diff --git a/README.md b/README.md
index ad71f22..80ffa3f 100644
--- a/README.md
+++ b/README.md
@@ -135,7 +135,7 @@ In `prod`, these environment variables are used:
 - `DATABASE_URL` (**required**), e.g. `ecto://USER:PASS@HOST/parrhesia_prod`
 - `POOL_SIZE` (optional, default `32`)
 - `PORT` (optional, default `4413`)
-- `PARRHESIA_*` runtime overrides for relay config, identity, sync, ACL, limits, policies, listeners, retention, and features
+- `PARRHESIA_*` runtime overrides for relay config, metadata, identity, sync, ACL, limits, policies, listeners, retention, and features
 - `PARRHESIA_EXTRA_CONFIG` (optional path to an extra runtime config file)
 
 `config/runtime.exs` reads these values at runtime in production releases.
@@ -145,6 +145,7 @@ In `prod`, these environment variables are used:
 For runtime overrides, use the `PARRHESIA_...` prefix:
 
 - `PARRHESIA_RELAY_URL`
+- `PARRHESIA_METADATA_HIDE_VERSION`
 - `PARRHESIA_IDENTITY_*`
 - `PARRHESIA_SYNC_*`
 - `PARRHESIA_ACL_*`
@@ -181,6 +182,7 @@ CSV env vars use comma-separated values. Boolean env vars accept `1/0`, `true/fa
 | Atom key | ENV | Default | Notes |
 | --- | --- | --- | --- |
 | `:relay_url` | `PARRHESIA_RELAY_URL` | `ws://localhost:4413/relay` | Advertised relay URL and auth relay tag target |
+| `:metadata.hide_version?` | `PARRHESIA_METADATA_HIDE_VERSION` | `true` | Hides the relay version from outbound `User-Agent` and NIP-11 when enabled |
 | `:acl.protected_filters` | `PARRHESIA_ACL_PROTECTED_FILTERS` | `[]` | JSON-encoded protected filter list for sync ACL checks |
 | `:identity.path` | `PARRHESIA_IDENTITY_PATH` | `nil` | Optional path for persisted relay identity material |
 | `:identity.private_key` | `PARRHESIA_IDENTITY_PRIVATE_KEY` | `nil` | Optional inline relay private key |
diff --git a/config/config.exs b/config/config.exs
index 5d93cae..3c82952 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -1,8 +1,19 @@
 import Config
 
+project_version =
+  case Mix.Project.config()[:version] do
+    version when is_binary(version) -> version
+    version -> to_string(version)
+  end
+
 config :postgrex, :json_library, JSON
 
 config :parrhesia,
+  metadata: [
+    name: "Parrhesia",
+    version: project_version,
+    hide_version?: true
+  ],
   database: [
     separate_read_pool?: config_env() != :test
   ],
diff --git a/config/runtime.exs b/config/runtime.exs
index 7932fcb..63372ef 100644
--- a/config/runtime.exs
+++ b/config/runtime.exs
@@ -132,6 +132,7 @@ if config_env() == :prod do
   repo_defaults = Application.get_env(:parrhesia, Parrhesia.Repo, [])
   read_repo_defaults = Application.get_env(:parrhesia, Parrhesia.ReadRepo, [])
   relay_url_default = Application.get_env(:parrhesia, :relay_url)
+  metadata_defaults = Application.get_env(:parrhesia, :metadata, [])
 
   moderation_cache_enabled_default =
     Application.get_env(:parrhesia, :moderation_cache_enabled, true)
@@ -646,6 +647,15 @@ if config_env() == :prod do
 
