feat(file): add GET /api/fs/browse shallow host-file picker (#235)

Restores the WebUI host-file browsing endpoint removed during M6 by
porting the pre-M6 Express directoryApi.ts to Rust. Unlike /api/fs/dir
(workspace tree) this is a shallow lister with navigation hints
(can_go_up, parent_path) and a __ROOT__ sentinel for the Windows drive
picker. Allowed roots widen to cwd + home + Windows drives + "/" on
Unix because the host-file picker legitimately needs to reach outside
any single workspace. Wired through FileRouterState.browse_roots so
the allow-list can be injected in tests.

Unblocks the DirectorySelectionModal in WebUI mode which was hitting
404s against the legacy URL.

Co-authored-by: zk <>

Author: kaizhou-lab

Cargo.lock

@@ -126,6 +126,64 @@ pub struct CancelZipRequest {
     pub request_id: String,
 }
 
+/// Query parameters for `GET /api/fs/browse` — shallow directory browser.
+///
+/// Unlike `/api/fs/dir` (which returns a recursive tree scoped to a workspace
+/// root), `browse` is a WebUI-only host-file picker: it lists a single
+/// directory level, surfaces navigation hints (`can_go_up`, `parent_path`),
+/// and on Windows supports a `__ROOT__` sentinel for the drive-list screen.
+#[derive(Debug, Deserialize)]
+pub struct BrowseDirectoryQuery {
+    /// Directory to list. Empty string means "use default" (Windows: drive
+    /// list; Unix: current working directory). `"__ROOT__"` on Windows is
+    /// treated the same as an empty path.
+    #[serde(default)]
+    pub path: Option<String>,
+    /// When true, include regular files in the response. Defaults to false
+    /// (directories only).
+    #[serde(default)]
+    pub show_files: Option<String>,
+}
+
+/// A single entry in a `/api/fs/browse` response.
+///
+/// Uses camelCase on the wire to match the original Express contract the
+/// frontend `DirectorySelectionModal` still consumes.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+#[serde(rename_all = "camelCase")]
+pub struct BrowseEntry {
+    pub name: String,
+    pub path: String,
+    pub is_directory: bool,
+    pub is_file: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub size: Option<u64>,
+    /// Last-modified time as milliseconds since the unix epoch. Absent when
+    /// the entry has no readable metadata (e.g. a Windows drive stub).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub modified: Option<i64>,
+}
+
+/// Response body for `GET /api/fs/browse`.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+#[serde(rename_all = "camelCase")]
+pub struct BrowseDirectoryResponse {
+    /// The resolved directory currently being listed. Empty string when the
+    /// response is a Windows drive-list screen.
+    pub current_path: String,
+    /// Path to navigate to when the user clicks "up". `None` when already at
+    /// the root. Value `"__ROOT__"` is a sentinel used on Windows to mean
+    /// "return to the drive-list screen".
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub parent_path: Option<String>,
+    pub items: Vec<BrowseEntry>,
+    pub can_go_up: bool,
+    pub truncated: bool,
+    /// True when the response represents the Windows drive-list screen.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub is_root: Option<bool>,
+}
+
 // ---------------------------------------------------------------------------
 // A. Core file operations — Response DTOs
 // ---------------------------------------------------------------------------

crates/aionui-api-types/src/file.rs

@@ -75,12 +75,13 @@ pub use extension::{
     InstallExtensionRequest, PermissionDetailResponse, PermissionSummaryResponse,
 };
 pub use file::{
-    CancelZipRequest, CopyFilesRequest, CopyFilesResponse, CreateTempFileRequest, DirOrFileResponse,
-    FetchRemoteImageRequest, FileChangeInfoResponse, FileMetadataResponse, FileWatchRequest, GetFileMetadataRequest,
-    GetFilesByDirRequest, GetImageBase64Request, ListWorkspaceFilesRequest, ReadFileBufferRequest, ReadFileRequest,
-    RemoveEntryRequest, RenameRequest, RenameResponse, SnapshotBaselineRequest, SnapshotCompareResponse,
-    SnapshotDiscardRequest, SnapshotInfoResponse, SnapshotMode, SnapshotStageRequest, SnapshotWorkspaceRequest,
-    WorkspaceFlatFileResponse, WorkspaceOfficeWatchRequest, WriteFileRequest, ZipFileEntry, ZipRequest,
+    BrowseDirectoryQuery, BrowseDirectoryResponse, BrowseEntry, CancelZipRequest, CopyFilesRequest, CopyFilesResponse,
+    CreateTempFileRequest, DirOrFileResponse, FetchRemoteImageRequest, FileChangeInfoResponse, FileMetadataResponse,
+    FileWatchRequest, GetFileMetadataRequest, GetFilesByDirRequest, GetImageBase64Request, ListWorkspaceFilesRequest,
+    ReadFileBufferRequest, ReadFileRequest, RemoveEntryRequest, RenameRequest, RenameResponse, SnapshotBaselineRequest,
+    SnapshotCompareResponse, SnapshotDiscardRequest, SnapshotInfoResponse, SnapshotMode, SnapshotStageRequest,
+    SnapshotWorkspaceRequest, WorkspaceFlatFileResponse, WorkspaceOfficeWatchRequest, WriteFileRequest, ZipFileEntry,
+    ZipRequest,
 };
 pub use lifecycle::{GitHubReleaseAsset, SystemInfoResponse, UpdateCheckRequest, UpdateCheckResult, UpdateReleaseInfo};
 pub use mcp::{

crates/aionui-api-types/src/lib.rs

@@ -223,6 +223,7 @@ pub fn build_session_state(services: &AppServices, agent_service: Arc<AgentServi
 pub fn build_file_state(services: &AppServices) -> FileRouterState {
     let broadcaster = services.event_bus.clone();
     let allowed_roots = default_allowed_roots();
+    let browse_roots = aionui_file::browse::default_browse_roots();
     let file_service = Arc::new(FileService::new(broadcaster.clone(), allowed_roots.clone()));
     let watch_service = Arc::new(FileWatchService::new(broadcaster).expect("file watch service initialization"));
     let snapshot_service = Arc::new(SnapshotService::new());
@@ -231,6 +232,7 @@ pub fn build_file_state(services: &AppServices) -> FileRouterState {
         watch_service,
         snapshot_service,
         allowed_roots,
+        browse_roots,
     }
 }
 

crates/aionui-app/src/state_builders.rs

@@ -23,6 +23,7 @@ serde.workspace = true
 serde_json.workspace = true
 tracing.workspace = true
 dashmap.workspace = true
+dirs.workspace = true
 
 [dev-dependencies]
 tempfile = "3"