defp normalize_formatters(options) do
     formatters =
       case Keyword.get_values(options, :formatter) do
-        [] -> options[:formatters] || ["html", "epub"]
+        [] -> options[:formatters] || ["html", "epub", "markdown"]
         values -> values
       end
 
     Keyword.put(options, :formatters, formatters)
   end
 
+  defp update_output_for_formatter(options, "markdown") do
+    output = options[:output] || "doc"
+    Keyword.put(options, :output, Path.join(output, "markdown"))
+  end
+
+  defp update_output_for_formatter(options, _formatter) do
+    output = options[:output] || "doc"
+    Keyword.put(options, :output, output)
+  end
+
   defp get_docs_opts(config) do
     docs = config[:docs]
 
diff --git a/test/ex_doc/formatter/markdown_test.exs b/test/ex_doc/formatter/markdown_test.exs
new file mode 100644
index 000000000..6c437684a
--- /dev/null
+++ b/test/ex_doc/formatter/markdown_test.exs
@@ -0,0 +1,362 @@
+defmodule ExDoc.Formatter.MarkdownTest do
+  use ExUnit.Case, async: false
+
+  @moduletag :tmp_dir
+
+  defp doc_config(%{tmp_dir: tmp_dir} = _context) do
+    [
+      project: "Elixir",
+      version: "1.0.1",
+      formatter: "markdown",
+      output: tmp_dir,
+      source_beam: "test/tmp/beam",
+      skip_undefined_reference_warnings_on: ["Warnings"]
+    ]
+  end
+
+  defp doc_config(context, config) when is_map(context) and is_list(config) do
+    Keyword.merge(doc_config(context), config)
+  end
+
+  defp generate_docs(config) do
+    ExDoc.generate_docs(config[:project], config[:version], config)
+  end
+
+  test "generates Markdown files in the default directory", %{tmp_dir: tmp_dir} = context do
+    generate_docs(doc_config(context))
+    assert File.regular?(tmp_dir <> "/index.md")
+    assert File.regular?(tmp_dir <> "/CompiledWithDocs.md")
+  end
+
+  test "generates headers for module pages", %{tmp_dir: tmp_dir} = context do
+    generate_docs(doc_config(context, main: "RandomError"))
+
+    content = File.read!(tmp_dir <> "/RandomError.md")
+    assert content =~ ~r{^# `RandomError`}m
+  end
+
+  test "generates all listing files", %{tmp_dir: tmp_dir} = context do
+    generate_docs(doc_config(context))
+
+    assert File.regular?(tmp_dir <> "/CompiledWithDocs.md")
+    assert File.regular?(tmp_dir <> "/CompiledWithDocs.Nested.md")
+    assert File.regular?(tmp_dir <> "/CustomBehaviourOne.md")
+    assert File.regular?(tmp_dir <> "/CustomBehaviourTwo.md")
+    assert File.regular?(tmp_dir <> "/RandomError.md")
+    assert File.regular?(tmp_dir <> "/CustomProtocol.md")
+    assert File.regular?(tmp_dir <> "/Mix.Tasks.TaskWithDocs.md")
+  end
+
+  test "generates the index file", %{tmp_dir: tmp_dir} = context do
+    generate_docs(doc_config(context))
+
+    content = File.read!(tmp_dir <> "/index.md")
+    assert content =~ ~r{^# Elixir v1\.0\.1 - Documentation - Table of Contents$}m
+    assert content =~ ~r{## Modules}
+    assert content =~ ~r{- \[CompiledWithDocs\]\(CompiledWithDocs\.md\)}
+    assert content =~ ~r{- \[CompiledWithDocs\.Nested\]\(CompiledWithDocs\.Nested\.md\)}
+  end
+
+  test "generates module with proper structure", %{tmp_dir: tmp_dir} = context do
+    generate_docs(doc_config(context))
+
+    content = File.read!(tmp_dir <> "/CompiledWithDocs.md")
+
+    # Header
+    assert content =~ ~r{^# `CompiledWithDocs`}m
+    assert content =~ ~r{\*example_module_tag\*}
+
+    # Moduledoc
+    assert content =~ ~r{moduledoc}
+  end
+
+  test "generates functions correctly", %{tmp_dir: tmp_dir} = context do
+    generate_docs(doc_config(context))
+
+    content = File.read!(tmp_dir <> "/CompiledWithDocs.md")
+
+    # Function header
+    assert content =~ ~r{^# `example`$}m
+
+    # Function documentation
+    assert content =~ ~r{Some example}
+
+    # Deprecated notice
+    assert content =~ ~r{> This function is deprecated\. Use something else instead\.}
+
+    # Struct
+    assert content =~ ~r{^# `__struct__`$}m
+    assert content =~ ~r{Some struct}
+
+    # Since annotation
+    assert content =~ ~r{^# `example_1`$}m
+    assert content =~ ~r{\*since 1\.3\.0\*}
+
+    # Macro annotation
+    assert content =~ ~r{\*macro\*}
+  end
+
+  describe "generates extras" do
