diff --git a/changelog.d/mediaproxy-content-type.fix b/changelog.d/mediaproxy-content-type.fix
new file mode 100644
index 000000000..f36dd6283
--- /dev/null
+++ b/changelog.d/mediaproxy-content-type.fix
@@ -0,0 +1 @@
+Detect image content types for extensionless MediaProxy responses.
diff --git a/lib/pleroma/reverse_proxy.ex b/lib/pleroma/reverse_proxy.ex
index 11f041c57..061b2de9b 100644
--- a/lib/pleroma/reverse_proxy.ex
+++ b/lib/pleroma/reverse_proxy.ex
@@ -17,6 +17,7 @@ defmodule Pleroma.ReverseProxy do
   @max_read_duration :timer.seconds(30)
   @max_body_length :infinity
   @failed_request_ttl :timer.seconds(60)
+  @sniff_bytes 8 * 1024
   @methods ~w(GET HEAD)
 
   @allowed_mime_types Pleroma.Config.get([Pleroma.Upload, :allowed_mime_types], [])
@@ -63,6 +64,9 @@ defmodule Pleroma.ReverseProxy do
     is always set (overriding any upstream header) so the media can be embedded
     in pages; the filename is derived from the content type
 
+  * `sniff_content_type` (default `false`): detects an image MIME type from the first
+  response chunk when the upstream type is missing or `application/octet-stream`.
+
   * `req_headers`, `resp_headers` additional headers.
 
   * `http`: options for [hackney](https://github.com/benoitc/hackney) or [gun](https://github.com/ninenines/gun).
@@ -71,11 +75,15 @@ defmodule Pleroma.ReverseProxy do
   @default_options [pool: :media]
 
   @inline_content_types [
+    "image/apng",
+    "image/avif",
+    "image/bmp",
     "image/gif",
     "image/jpeg",
     "image/jpg",
     "image/png",
     "image/svg+xml",
+    "image/webp",
     "audio/mpeg",
     "audio/mp3",
     "video/webm",
@@ -94,6 +102,7 @@ defmodule Pleroma.ReverseProxy do
           | {:req_headers, [{String.t(), String.t()}]}
           | {:resp_headers, [{String.t(), String.t()}]}
           | {:inline_content_types, boolean() | list(String.t())}
+          | {:sniff_content_type, boolean()}
           | {:redirect_on_failure, boolean()}
 
   @spec call(Plug.Conn.t(), String.t(), list(option())) :: Plug.Conn.t()
@@ -186,12 +195,14 @@ defmodule Pleroma.ReverseProxy do
   defp response(conn, client, url, status, headers, opts) do
     Logger.debug("#{__MODULE__} #{status} #{url} #{inspect(headers)}")
 
+    {headers, client, prefetched} = maybe_prefetch_for_content_type(headers, client, opts)
+
     result =
       conn
       |> put_resp_headers(build_resp_headers(headers, opts))
       |> streaming_compat
       |> send_chunked(status)
-      |> chunk_reply(client, opts)
+      |> chunk_reply(client, opts, prefetched)
 
     case result do
       {:ok, conn} ->
@@ -211,18 +222,28 @@ defmodule Pleroma.ReverseProxy do
     end
   end
 
-  defp chunk_reply(conn, client, opts) do
+  defp chunk_reply(conn, client, opts, :none) do
     chunk_reply(conn, client, opts, 0, 0)
   end
 
-  defp chunk_reply(conn, client, opts, sent_so_far, duration) do
-    with {:ok, duration} <-
-           check_read_duration(
-             duration,
-             Keyword.get(opts, :max_read_duration, @max_read_duration)
+  defp chunk_reply(conn, _client, _opts, :done), do: {:ok, conn}
+  defp chunk_reply(conn, _client, _opts, {:error, error}), do: {:error, error, conn}
+
+  defp chunk_reply(conn, client, opts, {:ok, data, duration}) do
+    with :ok <-
+           body_size_constraint(
+             byte_size(data),
+             Keyword.get(opts, :max_body_length, @max_body_length)
            ),
-         {:ok, data, client} <- client().stream_body(client),
-         {:ok, duration} <- increase_read_duration(duration),
+         {:ok, conn} <- chunk(conn, data) do
+      chunk_reply(conn, client, opts, byte_size(data), duration)
+    else
+      {:error, error} -> {:error, error, conn}
+    end
+  end
+
+  defp chunk_reply(conn, client, opts, sent_so_far, duration) do
+    with {:ok, data, client, duration} <- read_chunk(client, duration, opts),
          sent_so_far = sent_so_far + byte_size(data),
          :ok <-
            body_size_constraint(
@@ -237,6 +258,66 @@ defmodule Pleroma.ReverseProxy do
     end
   end
 
