docs: add a changelog

The project kept no change history of its own, so the tags were the
only record of what each release contained.

- Summarise 2.0.0, 2.0.1 and 2.0.2 by what changed for the user.
- Link the changelog from the README.

.gitea/workflows/release.yml

@@ -26,12 +26,16 @@ jobs:
           TARGET=x86_64-unknown-linux-musl
           ARCHIVE="mdrs-${VERSION}-${TARGET}.tar.gz"
           tar -czf "${ARCHIVE}" -C target/${TARGET}/release mdrs
+          # Published alongside the archive so `mdrs selfupdate` can check what it fetched.
+          sha256sum "${ARCHIVE}" > "${ARCHIVE}.sha256"
           echo "ARCHIVE=${ARCHIVE}" >> "$GITHUB_ENV"
       - name: Create release and upload asset
         uses: akkuman/gitea-release-action@v1
         with:
           token: ${{ github.token }}
-          files: ${{ env.ARCHIVE }}
+          files: |
+            ${{ env.ARCHIVE }}
+            ${{ env.ARCHIVE }}.sha256
 
   build-linux-aarch64:
     runs-on: ubuntu-latest
@@ -55,9 +59,13 @@ jobs:
           TARGET=aarch64-unknown-linux-musl
           ARCHIVE="mdrs-${VERSION}-${TARGET}.tar.gz"
           tar -czf "${ARCHIVE}" -C target/${TARGET}/release mdrs
+          # Published alongside the archive so `mdrs selfupdate` can check what it fetched.
+          sha256sum "${ARCHIVE}" > "${ARCHIVE}.sha256"
           echo "ARCHIVE=${ARCHIVE}" >> "$GITHUB_ENV"
       - name: Create release and upload asset
         uses: akkuman/gitea-release-action@v1
         with:
           token: ${{ github.token }}
-          files: ${{ env.ARCHIVE }}
+          files: |
+            ${{ env.ARCHIVE }}
+            ${{ env.ARCHIVE }}.sha256

CHANGELOG.md

@@ -0,0 +1,43 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+## [2.0.2] - 2026-09-04
+
+### Added
+- Accepted `-e` as the short form of `download --exclude`.
+
+### Changed
+- Transferred files larger than the memory available, in both directions.
+- Left an existing local file intact when a download fails part way through.
+- Showed the reason the server gave when it refused a request.
+- Updated dependencies.
+
+### Fixed
+- Kept a session working across concurrent runs, long server queues, and providers that rotate refresh tokens.
+- Listed a tree containing locked folders with `ls --json --recursive` instead of failing on the first one.
+- Other minor fixes to `ls --json` output, remote path handling, and the login cache.
+
+### Security
+- Verified the downloaded archive against the release checksum before `selfupdate` replaces the binary.
+
+## [2.0.1] - 2026-06-12
+
+### Added
+- Accepted a DOI in place of a path, as `remote:10.xxxx/prefix.ID[/sub/path]`.
+- Allowed `download` and the read-only commands to run without signing in.
+
+## [2.0.0] - 2026-04-20
+
+First release of the command-line client.
+
+### Added
+- Commands `config`, `login`, `logout`, `whoami`, `labs`, `ls`, `mkdir`, `upload`, `download`, `mv`, `cp`, `rm`, `chacl`, `metadata`, `file-metadata`, `version`, and `selfupdate`.
+- Release build scripts for Linux, macOS, and Windows.
+
+### Changed
+- Sped up transfers by working on folders and files in parallel, bounded by `MDRS_CLIENT_CONCURRENT`.
+
+### Fixed
+- Kept the session valid throughout a long-running transfer, and across concurrent runs.
+- Handled file and folder names with combining characters consistently.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mdrs-client-rust"
-version = "2.0.1"
+version = "2.0.2"
 edition = "2024"
 license = "MIT"
 authors = ["Neuroinformatics Unit, RIKEN CBS"]
@@ -12,18 +12,18 @@ path = "src/main.rs"
 
 [dependencies]
 clap = { version = "4.5", features = ["derive"] }
-reqwest = { version = "0.12", default-features = false, features = ["json", "multipart", "rustls-tls"] }
+reqwest = { version = "0.12", default-features = false, features = ["json", "multipart", "rustls-tls", "stream"] }
 serde = { version = "1.0", features = ["derive"] }
-serde_json = "1.0.150"
-tokio = { version = "1.52.3", features = ["full"] }
+serde_json = "1.0.151"
+tokio = { version = "1.53.1", features = ["full"] }
+tokio-util = { version = "0.7", features = ["io"] }
 futures = "0.3"
 dirs = "6.0.0"
-anyhow = "1.0.102"
+anyhow = "1.0.104"
 configparser = "3.2.0"
-validators = "0.25.3"
 sha2 = "0.11.0"
 rpassword = "7.5.4"
-base64 = "0.22"
+base64 = "0.23.1"
 fs2 = "0.4"
 ctrlc = "3"
 os_info = "3.15.0"

README.md

@@ -143,7 +143,7 @@ Download a file or folder from a remote path. You can also specify a DOI path.
 mdrs download neurodata:/NIU/Repository/TEST/sample.dat ./
 mdrs download -r neurodata:/NIU/Repository/TEST/dataset/ ./
 mdrs download -p SHARING_PASSWORD neurodata:/NIU/Repository/PW_Open/Readme.dat ./
-mdrs download -r --exclude /NIU/Repository/TEST/dataset/skip neurodata:/NIU/Repository/TEST/dataset/ ./
+mdrs download -r -e /NIU/Repository/TEST/dataset/skip neurodata:/NIU/Repository/TEST/dataset/ ./
 mdrs download -r --skip-if-exists neurodata:/NIU/Repository/TEST/dataset/ ./
 
 # DOI access examples:
@@ -224,7 +224,8 @@ mdrs version
 ### selfupdate
 
 Update the current `mdrs` binary to the latest published release for
-the same build target.
+the same build target. The downloaded archive is checked against the `.sha256`
+asset the release publishes; a release without one is reported as unverified.
 
 ```shell
 mdrs selfupdate
@@ -240,6 +241,10 @@ mdrs --help
 mdrs upload --help
 ```
 
+## Changelog
+
+See [CHANGELOG.md](./CHANGELOG.md) for the full change history.
+
 ## License
 
 [MIT](LICENSE) © 2026- Neuroinformatics Unit, RIKEN CBS

scripts/build-release-linux.sh

@@ -58,7 +58,10 @@ for TARGET in "${TARGETS[@]}"; do
 
   ARCHIVE="mdrs-${VERSION}-${TARGET}.tar.gz"
   tar -czf "${ARCHIVE}" -C "target/${TARGET}/release" mdrs
-  ARCHIVES+=("${ARCHIVE}")
+  # Uploaded alongside the archive so `mdrs selfupdate` can check what it fetched.
+  sha256sum "${ARCHIVE}" > "${ARCHIVE}.sha256" 2>/dev/null \
+    || shasum -a 256 "${ARCHIVE}" > "${ARCHIVE}.sha256"
+  ARCHIVES+=("${ARCHIVE}" "${ARCHIVE}.sha256")
   echo "    Created: ${ARCHIVE}"
 done
 

scripts/build-release-macos.sh

@@ -46,7 +46,10 @@ for TARGET in "${TARGETS[@]}"; do
 
   ARCHIVE="mdrs-${VERSION}-${TARGET}.tar.gz"
   tar -czf "${ARCHIVE}" -C "target/${TARGET}/release" mdrs
-  ARCHIVES+=("${ARCHIVE}")
+  # Uploaded alongside the archive so `mdrs selfupdate` can check what it fetched.
+  sha256sum "${ARCHIVE}" > "${ARCHIVE}.sha256" 2>/dev/null \
+    || shasum -a 256 "${ARCHIVE}" > "${ARCHIVE}.sha256"
+  ARCHIVES+=("${ARCHIVE}" "${ARCHIVE}.sha256")
   echo "    Created: ${ARCHIVE}"
 done
 

scripts/build-release-windows.ps1

@@ -55,6 +55,10 @@ cargo build --release --target $Target
 
 $Archive = "mdrs-$Version-$Target.zip"
 Compress-Archive -Force -Path "target\$Target\release\mdrs.exe" -DestinationPath $Archive
+# Written alongside the archive so `mdrs selfupdate` can check what it fetched.
+$Checksum = "$Archive.sha256"
+$Hash = (Get-FileHash -Algorithm SHA256 -Path $Archive).Hash.ToLower()
+"$Hash  $Archive" | Set-Content -NoNewline -Encoding ascii $Checksum
 Write-Host "    Created: $Archive"
 
 # Upload to Gitea if token is provided
@@ -87,14 +91,16 @@ $Release = Invoke-RestMethod -Method Get -Uri "$ServerUrl/api/v1/repos/$Reposito
     -Headers @{ Authorization = "Bearer $GiteaToken" }
 $ReleaseId = $Release.id
 
-Write-Host "==> Uploading $Archive (release id: $ReleaseId) ..."
-$ArchivePath = Join-Path $RepoRoot $Archive
-& curl.exe -sf -X POST `
-    -H "Authorization: Bearer $GiteaToken" `
-    -F "attachment=@$ArchivePath" `
-    "$ServerUrl/api/v1/repos/$Repository/releases/$ReleaseId/assets" | Out-Null
-if ($LASTEXITCODE -ne 0) { Write-Error "Upload failed (exit code $LASTEXITCODE)"; exit 1 }
-Write-Host "    Done."
+foreach ($Name in @($Archive, $Checksum)) {
+    Write-Host "==> Uploading $Name (release id: $ReleaseId) ..."
+    $AssetPath = Join-Path $RepoRoot $Name
+    & curl.exe -sf -X POST `
+        -H "Authorization: Bearer $GiteaToken" `
+        -F "attachment=@$AssetPath" `
+        "$ServerUrl/api/v1/repos/$Repository/releases/$ReleaseId/assets" | Out-Null
+    if ($LASTEXITCODE -ne 0) { Write-Error "Upload failed (exit code $LASTEXITCODE)"; exit 1 }
+    Write-Host "    Done."
+}
 
 Write-Host ""
 Write-Host "==> Upload complete: $ServerUrl/$Repository/releases/tag/$Tag"

src/api/doi.rs

@@ -1,6 +1,6 @@
 use crate::connection::MDRSConnection;
+use crate::error::response_error;
 use crate::models::doi::DoiResponse;
-use anyhow::bail;
 
 impl MDRSConnection {
     /// Retrieve the folder associated with a DOI suffix ID (GET v3/doi/{id}/).
@@ -10,7 +10,7 @@ impl MDRSConnection {
     pub async fn retrieve_doi(&self, id: &str) -> Result<DoiResponse, anyhow::Error> {
         let resp = self.get(&format!("v3/doi/{}/", id)).await?;
         if !resp.status().is_success() {
-            bail!("DOI lookup failed: {}", resp.status());
+            return Err(response_error("DOI lookup failed", resp).await);
         }
         Ok(resp.json::<DoiResponse>().await?)
     }

src/api/files.rs

@@ -1,8 +1,30 @@
 use crate::connection::{ApiRequestLimiter, MDRSConnection};
+use crate::error::response_error;
 pub use crate::models::file::File;
-use anyhow::bail;
 use unicode_normalization::UnicodeNormalization;
 
