diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 1753855..1b4828f 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -60,24 +60,8 @@ jobs:
             exit 1
           fi
 
-      - name: Install dependencies
-        run: brew install aria2 dylibbundler
-
       - name: Fetch media engines
-        run: |
-          mkdir -p Sources/Firelink
-
-          # Download the one-file macOS build. PyInstaller on macOS now properly supports code-signing without corrupting the archive.
-          curl -fsSL https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp_macos -o Sources/Firelink/yt-dlp
-          chmod +x Sources/Firelink/yt-dlp
-
-          # Download latest FFmpeg release build for macOS ARM64 from Martin Riedl's build server
-          curl -fsSL "https://ffmpeg.martin-riedl.de/redirect/latest/macos/arm64/release/ffmpeg.zip" -o ffmpeg.zip
-          unzip -q -o ffmpeg.zip -d Sources/Firelink
-          rm ffmpeg.zip
-          chmod +x Sources/Firelink/ffmpeg
-          test -x Sources/Firelink/yt-dlp
-          test -x Sources/Firelink/ffmpeg
+        run: Scripts/fetch_media_engines.sh
 
       - name: Build app bundle
         env:
@@ -89,7 +73,25 @@ jobs:
         run: |
           file build/Firelink.app/Contents/MacOS/Firelink
           lipo -archs build/Firelink.app/Contents/MacOS/Firelink | grep -qx arm64
-          codesign --verify --deep build/Firelink.app
+          codesign --verify --deep --strict build/Firelink.app
+
+          RESOURCES="build/Firelink.app/Contents/Resources"
+          test -d "$RESOURCES/_internal"
+          test -x "$RESOURCES/yt-dlp"
+          test -x "$RESOURCES/deno"
+          test -x "$RESOURCES/ffmpeg"
+          test -x "$RESOURCES/aria2c"
+          test -f "$RESOURCES/aria2-cacert.pem"
+          test -d "$RESOURCES/aria2-libs"
+          test "$(tr -d '[:space:]' < "$RESOURCES/aria2-version.txt")" = "1.37.0-2-arm64-sonoma"
+          test "$("$RESOURCES/yt-dlp" --version)" = "$(tr -d '[:space:]' < "$RESOURCES/yt-dlp-version.txt")"
+          "$RESOURCES/deno" --version
+          "$RESOURCES/ffmpeg" -version
+          "$RESOURCES/aria2c" --version | grep -q '^aria2 version 1.37.0$'
+          for library in "$RESOURCES"/aria2-libs/*.dylib; do
+            lipo -archs "$library" | grep -qx arm64
+          done
+          ! otool -L "$RESOURCES/aria2c" "$RESOURCES"/aria2-libs/*.dylib | grep -Eq '(@@HOMEBREW|/opt/homebrew|/usr/local)'
 
       - name: Create DMG
         env:
diff --git a/.gitignore b/.gitignore
index e02dde7..157943f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -23,8 +23,14 @@ SparklePrivateKey*
 private-key*
 private_key*
 yt-dlp
+deno
 ffmpeg
+aria2c
+Sources/Firelink/*-version.txt
 Sources/Firelink/_internal/
+Sources/Firelink/aria2-libs/
+Sources/Firelink/aria2-licenses/
+Sources/Firelink/aria2-cacert.pem
 !Sources/Firelink/_internal/
 Sources/Firelink/_internal/*
 !Sources/Firelink/_internal/.gitkeep
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 42a88cc..c6fc9de 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,19 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+- Prevented yt-dlp and JavaScript child processes from keeping metadata fetches or canceled downloads alive indefinitely.
+- Replaced the repeatedly extracted one-file yt-dlp build with a stable prewarmed runtime cache.
+- Bundled Deno so YouTube JavaScript challenges and formats above 720p do not depend on system-installed tools.
+- Stopped masking empty-format extraction failures and removed brittle forced YouTube client selection.
+
+### Changed
+- Pinned and checksum-verified yt-dlp, Deno, FFmpeg, aria2, and aria2's libraries for matching local and GitHub Actions builds.
+- Removed aria2's runtime dependency on Homebrew and configured its bundled CA certificate for direct and yt-dlp-delegated HTTPS downloads.
+- Added bounded network retries and optional aria2c acceleration for large direct media downloads.
+
 ## [0.7.1] - 2026-06-11
 
 ### Fixes
diff --git a/Makefile b/Makefile
index afd7dc0..c95c14f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,9 @@
-.PHONY: build app dmg release run verify clean
+.PHONY: engines build app dmg release run verify clean
 
-build:
+engines:
+	Scripts/fetch_media_engines.sh
+
+build: engines
 	swift build -c release
 
 app:
@@ -13,7 +16,7 @@ release:
 	Scripts/create_app_bundle.sh
 	Scripts/create_dmg.sh
 
-run:
+run: engines
 	swift run Firelink
 
 verify:
diff --git a/Package.swift b/Package.swift
index 1200cf9..b97dff4 100644
--- a/Package.swift
+++ b/Package.swift
@@ -17,12 +17,21 @@ let package = Package(
             dependencies: [],
             path: "Sources/Firelink",
             exclude: [
-                "_internal"
+                "deno-version.txt",
+                "ffmpeg-version.txt"
             ],
             resources: [
                 .process("Assets.xcassets"),
                 .copy("yt-dlp"),
-                .copy("ffmpeg")
+                .copy("yt-dlp-version.txt"),
+                .copy("_internal"),
+                .copy("deno"),
+                .copy("ffmpeg"),
+                .copy("aria2c"),
+                .copy("aria2-libs"),
+                .copy("aria2-cacert.pem"),
+                .copy("aria2-version.txt"),
+                .copy("aria2-licenses")
             ]
         )
     ]
diff --git a/Scripts/create_app_bundle.sh b/Scripts/create_app_bundle.sh
index 7f1dd70..e9a4f4c 100755
--- a/Scripts/create_app_bundle.sh
+++ b/Scripts/create_app_bundle.sh
@@ -17,36 +17,7 @@ ICON_NAME="AppIcon"
 
 cd "$ROOT_DIR"
 
-is_valid_mach_o() {
-  local path="$1"
-  if ! file "$path" | grep -q 'Mach-O'; then
-    return 1
-  fi
-
-  lipo -archs "$path" >/dev/null 2>&1
-}
-
-ensure_ytdlp() {
-  local ytdlp_path="$ROOT_DIR/Sources/Firelink/yt-dlp"
-
-  if [[ -x "$ytdlp_path" ]] && is_valid_mach_o "$ytdlp_path"; then
-    return
-  fi
-
-  if ! command -v curl >/dev/null; then
-    echo "WARNING: yt-dlp is missing, and curl is not available to refresh it." >&2
-    return
-  fi
-
-  echo "Refreshing bundled yt-dlp runtime..."
-  curl -fsSL https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp_macos -o "$ytdlp_path"
-  chmod +x "$ytdlp_path"
-  
-  # Remove legacy _internal directory if it exists
-  rm -rf "$ROOT_DIR/Sources/Firelink/_internal"
-}
-
-ensure_ytdlp
+"$ROOT_DIR/Scripts/fetch_media_engines.sh"
 
 swift build -c "$CONFIGURATION"
 
@@ -57,7 +28,7 @@ cp "$ROOT_DIR/Resources/$ICON_NAME.icns" "$RESOURCES_DIR/$ICON_NAME.icns"
 cp "$ROOT_DIR/Sources/Firelink/Assets.xcassets/MenuBarIcon.imageset/MenuBarIconTemplate.png" "$RESOURCES_DIR/MenuBarIconTemplate.png"
 cp "$ROOT_DIR/Resources/GitHubTemplate.png" "$RESOURCES_DIR/GitHubTemplate.png"
 