+  defp read_chunk(client, duration, opts) do
+    with {:ok, timer} <-
+           check_read_duration(
+             duration,
+             Keyword.get(opts, :max_read_duration, @max_read_duration)
+           ),
+         {:ok, data, client} <- client().stream_body(client),
+         {:ok, duration} <- increase_read_duration(timer) do
+      {:ok, data, client, duration}
+    end
+  end
+
+  defp maybe_prefetch_for_content_type(headers, client, opts) do
+    if Keyword.get(opts, :sniff_content_type, false) and generic_content_type?(headers) do
+      case read_chunk(client, 0, opts) do
+        {:ok, data, client, duration} ->
+          {maybe_put_image_content_type(headers, data), client, {:ok, data, duration}}
+
+        :done ->
+          {headers, client, :done}
+
+        {:error, error} ->
+          {headers, client, {:error, error}}
+      end
+    else
+      {headers, client, :none}
+    end
+  end
+
+  defp generic_content_type?(headers) do
+    headers
+    |> get_content_type()
+    |> String.trim()
+    |> String.downcase()
+    |> then(&(&1 in ["", "application/octet-stream"]))
+  end
+
+  defp maybe_put_image_content_type(headers, data) do
+    with false <- data == "",
+         {:ok, %{mime_type: "image/" <> _ = content_type}} <-
+           Majic.perform({:bytes, binary_part(data, 0, min(byte_size(data), @sniff_bytes))},
+             pool: Pleroma.MajicPool
+           ) do
+      [
+        {"content-type", content_type}
+        | Enum.reject(headers, fn {key, _} -> key == "content-type" end)
+      ]
+    else
+      _ -> headers
+    end
+  rescue
+    error ->
+      Logger.debug("#{__MODULE__}: content-type sniffing failed: #{Exception.message(error)}")
+      headers
+  catch
+    kind, reason ->
+      Logger.debug("#{__MODULE__}: content-type sniffing failed: #{kind}: #{inspect(reason)}")
+      headers
+  end
+
   defp head_response(conn, url, code, headers, opts) do
     Logger.debug("#{__MODULE__} #{code} #{url} #{inspect(headers)}")
 
@@ -283,17 +364,34 @@ defmodule Pleroma.ReverseProxy do
     |> Enum.filter(fn {k, _} -> k in @keep_req_headers end)
     |> build_req_range_or_encoding_header(opts)
     |> build_req_user_agent_header(opts)
-    |> Keyword.merge(Keyword.get(opts, :req_headers, []))
+    |> merge_headers(Keyword.get(opts, :req_headers, []))
+    |> maybe_force_identity_encoding(opts)
+  end
+
+  defp merge_headers(headers, extra_headers) do
+    Enum.reduce(extra_headers, headers, fn {key, value}, headers ->
+      List.keystore(headers, String.downcase(key), 0, {String.downcase(key), value})
+    end)
+  end
+
+  defp maybe_force_identity_encoding(headers, opts) do
+    if Keyword.get(opts, :sniff_content_type, false) do
+      List.keystore(headers, "accept-encoding", 0, {"accept-encoding", "identity"})
+    else
+      headers
+    end
   end
 
   # Disable content-encoding if any @range_headers are requested (see #1823).
   defp build_req_range_or_encoding_header(headers, _opts) do
     range? = Enum.any?(headers, fn {header, _} -> Enum.member?(@range_headers, header) end)
 
-    if range? && List.keymember?(headers, "accept-encoding", 0) do
-      List.keydelete(headers, "accept-encoding", 0)
-    else
-      headers
+    cond do
+      range? && List.keymember?(headers, "accept-encoding", 0) ->
+        List.keydelete(headers, "accept-encoding", 0)
+
+      true ->
+        headers
     end
   end
 
@@ -386,7 +484,7 @@ defmodule Pleroma.ReverseProxy do
 
       disposition = "attachment; filename=\"#{name}\""
 
-      List.keystore(headers, "content-disposition", 0, {"content-disposition", disposition})
+      replace_header(headers, "content-disposition", disposition)
     else
       if opt == true do
         headers
@@ -400,11 +498,15 @@ defmodule Pleroma.ReverseProxy do
             "inline"
           end
 
-        List.keystore(headers, "content-disposition", 0, {"content-disposition", disposition})
+        replace_header(headers, "content-disposition", disposition)
       end
     end
   end
 
