Added download settings and optimized the downloader system with concurrency.

ptlinux/cli.py

@@ -23,6 +23,7 @@ from ptdiag.logs import (
 from . import __version__
 from .command import CommandError, CommandOutcome, CommandRunner
 from .depot import (
+	DownloadOptions,
 	SyncProgress,
 	read_cached_depot_launch_catalog,
 	select_depot_start_option,
@@ -561,6 +562,7 @@ def _native_update(
 	"""Use the native verified depot client for normal installs and updates."""
 
 	settings = _load_or_default_settings(paths, persist=not dry_run)
+	download_options = _configured_download_options(settings)
 	runner = _runner(paths, "native-update", dry_run)
 	with _operation_guard(paths, "native-update", dry_run):
 		_print_operation_status(as_json, 1, 3, "Checking local game files…")
@@ -581,6 +583,11 @@ def _native_update(
 			quarantine_unmanaged=verify_import,
 			dry_run=dry_run,
 			progress=None if as_json else _print_sync_progress,
+			**(
+				{"download_options": download_options}
+				if download_options is not None
+				else {}
+			),
 		)
 		if verify_import and not dry_run:
 			mark_game_import_verified(
@@ -620,6 +627,7 @@ def _wine_update(
 		raise LauncherError("Wine, Wineboot, and Winetricks are required; run doctor")
 	runner = _runner(paths, "update", dry_run)
 	settings = _load_or_default_settings(paths, persist=not dry_run)
+	download_options = _configured_download_options(settings)
 	with _operation_guard(paths, "update", dry_run):
 		configure_launcher_prefix(
 			paths,
@@ -647,6 +655,11 @@ def _wine_update(
 				repair=True,
 				quarantine_unmanaged=True,
 				progress=None if as_json else _print_sync_progress,
+				**(
+					{"download_options": download_options}
+					if download_options is not None
+					else {}
+				),
 			)
 			mark_game_import_verified(
 				paths,
@@ -677,6 +690,20 @@ def _print_sync_progress(progress: SyncProgress) -> None:
 	print(f"PROGRESS {json.dumps(asdict(progress), sort_keys=True)}", flush=True)
 
 
+def _configured_download_options(settings: Settings) -> DownloadOptions | None:
+	if (
+		settings.download_speed_limit_bytes_per_second is None
+		and not settings.low_bandwidth_mode
+	):
+		return None
+	return DownloadOptions(
+		bandwidth_limit_bytes_per_second=(
+			settings.download_speed_limit_bytes_per_second
+		),
+		low_bandwidth=settings.low_bandwidth_mode,
+	)
+
+
 def _print_operation_status(
 	as_json: bool,
 	step: int,

ptlinux/depot.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 from base64 import b64decode
 from binascii import Error as BinAsciiError
+from collections import deque
 from concurrent.futures import FIRST_COMPLETED, Future, ThreadPoolExecutor, wait
 from dataclasses import asdict, dataclass
 from datetime import datetime
@@ -35,8 +36,15 @@ FALLBACK_SERVERS = (
 READ_SIZE = 128 * 1024
 HASH_READ_SIZE = 1024 * 1024
 DOWNLOAD_WORKERS = 8
+DOWNLOAD_INITIAL_WORKERS = DOWNLOAD_WORKERS
+LOW_BANDWIDTH_WORKERS = 2
+LOW_BANDWIDTH_BYTES_PER_SECOND = 5_000_000
 DOWNLOAD_RETRY_DELAYS_SECONDS = (1.0, 2.0, 4.0, 8.0, 16.0)
 PROGRESS_UPDATE_INTERVAL_SECONDS = 0.075
+ADAPTIVE_EVALUATION_INTERVAL_SECONDS = 1.0
+ADAPTIVE_RETRY_WINDOW_SECONDS = 15.0
+ADAPTIVE_RETRY_RECOVERY_SECONDS = 5.0
+TRANSFER_RATE_WINDOW_SECONDS = 5.0
 MAX_CREATE_IF_MISSING_BYTES = 16 * 1024 * 1024
 MAX_LINE_ENDING_RECOVERY_BYTES = 1024 * 1024
 UNMANAGED_EXECUTABLE_SUFFIXES = frozenset(
@@ -88,6 +96,275 @@ class _RetryableDownloadError(DepotError):
 		self.discard_partial = discard_partial
 