+/// Read and write size for a streamed transfer. Large enough that the syscalls are not
+/// what limits the transfer, small enough that ten of them in flight cost little.
+const TRANSFER_CHUNK_BYTES: usize = 64 * 1024;
+
+/// Name a scratch file beside the destination for a download in progress.
+///
+/// Beside it, so the move into place is a rename within one directory and cannot fail
+/// half way. Unique, so two transfers heading for the same name cannot clear up after
+/// each other.
+fn partial_path(dest: &std::path::Path) -> std::path::PathBuf {
+    use std::sync::atomic::{AtomicU64, Ordering};
+    static COUNTER: AtomicU64 = AtomicU64::new(0);
+
+    let mut name = dest.file_name().unwrap_or_default().to_os_string();
+    name.push(format!(
+        ".{}-{}.mdrspart",
+        std::process::id(),
+        COUNTER.fetch_add(1, Ordering::Relaxed)
+    ));
+    dest.with_file_name(name)
+}
+
 #[derive(serde::Deserialize)]
 struct FileListResponse {
     pub next: Option<String>,
@@ -21,7 +43,7 @@ impl MDRSConnection {
             ];
             let resp = self.get_with_query("v3/files/", &params).await?;
             if !resp.status().is_success() {
-                anyhow::bail!("List files failed: {}", resp.status());
+                return Err(response_error("List files failed", resp).await);
             }
             let list: FileListResponse = resp.json().await?;
             let has_next = list.next.is_some();
@@ -50,7 +72,7 @@ impl MDRSConnection {
             let _permit = limiter.acquire().await?;
             let resp = self.get_with_query("v3/files/", &params).await?;
             if !resp.status().is_success() {
-                anyhow::bail!("List files failed: {}", resp.status());
+                return Err(response_error("List files failed", resp).await);
             }
             let list: FileListResponse = resp.json().await?;
             let has_next = list.next.is_some();
@@ -79,15 +101,51 @@ impl MDRSConnection {
             .to_string_lossy()
             .nfc()
             .collect();
-        let file_bytes = tokio::fs::read(file_path).await?;
-        let part = multipart::Part::bytes(file_bytes).file_name(file_name.clone());
-        let form = multipart::Form::new()
-            .text("folder_id", folder_id.to_string())
-            .part("file", part);
+        // The file is handed to the request as a stream rather than a buffer: a
+        // repository holds recordings far larger than the machine's memory, and ten of
+        // them may be in flight at once. The length travels with it so the request keeps
+        // a Content-Length and does not have to be sent chunked.
+        let build_form = || async {
+            let file = tokio::fs::File::open(file_path).await?;
+            let length = file.metadata().await?.len();
+            let stream = tokio_util::io::ReaderStream::with_capacity(file, TRANSFER_CHUNK_BYTES);
+            let part =
+                multipart::Part::stream_with_length(reqwest::Body::wrap_stream(stream), length)
+                    .file_name(file_name.clone());
+            Ok::<_, anyhow::Error>(
+                multipart::Form::new()
+                    .text("folder_id", folder_id.to_string())
+                    .part("file", part),
+            )
+        };
         let _permit = limiter.acquire().await?;
-        let resp = self.post_multipart("v3/files/", form).await?;
+        let sent_with = self.token.clone();
+        let resp = self
+            .post_multipart("v3/files/", build_form().await?)
+            .await?;
+        if resp.status() != reqwest::StatusCode::UNAUTHORIZED {
+            if !resp.status().is_success() {
+                return Err(response_error("Upload failed", resp).await);
+            }
+            return Ok(());
+        }
+        // The body reached the server, but it may have waited to be served for longer
+        // than the access token it was sent with lived. Re-reading the file and sending
+        // it again is only worth it if the token has actually moved on: any other reason
+        // for the refusal would just cost a second full transfer to be told the same.
+        let retry_conn = self.connection_with_fresh_token_for_retry().await?;
+        if retry_conn.token == sent_with {
+            return Err(response_error("Upload failed", resp).await);
+        }
+        let resp = retry_conn
+            .post_multipart("v3/files/", build_form().await?)
+            .await?;
+        if resp.status() == reqwest::StatusCode::UNAUTHORIZED {
+            // Refused twice, the second time with a token that was current when it left.
+            bail!(crate::connection::SERVER_BUSY_MESSAGE);
+        }
         if !resp.status().is_success() {
-            bail!("Upload failed: {}", resp.status());
+            return Err(response_error("Upload failed", resp).await);
         }
         Ok(())
     }
@@ -99,14 +157,310 @@ impl MDRSConnection {
         dest: &str,
         limiter: &ApiRequestLimiter,
     ) -> Result<(), anyhow::Error> {
+        use futures::StreamExt;
+        use tokio::io::AsyncWriteExt;
+
         let _permit = limiter.acquire().await?;
+        let dest_path = std::path::Path::new(dest);
+        // Checked before anything is fetched. The finished file is moved into place, and
+        // a rename would replace a destination the mode says is protected, which is not
+        // what this client or the Python one has ever done.
+        if dest_path.exists() {
+            tokio::fs::OpenOptions::new()
+                .write(true)
+                .open(dest_path)
+                .await
+                .map_err(|e| anyhow::anyhow!("Cannot write `{}`: {}", dest, e))?;
+        }
         let resp = self.get_url(url).await?;
         if !resp.status().is_success() {
-            bail!("Download failed: {}", resp.status());
+            return Err(response_error("Download failed", resp).await);
+        }
+        // Written as it arrives, into a scratch file that is moved into place only once
+        // the whole body has landed. Holding the body in memory first would cost the size
+        // of the file, times however many transfers are running; writing straight to the
+        // destination would destroy whatever is already there the moment the transfer
+        // starts, and leave a truncated file behind if it does not finish.
+        let part_path = partial_path(dest_path);
+        let result = async {
+            let mut file = tokio::io::BufWriter::with_capacity(
+                TRANSFER_CHUNK_BYTES,
+                tokio::fs::File::create(&part_path).await?,
+            );
+            let mut stream = resp.bytes_stream();
+            while let Some(chunk) = stream.next().await {
+                file.write_all(&chunk?).await?;
+            }
+            file.flush().await?;
+            Ok::<(), anyhow::Error>(())
+        }
+        .await;
+        match result {
+            Ok(()) => Ok(tokio::fs::rename(&part_path, dest_path).await?),
+            Err(err) => {
+                // Only the scratch file goes. Anything already at the destination was not
+                // written by this transfer and is not this transfer's to remove.
+                let _ = tokio::fs::remove_file(&part_path).await;
+                Err(err)
+            }
         }
-        let bytes = resp.bytes().await?;
-        drop(_permit);
-        tokio::fs::write(dest, &bytes).await?;
-        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod transfer_tests {
+    use super::*;
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+    use tokio::net::TcpListener;
+
+    /// Read one HTTP request in full, using its Content-Length to know where it ends.
+    async fn read_request(stream: &mut tokio::net::TcpStream) -> (String, Vec<u8>) {
+        let mut buf = Vec::new();
+        let mut chunk = [0u8; 8192];
+        let header_end = loop {
+            let n = stream.read(&mut chunk).await.unwrap();
+            buf.extend_from_slice(&chunk[..n]);
+            if let Some(pos) = buf.windows(4).position(|w| w == b"\r\n\r\n") {
+                break pos + 4;
+            }
+            assert!(n > 0, "connection closed before the headers ended");
+        };
+        let head = String::from_utf8_lossy(&buf[..header_end]).to_string();
+        let length: usize = head
+            .lines()
+            .find_map(|l| {
+                l.to_ascii_lowercase()
+                    .strip_prefix("content-length:")
+                    .map(|v| v.trim().to_string())
+            })
+            .expect("request must carry a Content-Length")
+            .parse()
+            .unwrap();
+        while buf.len() < header_end + length {
+            let n = stream.read(&mut chunk).await.unwrap();
+            assert!(n > 0, "connection closed before the body ended");
+            buf.extend_from_slice(&chunk[..n]);
+        }
+        (head, buf[header_end..].to_vec())
+    }
+
+    /// The file goes out as a stream, and the request still declares its length, so the
+    /// server is not asked to accept a chunked upload.
+    #[tokio::test]
+    async fn an_upload_streams_the_file_with_a_declared_length() {
+        let payload: Vec<u8> = (0..300_000u32).map(|i| (i % 251) as u8).collect();
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("recording.dat");
+        std::fs::write(&path, &payload).unwrap();
+
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let expected = payload.clone();
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let (head, body) = read_request(&mut stream).await;
+            stream
+                .write_all(b"HTTP/1.1 200 OK\r\ncontent-length: 15\r\nconnection: close\r\n\r\n{\"id\":\"new\"}")
+                .await
+                .unwrap();
+            (head, body, expected)
+        });
+
+        let conn = MDRSConnection::new(&format!("http://{addr}"));
+        let limiter = ApiRequestLimiter::new(1);
+        conn.upload_file_limited("folder-1", path.to_str().unwrap(), &limiter)
+            .await
+            .unwrap();
+
+        let (head, body, expected) = server.await.unwrap();
+        assert!(
+            !head
+                .to_ascii_lowercase()
+                .contains("transfer-encoding: chunked"),
+            "the upload must not be chunked:\n{head}"
+        );
+        assert!(
+            body.windows(expected.len()).any(|w| w == expected),
+            "the file bytes must reach the server"
+        );
+        assert!(
+            body.windows(8).any(|w| w == b"folder-1"),
+            "the folder id must reach the server"
+        );
+        assert!(
+            String::from_utf8_lossy(&body).contains("recording.dat"),
+            "the file name must reach the server"
+        );
+    }
+
+    /// The body is written to disk as it arrives rather than being held whole.
+    #[tokio::test]
+    async fn a_download_writes_what_the_server_sent() {
+        let payload: Vec<u8> = (0..300_000u32).map(|i| (i % 241) as u8).collect();
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let served = payload.clone();
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut chunk = [0u8; 4096];
+            let _ = stream.read(&mut chunk).await.unwrap();
+            let head = format!(
+                "HTTP/1.1 200 OK\r\ncontent-length: {}\r\nconnection: close\r\n\r\n",
+                served.len()
+            );
+            stream.write_all(head.as_bytes()).await.unwrap();
+            stream.write_all(&served).await.unwrap();
+        });
+
+        let dir = tempfile::tempdir().unwrap();
+        let dest = dir.path().join("out.dat");
+        let conn = MDRSConnection::new(&format!("http://{addr}"));
+        let limiter = ApiRequestLimiter::new(1);
+        conn.download_file_limited(
+            &format!("http://{addr}/v3/files/1/download/"),
+            dest.to_str().unwrap(),
+            &limiter,
+        )
+        .await
+        .unwrap();
+        server.await.unwrap();
+
+        assert_eq!(std::fs::read(&dest).unwrap(), payload);
+    }
+
+    /// A transfer that dies part way must not take the copy already on disk with it.
+    #[tokio::test]
+    async fn an_interrupted_download_leaves_the_existing_file_intact() {
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut chunk = [0u8; 4096];
+            let _ = stream.read(&mut chunk).await.unwrap();
+            // Promises 300000 bytes, sends 1000, then hangs up.
+            stream
+                .write_all(
+                    b"HTTP/1.1 200 OK\r\ncontent-length: 300000\r\nconnection: close\r\n\r\n",
+                )
+                .await
+                .unwrap();
+            stream.write_all(&vec![b'x'; 1000]).await.unwrap();
+            stream.shutdown().await.unwrap();
+        });
+
+        let dir = tempfile::tempdir().unwrap();
+        let dest = dir.path().join("existing.dat");
+        std::fs::write(&dest, b"the copy already here").unwrap();
+
+        let conn = MDRSConnection::new(&format!("http://{addr}"));
+        let limiter = ApiRequestLimiter::new(1);
+        let outcome = conn
+            .download_file_limited(
+                &format!("http://{addr}/v3/files/1/download/"),
+                dest.to_str().unwrap(),
+                &limiter,
+            )
+            .await;
+        server.await.unwrap();
+
+        assert!(outcome.is_err(), "a truncated body is a failed download");
+        assert_eq!(std::fs::read(&dest).unwrap(), b"the copy already here");
+        let leftovers: Vec<_> = std::fs::read_dir(dir.path())
+            .unwrap()
+            .map(|e| e.unwrap().file_name().to_string_lossy().to_string())
+            .filter(|name| name != "existing.dat")
+            .collect();
+        assert!(
+            leftovers.is_empty(),
+            "no scratch file may be left: {leftovers:?}"
+        );
+    }
+
+    /// A destination this call could not even open is not a file it may delete.
+    #[cfg(unix)]
+    #[tokio::test]
+    async fn a_download_that_cannot_be_written_leaves_the_existing_file_intact() {
+        use std::os::unix::fs::PermissionsExt;
+
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut chunk = [0u8; 4096];
+            let _ = stream.read(&mut chunk).await.unwrap();
+            stream
+                .write_all(b"HTTP/1.1 200 OK\r\ncontent-length: 2\r\nconnection: close\r\n\r\nhi")
+                .await
+                .unwrap();
+        });
+
+        // A writable directory holding a file this process may not open for writing.
+        // That is what separates "could not write it" from "may delete it": unlink needs
+        // the directory, not the file.
+        let dir = tempfile::tempdir().unwrap();
+        let dest = dir.path().join("precious.dat");
+        std::fs::write(&dest, b"do not touch").unwrap();
+        let mut perms = std::fs::metadata(&dest).unwrap().permissions();
+        perms.set_mode(0o444);
+        std::fs::set_permissions(&dest, perms).unwrap();
+        if std::fs::OpenOptions::new().write(true).open(&dest).is_ok() {
+            // Running with rights that ignore the mode, so there is nothing to observe.
+            return;
+        }
+
+        let conn = MDRSConnection::new(&format!("http://{addr}"));
+        let limiter = ApiRequestLimiter::new(1);
+        let outcome = conn
+            .download_file_limited(
+                &format!("http://{addr}/v3/files/1/download/"),
+                dest.to_str().unwrap(),
+                &limiter,
+            )
+            .await;
+        // Nothing was fetched, so the stub is still waiting to be connected to.
+        server.abort();
+
+        let message = outcome.unwrap_err().to_string();
+        assert!(
+            message.starts_with("Cannot write "),
+            "the refusal must name the problem, got: {message}"
+        );
+        assert_eq!(std::fs::read(&dest).unwrap(), b"do not touch");
+    }
+
+    /// A refused download leaves nothing behind that a later run could mistake for the file.
+    #[tokio::test]
+    async fn a_refused_download_leaves_no_file() {
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut chunk = [0u8; 4096];
+            let _ = stream.read(&mut chunk).await.unwrap();
+            let body = r#"{"type":"client_error","errors":[{"code":"permission_denied","detail":"Access is denied.","attr":null}]}"#;
+            let head = format!(
+                "HTTP/1.1 403 Forbidden\r\ncontent-type: application/json\r\ncontent-length: {}\r\nconnection: close\r\n\r\n{}",
+                body.len(),
+                body
+            );
+            stream.write_all(head.as_bytes()).await.unwrap();
+        });
+
+        let dir = tempfile::tempdir().unwrap();
+        let dest = dir.path().join("out.dat");
+        let conn = MDRSConnection::new(&format!("http://{addr}"));
+        let limiter = ApiRequestLimiter::new(1);
+        let err = conn
+            .download_file_limited(
+                &format!("http://{addr}/v3/files/1/download/"),
+                dest.to_str().unwrap(),
+                &limiter,
+            )
+            .await
+            .unwrap_err();
+        server.await.unwrap();
+
+        assert_eq!(err.to_string(), "Download failed: Access is denied.");
+        assert!(!dest.exists());
     }
 }

src/api/folders.rs

@@ -1,4 +1,5 @@
 use crate::connection::{ApiRequestLimiter, MDRSConnection};
+use crate::error::response_error;
 pub use crate::models::folder::{FolderDetail, FolderSimple};
 use anyhow::{anyhow, bail};
 
