Merge current main and make purchase filing atomic under concurrent writes

Every paid download logged "filing into filebrowser/Music/... failed
(non-fatal): Permission denied". The purchase played in-app but never
appeared in Files. FileBrowser's folders belong to its rootless container
range (host uid 100000, mode 755). This service is host uid 1000, outside
that range, so it can read them but not create files in them.

New container::filebrowser::save_new_file:
- Writes directly when the folder allows it.
- Otherwise writes through `podman unshare`, where that uid range is
  ours: to a temp file, then chowned to the folder's owner, set to 0644,
  and hard-linked into place. FileBrowser never sees a partial file and an
  existing file is never replaced. A missing folder is created and given
  its parent's owner. No sudo.
- Keeps the "name (2).ext" de-duplication the RPC did inline.

Checked the unshare script on amishparadise in a scratch folder owned
like FileBrowser's: new folder + file OK, owner/mode right, no clobber,
no temp file left, and the service can read the result.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

core/archipelago/src/api/rpc/content.rs

@@ -54,13 +54,9 @@ fn paid_content_response(bytes: &[u8], mime: &str, paid_sats: u64) -> serde_json
     })
 }
 
-/// FileBrowser owns its files through a rootless UID mapping. Use its authenticated
-/// API rather than writing host paths with the backend's unrelated UID. Its
-/// override=false upload atomically refuses existing names, including races.
+/// File purchases through an atomic no-clobber write in Files' own namespace.
 async fn file_purchase_in_files(
-    client: &reqwest::Client,
-    base_url: &str,
-    token: &str,
+    data_dir: &std::path::Path,
     filename: &str,
     mime: &str,
     bytes: &[u8],
@@ -72,59 +68,24 @@ async fn file_purchase_in_files(
     } else {
         "Documents"
     };
-    let mut folder_url = reqwest::Url::parse(base_url)?;
-    folder_url
-        .path_segments_mut()
-        .map_err(|_| anyhow::anyhow!("Invalid Files URL"))?
-        .extend(["api", "resources", folder, ""]);
-    let response = client
-        .get(folder_url.clone())
-        .header("X-Auth", token)
-        .send()
-        .await?;
-    if response.status() == reqwest::StatusCode::NOT_FOUND {
-        let response = client
-            .post(folder_url.clone())
-            .header("X-Auth", token)
-            .send()
-            .await?;
-        if response.status() != reqwest::StatusCode::CONFLICT {
-            response.error_for_status()?;
-        }
-    } else {
-        response.error_for_status()?;
-    }
-    let base = std::path::Path::new(filename)
+    let root = data_dir.join("filebrowser");
+    anyhow::ensure!(
+        tokio::fs::metadata(&root).await?.is_dir(),
+        "Files storage is unavailable"
+    );
+    let name = std::path::Path::new(filename)
         .file_name()
         .and_then(|n| n.to_str())
         .filter(|n| !n.is_empty())
         .unwrap_or("download");
-    let (stem, extension) = match base.rsplit_once('.') {
-        Some((stem, ext)) if !stem.is_empty() => (stem, format!(".{ext}")),
-        _ => (base, String::new()),
-    };
-    for attempt in 1..=100 {
-        let name = if attempt == 1 {
-            base.to_string()
-        } else {
-            format!("{stem} ({attempt}){extension}")
-        };
-        let mut url = folder_url.clone();
-        url.path_segments_mut().unwrap().pop_if_empty().push(&name);
-        url.query_pairs_mut().append_pair("override", "false");
-        let response = client
-            .post(url)
-            .header("X-Auth", token)
-            .body(bytes.to_vec())
-            .send()
-            .await?;
-        if response.status() == reqwest::StatusCode::CONFLICT {
-            continue;
-        }
-        response.error_for_status()?;
-        return Ok(format!("{folder}/{name}"));
-    }
-    anyhow::bail!("Too many existing copies; purchased file remains in the purchase cache")
+    let path =
+        crate::container::filebrowser::save_new_file(&root.join(folder), name, bytes).await?;
+    Ok(format!(
+        "{folder}/{}",
+        path.file_name()
+            .and_then(|n| n.to_str())
+            .context("Invalid Files name")?
+    ))
 }
 