+    test "ignores any external url extras", %{tmp_dir: tmp_dir} = context do
+      config =
+        context
+        |> doc_config()
+        |> Keyword.put(:extras, elixir: [url: "https://elixir-lang.org"])
+
+      generate_docs(config)
+
+      refute File.exists?(tmp_dir <> "/elixir.md")
+    end
+  end
+
+  test "generates LLM index file", %{tmp_dir: tmp_dir} = context do
+    generate_docs(doc_config(context))
+
+    content = File.read!(tmp_dir <> "/llms.txt")
+
+    assert content =~ ~r{# Elixir 1\.0\.1}
+    assert content =~ ~r{Elixir documentation index for Large Language Models}
+    assert content =~ ~r{## Modules}
+    assert content =~ ~r{- \[CompiledWithDocs\]\(CompiledWithDocs\.md\):}
+  end
+
+  describe "markdown output validation" do
+    test "generates proper markdown syntax", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+      content = File.read!(tmp_dir <> "/CompiledWithDocs.md")
+
+      # Module header with backticks
+      assert content =~ ~r/^# `CompiledWithDocs`/m
+      # Function headers with backticks
+      assert content =~ ~r/^# `[a-z_]+`$/m
+    end
+
+    test "handles complex documentation elements", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+      content = File.read!(tmp_dir <> "/CompiledWithDocs.md")
+
+      # Function header format with backticks
+      assert content =~ ~r/^# `example`$/m
+      # Deprecated notice
+      assert content =~ ~r/> This function is deprecated\./
+    end
+
+    test "generates valid navigation structure", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+      content = File.read!(tmp_dir <> "/index.md")
+
+      assert content =~ ~r/^# Elixir v1\.0\.1 - Documentation - Table of Contents$/m
+      assert content =~ ~r/- \[CompiledWithDocs\]\(CompiledWithDocs\.md\)/
+      assert content =~ ~r/- \[CompiledWithDocs\.Nested\]\(CompiledWithDocs\.Nested\.md\)/
+      assert content =~ ~r/- \[mix task_with_docs\]\(Mix\.Tasks\.TaskWithDocs\.md\)/
+      refute content =~ ~r/\]\([^)]*\s[^)]*\)/
+      refute content =~ ~r/\[[^\]]*\]\(\)/
+    end
+
+    test "generates proper markdown escaping", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+      content = File.read!(tmp_dir <> "/CompiledWithDocs.md")
+
+      assert content =~ ~r/&lt;|&gt;|&amp;/ || !String.contains?(content, "<script>")
+    end
+  end
+
+  describe "configuration options" do
+    test "handles custom output directory", %{tmp_dir: tmp_dir} = context do
+      custom_output = Path.join(tmp_dir, "custom_docs")
+      config = doc_config(context, output: custom_output)
+      generate_docs(config)
+
+      assert File.regular?(custom_output <> "/index.md")
+      assert File.regular?(custom_output <> "/CompiledWithDocs.md")
+      refute File.exists?(tmp_dir <> "/index.md")
+    end
+
+    test "handles custom project name and version", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, project: "MyProject", version: "2.0.0")
+      generate_docs(config)
+
+      content = File.read!(tmp_dir <> "/index.md")
+      assert content =~ ~r/# MyProject v2\.0\.0 - Documentation/
+
+      llm_content = File.read!(tmp_dir <> "/llms.txt")
+      assert llm_content =~ ~r/# MyProject 2\.0\.0/
+    end
+
+    test "processes source_url configuration", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, source_url: "https://github.com/example/project")
+      generate_docs(config)
+
+      assert File.regular?(tmp_dir <> "/CompiledWithDocs.md")
+      assert File.regular?(tmp_dir <> "/index.md")
+    end
+  end
+
+  describe "extras handling" do
+    test "processes markdown extras correctly", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, extras: ["test/fixtures/README.md"])
+      generate_docs(config)
+
+      assert File.regular?(tmp_dir <> "/index.md")
+      nav_content = File.read!(tmp_dir <> "/index.md")
+      assert nav_content =~ ~r/## Modules/
+      assert File.regular?(tmp_dir <> "/llms.txt")
+    end
+
+    test "handles multiple extras with custom names", %{tmp_dir: tmp_dir} = context do
+      config =
+        doc_config(context,
+          extras: [
+            "test/fixtures/README.md",
+            {"test/fixtures/LICENSE", filename: "license-file"}
+          ]