@@ -15,7 +16,7 @@ impl MDRSConnection {
         ];
         let resp = self.get_with_query("v3/folders/", &params).await?;
         if !resp.status().is_success() {
-            bail!("List folders failed: {}", resp.status());
+            return Err(response_error("List folders failed", resp).await);
         }
         Ok(resp.json::<Vec<FolderSimple>>().await?)
     }
@@ -34,7 +35,7 @@ impl MDRSConnection {
         let _permit = limiter.acquire().await?;
         let resp = self.get_with_query("v3/folders/", &params).await?;
         if !resp.status().is_success() {
-            bail!("List folders failed: {}", resp.status());
+            return Err(response_error("List folders failed", resp).await);
         }
         Ok(resp.json::<Vec<FolderSimple>>().await?)
     }
@@ -43,7 +44,7 @@ impl MDRSConnection {
     pub async fn retrieve_folder(&self, id: &str) -> Result<FolderDetail, anyhow::Error> {
         let resp = self.get(&format!("v3/folders/{}/", id)).await?;
         if !resp.status().is_success() {
-            bail!("Retrieve folder failed: {}", resp.status());
+            return Err(response_error("Retrieve folder failed", resp).await);
         }
         Ok(resp.json::<FolderDetail>().await?)
     }
@@ -57,7 +58,7 @@ impl MDRSConnection {
         let _permit = limiter.acquire().await?;
         let resp = self.get(&format!("v3/folders/{}/", id)).await?;
         if !resp.status().is_success() {
-            bail!("Retrieve folder failed: {}", resp.status());
+            return Err(response_error("Retrieve folder failed", resp).await);
         }
         Ok(resp.json::<FolderDetail>().await?)
     }
@@ -94,7 +95,11 @@ impl MDRSConnection {
         let _permit = limiter.acquire().await?;
         let resp = self.post_json("v3/folders/", &body).await?;
         if !resp.status().is_success() {
-            bail!("Failed to create remote folder: {}", folder_name);
+            return Err(response_error(
+                &format!("Failed to create remote folder `{}`", folder_name),
+                resp,
+            )
+            .await);
         }
         let json: serde_json::Value = resp.json().await?;
         json["id"]
@@ -116,7 +121,7 @@ impl MDRSConnection {
             bail!("Password is incorrect.");
         }
         if !resp.status().is_success() {
-            bail!("Folder auth failed: {}", resp.status());
+            return Err(response_error("Folder auth failed", resp).await);
         }
         Ok(())
     }
@@ -140,7 +145,7 @@ impl MDRSConnection {
             bail!("Password is incorrect.");
         }
         if !resp.status().is_success() {
-            bail!("Folder auth failed: {}", resp.status());
+            return Err(response_error("Folder auth failed", resp).await);
         }
         Ok(())
     }

src/api/laboratories.rs

@@ -1,4 +1,5 @@
 use crate::connection::MDRSConnection;
+use crate::error::response_error;
 use crate::models::laboratory::{Laboratories, Laboratory};
 use serde::Deserialize;
 
@@ -12,7 +13,7 @@ impl MDRSConnection {
     pub async fn list_laboratories(&self) -> Result<Laboratories, anyhow::Error> {
         let resp = self.get("v3/laboratories/").await?;
         if !resp.status().is_success() {
-            anyhow::bail!("List laboratories failed: {}", resp.status());
+            return Err(response_error("List laboratories failed", resp).await);
         }
         // The API may return a paginated object or a direct array
         let text = resp.text().await?;

src/api/users.rs

@@ -1,7 +1,14 @@
 use crate::connection::MDRSConnection;
+use crate::error::response_error;
 use crate::models::user::User as ModelUser;
-use anyhow::bail;
 use serde::Deserialize;
+use std::time::Duration;
+
+/// Bound the refresh on its own: the caller holds a lock that spans processes while this
+/// runs, so a provider that accepts the connection and then goes quiet would stall every
+/// other request on this machine rather than just this one. Uploads are served by a
+/// separate instance, so this one is not queued behind them and has no reason to be slow.
+const TOKEN_REFRESH_TIMEOUT: Duration = Duration::from_secs(30);
 
 /// Full API response shape from GET v3/users/current/
 #[derive(Debug, Deserialize)]
@@ -20,6 +27,16 @@ struct UsersCurrentResponseLaboratory {
 #[derive(Deserialize)]
 struct TokenRefreshResponse {
     access: String,
+    /// Present when the provider rotates refresh tokens, absent when it does not,
+    /// so the caller keeps the token it already holds if nothing new arrives.
+    #[serde(default)]
+    refresh: Option<String>,
+}
+
+/// The token pair a refresh yields.
+pub struct RefreshedToken {
+    pub access: String,
+    pub refresh: Option<String>,
 }
 
 impl MDRSConnection {
@@ -27,7 +44,7 @@ impl MDRSConnection {
     pub async fn get_current_user(&self) -> Result<ModelUser, anyhow::Error> {
         let resp = self.get("v3/users/current/").await?;
         if !resp.status().is_success() {
-            bail!("Get current user failed: {}", resp.status());
+            return Err(response_error("Get current user failed", resp).await);
         }
         let obj = resp.json::<UsersApiCurrentResponse>().await?;
         let laboratory_ids = obj.laboratories.into_iter().map(|l| l.id).collect();
@@ -40,19 +57,83 @@ impl MDRSConnection {
     }
 
     /// Refresh the access token using the refresh token.
-    /// POST v3/users/token/refresh/ {refresh: ...} -> {access: new_access}
-    pub async fn token_refresh(&self, refresh_token: &str) -> Result<String, anyhow::Error> {
+    /// POST v3/users/token/refresh/ {refresh: ...} -> {access, refresh?}
+    ///
+    /// A rotating provider answers with a new refresh token and stops honouring the one
+    /// that was sent, so both halves of the reply have to be kept.
+    pub async fn token_refresh(
+        &self,
+        refresh_token: &str,
+    ) -> Result<RefreshedToken, anyhow::Error> {
         let body = serde_json::json!({ "refresh": refresh_token });
         let resp = self
             .client
             .post(self.build_url("v3/users/token/refresh/"))
             .json(&body)
+            .timeout(TOKEN_REFRESH_TIMEOUT)
             .send()
             .await?;
         if !resp.status().is_success() {
-            bail!("Token refresh failed: {}", resp.status());
+            return Err(response_error("Token refresh failed", resp).await);
         }
         let r: TokenRefreshResponse = resp.json().await?;
-        Ok(r.access)
+        Ok(RefreshedToken {
+            access: r.access,
+            refresh: r.refresh,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+    use tokio::net::TcpListener;
+
+    async fn refresh_against_stub(body: &'static str) -> RefreshedToken {
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut buf = [0u8; 4096];
+            let n = stream.read(&mut buf).await.unwrap();
+            let req = String::from_utf8_lossy(&buf[..n]);
+            assert!(req.starts_with("POST /v3/users/token/refresh/ HTTP/1.1"));
+            assert!(req.contains("\"refresh\":\"old-refresh\""));
+
+            let response = format!(
+                "HTTP/1.1 200 OK\r\ncontent-type: application/json\r\ncontent-length: {}\r\nconnection: close\r\n\r\n{}",
+                body.len(),
+                body
+            );
+            stream.write_all(response.as_bytes()).await.unwrap();
+        });
+
+        let conn = MDRSConnection::new(&format!("http://{addr}"));
+        let refreshed = conn.token_refresh("old-refresh").await.unwrap();
+        server.await.unwrap();
+        refreshed
+    }
+
+    /// A rotating provider stops honouring the token that was sent, so the reply's
+    /// refresh token has to reach the caller rather than being dropped.
+    #[tokio::test]
+    async fn token_refresh_returns_the_rotated_refresh_token() {
+        let refreshed =
+            refresh_against_stub(r#"{"access":"new-access","refresh":"new-refresh"}"#).await;
+
+        assert_eq!(refreshed.access, "new-access");
+        assert_eq!(refreshed.refresh.as_deref(), Some("new-refresh"));
+    }
+
+    /// A provider that does not rotate answers with the access token alone, and the
+    /// caller keeps the refresh token it already holds.
+    #[tokio::test]
+    async fn token_refresh_reports_no_rotation_when_the_reply_omits_it() {
+        let refreshed = refresh_against_stub(r#"{"access":"new-access"}"#).await;
+
+        assert_eq!(refreshed.access, "new-access");
+        assert_eq!(refreshed.refresh, None);
     }
 }

src/cache/mod.rs

@@ -139,14 +139,32 @@ fn write_cache_file(cache_path: &Path, cache: &Cache) -> Result<(), anyhow::Erro
 }
 
 fn parse_cache(remote: &str, data: &str) -> Result<Cache, anyhow::Error> {
-    serde_json::from_str::<Cache>(data).map_err(|e| {
+    let cache = serde_json::from_str::<Cache>(data).map_err(|e| {
         anyhow!(
             "Cache for `{}` is invalid or outdated ({}). Run `mdrs login {}` to refresh it.",
             remote,
             e,
             remote
         )
-    })
+    })?;
+    // The digest is what says the file is still the one this client wrote. The Python
+    // client checks it on every read and the two share the file, so a cache one of them
+    // would refuse must not be honoured by the other.
+    let expected = compute_digest(
+        cache.user.as_ref(),
+        &cache.token.access,
+        &cache.token.refresh,
+        &cache.laboratories,
+    );
+    if cache.digest != expected {
+        bail!(
+            "Cache for `{}` has been altered or was written by an incompatible version. \
+             Run `mdrs login {}` to refresh it.",
+            remote,
+            remote
+        );
+    }
+    Ok(cache)
 }
 
 fn load_cache_from_dir(remote: &str, config_dir: &Path) -> Result<Cache, anyhow::Error> {
@@ -213,7 +231,11 @@ fn load_cache_if_present_from_dir(
     };
     let cache = match parse_cache(remote, &data) {
         Ok(cache) => cache,
-        Err(_) => {
+        Err(e) => {
+            // Said out loud before the credentials go. The alternative is a command that
+            // quietly carries on anonymously and fails later for a reason that looks
+            // unrelated to the cache it just threw away.
+            eprintln!("{e}");
             remove_cache_in_dir(remote, config_dir)?;
             return Ok(None);
         }
@@ -290,6 +312,9 @@ pub async fn load_cache_with_token_refresh(remote: &str) -> Result<Cache, anyhow
     let lock_file = fs::OpenOptions::new()
         .write(true)
         .create(true)
+        // Nothing is ever written into it: the file exists only to be flocked, and
+        // truncating it would touch a file other processes are holding open.
+        .truncate(false)
         .open(&lock_path)?;
     lock_file.lock_exclusive()?;
 
@@ -331,6 +356,9 @@ async fn load_cache_with_token_refresh_optional_from_dir(
     let lock_file = fs::OpenOptions::new()
         .write(true)
         .create(true)
+        // Nothing is ever written into it: the file exists only to be flocked, and
+        // truncating it would touch a file other processes are holding open.
+        .truncate(false)
         .open(&lock_path)?;
     lock_file.lock_exclusive()?;
 
@@ -387,10 +415,13 @@ async fn refresh_and_persist_in_dir(
         .ok_or_else(|| anyhow!("Remote `{}` is not configured.", remote))?;
     let conn = MDRSConnection::new(&url);
 