 impl RpcHandler {
@@ -728,28 +689,8 @@ impl RpcHandler {
 
         // The durable purchased-content cache above is primary. A Files copy
         // remains optional: a stopped FileBrowser must not undo a paid download.
-        let filed = async {
-            let auth = self.handle_filebrowser_token().await?;
-            let token = auth
-                .get("token")
-                .and_then(|v| v.as_str())
-                .context("FileBrowser omitted its authentication token")?;
-            let client = reqwest::Client::builder()
-                .no_proxy()
-                .redirect(reqwest::redirect::Policy::none())
-                .timeout(std::time::Duration::from_secs(30))
-                .build()?;
-            file_purchase_in_files(
-                &client,
-                "http://127.0.0.1:8083",
-                token,
-                &filename,
-                &mime_type,
-                &bytes,
-            )
-            .await
-        }
-        .await;
+        let filed =
+            file_purchase_in_files(&self.config.data_dir, &filename, &mime_type, &bytes).await;
         match filed {
             Ok(path) => tracing::info!("paid download: filed into Files/{path}"),
             Err(error) => tracing::warn!(

core/archipelago/src/api/rpc/content_tests.rs

@@ -1,69 +1,4 @@
 use super::*;
-use hyper::{
-    service::{make_service_fn, service_fn},
-    Body, Response, Server,
-};
-use std::{
-    collections::VecDeque,
-    convert::Infallible,
-    sync::{Arc, Mutex},
-};
-
-struct FilesApi {
-    url: String,
-    seen: Arc<Mutex<Vec<(String, String, Vec<u8>)>>>,
-    task: tokio::task::JoinHandle<()>,
-}
-impl Drop for FilesApi {
-    fn drop(&mut self) {
-        self.task.abort();
-    }
-}
-fn files_api(statuses: Vec<u16>) -> FilesApi {
-    let statuses = Arc::new(Mutex::new(VecDeque::from(statuses)));
-    let seen = Arc::new(Mutex::new(Vec::new()));
-    let history = seen.clone();
-    let server = Server::bind(&([127, 0, 0, 1], 0).into());
-    let address = server.local_addr();
-    let service = make_service_fn(move |_| {
-        let statuses = statuses.clone();
-        let seen = history.clone();
-        async move {
-            Ok::<_, Infallible>(service_fn(move |request: hyper::Request<Body>| {
-                let statuses = statuses.clone();
-                let seen = seen.clone();
-                async move {
-                    assert_eq!(request.headers().get("X-Auth").unwrap(), "test-session");
-                    let method = request.method().to_string();
-                    let uri = request.uri().to_string();
-                    let body = hyper::body::to_bytes(request.into_body())
-                        .await
-                        .unwrap()
-                        .to_vec();
-                    seen.lock().unwrap().push((method, uri, body));
-                    let status = statuses
-                        .lock()
-                        .unwrap()
-                        .pop_front()
-                        .expect("unexpected extra Files request");
-                    Ok::<_, Infallible>(
-                        Response::builder()
-                            .status(status)
-                            .body(Body::empty())
-                            .unwrap(),
-                    )
-                }
-            }))
-        }
-    });
-    FilesApi {
-        url: format!("http://{address}"),
-        seen,
-        task: tokio::spawn(async move {
-            server.serve(service).await.unwrap();
-        }),
-    }
-}
 
 #[test]
 fn first_and_cached_paid_downloads_have_the_same_client_payload_contract() {
@@ -85,80 +20,37 @@ fn first_and_cached_paid_downloads_have_the_same_client_payload_contract() {
 }
 