 
+@dataclass(frozen=True)
+class DownloadOptions:
+	"""User-selected limits around the adaptive depot scheduler."""
+
+	bandwidth_limit_bytes_per_second: int | None = None
+	low_bandwidth: bool = False
+	minimum_workers: int = 1
+	maximum_workers: int | None = None
+
+	def __post_init__(self) -> None:
+		if not isinstance(self.low_bandwidth, bool):
+			raise ValueError("low_bandwidth must be a boolean")
+		if (
+			self.bandwidth_limit_bytes_per_second is not None
+			and (
+				isinstance(self.bandwidth_limit_bytes_per_second, bool)
+				or self.bandwidth_limit_bytes_per_second <= 0
+			)
+		):
+			raise ValueError("bandwidth limit must be positive or None")
+		if isinstance(self.minimum_workers, bool) or self.minimum_workers <= 0:
+			raise ValueError("minimum download workers must be positive")
+		if self.maximum_workers is not None and (
+			isinstance(self.maximum_workers, bool) or self.maximum_workers <= 0
+		):
+			raise ValueError("maximum download workers must be positive or None")
+		if (
+			self.maximum_workers is not None
+			and self.minimum_workers > self.maximum_workers
+		):
+			raise ValueError("minimum download workers exceed the maximum")
+		if self.low_bandwidth and self.minimum_workers > LOW_BANDWIDTH_WORKERS:
+			raise ValueError("low-bandwidth minimum workers exceed its worker cap")
+
+	@property
+	def effective_bandwidth_limit(self) -> int | None:
+		configured = self.bandwidth_limit_bytes_per_second
+		if not self.low_bandwidth:
+			return configured
+		return min(
+			configured if configured is not None else LOW_BANDWIDTH_BYTES_PER_SECOND,
+			LOW_BANDWIDTH_BYTES_PER_SECOND,
+		)
+
+	@property
+	def effective_maximum_workers(self) -> int:
+		configured = self.maximum_workers or DOWNLOAD_WORKERS
+		if self.low_bandwidth:
+			configured = min(configured, LOW_BANDWIDTH_WORKERS)
+		return max(self.minimum_workers, configured)
+
+
+@dataclass(frozen=True)
+class DownloadTelemetry:
+	"""One internal measurement produced while retrieving a depot file."""
+
+	kind: str
+	file: str
+	server: str
+	attempt: int
+	latency_seconds: float | None = None
+	bytes_written: int = 0
+	write_seconds: float = 0.0
+	reason: str | None = None
+
+
+DownloadObserver = Callable[[DownloadTelemetry], None]
+
+
+class BandwidthLimiter:
+	"""Thread-safe aggregate byte-rate limiter with a one-chunk burst allowance."""
+
+	def __init__(
+		self,
+		bytes_per_second: int,
+		*,
+		clock: Callable[[], float] = time.monotonic,
+		sleeper: Callable[[float], None] = time.sleep,
+	) -> None:
+		if isinstance(bytes_per_second, bool) or bytes_per_second <= 0:
+			raise ValueError("bandwidth limit must be positive")
+		self.bytes_per_second = bytes_per_second
+		self._clock = clock
+		self._sleeper = sleeper
+		self._lock = threading.Lock()
+		self._next_available_at = clock()
+
+	def consume(self, byte_count: int) -> None:
+		"""Wait until this newly received chunk's aggregate reservation begins.
+
+		The network read happens before this call. Reserving the chunk's *start*
+		keeps all workers under one aggregate rate without charging again for time
+		already spent receiving it. The first chunk is the bucket's burst allowance.
+		"""
+
+		if byte_count < 0:
+			raise ValueError("byte count must not be negative")
+		if byte_count == 0:
+			return
+		with self._lock:
+			now = self._clock()
+			start = max(now, self._next_available_at)
+			self._next_available_at = start + (byte_count / self.bytes_per_second)
+			delay = start - now
+		if delay > 0:
+			self._sleeper(delay)
+
+
+class AdaptiveConcurrencyController:
+	"""Select a bounded worker target from live network, host, and plan data."""
+
+	def __init__(
+		self,
+		options: DownloadOptions,
+		*,
+		clock: Callable[[], float] = time.monotonic,
+		cpu_load: Callable[[], float | None] | None = None,
+	) -> None:
+		self.options = options
+		self._clock = clock
+		self._cpu_load = cpu_load or _normalized_cpu_load
+		self._lock = threading.Lock()
+		self._target = max(
+			options.minimum_workers,
+			min(DOWNLOAD_INITIAL_WORKERS, options.effective_maximum_workers),
+		)
+		self._last_evaluation = clock()
+		self._transferred_bytes = 0
+		self._transfer_samples: deque[tuple[float, int]] = deque(
+			[(self._last_evaluation, 0)]
+		)
+		self._response_samples: deque[tuple[float, float]] = deque()
+		self._retry_samples: deque[float] = deque()
+		self._retry_count = 0
+		self._handled_retry_count = 0
+		self._last_retry_at: float | None = None
+		self._latency_seconds: float | None = None
+		self._disk_samples: deque[tuple[float, int, float]] = deque()
+
+	def record_response(self, latency_seconds: float) -> None:
+		if latency_seconds < 0:
+			return
+		now = self._clock()
+		with self._lock:
+			self._response_samples.append((now, latency_seconds))
+			self._prune_health_samples(now)
+			if self._latency_seconds is None:
+				self._latency_seconds = latency_seconds
+			else:
+				self._latency_seconds = (
+					(self._latency_seconds * 0.75) + (latency_seconds * 0.25)
+				)
+
+	def record_retry(self) -> None:
+		now = self._clock()
+		with self._lock:
+			self._retry_count += 1
+			self._retry_samples.append(now)
+			self._last_retry_at = now
+			self._prune_health_samples(now)
+
+	def record_chunk(self, byte_count: int, write_seconds: float) -> None:
+		if byte_count <= 0:
+			return
+		now = self._clock()
+		with self._lock:
+			self._transferred_bytes += byte_count
+			self._transfer_samples.append((now, self._transferred_bytes))
+			_prune_transfer_samples(self._transfer_samples, now)
+			self._disk_samples.append((now, byte_count, max(0.0, write_seconds)))
+			self._prune_disk_samples(now)
+
+	def _prune_health_samples(self, now: float) -> None:
+		cutoff = now - ADAPTIVE_RETRY_WINDOW_SECONDS
+		while self._response_samples and self._response_samples[0][0] < cutoff:
+			self._response_samples.popleft()
+		while self._retry_samples and self._retry_samples[0] < cutoff:
+			self._retry_samples.popleft()
+
+	def _prune_disk_samples(self, now: float) -> None:
+		cutoff = now - TRANSFER_RATE_WINDOW_SECONDS
+		while self._disk_samples and self._disk_samples[0][0] < cutoff:
+			self._disk_samples.popleft()
+
+	def target_workers(self, remaining_files: int, remaining_bytes: int) -> int:
+		"""Return the next target; active workers are allowed to drain naturally."""
+
+		if remaining_files <= 0:
+			return 0
+		maximum = min(self.options.effective_maximum_workers, remaining_files)
+		minimum = min(self.options.minimum_workers, maximum)
+		with self._lock:
+			self._target = min(maximum, max(minimum, self._target))
+			now = self._clock()
+			average_file_size = remaining_bytes / max(1, remaining_files)
+			if now - self._last_evaluation < ADAPTIVE_EVALUATION_INTERVAL_SECONDS:
+				return self._target
+			self._last_evaluation = now
+			_prune_transfer_samples(self._transfer_samples, now)
+			self._prune_health_samples(now)
+			self._prune_disk_samples(now)
+			rate = _sample_rate(self._transfer_samples)
+			attempts = len(self._response_samples) + len(self._retry_samples)
+			error_rate = len(self._retry_samples) / attempts if attempts else 0.0
+			latency = self._latency_seconds
+			disk_bytes = sum(sample[1] for sample in self._disk_samples)
+			disk_seconds = sum(sample[2] for sample in self._disk_samples)
+			disk_rate = (
+				disk_bytes / disk_seconds
+				if disk_seconds > 0
+				else None
+			)
+			try:
+				cpu_load = self._cpu_load()
+			except (OSError, ValueError):
+				cpu_load = None
+
+			new_retries = self._retry_count - self._handled_retry_count
+			if new_retries:
+				self._handled_retry_count = self._retry_count
+				if error_rate >= 0.12 and self._target > minimum:
+					backoff = min(2, new_retries)
+					self._target = max(minimum, self._target - backoff)
+				return self._target
+
+			resource_constrained = (
+				(cpu_load is not None and cpu_load >= 0.90)
+				or (
+					rate is not None
+					and disk_rate is not None
+					and disk_rate < rate * 0.75
+				)
+			)
+			if resource_constrained and self._target > minimum:
+				self._target -= 1
+				return self._target
+
+			limit = self.options.effective_bandwidth_limit
+			limit_saturated = (
+				limit is not None and rate is not None and rate >= limit * 0.90
+			)
+			healthy = (
+				(cpu_load is None or cpu_load < 0.80)
+				and (
+					rate is None
+					or disk_rate is None
+					or disk_rate >= rate
+				)
+			)
+			retry_recovery_pending = (
+				self._last_retry_at is not None
+				and now - self._last_retry_at < ADAPTIVE_RETRY_RECOVERY_SECONDS
+			)
+			if (
+				healthy
+				and not retry_recovery_pending
+				and not limit_saturated
+				and self._target < maximum
+			):
+				# Parallel requests hide CDN round-trip time and are especially useful
+				# for this depot's large population of small files.
+				step = 2 if (
+					(latency is not None and latency >= 0.75)
+					or average_file_size <= 512 * 1024
+				) else 1
+				self._target = min(maximum, self._target + step)
+			return min(maximum, max(minimum, self._target))
+
+
 @dataclass(frozen=True)
 class DepotFile:
 	"""One exact file in the published depot build."""
@@ -258,6 +535,14 @@ class SyncProgress:
 	bytes_total: int
 	current_file: str | None
 	bytes_transferred: int = 0
+	bytes_remaining: int = 0
+	transfer_rate_bytes_per_second: float | None = None
+	eta_seconds: float | None = None
+	current_server: str | None = None
+	retry_count: int = 0
+	retry_reason: str | None = None
+	active_workers: int = 0
+	target_workers: int = 0
 
