fix: make hosted downloads controllable and failures diagnosable

packages/app-lib/src/api/pack/hosted.rs

@@ -1,5 +1,7 @@
 //! Administrator-approved skin-site packs. Only content-addressed changed files cross the network.
+mod control;
 mod progress;
+pub use control::{HostedTaskState, cancel, pause, resume};
 mod tagged;
 mod transport;
 use crate::{
@@ -938,10 +940,20 @@ async fn synchronize_locked(instance_id: &str) -> crate::Result<SyncResult> {
     let metadata = crate::instance::get(instance_id)
         .await?
         .ok_or_else(|| invalid("Unknown instance"))?;
+    let task = control::Registration::new(instance_id)?;
     let progress =
         PackProgress::new(instance_id, &metadata.instance.name).await?;
-    let result =
-        synchronize_with_progress(instance_id, metadata, &progress).await;
+    let result = task
+        .control
+        .run(|| {
+            synchronize_with_progress(
+                instance_id,
+                metadata.clone(),
+                &progress,
+                &task.control,
+            )
+        })
+        .await;
     if let Err(error) = &result {
         progress.fail(error);
     }
@@ -952,6 +964,7 @@ async fn synchronize_with_progress(
     instance_id: &str,
     metadata: crate::state::InstanceMetadata,
     progress: &PackProgress,
+    control: &control::Control,
 ) -> crate::Result<SyncResult> {
     if metadata.instance.linked_launcher.is_some()
         || metadata.instance.symlink_target.is_some()
@@ -1275,7 +1288,7 @@ async fn synchronize_with_progress(
             &format!("文件 0/{total_files}"),
             true,
         );
-        let results = stream::iter(pending_downloads.into_values().map(
+        downloaded += control::collect_downloads(stream::iter(pending_downloads.into_values().map(
             |(file, url, object)| {
                 let current = &current;
                 let completed = &completed;
@@ -1342,34 +1355,14 @@ async fn synchronize_with_progress(
                         request = request
                             .with_header("Authorization", auth.clone());
                     }
-                    let first_result = download_to_path(
+                    download_to_path(
                         request.clone(),
                         &object,
                         &state.fetch_semaphore,
                         &state.pool,
                         Some(&mut on_progress),
                     )
-                    .await;
-                    if let Err(error) = first_result {
-                        tracing::warn!(
-                            path = %file_path,
-                            %error,
-                            "Parallel StarLight file download failed; retrying after the batch load has eased"
-                        );
-                        ensure_session(auth).await?;
-                        tokio::time::sleep(std::time::Duration::from_millis(
-                            750,
-                        ))
-                        .await;
-                        download_to_path(
-                            request,
-                            &object,
-                            &state.fetch_semaphore,
-                            &state.pool,
-                            Some(&mut on_progress),
-                        )
-                        .await?;
-                    }
+                    .await.map_err(|error| error.with_context(format!("下载整合包文件失败：{file_path}")))?;
                     let completed_files =
                         completed.fetch_add(1, Ordering::Relaxed) + 1;
                     let completed_bytes = {
@@ -1391,12 +1384,7 @@ async fn synchronize_with_progress(
                 }
             },
         ))
-        .buffer_unordered(concurrency)
-        .collect::<Vec<_>>()
-        .await;
-        downloaded += results.into_iter().try_fold(0, |sum, result| {
-            Ok::<u64, crate::Error>(sum + result?)
-        })?;
+        .buffer_unordered(concurrency)).await?;
     }
     ensure_session(&auth).await?;
     downloaded += tagged::download(
@@ -1446,6 +1434,8 @@ async fn synchronize_with_progress(
         previous,
         metadata,
     };
+    // From this atomic boundary onward the rollback/runtime transaction must finish.
+    control.begin_finalizing()?;
     write_json(&root, JOURNAL, &journal)?;
     let result = async {
         progress.update(0, 0, "正在安装游戏组件", true);