 #[tokio::test]
-async fn files_copy_uses_authenticated_api_and_preserves_existing_names() {
-    let api = files_api(vec![200, 409, 200]);
-    let client = reqwest::Client::new();
-    let path = file_purchase_in_files(
-        &client,
-        &api.url,
-        "test-session",
-        "../my #file?.txt",
-        "text/plain",
-        b"paid bytes",
-    )
+async fn files_copy_routes_media_and_sanitizes_the_filename() {
+    let dir = tempfile::tempdir().unwrap();
+    tokio::fs::create_dir(dir.path().join("filebrowser"))
         .await
         .unwrap();
-    assert_eq!(path, "Documents/my #file? (2).txt");
-    let seen = api.seen.lock().unwrap();
-    assert_eq!(seen[0].0, "GET");
-    assert_eq!(seen[0].1, "/api/resources/Documents/");
-    assert_eq!(seen.len(), 3);
-    for (_, uri, body) in &seen[1..] {
-        assert!(uri.contains("override=false"));
-        assert!(uri.contains("%23file%3F"));
-        assert!(!uri.contains("../"));
-        assert_eq!(body, b"paid bytes");
-    }
-}
-
-#[tokio::test]
-async fn files_copy_creates_missing_media_folder() {
     for (mime, folder) in [
         ("image/png", "Photos"),
         ("video/mp4", "Photos"),
-        ("audio/ogg", "Music"),
+        ("audio/mpeg", "Music"),
+        ("text/plain", "Documents"),
     ] {
-        let api = files_api(vec![404, 200, 200]);
-        let path = file_purchase_in_files(
-            &reqwest::Client::new(),
-            &api.url,
-            "test-session",
-            "file",
-            mime,
-            b"bytes",
-        )
+        let relative = file_purchase_in_files(dir.path(), "../name #?.bin", mime, b"paid")
             .await
             .unwrap();
-        assert_eq!(path, format!("{folder}/file"));
-        let seen = api.seen.lock().unwrap();
-        assert_eq!(seen[1].0, "POST");
-        assert!(seen[1].1.ends_with('/'));
-        assert!(seen[1].2.is_empty());
-        assert_eq!(seen[2].2, b"bytes");
+        assert!(relative.starts_with(&format!("{folder}/name #?")));
+        assert_eq!(
+            tokio::fs::read(dir.path().join("filebrowser").join(relative))
+                .await
+                .unwrap(),
+            b"paid"
+        );
     }
 }
 
 #[tokio::test]
-async fn files_copy_fails_without_overwriting_or_claiming_success_on_errors() {
-    for statuses in [
-        vec![401],
-        vec![503],
-        vec![404, 500],
-        vec![200, 507],
-        vec![200, 403],
-    ] {
-        let expected = statuses.len();
-        let api = files_api(statuses);
-        assert!(file_purchase_in_files(
-            &reqwest::Client::new(),
-            &api.url,
-            "test-session",
-            "file.txt",
-            "text/plain",
-            b"bytes"
-        )
+async fn unavailable_files_storage_is_reported_without_creating_a_fake_installation() {
+    let dir = tempfile::tempdir().unwrap();
+    assert!(
+        file_purchase_in_files(dir.path(), "name", "text/plain", b"bytes")
             .await
-        .is_err());
-        assert_eq!(api.seen.lock().unwrap().len(), expected);
-    }
+            .is_err()
+    );
+    assert!(!dir.path().join("filebrowser").exists());
 }

core/archipelago/src/container/filebrowser.rs

@@ -5,7 +5,7 @@
 //! starting the container with `--config /data/.filebrowser.json`.
 
 use anyhow::{Context, Result};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use tokio::fs;
 
 use crate::update::host_sudo;
@@ -117,6 +117,197 @@ fn shell_quote(s: &str) -> String {
     s.replace('\'', "'\\''")
 }
 