 
 @dataclass(frozen=True)
@@ -315,6 +600,7 @@ class DepotClient:
 		opener: HttpOpener = urlopen,
 		retry_delays: tuple[float, ...] = DOWNLOAD_RETRY_DELAYS_SECONDS,
 		sleeper: Callable[[float], None] = time.sleep,
+		download_observer: DownloadObserver | None = None,
 	) -> None:
 		if timeout_seconds <= 0:
 			raise ValueError("timeout_seconds must be positive")
@@ -325,6 +611,24 @@ class DepotClient:
 		self._retry_delays = retry_delays
 		self._sleeper = sleeper
 		self._candidate_servers: tuple[str, ...] = ()
+		self._download_observer = download_observer
+		self._bandwidth_limiter: BandwidthLimiter | None = None
+
+	@property
+	def download_observer(self) -> DownloadObserver | None:
+		return self._download_observer
+
+	@download_observer.setter
+	def download_observer(self, observer: DownloadObserver | None) -> None:
+		self._download_observer = observer
+
+	@property
+	def bandwidth_limiter(self) -> BandwidthLimiter | None:
+		return self._bandwidth_limiter
+
+	@bandwidth_limiter.setter
+	def bandwidth_limiter(self, limiter: BandwidthLimiter | None) -> None:
+		self._bandwidth_limiter = limiter
 
 	def fetch_snapshot(self, *, preferred_region: str = "Europe") -> DepotSnapshot:
 		"""Fetch the live depot and build manifests, trying trusted regional fallbacks."""
@@ -379,11 +683,21 @@ class DepotClient:
 					attempt_server,
 					file,
 					destination,
+					attempt=attempt_index + 1,
 					progress=progress,
 				)
 				return
 			except _RetryableDownloadError as exc:
 				last_error = exc
+				self._notify_download(
+					DownloadTelemetry(
+						kind="retry",
+						file=file.path,
+						server=attempt_server,
+						attempt=attempt_index + 1,
+						reason=str(exc),
+					)
+				)
 				if exc.discard_partial:
 					temporary.unlink(missing_ok=True)
 				if attempt_index >= len(self._retry_delays):
@@ -407,6 +721,7 @@ class DepotClient:
 		file: DepotFile,
 		destination: Path,
 		*,
+		attempt: int,
 		progress: Callable[[int], None] | None,
 	) -> None:
 		temporary = _download_partial_path(destination)
@@ -455,6 +770,15 @@ class DepotClient:
 			headers["Range"] = f"bytes={requested_offset}-"
 		url = _file_url(server, file)
 		request = Request(url, headers=headers, method="GET")
+		self._notify_download(
+			DownloadTelemetry(
+				kind="request",
+				file=file.path,
+				server=server,
+				attempt=attempt,
+			)
+		)
+		request_started_at = time.monotonic()
 		try:
 			response = self._opener(request, timeout=self.timeout_seconds)
 		except HTTPError as exc:
@@ -470,6 +794,15 @@ class DepotClient:
 			raise _RetryableDownloadError(
 				f"could not connect to {server} for {file.path}: {exc}"
 			) from exc
+		self._notify_download(
+			DownloadTelemetry(
+				kind="response",
+				file=file.path,
+				server=server,
+				attempt=attempt,
+				latency_seconds=max(0.0, time.monotonic() - request_started_at),
+			)
+		)
 
 		try:
 			append = False
@@ -528,8 +861,24 @@ class DepotClient:
 								f"download exceeds expected size for {file.path}",
 								discard_partial=True,
 							)
+						if self._bandwidth_limiter is not None:
+							self._bandwidth_limiter.consume(len(chunk))
 						digest.update(chunk)
+						write_started_at = time.monotonic()
 						handle.write(chunk)
+						self._notify_download(
+							DownloadTelemetry(
+								kind="chunk",
+								file=file.path,
+								server=server,
+								attempt=attempt,
+								bytes_written=len(chunk),
+								write_seconds=max(
+									0.0,
+									time.monotonic() - write_started_at,
+								),
+							)
+						)
 						if progress is not None:
 							progress(written)
 			except _RetryableDownloadError:
@@ -559,6 +908,16 @@ class DepotClient:
 			except (OSError, HTTPException):
 				pass
 
+	def _notify_download(self, event: DownloadTelemetry) -> None:
+		observer = self._download_observer
+		if observer is not None:
+			# noinspection PyBroadException
+			try:
+				observer(event)
+			except Exception:
+				# Telemetry must never weaken verified download behavior.
+				pass
+
 	def _get_json(self, url: str) -> Mapping[str, object]:
 		request = Request(url, headers=_headers(), method="GET")
 		try:
@@ -642,6 +1001,7 @@ def sync_managed_game(
 	dry_run: bool = False,
 	progress: ProgressCallback | None = None,
 	client: DepotClient | None = None,
+	download_options: DownloadOptions | None = None,
 ) -> DepotSyncResult:
 	"""Synchronize the managed game directory using only official public data."""
 
@@ -676,7 +1036,14 @@ def sync_managed_game(
 		)
 
 	root = _prepare_game_root(paths.source_game, create=True)
-	_download_plan(depot_client, snapshot, root, plan, progress)
+	_download_plan(
+		depot_client,
+		snapshot,
+		root,
+		plan,
+		progress,
+		download_options or DownloadOptions(),
+	)
 	deleted = _apply_deletions(root, plan.deletes)
 	created = _apply_create_if_missing(root, snapshot.create_if_missing)
 	result = _sync_result(
@@ -814,6 +1181,7 @@ def _download_plan(
 	root: Path,
 	plan: UpdatePlan,
 	progress: ProgressCallback | None,
+	options: DownloadOptions,
 ) -> None:
 	if not plan.downloads:
 		return
@@ -821,10 +1189,22 @@ def _download_plan(
 	lock = threading.Lock()
 	emit_lock = threading.Lock()
 	current_bytes: dict[str, int] = {}
+	current_servers: dict[str, str] = {}
 	completed_files = 0
 	completed_bytes = 0
 	transferred_bytes = 0
+	retry_count = 0
+	retry_reason: str | None = None
+	active_workers = 0
+	target_workers = 0
 	last_progress_emitted_at = 0.0
+	started_at = time.monotonic()
+	transfer_samples: deque[tuple[float, int]] = deque([(started_at, 0)])
+	controller = AdaptiveConcurrencyController(options)
+	bandwidth_limit = options.effective_bandwidth_limit
+	limiter = BandwidthLimiter(bandwidth_limit) if bandwidth_limit is not None else None
+	previous_observer = client.download_observer
+	previous_limiter = client.bandwidth_limiter
 