+  defp replace_header(headers, key, value) do
+    [{key, value} | Enum.reject(headers, fn {header, _} -> header == key end)]
+  end
+
   defp inline_filename(content_type) do
     case MIME.extensions(content_type) do
       [ext | _] when ext != "" -> "inline.#{ext}"
@@ -443,7 +545,9 @@ defmodule Pleroma.ReverseProxy do
     end
   end
 
-  defp check_read_duration(_, _), do: {:ok, :no_duration_limit, :no_duration_limit}
+  defp check_read_duration(_, _), do: {:ok, :no_duration_limit}
+
+  defp increase_read_duration(:no_duration_limit), do: {:ok, :no_duration_limit}
 
   defp increase_read_duration({previous_duration, started})
        when is_integer(previous_duration) and is_integer(started) do
diff --git a/lib/pleroma/web/activity_pub/object_validators/attachment_type_sniffer.ex b/lib/pleroma/web/activity_pub/object_validators/attachment_type_sniffer.ex
deleted file mode 100644
index 19215b627..000000000
--- a/lib/pleroma/web/activity_pub/object_validators/attachment_type_sniffer.ex
+++ /dev/null
@@ -1,59 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Web.ActivityPub.ObjectValidators.AttachmentTypeSniffer do
-  @moduledoc """
-  Best-effort MIME sniffing for remote attachments whose declared type is
-  unusable (missing or `application/octet-stream`).
-
-  Fetches the first chunk of the URL and runs it through libmagic. Only
-  `image/*` results are returned; anything else, or any failure, yields `nil` —
-  so this never reclassifies non-image media and never blocks ingestion. This
-  exists because some remotes (e.g. extensionless Cloudflare Images URLs) ship
-  attachments with no usable `mediaType`, which would otherwise render in the
-  timeline as a clickable link instead of an inline image.
-  """
-
-  alias Pleroma.HTTP
-
-  require Logger
-
-  # libmagic only needs the file header; a few KB is plenty and keeps the
-  # request cheap even when the origin ignores Range.
-  @sniff_bytes 8 * 1024
-  @timeout 5_000
-
-  @spec sniff_image_type(binary() | nil) :: {:ok, binary() | nil}
-  def sniff_image_type(url) when is_binary(url) and url != "" do
-    do_sniff(url)
-  rescue
-    e ->
-      Logger.debug(
-        "Attachment type sniff failed for #{url}: #{Exception.format(:error, e, __STACKTRACE__)}"
-      )
-
-      {:ok, nil}
-  end
-
-  def sniff_image_type(_), do: {:ok, nil}
-
-  defp do_sniff(url) do
-    headers = [{"range", "bytes=0-#{@sniff_bytes - 1}"}]
-    opts = [pool: :media, timeout: @timeout, recv_timeout: @timeout]
-
-    with {:ok, %Tesla.Env{status: status, body: body}} when status in 200..299 <-
-           HTTP.get(url, headers, opts),
-         false <- blank?(body),
-         {:ok, %{mime_type: mime}} <- Majic.perform({:bytes, body}, pool: Pleroma.MajicPool),
-         true <- String.starts_with?(mime, "image/") do
-      {:ok, mime}
-    else
-      _ -> {:ok, nil}
-    end
-  end
-
-  defp blank?(nil), do: true
-  defp blank?(""), do: true
-  defp blank?(_), do: false
-end
diff --git a/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex b/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex
index b6e30a438..5ee9e7549 100644
--- a/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex
+++ b/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex
@@ -6,7 +6,6 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.AttachmentValidator do
   use Ecto.Schema
 
   alias Pleroma.EctoType.ActivityPub.ObjectValidators
-  alias Pleroma.Web.ActivityPub.ObjectValidators.AttachmentTypeSniffer
 
   import Ecto.Changeset
 
@@ -62,27 +61,9 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.AttachmentValidator do
   end
 
   def fix_media_type(data) do
-    current = data["mediaType"] || data["mimeType"] || "application/octet-stream"
-
-    resolved =
-      if sniffable?(current) do
-        case AttachmentTypeSniffer.sniff_image_type(data["href"]) do
-          {:ok, mime} when is_binary(mime) -> mime
-          _ -> current
-        end
-      else
-        current
-      end
-
-    Map.put(data, "mediaType", resolved)
+    Map.put_new(data, "mediaType", data["mimeType"] || "application/octet-stream")
   end
 