-    let new_access = conn.token_refresh(&cache.token.refresh).await?;
+    let refreshed = conn.token_refresh(&cache.token.refresh).await?;
 
     let mut updated_cache = cache.clone();
-    updated_cache.token.access = new_access;
+    updated_cache.token.access = refreshed.access;
+    if let Some(refresh) = refreshed.refresh {
+        updated_cache.token.refresh = refresh;
+    }
     updated_cache.digest = compute_digest(
         updated_cache.user.as_ref(),
         &updated_cache.token.access,
@@ -440,7 +471,7 @@ mod tests {
     use tempfile::tempdir;
 
     fn sample_cache(username: &str) -> Cache {
-        Cache {
+        let mut cache = Cache {
             user: Some(CacheUser {
                 id: 1,
                 username: username.to_string(),
@@ -459,8 +490,15 @@ mod tests {
                     full_name: "Laboratory".to_string(),
                 }],
             },
-            digest: format!("digest-{username}"),
-        }
+            digest: String::new(),
+        };
+        cache.digest = compute_digest(
+            cache.user.as_ref(),
+            &cache.token.access,
+            &cache.token.refresh,
+            &cache.laboratories,
+        );
+        cache
     }
 
     fn remote_name(prefix: &str, config_dir: &Path) -> String {
@@ -572,6 +610,25 @@ mod tests {
         assert!(loaded.is_none());
     }
 
+    /// A cache whose contents no longer match its digest is not a session to act on.
+    #[test]
+    fn load_cache_refuses_a_tampered_cache() {
+        let dir = tempdir().unwrap();
+        let remote = remote_name("tampered", dir.path());
+        let mut cache = sample_cache("alice");
+        persist_cache_in_dir(&remote, dir.path(), &cache).unwrap();
+
+        // Someone edits the stored token but leaves the digest as it was.
+        cache.token.access = "someone-elses-access".to_string();
+        let cache_path = cache_file_path_in(dir.path(), &remote);
+        fs::write(&cache_path, serde_json::to_vec_pretty(&cache).unwrap()).unwrap();
+        invalidate_cached_entry(dir.path(), &remote);
+
+        let err = load_cache_from_dir(&remote, dir.path()).unwrap_err();
+
+        assert!(err.to_string().contains("has been altered"));
+    }
+
     #[test]
     fn load_cache_if_present_clears_invalid_cache() {
         let dir = tempdir().unwrap();
@@ -594,6 +651,13 @@ mod tests {
         let mut cache = sample_cache("alice");
         cache.token.access = make_jwt_with_exp(0);
         cache.token.refresh = make_jwt_with_exp(0);
+        // Re-stamped, so this exercises the expired session rather than the digest check.
+        cache.digest = compute_digest(
+            cache.user.as_ref(),
+            &cache.token.access,
+            &cache.token.refresh,
+            &cache.laboratories,
+        );
         persist_cache_in_dir(&remote, dir.path(), &cache).unwrap();
 
         let loaded = load_cache_with_token_refresh_optional_from_dir(&remote, dir.path())

src/cli.rs

@@ -41,7 +41,7 @@ pub enum Commands {
         skip_if_exists: bool,
         #[arg(short = 'p', long)]
         password: Option<String>,
-        #[arg(long)]
+        #[arg(short = 'e', long)]
         exclude: Vec<String>,
         remote_path: String,
         local_path: String,

src/commands/chacl.rs

@@ -1,5 +1,6 @@
 use crate::cache::{create_authenticated_conn, load_cache_with_token_refresh};
-use crate::commands::shared::{find_folder, find_lab_in_cache, parse_remote_path};
+use crate::commands::shared::{find_folder, find_laboratory, parse_remote_path};
+use crate::error::response_error;
 use anyhow::bail;
 
 pub async fn chacl(
@@ -23,7 +24,7 @@ pub async fn chacl(
     let (remote, labname, folder_path) = parse_remote_path(remote_path)?;
     let cache = load_cache_with_token_refresh(&remote).await?;
     let conn = create_authenticated_conn(&remote, &cache)?;
-    let lab = find_lab_in_cache(&cache, &labname)?;
+    let lab = find_laboratory(&conn, Some(&cache), &labname).await?;
     let folder = find_folder(&conn, lab.id, &folder_path, None).await?;
 
     let mut data = serde_json::Map::new();
@@ -45,7 +46,7 @@ pub async fn chacl(
         .await?;
 
     if !resp.status().is_success() {
-        bail!("ACL change failed: {}", resp.status());
+        return Err(response_error("ACL change failed", resp).await);
     }
     Ok(())
 }

src/commands/config.rs

@@ -13,18 +13,18 @@ fn sanitize_config_file(path: &PathBuf) -> Result<(), anyhow::Error> {
     }
     let text = fs::read_to_string(path)?;
     let lines: Vec<&str> = text.lines().collect();
-    if let Some(first) = lines.first() {
-        if first.trim() == path.to_string_lossy() {
-            // remove the first line and write atomically
-            let new_text = if lines.len() > 1 {
-                lines[1..].join("\n")
-            } else {
-                String::new()
-            };
-            let tmp = path.with_extension("tmp");
-            fs::write(&tmp, new_text.as_bytes())?;
-            fs::rename(&tmp, path)?;
-        }
+    if let Some(first) = lines.first()
+        && first.trim() == path.to_string_lossy()
+    {
+        // remove the first line and write atomically
+        let new_text = if lines.len() > 1 {
+            lines[1..].join("\n")
+        } else {
+            String::new()
+        };
+        let tmp = path.with_extension("tmp");
+        fs::write(&tmp, new_text.as_bytes())?;
+        fs::rename(&tmp, path)?;
     }
     Ok(())
 }
@@ -49,9 +49,10 @@ pub fn get_remote_url(remote: &str) -> Result<Option<String>, anyhow::Error> {
 }
 
 pub fn config_create(remote: &str, url: &str) -> Result<(), anyhow::Error> {
-    if !validate_url(url) {
+    let Some(url) = normalize_url(url) else {
         bail!("Malformed URL");
-    }
+    };
+    let url = url.as_str();
     let path = config_path();
     sanitize_config_file(&path)?;
     let path_str = path.to_string_lossy().to_string();
@@ -78,9 +79,10 @@ pub fn config_create(remote: &str, url: &str) -> Result<(), anyhow::Error> {
 }
 
 pub fn config_update(remote: &str, url: &str) -> Result<(), anyhow::Error> {
-    if !validate_url(url) {
+    let Some(url) = normalize_url(url) else {
         bail!("Malformed URL");
-    }
+    };
+    let url = url.as_str();
     let path = config_path();
     sanitize_config_file(&path)?;
     let path_str = path.to_string_lossy().to_string();
@@ -145,6 +147,54 @@ pub fn config_delete(remote: &str) -> Result<(), anyhow::Error> {
     Ok(())
 }
 
-fn validate_url(url: &str) -> bool {
-    validators::url::Url::parse(url).is_ok()
+/// Check a remote URL and put it in the one form every client agrees on.
+///
+/// A bare hostname is accepted, so a development server on `localhost` is as acceptable
+/// as a deployment behind a domain name. The trailing slash goes because the URL is
+/// joined with a path that brings its own.
+fn normalize_url(url: &str) -> Option<String> {
+    let parsed = reqwest::Url::parse(url).ok()?;
+    if !matches!(parsed.scheme(), "http" | "https") {
+        return None;
+    }
+    parsed.host_str()?;
+    Some(url.trim_end_matches('/').to_string())
+}
+
+#[cfg(test)]
+mod url_tests {
+    use super::normalize_url;
+
+    /// Both clients share config.ini, so they have to agree on what a remote URL is.
+    #[test]
+    fn trailing_slash_is_dropped() {
+        assert_eq!(
+            normalize_url("http://127.0.0.1:8000/api/").as_deref(),
+            Some("http://127.0.0.1:8000/api")
+        );
+        assert_eq!(
+            normalize_url("https://neurodata.riken.jp/api/").as_deref(),
+            Some("https://neurodata.riken.jp/api")
+        );
+    }
+
+    #[test]
+    fn bare_hostname_is_accepted() {
+        assert_eq!(
+            normalize_url("http://localhost:8000/api").as_deref(),
+            Some("http://localhost:8000/api")
+        );
+    }
+
+    #[test]
+    fn only_http_schemes_are_accepted() {
+        for url in [
+            "ftp://x.example.com/",
+            "file:///etc/passwd",
+            "not-a-url",
+            "http://",
+        ] {
+            assert_eq!(normalize_url(url), None, "{url} should be rejected");
+        }
+    }
 }

src/commands/cp.rs

@@ -1,8 +1,8 @@
 use crate::cache::{create_authenticated_conn, load_cache_with_token_refresh};
 use crate::commands::shared::{
-    find_file_by_name, find_folder, find_lab_in_cache, find_subfolder_by_name, nfc,
-    parse_remote_path,
+    find_file_by_name, find_folder, find_laboratory, find_subfolder_by_name, nfc, parse_remote_path,
 };
+use crate::error::response_error;
 use anyhow::bail;
 
 pub async fn cp(src_path: &str, dest_path: &str, recursive: bool) -> Result<(), anyhow::Error> {
@@ -19,7 +19,7 @@ pub async fn cp(src_path: &str, dest_path: &str, recursive: bool) -> Result<(),
 
     let cache = load_cache_with_token_refresh(&s_remote).await?;
     let conn = create_authenticated_conn(&s_remote, &cache)?;
-    let lab = find_lab_in_cache(&cache, &s_lab)?;
+    let lab = find_laboratory(&conn, Some(&cache), &s_lab).await?;
     let lab_id = lab.id;
 
     // Split source path into parent directory and target name
@@ -62,7 +62,7 @@ pub async fn cp(src_path: &str, dest_path: &str, recursive: bool) -> Result<(),
             .post_json(&format!("v3/files/{}/copy/", src_file_id), &body)
             .await?;
         if !resp.status().is_success() {
-            bail!("Copy failed: {}", resp.status());
+            return Err(response_error("Copy failed", resp).await);
         }
         return Ok(());
     }
@@ -102,7 +102,7 @@ pub async fn cp(src_path: &str, dest_path: &str, recursive: bool) -> Result<(),
         .post_json(&format!("v3/folders/{}/copy/", src_folder_id), &body)
         .await?;
     if !resp.status().is_success() {
-        bail!("Copy failed: {}", resp.status());
+        return Err(response_error("Copy failed", resp).await);
     }
     Ok(())
 }

src/commands/download.rs

@@ -27,7 +27,7 @@ pub async fn download(
     }
 
     // Detect DOI path: "remote:10.xxxx/prefix.ID[/optional/sub/path]"
-    if is_doi(remote_path.splitn(2, ':').nth(1).unwrap_or("")) {
+    if is_doi(remote_path.split_once(':').map(|x| x.1).unwrap_or("")) {
         let (remote, doi, subpath) = parse_doi_remote_path(remote_path)?;
         let (raw_conn, _cache) = create_readonly_conn(&remote).await?;
         let (doi_folder, lab) = find_folder_by_doi(&raw_conn, &doi, password).await?;
@@ -84,15 +84,13 @@ pub async fn download(
                         continue;
                     }
                     let dest = local_real.join(&file.name);
-                    if skip_if_exists {
-                        if dest.exists() {
-                            if let Ok(meta) = std::fs::metadata(&dest) {
-                                if meta.len() == file.size {
-                                    println!("{}", dest.display());
-                                    continue;
-                                }
-                            }
-                        }
+                    if skip_if_exists
+                        && dest.exists()
+                        && let Ok(meta) = std::fs::metadata(&dest)
+                        && meta.len() == file.size
+                    {
+                        println!("{}", dest.display());
+                        continue;
                     }
                     let url = make_absolute_url(&conn, &file.download_url);
                     conn.download_file_limited(&url, &dest.to_string_lossy(), &limiter)
@@ -102,30 +100,23 @@ pub async fn download(
                 return Ok(());
             }
 
-            spawn_download_folder_task(
-                &mut folder_tasks,
-                conn.clone(),
-                limiter.clone(),
-                lab_name.clone(),
-                excludes.clone(),
-                folder.id.clone(),
-                top_local,
-                password_owned.clone(),
-                skip_if_exists,
-            );
-
-            drive_download_tasks(
-                &mut folder_tasks,
-                &mut download_tasks,
-                &mut errors,
-                conn.clone(),
+            let session = DownloadSession {
+                conn: conn.clone(),
                 limiter,
                 lab_name,
                 excludes,
-                password_owned,
+                password: password_owned,
                 skip_if_exists,
-            )
-            .await;
+            };
+            spawn_download_folder_task(
+                &mut folder_tasks,
+                session.clone(),
+                folder.id.clone(),
+                top_local,
+            );
+
+            drive_download_tasks(&mut folder_tasks, &mut download_tasks, &mut errors, session)
+                .await;
 
             if !errors.is_empty() {
                 bail!(errors.join("\n"));
@@ -146,15 +137,13 @@ pub async fn download(
                 return Ok(());
             }
             let dest = local_real.join(&file.name);
-            if skip_if_exists {
-                if dest.exists() {
-                    if let Ok(meta) = std::fs::metadata(&dest) {
-                        if meta.len() == file.size {
-                            println!("{}", dest.display());
-                            return Ok(());
-                        }
-                    }
-                }
+            if skip_if_exists
+                && dest.exists()
+                && let Ok(meta) = std::fs::metadata(&dest)
+                && meta.len() == file.size
+            {
+                println!("{}", dest.display());
+                return Ok(());
             }
             let url = make_absolute_url(&conn, &file.download_url);
             conn.download_file_limited(&url, &dest.to_string_lossy(), &limiter)
@@ -177,30 +166,23 @@ pub async fn download(
             let lab_name = Arc::new(lab.name.clone());
             let password_owned = password.map(str::to_string);
 