packages/app-lib/src/api/pack/hosted/control.rs

@@ -0,0 +1,329 @@
+use futures::{Stream, StreamExt};
+use serde::{Deserialize, Serialize};
+use std::{
+    future::Future,
+    sync::{Arc, LazyLock, Mutex},
+};
+use tokio::sync::watch;
+
+#[derive(
+    Clone, Copy, Debug, Default, Deserialize, Serialize, Hash, PartialEq, Eq,
+)]
+#[serde(rename_all = "snake_case")]
+pub enum HostedTaskState {
+    #[default]
+    Running,
+    Paused,
+    Canceling,
+    Canceled,
+    Failed,
+    Finalizing,
+}
+
+static CONTROLS: LazyLock<dashmap::DashMap<String, Arc<Control>>> =
+    LazyLock::new(dashmap::DashMap::new);
+
+pub(super) struct Control {
+    instance_id: String,
+    state: Mutex<HostedTaskState>,
+    changes: watch::Sender<HostedTaskState>,
+}
+
+fn stopped() -> crate::Error {
+    super::invalid("已停止整合包下载；已下载的缓存会保留，可重试继续")
+}
+
+impl Control {
+    fn new(instance_id: &str) -> Self {
+        Self {
+            instance_id: instance_id.to_owned(),
+            state: Mutex::new(HostedTaskState::Running),
+            changes: watch::channel(HostedTaskState::Running).0,
+        }
+    }
+
+    fn state(&self) -> HostedTaskState {
+        *self.state.lock().unwrap_or_else(|error| error.into_inner())
+    }
+
+    fn transition(
+        &self,
+        allowed: &[HostedTaskState],
+        next: HostedTaskState,
+    ) -> crate::Result<()> {
+        let mut state =
+            self.state.lock().unwrap_or_else(|error| error.into_inner());
+        if !allowed.contains(&state) {
+            return Err(super::invalid(
+                "任务状态已变化或正在应用安装文件，当前操作不可用",
+            ));
+        }
+        *state = next;
+        // Publish under the transition lock, so a late pause cannot overwrite finalization.
+        crate::event::emit::set_hosted_loading_state(&self.instance_id, next);
+        self.changes.send_replace(next);
+        Ok(())
+    }
+
+    fn pause(&self) -> crate::Result<()> {
+        self.transition(&[HostedTaskState::Running], HostedTaskState::Paused)
+    }
+
+    fn resume(&self) -> crate::Result<()> {
+        self.transition(&[HostedTaskState::Paused], HostedTaskState::Running)
+    }
+
+    fn cancel(&self) -> crate::Result<()> {
+        self.transition(
+            &[HostedTaskState::Running, HostedTaskState::Paused],
+            HostedTaskState::Canceling,
+        )
+    }
+
+    pub(super) fn begin_finalizing(&self) -> crate::Result<()> {
+        self.transition(
+            &[HostedTaskState::Running],
+            HostedTaskState::Finalizing,
+        )
+    }
+
+    /// The operation may be dropped only before begin_finalizing. Restarting
+    /// re-plans from verified cache objects and the downloader's partial files.
+    pub(super) async fn run<T, F, Fut>(
+        &self,
+        mut operation: F,
+    ) -> crate::Result<T>
+    where
+        F: FnMut() -> Fut,
+        Fut: Future<Output = crate::Result<T>>,
+    {
+        let mut changes = self.changes.subscribe();
+        loop {
+            let state = *changes.borrow_and_update();
+            match state {
+                HostedTaskState::Paused => {
+                    changes.changed().await.map_err(|_| stopped())?;
+                    continue;
+                }
+                HostedTaskState::Canceling => return Err(stopped()),
+                _ => {}
+            }
+            let work = operation();
+            tokio::pin!(work);
+            loop {
+                tokio::select! {
+                    biased;
+                    changed = changes.changed() => {
+                        changed.map_err(|_| stopped())?;
+                        match self.state() {
+                            HostedTaskState::Paused => break,
+                            HostedTaskState::Canceling => return Err(stopped()),
+                            _ => {},
+                        }
+                    }
+                    result = &mut work => {
+                        match self.state() {
+                            HostedTaskState::Paused => break,
+                            HostedTaskState::Canceling => return Err(stopped()),
+                            _ => return result,
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub(super) struct Registration {
+    instance_id: String,
+    pub(super) control: Arc<Control>,
+}
+
+impl Registration {
+    pub(super) fn new(instance_id: &str) -> crate::Result<Self> {
+        use dashmap::mapref::entry::Entry;
+        let control = Arc::new(Control::new(instance_id));
+        match CONTROLS.entry(instance_id.to_owned()) {
+            Entry::Occupied(_) => {
+                return Err(super::invalid("此实例已有整合包下载任务"));
+            }
+            Entry::Vacant(entry) => {
+                entry.insert(control.clone());
+            }
+        }
+        Ok(Self {
+            instance_id: instance_id.to_owned(),
+            control,
+        })
+    }
+}
+
+impl Drop for Registration {
+    fn drop(&mut self) {
+        CONTROLS.remove_if(&self.instance_id, |_, value| {
+            Arc::ptr_eq(value, &self.control)
+        });
+    }
+}
+
+fn lookup(instance_id: &str) -> crate::Result<Arc<Control>> {
+    CONTROLS
+        .get(instance_id)
+        .map(|entry| entry.value().clone())
+        .ok_or_else(|| super::invalid("整合包下载任务已结束，请重试"))
+}
+
+pub async fn pause(instance_id: &str) -> crate::Result<()> {