+/// Save a complete purchase without overwriting any existing directory entry.
+/// Both host and rootless-namespace paths publish with a no-clobber hard link.
+pub async fn save_new_file(dir: &Path, name: &str, bytes: &[u8]) -> Result<PathBuf> {
+    save_new_file_with(dir, name, bytes, write_via_userns).await
+}
+
+fn validate_filename(name: &str) -> Result<()> {
+    anyhow::ensure!(
+        !name.is_empty()
+            && name != "."
+            && name != ".."
+            && !name.contains(['/', '\\', '\0'])
+            && name.len() <= 255,
+        "Invalid purchased filename"
+    );
+    Ok(())
+}
+
+async fn save_new_file_with<F, Fut>(
+    dir: &Path,
+    name: &str,
+    bytes: &[u8],
+    fallback: F,
+) -> Result<PathBuf>
+where
+    F: FnOnce(PathBuf, String, Vec<u8>) -> Fut,
+    Fut: std::future::Future<Output = Result<PathBuf>>,
+{
+    validate_filename(name)?;
+    // Never follow a user-created destination directory symlink.
+    match fs::symlink_metadata(dir).await {
+        Ok(meta) => anyhow::ensure!(meta.is_dir(), "Files destination is not a directory"),
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {}
+        Err(error) => return Err(error.into()),
+    }
+    save_after_direct_result(
+        write_direct(dir, name, bytes).await,
+        dir,
+        name,
+        bytes,
+        fallback,
+    )
+    .await
+}
+
+async fn save_after_direct_result<F, Fut>(
+    result: std::io::Result<PathBuf>,
+    dir: &Path,
+    name: &str,
+    bytes: &[u8],
+    fallback: F,
+) -> Result<PathBuf>
+where
+    F: FnOnce(PathBuf, String, Vec<u8>) -> Fut,
+    Fut: std::future::Future<Output = Result<PathBuf>>,
+{
+    match result {
+        Ok(path) => Ok(path),
+        Err(error) if error.kind() == std::io::ErrorKind::PermissionDenied => {
+            fallback(dir.to_owned(), name.to_owned(), bytes.to_vec())
+                .await
+                .context("Saving purchase in Files user namespace")
+        }
+        Err(error) => Err(error).context("Saving purchase in Files"),
+    }
+}
+
+fn numbered_name(name: &str, attempt: usize) -> String {
+    if attempt == 1 {
+        return name.to_owned();
+    }
+    match name.rsplit_once('.') {
+        Some((stem, extension)) if !stem.is_empty() => format!("{stem} ({attempt}).{extension}"),
+        _ => format!("{name} ({attempt})"),
+    }
+}
+
+struct PendingFile(PathBuf);
+impl Drop for PendingFile {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_file(&self.0);
+    }
+}
+
+async fn write_direct(dir: &Path, name: &str, bytes: &[u8]) -> std::io::Result<PathBuf> {
+    use std::os::unix::fs::PermissionsExt;
+    use tokio::io::AsyncWriteExt;
+    fs::create_dir_all(dir).await?;
+    let temp_path = dir.join(format!(".archy-saving-{}", uuid::Uuid::new_v4()));
+    let mut file = fs::OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .mode(0o600)
+        .open(&temp_path)
+        .await?;
+    let temp = PendingFile(temp_path);
+    file.write_all(bytes).await?;
+    file.set_permissions(std::fs::Permissions::from_mode(0o644))
+        .await?;
+    file.sync_all().await?;
+    for attempt in 1..=100 {
+        let target = dir.join(numbered_name(name, attempt));
+        match fs::hard_link(&temp.0, &target).await {
+            Ok(()) => return Ok(target),
+            Err(error) if error.kind() == std::io::ErrorKind::AlreadyExists => continue,
+            Err(error) => return Err(error),
+        }
+    }
+    Err(std::io::Error::new(
+        std::io::ErrorKind::AlreadyExists,
+        "Too many existing copies; purchase cache retained",
+    ))
