diff --git a/crates/collab/src/rpc.rs b/crates/collab/src/rpc.rs
index 40ce95bce6..b8e16a8650 100644
--- a/crates/collab/src/rpc.rs
+++ b/crates/collab/src/rpc.rs
@@ -605,6 +605,7 @@ impl Server {
             guest_user_id = state.user_id_for_connection(request.sender_id)?;
         };
 
+        tracing::info!(project_id, %host_user_id, %host_connection_id, "join project");
         let has_contact = self
             .app_state
             .db
@@ -760,6 +761,12 @@ impl Server {
         {
             let mut store = self.store_mut().await;
             project = store.leave_project(sender_id, project_id)?;
+            tracing::info!(
+                project_id,
+                host_user_id = %project.host_user_id,
+                host_connection_id = %project.host_connection_id,
+                "leave project"
+            );
 
             if project.remove_collaborator {
                 broadcast(sender_id, project.connection_ids, |conn_id| {
@@ -833,6 +840,7 @@ impl Server {
             &request.payload.updated_entries,
             request.payload.scan_id,
         )?;
+        // TODO: log `extension_counts` from `Worktree`.
 
         broadcast(request.sender_id, connection_ids, |connection_id| {
             self.peer
diff --git a/crates/collab/src/rpc/store.rs b/crates/collab/src/rpc/store.rs
index cad293876e..1d88264d72 100644
--- a/crates/collab/src/rpc/store.rs
+++ b/crates/collab/src/rpc/store.rs
@@ -3,7 +3,13 @@ use anyhow::{anyhow, Result};
 use collections::{hash_map::Entry, BTreeMap, HashMap, HashSet};
 use rpc::{proto, ConnectionId, Receipt};
 use serde::Serialize;
-use std::{collections::hash_map, mem, path::PathBuf};
+use std::{
+    collections::hash_map,
+    ffi::{OsStr, OsString},
+    mem,
+    path::{Path, PathBuf},
+    str,
+};
 use tracing::instrument;
 
 #[derive(Default, Serialize)]
@@ -43,6 +49,8 @@ pub struct Worktree {
     #[serde(skip)]
     pub entries: HashMap<u64, proto::Entry>,
     #[serde(skip)]
+    pub extension_counts: HashMap<OsString, usize>,
+    #[serde(skip)]
     pub diagnostic_summaries: BTreeMap<PathBuf, proto::DiagnosticSummary>,
     pub scan_id: u64,
 }
@@ -575,9 +583,22 @@ impl Store {
         let metadata_changed = worktree_root_name != worktree.root_name;
         worktree.root_name = worktree_root_name.to_string();
         for entry_id in removed_entries {
-            worktree.entries.remove(&entry_id);
+            if let Some(entry) = worktree.entries.remove(&entry_id) {
+                if let Some(extension) = extension_for_entry(&entry) {
+                    if let Some(count) = worktree.extension_counts.get_mut(extension) {
+                        *count = count.saturating_sub(1);
+                    }
+                }
+            }
         }
         for entry in updated_entries {
+            if let Some(extension) = extension_for_entry(&entry) {
+                if let Some(count) = worktree.extension_counts.get_mut(extension) {
+                    *count += 1;
+                } else {
+                    worktree.extension_counts.insert(extension.into(), 1);
+                }
+            }
             worktree.entries.insert(entry.id, entry.clone());
         }
         worktree.scan_id = scan_id;
@@ -732,3 +753,10 @@ impl Channel {
         self.connection_ids.iter().copied().collect()
     }
 }
+
+fn extension_for_entry(entry: &proto::Entry) -> Option<&OsStr> {
+    str::from_utf8(&entry.path)
+        .ok()
+        .map(Path::new)
+        .and_then(|p| p.extension())
+}