-  # Only sniff when the declared type carries no real information. Everything
-  # else (including unrecognized-but-present types) is left as the remote sent it.
-  defp sniffable?("application/octet-stream"), do: true
-  defp sniffable?(""), do: true
-  defp sniffable?(_), do: false
-
   defp handle_href(href, mediaType, data) do
     [
       %{
diff --git a/lib/pleroma/web/mastodon_api/views/status_view.ex b/lib/pleroma/web/mastodon_api/views/status_view.ex
index 6949c5f2d..725dc2ce7 100644
--- a/lib/pleroma/web/mastodon_api/views/status_view.ex
+++ b/lib/pleroma/web/mastodon_api/views/status_view.ex
@@ -620,6 +620,7 @@ defmodule Pleroma.Web.MastodonAPI.StatusView do
         String.contains?(media_type, "image") -> "image"
         String.contains?(media_type, "video") -> "video"
         String.contains?(media_type, "audio") -> "audio"
+        attachment["type"] == "Image" -> "image"
         true -> "unknown"
       end
 
diff --git a/lib/pleroma/web/media_proxy/media_proxy_controller.ex b/lib/pleroma/web/media_proxy/media_proxy_controller.ex
index a0aafc32e..93f692008 100644
--- a/lib/pleroma/web/media_proxy/media_proxy_controller.ex
+++ b/lib/pleroma/web/media_proxy/media_proxy_controller.ex
@@ -208,6 +208,7 @@ defmodule Pleroma.Web.MediaProxy.MediaProxyController do
 
   defp media_proxy_opts do
     Config.get([:media_proxy, :proxy_opts], [])
+    |> Keyword.put_new(:sniff_content_type, true)
   end
 
   defp sandbox(conn, _params) do
diff --git a/test/pleroma/reverse_proxy_test.exs b/test/pleroma/reverse_proxy_test.exs
index 5f75f2a07..ad1d75f33 100644
--- a/test/pleroma/reverse_proxy_test.exs
+++ b/test/pleroma/reverse_proxy_test.exs
@@ -222,6 +222,56 @@ defmodule Pleroma.ReverseProxyTest do
     assert Conn.get_resp_header(conn, "content-type") == ["application/octet-stream"]
   end
 
+  test "sniffs and preserves an image body with a generic content type", %{conn: conn} do
+    body = File.read!("test/fixtures/image.jpg")
+
+    ClientMock
+    |> expect(:request, fn :get, "/extensionless", headers, _, _ ->
+      assert {"accept-encoding", "identity"} in headers
+      {:ok, 200, [{"content-type", "application/octet-stream"}], %{body: body}}
+    end)
+    |> expect(:stream_body, fn %{body: ^body} = client ->
+      {:ok, body, Map.delete(client, :body)}
+    end)
+    |> expect(:stream_body, fn %{} -> :done end)
+
+    conn =
+      ReverseProxy.call(conn, "/extensionless",
+        sniff_content_type: true,
+        max_read_duration: :infinity,
+        req_headers: [{"accept-encoding", "gzip"}]
+      )
+
+    assert conn.resp_body == body
+    assert Conn.get_resp_header(conn, "content-type") == ["image/jpeg"]
+
+    assert Conn.get_resp_header(conn, "content-disposition") == [
+             "inline; filename=\"inline.jpg\""
+           ]
+  end
+
+  test "preserves a generic content type for a non-image body", %{conn: conn} do
+    body = "not an image"
+
+    ClientMock
+    |> expect(:request, fn :get, "/extensionless", _, _, _ ->
+      {:ok, 200, [], %{body: body}}
+    end)
+    |> expect(:stream_body, fn %{body: ^body} = client ->
+      {:ok, body, Map.delete(client, :body)}
+    end)
+    |> expect(:stream_body, fn %{} -> :done end)
+
+    conn = ReverseProxy.call(conn, "/extensionless", sniff_content_type: true)
+
+    assert conn.resp_body == body
+    assert Conn.get_resp_header(conn, "content-type") == ["application/octet-stream"]
+
+    assert Conn.get_resp_header(conn, "content-disposition") == [
+             "attachment; filename=\"extensionless\""
+           ]
+  end
+
   defp headers_mock(_) do
     ClientMock
     |> expect(:request, fn :get, "/headers", headers, _, _ ->
@@ -298,21 +348,21 @@ defmodule Pleroma.ReverseProxyTest do
     end
   end
 
-  defp disposition_headers_mock(headers, url \\ "/disposition") do
+  defp disposition_headers_mock(headers) do
     ClientMock
-    |> expect(:request, fn :get, ^url, _, _, _ ->
-      Registry.register(ClientMock, url, 0)
+    |> expect(:request, fn :get, "/disposition", _, _, _ ->
+      Registry.register(ClientMock, "/disposition", 0)
 