   config :parrhesia,
     relay_url: string_env.("PARRHESIA_RELAY_URL", relay_url_default),
+    metadata: [
+      name: Keyword.get(metadata_defaults, :name, "Parrhesia"),
+      version: Keyword.get(metadata_defaults, :version, "0.0.0"),
+      hide_version?:
+        bool_env.(
+          "PARRHESIA_METADATA_HIDE_VERSION",
+          Keyword.get(metadata_defaults, :hide_version?, true)
+        )
+    ],
     acl: [
       protected_filters:
         json_env.(
diff --git a/lib/parrhesia/http.ex b/lib/parrhesia/http.ex
new file mode 100644
index 0000000..a8dcdd7
--- /dev/null
+++ b/lib/parrhesia/http.ex
@@ -0,0 +1,48 @@
+defmodule Parrhesia.HTTP do
+  @moduledoc false
+
+  alias Parrhesia.Metadata
+
+  @default_headers [{"user-agent", Metadata.user_agent()}]
+
+  @spec default_headers() :: [{String.t(), String.t()}]
+  def default_headers, do: @default_headers
+
+  @spec get(Keyword.t()) :: {:ok, Req.Response.t()} | {:error, Exception.t()}
+  def get(options) when is_list(options) do
+    Req.get(put_default_headers(options))
+  end
+
+  @spec post(Keyword.t()) :: {:ok, Req.Response.t()} | {:error, Exception.t()}
+  def post(options) when is_list(options) do
+    Req.post(put_default_headers(options))
+  end
+
+  @spec put_default_headers(Keyword.t()) :: Keyword.t()
+  def put_default_headers(options) when is_list(options) do
+    Keyword.update(options, :headers, @default_headers, &merge_headers(&1, @default_headers))
+  end
+
+  defp merge_headers(headers, defaults) do
+    existing_names =
+      headers
+      |> List.wrap()
+      |> Enum.reduce(MapSet.new(), fn
+        {name, _value}, acc -> MapSet.put(acc, normalize_header_name(name))
+        _other, acc -> acc
+      end)
+
+    headers ++
+      Enum.reject(defaults, fn {name, _value} ->
+        MapSet.member?(existing_names, normalize_header_name(name))
+      end)
+  end
+
+  defp normalize_header_name(name) when is_atom(name) do
+    name
+    |> Atom.to_string()
+    |> String.downcase()
+  end
+
+  defp normalize_header_name(name) when is_binary(name), do: String.downcase(name)
+end
diff --git a/lib/parrhesia/metadata.ex b/lib/parrhesia/metadata.ex
new file mode 100644
index 0000000..4e66d7a
--- /dev/null
+++ b/lib/parrhesia/metadata.ex
@@ -0,0 +1,29 @@
+defmodule Parrhesia.Metadata do
+  @moduledoc false
+
+  @metadata Application.compile_env(:parrhesia, :metadata, [])
+  @name Keyword.get(@metadata, :name, "Parrhesia")
+  @version Keyword.get(@metadata, :version, "0.0.0")
+  @hide_version? Keyword.get(@metadata, :hide_version?, true)
+
+  @spec name() :: String.t()
+  def name, do: @name
+
+  @spec version() :: String.t()
+  def version, do: @version
+
+  @spec hide_version?() :: boolean()
+  def hide_version?, do: @hide_version?
+
+  @spec name_and_version() :: String.t()
+  def name_and_version, do: "#{@name}/#{@version}"
+
+  @spec user_agent() :: String.t()
+  def user_agent do
+    if hide_version?() do
+      name()
+    else
+      name_and_version()
+    end
+  end
+end
diff --git a/lib/parrhesia/nip66/probe.ex b/lib/parrhesia/nip66/probe.ex
index 5435ad4..65b1df7 100644
--- a/lib/parrhesia/nip66/probe.ex
+++ b/lib/parrhesia/nip66/probe.ex
@@ -1,6 +1,7 @@
 defmodule Parrhesia.NIP66.Probe do
   @moduledoc false
 
+  alias Parrhesia.HTTP
   alias Parrhesia.Sync.Transport.WebSockexClient
 
   @type result :: %{
@@ -145,7 +146,7 @@ defmodule Parrhesia.NIP66.Probe do
   defp fetch_nip11(relay_url, timeout_ms) do
     started_at = System.monotonic_time()
 
-    case Req.get(
+    case HTTP.get(
            url: relay_info_url(relay_url),
            headers: [{"accept", "application/nostr+json"}],
            decode_body: false,
diff --git a/lib/parrhesia/sync/relay_info_client.ex b/lib/parrhesia/sync/relay_info_client.ex
index e9d651d..b5cb51b 100644
--- a/lib/parrhesia/sync/relay_info_client.ex
+++ b/lib/parrhesia/sync/relay_info_client.ex
@@ -1,6 +1,7 @@
 defmodule Parrhesia.Sync.RelayInfoClient do
   @moduledoc false
 