-for media_engine in yt-dlp ffmpeg; do
+for media_engine in yt-dlp deno ffmpeg aria2c; do
   media_engine_path="$ROOT_DIR/Sources/Firelink/$media_engine"
   if [[ -x "$media_engine_path" ]]; then
     cp "$media_engine_path" "$RESOURCES_DIR/$media_engine"
@@ -67,9 +38,23 @@ for media_engine in yt-dlp ffmpeg; do
   fi
 done
 
-if [[ -d "$ROOT_DIR/Sources/Firelink/_internal" ]]; then
-  cp -R "$ROOT_DIR/Sources/Firelink/_internal" "$RESOURCES_DIR/_internal"
-fi
+for resource_directory in _internal aria2-libs aria2-licenses; do
+  source_path="$ROOT_DIR/Sources/Firelink/$resource_directory"
+  if [[ ! -d "$source_path" ]]; then
+    echo "Required runtime directory is missing: $source_path" >&2
+    exit 1
+  fi
+  cp -R "$source_path" "$RESOURCES_DIR/$resource_directory"
+done
+
+for resource_file in yt-dlp-version.txt aria2-version.txt aria2-cacert.pem; do
+  source_path="$ROOT_DIR/Sources/Firelink/$resource_file"
+  if [[ ! -f "$source_path" ]]; then
+    echo "Required runtime file is missing: $source_path" >&2
+    exit 1
+  fi
+  cp "$source_path" "$RESOURCES_DIR/$resource_file"
+done
 
 echo "Packaging Firefox extension..."
 mkdir -p "$RESOURCES_DIR/FirefoxExtension"
@@ -80,23 +65,6 @@ cp -R "$ROOT_DIR/Extensions/Firefox/icons" "$RESOURCES_DIR/FirefoxExtension/icon
 cp -R "$ROOT_DIR/Extensions/Firefox/popup" "$RESOURCES_DIR/FirefoxExtension/popup"
 
 
-ARIA2C_PATH=$(which aria2c || true)
-if [[ -n "$ARIA2C_PATH" && -x "$ARIA2C_PATH" ]]; then
-  echo "Bundling aria2c from $ARIA2C_PATH..."
-  cp "$ARIA2C_PATH" "$RESOURCES_DIR/aria2c"
-
-  if ! command -v dylibbundler &> /dev/null; then
-    echo "Installing dylibbundler..."
-    brew install dylibbundler
-  fi
-
-  FRAMEWORKS_DIR="$CONTENTS_DIR/Frameworks"
-  mkdir -p "$FRAMEWORKS_DIR"
-  dylibbundler -od -b -x "$RESOURCES_DIR/aria2c" -d "$FRAMEWORKS_DIR" -p "@executable_path/../Frameworks/"
-else
-  echo "WARNING: aria2c not found! It will not be bundled. Please install it first."
-fi
-
 FRAMEWORKS_DIR="$CONTENTS_DIR/Frameworks"
 mkdir -p "$FRAMEWORKS_DIR"
 
@@ -165,6 +133,11 @@ if command -v codesign &> /dev/null; then
 
   sign_mach_o_file() {
     local path="$1"
+    case "$path" in
+      */Python.framework/Python|*/Python.framework/Versions/Current/*)
+        return
+        ;;
+    esac
 
     if file "$path" | grep -q 'Mach-O'; then
       if ! sign_path "$path"; then
@@ -189,7 +162,7 @@ if command -v codesign &> /dev/null; then
 
   sign_path "$MACOS_DIR/$APP_NAME"
   sign_path "$APP_DIR"
-  codesign --verify --deep --verbose=2 "$APP_DIR" || true
+  codesign --verify --deep --strict --verbose=2 "$APP_DIR"
 fi
 