+    lookup(instance_id)?.pause()
+}
+pub async fn resume(instance_id: &str) -> crate::Result<()> {
+    lookup(instance_id)?.resume()
+}
+pub async fn cancel(instance_id: &str) -> crate::Result<()> {
+    lookup(instance_id)?.cancel()
+}
+
+/// Stop the batch on its first error so stalled peers cannot hide failure.
+pub(super) async fn collect_downloads<S>(downloads: S) -> crate::Result<u64>
+where
+    S: Stream<Item = crate::Result<u64>>,
+{
+    tokio::pin!(downloads);
+    let mut total = 0;
+    while let Some(result) = downloads.next().await {
+        total += result?;
+    }
+    Ok(total)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use futures::FutureExt;
+    use std::sync::{
+        Arc,
+        atomic::{AtomicUsize, Ordering},
+    };
+    use tokio::sync::{Notify, Semaphore};
+
+    struct TransferGuard(Arc<AtomicUsize>, Arc<Notify>);
+
+    impl Drop for TransferGuard {
+        fn drop(&mut self) {
+            self.0.fetch_add(1, Ordering::SeqCst);
+            self.1.notify_one();
+        }
+    }
+
+    #[tokio::test]
+    async fn pause_drops_live_transfers_and_resume_restarts_before_stop() {
+        let control = Arc::new(Control::new("pause-resume-test"));
+        let starts = Arc::new(Semaphore::new(0));
+        let drops = Arc::new(AtomicUsize::new(0));
+        let dropped = Arc::new(Notify::new());
+        let task = {
+            let control = control.clone();
+            let starts = starts.clone();
+            let drops = drops.clone();
+            let dropped = dropped.clone();
+            tokio::spawn(async move {
+                control
+                    .run(|| {
+                        let guard =
+                            TransferGuard(drops.clone(), dropped.clone());
+                        starts.add_permits(1);
+                        async move {
+                            let _guard = guard;
+                            std::future::pending::<crate::Result<()>>().await
+                        }
+                    })
+                    .await
+            })
+        };
+        starts.acquire().await.unwrap().forget();
+        control.pause().unwrap();
+        dropped.notified().await;
+        assert_eq!(drops.load(Ordering::SeqCst), 1);
+        assert_eq!(control.state(), HostedTaskState::Paused);
+        control.resume().unwrap();
+        starts.acquire().await.unwrap().forget();
+        control.cancel().unwrap();
+        let result = task.await.unwrap();
+        assert!(result.unwrap_err().to_string().contains("停止"));
+        assert_eq!(drops.load(Ordering::SeqCst), 2);
+    }
+
+    #[tokio::test]
+    async fn stopping_an_already_paused_task_never_starts_a_transfer() {
+        let control = Arc::new(Control::new("paused-stop-test"));
+        control.pause().unwrap();
+        let task = {
+            let control = control.clone();
+            tokio::spawn(async move {
+                control
+                    .run(|| async {
+                        panic!("paused work was polled");
+                        Ok::<(), crate::Error>(())
+                    })
+                    .await
+            })
+        };
+        control.cancel().unwrap();
+        assert!(task.await.unwrap().is_err());
+    }
+
+    #[test]
+    fn finalization_rejects_pause_and_stop() {
+        let control = Control::new("finalization-test");
+        control.begin_finalizing().unwrap();
+        assert_eq!(control.state(), HostedTaskState::Finalizing);
+        assert!(control.pause().is_err());
+        assert!(control.cancel().is_err());
+    }
+
+    #[test]
+    fn pause_and_finalization_have_only_one_winner() {
+        for _ in 0..32 {
+            let control = Arc::new(Control::new("finalization-race-test"));
+            let barrier = Arc::new(std::sync::Barrier::new(2));
+            let task = {
+                let control = control.clone();
+                let barrier = barrier.clone();
+                std::thread::spawn(move || {
+                    barrier.wait();
+                    control.pause().is_ok()
+                })
+            };
+            barrier.wait();
+            let finalized = control.begin_finalizing().is_ok();
+            assert_ne!(finalized, task.join().unwrap());
+        }
+    }
+
+    #[tokio::test]
+    async fn first_failure_drops_stalled_peer_downloads() {
+        let drops = Arc::new(AtomicUsize::new(0));
+        let guard = TransferGuard(drops.clone(), Arc::new(Notify::new()));
+        let downloads = futures::stream::iter(vec![
+            async move {
+                let _guard = guard;
+                std::future::pending::<crate::Result<u64>>().await
+            }
+            .boxed(),
+            async { Err(super::super::invalid("failed file")) }.boxed(),
+        ])
+        .buffer_unordered(2);
+        let result = collect_downloads(downloads).await;
+        assert!(result.unwrap_err().to_string().contains("failed file"));
+        assert_eq!(drops.load(Ordering::SeqCst), 1);
+    }
+
+    #[test]
+    fn registration_is_unique_and_released_on_drop() {
+        let id = uuid::Uuid::new_v4().to_string();
+        let registration = Registration::new(&id).unwrap();
+        assert!(Registration::new(&id).is_err());
+        drop(registration);
+        assert!(Registration::new(&id).is_ok());
+    }
+}