 	def emit_download_progress(
 		current_file: str,
@@ -847,27 +1227,72 @@ def _download_plan(
 				return
 			last_progress_emitted_at = now
 			with lock:
+				bytes_completed = min(
+					plan.bytes_total,
+					completed_bytes + sum(current_bytes.values()),
+				)
+				_prune_transfer_samples(transfer_samples, now)
+				transfer_rate = _sample_rate(transfer_samples)
+				bytes_remaining = max(0, plan.bytes_total - bytes_completed)
+				eta_seconds = (
+					bytes_remaining / transfer_rate
+					if transfer_rate is not None and transfer_rate > 0
+					else None
+				)
 				event = SyncProgress(
 					"downloading",
 					completed_files,
 					len(plan.downloads),
-					completed_bytes + sum(current_bytes.values()),
+					bytes_completed,
 					plan.bytes_total,
 					current_file,
 					transferred_bytes,
+					bytes_remaining,
+					transfer_rate,
+					eta_seconds,
+					current_servers.get(
+						current_file,
+						_server_display_name(depot_snapshot.server),
+					),
+					retry_count,
+					retry_reason,
+					active_workers,
+					target_workers,
 				)
 			progress(event)
 
+	def observe_download(event: DownloadTelemetry) -> None:
+		nonlocal transferred_bytes, retry_count, retry_reason
+		if event.kind == "response" and event.latency_seconds is not None:
+			controller.record_response(event.latency_seconds)
+		elif event.kind == "retry":
+			controller.record_retry()
+		elif event.kind == "chunk":
+			controller.record_chunk(event.bytes_written, event.write_seconds)
+
+		force = event.kind == "retry"
+		if event.kind in {"request", "response", "retry", "chunk"}:
+			with lock:
+				current_servers[event.file] = _server_display_name(event.server)
+				if event.kind == "chunk":
+					transferred_bytes += event.bytes_written
+					now = time.monotonic()
+					transfer_samples.append((now, transferred_bytes))
+					_prune_transfer_samples(transfer_samples, now)
+				if event.kind == "retry":
+					retry_count += 1
+					retry_reason = event.reason
+		if previous_observer is not None:
+			previous_observer(event)
+		if event.kind != "chunk":
+			emit_download_progress(event.file, force=force)
+
 	def download(planned_download: PlannedDownload) -> None:
 		target = _safe_target(root, planned_download.file.path)
 		_ensure_target_parent(root, target)
 
 		def report_file_bytes(written: int) -> None:
-			nonlocal transferred_bytes
 			with lock:
-				previous = current_bytes.get(planned_download.file.path)
-				if previous is not None and written > previous:
-					transferred_bytes += written - previous
 				current_bytes[planned_download.file.path] = written
 			emit_download_progress(planned_download.file.path)
 
@@ -878,26 +1303,45 @@ def _download_plan(
 			progress=report_file_bytes if progress is not None else None,
 		)
 
-	worker_count = min(DOWNLOAD_WORKERS, len(plan.downloads))
+	maximum_workers = min(options.effective_maximum_workers, len(plan.downloads))
-	remaining_items = iter(plan.downloads)
+	# Start large transfers first so they overlap the small-file request workload
-	with ThreadPoolExecutor(max_workers=worker_count) as executor:
+	# instead of becoming a single-connection tail at the end of an install.
+	remaining_items: deque[PlannedDownload] = deque(
+		sorted(plan.downloads, key=lambda item: item.file.size, reverse=True)
+	)
+	client.download_observer = observe_download
+	client.bandwidth_limiter = limiter
+	try:
+		with ThreadPoolExecutor(max_workers=maximum_workers) as executor:
 			future_items: dict[Future[None], PlannedDownload] = {}
 
-		def submit_next() -> bool:
+			def submit_until(worker_target: int) -> None:
+				nonlocal active_workers, target_workers
+				with lock:
+					target_workers = worker_target
+				while remaining_items and len(future_items) < worker_target:
+					next_item = remaining_items.popleft()
+					with lock:
+						active_workers += 1
 					try:
-				next_item = next(remaining_items)
+						submitted_future = executor.submit(download, next_item)
-			except StopIteration:
+					except BaseException:
-				return False
+						with lock:
-			future_items[executor.submit(download, next_item)] = next_item
+							active_workers -= 1
-			return True
+						remaining_items.appendleft(next_item)
+						raise
+					future_items[submitted_future] = next_item
 
 			try:
-			for _worker in range(worker_count):
+				initial_target = controller.target_workers(
-				if not submit_next():
+					len(remaining_items),
-					break
+					plan.bytes_total,
+				)
+				submit_until(initial_target)
 				while future_items:
 					done, _pending = wait(
 						tuple(future_items),
+						timeout=ADAPTIVE_EVALUATION_INTERVAL_SECONDS,
 						return_when=FIRST_COMPLETED,
 					)
 					completed_items: list[PlannedDownload] = []
@@ -907,6 +1351,7 @@ def _download_plan(
 						completed_items.append(completed_item)
 					for completed_item in completed_items:
 						with lock:
+							active_workers -= 1
 							completed_files += 1
 							completed_bytes += completed_item.file.size
 							current_bytes.pop(completed_item.file.path, None)
@@ -915,12 +1360,27 @@ def _download_plan(
 							completed_item.file.path,
 							force=is_final_download,
 						)
-				for _item in completed_items:
+						with lock:
-					submit_next()
+							current_servers.pop(completed_item.file.path, None)
+					with lock:
+						in_progress_bytes = sum(current_bytes.values())
+					remaining_file_count = len(remaining_items) + len(future_items)
+					remaining_byte_count = max(
+						0,
+						plan.bytes_total - completed_bytes - in_progress_bytes,
+					)
+					next_target = controller.target_workers(
+						remaining_file_count,
+						remaining_byte_count,
+					)
+					submit_until(next_target)
 			except BaseException:
 				for future in future_items:
 					future.cancel()
 				raise
+	finally:
+		client.download_observer = previous_observer
+		client.bandwidth_limiter = previous_limiter
 
 
 def _apply_deletions(root: Path, relative_paths: Iterable[str]) -> int:
@@ -1415,6 +1875,44 @@ def _content_range(value: str | None) -> tuple[int, int, int]:
 	return start, end, total
 
