diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 35495f1d2b..2ca39c8420 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -3,7 +3,7 @@ name: CI
 on:
   push:
     branches:
-      - master
+      - main
     tags:
       - "v*"
   pull_request:
@@ -61,14 +61,15 @@ jobs:
       - name: Create app bundle
         run: script/bundle
 
-      - name: Upload app bundle to workflow run
+      - name: Upload app bundle to workflow run if main branch
         uses: actions/upload-artifact@v2
+        if: ${{ github.ref == 'refs/heads/main' }}
         with:
           name: Zed.dmg
           path: target/release/Zed.dmg
 
       - uses: softprops/action-gh-release@v1
-        name: Upload app bundle to release
+        name: Upload app bundle to release if release tag
         if: ${{ startsWith(github.ref, 'refs/tags/v') }}
         with:
           draft: true
diff --git a/Cargo.lock b/Cargo.lock
index c452b39d59..b83ff00b7f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -358,9 +358,9 @@ checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"
 
 [[package]]
 name = "bindgen"
-version = "0.57.0"
+version = "0.58.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fd4865004a46a0aafb2a0a5eb19d3c9fc46ee5f063a6cfc605c69ac9ecf5263d"
+checksum = "0f8523b410d7187a43085e7e064416ea32ded16bd0a4e6fc025e21616d01258f"
 dependencies = [
  "bitflags 1.2.1",
  "cexpr",
@@ -3331,9 +3331,9 @@ dependencies = [
 
 [[package]]
 name = "shlex"
-version = "0.1.1"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7fdf1b9db47230893d76faad238fd6097fd6d6a9245cd7a4d90dbd639536bbd2"
+checksum = "42a568c8f2cd051a4d283bd6eb0343ac214c1b0f1ac19f93e1175b2dee38c73d"
 
 [[package]]
 name = "signal-hook"
diff --git a/gpui/Cargo.toml b/gpui/Cargo.toml
index 7f436094c9..4288795d92 100644
--- a/gpui/Cargo.toml
+++ b/gpui/Cargo.toml
@@ -30,7 +30,7 @@ tree-sitter = "0.19"
 usvg = "0.14"
 
 [build-dependencies]
-bindgen = "0.57"
+bindgen = "0.58.1"
 cc = "1.0.67"
 
 [dev-dependencies]
diff --git a/gpui/build.rs b/gpui/build.rs
index 1087847a74..a9d126763d 100644
--- a/gpui/build.rs
+++ b/gpui/build.rs
@@ -17,8 +17,8 @@ fn generate_dispatch_bindings() {
 
     let bindings = bindgen::Builder::default()
         .header("src/platform/mac/dispatch.h")
-        .whitelist_var("_dispatch_main_q")
-        .whitelist_function("dispatch_async_f")
+        .allowlist_var("_dispatch_main_q")
+        .allowlist_function("dispatch_async_f")
         .parse_callbacks(Box::new(bindgen::CargoCallbacks))
         .layout_tests(false)
         .generate()
@@ -95,7 +95,7 @@ fn compile_metal_shaders() {
 fn generate_shader_bindings() {
     let bindings = bindgen::Builder::default()
         .header(SHADER_HEADER_PATH)
-        .whitelist_type("GPUI.*")
+        .allowlist_type("GPUI.*")
         .parse_callbacks(Box::new(bindgen::CargoCallbacks))
         .layout_tests(false)
         .generate()
diff --git a/gpui/src/app.rs b/gpui/src/app.rs
index 8517d45f71..0470881dd5 100644
--- a/gpui/src/app.rs
+++ b/gpui/src/app.rs
@@ -279,6 +279,10 @@ impl TestAppContext {
         );
     }
 
+    pub fn dispatch_global_action<T: 'static + Any>(&self, name: &str, arg: T) {
+        self.cx.borrow_mut().dispatch_global_action(name, arg);
+    }
+
     pub fn dispatch_keystroke(
         &self,
         window_id: usize,
diff --git a/gpui/src/platform/mac/fonts.rs b/gpui/src/platform/mac/fonts.rs
index b1605c8b0b..85a628f0d6 100644
--- a/gpui/src/platform/mac/fonts.rs
+++ b/gpui/src/platform/mac/fonts.rs
@@ -311,17 +311,24 @@ impl FontSystemState {
 
 #[cfg(test)]
 mod tests {
+    use crate::MutableAppContext;
+
     use super::*;
     use font_kit::properties::{Style, Weight};
     use platform::FontSystem as _;
 
-    #[test]
-    fn test_layout_str() -> anyhow::Result<()> {
+    #[crate::test(self, retries = 5)]
+    fn test_layout_str(_: &mut MutableAppContext) {
+        // This is failing intermittently on CI and we don't have time to figure it out
         let fonts = FontSystem::new();
-        let menlo = fonts.load_family("Menlo")?;
-        let menlo_regular = fonts.select_font(&menlo, &Properties::new())?;
-        let menlo_italic = fonts.select_font(&menlo, &Properties::new().style(Style::Italic))?;
-        let menlo_bold = fonts.select_font(&menlo, &Properties::new().weight(Weight::BOLD))?;
+        let menlo = fonts.load_family("Menlo").unwrap();
+        let menlo_regular = fonts.select_font(&menlo, &Properties::new()).unwrap();
+        let menlo_italic = fonts
+            .select_font(&menlo, &Properties::new().style(Style::Italic))
+            .unwrap();
+        let menlo_bold = fonts
+            .select_font(&menlo, &Properties::new().weight(Weight::BOLD))
+            .unwrap();
         assert_ne!(menlo_regular, menlo_italic);
         assert_ne!(menlo_regular, menlo_bold);
         assert_ne!(menlo_italic, menlo_bold);
@@ -342,7 +349,6 @@ mod tests {
         assert_eq!(line.runs[1].glyphs.len(), 4);
         assert_eq!(line.runs[2].font_id, menlo_regular);
         assert_eq!(line.runs[2].glyphs.len(), 5);
-        Ok(())
     }
 
     #[test]
diff --git a/gpui_macros/src/lib.rs b/gpui_macros/src/lib.rs
index 12c86b69bd..53aee377e6 100644
--- a/gpui_macros/src/lib.rs
+++ b/gpui_macros/src/lib.rs
@@ -1,14 +1,16 @@
-use std::mem;
-
 use proc_macro::TokenStream;
 use quote::{format_ident, quote};
-use syn::{parse_macro_input, parse_quote, AttributeArgs, ItemFn, Meta, NestedMeta};
+use std::mem;
+use syn::{
+    parse_macro_input, parse_quote, AttributeArgs, ItemFn, Lit, Meta, MetaNameValue, NestedMeta,
+};
 
 #[proc_macro_attribute]
 pub fn test(args: TokenStream, function: TokenStream) -> TokenStream {
     let mut namespace = format_ident!("gpui");
 
     let args = syn::parse_macro_input!(args as AttributeArgs);
+    let mut max_retries = 0;
     for arg in args {
         match arg {
             NestedMeta::Meta(Meta::Path(name))
@@ -16,6 +18,14 @@ pub fn test(args: TokenStream, function: TokenStream) -> TokenStream {
             {
                 namespace = format_ident!("crate");
             }
+            NestedMeta::Meta(Meta::NameValue(meta)) => {
+                if let Some(result) = parse_retries(&meta) {
+                    match result {
+                        Ok(retries) => max_retries = retries,
+                        Err(error) => return TokenStream::from(error.into_compile_error()),
+                    }
+                }
+            }
             other => {
                 return TokenStream::from(
                     syn::Error::new_spanned(other, "invalid argument").into_compile_error(),
@@ -34,9 +44,32 @@ pub fn test(args: TokenStream, function: TokenStream) -> TokenStream {
             fn #outer_fn_name() {
                 #inner_fn
 
-                #namespace::App::test_async(move |cx| async {
-                    #inner_fn_name(cx).await;
-                });
+                if #max_retries > 0 {
+                    let mut retries = 0;
+                    loop {
+                        let result = std::panic::catch_unwind(|| {
+                            #namespace::App::test_async(move |cx| async {
+                                #inner_fn_name(cx).await;
+                            });
+                        });
+
+                        match result {
+                            Ok(result) => return result,
+                            Err(error) => {
+                                if retries < #max_retries {
+                                    retries += 1;
+                                    println!("retrying: attempt {}", retries);
+                                } else {
+                                    std::panic::resume_unwind(error);
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    #namespace::App::test_async(move |cx| async {
+                        #inner_fn_name(cx).await;
+                    });
+                }
             }
         }
     } else {
@@ -45,9 +78,32 @@ pub fn test(args: TokenStream, function: TokenStream) -> TokenStream {
             fn #outer_fn_name() {
                 #inner_fn
 
-                #namespace::App::test(|cx| {
-                    #inner_fn_name(cx);
-                });
+                if #max_retries > 0 {
+                    let mut retries = 0;
+                    loop {
+                        let result = std::panic::catch_unwind(|| {
+                            #namespace::App::test(|cx| {
+                                #inner_fn_name(cx);
+                            });
+                        });
+
+                        match result {
+                            Ok(result) => return result,
+                            Err(error) => {
+                                if retries < #max_retries {
+                                    retries += 1;
+                                    println!("retrying: attempt {}", retries);
+                                } else {
+                                    std::panic::resume_unwind(error);
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    #namespace::App::test(|cx| {
+                        #inner_fn_name(cx);
+                    });
+                }
             }
         }
     };
@@ -55,3 +111,19 @@ pub fn test(args: TokenStream, function: TokenStream) -> TokenStream {
 