+}
+
+// Positional arguments carry all user-controlled text. mktemp prevents temp-name
+// collisions; ln -T refuses files, symlinks and directories, including races.
+const WRITE_VIA_USERNS: &str = r#"set -eu
+dir=$1
+name=$2
+expected=$3
+[ ! -L "$dir" ] || exit 1
+if [ ! -d "$dir" ]; then
+    mkdir -p -- "$dir"
+    chown --reference="$(dirname -- "$dir")" -- "$dir"
+fi
+tmp=$(mktemp "$dir/.archy-saving.XXXXXXXXXX")
+trap 'rm -f -- "$tmp"' EXIT HUP INT TERM
+cat > "$tmp"
+[ "$(wc -c < "$tmp")" -eq "$expected" ] || exit 1
+chown --reference="$dir" -- "$tmp"
+chmod 0644 -- "$tmp"
+sync -f -- "$tmp"
+stem=$name
+ext=
+case "$name" in
+    *.*) prefix=${name%.*}; if [ -n "$prefix" ]; then stem=$prefix; ext=.${name##*.}; fi ;;
+esac
+n=1
+while [ "$n" -le 100 ]; do
+    candidate=$name
+    if [ "$n" -gt 1 ]; then candidate="$stem ($n)$ext"; fi
+    dst="$dir/$candidate"
+    if ln -T -- "$tmp" "$dst" 2>/dev/null; then
+        printf '%s' "$candidate"
+        exit 0
+    fi
+    # A conflict may be a dangling symlink; never follow it or overwrite it.
+    if [ ! -e "$dst" ] && [ ! -L "$dst" ]; then exit 1; fi
+    n=$((n + 1))
+done
+exit 1
+"#;
+
+async fn write_via_userns(dir: PathBuf, name: String, bytes: Vec<u8>) -> Result<PathBuf> {
+    use tokio::io::AsyncWriteExt;
+    let mut child = tokio::process::Command::new("podman")
+        .args(["unshare", "sh", "-c", WRITE_VIA_USERNS, "sh"])
+        .arg(&dir)
+        .arg(&name)
+        .arg(bytes.len().to_string())
+        .kill_on_drop(true)
+        .stdin(std::process::Stdio::piped())
+        .stdout(std::process::Stdio::piped())
+        .stderr(std::process::Stdio::piped())
+        .spawn()
+        .context("Starting Files namespace writer")?;
+    let mut stdin = child.stdin.take().context("Files writer stdin missing")?;
+    let operation = async {
+        let fed = stdin.write_all(&bytes).await;
+        drop(stdin);
+        let output = child.wait_with_output().await?;
+        anyhow::ensure!(
+            output.status.success(),
+            "Files namespace writer failed: {}",
+            output.status
+        );
+        fed.context("Sending purchase bytes to Files")?;
+        let chosen =
+            String::from_utf8(output.stdout).context("Files writer returned an invalid name")?;
+        validate_filename(&chosen)?;
+        anyhow::ensure!(
+            (1..=100).any(|n| numbered_name(&name, n) == chosen),
+            "Files writer returned an unexpected name"
+        );
+        Ok(dir.join(chosen))
+    };
+    tokio::time::timeout(std::time::Duration::from_secs(120), operation)
+        .await
+        .context("Files namespace writer timed out")?
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -152,3 +343,231 @@ mod tests {
         assert_eq!(second, EnsureOutcome::Unchanged);
     }
 }
+
+#[cfg(test)]
+mod purchase_write_tests {
+    use super::*;
+    use std::{
+        collections::HashSet,
+        os::unix::fs::{symlink, PermissionsExt},
+    };
+
+    fn no_temps(dir: &Path) {
+        assert!(std::fs::read_dir(dir).unwrap().all(|e| !e
+            .unwrap()
+            .file_name()
+            .to_string_lossy()
+            .starts_with(".archy-saving")));
+    }
+
+    #[tokio::test]
+    async fn direct_write_uses_complete_bytes_and_preserves_originals() {
+        let dir = tempfile::tempdir().unwrap();
+        fs::write(dir.path().join("song.mp3"), b"original")
+            .await
+            .unwrap();
+        let target = save_new_file(dir.path(), "song.mp3", b"new").await.unwrap();
+        assert_eq!(target.file_name().unwrap(), "song (2).mp3");