+        )
+
+      generate_docs(config)
+
+      assert File.regular?(tmp_dir <> "/index.md")
+      assert File.regular?(tmp_dir <> "/llms.txt")
+    end
+
+    test "processes plain text files as extras", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, extras: ["test/fixtures/PlainText.txt"])
+      generate_docs(config)
+
+      assert File.regular?(tmp_dir <> "/index.md")
+    end
+
+    test "handles extras with custom titles", %{tmp_dir: tmp_dir} = context do
+      config =
+        doc_config(context,
+          extras: [
+            {"test/fixtures/README.md", title: "Getting Started"}
+          ]
+        )
+
+      generate_docs(config)
+
+      assert File.regular?(tmp_dir <> "/index.md")
+      assert File.regular?(tmp_dir <> "/llms.txt")
+    end
+
+    test "ignores external url extras", %{tmp_dir: tmp_dir} = context do
+      config =
+        doc_config(context,
+          extras: [
+            "test/fixtures/README.md",
+            elixir: [url: "https://elixir-lang.org"]
+          ]
+        )
+
+      generate_docs(config)
+
+      refute File.exists?(tmp_dir <> "/elixir.md")
+      assert File.regular?(tmp_dir <> "/index.md")
+    end
+  end
+
+  describe "error scenarios" do
+    test "handles modules with no documentation gracefully", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+
+      assert File.regular?(tmp_dir <> "/CompiledWithoutDocs.md")
+
+      content = File.read!(tmp_dir <> "/CompiledWithoutDocs.md")
+      assert content =~ ~r/^# `CompiledWithoutDocs`/m
+    end
+
+    test "handles missing source beam directory", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, source_beam: "nonexistent/path")
+
+      generate_docs(config)
+      assert File.regular?(tmp_dir <> "/index.md")
+    end
+
+    test "handles empty extras list", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, extras: [])
+      generate_docs(config)
+
+      nav_content = File.read!(tmp_dir <> "/index.md")
+      refute nav_content =~ ~r/## Guides/
+
+      llm_content = File.read!(tmp_dir <> "/llms.txt")
+      refute llm_content =~ ~r/## Guides/
+    end
+
+    test "handles special characters in module names", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+
+      assert File.regular?(tmp_dir <> "/CompiledWithDocs.Nested.md")
+
+      content = File.read!(tmp_dir <> "/CompiledWithDocs.Nested.md")
+      assert content =~ ~r/^# `CompiledWithDocs\.Nested`/m
+    end
+  end
+
+  describe "llm index comprehensive tests" do
+    test "creates comprehensive llm index with all sections", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, extras: ["test/fixtures/README.md"])
+      generate_docs(config)
+
+      content = File.read!(tmp_dir <> "/llms.txt")
+
+      assert content =~ ~r/# Elixir 1\.0\.1/
+      assert content =~ ~r/documentation index for Large Language Models/
+
+      assert content =~ ~r/## Modules/
+      assert content =~ ~r/- \[CompiledWithDocs\]\(CompiledWithDocs\.md\):/
+      assert content =~ ~r/- \[CustomBehaviourOne\]/
+
+      assert content =~ ~r/## Mix Tasks/
+      assert content =~ ~r/- \[mix task_with_docs\]/
+    end
+
+    test "handles llm index when no tasks exist", %{tmp_dir: tmp_dir} = context do
+      config = doc_config(context, source_beam: "test/fixtures/beam_no_tasks")
+      generate_docs(config)
+
+      content = File.read!(tmp_dir <> "/llms.txt")
+
+      assert content =~ ~r/## Modules/
+    end
+
+    test "truncates long descriptions in llm index", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+
+      content = File.read!(tmp_dir <> "/llms.txt")
+
+      lines = String.split(content, "\n")
+      module_lines = Enum.filter(lines, &String.starts_with?(&1, "- ["))
+
+      for line <- module_lines do
+        assert String.length(line) < 300
+      end
+    end
+  end
+
+  describe "output normalization" do
+    test "normalizes line endings consistently", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+      content = File.read!(tmp_dir <> "/CompiledWithDocs.md")
+
+      refute String.contains?(content, "\r\n")
+      refute String.contains?(content, "\r")
+
+      refute String.contains?(content, "\n\n\n\n")
+    end
+