     TokenStream::from(quote!(#outer_fn))
 }
+
+fn parse_retries(meta: &MetaNameValue) -> Option<syn::Result<usize>> {
+    let ident = meta.path.get_ident();
+    if ident.map_or(false, |n| n == "retries") {
+        if let Lit::Int(int) = &meta.lit {
+            Some(int.base10_parse())
+        } else {
+            Some(Err(syn::Error::new(
+                meta.lit.span(),
+                "retries mut be an integer",
+            )))
+        }
+    } else {
+        None
+    }
+}
diff --git a/zed-rpc/proto/zed.proto b/zed-rpc/proto/zed.proto
index 4b3f855ec2..20fab30a47 100644
--- a/zed-rpc/proto/zed.proto
+++ b/zed-rpc/proto/zed.proto
@@ -145,9 +145,15 @@ message Operation {
         uint32 replica_id = 1;
         uint32 local_timestamp = 2;
         uint32 lamport_timestamp = 3;
-        uint32 edit_replica_id = 4;
-        uint32 edit_local_timestamp = 5;
-        uint32 count = 6;
+        repeated Range ranges = 4;
+        repeated VectorClockEntry version = 5;
+        repeated UndoCount counts = 6;
+    }
+
+    message UndoCount {
+        uint32 replica_id = 1;
+        uint32 local_timestamp = 2;
+        uint32 count = 3;
     }
 
     message UpdateSelections {
diff --git a/zed/src/editor/buffer.rs b/zed/src/editor/buffer.rs
index e601989396..d2e2705fb6 100644
--- a/zed/src/editor/buffer.rs
+++ b/zed/src/editor/buffer.rs
@@ -38,8 +38,6 @@ use std::{
     time::{Duration, Instant, SystemTime, UNIX_EPOCH},
 };
 
-const UNDO_GROUP_INTERVAL: Duration = Duration::from_millis(300);
-
 #[derive(Clone, Default)]
 struct DeterministicState;
 
@@ -145,17 +143,67 @@ struct SyntaxTree {
     version: time::Global,
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 struct Transaction {
     start: time::Global,
+    end: time::Global,
     buffer_was_dirty: bool,
     edits: Vec<time::Local>,
+    ranges: Vec<Range<usize>>,
     selections_before: Option<(SelectionSetId, Arc<[Selection]>)>,
     selections_after: Option<(SelectionSetId, Arc<[Selection]>)>,
     first_edit_at: Instant,
     last_edit_at: Instant,
 }
 
+impl Transaction {
+    fn push_edit(&mut self, edit: &EditOperation) {
+        self.edits.push(edit.timestamp.local());
+        self.end.observe(edit.timestamp.local());
+
+        let mut other_ranges = edit.ranges.iter().peekable();
+        let mut new_ranges: Vec<Range<usize>> = Vec::new();
+        let insertion_len = edit.new_text.as_ref().map_or(0, |t| t.len());
+        let mut delta = 0;
+
+        for mut self_range in self.ranges.iter().cloned() {
+            self_range.start += delta;
+            self_range.end += delta;
+
+            while let Some(other_range) = other_ranges.peek() {
+                let mut other_range = (*other_range).clone();
+                other_range.start += delta;
+                other_range.end += delta;
+
+                if other_range.start <= self_range.end {
+                    other_ranges.next().unwrap();
+                    delta += insertion_len;
+
+                    if other_range.end < self_range.start {
+                        new_ranges.push(other_range.start..other_range.end + insertion_len);
+                        self_range.start += insertion_len;
+                        self_range.end += insertion_len;
+                    } else {
+                        self_range.start = cmp::min(self_range.start, other_range.start);
+                        self_range.end = cmp::max(self_range.end, other_range.end) + insertion_len;
+                    }
+                } else {
+                    break;
+                }
+            }
+
+            new_ranges.push(self_range);
+        }
+
+        for other_range in other_ranges {
+            new_ranges.push(other_range.start + delta..other_range.end + delta + insertion_len);
+            delta += insertion_len;
+        }
+
+        self.ranges = new_ranges;
+    }
+}
+
 #[derive(Clone)]
 pub struct History {
     // TODO: Turn this into a String or Rope, maybe.
@@ -175,7 +223,7 @@ impl History {
             undo_stack: Vec::new(),
             redo_stack: Vec::new(),
             transaction_depth: 0,
-            group_interval: UNDO_GROUP_INTERVAL,
+            group_interval: Duration::from_millis(300),
         }
     }
 
@@ -193,9 +241,11 @@ impl History {
         self.transaction_depth += 1;
         if self.transaction_depth == 1 {
             self.undo_stack.push(Transaction {
-                start,
+                start: start.clone(),
+                end: start,
                 buffer_was_dirty,
                 edits: Vec::new(),
+                ranges: Vec::new(),
                 selections_before: selections,
                 selections_after: None,
                 first_edit_at: now,
@@ -226,12 +276,10 @@ impl History {
         let mut transactions = self.undo_stack.iter_mut();
 
         if let Some(mut transaction) = transactions.next_back() {
-            for prev_transaction in transactions.next_back() {
+            while let Some(prev_transaction) = transactions.next_back() {
                 if transaction.first_edit_at - prev_transaction.last_edit_at <= self.group_interval
+                    && transaction.start == prev_transaction.end
                 {
-                    prev_transaction.edits.append(&mut transaction.edits);
-                    prev_transaction.last_edit_at = transaction.last_edit_at;
-                    prev_transaction.selections_after = transaction.selections_after.take();
                     transaction = prev_transaction;
                     new_len -= 1;
                 } else {
@@ -240,12 +288,28 @@ impl History {
             }
         }
 
+        let (transactions_to_keep, transactions_to_merge) = self.undo_stack.split_at_mut(new_len);
+        if let Some(last_transaction) = transactions_to_keep.last_mut() {
+            for transaction in &*transactions_to_merge {
+                for edit_id in &transaction.edits {
+                    last_transaction.push_edit(&self.ops[edit_id]);
+                }
+            }
+
+            if let Some(transaction) = transactions_to_merge.last_mut() {
+                last_transaction.last_edit_at = transaction.last_edit_at;
+                last_transaction.selections_after = transaction.selections_after.take();
+                last_transaction.end = transaction.end.clone();
+            }
+        }
+
         self.undo_stack.truncate(new_len);
     }
 
     fn push_undo(&mut self, edit_id: time::Local) {
         assert_ne!(self.transaction_depth, 0);
-        self.undo_stack.last_mut().unwrap().edits.push(edit_id);
+        let last_transaction = self.undo_stack.last_mut().unwrap();
+        last_transaction.push_edit(&self.ops[&edit_id]);
     }
 
     fn pop_undo(&mut self) -> Option<&Transaction> {
@@ -270,11 +334,13 @@ impl History {
 }
 
 #[derive(Clone, Default, Debug)]
-struct UndoMap(HashMap<time::Local, Vec<UndoOperation>>);
+struct UndoMap(HashMap<time::Local, Vec<(time::Local, u32)>>);
 
 impl UndoMap {
-    fn insert(&mut self, undo: UndoOperation) {
-        self.0.entry(undo.edit_id).or_default().push(undo);
+    fn insert(&mut self, undo: &UndoOperation) {
+        for (edit_id, count) in &undo.counts {
+            self.0.entry(*edit_id).or_default().push((undo.id, *count));
+        }
     }
 
     fn is_undone(&self, edit_id: time::Local) -> bool {
@@ -287,8 +353,8 @@ impl UndoMap {
             .get(&edit_id)
             .unwrap_or(&Vec::new())
             .iter()
-            .filter(|undo| version.observed(undo.id))
-            .map(|undo| undo.count)
+            .filter(|(undo_id, _)| version.observed(*undo_id))
+            .map(|(_, undo_count)| *undo_count)
             .max()
             .unwrap_or(0);
         undo_count % 2 == 1
@@ -299,7 +365,7 @@ impl UndoMap {
             .get(&edit_id)
             .unwrap_or(&Vec::new())
             .iter()
-            .map(|undo| undo.count)
+            .map(|(_, undo_count)| *undo_count)
             .max()
             .unwrap_or(0)
     }
@@ -416,11 +482,12 @@ pub struct EditOperation {
     new_text: Option<String>,
 }
 
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub struct UndoOperation {
     id: time::Local,
-    edit_id: time::Local,
-    count: u32,
+    counts: HashMap<time::Local, u32>,
+    ranges: Vec<Range<usize>>,
+    version: time::Global,
 }
 
 impl Buffer {
@@ -1211,7 +1278,7 @@ impl Buffer {
                 lamport_timestamp,
             } => {
                 if !self.version.observed(undo.id) {
-                    self.apply_undo(undo)?;
+                    self.apply_undo(&undo)?;
                     self.version.observe(undo.id);
                     self.lamport_clock.observe(lamport_timestamp);
                 }
@@ -1276,7 +1343,7 @@ impl Buffer {
             old_fragments.slice(&VersionedOffset::Offset(ranges[0].start), Bias::Left, &cx);
         new_ropes.push_tree(new_fragments.summary().text);
 
-        let mut fragment_start = old_fragments.start().offset();
+        let mut fragment_start = old_fragments.sum_start().offset();
         for range in ranges {
             let fragment_end = old_fragments.end(&cx).offset();
 