-      {:ok, 200, headers, %{url: url}}
+      {:ok, 200, headers, %{url: "/disposition"}}
     end)
-    |> expect(:stream_body, 2, fn %{url: ^url} = client ->
-      case Registry.lookup(ClientMock, url) do
+    |> expect(:stream_body, 2, fn %{url: "/disposition"} = client ->
+      case Registry.lookup(ClientMock, "/disposition") do
         [{_, 0}] ->
-          Registry.update_value(ClientMock, url, &(&1 + 1))
+          Registry.update_value(ClientMock, "/disposition", &(&1 + 1))
           {:ok, "", client}
 
         [{_, 1}] ->
-          Registry.unregister(ClientMock, url)
+          Registry.unregister(ClientMock, "/disposition")
           :done
       end
     end)
@@ -337,6 +387,7 @@ defmodule Pleroma.ReverseProxyTest do
       disposition_headers_mock([
         {"content-type", "image/png"},
         {"content-disposition", "attachment; filename=\"filename.png\""},
+        {"content-disposition", "attachment; filename=\"duplicate.png\""},
         {"content-length", "0"}
       ])
 
@@ -347,23 +398,6 @@ defmodule Pleroma.ReverseProxyTest do
       refute String.starts_with?(disposition, "attachment")
     end
 
-    test "forces inline based on content type even without a file extension in the url", %{
-      conn: conn
-    } do
-      disposition_headers_mock(
-        [
-          {"content-type", "image/jpeg"},
-          {"content-length", "0"}
-        ],
-        "/original"
-      )
-
-      conn = ReverseProxy.call(conn, "/original")
-
-      [disposition] = Conn.get_resp_header(conn, "content-disposition")
-      assert disposition == "inline; filename=\"inline.jpg\""
-    end
-
     test "with content-disposition header", %{conn: conn} do
       disposition_headers_mock([
         {"content-disposition", "attachment; filename=\"filename.jpg\""},
@@ -390,69 +424,6 @@ defmodule Pleroma.ReverseProxyTest do
       assert {"content-disposition", "attachment; filename=\"upstream.png\""} in conn.resp_headers
     end
 
-    test "with inline_content_types: true does not synthesise inline when upstream is absent", %{
-      conn: conn
-    } do
-      disposition_headers_mock([
-        {"content-type", "image/png"},
-        {"content-length", "0"}
-      ])
-
-      conn = ReverseProxy.call(conn, "/disposition", inline_content_types: true)
-
-      assert Conn.get_resp_header(conn, "content-disposition") == []
-    end
-
-    test "with inline_content_types: false forces attachment for everything", %{
-      conn: conn
-    } do
-      disposition_headers_mock([
-        {"content-type", "image/png"},
-        {"content-disposition", "inline; filename=\"pic.png\""},
-        {"content-length", "0"}
-      ])
-
-      conn = ReverseProxy.call(conn, "/disposition", inline_content_types: false)
-
-      [disposition] = Conn.get_resp_header(conn, "content-disposition")
-      assert String.starts_with?(disposition, "attachment")
-    end
-
-    test "with inline_content_types: false derives attachment filename from the URL basename when no upstream filename", %{
-      conn: conn
-    } do
-      # No content-disposition header: the attachment branch falls back to
-      # attachment_name, which by default comes from MediaProxy.filename/1
-      # (the URL basename).
-      disposition_headers_mock([
-        {"content-type", "image/png"},
-        {"content-length", "0"}
-      ])
-
-      conn = ReverseProxy.call(conn, "/disposition", inline_content_types: false)
-
-      [disposition] = Conn.get_resp_header(conn, "content-disposition")
-      assert disposition == "attachment; filename=\"disposition\""
-    end
-
-    test "with inline_content_types: false honours an explicit attachment_name opt", %{
-      conn: conn
-    } do
-      disposition_headers_mock([
-        {"content-type", "image/png"},
-        {"content-length", "0"}
-      ])
-
-      conn =
-        ReverseProxy.call(conn, "/disposition",
-          inline_content_types: false,
-          attachment_name: "custom.bin"
-        )
-
-      [disposition] = Conn.get_resp_header(conn, "content-disposition")
-      assert disposition == "attachment; filename=\"custom.bin\""
-    end
-
     test "forces bare inline for a whitelisted type with no MIME extension", %{
       conn: conn
     } do
@@ -469,36 +440,17 @@ defmodule Pleroma.ReverseProxyTest do
       assert disposition == "inline"
     end
 