 echo "Created $APP_DIR"
diff --git a/Scripts/fetch_media_engines.sh b/Scripts/fetch_media_engines.sh
new file mode 100755
index 0000000..08178ed
--- /dev/null
+++ b/Scripts/fetch_media_engines.sh
@@ -0,0 +1,337 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+SOURCE_DIR="$ROOT_DIR/Sources/Firelink"
+
+YTDLP_VERSION="2026.06.09"
+YTDLP_MACOS_ZIP_SHA256="62a3108d7c37090107f0bb9a2369b953b35e43f4bc76ab0ea87e4ab593c23ec7"
+
+DENO_VERSION="2.8.2"
+DENO_ARM64_ZIP_SHA256="02e5eb795c9f763772dfd081429cead9029e0a4a6aaff6d4e5f3ed6d2e94d361"
+DENO_X86_64_ZIP_SHA256="77cf27f835f1921e49434449675c57432c6314d54edc725e2474cc825546e206"
+
+FFMPEG_VERSION="8.1.1"
+FFMPEG_ARM64_URL="https://ffmpeg.martin-riedl.de/download/macos/arm64/1778761665_8.1.1/ffmpeg.zip"
+FFMPEG_ARM64_ZIP_SHA256="a05b1a47bb3ac89a95a55eec713f8bbb347051bb07015f3b7d08fb62ed81a21e"
+
+ARIA2_VERSION="1.37.0"
+ARIA2_BOTTLE_REVISION="2"
+ARIA2_RUNTIME_ID="$ARIA2_VERSION-$ARIA2_BOTTLE_REVISION-arm64-sonoma"
+ARIA2_BOTTLE_SHA256="8815b6b79395235863349628dc0d753bbee9069e99d94257b7646ffd85615623"
+CARES_VERSION="1.34.6"
+CARES_BOTTLE_SHA256="17f44048d8003b88231d69bac0408cf22be2f712ef8588d4933ff0811b92342c"
+LIBSSH2_VERSION="1.11.1_1"
+LIBSSH2_BOTTLE_SHA256="34927ad08cd265d32f1390a92d84451f85ab5b2f28101ca951da3d3e9df12047"
+OPENSSL_VERSION="3.6.2"
+OPENSSL_BOTTLE_SHA256="aaa5f4f3d87868ecd5f5fd6967da0c305eb335a58171faba193e9c7e39fbf35c"
+SQLITE_VERSION="3.53.0"
+SQLITE_BOTTLE_SHA256="36080e3273614fe3d606ff0bd5bb090ad33c19f186ba44c35807b8f97afa15be"
+GETTEXT_VERSION="1.0"
+GETTEXT_BOTTLE_SHA256="f9ea4eed738746ea4150a4f83e8dd11ca21ca3de5bb113995c25eec409bb5749"
+
+ARIA2_RUNTIME_SHA256="111b2f5ed760f1e1a2ec06117c4e8094fcde336ba16122dda1c5e7209bf1862d"
+CARES_RUNTIME_SHA256="86ceec6264753bfffb1562df22e81cbbed72d370105936ee083f3152c9dc1673"
+LIBCRYPTO_RUNTIME_SHA256="a13e280563c6eb85058f590f6f558fb20f54e171024f3b9b3637df140add1714"
+LIBINTL_RUNTIME_SHA256="7e6628118b26b58b57346f3f088b1f87b263c677736ade678f0aced5579ea357"
+LIBSQLITE_RUNTIME_SHA256="27da39c4cc96e7f43c8ed0134d2de6dd2fd36008dcb044c03aeee3eec9edc545"
+LIBSSH2_RUNTIME_SHA256="67cbce90dca26590a8a7627af8f4abccfd94f41cae48f7fa67a5f0cb98efc85b"
+LIBSSL_RUNTIME_SHA256="f5676ffe68757ea2629898c29bcee5f15982e06fe878bec4f70d159dd1b70452"
+
+mkdir -p "$SOURCE_DIR"
+
+sha256() {
+  shasum -a 256 "$1" | awk '{print $1}'
+}
+
+verify_sha256() {
+  local path="$1"
+  local expected="$2"
+  local actual
+  actual="$(sha256 "$path")"
+  if [[ "$actual" != "$expected" ]]; then
+    echo "Checksum mismatch for $path" >&2
+    echo "Expected: $expected" >&2
+    echo "Actual:   $actual" >&2
+    exit 1
+  fi
+}
+
+version_matches() {
+  local marker_path="$1"
+  local expected="$2"
+  [[ -f "$marker_path" ]] && [[ "$(tr -d '[:space:]' < "$marker_path")" == "$expected" ]]
+}
+
+fetch_homebrew_bottle() {
+  local repository="$1"
+  local digest="$2"
+  local output_path="$3"
+  local token
+
+  token="$(
+    curl -fsSL "https://ghcr.io/token?service=ghcr.io&scope=repository:homebrew/core/$repository:pull" |
+      python3 -c 'import json, sys; print(json.load(sys.stdin)["token"])'
+  )"
+  curl -fsSL \
+    -H "Authorization: Bearer $token" \
+    "https://ghcr.io/v2/homebrew/core/$repository/blobs/sha256:$digest" \
+    -o "$output_path"
+  verify_sha256 "$output_path" "$digest"
+}
+
+fetch_ytdlp() {
+  local executable="$SOURCE_DIR/yt-dlp"
+  local runtime="$SOURCE_DIR/_internal"
+  local marker="$SOURCE_DIR/yt-dlp-version.txt"
+
+  if [[ -x "$executable" ]] && [[ -d "$runtime" ]] && version_matches "$marker" "$YTDLP_VERSION"; then
+    return
+  fi
+
+  echo "Fetching yt-dlp $YTDLP_VERSION one-folder runtime..."
+  local temp_dir
+  temp_dir="$(mktemp -d)"
+  curl -fsSL \
+    "https://github.com/yt-dlp/yt-dlp/releases/download/$YTDLP_VERSION/yt-dlp_macos.zip" \
+    -o "$temp_dir/yt-dlp.zip"
+  verify_sha256 "$temp_dir/yt-dlp.zip" "$YTDLP_MACOS_ZIP_SHA256"
+  unzip -q -o "$temp_dir/yt-dlp.zip" -d "$temp_dir/runtime"
+
+  rm -rf "$runtime"
+  cp "$temp_dir/runtime/yt-dlp_macos" "$executable"
+  cp -R "$temp_dir/runtime/_internal" "$runtime"
+  touch "$runtime/.gitkeep"
+  chmod +x "$executable"
+  printf '%s\n' "$YTDLP_VERSION" > "$marker"
+  rm -rf "$temp_dir"
+}
+
+fetch_deno() {
+  local machine_arch
+  machine_arch="$(uname -m)"
+
+  local asset_arch
+  local expected_sha
+  case "$machine_arch" in
+    arm64)
+      asset_arch="aarch64"
+      expected_sha="$DENO_ARM64_ZIP_SHA256"
+      ;;
+    x86_64)
+      asset_arch="x86_64"
+      expected_sha="$DENO_X86_64_ZIP_SHA256"
+      ;;
+    *)
+      echo "Unsupported architecture for bundled Deno: $machine_arch" >&2
+      exit 1
+      ;;
+  esac
+
+  local executable="$SOURCE_DIR/deno"
+  local marker="$SOURCE_DIR/deno-version.txt"
+  if [[ -x "$executable" ]] && version_matches "$marker" "$DENO_VERSION-$machine_arch"; then
+    return
+  fi
+
+  echo "Fetching Deno $DENO_VERSION for $machine_arch..."
+  local temp_dir
+  temp_dir="$(mktemp -d)"
+  curl -fsSL \
+    "https://github.com/denoland/deno/releases/download/v$DENO_VERSION/deno-$asset_arch-apple-darwin.zip" \
+    -o "$temp_dir/deno.zip"
+  verify_sha256 "$temp_dir/deno.zip" "$expected_sha"
+  unzip -q -o "$temp_dir/deno.zip" -d "$temp_dir/runtime"
+  cp "$temp_dir/runtime/deno" "$executable"
+  chmod +x "$executable"
+  printf '%s\n' "$DENO_VERSION-$machine_arch" > "$marker"
+  rm -rf "$temp_dir"
+}
+
+fetch_ffmpeg() {
+  local executable="$SOURCE_DIR/ffmpeg"
+  local marker="$SOURCE_DIR/ffmpeg-version.txt"
+
+  if [[ "$(uname -m)" != "arm64" ]]; then
+    if [[ ! -x "$executable" ]]; then
+      echo "A local ffmpeg executable is required on non-ARM64 development hosts." >&2
+      exit 1
+    fi
+    return
+  fi
+
+  if [[ -x "$executable" ]] && version_matches "$marker" "$FFMPEG_VERSION-arm64"; then
+    return
+  fi
+
+  echo "Fetching FFmpeg $FFMPEG_VERSION for arm64..."
+  local temp_dir
+  temp_dir="$(mktemp -d)"
+  curl -fsSL "$FFMPEG_ARM64_URL" -o "$temp_dir/ffmpeg.zip"
+  verify_sha256 "$temp_dir/ffmpeg.zip" "$FFMPEG_ARM64_ZIP_SHA256"
+  unzip -q -o "$temp_dir/ffmpeg.zip" -d "$temp_dir/runtime"
+  cp "$temp_dir/runtime/ffmpeg" "$executable"
+  chmod +x "$executable"
+  printf '%s\n' "$FFMPEG_VERSION-arm64" > "$marker"
+  rm -rf "$temp_dir"
+}
+
+aria2_runtime_is_ready() {
+  local required_paths=(
+    "$SOURCE_DIR/aria2c"
+    "$SOURCE_DIR/aria2-cacert.pem"
+    "$SOURCE_DIR/aria2-libs/libcares.2.dylib"
+    "$SOURCE_DIR/aria2-libs/libcrypto.3.dylib"
+    "$SOURCE_DIR/aria2-libs/libintl.8.dylib"
+    "$SOURCE_DIR/aria2-libs/libsqlite3.dylib"
+    "$SOURCE_DIR/aria2-libs/libssh2.1.dylib"
+    "$SOURCE_DIR/aria2-libs/libssl.3.dylib"
+  )
+
+  version_matches "$SOURCE_DIR/aria2-version.txt" "$ARIA2_RUNTIME_ID" || return 1
+  [[ -x "$SOURCE_DIR/aria2c" ]] || return 1
+  [[ -d "$SOURCE_DIR/aria2-licenses" ]] || return 1
+
+  local path
+  for path in "${required_paths[@]}"; do
+    [[ -e "$path" ]] || return 1
+  done
+
+  [[ "$(sha256 "$SOURCE_DIR/aria2c")" == "$ARIA2_RUNTIME_SHA256" ]] || return 1
+  [[ "$(sha256 "$SOURCE_DIR/aria2-libs/libcares.2.dylib")" == "$CARES_RUNTIME_SHA256" ]] || return 1
+  [[ "$(sha256 "$SOURCE_DIR/aria2-libs/libcrypto.3.dylib")" == "$LIBCRYPTO_RUNTIME_SHA256" ]] || return 1
+  [[ "$(sha256 "$SOURCE_DIR/aria2-libs/libintl.8.dylib")" == "$LIBINTL_RUNTIME_SHA256" ]] || return 1
+  [[ "$(sha256 "$SOURCE_DIR/aria2-libs/libsqlite3.dylib")" == "$LIBSQLITE_RUNTIME_SHA256" ]] || return 1
+  [[ "$(sha256 "$SOURCE_DIR/aria2-libs/libssh2.1.dylib")" == "$LIBSSH2_RUNTIME_SHA256" ]] || return 1
+  [[ "$(sha256 "$SOURCE_DIR/aria2-libs/libssl.3.dylib")" == "$LIBSSL_RUNTIME_SHA256" ]] || return 1
+}
+
+fetch_aria2() {
+  if [[ "$(uname -m)" != "arm64" ]]; then
+    echo "The pinned aria2 runtime is currently available only for ARM64 macOS." >&2
+    exit 1
+  fi
+
+  if aria2_runtime_is_ready; then
+    return
+  fi
+
+  echo "Fetching aria2 $ARIA2_VERSION Homebrew ARM64 Sonoma runtime..."
+  local temp_dir
+  temp_dir="$(mktemp -d)"
+  local bottles_dir="$temp_dir/bottles"
+  local extracted_dir="$temp_dir/extracted"
+  local runtime_dir="$temp_dir/runtime"
+  local libraries_dir="$runtime_dir/aria2-libs"
+  local licenses_dir="$runtime_dir/aria2-licenses"
+  mkdir -p "$bottles_dir" "$extracted_dir" "$libraries_dir" "$licenses_dir"
+
+  fetch_homebrew_bottle "aria2" "$ARIA2_BOTTLE_SHA256" "$bottles_dir/aria2.tar.gz"
+  fetch_homebrew_bottle "c-ares" "$CARES_BOTTLE_SHA256" "$bottles_dir/c-ares.tar.gz"
+  fetch_homebrew_bottle "libssh2" "$LIBSSH2_BOTTLE_SHA256" "$bottles_dir/libssh2.tar.gz"
+  fetch_homebrew_bottle "openssl/3" "$OPENSSL_BOTTLE_SHA256" "$bottles_dir/openssl.tar.gz"
+  fetch_homebrew_bottle "sqlite" "$SQLITE_BOTTLE_SHA256" "$bottles_dir/sqlite.tar.gz"
+  fetch_homebrew_bottle "gettext" "$GETTEXT_BOTTLE_SHA256" "$bottles_dir/gettext.tar.gz"
+
+  local bottle
+  for bottle in "$bottles_dir"/*.tar.gz; do
+    tar -xzf "$bottle" -C "$extracted_dir"
+  done
+
+  cp "$extracted_dir/aria2/$ARIA2_VERSION"_"$ARIA2_BOTTLE_REVISION/bin/aria2c" "$runtime_dir/aria2c"
+  cp "$extracted_dir/c-ares/$CARES_VERSION/lib/libcares.2.19.5.dylib" "$libraries_dir/libcares.2.dylib"
+  cp "$extracted_dir/libssh2/$LIBSSH2_VERSION/lib/libssh2.1.dylib" "$libraries_dir/libssh2.1.dylib"
+  cp "$extracted_dir/openssl@3/$OPENSSL_VERSION/lib/libssl.3.dylib" "$libraries_dir/libssl.3.dylib"
+  cp "$extracted_dir/openssl@3/$OPENSSL_VERSION/lib/libcrypto.3.dylib" "$libraries_dir/libcrypto.3.dylib"
+  cp "$extracted_dir/sqlite/$SQLITE_VERSION/lib/libsqlite3.3.53.0.dylib" "$libraries_dir/libsqlite3.dylib"
+  cp "$extracted_dir/gettext/$GETTEXT_VERSION/lib/libintl.8.dylib" "$libraries_dir/libintl.8.dylib"
+  cp "$SOURCE_DIR/_internal/certifi/cacert.pem" "$runtime_dir/aria2-cacert.pem"
+
+  cp "$extracted_dir/aria2/$ARIA2_VERSION"_"$ARIA2_BOTTLE_REVISION/COPYING" "$licenses_dir/aria2-COPYING"
+  cp "$extracted_dir/c-ares/$CARES_VERSION/LICENSE.md" "$licenses_dir/c-ares-LICENSE.md"
+  cp "$extracted_dir/libssh2/$LIBSSH2_VERSION/COPYING" "$licenses_dir/libssh2-COPYING"
+  cp "$extracted_dir/openssl@3/$OPENSSL_VERSION/LICENSE.txt" "$licenses_dir/openssl-LICENSE.txt"
+  cp "$extracted_dir/gettext/$GETTEXT_VERSION/COPYING" "$licenses_dir/gettext-COPYING"
+  cp "$extracted_dir/sqlite/$SQLITE_VERSION/sbom.spdx.json" "$licenses_dir/sqlite-sbom.spdx.json"
+
+  install_name_tool \
+    -change "@@HOMEBREW_PREFIX@@/opt/sqlite/lib/libsqlite3.dylib" "@loader_path/aria2-libs/libsqlite3.dylib" \
+    -change "@@HOMEBREW_PREFIX@@/opt/openssl@3/lib/libssl.3.dylib" "@loader_path/aria2-libs/libssl.3.dylib" \
+    -change "@@HOMEBREW_PREFIX@@/opt/openssl@3/lib/libcrypto.3.dylib" "@loader_path/aria2-libs/libcrypto.3.dylib" \
+    -change "@@HOMEBREW_PREFIX@@/opt/libssh2/lib/libssh2.1.dylib" "@loader_path/aria2-libs/libssh2.1.dylib" \
+    -change "@@HOMEBREW_PREFIX@@/opt/c-ares/lib/libcares.2.dylib" "@loader_path/aria2-libs/libcares.2.dylib" \
+    -change "@@HOMEBREW_PREFIX@@/opt/gettext/lib/libintl.8.dylib" "@loader_path/aria2-libs/libintl.8.dylib" \
+    "$runtime_dir/aria2c"
+
+  local library
+  for library in "$libraries_dir"/*.dylib; do
+    install_name_tool -id "@loader_path/$(basename "$library")" "$library"
+  done
+
+  install_name_tool \
+    -change "@@HOMEBREW_PREFIX@@/opt/openssl@3/lib/libssl.3.dylib" "@loader_path/libssl.3.dylib" \
+    -change "@@HOMEBREW_PREFIX@@/opt/openssl@3/lib/libcrypto.3.dylib" "@loader_path/libcrypto.3.dylib" \
+    "$libraries_dir/libssh2.1.dylib"
+  install_name_tool \
+    -change "@@HOMEBREW_CELLAR@@/openssl@3/$OPENSSL_VERSION/lib/libcrypto.3.dylib" "@loader_path/libcrypto.3.dylib" \
+    "$libraries_dir/libssl.3.dylib"
+
+  chmod +x "$runtime_dir/aria2c"
+  for library in "$libraries_dir"/*.dylib; do
+    codesign --force --sign - "$library"
+  done
+  codesign --force --sign - "$runtime_dir/aria2c"
+
+  verify_sha256 "$runtime_dir/aria2c" "$ARIA2_RUNTIME_SHA256"
+  verify_sha256 "$libraries_dir/libcares.2.dylib" "$CARES_RUNTIME_SHA256"
+  verify_sha256 "$libraries_dir/libcrypto.3.dylib" "$LIBCRYPTO_RUNTIME_SHA256"
+  verify_sha256 "$libraries_dir/libintl.8.dylib" "$LIBINTL_RUNTIME_SHA256"
+  verify_sha256 "$libraries_dir/libsqlite3.dylib" "$LIBSQLITE_RUNTIME_SHA256"
+  verify_sha256 "$libraries_dir/libssh2.1.dylib" "$LIBSSH2_RUNTIME_SHA256"
+  verify_sha256 "$libraries_dir/libssl.3.dylib" "$LIBSSL_RUNTIME_SHA256"
+
+  if otool -L "$runtime_dir/aria2c" "$libraries_dir"/*.dylib | grep -Eq '(@@HOMEBREW|/opt/homebrew|/usr/local)'; then
+    echo "The prepared aria2 runtime still contains a Homebrew path." >&2
+    rm -rf "$temp_dir"
+    exit 1
+  fi
+  if ! vtool -show-build "$runtime_dir/aria2c" | grep -q 'minos 14.0'; then
+    echo "The pinned aria2 runtime no longer supports the app's macOS 14 deployment target." >&2
+    rm -rf "$temp_dir"
+    exit 1
+  fi
+  if [[ "$("$runtime_dir/aria2c" --version | head -n 1)" != "aria2 version $ARIA2_VERSION" ]]; then
+    echo "The prepared aria2 runtime failed its version check." >&2
+    rm -rf "$temp_dir"
+    exit 1
+  fi
+
+  rm -rf "$SOURCE_DIR/aria2-libs" "$SOURCE_DIR/aria2-licenses"
+  cp "$runtime_dir/aria2c" "$SOURCE_DIR/aria2c"
+  cp "$runtime_dir/aria2-cacert.pem" "$SOURCE_DIR/aria2-cacert.pem"
+  cp -R "$libraries_dir" "$SOURCE_DIR/aria2-libs"
+  cp -R "$licenses_dir" "$SOURCE_DIR/aria2-licenses"
+  printf '%s\n' "$ARIA2_RUNTIME_ID" > "$SOURCE_DIR/aria2-version.txt"
+  rm -rf "$temp_dir"
+}
+
+fetch_ytdlp
+fetch_deno
+fetch_ffmpeg
+fetch_aria2
+
+if command -v xattr >/dev/null; then
+  xattr -cr \
+    "$SOURCE_DIR/yt-dlp" \
+    "$SOURCE_DIR/_internal" \
+    "$SOURCE_DIR/deno" \
+    "$SOURCE_DIR/ffmpeg" \
+    "$SOURCE_DIR/aria2c" \
+    "$SOURCE_DIR/aria2-libs" 2>/dev/null || true
+fi
+
+echo "Media engines are ready:"
+echo "  yt-dlp $YTDLP_VERSION"
+echo "  Deno $DENO_VERSION"
+echo "  FFmpeg $FFMPEG_VERSION"
+echo "  aria2 $ARIA2_VERSION (Homebrew bottle revision $ARIA2_BOTTLE_REVISION)"
diff --git a/Scripts/verify.sh b/Scripts/verify.sh
index 2edbf8a..ed163e0 100755
--- a/Scripts/verify.sh
+++ b/Scripts/verify.sh
@@ -4,6 +4,25 @@ set -euo pipefail
 ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
 cd "$ROOT_DIR"
 