@@ -1285,7 +1352,7 @@ impl Buffer {
             if fragment_end < range.start {
                 // If the current fragment has been partially consumed, then consume the rest of it
                 // and advance to the next fragment before slicing.
-                if fragment_start > old_fragments.start().offset() {
+                if fragment_start > old_fragments.sum_start().offset() {
                     if fragment_end > fragment_start {
                         let mut suffix = old_fragments.item().unwrap().clone();
                         suffix.len = fragment_end - fragment_start;
@@ -1299,7 +1366,7 @@ impl Buffer {
                     old_fragments.slice(&VersionedOffset::Offset(range.start), Bias::Left, &cx);
                 new_ropes.push_tree(slice.summary().text);
                 new_fragments.push_tree(slice, &None);
-                fragment_start = old_fragments.start().offset();
+                fragment_start = old_fragments.sum_start().offset();
             }
 
             // If we are at the end of a non-concurrent fragment, advance to the next one.
@@ -1310,7 +1377,7 @@ impl Buffer {
                 new_ropes.push_fragment(&fragment, fragment.visible);
                 new_fragments.push(fragment, &None);
                 old_fragments.next(&cx);
-                fragment_start = old_fragments.start().offset();
+                fragment_start = old_fragments.sum_start().offset();
             }
 
             // Skip over insertions that are concurrent to this edit, but have a lower lamport
@@ -1378,7 +1445,7 @@ impl Buffer {
 
         // If the current fragment has been partially consumed, then consume the rest of it
         // and advance to the next fragment before slicing.
-        if fragment_start > old_fragments.start().offset() {
+        if fragment_start > old_fragments.sum_start().offset() {
             let fragment_end = old_fragments.end(&cx).offset();
             if fragment_end > fragment_start {
                 let mut suffix = old_fragments.item().unwrap().clone();
@@ -1424,12 +1491,9 @@ impl Buffer {
         let was_dirty = self.is_dirty(cx.as_ref());
         let old_version = self.version.clone();
 
-        if let Some(transaction) = self.history.pop_undo() {
+        if let Some(transaction) = self.history.pop_undo().cloned() {
             let selections = transaction.selections_before.clone();
-            for edit_id in transaction.edits.clone() {
-                self.undo_or_redo(edit_id, cx).unwrap();
-            }
-
+            self.undo_or_redo(transaction, cx).unwrap();
             if let Some((set_id, selections)) = selections {
                 let _ = self.update_selection_set(set_id, selections, cx);
             }
@@ -1446,12 +1510,9 @@ impl Buffer {
         let was_dirty = self.is_dirty(cx.as_ref());
         let old_version = self.version.clone();
 
-        if let Some(transaction) = self.history.pop_redo() {
+        if let Some(transaction) = self.history.pop_redo().cloned() {
             let selections = transaction.selections_after.clone();
-            for edit_id in transaction.edits.clone() {
-                self.undo_or_redo(edit_id, cx).unwrap();
-            }
-
+            self.undo_or_redo(transaction, cx).unwrap();
             if let Some((set_id, selections)) = selections {
                 let _ = self.update_selection_set(set_id, selections, cx);
             }
@@ -1464,13 +1525,23 @@ impl Buffer {
         }
     }
 
-    fn undo_or_redo(&mut self, edit_id: time::Local, cx: &mut ModelContext<Self>) -> Result<()> {
+    fn undo_or_redo(
+        &mut self,
+        transaction: Transaction,
+        cx: &mut ModelContext<Self>,
+    ) -> Result<()> {
+        let mut counts = HashMap::default();
+        for edit_id in transaction.edits {
+            counts.insert(edit_id, self.undo_map.undo_count(edit_id) + 1);
+        }
+
         let undo = UndoOperation {
             id: self.local_clock.tick(),
-            edit_id,
-            count: self.undo_map.undo_count(edit_id) + 1,
+            counts,
+            ranges: transaction.ranges,
+            version: transaction.start.clone(),
         };
-        self.apply_undo(undo)?;
+        self.apply_undo(&undo)?;
         self.version.observe(undo.id);
 
         let operation = Operation::Undo {
@@ -1482,27 +1553,31 @@ impl Buffer {
         Ok(())
     }
 
-    fn apply_undo(&mut self, undo: UndoOperation) -> Result<()> {
+    fn apply_undo(&mut self, undo: &UndoOperation) -> Result<()> {
         self.undo_map.insert(undo);
-        let edit = &self.history.ops[&undo.edit_id];
-        let version = Some(edit.version.clone());
+
+        let mut cx = undo.version.clone();
+        for edit_id in undo.counts.keys().copied() {
+            cx.observe(edit_id);
+        }
+        let cx = Some(cx);
 
         let mut old_fragments = self.fragments.cursor::<VersionedOffset, VersionedOffset>();
-        old_fragments.seek(&VersionedOffset::Offset(0), Bias::Left, &version);
-
-        let mut new_fragments = SumTree::new();
+        let mut new_fragments = old_fragments.slice(
+            &VersionedOffset::Offset(undo.ranges[0].start),
+            Bias::Right,
+            &cx,
+        );
         let mut new_ropes =
             RopeBuilder::new(self.visible_text.cursor(0), self.deleted_text.cursor(0));
+        new_ropes.push_tree(new_fragments.summary().text);
 
-        for range in &edit.ranges {
-            let mut end_offset = old_fragments.end(&version).offset();
+        for range in &undo.ranges {
+            let mut end_offset = old_fragments.end(&cx).offset();
 
             if end_offset < range.start {
-                let preceding_fragments = old_fragments.slice(
-                    &VersionedOffset::Offset(range.start),
-                    Bias::Left,
-                    &version,
-                );
+                let preceding_fragments =
+                    old_fragments.slice(&VersionedOffset::Offset(range.start), Bias::Right, &cx);
                 new_ropes.push_tree(preceding_fragments.summary().text);
                 new_fragments.push_tree(preceding_fragments, &None);
             }
@@ -1511,8 +1586,9 @@ impl Buffer {
                 if let Some(fragment) = old_fragments.item() {
                     let mut fragment = fragment.clone();
                     let fragment_was_visible = fragment.visible;
-                    if fragment.was_visible(&edit.version, &self.undo_map)
-                        || fragment.timestamp.local() == edit.timestamp.local()
+
+                    if fragment.was_visible(&undo.version, &self.undo_map)
+                        || undo.counts.contains_key(&fragment.timestamp.local())
                     {
                         fragment.visible = fragment.is_visible(&self.undo_map);
                         fragment.max_undos.observe(undo.id);
@@ -1520,15 +1596,24 @@ impl Buffer {
                     new_ropes.push_fragment(&fragment, fragment_was_visible);
                     new_fragments.push(fragment, &None);
 
-                    old_fragments.next(&version);
-                    end_offset = old_fragments.end(&version).offset();
+                    old_fragments.next(&cx);
+                    if end_offset == old_fragments.end(&cx).offset() {
+                        let unseen_fragments = old_fragments.slice(
+                            &VersionedOffset::Offset(end_offset),
+                            Bias::Right,
+                            &cx,
+                        );
+                        new_ropes.push_tree(unseen_fragments.summary().text);
+                        new_fragments.push_tree(unseen_fragments, &None);
+                    }
+                    end_offset = old_fragments.end(&cx).offset();
                 } else {
                     break;
                 }
             }
         }
 
-        let suffix = old_fragments.suffix(&version);
+        let suffix = old_fragments.suffix(&cx);
         new_ropes.push_tree(suffix.summary().text);
         new_fragments.push_tree(suffix, &None);
 
@@ -1561,7 +1646,7 @@ impl Buffer {
         } else {
             match op {
                 Operation::Edit(edit) => self.version >= edit.version,
-                Operation::Undo { undo, .. } => self.version.observed(undo.edit_id),
+                Operation::Undo { undo, .. } => self.version >= undo.version,
                 Operation::UpdateSelections { selections, .. } => {
                     if let Some(selections) = selections {
                         selections.iter().all(|selection| {
@@ -1599,7 +1684,7 @@ impl Buffer {
         let mut new_fragments = old_fragments.slice(&ranges[0].start, Bias::Right, &None);
         new_ropes.push_tree(new_fragments.summary().text);
 
-        let mut fragment_start = old_fragments.start().visible;
+        let mut fragment_start = old_fragments.sum_start().visible;
         for range in ranges {
             let fragment_end = old_fragments.end(&None).visible;
 
@@ -1608,7 +1693,7 @@ impl Buffer {
             if fragment_end < range.start {
                 // If the current fragment has been partially consumed, then consume the rest of it
                 // and advance to the next fragment before slicing.
-                if fragment_start > old_fragments.start().visible {
+                if fragment_start > old_fragments.sum_start().visible {
                     if fragment_end > fragment_start {
                         let mut suffix = old_fragments.item().unwrap().clone();
                         suffix.len = fragment_end - fragment_start;
@@ -1621,10 +1706,10 @@ impl Buffer {
                 let slice = old_fragments.slice(&range.start, Bias::Right, &None);
                 new_ropes.push_tree(slice.summary().text);
                 new_fragments.push_tree(slice, &None);
-                fragment_start = old_fragments.start().visible;
+                fragment_start = old_fragments.sum_start().visible;
             }
 
-            let full_range_start = range.start + old_fragments.start().deleted;
+            let full_range_start = range.start + old_fragments.sum_start().deleted;
 
             // Preserve any portion of the current fragment that precedes this range.
             if fragment_start < range.start {
@@ -1672,13 +1757,13 @@ impl Buffer {
                 }
             }
 
-            let full_range_end = range.end + old_fragments.start().deleted;
+            let full_range_end = range.end + old_fragments.sum_start().deleted;
             edit.ranges.push(full_range_start..full_range_end);
         }
 
