scope file ops (ws, api, tools) to per-user context

crates/core-api/src/events.rs

@@ -149,10 +149,12 @@ pub enum ServerEvent {
     FileChanged {
         path: String,
     },
-    /// Ask the frontend to open a file for the user. Behaves like
-    /// `window.openFile(path)`: navigates to the file viewer page for markdown /
-    /// text / images, or opens an HTML file in a new browser tab. Emitted by
-    /// the future `show_file_to_user` interface tool (not wired yet).
+    /// Ask the frontend to open a file for the user, via `window.openFile(path)`:
+    /// the file-viewer page renders every kind (markdown / text / images / SVG /
+    /// PDF / LaTeX compiled server-side, and HTML live in an origin-isolated
+    /// iframe). Emitted by the `show_file_to_user` interface tool; `path` is the
+    /// caller's canonical **agent path** (`~/…`, `shared/{X}/…`, `projects/…`),
+    /// which the viewer fetches back through `GET /api/file`.
     OpenFile {
         path: String,
     },

crates/core-api/src/user_fs.rs

@@ -161,6 +161,65 @@ impl UserFs {
         let stripped = strip_home_prefix(agent_path);
         normalize(&self.container_home.join(stripped))
     }
+
+    /// Reverse of [`to_container`](Self::to_container) for an already-absolute path:
+    /// map a **container-absolute** path (`/root/…`, `/root/shared/{X}/…`,
+    /// `/root/projects/{O}/{S}/…`) back to the agent vocabulary. Shared and project
+    /// mounts nest *under* `container_home`, so they are matched **first** — otherwise
+    /// `/root/shared/X` would strip against the home base and mis-route.
+    ///
+    /// Returns `None` when `abs` lies outside every one of this user's container mounts
+    /// (i.e. it points outside their view) — the caller rejects it fail-closed. Purely
+    /// lexical: no membership check, no filesystem access.
+    pub fn container_to_agent(&self, abs: &Path) -> Option<String> {
+        let abs = normalize(abs);
+        for m in &self.shared {
+            if let Ok(tail) = abs.strip_prefix(&m.container) {
+                return Some(agent_join(&format!("shared/{}", m.name), tail));
+            }
+        }
+        for m in &self.projects {
+            if let Ok(tail) = abs.strip_prefix(&m.container) {
+                return Some(agent_join(&format!("projects/{}/{}", m.owner_username, m.slug), tail));
+            }
+        }
+        abs.strip_prefix(&self.container_home)
+            .ok()
+            .map(|tail| agent_join("~", tail))
+    }
+
+    /// Normalize any path arriving from the show-file / file-viewer surface into a
+    /// **canonical agent path** the UI can display and echo back: a relative or `~/…`
+    /// path is cleaned and rooted (`report.md` → `~/report.md`, `shared/X/y` and
+    /// `projects/O/S/y` keep their root); a container-absolute path is reverse-mapped
+    /// via [`container_to_agent`](Self::container_to_agent).
+    ///
+    /// Returns `None` only for an absolute path outside every container mount — the
+    /// caller rejects it fail-closed. Purely lexical (`.`/`..` collapse, `..` clamps at
+    /// the root); membership + on-disk containment are enforced later, in skald-core.
+    pub fn to_agent_display(&self, input: &str) -> Option<String> {
+        let p = Path::new(input);
+        if p.is_absolute() {
+            return self.container_to_agent(p);
+        }
+        let cleaned = normalize(Path::new(strip_home_prefix(input)));
+        let cleaned = cleaned.to_string_lossy().replace('\\', "/");
+        let root = cleaned.split('/').next().unwrap_or("");
+        if root == "shared" || root == "projects" {
+            Some(cleaned)
+        } else if cleaned.is_empty() {
+            Some("~".to_string())
+        } else {
+            Some(format!("~/{cleaned}"))
+        }
+    }
+}
+
+/// Join an agent-path base (`~`, `shared/X`, `projects/O/S`) with a tail relative to
+/// the mount, normalizing separators. An empty tail yields the bare base.
+fn agent_join(base: &str, tail: &Path) -> String {
+    let t = tail.to_string_lossy().replace('\\', "/");
+    if t.is_empty() { base.to_string() } else { format!("{base}/{t}") }
 }
 
 /// Strips a leading `~/`, bare `~`, or `./` so what remains is relative to the home.

crates/skald-core/src/tools/fs/mod.rs

@@ -212,6 +212,29 @@ pub(crate) fn resolve_host_path(fs: &UserFs, agent_path: &str) -> Result<PathBuf
     Ok(canon)
 }
 