-            spawn_download_folder_task(
-                &mut folder_tasks,
-                conn.clone(),
-                limiter.clone(),
-                lab_name.clone(),
-                excludes.clone(),
-                sub.id.clone(),
-                top_local,
-                password_owned.clone(),
-                skip_if_exists,
-            );
-
-            drive_download_tasks(
-                &mut folder_tasks,
-                &mut download_tasks,
-                &mut errors,
-                conn.clone(),
+            let session = DownloadSession {
+                conn: conn.clone(),
                 limiter,
                 lab_name,
                 excludes,
-                password_owned,
+                password: password_owned,
                 skip_if_exists,
-            )
-            .await;
+            };
+            spawn_download_folder_task(
+                &mut folder_tasks,
+                session.clone(),
+                sub.id.clone(),
+                top_local,
+            );
+
+            drive_download_tasks(&mut folder_tasks, &mut download_tasks, &mut errors, session)
+                .await;
 
             if !errors.is_empty() {
                 bail!(errors.join("\n"));
@@ -242,15 +224,13 @@ pub async fn download(
         }
         // Python always places the downloaded file inside the local directory.
         let dest = local_real.join(&file.name);
-        if skip_if_exists {
-            if dest.exists() {
-                if let Ok(meta) = std::fs::metadata(&dest) {
-                    if meta.len() == file.size {
-                        println!("{}", dest.display());
-                        return Ok(());
-                    }
-                }
-            }
+        if skip_if_exists
+            && dest.exists()
+            && let Ok(meta) = std::fs::metadata(&dest)
+            && meta.len() == file.size
+        {
+            println!("{}", dest.display());
+            return Ok(());
         }
         let url = make_absolute_url(&conn, &file.download_url);
         conn.download_file_limited(&url, &dest.to_string_lossy(), &limiter)
@@ -277,30 +257,22 @@ pub async fn download(
         let lab_name = Arc::new(lab.name.clone());
         let password = password.map(str::to_string);
 
-        spawn_download_folder_task(
-            &mut folder_tasks,
-            conn.clone(),
-            limiter.clone(),
-            lab_name.clone(),
-            excludes.clone(),
-            sub.id.clone(),
-            top_local,
-            password.clone(),
-            skip_if_exists,
-        );
-
-        drive_download_tasks(
-            &mut folder_tasks,
-            &mut download_tasks,
-            &mut errors,
-            conn.clone(),
+        let session = DownloadSession {
+            conn: conn.clone(),
             limiter,
             lab_name,
             excludes,
             password,
             skip_if_exists,
-        )
-        .await;
+        };
+        spawn_download_folder_task(
+            &mut folder_tasks,
+            session.clone(),
+            sub.id.clone(),
+            top_local,
+        );
+
+        drive_download_tasks(&mut folder_tasks, &mut download_tasks, &mut errors, session).await;
 
         if !errors.is_empty() {
             bail!(errors.join("\n"));
@@ -353,30 +325,26 @@ struct DownloadJob {
     dest_path: PathBuf,
 }
 
-fn spawn_download_folder_task(
-    folder_tasks: &mut JoinSet<Result<DownloadFolderTaskResult, anyhow::Error>>,
+/// What every folder of one recursive download shares: the connection and its request
+/// budget, the laboratory the paths are named against, what to leave out, the password
+/// for locked folders, and whether files already on disk may be left alone.
+#[derive(Clone)]
+struct DownloadSession {
     conn: Arc<MDRSConnection>,
     limiter: ApiRequestLimiter,
     lab_name: Arc<String>,
     excludes: Arc<Vec<String>>,
-    folder_id: String,
-    local_dir: PathBuf,
     password: Option<String>,
     skip_if_exists: bool,
+}
+
+fn spawn_download_folder_task(
+    folder_tasks: &mut JoinSet<Result<DownloadFolderTaskResult, anyhow::Error>>,
+    session: DownloadSession,
+    folder_id: String,
+    local_dir: PathBuf,
 ) {
-    folder_tasks.spawn(async move {
-        process_download_folder(
-            conn,
-            limiter,
-            lab_name,
-            excludes,
-            folder_id,
-            local_dir,
-            password,
-            skip_if_exists,
-        )
-        .await
-    });
+    folder_tasks.spawn(async move { process_download_folder(session, folder_id, local_dir).await });
 }
 
 fn spawn_download_task(
@@ -396,9 +364,8 @@ fn spawn_download_task(
                 Ok(())
             }
             Err(err) => {
-                if job.dest_path.is_file() {
-                    let _ = std::fs::remove_file(&job.dest_path);
-                }
+                // Nothing to clear up: a failed transfer writes only to its own scratch
+                // file, and removes that itself.
                 Err(anyhow!(
                     "Failed to download {}: {}",
                     job.dest_path.display(),
@@ -410,15 +377,18 @@ fn spawn_download_task(
 }
 
 async fn process_download_folder(
-    conn: Arc<MDRSConnection>,
-    limiter: ApiRequestLimiter,
-    lab_name: Arc<String>,
-    excludes: Arc<Vec<String>>,
+    session: DownloadSession,
     folder_id: String,
     local_dir: PathBuf,
-    password: Option<String>,
-    skip_if_exists: bool,
 ) -> Result<DownloadFolderTaskResult, anyhow::Error> {
+    let DownloadSession {
+        conn,
+        limiter,
+        lab_name,
+        excludes,
+        password,
+        skip_if_exists,
+    } = session;
     let folder = conn.retrieve_folder_limited(&folder_id, &limiter).await?;
 
     if is_excluded(excludes.as_slice(), lab_name.as_str(), &folder.path, None) {
@@ -443,13 +413,13 @@ async fn process_download_folder(
             continue;
         }
         let dest_path = local_dir.join(&file.name);
-        if skip_if_exists && dest_path.exists() {
-            if let Ok(meta) = std::fs::metadata(&dest_path) {
-                if meta.len() == file.size {
-                    println!("{}", dest_path.display());
-                    continue;
-                }
-            }
+        if skip_if_exists
+            && dest_path.exists()
+            && let Ok(meta) = std::fs::metadata(&dest_path)
+            && meta.len() == file.size
+        {
+            println!("{}", dest_path.display());
+            continue;
         }
         download_jobs.push(DownloadJob {
             url: make_absolute_url(&conn, &file.download_url),
@@ -500,12 +470,7 @@ async fn drive_download_tasks(
     folder_tasks: &mut JoinSet<Result<DownloadFolderTaskResult, anyhow::Error>>,
     download_tasks: &mut JoinSet<Result<(), anyhow::Error>>,
     errors: &mut Vec<String>,
-    conn: Arc<MDRSConnection>,
-    limiter: ApiRequestLimiter,
-    lab_name: Arc<String>,
-    excludes: Arc<Vec<String>>,
-    password: Option<String>,
-    skip_if_exists: bool,
+    session: DownloadSession,
 ) {
     loop {
         match (folder_tasks.is_empty(), download_tasks.is_empty()) {
@@ -517,20 +482,15 @@ async fn drive_download_tasks(
                         folder_tasks,
                         download_tasks,
                         errors,
-                        conn.clone(),
-                        limiter.clone(),
-                        lab_name.clone(),
-                        excludes.clone(),
-                        password.clone(),
-                        skip_if_exists,
+                        &session,
                     );
                 }
             }
             (true, false) => {
-                if let Some(result) = download_tasks.join_next().await {
-                    if let Err(err) = flatten_join_result(result) {
-                        errors.push(err.to_string());
-                    }
+                if let Some(result) = download_tasks.join_next().await
+                    && let Err(err) = flatten_join_result(result)
+                {
+                    errors.push(err.to_string());
                 }
             }
             (false, false) => {
@@ -542,21 +502,15 @@ async fn drive_download_tasks(
                                 folder_tasks,
                                 download_tasks,
                                 errors,
-                                conn.clone(),
-                                limiter.clone(),
-                                lab_name.clone(),
-                                excludes.clone(),
-                                password.clone(),
-                                skip_if_exists,
+                                &session,
                             );
                         }
                     }
                     result = download_tasks.join_next() => {
-                        if let Some(result) = result {
-                            if let Err(err) = flatten_join_result(result) {
+                        if let Some(result) = result
+                            && let Err(err) = flatten_join_result(result) {
                                 errors.push(err.to_string());
                             }
-                        }
                     }
                 }
             }
@@ -569,30 +523,20 @@ fn handle_download_folder_result(
     folder_tasks: &mut JoinSet<Result<DownloadFolderTaskResult, anyhow::Error>>,
     download_tasks: &mut JoinSet<Result<(), anyhow::Error>>,
     errors: &mut Vec<String>,
-    conn: Arc<MDRSConnection>,
-    limiter: ApiRequestLimiter,
-    lab_name: Arc<String>,
-    excludes: Arc<Vec<String>>,
-    password: Option<String>,
-    skip_if_exists: bool,
+    session: &DownloadSession,
 ) {
     match flatten_join_result(result) {
         Ok(task_result) => {
             for (folder_id, local_dir) in task_result.child_folders {
-                spawn_download_folder_task(
-                    folder_tasks,
-                    conn.clone(),
-                    limiter.clone(),
-                    lab_name.clone(),
-                    excludes.clone(),
-                    folder_id,
-                    local_dir,
-                    password.clone(),
-                    skip_if_exists,
-                );
+                spawn_download_folder_task(folder_tasks, session.clone(), folder_id, local_dir);
             }
             for job in task_result.download_jobs {
-                spawn_download_task(download_tasks, conn.clone(), limiter.clone(), job);
+                spawn_download_task(
+                    download_tasks,
+                    session.conn.clone(),
+                    session.limiter.clone(),
+                    job,
+                );
             }
         }
         Err(err) => errors.push(err.to_string()),

src/commands/file_metadata.rs

@@ -1,10 +1,11 @@
 use crate::cache::create_readonly_conn;
 use crate::commands::shared::{find_file_by_name, resolve_remote_file};
+use crate::error::response_error;
 use anyhow::anyhow;
 
 pub async fn file_metadata(remote_path: &str, password: Option<&str>) -> Result<(), anyhow::Error> {
     let remote = remote_path
-        .splitn(2, ':')
+        .split(':')
         .next()
         .ok_or_else(|| anyhow!("Invalid remote path"))?;
     let (conn, cache) = create_readonly_conn(remote).await?;
@@ -17,6 +18,9 @@ pub async fn file_metadata(remote_path: &str, password: Option<&str>) -> Result<
         .ok_or_else(|| anyhow!("File `{}` not found.", basename))?;
 
     let resp = conn.get(&format!("v3/files/{}/metadata/", file.id)).await?;
+    if !resp.status().is_success() {
+        return Err(response_error("Failed to get file metadata", resp).await);
+    }
     let json: serde_json::Value = resp.json().await?;
     println!("{}", serde_json::to_string(&json)?);
     Ok(())

src/commands/ls.rs

@@ -1,12 +1,19 @@
-use crate::cache::create_readonly_conn;
+use crate::cache::{Cache, create_readonly_conn};
 use crate::commands::shared::{fmt_datetime, resolve_remote_folder};
 use crate::connection::MDRSConnection;
 use crate::models::file::File;
 use crate::models::folder::{FolderDetail, FolderSimple};
 use serde_json::{Value, json};
+use std::collections::HashMap;
 use std::future::Future;
 use std::pin::Pin;
 
+/// Laboratory names by id, for the JSON output's per-folder `laboratory` field.
+type LaboratoryNames = HashMap<u32, String>;
+
+/// Shown for a folder whose laboratory the client cannot name, matching the Python client.
+const UNKNOWN_LABORATORY: &str = "(invalid)";
+
 pub async fn ls(
     remote_path: &str,
     password: Option<&str>,
@@ -15,7 +22,7 @@ pub async fn ls(
     is_quiet: bool,
 ) -> Result<(), anyhow::Error> {
     let remote = remote_path
-        .splitn(2, ':')
+        .split(':')
         .next()
         .ok_or_else(|| anyhow::anyhow!("Invalid remote path"))?;
     let (conn, cache) = create_readonly_conn(remote).await?;
@@ -24,10 +31,11 @@ pub async fn ls(
     let labname = lab.name;
 
     if is_json {
+        let names = laboratory_names(&conn, cache.as_ref()).await;
         let output = if is_recursive {
-            build_folder_json_recursive(&conn, folder, &labname).await?
+            build_folder_json_recursive(&conn, folder, &names, password).await?
         } else {
-            build_folder_json_flat(&conn, &folder, &labname).await?
+            build_folder_json_flat(&conn, &folder, &names).await?
         };
         println!("{}", serde_json::to_string(&output)?);
     } else if is_recursive {
@@ -214,7 +222,13 @@ fn file_to_json(f: &File, base_url: &str) -> Value {
     let download_url = if f.download_url.starts_with("http") {
         f.download_url.clone()
     } else {
-        format!("{}{}", base_url.trim_end_matches('/'), f.download_url)
+        // The API answers with a relative path and no leading separator, so supply one
+        // rather than running the two together.
+        format!(
+            "{}/{}",
+            base_url.trim_end_matches('/'),
+            f.download_url.trim_start_matches('/')
+        )
     };
     json!({
         "id": f.id,
@@ -229,7 +243,7 @@ fn file_to_json(f: &File, base_url: &str) -> Value {
     })
 }
 