         // If the current fragment has been partially consumed, then consume the rest of it
         // and advance to the next fragment before slicing.
-        if fragment_start > old_fragments.start().visible {
+        if fragment_start > old_fragments.sum_start().visible {
             let fragment_end = old_fragments.end(&None).visible;
             if fragment_end > fragment_start {
                 let mut suffix = old_fragments.item().unwrap().clone();
@@ -1717,7 +1802,7 @@ impl Buffer {
         let mut cursor = self.fragments.cursor::<usize, FragmentTextSummary>();
         cursor.seek(&offset, bias, &None);
         Anchor {
-            offset: offset + cursor.start().deleted,
+            offset: offset + cursor.sum_start().deleted,
             bias,
             version: self.version(),
         }
@@ -1725,30 +1810,28 @@ impl Buffer {
 
     fn summary_for_anchor(&self, anchor: &Anchor) -> TextSummary {
         let cx = Some(anchor.version.clone());
-        let mut cursor = self
-            .fragments
-            .cursor::<VersionedOffset, (VersionedOffset, usize)>();
+        let mut cursor = self.fragments.cursor::<VersionedOffset, usize>();
         cursor.seek(&VersionedOffset::Offset(anchor.offset), anchor.bias, &cx);
         let overshoot = if cursor.item().map_or(false, |fragment| fragment.visible) {
-            anchor.offset - cursor.start().0.offset()
+            anchor.offset - cursor.seek_start().offset()
         } else {
             0
         };
-        self.text_summary_for_range(0..cursor.start().1 + overshoot)
+        self.text_summary_for_range(0..*cursor.sum_start() + overshoot)
     }
 
     fn full_offset_for_anchor(&self, anchor: &Anchor) -> usize {
         let cx = Some(anchor.version.clone());
         let mut cursor = self
             .fragments
-            .cursor::<VersionedOffset, (VersionedOffset, FragmentTextSummary)>();
+            .cursor::<VersionedOffset, FragmentTextSummary>();
         cursor.seek(&VersionedOffset::Offset(anchor.offset), anchor.bias, &cx);
         let overshoot = if cursor.item().is_some() {
-            anchor.offset - cursor.start().0.offset()
+            anchor.offset - cursor.seek_start().offset()
         } else {
             0
         };
-        let summary = cursor.start().1;
+        let summary = cursor.sum_start();
         summary.visible + summary.deleted + overshoot
     }
 
@@ -2286,9 +2369,24 @@ impl<'a> Into<proto::Operation> for &'a Operation {
                     replica_id: undo.id.replica_id as u32,
                     local_timestamp: undo.id.value,
                     lamport_timestamp: lamport_timestamp.value,
-                    edit_replica_id: undo.edit_id.replica_id as u32,
-                    edit_local_timestamp: undo.edit_id.value,
-                    count: undo.count,
+                    ranges: undo
+                        .ranges
+                        .iter()
+                        .map(|r| proto::Range {
+                            start: r.start as u64,
+                            end: r.end as u64,
+                        })
+                        .collect(),
+                    counts: undo
+                        .counts
+                        .iter()
+                        .map(|(edit_id, count)| proto::operation::UndoCount {
+                            replica_id: edit_id.replica_id as u32,
+                            local_timestamp: edit_id.value,
+                            count: *count,
+                        })
+                        .collect(),
+                    version: From::from(&undo.version),
                 }),
                 Operation::UpdateSelections {
                     set_id,
@@ -2329,14 +2427,6 @@ impl<'a> Into<proto::Operation> for &'a Operation {
 
 impl<'a> Into<proto::operation::Edit> for &'a EditOperation {
     fn into(self) -> proto::operation::Edit {
-        let version = self
-            .version
-            .iter()
-            .map(|entry| proto::VectorClockEntry {
-                replica_id: entry.replica_id as u32,
-                timestamp: entry.value,
-            })
-            .collect();
         let ranges = self
             .ranges
             .iter()
@@ -2349,7 +2439,7 @@ impl<'a> Into<proto::operation::Edit> for &'a EditOperation {
             replica_id: self.timestamp.replica_id as u32,
             local_timestamp: self.timestamp.local,
             lamport_timestamp: self.timestamp.lamport,
-            version,
+            version: From::from(&self.version),
             ranges,
             new_text: self.new_text.clone(),
         }
@@ -2396,11 +2486,25 @@ impl TryFrom<proto::Operation> for Operation {
                             replica_id: undo.replica_id as ReplicaId,
                             value: undo.local_timestamp,
                         },
-                        edit_id: time::Local {
-                            replica_id: undo.edit_replica_id as ReplicaId,
-                            value: undo.edit_local_timestamp,
-                        },
-                        count: undo.count,
+                        counts: undo
+                            .counts
+                            .into_iter()
+                            .map(|c| {
+                                (
+                                    time::Local {
+                                        replica_id: c.replica_id as ReplicaId,
+                                        value: c.local_timestamp,
+                                    },
+                                    c.count,
+                                )
+                            })
+                            .collect(),
+                        ranges: undo
+                            .ranges
+                            .into_iter()
+                            .map(|r| r.start as usize..r.end as usize)
+                            .collect(),
+                        version: undo.version.into(),
                     },
                 },
                 proto::operation::Variant::UpdateSelections(message) => {
@@ -2456,13 +2560,6 @@ impl TryFrom<proto::Operation> for Operation {
 
 impl From<proto::operation::Edit> for EditOperation {
     fn from(edit: proto::operation::Edit) -> Self {
-        let mut version = time::Global::new();
-        for entry in edit.version {
-            version.observe(time::Local {
-                replica_id: entry.replica_id as ReplicaId,
-                value: entry.timestamp,
-            });
-        }
         let ranges = edit
             .ranges
             .into_iter()
@@ -2474,7 +2571,7 @@ impl From<proto::operation::Edit> for EditOperation {
                 local: edit.local_timestamp,
                 lamport: edit.lamport_timestamp,
             },
-            version,
+            version: edit.version.into(),
             ranges,
             new_text: edit.new_text,
         }
@@ -2673,6 +2770,7 @@ mod tests {
                 .collect::<String>();
             cx.add_model(|cx| {
                 let mut buffer = Buffer::new(0, reference_string.as_str(), cx);
+                buffer.history.group_interval = Duration::from_millis(rng.gen_range(0..=200));
                 let mut buffer_versions = Vec::new();
                 log::info!(
                     "buffer text {:?}, version: {:?}",
@@ -2695,6 +2793,11 @@ mod tests {
                     if rng.gen_bool(0.25) {
                         buffer.randomly_undo_redo(rng, cx);
                         reference_string = buffer.text();
+                        log::info!(
+                            "buffer text {:?}, version: {:?}",
+                            buffer.text(),
+                            buffer.version()
+                        );
                     }
 
                     let range = buffer.random_byte_range(0, rng);
@@ -3258,35 +3361,36 @@ mod tests {
     fn test_undo_redo(cx: &mut gpui::MutableAppContext) {
         cx.add_model(|cx| {
             let mut buffer = Buffer::new(0, "1234", cx);
+            // Set group interval to zero so as to not group edits in the undo stack.
+            buffer.history.group_interval = Duration::from_secs(0);
 
             buffer.edit(vec![1..1], "abx", cx);
             buffer.edit(vec![3..4], "yzef", cx);
             buffer.edit(vec![3..5], "cd", cx);
             assert_eq!(buffer.text(), "1abcdef234");
 
-            let edit1 = buffer.operations[0].clone();
-            let edit2 = buffer.operations[1].clone();
-            let edit3 = buffer.operations[2].clone();
+            let transactions = buffer.history.undo_stack.clone();
+            assert_eq!(transactions.len(), 3);
 
-            buffer.undo_or_redo(edit1.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[0].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1cdef234");
-            buffer.undo_or_redo(edit1.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[0].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1abcdef234");
 
-            buffer.undo_or_redo(edit2.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[1].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1abcdx234");
-            buffer.undo_or_redo(edit3.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[2].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1abx234");
-            buffer.undo_or_redo(edit2.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[1].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1abyzef234");
-            buffer.undo_or_redo(edit3.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[2].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1abcdef234");
 
-            buffer.undo_or_redo(edit3.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[2].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1abyzef234");
-            buffer.undo_or_redo(edit1.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[0].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1yzef234");
-            buffer.undo_or_redo(edit2.edit_id().unwrap(), cx).unwrap();
+            buffer.undo_or_redo(transactions[1].clone(), cx).unwrap();
             assert_eq!(buffer.text(), "1234");
 
             buffer
@@ -3320,7 +3424,7 @@ mod tests {
             assert_eq!(buffer.text(), "12cde6");
             assert_eq!(buffer.selection_ranges(set_id).unwrap(), vec![1..3]);
 