 
+def _normalized_cpu_load() -> float | None:
+	"""Return one-minute runnable load normalized by the available CPU count."""
+
+	try:
+		load = os.getloadavg()[0]
+	except (AttributeError, OSError):
+		return None
+	processors = os.cpu_count()
+	if processors is None or processors <= 0:
+		return None
+	return max(0.0, load / processors)
+
+
+def _prune_transfer_samples(
+	samples: deque[tuple[float, int]],
+	now: float,
+) -> None:
+	cutoff = now - TRANSFER_RATE_WINDOW_SECONDS
+	while len(samples) > 2 and samples[1][0] <= cutoff:
+		samples.popleft()
+
+
+def _sample_rate(samples: deque[tuple[float, int]]) -> float | None:
+	if len(samples) < 2:
+		return None
+	first_time, first_bytes = samples[0]
+	last_time, last_bytes = samples[-1]
+	elapsed = last_time - first_time
+	if elapsed <= 0 or last_bytes < first_bytes:
+		return None
+	return (last_bytes - first_bytes) / elapsed
+
+
+def _server_display_name(server: str) -> str:
+	parsed = urlparse(server if "://" in server else f"//{server}")
+	return parsed.hostname or server.split("/", 1)[0]
+
+
 def _headers() -> dict[str, str]:
 	return {"User-Agent": f"PT-Linux/{__version__} (+https://pristontale.eu/)"}
 
@@ -1451,5 +1949,6 @@ def _emit_progress(
 				bytes_completed,
 				bytes_total,
 				current_file,
+				bytes_remaining=max(0, bytes_total - bytes_completed),
 			)
 		)

ptlinux/news.py

@@ -95,6 +95,17 @@ def fetch_news_image(
 	return _fetch_png_image(article.image_url, cache_path, timeout_seconds, opener)
 
 
+def read_cached_news_image(
+	article: NewsArticle,
+	cache_directory: Path,
+) -> bytes | None:
+	"""Read article artwork without contacting the network."""
+
+	if article.image_url is None:
+		return None
+	return _read_png(_image_cache_path(cache_directory, article))
+
+
 def fetch_official_logo(
 	cache_path: Path,
 	*,
@@ -106,6 +117,12 @@ def fetch_official_logo(
 	return _fetch_png_image(OFFICIAL_LOGO_URL, cache_path, timeout_seconds, opener)
 
 
+def read_cached_official_logo(cache_path: Path) -> bytes | None:
+	"""Read the official logo cache without contacting the network."""
+
+	return _read_png(cache_path)
+
+
 def _fetch_png_image(
 	url: str,
 	cache_path: Path,

ptlinux/settings.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 from dataclasses import asdict, dataclass, fields, replace
 import json
+import math
 import os
 from pathlib import Path
 import secrets
@@ -41,11 +42,19 @@ class Settings:
 	proton_sync: str = "auto"
 	proton_path: str | None = None
 	game_source: str | None = None
+	download_speed_limit_mbps: float | None = None
+	low_bandwidth_mode: bool = False
 
 	@property
 	def source_override(self) -> Path | None:
 		return Path(self.game_source).expanduser().resolve() if self.game_source else None
 
+	@property
+	def download_speed_limit_bytes_per_second(self) -> int | None:
+		if self.download_speed_limit_mbps is None:
+			return None
+		return round(self.download_speed_limit_mbps * 1_000_000)
+
 
 def load_settings(paths: AppPaths) -> Settings:
 	value = _read_settings_object(paths.settings_file)
@@ -153,6 +162,11 @@ def _settings_from_object(value: dict[str, object]) -> Settings:
 		proton_sync=_string(value, "proton_sync", "auto"),
 		proton_path=_optional_string(value, "proton_path"),
 		game_source=_optional_string(value, "game_source"),
+		download_speed_limit_mbps=_optional_positive_number(
+			value,
+			"download_speed_limit_mbps",
+		),
+		low_bandwidth_mode=_boolean(value, "low_bandwidth_mode", False),
 	)
 	_validate(settings)
 	return settings
@@ -250,6 +264,17 @@ def _validate(settings: Settings) -> None:
 		raise ValueError(f"unsupported runtime selection: {settings.runtime}")
 	if settings.proton_sync not in {"auto", "fsync", "esync"}:
 		raise ValueError(f"unsupported Proton synchronization mode: {settings.proton_sync}")
+	if (
+		settings.download_speed_limit_mbps is not None
+		and (
+			not math.isfinite(settings.download_speed_limit_mbps)
+			or settings.download_speed_limit_mbps <= 0
+			or settings.download_speed_limit_mbps > 10_000
+		)
+	):
+		raise ValueError(
+			"download_speed_limit_mbps must be greater than 0 and at most 10000, or null"
+		)
 
 def _boolean(value: dict[str, object], key: str, default: bool) -> bool:
 	item = value.get(key, default)
@@ -274,4 +299,16 @@ def _optional_string(value: dict[str, object], key: str) -> str | None:
 	return item
 
 
+def _optional_positive_number(value: dict[str, object], key: str) -> float | None:
+	item = value.get(key)
+	if item is None:
+		return None
+	if isinstance(item, bool) or not isinstance(item, (int, float)):
+		raise ValueError(f"{key} must be null or a positive number")
+	number = float(item)
+	if not math.isfinite(number) or number <= 0:
+		raise ValueError(f"{key} must be null or a positive number")
+	return number
+
+
 _SETTINGS_FIELD_NAMES = frozenset(field.name for field in fields(Settings))

ptlinux/ui.py

@@ -63,6 +63,8 @@ from .news import (
 	fetch_official_logo,
 	read_cached_broadcast,
 	read_cached_news,
+	read_cached_news_image,
+	read_cached_official_logo,
 )
 from .overlay import RuntimeCompatibility, inspect_runtime_compatibility
 from .paths import AppPaths
@@ -120,6 +122,14 @@ PROTON_SYNC_LABELS: dict[str, str] = {
 	"Fsync": "fsync",
 	"Esync": "esync",
 }
+DOWNLOAD_SPEED_PRESETS_MBPS: dict[str, float | None] = {
+	"Unlimited": None,
+	"5 MB/s": 5.0,
+	"10 MB/s": 10.0,
+	"25 MB/s": 25.0,
+	"50 MB/s": 50.0,
+}
+DOWNLOAD_SPEED_CUSTOM_LABEL = "Custom…"
 NEWS_THREE_COLUMN_WIDTH = 900
 NEWS_TWO_COLUMN_WIDTH = 620
 STACKED_CONTROLS_WIDTH = 860
@@ -305,6 +315,62 @@ def setting_value(label: str, choices: Mapping[str, str]) -> str:
 		raise ValueError(f"unsupported setting choice: {label}") from error
 