-fn folder_simple_to_json(sf: &FolderSimple) -> Value {
+fn folder_simple_to_json(sf: &FolderSimple, names: &LaboratoryNames) -> Value {
     json!({
         "id": sf.id,
         "pid": sf.pid,
@@ -237,26 +251,58 @@ fn folder_simple_to_json(sf: &FolderSimple) -> Value {
         "access_level": sf.access_level_name(),
         "lock": sf.lock,
         "size": sf.size,
-        "laboratory_id": sf.laboratory_id,
+        "laboratory": laboratory_name(names, sf.laboratory_id),
         "description": sf.description,
         "created_at": sf.created_at,
         "updated_at": sf.updated_at,
     })
 }
 
+/// Name the laboratory a folder belongs to, so a listing does not hand out an id the
+/// reader has no way to resolve.
+fn laboratory_name(names: &LaboratoryNames, id: u32) -> String {
+    names
+        .get(&id)
+        .cloned()
+        .unwrap_or_else(|| UNKNOWN_LABORATORY.to_string())
+}
+
+/// Collect laboratory names, preferring what the login cache already holds so a listing
+/// does not pay for a request it does not need.
+async fn laboratory_names(conn: &MDRSConnection, cache: Option<&Cache>) -> LaboratoryNames {
+    if let Some(cache) = cache.filter(|c| !c.laboratories.items.is_empty()) {
+        return cache
+            .laboratories
+            .items
+            .iter()
+            .map(|lab| (lab.id, lab.name.clone()))
+            .collect();
+    }
+    match conn.list_laboratories().await {
+        Ok(labs) => labs
+            .items
+            .into_iter()
+            .map(|lab| (lab.id, lab.name))
+            .collect(),
+        Err(_) => LaboratoryNames::new(),
+    }
+}
+
 /// Build JSON for the top-level folder without recursing into sub-folders.
 async fn build_folder_json_flat(
     conn: &MDRSConnection,
     folder: &FolderDetail,
-    labname: &str,
+    names: &LaboratoryNames,
 ) -> Result<Value, anyhow::Error> {
     let metadata = get_folder_metadata(conn, &folder.id).await?;
-    let files = conn.list_all_files(&folder.id).await?;
+    let mut files = conn.list_all_files(&folder.id).await?;
+    files.sort_by(|a, b| a.name.cmp(&b.name));
     let files_json: Vec<Value> = files.iter().map(|f| file_to_json(f, &conn.url)).collect();
-    let sub_folders_json: Vec<Value> = folder
-        .sub_folders
+    let mut sub_folders = folder.sub_folders.clone();
+    sub_folders.sort_by(|a, b| a.name.cmp(&b.name));
+    let sub_folders_json: Vec<Value> = sub_folders
         .iter()
-        .map(folder_simple_to_json)
+        .map(|sf| folder_simple_to_json(sf, names))
         .collect();
 
     Ok(json!({
@@ -266,7 +312,7 @@ async fn build_folder_json_flat(
         "size": folder.size,
         "access_level": folder.access_level_name(),
         "lock": folder.lock,
-        "laboratory": labname,
+        "laboratory": laboratory_name(names, folder.laboratory_id),
         "description": folder.description,
         "created_at": folder.created_at,
         "updated_at": folder.updated_at,
@@ -280,17 +326,36 @@ async fn build_folder_json_flat(
 fn build_folder_json_recursive<'a>(
     conn: &'a MDRSConnection,
     folder: FolderDetail,
-    labname: &'a str,
+    names: &'a LaboratoryNames,
+    password: Option<&'a str>,
 ) -> Pin<Box<dyn Future<Output = Result<Value, anyhow::Error>> + 'a>> {
     Box::pin(async move {
         let metadata = get_folder_metadata(conn, &folder.id).await?;
-        let files = conn.list_all_files(&folder.id).await?;
+        let mut files = conn.list_all_files(&folder.id).await?;
+        files.sort_by(|a, b| a.name.cmp(&b.name));
         let files_json: Vec<Value> = files.iter().map(|f| file_to_json(f, &conn.url)).collect();
 
+        let mut sub_folders = folder.sub_folders.clone();
+        sub_folders.sort_by(|a, b| a.name.cmp(&b.name));
         let mut sub_folders_json = Vec::new();
-        for sf in &folder.sub_folders {
+        for sf in &sub_folders {
+            // A folder the caller cannot unlock is left out rather than ending the whole
+            // listing: a tree usually holds a locked folder or two, and the rest of it is
+            // still what the user asked to see. Anything else is reported, because a
+            // listing that quietly drops a branch cannot be told from one where the
+            // branch is empty, and this output is read by programs.
+            if sf.lock {
+                match password {
+                    None => continue,
+                    Some(pw) => {
+                        if conn.folder_auth(&sf.id, pw).await.is_err() {
+                            continue;
+                        }
+                    }
+                }
+            }
             let sf_detail = conn.retrieve_folder(&sf.id).await?;
-            let sf_json = build_folder_json_recursive(conn, sf_detail, labname).await?;
+            let sf_json = build_folder_json_recursive(conn, sf_detail, names, password).await?;
             sub_folders_json.push(sf_json);
         }
 
@@ -301,7 +366,7 @@ fn build_folder_json_recursive<'a>(
             "size": folder.size,
             "access_level": folder.access_level_name(),
             "lock": folder.lock,
-            "laboratory": labname,
+            "laboratory": laboratory_name(names, folder.laboratory_id),
             "description": folder.description,
             "created_at": folder.created_at,
             "updated_at": folder.updated_at,

src/commands/metadata.rs

@@ -1,9 +1,10 @@
 use crate::cache::create_readonly_conn;
 use crate::commands::shared::resolve_remote_folder;
+use crate::error::response_error;
 
 pub async fn metadata(remote_path: &str, password: Option<&str>) -> Result<(), anyhow::Error> {
     let remote = remote_path
-        .splitn(2, ':')
+        .split(':')
         .next()
         .ok_or_else(|| anyhow::anyhow!("Invalid remote path"))?;
     let (conn, cache) = create_readonly_conn(remote).await?;
@@ -13,6 +14,9 @@ pub async fn metadata(remote_path: &str, password: Option<&str>) -> Result<(), a
     let resp = conn
         .get(&format!("v3/folders/{}/metadata/", folder.id))
         .await?;
+    if !resp.status().is_success() {
+        return Err(response_error("Failed to get folder metadata", resp).await);
+    }
     let json: serde_json::Value = resp.json().await?;
     println!("{}", serde_json::to_string(&json)?);
     Ok(())

src/commands/mkdir.rs

@@ -1,8 +1,8 @@
 use crate::cache::{create_authenticated_conn, load_cache_with_token_refresh};
 use crate::commands::shared::{
-    find_file_by_name, find_folder, find_lab_in_cache, find_subfolder_by_name, nfc,
-    parse_remote_path,
+    find_file_by_name, find_folder, find_laboratory, find_subfolder_by_name, nfc, parse_remote_path,
 };
+use crate::error::response_error;
 use anyhow::{anyhow, bail};
 
 pub async fn mkdir(remote_path: &str) -> Result<(), anyhow::Error> {
@@ -25,7 +25,7 @@ pub async fn mkdir(remote_path: &str) -> Result<(), anyhow::Error> {
 
     let cache = load_cache_with_token_refresh(&remote).await?;
     let conn = create_authenticated_conn(&remote, &cache)?;
-    let lab = find_lab_in_cache(&cache, &labname)?;
+    let lab = find_laboratory(&conn, Some(&cache), &labname).await?;
     let parent_folder = find_folder(&conn, lab.id, parent_path, None).await?;
 
     // Check for name conflict in sub-folders or files
@@ -40,7 +40,7 @@ pub async fn mkdir(remote_path: &str) -> Result<(), anyhow::Error> {
         .create_folder(&parent_folder.id, &nfc(new_folder_name))
         .await?;
     if !resp.status().is_success() {
-        bail!("Failed to create folder: {}", resp.status());
+        return Err(response_error("Failed to create folder", resp).await);
     }
     Ok(())
 }

src/commands/mv.rs

@@ -1,8 +1,8 @@
 use crate::cache::{create_authenticated_conn, load_cache_with_token_refresh};
 use crate::commands::shared::{
-    find_file_by_name, find_folder, find_lab_in_cache, find_subfolder_by_name, nfc,
-    parse_remote_path,
+    find_file_by_name, find_folder, find_laboratory, find_subfolder_by_name, nfc, parse_remote_path,
 };
+use crate::error::response_error;
 use anyhow::bail;
 
 pub async fn mv(src_path: &str, dest_path: &str) -> Result<(), anyhow::Error> {
@@ -19,7 +19,7 @@ pub async fn mv(src_path: &str, dest_path: &str) -> Result<(), anyhow::Error> {
 
     let cache = load_cache_with_token_refresh(&s_remote).await?;
     let conn = create_authenticated_conn(&s_remote, &cache)?;
-    let lab = find_lab_in_cache(&cache, &s_lab)?;
+    let lab = find_laboratory(&conn, Some(&cache), &s_lab).await?;
     let lab_id = lab.id;
 
     // Split source path into parent directory and target name
@@ -62,7 +62,7 @@ pub async fn mv(src_path: &str, dest_path: &str) -> Result<(), anyhow::Error> {
             .post_json(&format!("v3/files/{}/move/", src_file_id), &body)
             .await?;
         if !resp.status().is_success() {
-            bail!("Move failed: {}", resp.status());
+            return Err(response_error("Move failed", resp).await);
         }
         return Ok(());
     }
@@ -99,7 +99,7 @@ pub async fn mv(src_path: &str, dest_path: &str) -> Result<(), anyhow::Error> {
         .post_json(&format!("v3/folders/{}/move/", src_folder_id), &body)
         .await?;
     if !resp.status().is_success() {
-        bail!("Move failed: {}", resp.status());
+        return Err(response_error("Move failed", resp).await);
     }
     Ok(())
 }

src/commands/rm.rs

@@ -1,7 +1,8 @@
 use crate::cache::{create_authenticated_conn, load_cache_with_token_refresh};
 use crate::commands::shared::{
-    find_file_by_name, find_folder, find_lab_in_cache, find_subfolder_by_name, parse_remote_path,
+    find_file_by_name, find_folder, find_laboratory, find_subfolder_by_name, parse_remote_path,
 };
+use crate::error::response_error;
 use anyhow::{anyhow, bail};
 
 pub async fn rm(remote_path: &str, recursive: bool) -> Result<(), anyhow::Error> {
@@ -22,7 +23,7 @@ pub async fn rm(remote_path: &str, recursive: bool) -> Result<(), anyhow::Error>
 
     let cache = load_cache_with_token_refresh(&remote).await?;
     let conn = create_authenticated_conn(&remote, &cache)?;
-    let lab = find_lab_in_cache(&cache, &labname)?;
+    let lab = find_laboratory(&conn, Some(&cache), &labname).await?;
     let parent_folder = find_folder(&conn, lab.id, parent_path, None).await?;
 
     // Check if target is a file
@@ -30,7 +31,7 @@ pub async fn rm(remote_path: &str, recursive: bool) -> Result<(), anyhow::Error>
     if let Some(file) = find_file_by_name(&files, target_name) {
         let resp = conn.delete(&format!("v3/files/{}/", file.id)).await?;
         if !resp.status().is_success() {
-            bail!("Failed to delete file: {}", resp.status());
+            return Err(response_error("Failed to delete file", resp).await);
         }
         return Ok(());
     }
@@ -47,7 +48,7 @@ pub async fn rm(remote_path: &str, recursive: bool) -> Result<(), anyhow::Error>
             )
             .await?;
         if !resp.status().is_success() {
-            bail!("Failed to delete folder: {}", resp.status());
+            return Err(response_error("Failed to delete folder", resp).await);
         }
         return Ok(());
     }

src/commands/selfupdate.rs

@@ -48,6 +48,25 @@ fn is_newer(current: &str, latest: &str) -> bool {
     false
 }
 
+/// Read the digest out of a `sha256sum` line: the hex digest, then the file it covers.
+fn parse_sha256_line(text: &str) -> Option<String> {
+    let digest = text.split_whitespace().next()?.to_ascii_lowercase();
+    let is_hex = digest.len() == 64 && digest.chars().all(|c| c.is_ascii_hexdigit());
+    is_hex.then_some(digest)
+}
+
+/// Hex SHA-256 of a slice, in the form `sha256sum` prints.
+fn sha256_hex(bytes: &[u8]) -> String {
+    use sha2::{Digest, Sha256};
+    let mut hasher = Sha256::new();
+    hasher.update(bytes);
+    hasher
+        .finalize()
+        .iter()
+        .map(|b| format!("{:02x}", b))
+        .collect()
+}
+
 /// Extract the binary named `bin_name` from a `.tar.gz` archive at `archive_path`
 /// and write it to `dest_path`.
 fn extract_from_tar_gz(
@@ -138,10 +157,11 @@ pub async fn selfupdate(yes: bool) -> anyhow::Result<()> {
     println!("New version available: {latest_version}");
 