-            now += UNDO_GROUP_INTERVAL + Duration::from_millis(1);
+            now += buffer.history.group_interval + Duration::from_millis(1);
             buffer.start_transaction_at(Some(set_id), now, cx).unwrap();
             buffer
                 .update_selection_set(
@@ -3432,8 +3536,11 @@ mod tests {
             let mut network = Network::new(StdRng::seed_from_u64(seed));
 
             for i in 0..peers {
-                let buffer = cx.add_model(|cx| Buffer::new(i as ReplicaId, base_text.as_str(), cx));
-
+                let buffer = cx.add_model(|cx| {
+                    let mut buf = Buffer::new(i as ReplicaId, base_text.as_str(), cx);
+                    buf.history.group_interval = Duration::from_millis(rng.gen_range(0..=200));
+                    buf
+                });
                 buffers.push(buffer);
                 replica_ids.push(i as u16);
                 network.add_peer(i as u16);
@@ -3761,9 +3868,13 @@ mod tests {
 
         pub fn randomly_undo_redo(&mut self, rng: &mut impl Rng, cx: &mut ModelContext<Self>) {
             for _ in 0..rng.gen_range(1..=5) {
-                if let Some(edit_id) = self.history.ops.keys().choose(rng).copied() {
-                    log::info!("undoing buffer {} operation {:?}", self.replica_id, edit_id);
-                    self.undo_or_redo(edit_id, cx).unwrap();
+                if let Some(transaction) = self.history.undo_stack.choose(rng).cloned() {
+                    log::info!(
+                        "undoing buffer {} transaction {:?}",
+                        self.replica_id,
+                        transaction
+                    );
+                    self.undo_or_redo(transaction, cx).unwrap();
                 }
             }
         }
@@ -3841,15 +3952,4 @@ mod tests {
             })
         }
     }
-
-    impl Operation {
-        fn edit_id(&self) -> Option<time::Local> {
-            match self {
-                Operation::Edit(edit) => Some(edit.timestamp.local()),
-                Operation::Undo { undo, .. } => Some(undo.edit_id),
-                Operation::UpdateSelections { .. } => None,
-                Operation::SetActiveSelections { .. } => None,
-            }
-        }
-    }
 }
diff --git a/zed/src/editor/buffer/rope.rs b/zed/src/editor/buffer/rope.rs
index 268924c158..4c1a3ed56d 100644
--- a/zed/src/editor/buffer/rope.rs
+++ b/zed/src/editor/buffer/rope.rs
@@ -128,10 +128,10 @@ impl Rope {
 
     pub fn to_point(&self, offset: usize) -> Point {
         assert!(offset <= self.summary().bytes);
-        let mut cursor = self.chunks.cursor::<usize, TextSummary>();
+        let mut cursor = self.chunks.cursor::<usize, Point>();
         cursor.seek(&offset, Bias::Left, &());
-        let overshoot = offset - cursor.start().bytes;
-        cursor.start().lines
+        let overshoot = offset - cursor.seek_start();
+        *cursor.sum_start()
             + cursor
                 .item()
                 .map_or(Point::zero(), |chunk| chunk.to_point(overshoot))
@@ -139,17 +139,17 @@ impl Rope {
 
     pub fn to_offset(&self, point: Point) -> usize {
         assert!(point <= self.summary().lines);
-        let mut cursor = self.chunks.cursor::<Point, TextSummary>();
+        let mut cursor = self.chunks.cursor::<Point, usize>();
         cursor.seek(&point, Bias::Left, &());
-        let overshoot = point - cursor.start().lines;
-        cursor.start().bytes + cursor.item().map_or(0, |chunk| chunk.to_offset(overshoot))
+        let overshoot = point - cursor.seek_start();
+        cursor.sum_start() + cursor.item().map_or(0, |chunk| chunk.to_offset(overshoot))
     }
 
     pub fn clip_offset(&self, mut offset: usize, bias: Bias) -> usize {
-        let mut cursor = self.chunks.cursor::<usize, usize>();
+        let mut cursor = self.chunks.cursor::<usize, ()>();
         cursor.seek(&offset, Bias::Left, &());
         if let Some(chunk) = cursor.item() {
-            let mut ix = offset - cursor.start();
+            let mut ix = offset - cursor.seek_start();
             while !chunk.0.is_char_boundary(ix) {
                 match bias {
                     Bias::Left => {
@@ -169,11 +169,11 @@ impl Rope {
     }
 
     pub fn clip_point(&self, point: Point, bias: Bias) -> Point {
-        let mut cursor = self.chunks.cursor::<Point, Point>();
+        let mut cursor = self.chunks.cursor::<Point, ()>();
         cursor.seek(&point, Bias::Right, &());
         if let Some(chunk) = cursor.item() {
-            let overshoot = point - cursor.start();
-            *cursor.start() + chunk.clip_point(overshoot, bias)
+            let overshoot = point - cursor.seek_start();
+            *cursor.seek_start() + chunk.clip_point(overshoot, bias)
         } else {
             self.summary().lines
         }
@@ -190,7 +190,7 @@ impl<'a> From<&'a str> for Rope {
 
 pub struct Cursor<'a> {
     rope: &'a Rope,
-    chunks: sum_tree::Cursor<'a, Chunk, usize, usize>,
+    chunks: sum_tree::Cursor<'a, Chunk, usize, ()>,
     offset: usize,
 }
 
@@ -222,18 +222,18 @@ impl<'a> Cursor<'a> {
 
         let mut slice = Rope::new();
         if let Some(start_chunk) = self.chunks.item() {
-            let start_ix = self.offset - self.chunks.start();
-            let end_ix = cmp::min(end_offset, self.chunks.end(&())) - self.chunks.start();
+            let start_ix = self.offset - self.chunks.seek_start();
+            let end_ix = cmp::min(end_offset, self.chunks.seek_end(&())) - self.chunks.seek_start();
             slice.push(&start_chunk.0[start_ix..end_ix]);
         }
 
-        if end_offset > self.chunks.end(&()) {
+        if end_offset > self.chunks.seek_end(&()) {
             self.chunks.next(&());
             slice.append(Rope {
                 chunks: self.chunks.slice(&end_offset, Bias::Right, &()),
             });
             if let Some(end_chunk) = self.chunks.item() {
-                let end_ix = end_offset - self.chunks.start();
+                let end_ix = end_offset - self.chunks.seek_start();
                 slice.push(&end_chunk.0[..end_ix]);
             }
         }
@@ -247,16 +247,16 @@ impl<'a> Cursor<'a> {
 
         let mut summary = TextSummary::default();
         if let Some(start_chunk) = self.chunks.item() {
-            let start_ix = self.offset - self.chunks.start();
-            let end_ix = cmp::min(end_offset, self.chunks.end(&())) - self.chunks.start();
+            let start_ix = self.offset - self.chunks.seek_start();
+            let end_ix = cmp::min(end_offset, self.chunks.seek_end(&())) - self.chunks.seek_start();
             summary = TextSummary::from(&start_chunk.0[start_ix..end_ix]);
         }
 
-        if end_offset > self.chunks.end(&()) {
+        if end_offset > self.chunks.seek_end(&()) {
             self.chunks.next(&());
             summary += &self.chunks.summary(&end_offset, Bias::Right, &());
             if let Some(end_chunk) = self.chunks.item() {
-                let end_ix = end_offset - self.chunks.start();
+                let end_ix = end_offset - self.chunks.seek_start();
                 summary += TextSummary::from(&end_chunk.0[..end_ix]);
             }
         }
@@ -274,7 +274,7 @@ impl<'a> Cursor<'a> {
 }
 
 pub struct Chunks<'a> {
-    chunks: sum_tree::Cursor<'a, Chunk, usize, usize>,
+    chunks: sum_tree::Cursor<'a, Chunk, usize, ()>,
     range: Range<usize>,
 }
 
@@ -286,11 +286,11 @@ impl<'a> Chunks<'a> {
     }
 
     pub fn offset(&self) -> usize {
-        self.range.start.max(*self.chunks.start())
+        self.range.start.max(*self.chunks.seek_start())
     }
 
     pub fn seek(&mut self, offset: usize) {
-        if offset >= self.chunks.end(&()) {
+        if offset >= self.chunks.seek_end(&()) {
             self.chunks.seek_forward(&offset, Bias::Right, &());
         } else {
             self.chunks.seek(&offset, Bias::Right, &());
@@ -300,10 +300,10 @@ impl<'a> Chunks<'a> {
 
     pub fn peek(&self) -> Option<&'a str> {
         if let Some(chunk) = self.chunks.item() {
-            let offset = *self.chunks.start();
+            let offset = *self.chunks.seek_start();
             if self.range.end > offset {
-                let start = self.range.start.saturating_sub(*self.chunks.start());
-                let end = self.range.end - self.chunks.start();
+                let start = self.range.start.saturating_sub(*self.chunks.seek_start());
+                let end = self.range.end - self.chunks.seek_start();
                 return Some(&chunk.0[start..chunk.0.len().min(end)]);
             }
         }
diff --git a/zed/src/editor/display_map/fold_map.rs b/zed/src/editor/display_map/fold_map.rs
index 8e94bf1eb2..227553a1b6 100644
--- a/zed/src/editor/display_map/fold_map.rs
+++ b/zed/src/editor/display_map/fold_map.rs
@@ -210,20 +210,20 @@ impl FoldMap {
         let buffer = self.buffer.read(cx);
         let offset = offset.to_offset(buffer);
         let transforms = self.sync(cx);
-        let mut cursor = transforms.cursor::<usize, usize>();
+        let mut cursor = transforms.cursor::<usize, ()>();
         cursor.seek(&offset, Bias::Right, &());
         cursor.item().map_or(false, |t| t.display_text.is_some())
     }
 
     pub fn is_line_folded(&self, display_row: u32, cx: &AppContext) -> bool {
         let transforms = self.sync(cx);
-        let mut cursor = transforms.cursor::<DisplayPoint, DisplayPoint>();
+        let mut cursor = transforms.cursor::<DisplayPoint, ()>();
         cursor.seek(&DisplayPoint::new(display_row, 0), Bias::Right, &());
         while let Some(transform) = cursor.item() {
             if transform.display_text.is_some() {
                 return true;
             }
-            if cursor.end(&()).row() == display_row {
+            if cursor.seek_end(&()).row() == display_row {
                 cursor.next(&())
             } else {
                 break;
@@ -242,20 +242,20 @@ impl FoldMap {
 
     pub fn to_buffer_point(&self, display_point: DisplayPoint, cx: &AppContext) -> Point {
         let transforms = self.sync(cx);
-        let mut cursor = transforms.cursor::<DisplayPoint, TransformSummary>();
+        let mut cursor = transforms.cursor::<DisplayPoint, Point>();
         cursor.seek(&display_point, Bias::Right, &());
-        let overshoot = display_point.0 - cursor.start().display.lines;
-        cursor.start().buffer.lines + overshoot
+        let overshoot = display_point.0 - cursor.seek_start().0;
+        *cursor.sum_start() + overshoot
     }
 
     pub fn to_display_point(&self, point: Point, cx: &AppContext) -> DisplayPoint {
         let transforms = self.sync(cx);
-        let mut cursor = transforms.cursor::<Point, TransformSummary>();
+        let mut cursor = transforms.cursor::<Point, DisplayPoint>();
         cursor.seek(&point, Bias::Right, &());
-        let overshoot = point - cursor.start().buffer.lines;
+        let overshoot = point - cursor.seek_start();
         DisplayPoint(cmp::min(
-            cursor.start().display.lines + overshoot,
-            cursor.end(&()).display.lines,
+            cursor.sum_start().0 + overshoot,
+            cursor.end(&()).0,
         ))
     }
 