-    test "honours a custom inline_content_types whitelist", %{conn: conn} do
-      # image/bmp is NOT in the default whitelist; with a custom whitelist
-      # that includes it, the proxy should force inline.
+    test "serves modern browser image types inline", %{conn: conn} do
       disposition_headers_mock([
-        {"content-type", "image/bmp"},
-        {"content-disposition", "attachment; filename=\"upstream.bmp\""},
+        {"content-type", "image/webp"},
         {"content-length", "0"}
       ])
 
-      conn =
-        ReverseProxy.call(conn, "/disposition", inline_content_types: ["image/bmp"])
+      conn = ReverseProxy.call(conn, "/disposition")
 
-      [disposition] = Conn.get_resp_header(conn, "content-disposition")
-      assert String.starts_with?(disposition, "inline")
-      assert String.ends_with?(disposition, "inline.bmp\"")
-    end
-
-    test "treats a type outside the whitelist as attachment even on custom whitelist", %{
-      conn: conn
-    } do
-      disposition_headers_mock([
-        {"content-type", "image/png"},
-        {"content-disposition", "attachment; filename=\"filename.png\""},
-        {"content-length", "0"}
-      ])
-
-      conn =
-        ReverseProxy.call(conn, "/disposition", inline_content_types: ["image/bmp"])
-
-      assert {"content-disposition", "attachment; filename=\"filename.png\""} in conn.resp_headers
+      assert Conn.get_resp_header(conn, "content-disposition") == [
+               "inline; filename=\"inline.webp\""
+             ]
     end
   end
 