packages/app-lib/src/api/pack/hosted/progress.rs

@@ -59,6 +59,9 @@ impl PackProgress {
                 instance_id: instance_id.to_owned(),
                 instance_name: name.to_owned(),
                 error: None,
+                state: super::HostedTaskState::Running,
+                can_pause: true,
+                can_cancel: true,
             },
             1.0,
             "正在获取整合包信息",

packages/app-lib/src/api/pack/hosted/tagged.rs

@@ -681,7 +681,7 @@ pub(super) async fn download(
         set_loading(&bar, 0, file.size, "等待下载")?;
         work.push((file, url, object, bar));
     }
-    let results =
+    control::collect_downloads(
         stream::iter(work.into_iter().map(|(file, url, object, bar)| {
             let current = &current;
             let state = &state;
@@ -740,10 +740,7 @@ pub(super) async fn download(
                 result
             }
         }))
-        .buffer_unordered(concurrency)
-        .collect::<Vec<_>>()
-        .await;
-    results
-        .into_iter()
-        .try_fold(0, |sum, result| Ok(sum + result?))
+        .buffer_unordered(concurrency),
+    )
+    .await
 }

packages/app-lib/src/event/emit.rs

@@ -232,8 +232,24 @@ pub fn fail_hosted_loading(key: &LoadingBarId, error: &str) {
         && let Some(mut bar) = state.loading_bars.get_mut(&key.0)
     {
         match &mut bar.bar_type {
-            LoadingBarType::HostedPackSync { error: failure, .. }
-            | LoadingBarType::HostedModDownload { error: failure, .. } => {
+            LoadingBarType::HostedPackSync {
+                error: failure,
+                state,
+                can_pause,
+                can_cancel,
+                ..
+            } => {
+                use crate::api::pack::hosted::HostedTaskState;
+                *state = if *state == HostedTaskState::Canceling {
+                    HostedTaskState::Canceled
+                } else {
+                    HostedTaskState::Failed
+                };
+                *can_pause = false;
+                *can_cancel = false;
+                *failure = Some(error.to_owned());
+            }
+            LoadingBarType::HostedModDownload { error: failure, .. } => {
                 *failure = Some(error.to_owned())
             }
             _ => {}
@@ -241,6 +257,67 @@ pub fn fail_hosted_loading(key: &LoadingBarId, error: &str) {
     }
 }
 