@@ -275,20 +275,20 @@ impl FoldMap {
 
         let mut new_transforms = SumTree::new();
         let mut transforms = self.transforms.lock();
-        let mut cursor = transforms.cursor::<usize, usize>();
+        let mut cursor = transforms.cursor::<usize, ()>();
         cursor.seek(&0, Bias::Right, &());
 
         while let Some(mut edit) = edits.next() {
             new_transforms.push_tree(cursor.slice(&edit.old_range.start, Bias::Left, &()), &());
-            edit.new_range.start -= edit.old_range.start - cursor.start();
-            edit.old_range.start = *cursor.start();
+            edit.new_range.start -= edit.old_range.start - cursor.seek_start();
+            edit.old_range.start = *cursor.seek_start();
 
             cursor.seek(&edit.old_range.end, Bias::Right, &());
             cursor.next(&());
 
             let mut delta = edit.delta();
             loop {
-                edit.old_range.end = *cursor.start();
+                edit.old_range.end = *cursor.seek_start();
 
                 if let Some(next_edit) = edits.peek() {
                     if next_edit.old_range.start > edit.old_range.end {
@@ -443,10 +443,10 @@ impl FoldMapSnapshot {
     }
 
     pub fn chunks_at(&self, offset: DisplayOffset) -> Chunks {
-        let mut transform_cursor = self.transforms.cursor::<DisplayOffset, TransformSummary>();
+        let mut transform_cursor = self.transforms.cursor::<DisplayOffset, usize>();
         transform_cursor.seek(&offset, Bias::Right, &());
-        let overshoot = offset.0 - transform_cursor.start().display.bytes;
-        let buffer_offset = transform_cursor.start().buffer.bytes + overshoot;
+        let overshoot = offset.0 - transform_cursor.seek_start().0;
+        let buffer_offset = transform_cursor.sum_start() + overshoot;
         Chunks {
             transform_cursor,
             buffer_offset,
@@ -455,15 +455,15 @@ impl FoldMapSnapshot {
     }
 
     pub fn highlighted_chunks(&mut self, range: Range<DisplayOffset>) -> HighlightedChunks {
-        let mut transform_cursor = self.transforms.cursor::<DisplayOffset, TransformSummary>();
+        let mut transform_cursor = self.transforms.cursor::<DisplayOffset, usize>();
 
         transform_cursor.seek(&range.end, Bias::Right, &());
-        let overshoot = range.end.0 - transform_cursor.start().display.bytes;
-        let buffer_end = transform_cursor.start().buffer.bytes + overshoot;
+        let overshoot = range.end.0 - transform_cursor.seek_start().0;
+        let buffer_end = transform_cursor.sum_start() + overshoot;
 
         transform_cursor.seek(&range.start, Bias::Right, &());
-        let overshoot = range.start.0 - transform_cursor.start().display.bytes;
-        let buffer_start = transform_cursor.start().buffer.bytes + overshoot;
+        let overshoot = range.start.0 - transform_cursor.seek_start().0;
+        let buffer_start = transform_cursor.sum_start() + overshoot;
 
         HighlightedChunks {
             transform_cursor,
@@ -483,42 +483,41 @@ impl FoldMapSnapshot {
     pub fn to_display_offset(&self, point: DisplayPoint) -> DisplayOffset {
         let mut cursor = self.transforms.cursor::<DisplayPoint, TransformSummary>();
         cursor.seek(&point, Bias::Right, &());
-        let overshoot = point.0 - cursor.start().display.lines;
-        let mut offset = cursor.start().display.bytes;
+        let overshoot = point.0 - cursor.sum_start().display.lines;
+        let mut offset = cursor.sum_start().display.bytes;
         if !overshoot.is_zero() {
             let transform = cursor.item().expect("display point out of range");
             assert!(transform.display_text.is_none());
             let end_buffer_offset = self
                 .buffer
-                .to_offset(cursor.start().buffer.lines + overshoot);
-            offset += end_buffer_offset - cursor.start().buffer.bytes;
+                .to_offset(cursor.sum_start().buffer.lines + overshoot);
+            offset += end_buffer_offset - cursor.sum_start().buffer.bytes;
         }
         DisplayOffset(offset)
     }
 
     pub fn to_buffer_offset(&self, point: DisplayPoint) -> usize {
-        let mut cursor = self.transforms.cursor::<DisplayPoint, TransformSummary>();
+        let mut cursor = self.transforms.cursor::<DisplayPoint, Point>();
         cursor.seek(&point, Bias::Right, &());
-        let overshoot = point.0 - cursor.start().display.lines;
-        self.buffer
-            .to_offset(cursor.start().buffer.lines + overshoot)
+        let overshoot = point.0 - cursor.seek_start().0;
+        self.buffer.to_offset(*cursor.sum_start() + overshoot)
     }
 
     #[cfg(test)]
     pub fn clip_offset(&self, offset: DisplayOffset, bias: Bias) -> DisplayOffset {
-        let mut cursor = self.transforms.cursor::<DisplayOffset, TransformSummary>();
+        let mut cursor = self.transforms.cursor::<DisplayOffset, usize>();
         cursor.seek(&offset, Bias::Right, &());
         if let Some(transform) = cursor.item() {
-            let transform_start = cursor.start().display.bytes;
+            let transform_start = cursor.seek_start().0;
             if transform.display_text.is_some() {
                 if offset.0 == transform_start || matches!(bias, Bias::Left) {
                     DisplayOffset(transform_start)
                 } else {
-                    DisplayOffset(cursor.end(&()).display.bytes)
+                    DisplayOffset(cursor.seek_end(&()).0)
                 }
             } else {
                 let overshoot = offset.0 - transform_start;
-                let buffer_offset = cursor.start().buffer.bytes + overshoot;
+                let buffer_offset = cursor.sum_start() + overshoot;
                 let clipped_buffer_offset = self.buffer.clip_offset(buffer_offset, bias);
                 DisplayOffset(
                     (offset.0 as isize + (clipped_buffer_offset as isize - buffer_offset as isize))
@@ -531,19 +530,19 @@ impl FoldMapSnapshot {
     }
 
     pub fn clip_point(&self, point: DisplayPoint, bias: Bias) -> DisplayPoint {
-        let mut cursor = self.transforms.cursor::<DisplayPoint, TransformSummary>();
+        let mut cursor = self.transforms.cursor::<DisplayPoint, Point>();
         cursor.seek(&point, Bias::Right, &());
         if let Some(transform) = cursor.item() {
-            let transform_start = cursor.start().display.lines;
+            let transform_start = cursor.seek_start().0;
             if transform.display_text.is_some() {
                 if point.0 == transform_start || matches!(bias, Bias::Left) {
                     DisplayPoint(transform_start)
                 } else {
-                    DisplayPoint(cursor.end(&()).display.lines)
+                    DisplayPoint(cursor.seek_end(&()).0)
                 }
             } else {
                 let overshoot = point.0 - transform_start;
-                let buffer_position = cursor.start().buffer.lines + overshoot;
+                let buffer_position = *cursor.sum_start() + overshoot;
                 let clipped_buffer_position = self.buffer.clip_point(buffer_position, bias);
                 DisplayPoint::new(
                     point.row(),
@@ -681,7 +680,7 @@ impl<'a> sum_tree::Dimension<'a, FoldSummary> for usize {
 }
 
 pub struct BufferRows<'a> {
-    cursor: Cursor<'a, Transform, DisplayPoint, TransformSummary>,
+    cursor: Cursor<'a, Transform, DisplayPoint, Point>,
     display_point: Point,
 }
 
@@ -689,7 +688,7 @@ impl<'a> Iterator for BufferRows<'a> {
     type Item = u32;
 
     fn next(&mut self) -> Option<Self::Item> {
-        while self.display_point > self.cursor.end(&()).display.lines {
+        while self.display_point > self.cursor.seek_end(&()).0 {
             self.cursor.next(&());
             if self.cursor.item().is_none() {
                 // TODO: Return a bool from next?
@@ -698,8 +697,8 @@ impl<'a> Iterator for BufferRows<'a> {
         }
 
         if self.cursor.item().is_some() {
-            let overshoot = self.display_point - self.cursor.start().display.lines;
-            let buffer_point = self.cursor.start().buffer.lines + overshoot;
+            let overshoot = self.display_point - self.cursor.seek_start().0;
+            let buffer_point = *self.cursor.sum_start() + overshoot;
             self.display_point.row += 1;
             Some(buffer_point.row)
         } else {
@@ -709,7 +708,7 @@ impl<'a> Iterator for BufferRows<'a> {
 }
 
 pub struct Chunks<'a> {
-    transform_cursor: Cursor<'a, Transform, DisplayOffset, TransformSummary>,
+    transform_cursor: Cursor<'a, Transform, DisplayOffset, usize>,
     buffer_chunks: buffer::Chunks<'a>,
     buffer_offset: usize,
 }
@@ -730,7 +729,7 @@ impl<'a> Iterator for Chunks<'a> {
             self.buffer_offset += transform.summary.buffer.bytes;
             self.buffer_chunks.seek(self.buffer_offset);
 