+    test "handles unicode content properly", %{tmp_dir: tmp_dir} = context do
+      generate_docs(doc_config(context))
+
+      files = [
+        tmp_dir <> "/index.md",
+        tmp_dir <> "/CompiledWithDocs.md"
+      ]
+
+      for file <- files do
+        content = File.read!(file)
+        assert String.valid?(content)
+      end
+    end
+  end
+end
diff --git a/test/mix/tasks/docs_test.exs b/test/mix/tasks/docs_test.exs
index 6019b62a0..2ce9730d8 100644
--- a/test/mix/tasks/docs_test.exs
+++ b/test/mix/tasks/docs_test.exs
@@ -27,8 +27,9 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "0.1.0",
               [
+                output: _,
                 formatter: "html",
-                formatters: ["html", "epub"],
+                formatters: ["html", "epub", "markdown"],
                 deps: _,
                 apps: _,
                 source_beam: _,
@@ -36,8 +37,19 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "0.1.0",
               [
+                output: _,
                 formatter: "epub",
-                formatters: ["html", "epub"],
+                formatters: ["html", "epub", "markdown"],
+                deps: _,
+                apps: _,
+                source_beam: _,
+                proglang: :elixir
+              ]},
+             {"ex_doc", "0.1.0",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: ["html", "epub", "markdown"],
                 deps: _,
                 apps: _,
                 source_beam: _,
@@ -50,6 +62,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "0.1.0",
               [
+                output: _,
                 formatter: "html",
                 formatters: ["html", "epub"],
                 deps: _,
@@ -59,6 +72,7 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "0.1.0",
               [
+                output: _,
                 formatter: "epub",
                 formatters: ["html", "epub"],
                 deps: _,
@@ -73,6 +87,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "0.1.0",
               [
+                output: _,
                 formatter: "html",
                 formatters: ["html", "epub"],
                 deps: _,
@@ -82,6 +97,7 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "0.1.0",
               [
+                output: _,
                 formatter: "epub",
                 formatters: ["html", "epub"],
                 deps: _,
@@ -101,6 +117,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ExDoc", "0.1.0",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: _,
@@ -110,12 +127,23 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ExDoc", "0.1.0",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: _,
                 apps: _,
                 source_beam: _,
                 proglang: :elixir
+              ]},
+             {"ExDoc", "0.1.0",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: _,
+                apps: _,
+                source_beam: _,
+                proglang: :elixir
               ]}
            ] = run(context, [], app: :ex_doc, version: "0.1.0", name: "ExDoc")
   end
@@ -124,6 +152,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: _,
@@ -134,6 +163,7 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: _,
@@ -141,6 +171,17 @@ defmodule Mix.Tasks.DocsTest do
                 apps: _,
                 source_beam: _,
                 proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: _,
+                main: "Sample",
+                apps: _,
+                source_beam: _,
+                proglang: :elixir
               ]}
            ] = run(context, [], app: :ex_doc, docs: [main: Sample])
   end
@@ -149,6 +190,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: _,
@@ -159,6 +201,7 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: _,
@@ -166,78 +209,112 @@ defmodule Mix.Tasks.DocsTest do
                 source_beam: _,
                 main: "another",
                 proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: _,
+                apps: _,
+                source_beam: _,
+                main: "another",
+                proglang: :elixir
               ]}
            ] = run(context, [], app: :ex_doc, docs: [main: "another"])
   end
 