diff --git a/test/pleroma/web/activity_pub/object_validators/attachment_type_sniffer_test.exs b/test/pleroma/web/activity_pub/object_validators/attachment_type_sniffer_test.exs
deleted file mode 100644
index 52b1b67a1..000000000
--- a/test/pleroma/web/activity_pub/object_validators/attachment_type_sniffer_test.exs
+++ /dev/null
@@ -1,178 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Web.ActivityPub.ObjectValidators.AttachmentTypeSnifferTest do
-  use Pleroma.DataCase, async: true
-
-  alias Pleroma.Web.ActivityPub.ObjectValidators.AttachmentTypeSniffer
-
-  # @sniff_bytes must mirror the value in the module under test; we assert the
-  # Range header that the sniffer sends, so the test should fail loudly if the
-  # constant drifts.
-  @sniff_bytes 8 * 1024
-  @range_header "bytes=0-#{@sniff_bytes - 1}"
-
-  describe "sniff_image_type/1 with a real image body" do
-    test "returns image/jpeg for a JPEG body" do
-      url = "https://example.com/media/image.jpg"
-      jpeg = File.read!("test/fixtures/image.jpg")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: jpeg}
-      end)
-
-      assert {:ok, "image/jpeg"} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns image/png for a PNG body" do
-      url = "https://example.com/media/image.png"
-      png = File.read!("test/fixtures/image.png")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: png}
-      end)
-
-      assert {:ok, "image/png"} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns image/gif for a GIF body" do
-      url = "https://example.com/media/image.gif"
-      gif = File.read!("test/fixtures/image.gif")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: gif}
-      end)
-
-      assert {:ok, "image/gif"} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-  end
-
-  describe "sniff_image_type/1 sends a ranged request" do
-    test "sends a Range header asking for the first chunk" do
-      url = "https://example.com/media/ranged"
-      jpeg = File.read!("test/fixtures/image.jpg")
-
-      Tesla.Mock.mock(fn
-        %{method: :get, url: ^url, headers: headers} ->
-          headers_map = Enum.into(headers, %{})
-          assert headers_map["range"] == @range_header
-
-          %Tesla.Env{status: 200, body: jpeg}
-
-        %{method: :get, url: ^url} ->
-          # If the sniffer did not send the Range header, fail explicitly.
-          flunk("expected Range header to be sent with the request")
-      end)
-
-      assert {:ok, "image/jpeg"} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-  end
-
-  describe "sniff_image_type/1 with a non-image body" do
-    test "returns nil for plain text" do
-      url = "https://example.com/media/note.txt"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: "just some plain text, not an image at all"}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns nil for an HTML body" do
-      url = "https://example.com/page"
-      html = File.read!("test/fixtures/rel_me_anchor.html")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: html}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns nil for an empty body" do
-      url = "https://example.com/media/empty"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: ""}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns nil for a nil body" do
-      url = "https://example.com/media/nil-body"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: nil}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-  end
-
-  describe "sniff_image_type/1 on HTTP failure" do
-    test "returns nil on a 404" do
-      url = "https://example.com/media/missing"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 404, body: ""}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns nil on a 500" do
-      url = "https://example.com/media/oops"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 500, body: "server error"}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns nil on a 3xx (not in 200..299)" do
-      url = "https://example.com/media/redirect"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 302, body: ""}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns nil on a transport-level error" do
-      url = "https://example.com/media/econnrefused"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        {:error, :econnrefused}
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-
-    test "returns nil when the HTTP adapter raises" do
-      url = "https://example.com/media/raises"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        raise "boom"
-      end)
-
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(url)
-    end
-  end
-
-  describe "sniff_image_type/1 guard clauses" do
-    test "returns nil for nil input without making a request" do
-      # No Tesla mock is configured; if a request were made, Tesla.Mock would
-      # raise and fail the test.
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type(nil)
-    end
-
-    test "returns nil for an empty-string URL without making a request" do
-      assert {:ok, nil} = AttachmentTypeSniffer.sniff_image_type("")
-    end
-  end
-end
diff --git a/test/pleroma/web/activity_pub/object_validators/attachment_validator_test.exs b/test/pleroma/web/activity_pub/object_validators/attachment_validator_test.exs
index 870ad90cc..744ae8704 100644
--- a/test/pleroma/web/activity_pub/object_validators/attachment_validator_test.exs
+++ b/test/pleroma/web/activity_pub/object_validators/attachment_validator_test.exs
@@ -215,226 +215,5 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.AttachmentValidatorTest do
         AttachmentValidator.cast_and_validate(attachment)
         |> Ecto.Changeset.apply_action(:insert)
     end
-
-    test "sniffs image/jpeg for octet-stream attachments whose body is an image" do
-      url = "https://example.com/media/no-extension/original"
-      jpeg = File.read!("test/fixtures/image.jpg")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: jpeg}
-      end)
-
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "application/octet-stream",
-        "url" => [%{"type" => "Link", "href" => url, "mediaType" => "application/octet-stream"}]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [%{href: ^url, mediaType: "image/jpeg"}] = attachment.url
-    end
-
-    test "sniffs image/jpeg for attachments with a missing mediaType" do
-      url = "https://example.com/media/missing-type/original"
-      jpeg = File.read!("test/fixtures/image.jpg")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: jpeg}
-      end)
-
-      attachment = %{
-        "type" => "Document",
-        "url" => [%{"type" => "Link", "href" => url}]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [%{href: ^url, mediaType: "image/jpeg"}] = attachment.url
-    end
-
-    test "leaves non-image octet-stream attachments as octet-stream" do