+"$ROOT_DIR/Scripts/fetch_media_engines.sh"
+
+ARIA2C="$ROOT_DIR/Sources/Firelink/aria2c"
+ARIA2_LIBS="$ROOT_DIR/Sources/Firelink/aria2-libs"
+test -x "$ARIA2C"
+test -f "$ROOT_DIR/Sources/Firelink/aria2-cacert.pem"
+test -d "$ARIA2_LIBS"
+"$ARIA2C" --version | grep -q '^aria2 version 1.37.0$'
+test "$(tr -d '[:space:]' < "$ROOT_DIR/Sources/Firelink/aria2-version.txt")" = "1.37.0-2-arm64-sonoma"
+lipo -archs "$ARIA2C" | grep -qx arm64
+vtool -show-build "$ARIA2C" | grep -q 'minos 14.0'
+for library in "$ARIA2_LIBS"/*.dylib; do
+  lipo -archs "$library" | grep -qx arm64
+done
+if otool -L "$ARIA2C" "$ARIA2_LIBS"/*.dylib | grep -Eq '(@@HOMEBREW|/opt/homebrew|/usr/local)'; then
+  echo "Bundled aria2 runtime contains a non-portable dependency path." >&2
+  exit 1
+fi
+
 swift build
 git diff --check
 python3 -m json.tool Extensions/Firefox/manifest.json >/dev/null
diff --git a/Sources/Firelink/Aria2DownloadEngine.swift b/Sources/Firelink/Aria2DownloadEngine.swift
index 34fa6b1..eb62824 100644
--- a/Sources/Firelink/Aria2DownloadEngine.swift
+++ b/Sources/Firelink/Aria2DownloadEngine.swift
@@ -57,7 +57,7 @@ final class Aria2DownloadEngine: Sendable {
         var errorDescription: String? {
             switch self {
             case .executableNotFound:
-                "aria2c was not found. Install it with `brew install aria2`, or bundle aria2c inside the app resources."
+                "The bundled aria2c runtime is missing. Reinstall Firelink or rebuild its media engines."
             case .launchFailed(let details):
                 "Could not start aria2c: \(details)"
             case .unsupportedProxy(let details):
@@ -73,20 +73,30 @@ final class Aria2DownloadEngine: Sendable {
     }
 