 
+def download_speed_setting_label(limit_mbps: float | None) -> str:
+	for label, preset in DOWNLOAD_SPEED_PRESETS_MBPS.items():
+		if preset == limit_mbps:
+			return label
+	return DOWNLOAD_SPEED_CUSTOM_LABEL
+
+
+def download_speed_setting_value(label: str, custom_value: str) -> float | None:
+	if label in DOWNLOAD_SPEED_PRESETS_MBPS:
+		return DOWNLOAD_SPEED_PRESETS_MBPS[label]
+	if label != DOWNLOAD_SPEED_CUSTOM_LABEL:
+		raise ValueError(f"unsupported download speed choice: {label}")
+	try:
+		value = float(custom_value.strip())
+	except ValueError as error:
+		raise ValueError("custom download speed must be a number in MB/s") from error
+	if not math.isfinite(value) or value <= 0 or value > 10_000:
+		raise ValueError(
+			"custom download speed must be greater than 0 and at most 10000 MB/s"
+		)
+	return value
+
+
+def download_activity_metadata(
+	*,
+	current_server: str | None,
+	retry_count: int,
+	retry_reason: str | None,
+	active_workers: int,
+	target_workers: int,
+) -> str:
+	"""Render compact download details for the existing activity heading."""
+
+	if retry_count < 0 or active_workers < 0 or target_workers < 0:
+		raise ValueError("download activity counts must not be negative")
+	parts: list[str] = []
+	if current_server:
+		parts.append(f"CDN: {_ellipsize(current_server, 28)}")
+	if target_workers:
+		parts.append(f"Workers: {active_workers}/{target_workers}")
+	retry_text = f"Retries: {retry_count}"
+	if retry_reason:
+		retry_text += f" ({_ellipsize(retry_reason, 26, keep_tail=True)})"
+	parts.append(retry_text)
+	return " · ".join(parts)
+
+
+def _ellipsize(value: str, limit: int, *, keep_tail: bool = False) -> str:
+	normalized = " ".join(value.split())
+	if len(normalized) <= limit:
+		return normalized
+	if keep_tail:
+		return f"…{normalized[-(limit - 1):]}"
+	return f"{normalized[:limit - 1]}…"
+
+
 def call_optional(callback: Callable[..., None] | None, *arguments: object) -> None:
 	if callback is not None:
 		callback(*arguments)
@@ -1813,6 +1879,18 @@ def run_dashboard(paths: AppPaths) -> None:
 	progress_text = tk.StringVar(value="Click Play to start your journey")
 	speed_text = tk.StringVar(value="")
 	client_activity_text = tk.StringVar(value="")
+	download_context_text = tk.StringVar(value="")
+	activity_meta_text = tk.StringVar(value="")
+
+	def refresh_activity_meta_text() -> None:
+		activity_meta_text.set(
+			download_context_text.get() or client_activity_text.get()
+		)
+
+	def set_download_context_text(value: str) -> None:
+		download_context_text.set(value)
+		refresh_activity_meta_text()
+
 	activity_heading = ttk.Frame(activity_copy, style="Surface.TFrame")
 	activity_heading.pack(fill="x")
 	ttk.Label(
@@ -1822,7 +1900,7 @@ def run_dashboard(paths: AppPaths) -> None:
 	).pack(side="left", anchor="w")
 	ttk.Label(
 		activity_heading,
-		textvariable=client_activity_text,
+		textvariable=activity_meta_text,
 		style="Muted.TLabel",
 	).pack(side="right", anchor="e")
 	progress_bar = ttk.Progressbar(
@@ -1839,7 +1917,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		progress_details,
 		textvariable=speed_text,
 		style="Speed.TLabel",
-		width=15,
+		width=28,
 		anchor="e",
 	).pack(side="right")
 	ttk.Label(
@@ -1857,6 +1935,24 @@ def run_dashboard(paths: AppPaths) -> None:
 	).pack(side="left", fill="y", padx=(0, 8))
 	server_status_content = ttk.Frame(server_status_row, style="Surface.TFrame")
 	server_status_content.pack(side="left", fill="y", anchor="w")
+	log_toggle = tk.Button(
+		server_status_row,
+		text=">_",
+		background="#191311",
+		foreground="#f8fafc",
+		activebackground="#24170f",
+		activeforeground="#ffffff",
+		font=("Monospace", 8, "bold"),
+		padx=3,
+		pady=1,
+		borderwidth=0,
+		highlightthickness=1,
+		highlightbackground="#191311",
+		highlightcolor="#f4bd61",
+		relief="flat",
+		takefocus=True,
+	)
+	log_toggle.pack(side="right", anchor="e", padx=(8, 0))
 	server_status_debug_text = tk.StringVar(value="")
 	ttk.Label(
 		server_status_row,
@@ -1969,26 +2065,6 @@ def run_dashboard(paths: AppPaths) -> None:
 	)
 	log.pack(fill="both", expand=True, padx=10, pady=10)
 	activity_window.withdraw()
-	activity_footer = ttk.Frame(frame, style="Root.TFrame")
-	activity_footer.pack(fill="x", pady=(3, 0))
-	log_toggle = tk.Button(
-		activity_footer,
-		text=">_",
-		background="#0c0908",
-		foreground="#f8fafc",
-		activebackground="#24170f",
-		activeforeground="#ffffff",
-		font=("Monospace", 8, "bold"),
-		padx=3,
-		pady=2,
-		borderwidth=0,
-		highlightthickness=2,
-		highlightbackground="#0c0908",
-		highlightcolor="#f4bd61",
-		relief="flat",
-		takefocus=True,
-	)
-	log_toggle.pack(side="left", anchor="sw")
 