     // Find the asset matching the current build target.
+    // The checksum asset carries the target in its name too, so say which one is wanted.
     let asset = release
         .assets
         .iter()
-        .find(|a| a.name.contains(BUILD_TARGET))
+        .find(|a| a.name.contains(BUILD_TARGET) && !a.name.ends_with(".sha256"))
         .ok_or_else(|| {
             let names: Vec<&str> = release.assets.iter().map(|a| a.name.as_str()).collect();
             anyhow!(
@@ -186,6 +206,54 @@ pub async fn selfupdate(yes: bool) -> anyhow::Result<()> {
     }
 
     let bytes = download_resp.bytes().await?;
+
+    // This binary is about to replace the one the user is running, so what arrived has to
+    // be what the release says it is. Transport already proves who served it; the digest
+    // proves the archive was not swapped or truncated on the way.
+    match release
+        .assets
+        .iter()
+        .find(|a| a.name == format!("{}.sha256", asset.name))
+    {
+        Some(checksum_asset) => {
+            let mut checksum_req = client
+                .get(&checksum_asset.browser_download_url)
+                .header(USER_AGENT, format!("mdrs/{current_version}"));
+            if let Ok(token) = env::var("GITEA_TOKEN") {
+                checksum_req = checksum_req.header(AUTHORIZATION, format!("Bearer {token}"));
+            }
+            let checksum_resp = checksum_req.send().await?;
+            if !checksum_resp.status().is_success() {
+                bail!(
+                    "Failed to download checksum: HTTP {}",
+                    checksum_resp.status()
+                );
+            }
+            let expected = parse_sha256_line(&checksum_resp.text().await?)
+                .ok_or_else(|| anyhow!("Checksum asset '{}' is malformed", checksum_asset.name))?;
+            let actual = sha256_hex(&bytes);
+            if actual != expected {
+                bail!(
+                    "Checksum mismatch for '{}': expected {}, got {}. The download was not what \
+                     the release publishes, so this binary has not been replaced.",
+                    asset.name,
+                    expected,
+                    actual
+                );
+            }
+            println!("Checksum verified.");
+        }
+        None => {
+            // Releases built before the workflow published checksums have none to check
+            // against. Say so rather than letting the absence pass for a verified download.
+            eprintln!(
+                "Warning: release {latest_version} publishes no checksum for '{}', \
+                 so the download could not be verified.",
+                asset.name
+            );
+        }
+    }
+
     std::fs::write(&archive_path, &bytes)?;
 
     // Extract the binary from the archive.
@@ -216,3 +284,35 @@ pub async fn selfupdate(yes: bool) -> anyhow::Result<()> {
     println!("Successfully updated to version {latest_version}.");
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn a_sha256sum_line_yields_its_digest() {
+        let digest = "a".repeat(64);
+        assert_eq!(
+            parse_sha256_line(&format!(
+                "{digest}  mdrs-2.0.1-x86_64-unknown-linux-musl.tar.gz\n"
+            )),
+            Some(digest)
+        );
+    }
+
+    #[test]
+    fn a_line_that_is_not_a_digest_is_refused() {
+        for text in ["", "not-a-digest  file", "abc123  file"] {
+            assert_eq!(parse_sha256_line(text), None, "{text:?} should be refused");
+        }
+    }
+
+    #[test]
+    fn the_digest_matches_what_sha256sum_prints() {
+        // Verified against `printf mdrs | sha256sum`.
+        assert_eq!(
+            sha256_hex(b"mdrs"),
+            "bd9845248df877e411ec8bef10b823bd4c0900a530157eedfdfbfb63ccbde2fa"
+        );
+    }
+}

src/commands/shared.rs

@@ -158,6 +158,10 @@ pub async fn find_folder_by_doi(
 // ---------------------------------------------------------------------------
 
 /// Parse "remote:/labname/path/" into (remote, labname, folder_path).
+///
+/// The path is put in one form before anything is done with it: repeated and trailing
+/// separators go, `.` segments go, and a `..` is refused rather than sent on. The Python
+/// client does the same, and both talk to the same server.
 pub fn parse_remote_path(remote_path: &str) -> Result<(String, String, String), anyhow::Error> {
     let parts: Vec<&str> = remote_path.splitn(2, ':').collect();
     if parts.len() != 2 {
@@ -168,12 +172,22 @@ pub fn parse_remote_path(remote_path: &str) -> Result<(String, String, String),
     if !rest.starts_with('/') {
         bail!("Path must be absolute (start with '/')");
     }
-    let folder_parts: Vec<&str> = rest.trim_start_matches('/').splitn(2, '/').collect();
-    let labname = folder_parts[0].to_string();
-    let path = if folder_parts.len() > 1 && !folder_parts[1].is_empty() {
-        format!("/{}", folder_parts[1].trim_end_matches('/'))
-    } else {
+    let mut segments = Vec::new();
+    for segment in rest.split('/') {
+        match segment {
+            "" | "." => continue,
+            ".." => bail!("Path traversal found."),
+            other => segments.push(other),
+        }
+    }
+    if segments.is_empty() {
+        bail!("Laboratory name is missing from `{}`.", remote_path);
+    }
+    let labname = segments.remove(0).to_string();
+    let path = if segments.is_empty() {
         "/".to_string()
+    } else {
+        format!("/{}", segments.join("/"))
     };
     Ok((remote, labname, path))
 }
@@ -202,15 +216,15 @@ pub async fn find_laboratory(
     cache: Option<&Cache>,
     labname: &str,
 ) -> Result<Laboratory, anyhow::Error> {
-    if let Some(cache) = cache {
-        if let Ok(lab) = find_lab_in_cache(cache, labname) {
-            return Ok(Laboratory {
-                id: lab.id,
-                name: lab.name.clone(),
-                pi_name: lab.pi_name.clone(),
-                full_name: lab.full_name.clone(),
-            });
-        }
+    if let Some(cache) = cache
+        && let Ok(lab) = find_lab_in_cache(cache, labname)
+    {
+        return Ok(Laboratory {
+            id: lab.id,
+            name: lab.name.clone(),
+            pi_name: lab.pi_name.clone(),
+            full_name: lab.full_name.clone(),
+        });
     }
 
     conn.list_laboratories()
@@ -338,7 +352,7 @@ pub fn find_subfolder_by_name<'a>(
 /// Format an ISO 8601 timestamp as "YYYY/MM/DD HH:MM:SS".
 pub fn fmt_datetime(iso: &str) -> String {
     let s = iso.trim();
-    let s = if let Some(pos) = s[10..].find(|c: char| c == '+' || c == '-') {
+    let s = if let Some(pos) = s[10..].find(['+', '-']) {
         &s[..10 + pos]
     } else {
         s.trim_end_matches('Z')
@@ -361,7 +375,7 @@ pub async fn resolve_remote_folder(
     remote_path: &str,
     password: Option<&str>,
 ) -> Result<(FolderDetail, Laboratory), anyhow::Error> {
-    let path_component = remote_path.splitn(2, ':').nth(1).unwrap_or("");
+    let path_component = remote_path.split_once(':').map(|x| x.1).unwrap_or("");
     if is_doi(path_component) {
         let (_, doi, subpath) = parse_doi_remote_path(remote_path)?;
         let (doi_folder, lab) = find_folder_by_doi(conn, &doi, password).await?;
@@ -395,7 +409,7 @@ pub async fn resolve_remote_file(
     remote_path: &str,
     password: Option<&str>,
 ) -> Result<(FolderDetail, String), anyhow::Error> {
-    let path_component = remote_path.splitn(2, ':').nth(1).unwrap_or("");
+    let path_component = remote_path.split_once(':').map(|x| x.1).unwrap_or("");
     if is_doi(path_component) {
         let (_, doi, subpath) = parse_doi_remote_path(remote_path)?;
         let (doi_folder, lab) = find_folder_by_doi(conn, &doi, password).await?;
@@ -473,6 +487,53 @@ mod tests {
         server.await.unwrap();
     }
 
+    // ------------------------------------------------------------------
+    // Remote path parsing
+    // ------------------------------------------------------------------
+
+    #[test]
+    fn parse_remote_path_splits_remote_lab_and_path() {
+        let (remote, lab, path) = parse_remote_path("neurodata:/mylab/a/b/").unwrap();
+        assert_eq!(
+            (remote.as_str(), lab.as_str(), path.as_str()),
+            ("neurodata", "mylab", "/a/b")
+        );
+    }
+
+    #[test]
+    fn parse_remote_path_gives_the_lab_root_its_own_form() {
+        let (_, lab, path) = parse_remote_path("neurodata:/mylab").unwrap();
+        assert_eq!((lab.as_str(), path.as_str()), ("mylab", "/"));
+    }
+
+    /// Both clients talk to the same server, so a doubled separator or a `.` segment has
+    /// to reach it as the same path from either one.
+    #[test]
+    fn parse_remote_path_collapses_redundant_segments() {
+        let (_, lab, path) = parse_remote_path("neurodata://mylab//a/./b//").unwrap();
+        assert_eq!((lab.as_str(), path.as_str()), ("mylab", "/a/b"));
+    }
+
+    #[test]
+    fn parse_remote_path_refuses_a_parent_segment() {
+        for path in [
+            "neurodata:/mylab/../other",
+            "neurodata:/mylab/a/..",
+            "neurodata:/../mylab",
+        ] {
+            let err = parse_remote_path(path).unwrap_err();
+            assert!(
+                err.to_string().contains("Path traversal found."),
+                "{path} should be refused"
+            );
+        }
+    }
+
+    #[test]
+    fn parse_remote_path_refuses_a_path_without_a_laboratory() {
+        assert!(parse_remote_path("neurodata:/").is_err());
+    }
+
     // ------------------------------------------------------------------
     // DOI helper unit tests
     // ------------------------------------------------------------------

src/commands/upload.rs

@@ -1,6 +1,6 @@
 use crate::cache::{create_authenticated_conn, load_cache_with_token_refresh};
 use crate::commands::shared::{
-    find_file_by_name, find_folder_limited, find_lab_in_cache, nfc, parse_remote_path,
+    find_file_by_name, find_folder_limited, find_laboratory, nfc, parse_remote_path,
 };
 use crate::connection::{ApiRequestLimiter, MDRSConnection};
 use crate::models::folder::FolderSimple;
@@ -20,7 +20,7 @@ pub async fn upload(
     let cache = load_cache_with_token_refresh(&remote).await?;
     let conn = Arc::new(create_authenticated_conn(&remote, &cache)?);
     let limiter = ApiRequestLimiter::new(crate::settings::SETTINGS.concurrent);
-    let lab = find_lab_in_cache(&cache, &labname)?;
+    let lab = find_laboratory(&conn, Some(&cache), &labname).await?;
     let dest_folder = find_folder_limited(&conn, &limiter, lab.id, &r_path, None).await?;
 
     // Normalize local_path: resolve to an absolute canonical path so that
@@ -35,13 +35,12 @@ pub async fn upload(
         let remote_files = conn
             .list_all_files_limited(&dest_folder.id, &limiter)
             .await?;
-        if skip_if_exists {
-            if let Some(rf) = find_file_by_name(&remote_files, &filename) {
-                if rf.size == std::fs::metadata(local)?.len() {
-                    println!("{}{}", dest_folder.path, filename);
-                    return Ok(());
-                }
-            }
+        if skip_if_exists
+            && let Some(rf) = find_file_by_name(&remote_files, &filename)
+            && rf.size == std::fs::metadata(local)?.len()
+        {
+            println!("{}{}", dest_folder.path, filename);
+            return Ok(());
         }
         conn.upload_file_limited(&dest_folder.id, &local.to_string_lossy(), &limiter)
             .await?;
@@ -219,15 +218,13 @@ async fn process_upload_folder(
     let mut upload_jobs = Vec::new();
     for file_path in files {
         let filename = file_path.file_name().unwrap().to_string_lossy().to_string();
-        if skip_if_exists {
-            if let Some(rf) = find_file_by_name(&remote_files, &filename) {
-                if let Ok(meta) = std::fs::metadata(&file_path) {
-                    if rf.size == meta.len() {
-                        println!("{}{}", folder_detail.path, filename);
-                        continue;
-                    }
-                }
-            }
+        if skip_if_exists
+            && let Some(rf) = find_file_by_name(&remote_files, &filename)
+            && let Ok(meta) = std::fs::metadata(&file_path)
+            && rf.size == meta.len()
+        {
+            println!("{}{}", folder_detail.path, filename);
+            continue;
         }
         upload_jobs.push(UploadJob {
             folder_id: remote_id.clone(),
@@ -267,10 +264,10 @@ async fn drive_upload_tasks(
                 }
             }
             (true, false) => {
-                if let Some(result) = upload_tasks.join_next().await {
-                    if let Err(err) = flatten_join_result(result) {
-                        errors.push(err.to_string());
-                    }
+                if let Some(result) = upload_tasks.join_next().await
+                    && let Err(err) = flatten_join_result(result)
+                {
+                    errors.push(err.to_string());
                 }
             }
             (false, false) => {
@@ -289,11 +286,10 @@ async fn drive_upload_tasks(
                         }
                     }
                     result = upload_tasks.join_next() => {
-                        if let Some(result) = result {
-                            if let Err(err) = flatten_join_result(result) {
+                        if let Some(result) = result
+                            && let Err(err) = flatten_join_result(result) {
                                 errors.push(err.to_string());
                             }
-                        }
                     }
                 }
             }

src/commands/whoami.rs

@@ -1,9 +1,14 @@
+use crate::cache::create_readonly_conn;
+
+/// Ask the server who it thinks is calling.
+///
+/// The cached name is only what was true at login: an account disabled or removed since
+/// then would still answer from the cache, which is the one thing this command exists to
+/// tell the user. A session the server no longer honours reads as anonymous.
 pub async fn whoami(remote: &str) -> Result<(), anyhow::Error> {
-    match crate::cache::load_cache(remote) {
-        Ok(cache) => match cache.user {
-            Some(user) => println!("{}", user.username),
-            None => println!("(Anonymous)"),
-        },
+    let (conn, _cache) = create_readonly_conn(remote).await?;
+    match conn.get_current_user().await {
+        Ok(user) => println!("{}", user.username),
         Err(_) => println!("(Anonymous)"),
     }
     Ok(())

src/connection.rs

@@ -1,9 +1,14 @@
+use anyhow::bail;
 use reqwest::header::{ACCEPT, AUTHORIZATION, HeaderMap, HeaderValue, USER_AGENT};
 use reqwest::{Client, Response};
 use serde::Serialize;
 use std::sync::Arc;
 use tokio::sync::{OwnedSemaphorePermit, Semaphore};
 