   test "accepts output in :output", %{tmp_dir: tmp_dir} = context do
-    [{_, _, html_options}, {_, _, epub_options}] =
+    [{_, _, html_options}, {_, _, epub_options}, {_, _, markdown_options}] =
       run_results = run(context, [], app: :ex_doc, docs: [output: tmp_dir <> "/hello"])
 
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: _,
                 apps: _,
                 source_beam: _,
-                output: _,
                 proglang: :elixir
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: _,
                 apps: _,
                 source_beam: _,
+                proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
                 output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: _,
+                apps: _,
+                source_beam: _,
                 proglang: :elixir
               ]}
            ] = run_results
 
     assert html_options[:output] == "#{tmp_dir}/hello"
     assert epub_options[:output] == "#{tmp_dir}/hello"
+    assert markdown_options[:output] == "#{tmp_dir}/hello/markdown"
   end
 
   test "parses output with lower preference than options", %{tmp_dir: tmp_dir} = context do
     output = tmp_dir <> "/world"
 
-    [{_, _, html_options}, {_, _, epub_options}] =
+    [{_, _, html_options}, {_, _, epub_options}, {_, _, markdown_options}] =
       run_results = run(context, ["-o", "#{output}"], app: :ex_doc, docs: [output: output])
 
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: _,
                 apps: _,
                 source_beam: _,
-                output: _,
                 proglang: :elixir
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: _,
                 apps: _,
                 source_beam: _,
+                proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
                 output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: _,
+                apps: _,
+                source_beam: _,
                 proglang: :elixir
               ]}
            ] = run_results
 
     assert html_options[:output] == "#{tmp_dir}/world"
     assert epub_options[:output] == "#{tmp_dir}/world"
+    assert markdown_options[:output] == "#{tmp_dir}/world/markdown"
   end
 
   test "includes dependencies", context do
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: deps,
@@ -247,12 +324,23 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: deps,
                 apps: _,
                 source_beam: _,
                 proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: deps,
+                apps: _,
+                source_beam: _,
+                proglang: :elixir
               ]}
            ] = run(context, [], app: :ex_doc, docs: [])
 
@@ -265,6 +353,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: deps,
@@ -274,12 +363,23 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: deps,
                 apps: _,
                 source_beam: _,
                 proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: deps,
+                apps: _,
+                source_beam: _,
+                proglang: :elixir
               ]}
            ] = run(context, [], app: :ex_doc, docs: [deps: [earmark_parser: "foo"]])
 
@@ -291,6 +391,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: _,
@@ -301,6 +402,7 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: _,
@@ -308,6 +410,17 @@ defmodule Mix.Tasks.DocsTest do
                 source_beam: _,
                 main: "another",
                 proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: _,
+                apps: _,
+                source_beam: _,
+                main: "another",
+                proglang: :elixir
               ]}
            ] = run(context, [], app: :ex_doc, docs: fn -> [main: "another"] end)
   end
@@ -317,6 +430,7 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ExDoc", "1.2.3-dev",
               [
+                output: _,
                 formatter: "html",
                 formatters: _,
                 deps: _,
@@ -328,6 +442,7 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ExDoc", "1.2.3-dev",
               [
+                output: _,
                 formatter: "epub",
                 formatters: _,
                 deps: _,
@@ -336,6 +451,18 @@ defmodule Mix.Tasks.DocsTest do
                 homepage_url: "https://elixir-lang.org",
                 source_url: "https://github.com/elixir-lang/ex_doc",
                 proglang: :elixir
+              ]},
+             {"ExDoc", "1.2.3-dev",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: _,
+                deps: _,
+                apps: _,
+                source_beam: _,
+                homepage_url: "https://elixir-lang.org",
+                source_url: "https://github.com/elixir-lang/ex_doc",
+                proglang: :elixir
               ]}
            ] =
              run(context, [],
@@ -347,7 +474,8 @@ defmodule Mix.Tasks.DocsTest do
                proglang: :elixir
              )
 