 	events: queue.Queue[tuple[str, object]] = queue.Queue()
 	progress_updates = ProgressCoalescer()
@@ -2111,28 +2187,67 @@ def run_dashboard(paths: AppPaths) -> None:
 		if phase == "manifest":
 			transfer_rate.reset()
 			speed_text.set("")
+			set_download_context_text("")
 			set_operation_stage(1, 3, "Checking official CDN manifests…")
 			return
 		progress_bar.stop()
 		progress_bar.configure(mode="determinate")
 		if bytes_total:
 			progress_bar.configure(maximum=bytes_total, value=min(bytes_completed, bytes_total))
+			bytes_remaining = _as_int(event.get("bytes_remaining"))
+			if "bytes_remaining" not in event:
+				bytes_remaining = max(0, bytes_total - bytes_completed)
+			percent = min(100, round((bytes_completed / bytes_total) * 100))
 			operation_progress_detail = (
-				f"{files_completed}/{files_total} files · "
+				f"{percent}% · {files_completed:,}/{files_total:,} files · "
-				f"{_format_bytes(bytes_completed)} / {_format_bytes(bytes_total)}"
+				f"{_format_bytes(bytes_completed)} / {_format_bytes(bytes_total)} · "
+				f"{_format_bytes(bytes_remaining)} remaining"
 			)
 			if phase == "downloading":
 				bytes_transferred = _as_int(event.get("bytes_transferred"))
-				rate = transfer_rate.update(bytes_transferred)
+				estimated_rate = transfer_rate.update(bytes_transferred)
-				speed_text.set(format_transfer_rate(rate) if rate is not None else "0 B/s")
+				reported_rate = _as_float(
+					event.get("transfer_rate_bytes_per_second")
+				)
+				rate = reported_rate if reported_rate is not None else estimated_rate
+				eta_seconds = _as_float(event.get("eta_seconds"))
+				if eta_seconds is None and rate is not None and rate > 0:
+					eta_seconds = bytes_remaining / rate
+				speed_text.set(
+					f"{format_transfer_rate(rate) if rate is not None else '0 B/s'} · "
+					f"ETA {format_eta(eta_seconds)}"
+				)
+				current_server = event.get("current_server")
+				active_workers = _as_int(event.get("active_workers"))
+				target_workers = _as_int(event.get("target_workers"))
+				retry_reason = event.get("retry_reason")
+				set_download_context_text(
+					download_activity_metadata(
+						current_server=(
+							current_server
+							if isinstance(current_server, str) and current_server
+							else None
+						),
+						retry_count=_as_int(event.get("retry_count")),
+						retry_reason=(
+							retry_reason
+							if isinstance(retry_reason, str) and retry_reason
+							else None
+						),
+						active_workers=active_workers,
+						target_workers=target_workers,
+					)
+				)
 			else:
 				transfer_rate.reset()
 				speed_text.set("")
+				set_download_context_text("")
 		else:
 			progress_bar.configure(maximum=3, value=3)
 			operation_progress_detail = "Game files are already up to date."
 			transfer_rate.reset()
 			speed_text.set("")
+			set_download_context_text("")
 		progress_text.set(activity_text())
 		if isinstance(current_file, str) and current_file:
 			status.set(
@@ -2159,6 +2274,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		operation_progress_detail = None
 		transfer_rate.reset()
 		speed_text.set("")
+		set_download_context_text("")
 		progress_bar.stop()
 		progress_bar.configure(
 			mode="determinate",
@@ -2370,6 +2486,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		progress_updates.clear()
 		transfer_rate.reset()
 		speed_text.set("")
+		set_download_context_text("")
 		set_busy(True)
 		status.set(label)
 		progress_text.set("Waiting for the operation to report progress…")
@@ -2971,7 +3088,11 @@ def run_dashboard(paths: AppPaths) -> None:
 			)
 
 		def worker(news_article: NewsArticle) -> None:
-			image = fetch_news_image(news_article, paths.news_image_cache)
+			image = (
+				read_cached_news_image(news_article, paths.news_image_cache)
+				if startup_settings.low_bandwidth_mode
+				else fetch_news_image(news_article, paths.news_image_cache)
+			)
 			events.put(("news_image", (news_article.id, image)))
 
 		for article in image_articles:
@@ -3087,7 +3208,11 @@ def run_dashboard(paths: AppPaths) -> None:
 
 	def load_official_logo() -> None:
 		def worker() -> None:
-			image = fetch_official_logo(paths.logo_cache)
+			image = (
+				read_cached_official_logo(paths.logo_cache)
+				if startup_settings.low_bandwidth_mode
+				else fetch_official_logo(paths.logo_cache)
+			)
 			events.put(("logo_image", image))
 
 		threading.Thread(target=worker, name="ptlinux-logo", daemon=True).start()
@@ -3529,6 +3654,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		latest_installation_status = installation
 		additional_client_ready = game_clients.running_count > 0 and installation.installed
 		client_activity_text.set(game_client_activity_text(game_clients.running_count))
+		refresh_activity_meta_text()
 		play_button.configure(
 			text="PLAY" if additional_client_ready else installation.action.value
 		)
@@ -3685,15 +3811,41 @@ def run_dashboard(paths: AppPaths) -> None:
 					)
 				events.put(("version", snapshot))
 
-		threading.Thread(target=broadcast_worker, name="ptlinux-broadcast", daemon=True).start()
+		if startup_settings.low_bandwidth_mode:
-		threading.Thread(target=news_worker, name="ptlinux-news", daemon=True).start()
+			append_log(
-		threading.Thread(target=patches_worker, name="ptlinux-patches", daemon=True).start()
+				"Low-bandwidth mode: using cached news, broadcasts, patch notes, "
+				"and artwork."
+			)
+			for component, message in (
+				("broadcast", "Cached broadcast ready"),
+				("news", "Cached news ready"),
+				("patches", "Cached patch notes ready"),
+				("launcher_update", "Cached launcher update status ready"),
+			):
+				mark_startup_component_ready(component, message)
+		else:
+			threading.Thread(
+				target=broadcast_worker,
+				name="ptlinux-broadcast",
+				daemon=True,
+			).start()
+			threading.Thread(
+				target=news_worker,
+				name="ptlinux-news",
+				daemon=True,
+			).start()
+			threading.Thread(
+				target=patches_worker,
+				name="ptlinux-patches",
+				daemon=True,
+			).start()
 		threading.Thread(
 			target=server_status_worker,
 			name="ptlinux-server-status",
 			daemon=True,
 		).start()
 		threading.Thread(target=version_worker, name="ptlinux-version", daemon=True).start()
+		if not startup_settings.low_bandwidth_mode:
 			refresh_launcher_update_check()
 
 	def start_remote_content_refresh() -> None:
@@ -3723,6 +3875,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		progress_updates.clear()
 		transfer_rate.reset()
 		speed_text.set("")
+		set_download_context_text("")
 		progress_bar.stop()
 		close_game_preloader()
 		if not ready:
@@ -3756,6 +3909,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		progress_updates.clear()
 		transfer_rate.reset()
 		speed_text.set("")
+		set_download_context_text("")
 		progress_bar.stop()
 		close_game_preloader()
 		root.deiconify()
@@ -4556,7 +4710,10 @@ def run_dashboard(paths: AppPaths) -> None:
 		).pack(anchor="w", pady=(1, 0))
 		tk.Label(
 			header_copy,
-			text="Tune launcher accessibility, the game window, and runtime preferences.",
+			text=(
+				"Tune launcher accessibility, downloads, the game window, and runtime "
+				"preferences."
+			),
 			background="#24170f",
 			foreground="#c9baaa",
 			font=("Sans", 9),
@@ -4586,6 +4743,21 @@ def run_dashboard(paths: AppPaths) -> None:
 		)
 		proton_path_value = tk.StringVar(value=current_settings.proton_path or "")
 		game_source_value = tk.StringVar(value=current_settings.game_source or "")
+		download_speed_value = tk.StringVar(
+			value=download_speed_setting_label(
+				current_settings.download_speed_limit_mbps
+			)
+		)
+		custom_download_speed_value = tk.StringVar(
+			value=(
+				f"{current_settings.download_speed_limit_mbps:g}"
+				if current_settings.download_speed_limit_mbps is not None
+				else "5"
+			)
+		)
+		low_bandwidth_value = tk.BooleanVar(
+			value=current_settings.low_bandwidth_mode
+		)
 
 		def add_choice(
 			parent: ttk.LabelFrame,
@@ -4673,6 +4845,10 @@ def run_dashboard(paths: AppPaths) -> None:
 