+        assert_eq!(fs::read(target).await.unwrap(), b"new");
+        assert_eq!(
+            fs::read(dir.path().join("song.mp3")).await.unwrap(),
+            b"original"
+        );
+        no_temps(dir.path());
+    }
+
+    #[tokio::test]
+    async fn simultaneous_saves_publish_unique_complete_files() {
+        let dir = tempfile::tempdir().unwrap();
+        let mut tasks = Vec::new();
+        for n in 0..24u8 {
+            let dir = dir.path().to_owned();
+            tasks.push(tokio::spawn(async move {
+                let bytes = vec![n; 32768];
+                let path = save_new_file(&dir, "same.bin", &bytes).await.unwrap();
+                assert_eq!(fs::read(&path).await.unwrap(), bytes);
+                path
+            }));
+        }
+        let mut paths = HashSet::new();
+        for task in tasks {
+            assert!(paths.insert(task.await.unwrap()));
+        }
+        assert_eq!(paths.len(), 24);
+        no_temps(dir.path());
+    }
+
+    #[tokio::test]
+    async fn existing_directories_and_dangling_symlinks_are_conflicts() {
+        let dir = tempfile::tempdir().unwrap();
+        fs::create_dir(dir.path().join("name")).await.unwrap();
+        symlink("missing", dir.path().join("name (2)")).unwrap();
+        let path = save_new_file(dir.path(), "name", b"new").await.unwrap();
+        assert_eq!(path.file_name().unwrap(), "name (3)");
+        assert!(dir.path().join("name").is_dir());
+        assert!(fs::symlink_metadata(dir.path().join("name (2)"))
+            .await
+            .unwrap()
+            .is_symlink());
+        no_temps(dir.path());
+    }
+
+    #[tokio::test]
+    async fn invalid_names_and_symlink_destination_are_refused() {
+        let dir = tempfile::tempdir().unwrap();
+        for name in [
+            "",
+            ".",
+            "..",
+            "../escape",
+            "/absolute",
+            "a/b",
+            "a\\b",
+            "a\0b",
+        ] {
+            assert!(save_new_file(dir.path(), name, b"bytes").await.is_err());
+        }
+        let outside = tempfile::tempdir().unwrap();
+        symlink(outside.path(), dir.path().join("Music")).unwrap();
+        assert!(save_new_file(&dir.path().join("Music"), "song", b"bytes")
+            .await
+            .is_err());
+        assert_eq!(std::fs::read_dir(outside.path()).unwrap().count(), 0);
+    }
+
+    #[tokio::test]
+    async fn collision_limit_preserves_all_files_and_cleans_temporary_data() {
+        let dir = tempfile::tempdir().unwrap();
+        for n in 1..=100 {
+            fs::write(dir.path().join(numbered_name("a.txt", n)), b"keep")
+                .await
+                .unwrap();
+        }
+        assert!(save_new_file(dir.path(), "a.txt", b"new").await.is_err());
+        for n in 1..=100 {
+            assert_eq!(
+                fs::read(dir.path().join(numbered_name("a.txt", n)))
+                    .await
+                    .unwrap(),
+                b"keep"
+            );
+        }
+        no_temps(dir.path());
+    }
+
+    #[tokio::test]
+    async fn permission_fallback_is_exercised_without_skipping_as_root() {
+        let dir = tempfile::tempdir().unwrap();
+        let result = save_after_direct_result(
+            Err(std::io::ErrorKind::PermissionDenied.into()),
+            dir.path(),
+            "a",
+            b"abc",
+            |dir, name, bytes| async move {
+                assert_eq!(bytes, b"abc");
+                Ok(dir.join(name))
+            },
+        )
+        .await
+        .unwrap();