     static func findExecutable() -> URL? {
-        if let bundled = Bundle.main.url(forResource: "aria2c", withExtension: nil),
-           FileManager.default.isExecutableFile(atPath: bundled.path) {
+        bundledResource(named: "aria2c", executable: true)
+    }
+
+    static func certificateBundleURL() -> URL? {
+        bundledResource(named: "aria2-cacert.pem", executable: false)
+    }
+
+    private static func bundledResource(named name: String, executable: Bool) -> URL? {
+        func validResource(in bundle: Bundle) -> URL? {
+            guard let url = bundle.resourceURL?.appendingPathComponent(name) else { return nil }
+            let isValid = executable
+                ? FileManager.default.isExecutableFile(atPath: url.path)
+                : FileManager.default.fileExists(atPath: url.path)
+            return isValid ? url : nil
+        }
+
+        if let bundled = validResource(in: .main) {
             return bundled
         }
 
-        let candidates = [
-            "/opt/homebrew/bin/aria2c",
-            "/usr/local/bin/aria2c",
-            "/usr/bin/aria2c",
-            "/opt/local/bin/aria2c"
-        ]
-
-        if let found = candidates.first(where: { FileManager.default.isExecutableFile(atPath: $0) }) {
-            return URL(fileURLWithPath: found)
+        if Bundle.main.bundleURL.pathExtension.lowercased() != "app" {
+            #if SWIFT_PACKAGE
+            return validResource(in: .module)
+            #endif
         }
 
         return nil
@@ -303,7 +313,7 @@ final class Aria2DownloadEngine: Sendable {
             return Handle(processIdentifier: process.processIdentifier, rpcPort: rpcPort, rpcSecret: rpcSecret) {
                 completionMonitor.cancel()
                 if process.isRunning {
-                    process.terminate()
+                    ProcessTreeTerminator.terminate(process)
                 }
                 cleanupTempDir()
             }
@@ -323,7 +333,7 @@ final class Aria2DownloadEngine: Sendable {
                 if await completedDownloadStatus(rpcPort: rpcPort, rpcSecret: rpcSecret) {
                     completionGate.complete(.success(()))
                     if process.isRunning {
-                        process.terminate()
+                        ProcessTreeTerminator.terminate(process)
                     }
                     return
                 }
@@ -449,6 +459,10 @@ final class Aria2DownloadEngine: Sendable {
             arguments.append("--max-overall-download-limit=\(speedLimitKiBPerSecond)K")
         }
 