 		def save_current_settings() -> None:
 			try:
+				download_speed_limit = download_speed_setting_value(
+					download_speed_value.get(),
+					custom_download_speed_value.get(),
+				)
 				updated_settings = update_settings(
 					paths,
 					borderless=borderless_value.get(),
@@ -4685,6 +4861,8 @@ def run_dashboard(paths: AppPaths) -> None:
 					),
 					proton_path=proton_path_value.get().strip() or None,
 					game_source=game_source_value.get().strip() or None,
+					download_speed_limit_mbps=download_speed_limit,
+					low_bandwidth_mode=low_bandwidth_value.get(),
 				)
 			except (OSError, ValueError) as error:
 				show_themed_dialog(
@@ -4695,14 +4873,22 @@ def run_dashboard(paths: AppPaths) -> None:
 					window_icon=window_icon,
 				)
 				return
+			saved_limit = (
+				f"{updated_settings.download_speed_limit_mbps:g} MB/s"
+				if updated_settings.download_speed_limit_mbps is not None
+				else "unlimited"
+			)
 			append_log(
 				f"Saved launcher settings to {paths.settings_file}: "
 				f"runtime={updated_settings.runtime}, "
-				f"proton_sync={updated_settings.proton_sync}"
+				f"proton_sync={updated_settings.proton_sync}, "
+				f"download_limit={saved_limit}, "
+				f"low_bandwidth={updated_settings.low_bandwidth_mode}"
 			)
 			status.set("Settings saved.")
 			progress_text.set(
-				"Game settings apply on the next launch; launcher scale applies after restart."
+				"Game and download settings apply to the next operation; launcher scale "
+				"and cached-content mode apply after restart."
 			)
 			if show_dashboard_debug:
 				refresh_dashboard_debug_disk_state()
@@ -4782,13 +4968,97 @@ def run_dashboard(paths: AppPaths) -> None:
 			tuple(PROTON_SYNC_LABELS),
 		)
 
+		downloads_card = ttk.LabelFrame(
+			content,
+			text="DOWNLOADS",
+			style="SettingsCard.TLabelframe",
+			padding=14,
+		)
+		downloads_card.grid(
+			row=1,
+			column=0,
+			columnspan=2,
+			sticky="ew",
+			pady=(12, 0),
+		)
+		downloads_card.columnconfigure(0, weight=1)
+		downloads_card.columnconfigure(1, weight=1)
+		downloads_card.columnconfigure(2, weight=1)
+		ttk.Label(
+			downloads_card,
+			text=(
+				"Concurrency adapts to CDN latency, retries, transfer and disk speed, "
+				"CPU load, and the remaining files."
+			),
+			style="SettingsHint.TLabel",
+		).grid(row=0, column=0, columnspan=3, sticky="w", pady=(0, 9))
+		ttk.Checkbutton(
+			downloads_card,
+			text="Low-bandwidth mode (cached news, up to 2 workers and 5 MB/s)",
+			variable=low_bandwidth_value,
+			style="Settings.TCheckbutton",
+		).grid(row=1, column=0, sticky="w", padx=(0, 16))
+		ttk.Label(
+			downloads_card,
+			text="Speed limit",
+			style="SettingsText.TLabel",
+		).grid(row=1, column=1, sticky="w")
+		ttk.Label(
+			downloads_card,
+			text="Custom MB/s",
+			style="SettingsText.TLabel",
+		).grid(row=1, column=2, sticky="w", padx=(8, 0))
+		download_speed_selector = ttk.Combobox(
+			downloads_card,
+			textvariable=download_speed_value,
+			values=tuple(DOWNLOAD_SPEED_PRESETS_MBPS) + (
+				DOWNLOAD_SPEED_CUSTOM_LABEL,
+			),
+			state="readonly",
+			style="Settings.TCombobox",
+		)
+		download_speed_selector.grid(
+			row=2,
+			column=1,
+			sticky="ew",
+			pady=(3, 0),
+		)
+		custom_download_speed = ttk.Entry(
+			downloads_card,
+			textvariable=custom_download_speed_value,
+			style="Settings.TEntry",
+			width=12,
+		)
+		custom_download_speed.grid(
+			row=2,
+			column=2,
+			sticky="ew",
+			padx=(8, 0),
+			pady=(3, 0),
+		)
+
+		def update_custom_download_state(_event: object | None = None) -> None:
+			custom_download_speed.configure(
+				state=(
+					"normal"
+					if download_speed_value.get() == DOWNLOAD_SPEED_CUSTOM_LABEL
+					else "disabled"
+				)
+			)
+
+		download_speed_selector.bind(
+			"<<ComboboxSelected>>",
+			update_custom_download_state,
+		)
+		update_custom_download_state()
+
 		overrides_card = ttk.LabelFrame(
 			content,
 			text="OPTIONAL OVERRIDES",
 			style="SettingsCard.TLabelframe",
 			padding=14,
 		)
-		overrides_card.grid(row=1, column=0, columnspan=2, sticky="ew", pady=(12, 0))
+		overrides_card.grid(row=2, column=0, columnspan=2, sticky="ew", pady=(12, 0))
 		overrides_card.columnconfigure(0, weight=1)
 		ttk.Label(
 			overrides_card,
@@ -4813,7 +5083,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		)
 
 		footer = ttk.Frame(content, style="SettingsFooter.TFrame", padding=(12, 9))
-		footer.grid(row=2, column=0, columnspan=2, sticky="ew", pady=(12, 0))
+		footer.grid(row=3, column=0, columnspan=2, sticky="ew", pady=(12, 0))
 		footer.columnconfigure(0, weight=1)
 		ttk.Label(
 			footer,
@@ -4841,7 +5111,7 @@ def run_dashboard(paths: AppPaths) -> None:
 		dialog.update_idletasks()
 		settings_width, settings_height = fitted_window_size(
 			842,
-			760,
+			880,
 			scale=launcher_ui_scale,
 			screen_width=dialog.winfo_screenwidth(),
 			screen_height=dialog.winfo_screenheight(),
@@ -5037,6 +5307,13 @@ def _as_int(value: object) -> int:
 	return value if isinstance(value, int) and value >= 0 else 0
 
 
+def _as_float(value: object) -> float | None:
+	if isinstance(value, bool) or not isinstance(value, (int, float)):
+		return None
+	number = float(value)
+	return number if math.isfinite(number) and number >= 0 else None
+
+
 def dashboard_poll_interval(
 	*,
 	operation_active: bool,
@@ -5064,3 +5341,16 @@ def _format_bytes(value: int) -> str:
 
 def format_transfer_rate(bytes_per_second: float) -> str:
 	return f"{_format_bytes(max(0, round(bytes_per_second)))}/s"
+
+
+def format_eta(seconds: float | None) -> str:
+	if seconds is None or not math.isfinite(seconds) or seconds < 0:
+		return "calculating…"
+	total_seconds = max(0, math.ceil(seconds))
+	hours, remainder = divmod(total_seconds, 60 * 60)
+	minutes, seconds = divmod(remainder, 60)
+	if hours:
+		return f"{hours}h {minutes:02d}m"
+	if minutes:
+		return f"{minutes}m {seconds:02d}s"
+	return f"{seconds}s"