diff --git a/crates/spaceshd/src/main.rs b/crates/spaceshd/src/main.rs
index e12c513..2715dc4 100644
--- a/crates/spaceshd/src/main.rs
+++ b/crates/spaceshd/src/main.rs
@@ -1,4 +1,5 @@
 mod lifecycle;
+mod registry;
 mod surface;
 
 fn main() {
diff --git a/crates/spaceshd/src/registry.rs b/crates/spaceshd/src/registry.rs
new file mode 100644
index 0000000..872696b
--- /dev/null
+++ b/crates/spaceshd/src/registry.rs
@@ -0,0 +1,105 @@
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::sync::atomic::{AtomicU64, Ordering};
+use spacesh_proto::{SurfaceId, WorkspaceId};
+use crate::surface::SurfaceHandle;
+
+#[derive(Clone)]
+pub struct WorkspaceMeta {
+    pub id: WorkspaceId,
+    pub path: PathBuf,
+}
+
+/// Single-threaded owner of all live surfaces and workspaces.
+/// Lives inside the server task; not shared across threads.
+#[derive(Default)]
+pub struct Registry {
+    counter: AtomicU64,
+    workspaces: HashMap<WorkspaceId, WorkspaceMeta>,
+    /// path → workspace, so `open` is idempotent.
+    by_path: HashMap<PathBuf, WorkspaceId>,
+    surfaces: HashMap<SurfaceId, SurfaceHandle>,
+}
+
+impl Registry {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    fn next_id(&self, prefix: &str) -> String {
+        let n = self.counter.fetch_add(1, Ordering::Relaxed);
+        format!("{prefix}_{n:x}")
+    }
+
+    /// Idempotent: opening the same canonicalized path returns the existing workspace.
+    pub fn open_workspace(&mut self, path: PathBuf) -> WorkspaceMeta {
+        let canonical = path.canonicalize().unwrap_or(path);
+        if let Some(id) = self.by_path.get(&canonical) {
+            return self.workspaces[id].clone();
+        }
+        let id = WorkspaceId(self.next_id("w"));
+        let meta = WorkspaceMeta { id: id.clone(), path: canonical.clone() };
+        self.workspaces.insert(id.clone(), meta.clone());
+        self.by_path.insert(canonical, id);
+        meta
+    }
+
+    pub fn workspace(&self, id: &WorkspaceId) -> Option<&WorkspaceMeta> {
+        self.workspaces.get(id)
+    }
+
+    pub fn new_surface_id(&self) -> SurfaceId {
+        SurfaceId(self.next_id("s"))
+    }
+
+    pub fn insert_surface(&mut self, handle: SurfaceHandle) {
+        self.surfaces.insert(handle.id.clone(), handle);
+    }
+
+    pub fn surface(&self, id: &SurfaceId) -> Option<&SurfaceHandle> {
+        self.surfaces.get(id)
+    }
+
+    pub fn remove_surface(&mut self, id: &SurfaceId) -> Option<SurfaceHandle> {
+        self.surfaces.remove(id)
+    }
+
+    /// Snapshot for the `status` command: (workspace, its surface ids).
+    pub fn status(&self) -> Vec<(WorkspaceMeta, Vec<SurfaceId>)> {
+        self.workspaces
+            .values()
+            .map(|w| {
+                let sids = self
+                    .surfaces
+                    .values()
+                    .filter(|s| s.workspace_id == w.id)
+                    .map(|s| s.id.clone())
+                    .collect();
+                (w.clone(), sids)
+            })
+            .collect()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn open_is_idempotent_per_path() {
+        let mut reg = Registry::new();
+        let dir = std::env::temp_dir();
+        let a = reg.open_workspace(dir.clone());
+        let b = reg.open_workspace(dir.clone());
+        assert_eq!(a.id, b.id);
+    }
+
+    #[test]
+    fn ids_are_unique_and_prefixed() {
+        let reg = Registry::new();
+        let s1 = reg.new_surface_id();
+        let s2 = reg.new_surface_id();
+        assert!(s1.0.starts_with("s_"));
+        assert_ne!(s1, s2);
+    }
+}