+        if let certificateBundleURL = Self.certificateBundleURL() {
+            arguments.append("--ca-certificate=\(certificateBundleURL.path)")
+        }
+
         arguments.append(contentsOf: try proxyArguments(for: item, configuration: proxyConfiguration))
         return arguments
     }
diff --git a/Sources/Firelink/DownloadController.swift b/Sources/Firelink/DownloadController.swift
index 979fc52..6e11d85 100644
--- a/Sources/Firelink/DownloadController.swift
+++ b/Sources/Firelink/DownloadController.swift
@@ -472,7 +472,7 @@ final class DownloadController: ObservableObject {
         }
 
         guard hasRunnableQueuedDownload else {
-            engineMessage = "aria2c is not installed. Run `brew install aria2` to enable downloads."
+            engineMessage = "The bundled aria2c runtime is missing. Reinstall Firelink or rebuild its media engines."
             return
         }
 
diff --git a/Sources/Firelink/FirelinkApp.swift b/Sources/Firelink/FirelinkApp.swift
index ae4c45a..86622b7 100644
--- a/Sources/Firelink/FirelinkApp.swift
+++ b/Sources/Firelink/FirelinkApp.swift
@@ -38,6 +38,7 @@ struct FirelinkApp: App {
                 .modifier(AppFontSizeModifier(fontSize: settings.appFontSize))
                 .task {
                     updateChecker.checkAutomaticallyIfNeeded()
+                    _ = await MediaEngineManager.shared.preparedBinaryPath(for: .ytDlp)
                 }
                 .onOpenURL { url in
                     let now = Date()
diff --git a/Sources/Firelink/MediaDownloadEngine.swift b/Sources/Firelink/MediaDownloadEngine.swift
index bcb304b..15faaa8 100644
--- a/Sources/Firelink/MediaDownloadEngine.swift
+++ b/Sources/Firelink/MediaDownloadEngine.swift
@@ -26,7 +26,7 @@ final class MediaDownloadEngine: @unchecked Sendable {
         messageUpdate: @escaping @Sendable (String) -> Void,
         completion: @escaping @Sendable (Result<URL, Error>) -> Void
     ) async throws -> Handle {
-        let ytDlpURL = await MediaEngineManager.shared.binaryPath(for: .ytDlp)
+        let ytDlpURL = await MediaEngineManager.shared.preparedBinaryPath(for: .ytDlp)
         let ffmpegURL = await MediaEngineManager.shared.binaryPath(for: .ffmpeg)
 
         guard let ytDlpURL, FileManager.default.isExecutableFile(atPath: ytDlpURL.path) else {
@@ -45,11 +45,12 @@ final class MediaDownloadEngine: @unchecked Sendable {
             "--newline",
             "--ffmpeg-location", ffmpegURL.path,
             "--no-check-formats",
+            "--socket-timeout", "20",
+            "--retries", "3",
+            "--extractor-retries", "3",
             "--fragment-retries", "10",
             "--retry-sleep", "0",
             "--skip-unavailable-fragments",
-            "--extractor-args", "youtube:player_client=tv,web",
-            "--extractor-args", "youtube:skip=webpage",
             "--compat-options", "no-youtube-unavailable-videos",
             "-o", item.destinationPath
         ]
@@ -71,7 +72,8 @@ final class MediaDownloadEngine: @unchecked Sendable {
             to: &arguments,
             cookieSource: cookieSource,
             credentials: item.credentials,
-            transferOptions: item.transferOptions
+            transferOptions: item.transferOptions,
+            preferredDenoURL: ytDlpURL.deletingLastPathComponent().appendingPathComponent("deno")
         )
 
         if let proxyURI = proxyConfiguration.customProxyURI, proxyConfiguration.mode == .custom {
@@ -82,7 +84,11 @@ final class MediaDownloadEngine: @unchecked Sendable {
             arguments.append(contentsOf: ["--limit-rate", "\(speedLimitKiBPerSecond)K"])
         }
 
-        appendParallelDownloadArguments(to: &arguments, connectionsPerServer: item.connectionsPerServer)
+        appendParallelDownloadArguments(
+            to: &arguments,
+            item: item,
+            speedLimitKiBPerSecond: speedLimitKiBPerSecond
+        )
 
         arguments.append(item.url.absoluteString)
         process.arguments = arguments
@@ -134,7 +140,7 @@ final class MediaDownloadEngine: @unchecked Sendable {
             if let tempConfigDir {
                 try? FileManager.default.removeItem(at: tempConfigDir)
             }
-            readGroup.notify(queue: .global()) {
+            let complete: @Sendable () -> Void = {
                 if finishedProcess.terminationStatus == 0 {
                     completionGate.complete(.success(Self.resolvedOutputURL(for: item, tracker: outputPathTracker)))
                 } else {
@@ -142,6 +148,12 @@ final class MediaDownloadEngine: @unchecked Sendable {
                     completionGate.complete(.failure(EngineError.launchFailed(Self.cleanErrorMessage(errorString, status: finishedProcess.terminationStatus))))
                 }
             }
+            readGroup.notify(queue: .global(), execute: complete)
+            DispatchQueue.global().asyncAfter(deadline: .now() + 1) {
+                outputPipe.fileHandleForReading.readabilityHandler = nil
+                errorPipe.fileHandleForReading.readabilityHandler = nil
+                complete()
+            }
         }
 
         var didRun = false
@@ -158,7 +170,7 @@ final class MediaDownloadEngine: @unchecked Sendable {
 
         return Handle(cancel: {
             if process.isRunning {
-                process.terminate()
+                ProcessTreeTerminator.terminate(process)
             }
         })
     }
@@ -212,12 +224,37 @@ final class MediaDownloadEngine: @unchecked Sendable {
         return message
     }
 
-    private func appendParallelDownloadArguments(to arguments: inout [String], connectionsPerServer: Int) {
-        let connections = min(max(connectionsPerServer, 1), 16)
+    private func appendParallelDownloadArguments(
+        to arguments: inout [String],
+        item: DownloadItem,
+        speedLimitKiBPerSecond: Int?
+    ) {
+        let connections = min(max(item.connectionsPerServer, 1), 16)
         guard connections > 1 else { return }
 
         arguments.append(contentsOf: ["--concurrent-fragments", "\(connections)"])
-        // Use yt-dlp's native concurrent downloader instead of aria2c to ensure progress parsing works via stdout
+        let largeDirectDownloadThreshold: Int64 = 128 * 1024 * 1024
+        guard item.isAudioOnlyMedia != true,
+              (item.sizeBytes ?? 0) >= largeDirectDownloadThreshold,
+              speedLimitKiBPerSecond == nil,
+              let aria2URL = Aria2DownloadEngine.findExecutable() else {
+            return
+        }
+
+        let aria2Connections = min(connections, 8)
+        let certificateArgument = Aria2DownloadEngine.certificateBundleURL().map {
+            " --ca-certificate=\(Self.shellQuoted($0.path))"
+        } ?? ""
+        arguments.append(contentsOf: [
+            "--downloader", aria2URL.path,
+            "--downloader", "dash,m3u8:native",
+            "--downloader-args",
+            "aria2c:-x\(aria2Connections) -s\(aria2Connections) -k1M --file-allocation=none --summary-interval=1\(certificateArgument)"
+        ])
+    }
+
+    private static func shellQuoted(_ value: String) -> String {
+        "'\(value.replacingOccurrences(of: "'", with: "'\"'\"'"))'"
     }
 }
 
diff --git a/Sources/Firelink/MediaEngineManager.swift b/Sources/Firelink/MediaEngineManager.swift
index 68b8351..f307f91 100644
--- a/Sources/Firelink/MediaEngineManager.swift
+++ b/Sources/Firelink/MediaEngineManager.swift
@@ -1,5 +1,6 @@
 import Foundation
 import Combine
+import Darwin
 
 enum AddonState: Equatable, Sendable {
     case notInstalled
@@ -25,23 +26,34 @@ final class MediaEngineManager: ObservableObject {
 
     @Published var ytDlpState: AddonState = .notInstalled
     @Published var ffmpegState: AddonState = .notInstalled
+    private var ytDlpPreparationTask: Task<URL?, Never>?
 
     private init() {
         checkLocalInstallation()
-        Task.detached { [weak self] in
-            await self?.prewarmYtDlp()
+        Task { [weak self] in
+            _ = await self?.preparedBinaryPath(for: .ytDlp)
         }
     }
 