+/// Shown when a request was refused twice for a token that was current when it left.
+pub const SERVER_BUSY_MESSAGE: &str = "The server took too long to start handling the request and may be overloaded. \
+Try again, or reduce the number of parallel transfers.";
+
 fn build_user_agent() -> String {
     let info = os_info::get();
     let mut parts = vec![info.os_type().to_string()];
@@ -90,6 +95,12 @@ impl MDRSConnection {
         }
     }
 
+    /// Same as `connection_with_fresh_token`, for callers that manage their own retry
+    /// because the request body cannot simply be sent twice.
+    pub async fn connection_with_fresh_token_for_retry(&self) -> Result<Self, anyhow::Error> {
+        self.connection_with_fresh_token().await
+    }
+
     async fn connection_with_fresh_token(&self) -> Result<Self, anyhow::Error> {
         match (&self.remote, &self.token) {
             (Some(remote), Some(_)) => {
@@ -122,56 +133,87 @@ impl MDRSConnection {
         headers
     }
 
-    pub async fn get(&self, path: &str) -> Result<Response, anyhow::Error> {
+    /// Send a request, and send it once more if the server found the access token
+    /// expired. A request can wait in the server's queue for longer than the token it
+    /// was sent with lives, so a refusal here need not mean the session is over.
+    ///
+    /// The retry goes back through `connection_with_fresh_token`, which re-reads the
+    /// cache under the lock: if another process refreshed while this request waited,
+    /// its token is reused rather than a second one being minted.
+    async fn send_with_retry<F>(&self, build: F) -> Result<Response, anyhow::Error>
+    where
+        F: Fn(&MDRSConnection) -> reqwest::RequestBuilder,
+    {
         let conn = self.connection_with_fresh_token().await?;
-        Ok(conn
-            .client
-            .get(conn.build_url(path))
-            .headers(conn.prepare_headers())
-            .send()
-            .await?)
+        let response = build(&conn).send().await?;
+        if response.status() != reqwest::StatusCode::UNAUTHORIZED {
+            return Ok(response);
+        }
+        // Only a stale access token is worth a second attempt, and the sign of one is a
+        // different token coming back. A wrong folder password, an anonymous request, or
+        // a session that has really ended all leave it untouched, and those refusals
+        // belong to the caller to report.
+        let retry_conn = self.connection_with_fresh_token().await?;
+        if retry_conn.token == conn.token {
+            return Ok(response);
+        }
+        let response = build(&retry_conn).send().await?;
+        if response.status() == reqwest::StatusCode::UNAUTHORIZED {
+            // Refused twice, the second time with a token that was current when it left.
+            // The session is fine; the server is not starting requests before their
+            // credentials lapse, which is worth saying plainly rather than sending the
+            // user off to log in again.
+            bail!(SERVER_BUSY_MESSAGE);
+        }
+        Ok(response)
+    }
+
+    pub async fn get(&self, path: &str) -> Result<Response, anyhow::Error> {
+        self.send_with_retry(|conn| {
+            conn.client
+                .get(conn.build_url(path))
+                .headers(conn.prepare_headers())
+        })
+        .await
     }
 
     pub async fn get_with_query<Q>(&self, path: &str, query: &Q) -> Result<Response, anyhow::Error>
     where
         Q: Serialize + ?Sized,
     {
-        let conn = self.connection_with_fresh_token().await?;
-        Ok(conn
-            .client
-            .get(conn.build_url(path))
-            .headers(conn.prepare_headers())
-            .query(query)
-            .send()
-            .await?)
+        self.send_with_retry(|conn| {
+            conn.client
+                .get(conn.build_url(path))
+                .headers(conn.prepare_headers())
+                .query(query)
+        })
+        .await
     }
 
     pub async fn get_url(&self, url: &str) -> Result<Response, anyhow::Error> {
-        let conn = self.connection_with_fresh_token().await?;
-        Ok(conn
-            .client
-            .get(if url.starts_with("http") {
-                url.to_string()
-            } else {
-                conn.build_url(url)
-            })
-            .headers(conn.prepare_headers())
-            .send()
-            .await?)
+        self.send_with_retry(|conn| {
+            conn.client
+                .get(if url.starts_with("http") {
+                    url.to_string()
+                } else {
+                    conn.build_url(url)
+                })
+                .headers(conn.prepare_headers())
+        })
+        .await
     }
 
     pub async fn post_json<B>(&self, path: &str, body: &B) -> Result<Response, anyhow::Error>
     where
         B: Serialize + ?Sized,
     {
-        let conn = self.connection_with_fresh_token().await?;
-        Ok(conn
-            .client
-            .post(conn.build_url(path))
-            .headers(conn.prepare_headers())
-            .json(body)
-            .send()
-            .await?)
+        self.send_with_retry(|conn| {
+            conn.client
+                .post(conn.build_url(path))
+                .headers(conn.prepare_headers())
+                .json(body)
+        })
+        .await
     }
 
     pub async fn post_multipart(
@@ -190,13 +232,12 @@ impl MDRSConnection {
     }
 
     pub async fn delete(&self, path: &str) -> Result<Response, anyhow::Error> {
-        let conn = self.connection_with_fresh_token().await?;
-        Ok(conn
-            .client
-            .delete(conn.build_url(path))
-            .headers(conn.prepare_headers())
-            .send()
-            .await?)
+        self.send_with_retry(|conn| {
+            conn.client
+                .delete(conn.build_url(path))
+                .headers(conn.prepare_headers())
+        })
+        .await
     }
 
     pub async fn delete_with_query<Q>(
@@ -207,13 +248,48 @@ impl MDRSConnection {
     where
         Q: Serialize + ?Sized,
     {
-        let conn = self.connection_with_fresh_token().await?;
-        Ok(conn
-            .client
-            .delete(conn.build_url(path))
-            .headers(conn.prepare_headers())
-            .query(query)
-            .send()
-            .await?)
+        self.send_with_retry(|conn| {
+            conn.client
+                .delete(conn.build_url(path))
+                .headers(conn.prepare_headers())
+                .query(query)
+        })
+        .await
+    }
+}
+
+#[cfg(test)]
+mod retry_tests {
+    use super::*;
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+    use tokio::net::TcpListener;
+
+    /// A refusal that no new token could answer belongs to the caller: an anonymous
+    /// request, a wrong folder password and an ended session all look like this, and
+    /// sending the same thing twice would only repeat the refusal.
+    #[tokio::test]
+    async fn a_refusal_is_handed_back_when_the_token_cannot_change() {
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut buf = [0u8; 4096];
+            let _ = stream.read(&mut buf).await.unwrap();
+            stream
+                .write_all(
+                    b"HTTP/1.1 401 Unauthorized\r\ncontent-length: 0\r\nconnection: close\r\n\r\n",
+                )
+                .await
+                .unwrap();
+        });
+
+        // No remote and no token, so nothing can be refreshed and the request must not
+        // be sent a second time. The stub answers once and would hang on a retry.
+        let conn = MDRSConnection::new(&format!("http://{addr}"));
+        let response = conn.get("v3/anything/").await.unwrap();
+        server.await.unwrap();
+
+        assert_eq!(response.status(), reqwest::StatusCode::UNAUTHORIZED);
     }
 }

src/error.rs

@@ -1,3 +1,33 @@
+use anyhow::anyhow;
+use serde::Deserialize;
+
+/// The error envelope the API answers with (drf-standardized-errors).
+#[derive(Deserialize)]
+struct ApiErrors {
+    errors: Vec<ApiError>,
+}
+
+#[derive(Deserialize)]
+struct ApiError {
+    detail: String,
+}
+
+/// Turn a refused response into an error carrying what the server actually said.
+///
+/// A status code on its own leaves the user guessing. The reason - a permission, a
+/// quota, a name already taken - is in the body the API sends along with it, and that
+/// is the part worth showing.
+pub async fn response_error(context: &str, resp: reqwest::Response) -> anyhow::Error {
+    let status = resp.status();
+    let body = resp.text().await.unwrap_or_default();
+    match serde_json::from_str::<ApiErrors>(&body) {
+        Ok(parsed) if !parsed.errors.is_empty() => {
+            anyhow!("{}: {}", context, parsed.errors[0].detail)
+        }
+        _ => anyhow!("{}: {}", context, status),
+    }
+}
+
 /// Print the error message and exit with code 2.
 /// JSON deserialization errors produce a friendlier message matching Python's
 /// JSONDecodeError handling.
@@ -23,3 +53,53 @@ fn is_json_error(e: &(dyn std::error::Error + 'static)) -> bool {
     }
     false
 }
+
+#[cfg(test)]
+mod response_error_tests {
+    use super::*;
+
+    async fn refused_with(body: &'static str, content_type: &'static str) -> String {
+        use tokio::io::{AsyncReadExt, AsyncWriteExt};
+        use tokio::net::TcpListener;
+
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut buf = [0u8; 4096];
+            let _ = stream.read(&mut buf).await.unwrap();
+            let response = format!(
+                "HTTP/1.1 403 Forbidden\r\ncontent-type: {}\r\ncontent-length: {}\r\nconnection: close\r\n\r\n{}",
+                content_type,
+                body.len(),
+                body
+            );
+            stream.write_all(response.as_bytes()).await.unwrap();
+        });
+
+        let resp = reqwest::get(format!("http://{addr}/")).await.unwrap();
+        let message = response_error("Upload failed", resp).await.to_string();
+        server.await.unwrap();
+        message
+    }
+
+    /// The reason the server gave is what the user needs, not the number that carried it.
+    #[tokio::test]
+    async fn the_servers_own_message_is_reported() {
+        let message = refused_with(
+            r#"{"type":"client_error","errors":[{"code":"permission_denied","detail":"You do not have permission.","attr":null}]}"#,
+            "application/json",
+        )
+        .await;
+
+        assert_eq!(message, "Upload failed: You do not have permission.");
+    }
+
+    /// A gateway that answers in HTML has nothing to quote, so the status still stands in.
+    #[tokio::test]
+    async fn the_status_stands_in_when_the_body_says_nothing() {
+        let message = refused_with("<html>nope</html>", "text/html").await;
+
+        assert_eq!(message, "Upload failed: 403 Forbidden");
+    }
+}

src/main.rs

@@ -201,7 +201,7 @@ fn run(cli: Cli) {
         }
         Commands::SelfUpdate { yes } => {
             if let Err(e) = build_rt().block_on(commands::selfupdate::selfupdate(yes)) {
-                handle_error(e.into());
+                handle_error(e);
             }
         }
     }

src/settings.rs

@@ -13,14 +13,11 @@ impl Settings {
     fn load() -> Self {
         let config_dirname = std::env::var("MDRS_CLIENT_CONFIG_DIRNAME")
             .ok()
-            .map(|s| {
-                if s.starts_with("~/") {
-                    dirs::home_dir()
-                        .unwrap_or_else(|| std::path::PathBuf::from("."))
-                        .join(&s[2..])
-                } else {
-                    std::path::PathBuf::from(&s)
-                }
+            .map(|s| match s.strip_prefix("~/") {
+                Some(rest) => dirs::home_dir()
+                    .unwrap_or_else(|| std::path::PathBuf::from("."))
+                    .join(rest),
+                None => std::path::PathBuf::from(&s),
             })
             .unwrap_or_else(|| {
                 dirs::home_dir()