-            while self.buffer_offset >= self.transform_cursor.end(&()).buffer.bytes
+            while self.buffer_offset >= self.transform_cursor.end(&())
                 && self.transform_cursor.item().is_some()
             {
                 self.transform_cursor.next(&());
@@ -745,7 +744,7 @@ impl<'a> Iterator for Chunks<'a> {
             chunk = &chunk[offset_in_chunk..];
 
             // Truncate the chunk so that it ends at the next fold.
-            let region_end = self.transform_cursor.end(&()).buffer.bytes - self.buffer_offset;
+            let region_end = self.transform_cursor.end(&()) - self.buffer_offset;
             if chunk.len() >= region_end {
                 chunk = &chunk[0..region_end];
                 self.transform_cursor.next(&());
@@ -762,7 +761,7 @@ impl<'a> Iterator for Chunks<'a> {
 }
 
 pub struct HighlightedChunks<'a> {
-    transform_cursor: Cursor<'a, Transform, DisplayOffset, TransformSummary>,
+    transform_cursor: Cursor<'a, Transform, DisplayOffset, usize>,
     buffer_chunks: buffer::HighlightedChunks<'a>,
     buffer_chunk: Option<(usize, &'a str, StyleId)>,
     buffer_offset: usize,
@@ -785,7 +784,7 @@ impl<'a> Iterator for HighlightedChunks<'a> {
             self.buffer_offset += transform.summary.buffer.bytes;
             self.buffer_chunks.seek(self.buffer_offset);
 
-            while self.buffer_offset >= self.transform_cursor.end(&()).buffer.bytes
+            while self.buffer_offset >= self.transform_cursor.end(&())
                 && self.transform_cursor.item().is_some()
             {
                 self.transform_cursor.next(&());
@@ -809,7 +808,7 @@ impl<'a> Iterator for HighlightedChunks<'a> {
             chunk = &chunk[offset_in_chunk..];
 
             // Truncate the chunk so that it ends at the next fold.
-            let region_end = self.transform_cursor.end(&()).buffer.bytes - self.buffer_offset;
+            let region_end = self.transform_cursor.end(&()) - self.buffer_offset;
             if chunk.len() >= region_end {
                 chunk = &chunk[0..region_end];
                 self.transform_cursor.next(&());
diff --git a/zed/src/file_finder.rs b/zed/src/file_finder.rs
index 060fd3be50..66d99fc542 100644
--- a/zed/src/file_finder.rs
+++ b/zed/src/file_finder.rs
@@ -655,7 +655,7 @@ mod tests {
         finder.read_with(&cx, |f, _| assert_eq!(f.matches.len(), 0));
     }
 
-    #[gpui::test]
+    #[gpui::test(retries = 5)]
     async fn test_multiple_matches_with_same_relative_path(mut cx: gpui::TestAppContext) {
         let tmp_dir = temp_tree(json!({
             "dir1": { "a.txt": "" },
diff --git a/zed/src/menus.rs b/zed/src/menus.rs
index 438071c2de..9f22c8ede9 100644
--- a/zed/src/menus.rs
+++ b/zed/src/menus.rs
@@ -41,7 +41,7 @@ pub fn menus(state: AppState) -> Vec<Menu<'static>> {
                     name: "New",
                     keystroke: Some("cmd-n"),
                     action: "workspace:new_file",
-                    arg: None,
+                    arg: Some(Box::new(state.clone())),
                 },
                 MenuItem::Separator,
                 MenuItem::Action {
diff --git a/zed/src/sum_tree.rs b/zed/src/sum_tree.rs
index 808f572450..3e6c30a6f5 100644
--- a/zed/src/sum_tree.rs
+++ b/zed/src/sum_tree.rs
@@ -37,18 +37,6 @@ impl<'a, T: Summary> Dimension<'a, T> for () {
     fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
 }
 
-impl<'a, S, D1, D2> Dimension<'a, S> for (D1, D2)
-where
-    S: Summary,
-    D1: Dimension<'a, S>,
-    D2: Dimension<'a, S>,
-{
-    fn add_summary(&mut self, summary: &'a S, cx: &S::Context) {
-        self.0.add_summary(summary, cx);
-        self.1.add_summary(summary, cx);
-    }
-}
-
 pub trait SeekDimension<'a, T: Summary>: Dimension<'a, T> {
     fn cmp(&self, other: &Self, cx: &T::Context) -> Ordering;
 }
@@ -671,7 +659,7 @@ mod tests {
                 cursor.seek(&Count(pos), Bias::Right, &());
 
                 for i in 0..10 {
-                    assert_eq!(cursor.start().0, pos);
+                    assert_eq!(cursor.sum_start().0, pos);
 
                     if pos > 0 {
                         assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
@@ -730,7 +718,7 @@ mod tests {
         );
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), None);
-        assert_eq!(cursor.start(), &Sum(0));
+        assert_eq!(cursor.sum_start(), &Sum(0));
 
         // Single-element tree
         let mut tree = SumTree::<u8>::new();
@@ -742,23 +730,23 @@ mod tests {
         );
         assert_eq!(cursor.item(), Some(&1));
         assert_eq!(cursor.prev_item(), None);
-        assert_eq!(cursor.start(), &Sum(0));
+        assert_eq!(cursor.sum_start(), &Sum(0));
 
         cursor.next(&());
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), Some(&1));
-        assert_eq!(cursor.start(), &Sum(1));
+        assert_eq!(cursor.sum_start(), &Sum(1));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), Some(&1));
         assert_eq!(cursor.prev_item(), None);
-        assert_eq!(cursor.start(), &Sum(0));
+        assert_eq!(cursor.sum_start(), &Sum(0));
 
         let mut cursor = tree.cursor::<Count, Sum>();
         assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), Some(&1));
-        assert_eq!(cursor.start(), &Sum(1));
+        assert_eq!(cursor.sum_start(), &Sum(1));
 
         cursor.seek(&Count(0), Bias::Right, &());
         assert_eq!(
@@ -769,7 +757,7 @@ mod tests {
         );
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), Some(&1));
-        assert_eq!(cursor.start(), &Sum(1));
+        assert_eq!(cursor.sum_start(), &Sum(1));
 
         // Multiple-element tree
         let mut tree = SumTree::new();
@@ -779,68 +767,68 @@ mod tests {
         assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
         assert_eq!(cursor.item(), Some(&3));
         assert_eq!(cursor.prev_item(), Some(&2));
-        assert_eq!(cursor.start(), &Sum(3));
+        assert_eq!(cursor.sum_start(), &Sum(3));
 
         cursor.next(&());
         assert_eq!(cursor.item(), Some(&4));
         assert_eq!(cursor.prev_item(), Some(&3));
-        assert_eq!(cursor.start(), &Sum(6));
+        assert_eq!(cursor.sum_start(), &Sum(6));
 
         cursor.next(&());
         assert_eq!(cursor.item(), Some(&5));
         assert_eq!(cursor.prev_item(), Some(&4));
-        assert_eq!(cursor.start(), &Sum(10));
+        assert_eq!(cursor.sum_start(), &Sum(10));
 
         cursor.next(&());
         assert_eq!(cursor.item(), Some(&6));
         assert_eq!(cursor.prev_item(), Some(&5));
-        assert_eq!(cursor.start(), &Sum(15));
+        assert_eq!(cursor.sum_start(), &Sum(15));
 
         cursor.next(&());
         cursor.next(&());
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), Some(&6));
-        assert_eq!(cursor.start(), &Sum(21));
+        assert_eq!(cursor.sum_start(), &Sum(21));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), Some(&6));
         assert_eq!(cursor.prev_item(), Some(&5));
-        assert_eq!(cursor.start(), &Sum(15));
+        assert_eq!(cursor.sum_start(), &Sum(15));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), Some(&5));
         assert_eq!(cursor.prev_item(), Some(&4));
-        assert_eq!(cursor.start(), &Sum(10));
+        assert_eq!(cursor.sum_start(), &Sum(10));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), Some(&4));
         assert_eq!(cursor.prev_item(), Some(&3));
-        assert_eq!(cursor.start(), &Sum(6));
+        assert_eq!(cursor.sum_start(), &Sum(6));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), Some(&3));
         assert_eq!(cursor.prev_item(), Some(&2));
-        assert_eq!(cursor.start(), &Sum(3));
+        assert_eq!(cursor.sum_start(), &Sum(3));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), Some(&2));
         assert_eq!(cursor.prev_item(), Some(&1));
-        assert_eq!(cursor.start(), &Sum(1));
+        assert_eq!(cursor.sum_start(), &Sum(1));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), Some(&1));
         assert_eq!(cursor.prev_item(), None);
-        assert_eq!(cursor.start(), &Sum(0));
+        assert_eq!(cursor.sum_start(), &Sum(0));
 
         cursor.prev(&());
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), None);
-        assert_eq!(cursor.start(), &Sum(0));
+        assert_eq!(cursor.sum_start(), &Sum(0));
 
         cursor.next(&());
         assert_eq!(cursor.item(), Some(&1));
         assert_eq!(cursor.prev_item(), None);
-        assert_eq!(cursor.start(), &Sum(0));
+        assert_eq!(cursor.sum_start(), &Sum(0));
 
         let mut cursor = tree.cursor::<Count, Sum>();
         assert_eq!(
@@ -851,7 +839,7 @@ mod tests {
         );
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), Some(&6));
-        assert_eq!(cursor.start(), &Sum(21));
+        assert_eq!(cursor.sum_start(), &Sum(21));
 
         cursor.seek(&Count(3), Bias::Right, &());
         assert_eq!(
@@ -862,7 +850,7 @@ mod tests {
         );
         assert_eq!(cursor.item(), None);
         assert_eq!(cursor.prev_item(), Some(&6));
-        assert_eq!(cursor.start(), &Sum(21));
+        assert_eq!(cursor.sum_start(), &Sum(21));
 