-      url = "https://example.com/media/some-document"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: "just some plain text, not an image at all"}
-      end)
-
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "application/octet-stream",
-        "url" => [%{"type" => "Link", "href" => url, "mediaType" => "application/octet-stream"}]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [%{mediaType: "application/octet-stream"}] = attachment.url
-    end
-
-    test "does not sniff when the remote already provided a real mediaType" do
-      # No Tesla mock is set up: if the validator tried to fetch, Tesla.Mock
-      # would raise and fail the test. A real image type must be kept as-is.
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "image/png",
-        "url" => [
-          %{"type" => "Link", "href" => "https://example.com/x", "mediaType" => "image/png"}
-        ]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [%{mediaType: "image/png"}] = attachment.url
-    end
-  end
-
-  describe "fix_media_type fallbacks and sniffing" do
-    test "uses mimeType as a fallback when mediaType is absent (real type, not sniffed)" do
-      # No Tesla mock: if the validator tried to fetch, the test would fail.
-      # A real image type coming from mimeType must be preserved as-is on the
-      # outer attachment and on the synthesised url entry (string url form).
-      attachment = %{
-        "type" => "Document",
-        "mimeType" => "image/png",
-        "url" => "https://example.com/x.png"
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert attachment.mediaType == "image/png"
-      assert [%{mediaType: "image/png"}] = attachment.url
-    end
-
-    test "prefers mediaType over mimeType when both are present" do
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "image/gif",
-        "mimeType" => "image/png",
-        "url" => "https://example.com/x.gif"
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert attachment.mediaType == "image/gif"
-      assert [%{mediaType: "image/gif"}] = attachment.url
-    end
-
-    test "sniffs when the url entry's mediaType is application/octet-stream and the body is an image" do
-      # The outer attachment mediaType is not sniffed (no top-level href); only
-      # the url entry is. We assert only on the url entry.
-      url = "https://example.com/media/mime-type-octet"
-      jpeg = File.read!("test/fixtures/image.jpg")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: jpeg}
-      end)
-
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "application/octet-stream",
-        "url" => [%{"type" => "Link", "href" => url, "mediaType" => "application/octet-stream"}]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [%{mediaType: "image/jpeg"}] = attachment.url
-    end
-
-    test "sniffs when mediaType is the empty string and the body is an image" do
-      url = "https://example.com/media/empty-mediatype"
-      png = File.read!("test/fixtures/image.png")
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 200, body: png}
-      end)
-
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "",
-        "url" => [%{"type" => "Link", "href" => url, "mediaType" => ""}]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [%{mediaType: "image/png"}] = attachment.url
-    end
-
-    test "falls back to the declared type when the sniffer HTTP request fails" do
-      url = "https://example.com/media/sniff-404"
-
-      Tesla.Mock.mock(fn %{method: :get, url: ^url} ->
-        %Tesla.Env{status: 404, body: ""}
-      end)
-
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "application/octet-stream",
-        "url" => [%{"type" => "Link", "href" => url, "mediaType" => "application/octet-stream"}]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [%{mediaType: "application/octet-stream"}] = attachment.url
-    end
-
-    test "sniffs each url entry independently" do
-      jpeg_url = "https://example.com/media/a"
-      octet_url = "https://example.com/media/b"
-      jpeg = File.read!("test/fixtures/image.jpg")
-
-      Tesla.Mock.mock(fn
-        %{method: :get, url: ^jpeg_url} ->
-          %Tesla.Env{status: 200, body: jpeg}
-
-        %{method: :get, url: ^octet_url} ->
-          %Tesla.Env{status: 200, body: "definitely not an image"}
-      end)
-
-      attachment = %{
-        "type" => "Document",
-        "mediaType" => "application/octet-stream",
-        "url" => [
-          %{"type" => "Link", "href" => jpeg_url, "mediaType" => "application/octet-stream"},
-          %{"type" => "Link", "href" => octet_url, "mediaType" => "application/octet-stream"}
-        ]
-      }
-
-      {:ok, attachment} =
-        attachment
-        |> AttachmentValidator.cast_and_validate()
-        |> Ecto.Changeset.apply_action(:insert)
-
-      assert [
-               %{href: ^jpeg_url, mediaType: "image/jpeg"},
-               %{href: ^octet_url, mediaType: "application/octet-stream"}
-             ] = attachment.url
-    end
   end
 end
diff --git a/test/pleroma/web/mastodon_api/views/status_view_test.exs b/test/pleroma/web/mastodon_api/views/status_view_test.exs
index 76123cd0f..faeca050e 100644
--- a/test/pleroma/web/mastodon_api/views/status_view_test.exs
+++ b/test/pleroma/web/mastodon_api/views/status_view_test.exs
@@ -668,6 +668,23 @@ defmodule Pleroma.Web.MastodonAPI.StatusViewTest do
       assert expected == StatusView.render("attachment.json", %{attachment: object})
       assert_schema(expected, "Attachment", api_spec)
     end
+
+    test "uses the ActivityStreams image type when the MIME type is generic" do
+      object = %{
+        "type" => "Image",
+        "url" => [
+          %{
+            "mediaType" => "application/octet-stream",
+            "href" => "https://example.com/extensionless"
+          }
+        ]
+      }
+
+      attachment = StatusView.render("attachment.json", %{attachment: object})
+
+      assert attachment.type == "image"
+      assert attachment.pleroma.mime_type == "application/octet-stream"
+    end
   end
 
   test "put the url advertised in the Activity in to the url attribute" do
diff --git a/test/pleroma/web/media_proxy/media_proxy_controller_test.exs b/test/pleroma/web/media_proxy/media_proxy_controller_test.exs
index f7e52483c..800159c21 100644
--- a/test/pleroma/web/media_proxy/media_proxy_controller_test.exs
+++ b/test/pleroma/web/media_proxy/media_proxy_controller_test.exs
@@ -71,7 +71,10 @@ defmodule Pleroma.Web.MediaProxy.MediaProxyControllerTest do
 
     test "it performs ReverseProxy.call with valid signature", %{conn: conn, url: url} do
       with_mock Pleroma.ReverseProxy,
-        call: fn _conn, _url, _opts -> %Conn{status: :success} end do
+        call: fn _conn, _url, opts ->
+          assert opts[:sniff_content_type]
+          %Conn{status: :success}
+        end do
         assert %Conn{status: :success} = get(conn, url)
       end
     end