+  alias Parrhesia.HTTP
   alias Parrhesia.Sync.TLS
 
   @spec verify_remote_identity(map(), keyword()) :: :ok | {:error, term()}
@@ -18,7 +19,7 @@ defmodule Parrhesia.Sync.RelayInfoClient do
   end
 
   defp default_request(url, opts) do
-    case Req.get(
+    case HTTP.get(
            url: url,
            headers: [{"accept", "application/nostr+json"}],
            decode_body: false,
diff --git a/lib/parrhesia/web/relay_info.ex b/lib/parrhesia/web/relay_info.ex
index 683e279..0113da6 100644
--- a/lib/parrhesia/web/relay_info.ex
+++ b/lib/parrhesia/web/relay_info.ex
@@ -4,21 +4,27 @@ defmodule Parrhesia.Web.RelayInfo do
   """
 
   alias Parrhesia.API.Identity
+  alias Parrhesia.Metadata
   alias Parrhesia.NIP43
   alias Parrhesia.Web.Listener
 
   @spec document(Listener.t()) :: map()
   def document(listener) do
-    %{
-      "name" => "Parrhesia",
+    document = %{
+      "name" => Metadata.name(),
       "description" => "Nostr/Marmot relay",
       "pubkey" => relay_pubkey(),
       "self" => relay_pubkey(),
       "supported_nips" => supported_nips(),
       "software" => "https://git.teralink.net/self/parrhesia",
-      "version" => Application.spec(:parrhesia, :vsn) |> to_string(),
       "limitation" => limitations(listener)
     }
+
+    if Metadata.hide_version?() do
+      document
+    else
+      Map.put(document, "version", Metadata.version())
+    end
   end
 
   defp supported_nips do
diff --git a/test/parrhesia/config_test.exs b/test/parrhesia/config_test.exs
index e6342ef..c20af95 100644
--- a/test/parrhesia/config_test.exs
+++ b/test/parrhesia/config_test.exs
@@ -4,6 +4,9 @@ defmodule Parrhesia.ConfigTest do
   alias Parrhesia.Web.Listener
 
   test "returns configured relay limits/policies/features" do
+    assert Parrhesia.Config.get([:metadata, :name]) == "Parrhesia"
+    assert Parrhesia.Config.get([:metadata, :version]) == "0.5.0"
+    assert Parrhesia.Config.get([:metadata, :hide_version?]) == true
     assert Parrhesia.Config.get([:limits, :max_frame_bytes]) == 1_048_576
     assert Parrhesia.Config.get([:limits, :max_event_bytes]) == 262_144
     assert Parrhesia.Config.get([:limits, :max_event_future_skew_seconds]) == 900
diff --git a/test/parrhesia/http_test.exs b/test/parrhesia/http_test.exs
new file mode 100644
index 0000000..361eacb
--- /dev/null
+++ b/test/parrhesia/http_test.exs
@@ -0,0 +1,32 @@
+defmodule Parrhesia.HTTPTest do
+  use ExUnit.Case, async: true
+
+  alias Parrhesia.HTTP
+  alias Parrhesia.Metadata
+
+  test "default headers advertise the configured user agent" do
+    assert Metadata.hide_version?() == true
+    assert HTTP.default_headers() == [{"user-agent", Metadata.user_agent()}]
+  end
+
+  test "default headers are added without overriding request-specific headers" do
+    options =
+      HTTP.put_default_headers(
+        headers: [{"accept", "application/nostr+json"}],
+        decode_body: false
+      )
+
+    assert Keyword.get(options, :headers) == [
+             {"accept", "application/nostr+json"},
+             {"user-agent", Metadata.user_agent()}
+           ]
+
+    assert Keyword.get(options, :decode_body) == false
+  end
+
+  test "explicit user-agent overrides suppress the default case-insensitively" do
+    options = HTTP.put_default_headers(headers: [{"User-Agent", "custom-agent"}])
+
+    assert Keyword.get(options, :headers) == [{"User-Agent", "custom-agent"}]
+  end
+end
diff --git a/test/parrhesia/web/relay_info_test.exs b/test/parrhesia/web/relay_info_test.exs
new file mode 100644
index 0000000..a95009d
--- /dev/null
+++ b/test/parrhesia/web/relay_info_test.exs
@@ -0,0 +1,17 @@
+defmodule Parrhesia.Web.RelayInfoTest do
+  use ExUnit.Case, async: true
+
+  alias Parrhesia.Web.Listener
+  alias Parrhesia.Web.RelayInfo
+
+  test "nip-11 omits version when metadata hides it" do
+    document =
+      :parrhesia
+      |> Application.get_env(:listeners, %{})
+      |> Keyword.fetch!(:public)
+      |> then(&Listener.from_opts(listener: &1))
+      |> RelayInfo.document()
+
+    refute Map.has_key?(document, "version")
+  end
+end