-    nonisolated private func prewarmYtDlp() async {
-        guard let path = await MainActor.run(body: { binaryPath(for: .ytDlp) }) else { return }
-        let process = Process()
-        process.executableURL = path
-        process.arguments = ["--version"]
-        process.standardOutput = nil
-        process.standardError = nil
-        try? process.run()
-        process.waitUntilExit()
+    func preparedBinaryPath(for addon: AddonType) async -> URL? {
+        guard addon == .ytDlp else { return binaryPath(for: addon) }
+
+        if let ytDlpPreparationTask {
+            return await ytDlpPreparationTask.value
+        }
+
+        guard let bundledURL = binaryPath(for: .ytDlp) else { return nil }
+        let runtimeVersion = bundledRuntimeVersion(near: bundledURL)
+        let task = Task<URL?, Never>.detached(priority: .userInitiated) {
+            let executableURL = Self.installStableYtDlpRuntime(
+                bundledExecutableURL: bundledURL,
+                version: runtimeVersion
+            ) ?? bundledURL
+            Self.prewarm(executableURL)
+            return executableURL
+        }
+        ytDlpPreparationTask = task
+        return await task.value
     }
 
     func binaryPath(for addon: AddonType) -> URL? {
@@ -62,6 +74,144 @@ final class MediaEngineManager: ObservableObject {
         return nil
     }
 
+    private func bundledRuntimeVersion(near executableURL: URL) -> String {
+        let versionURL = executableURL.deletingLastPathComponent()
+            .appendingPathComponent("yt-dlp-version.txt")
+        if let version = try? String(contentsOf: versionURL, encoding: .utf8)
+            .trimmingCharacters(in: .whitespacesAndNewlines),
+           !version.isEmpty {
+            return version
+        }
+
+        return Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String ?? "unknown"
+    }
+
+    nonisolated private static func installStableYtDlpRuntime(
+        bundledExecutableURL: URL,
+        version: String
+    ) -> URL? {
+        let fileManager = FileManager.default
+        let bundledDirectory = bundledExecutableURL.deletingLastPathComponent()
+        let bundledInternalURL = bundledDirectory.appendingPathComponent("_internal", isDirectory: true)
+        let bundledDenoURL = bundledDirectory.appendingPathComponent("deno")
+        let hasBundledDeno = fileManager.isExecutableFile(atPath: bundledDenoURL.path)
+
+        guard fileManager.fileExists(atPath: bundledInternalURL.path) else {
+            return bundledExecutableURL
+        }
+
+        guard let applicationSupportURL = fileManager.urls(
+            for: .applicationSupportDirectory,
+            in: .userDomainMask
+        ).first else {
+            return bundledExecutableURL
+        }
+
+        let safeVersion = version.replacingOccurrences(
+            of: #"[^A-Za-z0-9._-]"#,
+            with: "_",
+            options: .regularExpression
+        )
+        let enginesURL = applicationSupportURL
+            .appendingPathComponent("Firelink", isDirectory: true)
+            .appendingPathComponent("MediaEngines", isDirectory: true)
+            .appendingPathComponent("yt-dlp", isDirectory: true)
+        let runtimeURL = enginesURL.appendingPathComponent(safeVersion, isDirectory: true)
+        let executableURL = runtimeURL.appendingPathComponent("yt-dlp")
+        let internalURL = runtimeURL.appendingPathComponent("_internal", isDirectory: true)
+        let denoURL = runtimeURL.appendingPathComponent("deno")
+
+        if fileManager.isExecutableFile(atPath: executableURL.path),
+           fileManager.fileExists(atPath: internalURL.path),
+           !hasBundledDeno || fileManager.isExecutableFile(atPath: denoURL.path) {
+            return executableURL
+        }
+
+        let temporaryURL = enginesURL.appendingPathComponent(
+            ".install-\(UUID().uuidString)",
+            isDirectory: true
+        )
+
+        do {
+            try fileManager.createDirectory(at: enginesURL, withIntermediateDirectories: true)
+            try fileManager.createDirectory(at: temporaryURL, withIntermediateDirectories: true)
+            try fileManager.copyItem(
+                at: bundledExecutableURL,
+                to: temporaryURL.appendingPathComponent("yt-dlp")
+            )
+            try fileManager.copyItem(
+                at: bundledInternalURL,
+                to: temporaryURL.appendingPathComponent("_internal", isDirectory: true)
+            )
+            if hasBundledDeno {
+                try fileManager.copyItem(
+                    at: bundledDenoURL,
+                    to: temporaryURL.appendingPathComponent("deno")
+                )
+            }
+            removeTransportAttributesRecursively(at: temporaryURL)
+
+            if fileManager.fileExists(atPath: runtimeURL.path) {
+                try fileManager.removeItem(at: runtimeURL)
+            }
+            try fileManager.moveItem(at: temporaryURL, to: runtimeURL)
+            return executableURL
+        } catch {
+            try? fileManager.removeItem(at: temporaryURL)
+            return bundledExecutableURL
+        }
+    }
+
+    nonisolated private static func removeTransportAttributesRecursively(at rootURL: URL) {
+        removeTransportAttributes(at: rootURL)
+
+        guard let enumerator = FileManager.default.enumerator(
+            at: rootURL,
+            includingPropertiesForKeys: nil,
+            options: [],
+            errorHandler: nil
+        ) else {
+            return
+        }
+
+        for case let itemURL as URL in enumerator {
+            removeTransportAttributes(at: itemURL)
+        }
+    }
+
+    nonisolated private static func removeTransportAttributes(at url: URL) {
+        url.withUnsafeFileSystemRepresentation { path in
+            guard let path else { return }
+            removexattr(path, "com.apple.quarantine", 0)
+            removexattr(path, "com.apple.provenance", 0)
+        }
+    }
+
+    nonisolated private static func prewarm(_ executableURL: URL) {
+        runVersionCommand(executableURL)
+
+        let denoURL = executableURL.deletingLastPathComponent().appendingPathComponent("deno")
+        if FileManager.default.isExecutableFile(atPath: denoURL.path) {
+            runVersionCommand(denoURL)
+        }
+    }
+
+    nonisolated private static func runVersionCommand(_ executableURL: URL) {
+        let process = Process()
+        process.executableURL = executableURL
+        process.arguments = ["--version"]
+        process.standardOutput = nil
+        process.standardError = nil
+        process.standardInput = nil
+
+        do {
+            try process.run()
+            process.waitUntilExit()
+        } catch {
+            return
+        }
+    }
+
     func checkLocalInstallation() {
         for addon in AddonType.allCases {
             if binaryPath(for: addon) != nil {
diff --git a/Sources/Firelink/MediaExtractionEngine.swift b/Sources/Firelink/MediaExtractionEngine.swift
index d61fb53..a6a1f76 100644
--- a/Sources/Firelink/MediaExtractionEngine.swift
+++ b/Sources/Firelink/MediaExtractionEngine.swift
@@ -87,20 +87,20 @@ enum MediaExtractionEngine {
         if let cached = metadataCache.object(forKey: url as NSURL), Date().timeIntervalSince(cached.date) < 300 {
             return (cached.metadata, cached.options)
         }
-        guard let ytDlpURL = await MediaEngineManager.shared.binaryPath(for: .ytDlp),
+        guard let ytDlpURL = await MediaEngineManager.shared.preparedBinaryPath(for: .ytDlp),
               FileManager.default.isExecutableFile(atPath: ytDlpURL.path) else {
             throw ExtractionError.processFailed("yt-dlp binary not found.")
         }
         let ytDlpPath = ytDlpURL.path
 
         var args = [
-            "-J", 
-            "--no-warnings", 
-            "--ignore-no-formats-error", 
-            "--no-playlist", 
+            "-J",
+            "--no-warnings",
+            "--no-playlist",
             "--no-check-formats",
-            "--extractor-args", "youtube:player_client=tv,web",
-            "--extractor-args", "youtube:skip=webpage",
+            "--socket-timeout", "20",
+            "--retries", "3",
+            "--extractor-retries", "3",
             "--compat-options", "no-youtube-unavailable-videos"
         ]
 