+/// Resolve a path arriving from the show-file / file-viewer surface into
+/// `(host_abs, agent_display)`, scoped to the caller's workspace.
+///
+/// Accepts the agent vocabulary (`~/…`, `shared/{X}/…`, `projects/{O}/{S}/…`, bare
+/// relative) **and** a container-absolute path (`/root/…`); any path outside the
+/// caller's container view is rejected fail-closed. `agent_display` is the canonical
+/// path the UI shows and echoes back to `/api/file`, so the tool, the viewer fetch
+/// and the watcher all key on the same string. Memory paths (`user-memory/…`,
+/// `shared-memory/…`) are virtual notes, not disk files — rejected with a clear error.
+///
+/// This is the single entry point the server shell uses for `show_file_to_user`,
+/// `GET /api/file` and `GET /api/file/watch`; containment (canonicalize +
+/// prefix-check, symlink-aware) is handled by [`resolve_host_path`].
+pub fn resolve_view_path(fs: &UserFs, input: &str) -> Result<(PathBuf, String)> {
+    if classify_memory(input).is_some() {
+        anyhow::bail!("memory notes can't be opened in the file viewer: {input}");
+    }
+    let agent = fs.to_agent_display(input)
+        .ok_or_else(|| anyhow::anyhow!("path is outside your workspace: {input}"))?;
+    let host = resolve_host_path(fs, &agent)?;
+    Ok((host, agent))
+}
+
 /// Rewrites the `path` argument of a physical fs-tool call to the resolved absolute
 /// host path, so the on-disk `execute` (which takes absolute paths as-is) acts on
 /// the caller's per-user workspace rather than the process working directory.

crates/skald-core/src/tools/show_file.rs

@@ -2,22 +2,28 @@ use std::sync::Arc;
 
 use serde_json::{Value, json};
 
+use core_api::user_fs::SharedFs;
+
 use crate::chat_hub::ChatHub;
 use crate::events::{GlobalEvent, ServerEvent};
 use crate::session::handler::{InterfaceTool, ToolFuture};
 use crate::tools::fs;
 use crate::tools::tool_names::SHOW_FILE_TO_USER;
 
-/// Build a `show_file_to_user` InterfaceTool bound to a `ChatHub` and a source.
+/// Build a `show_file_to_user` InterfaceTool bound to a `ChatHub`, a source and the
+/// caller's [`SharedFs`] (their per-user filesystem view).
 ///
 /// Injected only for SPA clients (web copilot + mobile) at the WebSocket entry
 /// point, so Telegram — which has its own `send_attachment` — never sees it.
 ///
-/// When called, it emits a `ServerEvent::OpenFile` to the source's connected
-/// clients. The frontend routes it: HTML opens in a new browser tab, everything
-/// else (Markdown / code / raster images / SVG / PDF / LaTeX — which is compiled
-/// to PDF server-side) opens in the file-viewer page.
-pub fn make_tool(hub: Arc<ChatHub>, source: String) -> InterfaceTool {
+/// The path is resolved through the caller's own workspace (`resolve_view_path`):
+/// `~/…`, `shared/{X}/…`, `projects/{O}/{S}/…`, a bare relative path, or a
+/// container-absolute `/root/…` — anything outside the container view is refused.
+/// It then emits a `ServerEvent::OpenFile` carrying the **canonical agent path**, so
+/// the file-viewer page fetches the same file back through `/api/file` (which applies
+/// the identical per-user resolution). The frontend renders every kind in the viewer
+/// (HTML live in an origin-isolated iframe; LaTeX compiled to PDF server-side).
+pub fn make_tool(hub: Arc<ChatHub>, source: String, fs: SharedFs) -> InterfaceTool {
     let definition = json!({
         "type": "function",
         "function": {
@@ -41,7 +47,10 @@ pub fn make_tool(hub: Arc<ChatHub>, source: String) -> InterfaceTool {
                 "properties": {
                     "path": {
                         "type": "string",
-                        "description": "Path of the file to show. Relative to the project root, or absolute."
+                        "description": "Path of the file to show, in your own workspace: relative to your \
+                                         home (e.g. `report.md` or `~/report.md`), a `shared/<folder>/…` or \
+                                         `projects/<owner>/<slug>/…` path, or an absolute container path \
+                                         (`/root/…`). Paths outside your workspace are refused."
                     }
                 },
                 "required": ["path"]
@@ -52,20 +61,24 @@ pub fn make_tool(hub: Arc<ChatHub>, source: String) -> InterfaceTool {
     let handler = Arc::new(move |args: Value| -> ToolFuture {
         let hub    = Arc::clone(&hub);
         let source = source.clone();
+        let fs     = fs.clone();
         Box::pin(async move {
             let path = args["path"]
                 .as_str()
                 .ok_or_else(|| anyhow::anyhow!("show_file_to_user: missing required parameter 'path'"))?;
 
-            let abs = fs::resolve(path)?;
+            // Resolve against the caller's workspace snapshot: gives the host path to
+            // stat and the canonical agent path the viewer will fetch back.
+            let user_fs = fs.load();
+            let (abs, display) = fs::resolve_view_path(user_fs.as_ref(), path)
+                .map_err(|e| anyhow::anyhow!("show_file_to_user: {e}"))?;
             if !abs.exists() {
-                anyhow::bail!("show_file_to_user: file not found: {path}");
+                anyhow::bail!("show_file_to_user: file not found: {display}");
             }
             if abs.is_dir() {
-                anyhow::bail!("show_file_to_user: '{path}' is a directory, not a file");
+                anyhow::bail!("show_file_to_user: '{display}' is a directory, not a file");
             }
 
-            let display = fs::relativize_for_display(path);
             hub.emit(GlobalEvent {
                 source:     Some(source),
                 session_id: None,