+/// Update the authoritative snapshot and notify observers even while all
+/// transfer futures are paused and no byte-progress event can be produced.
+pub fn set_hosted_loading_state(
+    instance_id: &str,
+    next: crate::api::pack::hosted::HostedTaskState,
+) {
+    use crate::api::pack::hosted::HostedTaskState;
+    let Ok(event_state) = crate::EventState::get() else {
+        return;
+    };
+    for mut bar in event_state.loading_bars.iter_mut() {
+        let LoadingBarType::HostedPackSync {
+            instance_id: id,
+            state,
+            can_pause,
+            can_cancel,
+            ..
+        } = &mut bar.bar_type
+        else {
+            continue;
+        };
+        if id != instance_id {
+            continue;
+        }
+        *state = next;
+        let controllable =
+            matches!(next, HostedTaskState::Running | HostedTaskState::Paused);
+        *can_pause = controllable;
+        *can_cancel = controllable;
+        match next {
+            HostedTaskState::Paused => {
+                bar.message = "已暂停，点击继续以恢复下载".into()
+            }
+            HostedTaskState::Canceling => {
+                bar.message = "正在停止整合包下载".into()
+            }
+            HostedTaskState::Running => {
+                bar.message = "正在继续整合包下载".into()
+            }
+            _ => {}
+        }
+        #[cfg(feature = "tauri")]
+        {
+            let _ = event_state.app.emit(
+                "loading",
+                LoadingPayload {
+                    fraction: Some(if bar.total > 0.0 {
+                        bar.current / bar.total
+                    } else {
+                        0.0
+                    }),
+                    message: bar.message.clone(),
+                    event: bar.bar_type.clone(),
+                    loader_uuid: bar.loading_bar_uuid,
+                    total: Some(bar.total),
+                },
+            );
+        }
+    }
+}
+
 // emit_warning(message)
 pub async fn emit_warning(message: &str) -> crate::Result<()> {
     #[cfg(feature = "tauri")]

packages/app-lib/src/event/mod.rs

@@ -142,6 +142,12 @@ pub enum LoadingBarType {
         instance_id: String,
         instance_name: String,
         error: Option<String>,
+        #[serde(default)]
+        state: crate::api::pack::hosted::HostedTaskState,
+        #[serde(default)]
+        can_pause: bool,
+        #[serde(default)]
+        can_cancel: bool,
     },
     HostedModDownload {
         instance_id: String,

packages/app-lib/src/util/fetch.rs

@@ -689,6 +689,46 @@ fn bounded_diagnostic_text(value: impl AsRef<str>, max_chars: usize) -> String {
     value.as_ref().chars().take(max_chars).collect()
 }
 
+fn sanitize_download_error_text(value: &str) -> String {
+    static URLS: LazyLock<regex::Regex> = LazyLock::new(|| {
+        regex::Regex::new(r"(?i)\b(?:https?|socks4a?|socks5h?)://[^\s]+")
+            .expect("download diagnostic URL pattern should be valid")
+    });
+    let sanitized = URLS.replace_all(value, |matched: &regex::Captures<'_>| {
+        let url = &matched[0];
+        // A malformed URL must not fall back to logging its userinfo. The
+        // normal helper also strips signed query strings and fragments.
+        if Url::parse(url).is_ok() {
+            sanitize_url_for_log(url)
+        } else {
+            "[redacted URL]".to_string()
+        }
+    });
+    bounded_diagnostic_text(sanitized, 256)
+}
+
+fn download_transport_error_detail(source: &reqwest::Error) -> String {
+    // reqwest's Display stops before the useful DNS/TLS/socket cause and can
+    // include a signed request URL. Walk only its underlying causes instead.
+    let mut details = Vec::new();
+    let mut cause = source.source();
+    while let Some(error) = cause {
+        let detail = sanitize_download_error_text(&error.to_string());
+        if details.last() != Some(&detail) {
+            details.push(detail);
+        }
+        if details.len() == 8 {
+            break;
+        }
+        cause = error.source();
+    }
+    if details.is_empty() {
+        sanitize_download_error_text(&source.to_string())
+    } else {
+        bounded_diagnostic_text(details.join(": "), 256)
+    }
+}
+
 fn download_error_category(error: &crate::Error) -> &'static str {
     match error.raw.as_ref() {
         ErrorKind::FetchError(source) => {
@@ -750,7 +790,16 @@ fn download_error_category(error: &crate::Error) -> &'static str {
 fn download_error_detail(error: &crate::Error) -> String {
     match error.raw.as_ref() {
         ErrorKind::FetchError(source) => source.status().map_or_else(
-            || format!("{} failure", download_error_category(error)),
+            || {
+                bounded_diagnostic_text(
+                    format!(
+                        "{} failure: {}",
+                        download_error_category(error),
+                        download_transport_error_detail(source)
+                    ),
+                    256,
+                )
+            },
             |status| format!("HTTP {}", status.as_u16()),
         ),
         ErrorKind::LabrinthError(error) => error.status.map_or_else(
@@ -929,8 +978,10 @@ fn add_starlight_direct_recovery_route(routes: &mut Vec<DownloadRoute>) {
         .filter(|route| {
             route.proxy == ProxyPolicy::System
                 && Url::parse(&route.url).ok().is_some_and(|url| {
-                    url.host_str() == Some("skin.starlight.cool")
-                        && url.path().starts_with("/starlight/mod/packs/files/")
+                    matches!(
+                        url.host_str(),
+                        Some("skin.starlight.cool" | "download.starlight.cool")
+                    ) && url.path().starts_with("/starlight/mod/packs/files/")
                 })
         })
         .cloned()
@@ -6308,7 +6359,9 @@ async fn download_to_path_inner(
                             source = route.source.as_str(),
                             attempt = attempts,
                             max_attempts = file_attempt_budget,
-                            error = %error,
+                            proxy = ?route.proxy,
+                            category = download_error_category(&error),
+                            error = %download_error_detail(&error),
                             "File download request failed; trying the next source or retry"
                         );
                         last_error = Some(error);
@@ -8857,18 +8910,86 @@ mod tests {
 