+        assert_eq!(result, dir.path().join("a"));
+        assert!(save_after_direct_result(
+            Err(std::io::ErrorKind::PermissionDenied.into()),
+            dir.path(),
+            "a",
+            b"abc",
+            |_, _, _| async { anyhow::bail!("namespace unavailable") }
+        )
+        .await
+        .unwrap_err()
+        .to_string()
+        .contains("namespace"));
+        assert!(save_after_direct_result(
+            Err(std::io::ErrorKind::StorageFull.into()),
+            dir.path(),
+            "a",
+            b"abc",
+            |_, _, _| async { panic!("disk full must not trigger permission fallback") }
+        )
+        .await
+        .is_err());
+    }
+
+    async fn run_script(
+        dir: &Path,
+        name: &str,
+        bytes: &[u8],
+        expected: usize,
+    ) -> std::process::Output {
+        use tokio::io::AsyncWriteExt;
+        let mut child = tokio::process::Command::new("sh")
+            .args(["-c", WRITE_VIA_USERNS, "sh"])
+            .arg(dir)
+            .arg(name)
+            .arg(expected.to_string())
+            .stdin(std::process::Stdio::piped())
+            .stdout(std::process::Stdio::piped())
+            .stderr(std::process::Stdio::piped())
+            .spawn()
+            .unwrap();
+        let mut input = child.stdin.take().unwrap();
+        input.write_all(bytes).await.unwrap();
+        drop(input);
+        child.wait_with_output().await.unwrap()
+    }
+
+    #[tokio::test]
+    async fn namespace_script_preserves_names_bytes_modes_and_existing_entries() {
+        let dir = tempfile::tempdir().unwrap();
+        let folder = dir.path().join("Music");
+        let name = "song ' $() ; #.mp3";
+        for n in 1..=2 {
+            let output = run_script(&folder, name, b"abc", 3).await;
+            assert!(
+                output.status.success(),
+                "{}",
+                String::from_utf8_lossy(&output.stderr)
+            );
+            let chosen = String::from_utf8(output.stdout).unwrap();
+            assert_eq!(chosen, numbered_name(name, n));
+            let path = folder.join(chosen);
+            assert_eq!(fs::read(&path).await.unwrap(), b"abc");
+            assert_eq!(
+                fs::metadata(path).await.unwrap().permissions().mode() & 0o777,
+                0o644
+            );
+        }
+        no_temps(&folder);
+    }
+
+    #[tokio::test]
+    async fn namespace_script_refuses_truncated_input_and_cleans_up() {
+        let dir = tempfile::tempdir().unwrap();
+        let output = run_script(dir.path(), "never.bin", b"partial", 100).await;
+        assert!(!output.status.success());
+        assert!(!dir.path().join("never.bin").exists());
+        no_temps(dir.path());
+    }
+
+    #[tokio::test]
+    async fn namespace_script_does_not_link_inside_existing_directory() {
+        let dir = tempfile::tempdir().unwrap();
+        fs::create_dir(dir.path().join("name")).await.unwrap();
+        symlink("missing", dir.path().join("name (2)")).unwrap();
+        let output = run_script(dir.path(), "name", b"abc", 3).await;
+        assert!(output.status.success());
+        assert_eq!(output.stdout, b"name (3)");
+        assert_eq!(
+            std::fs::read_dir(dir.path().join("name")).unwrap().count(),
+            0
+        );
+        no_temps(dir.path());
+    }
+
+    #[test]
+    fn names_keep_extensions_and_dotfiles() {
+        assert_eq!(numbered_name("a.tar.gz", 2), "a.tar (2).gz");
+        assert_eq!(numbered_name(".hidden", 2), ".hidden (2)");
+        assert_eq!(numbered_name("README", 2), "README (2)");
+    }
+}