@@ -113,7 +113,13 @@ enum MediaExtractionEngine {
             args.append(contentsOf: ["--proxy", proxyURI])
         }
 
-        let tempConfigDir = appendCommonArguments(to: &args, cookieSource: cookieSource, credentials: credentials, transferOptions: transferOptions)
+        let tempConfigDir = appendCommonArguments(
+            to: &args,
+            cookieSource: cookieSource,
+            credentials: credentials,
+            transferOptions: transferOptions,
+            preferredDenoURL: cachedDenoURL(near: ytDlpURL)
+        )
         defer {
             if let tempConfigDir {
                 try? FileManager.default.removeItem(at: tempConfigDir)
@@ -144,13 +150,14 @@ enum MediaExtractionEngine {
         to args: inout [String],
         cookieSource: BrowserCookieSource,
         credentials: DownloadCredentials?,
-        transferOptions: DownloadTransferOptions
+        transferOptions: DownloadTransferOptions,
+        preferredDenoURL: URL? = nil
     ) -> URL? {
         if let browserName = cookieSource.ytDlpBrowserName {
             args.append(contentsOf: ["--cookies-from-browser", browserName])
         }
 
-        appendJavaScriptRuntimeArguments(to: &args)
+        appendJavaScriptRuntimeArguments(to: &args, preferredDenoURL: preferredDenoURL)
 
         for header in transferOptions.requestHeaders.map(\.normalized) where !header.isEmpty {
             args.append(contentsOf: ["--add-header", header.headerLine])
@@ -175,9 +182,14 @@ enum MediaExtractionEngine {
         return tempConfigDir
     }
 
-    private static func appendJavaScriptRuntimeArguments(to args: inout [String]) {
+    private static func appendJavaScriptRuntimeArguments(
+        to args: inout [String],
+        preferredDenoURL: URL?
+    ) {
         var runtimes: [String] = []
-        if let denoPath = executablePath(named: "deno", candidates: [
+        if let denoPath = executablePath(at: preferredDenoURL) ??
+            bundledExecutablePath(named: "deno") ??
+            executablePath(named: "deno", candidates: [
             "/opt/homebrew/bin/deno",
             "/usr/local/bin/deno"
         ]) {
@@ -197,6 +209,36 @@ enum MediaExtractionEngine {
         }
     }
 
+    private static func cachedDenoURL(near ytDlpURL: URL) -> URL? {
+        let denoURL = ytDlpURL.deletingLastPathComponent().appendingPathComponent("deno")
+        return FileManager.default.isExecutableFile(atPath: denoURL.path) ? denoURL : nil
+    }
+
+    private static func executablePath(at url: URL?) -> String? {
+        guard let url, FileManager.default.isExecutableFile(atPath: url.path) else {
+            return nil
+        }
+        return url.path
+    }
+
+    private static func bundledExecutablePath(named name: String) -> String? {
+        if let bundled = Bundle.main.url(forResource: name, withExtension: nil),
+           FileManager.default.isExecutableFile(atPath: bundled.path) {
+            return bundled.path
+        }
+
+        if Bundle.main.bundleURL.pathExtension.lowercased() != "app" {
+            #if SWIFT_PACKAGE
+            if let bundled = Bundle.module.url(forResource: name, withExtension: nil),
+               FileManager.default.isExecutableFile(atPath: bundled.path) {
+                return bundled.path
+            }
+            #endif
+        }
+
+        return nil
+    }
+
     private static func executablePath(named name: String, candidates: [String]) -> String? {
         var safeCandidates = candidates
         safeCandidates.append(contentsOf: [
@@ -501,6 +543,9 @@ private final class YTDLPMetadataProcess: @unchecked Sendable {
 
             do {
                 try process.run()
+                if Task.isCancelled {
+                    self.terminate()
+                }
                 outputPipe.fileHandleForWriting.closeFile()
                 errorPipe.fileHandleForWriting.closeFile()
             } catch {
@@ -515,14 +560,6 @@ private final class YTDLPMetadataProcess: @unchecked Sendable {
     private func terminate() {
         let p = lock.withLock { self.process }
         guard let p, p.isRunning else { return }
-        
-        p.terminate()
-        
-        Task.detached {
-            try? await Task.sleep(nanoseconds: 500_000_000)
-            if p.isRunning {
-                kill(p.processIdentifier, SIGKILL)
-            }
-        }
+        ProcessTreeTerminator.terminate(p)
     }
 }
diff --git a/Sources/Firelink/ProcessTreeTerminator.swift b/Sources/Firelink/ProcessTreeTerminator.swift
new file mode 100644
index 0000000..312598c
--- /dev/null
+++ b/Sources/Firelink/ProcessTreeTerminator.swift
@@ -0,0 +1,53 @@
+import Foundation
+import Darwin
+
+enum ProcessTreeTerminator {
+    static func terminate(_ process: Process, forceAfter delay: TimeInterval = 0.5) {
+        let rootPID = process.processIdentifier
+        guard rootPID > 0 else { return }
+
+        let processIDs = descendants(of: rootPID) + [rootPID]
+        signal(processIDs.reversed(), with: SIGTERM)
+
+        DispatchQueue.global(qos: .utility).asyncAfter(deadline: .now() + delay) {
+            signal(processIDs.reversed(), with: SIGKILL)
+        }
+    }
+
+    private static func descendants(of rootPID: pid_t) -> [pid_t] {
+        var result: [pid_t] = []
+        var pending = directChildren(of: rootPID)
+
+        while let processID = pending.popLast() {
+            result.append(processID)
+            pending.append(contentsOf: directChildren(of: processID))
+        }
+
+        return result
+    }
+
+    private static func directChildren(of processID: pid_t) -> [pid_t] {
+        var capacity = 32
+
+        while capacity <= 4096 {
+            var processIDs = [pid_t](repeating: 0, count: capacity)
+            let count = processIDs.withUnsafeMutableBytes { buffer in
+                proc_listchildpids(processID, buffer.baseAddress, Int32(buffer.count))
+            }
+
+            guard count > 0 else { return [] }
+            if count < capacity {
+                return Array(processIDs.prefix(Int(count))).filter { $0 > 0 }
+            }
+            capacity *= 2
+        }
+
+        return []
+    }
+
+    private static func signal<S: Sequence>(_ processIDs: S, with signal: Int32) where S.Element == pid_t {
+        for processID in processIDs where processID > 0 {
+            kill(processID, signal)
+        }
+    }
+}
diff --git a/Sources/Firelink/Settings/EngineSettingsPane.swift b/Sources/Firelink/Settings/EngineSettingsPane.swift
index abdf5b6..c3983db 100644
--- a/Sources/Firelink/Settings/EngineSettingsPane.swift
+++ b/Sources/Firelink/Settings/EngineSettingsPane.swift
@@ -34,7 +34,7 @@ struct EngineSettingsPane: View {
                 Text("Core Downloader (Aria2)")
             } footer: {
                 if executableURL == nil {
-                    Text("Install aria2 with Homebrew or ensure it is bundled inside the app resources.")
+                    Text("The bundled aria2 runtime is missing. Reinstall Firelink or rebuild its media engines.")
                         .foregroundStyle(.red)
                 } else {
                     Text("Handles core HTTP/FTP and BitTorrent downloads.")