     #[test]
     fn starlight_hosted_files_have_a_direct_recovery_route() {
-        let mut routes = vec![official_route(
+        for url in [
             "https://skin.starlight.cool/starlight/mod/packs/files/release/hash",
-            ResourceClass::Modpack,
-        )];
+            "https://download.starlight.cool:20443/starlight/mod/packs/files/4/hash",
+        ] {
+            let mut routes = vec![official_route(url, ResourceClass::Modpack)];
+            add_starlight_direct_recovery_route(&mut routes);
+            add_starlight_direct_recovery_route(&mut routes);
 
-        add_starlight_direct_recovery_route(&mut routes);
+            assert_eq!(routes.len(), 2, "{url}");
+            assert_eq!(routes[0].proxy, ProxyPolicy::System);
+            assert_eq!(routes[1].proxy, ProxyPolicy::Direct);
+            assert_eq!(routes[0].url, routes[1].url);
+            assert!(routes[1].allow_sensitive_headers);
+        }
+    }
 
-        assert_eq!(routes.len(), 2);
-        assert_eq!(routes[0].proxy, ProxyPolicy::System);
-        assert_eq!(routes[1].proxy, ProxyPolicy::Direct);
-        assert_eq!(routes[0].url, routes[1].url);
-        assert!(routes[1].allow_sensitive_headers);
+    #[test]
+    fn starlight_direct_recovery_excludes_other_paths_and_lookalike_hosts() {
+        for url in [
+            "https://download.starlight.cool:20443/starlight/mod/packs",
+            "https://download.starlight.cool.evil.example/starlight/mod/packs/files/4/hash",
+            "https://evil.example/starlight/mod/packs/files/4/hash",
+            "https://skin.starlight.cool/yggdrasil",
+        ] {
+            let mut routes = vec![official_route(url, ResourceClass::Modpack)];
+            add_starlight_direct_recovery_route(&mut routes);
+            assert_eq!(routes.len(), 1, "{url}");
+        }
+    }
+
+    #[tokio::test]
+    async fn download_transport_diagnostic_preserves_causes_without_url_secrets()
+     {
+        let listener =
+            tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let address = listener.local_addr().unwrap();
+        drop(listener);
+        let url = format!(
+            "http://username:password@{address}/file?token=secret#fragment"
+        );
+        let error: crate::Error = reqwest::Client::builder()
+            .no_proxy()
+            .build()
+            .unwrap()
+            .get(url)
+            .send()
+            .await
+            .unwrap_err()
+            .into();
+        let detail = download_error_detail(&error);
+        assert_eq!(download_error_category(&error), "connect");
+        assert!(detail.contains("connect"), "{detail}");
+        assert!(
+            detail.contains("tcp") || detail.contains("os error"),
+            "{detail}"
+        );
+        for secret in ["username", "password", "token", "secret", "fragment"] {
+            assert!(!detail.contains(secret), "{detail}");
+        }
+    }
+
+    #[test]
+    fn download_transport_diagnostic_scrubs_embedded_urls() {
+        let detail = sanitize_download_error_text(
+            "request https://username:password@example.com/file?token=secret#fragment failed: connecting to http://proxyuser:proxypass@proxy.example:8080/?key=proxysecret: connection refused",
+        );
+        assert!(detail.contains("https://example.com/file"), "{detail}");
+        assert!(detail.contains("http://proxy.example:8080/"), "{detail}");
+        assert!(detail.contains("connection refused"), "{detail}");
+        for secret in [
+            "username",
+            "password",
+            "token",
+            "secret",
+            "fragment",
+            "proxyuser",
+            "proxypass",
+        ] {
+            assert!(!detail.contains(secret), "{detail}");
+        }
     }
 
     #[test]