-    assert [{"ex_doc", "dev", _}, {"ex_doc", "dev", _}] = run(context, [], app: :ex_doc)
+    assert [{"ex_doc", "dev", _}, {"ex_doc", "dev", _}, {"ex_doc", "dev", _}] =
+             run(context, [], app: :ex_doc)
   end
 
   test "supports umbrella project", context do
@@ -355,6 +483,7 @@ defmodule Mix.Tasks.DocsTest do
       assert [
                {"umbrella", "dev",
                 [
+                  output: _,
                   formatter: "html",
                   formatters: _,
                   deps: _,
@@ -364,12 +493,23 @@ defmodule Mix.Tasks.DocsTest do
                 ]},
                {"umbrella", "dev",
                 [
+                  output: _,
                   formatter: "epub",
                   formatters: _,
                   deps: _,
                   apps: [:bar, :foo],
                   source_beam: _,
                   proglang: :elixir
+                ]},
+               {"umbrella", "dev",
+                [
+                  output: _,
+                  formatter: "markdown",
+                  formatters: _,
+                  deps: _,
+                  apps: [:bar, :foo],
+                  source_beam: _,
+                  proglang: :elixir
                 ]}
              ] = run(context, [], app: :umbrella, apps_path: "apps/", docs: [])
     end)
@@ -380,6 +520,7 @@ defmodule Mix.Tasks.DocsTest do
       assert [
                {"umbrella", "dev",
                 [
+                  output: _,
                   formatter: "html",
                   formatters: _,
                   deps: _,
@@ -390,6 +531,7 @@ defmodule Mix.Tasks.DocsTest do
                 ]},
                {"umbrella", "dev",
                 [
+                  output: _,
                   formatter: "epub",
                   formatters: _,
                   deps: _,
@@ -397,6 +539,17 @@ defmodule Mix.Tasks.DocsTest do
                   source_beam: _,
                   ignore_apps: [:foo],
                   proglang: :elixir
+                ]},
+               {"umbrella", "dev",
+                [
+                  output: _,
+                  formatter: "markdown",
+                  formatters: _,
+                  deps: _,
+                  apps: [:bar],
+                  source_beam: _,
+                  ignore_apps: [:foo],
+                  proglang: :elixir
                 ]}
              ] = run(context, [], app: :umbrella, apps_path: "apps/", docs: [ignore_apps: [:foo]])
     end)
@@ -406,8 +559,9 @@ defmodule Mix.Tasks.DocsTest do
     assert [
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "html",
-                formatters: ["html", "epub"],
+                formatters: ["html", "epub", "markdown"],
                 deps: _,
                 apps: [:ex_doc],
                 source_beam: _,
@@ -416,8 +570,20 @@ defmodule Mix.Tasks.DocsTest do
               ]},
              {"ex_doc", "dev",
               [
+                output: _,
                 formatter: "epub",
-                formatters: ["html", "epub"],
+                formatters: ["html", "epub", "markdown"],
+                deps: _,
+                apps: [:ex_doc],
+                source_beam: _,
+                warnings_as_errors: false,
+                proglang: :elixir
+              ]},
+             {"ex_doc", "dev",
+              [
+                output: _,
+                formatter: "markdown",
+                formatters: ["html", "epub", "markdown"],
                 deps: _,
                 apps: [:ex_doc],
                 source_beam: _,