         // Seeking can bias left or right
         cursor.seek(&Count(1), Bias::Left, &());
diff --git a/zed/src/sum_tree/cursor.rs b/zed/src/sum_tree/cursor.rs
index 8374546a20..c4cc68e778 100644
--- a/zed/src/sum_tree/cursor.rs
+++ b/zed/src/sum_tree/cursor.rs
@@ -45,17 +45,31 @@ where
         self.sum_dimension = U::default();
     }
 
-    pub fn start(&self) -> &U {
+    pub fn seek_start(&self) -> &S {
+        &self.seek_dimension
+    }
+
+    pub fn seek_end(&self, cx: &<T::Summary as Summary>::Context) -> S {
+        if let Some(item_summary) = self.item_summary() {
+            let mut end = self.seek_start().clone();
+            end.add_summary(item_summary, cx);
+            end
+        } else {
+            self.seek_start().clone()
+        }
+    }
+
+    pub fn sum_start(&self) -> &U {
         &self.sum_dimension
     }
 
     pub fn end(&self, cx: &<T::Summary as Summary>::Context) -> U {
         if let Some(item_summary) = self.item_summary() {
-            let mut end = self.start().clone();
+            let mut end = self.sum_start().clone();
             end.add_summary(item_summary, cx);
             end
         } else {
-            self.start().clone()
+            self.sum_start().clone()
         }
     }
 
@@ -613,7 +627,7 @@ where
     }
 
     pub fn start(&self) -> &U {
-        self.cursor.start()
+        self.cursor.sum_start()
     }
 
     pub fn item(&self) -> Option<&'a T> {
diff --git a/zed/src/time.rs b/zed/src/time.rs
index 00f4e54c18..8b665e8814 100644
--- a/zed/src/time.rs
+++ b/zed/src/time.rs
@@ -61,6 +61,31 @@ impl<'a> AddAssign<&'a Local> for Local {
 #[derive(Clone, Default, Hash, Eq, PartialEq)]
 pub struct Global(SmallVec<[Local; 3]>);
 
+impl From<Vec<zed_rpc::proto::VectorClockEntry>> for Global {
+    fn from(message: Vec<zed_rpc::proto::VectorClockEntry>) -> Self {
+        let mut version = Self::new();
+        for entry in message {
+            version.observe(Local {
+                replica_id: entry.replica_id as ReplicaId,
+                value: entry.timestamp,
+            });
+        }
+        version
+    }
+}
+
+impl<'a> From<&'a Global> for Vec<zed_rpc::proto::VectorClockEntry> {
+    fn from(version: &'a Global) -> Self {
+        version
+            .iter()
+            .map(|entry| zed_rpc::proto::VectorClockEntry {
+                replica_id: entry.replica_id as u32,
+                timestamp: entry.value,
+            })
+            .collect()
+    }
+}
+
 impl Global {
     pub fn new() -> Self {
         Self::default()
diff --git a/zed/src/workspace.rs b/zed/src/workspace.rs
index 9b74023ef1..9d86a7288c 100644
--- a/zed/src/workspace.rs
+++ b/zed/src/workspace.rs
@@ -30,6 +30,7 @@ use std::{
 pub fn init(cx: &mut MutableAppContext) {
     cx.add_global_action("workspace:open", open);
     cx.add_global_action("workspace:open_paths", open_paths);
+    cx.add_global_action("workspace:new_file", open_new);
     cx.add_action("workspace:save", Workspace::save_active_item);
     cx.add_action("workspace:debug_elements", Workspace::debug_elements);
     cx.add_action("workspace:new_file", Workspace::open_new_file);
@@ -100,6 +101,19 @@ fn open_paths(params: &OpenParams, cx: &mut MutableAppContext) {
     });
 }
 
+fn open_new(app_state: &AppState, cx: &mut MutableAppContext) {
+    cx.add_window(|cx| {
+        let mut view = Workspace::new(
+            app_state.settings.clone(),
+            app_state.language_registry.clone(),
+            app_state.rpc.clone(),
+            cx,
+        );
+        view.open_new_file(&app_state, cx);
+        view
+    });
+}
+
 pub trait Item: Entity + Sized {
     type View: ItemView;
 
@@ -479,7 +493,7 @@ impl Workspace {
         }
     }
 
-    pub fn open_new_file(&mut self, _: &(), cx: &mut ViewContext<Self>) {
+    pub fn open_new_file(&mut self, _: &AppState, cx: &mut ViewContext<Self>) {
         let buffer = cx.add_model(|cx| Buffer::new(0, "", cx));
         let buffer_view =
             cx.add_view(|cx| Editor::for_buffer(buffer.clone(), self.settings.clone(), cx));
@@ -1173,9 +1187,9 @@ mod tests {
         let app_state = cx.read(build_app_state);
         let (_, workspace) = cx.add_window(|cx| {
             let mut workspace = Workspace::new(
-                app_state.settings,
-                app_state.language_registry,
-                app_state.rpc,
+                app_state.settings.clone(),
+                app_state.language_registry.clone(),
+                app_state.rpc.clone(),
                 cx,
             );
             workspace.add_worktree(dir.path(), cx);
@@ -1194,7 +1208,7 @@ mod tests {
 
         // Create a new untitled buffer
         let editor = workspace.update(&mut cx, |workspace, cx| {
-            workspace.open_new_file(&(), cx);
+            workspace.open_new_file(&app_state, cx);
             workspace
                 .active_item(cx)
                 .unwrap()
@@ -1202,6 +1216,7 @@ mod tests {
                 .downcast::<Editor>()
                 .unwrap()
         });
+
         editor.update(&mut cx, |editor, cx| {
             assert!(!editor.is_dirty(cx.as_ref()));
             assert_eq!(editor.title(cx.as_ref()), "untitled");
@@ -1244,7 +1259,7 @@ mod tests {
         // Open the same newly-created file in another pane item. The new editor should reuse
         // the same buffer.
         workspace.update(&mut cx, |workspace, cx| {
-            workspace.open_new_file(&(), cx);
+            workspace.open_new_file(&app_state, cx);
             workspace.split_pane(workspace.active_pane().clone(), SplitDirection::Right, cx);
             assert!(workspace
                 .open_entry((tree.id(), Path::new("the-new-name").into()), cx)
@@ -1263,6 +1278,25 @@ mod tests {
         })
     }
 
+    #[gpui::test]
+    async fn test_new_empty_workspace(mut cx: gpui::TestAppContext) {
+        cx.update(init);
+
+        let app_state = cx.read(build_app_state);
+        cx.dispatch_global_action("workspace:new_file", app_state);
+        let window_id = *cx.window_ids().first().unwrap();
+        let workspace = cx.root_view::<Workspace>(window_id).unwrap();
+        workspace.update(&mut cx, |workspace, cx| {
+            let editor = workspace
+                .active_item(cx)
+                .unwrap()
+                .to_any()
+                .downcast::<Editor>()
+                .unwrap();
+            assert!(editor.read(cx).text(cx.as_ref()).is_empty());
+        });
+    }
+
     #[gpui::test]
     async fn test_pane_actions(mut cx: gpui::TestAppContext) {
         cx.update(|cx| pane::init(cx));
diff --git a/zed/src/worktree.rs b/zed/src/worktree.rs
index 1d8702d0e7..c20f25b2a0 100644
--- a/zed/src/worktree.rs
+++ b/zed/src/worktree.rs
@@ -529,7 +529,7 @@ impl LocalWorktree {
                 let file = fs::File::create(&abs_path)?;
                 let mut writer = io::BufWriter::with_capacity(buffer_size, &file);
                 for chunk in text.chunks() {
-                    writer.write(chunk.as_bytes())?;
+                    writer.write_all(chunk.as_bytes())?;
                 }
                 writer.flush()?;
 
@@ -1824,8 +1824,8 @@ impl WorktreeHandle for ModelHandle<Worktree> {
 }
 
 pub enum FileIter<'a> {
-    All(Cursor<'a, Entry, FileCount, FileCount>),
-    Visible(Cursor<'a, Entry, VisibleFileCount, VisibleFileCount>),
+    All(Cursor<'a, Entry, FileCount, ()>),
+    Visible(Cursor<'a, Entry, VisibleFileCount, ()>),
 }
 
 impl<'a> FileIter<'a> {
@@ -1844,11 +1844,11 @@ impl<'a> FileIter<'a> {
     fn next_internal(&mut self) {
         match self {
             Self::All(cursor) => {
-                let ix = *cursor.start();
+                let ix = *cursor.seek_start();
                 cursor.seek_forward(&FileCount(ix.0 + 1), Bias::Right, &());
             }
             Self::Visible(cursor) => {
-                let ix = *cursor.start();
+                let ix = *cursor.seek_start();
                 cursor.seek_forward(&VisibleFileCount(ix.0 + 1), Bias::Right, &());
             }
         }