diff --git a/build.zig b/build.zig
index 9764fd5..04b8cd5 100644
--- a/build.zig
+++ b/build.zig
@@ -297,6 +297,11 @@ pub fn build_exe(
         .optimize = optimize,
     });
 
+    const diffz_dep = b.dependency("diffz", .{
+        .target = target,
+        .optimize = optimize,
+    });
+
     const fuzzig_dep = b.dependency("fuzzig", .{
         .target = target,
         .optimize = optimize,
@@ -601,6 +606,7 @@ pub fn build_exe(
             .{ .name = "Buffer", .module = Buffer_mod },
             .{ .name = "tracy", .module = tracy_mod },
             .{ .name = "dizzy", .module = dizzy_dep.module("dizzy") },
+            .{ .name = "diffz", .module = diffz_dep.module("diffz") },
             .{ .name = "log", .module = log_mod },
             .{ .name = "cbor", .module = cbor_mod },
         },
diff --git a/build.zig.zon b/build.zig.zon
index 6d5fdc1..dfc143b 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -42,6 +42,10 @@
             .hash = "zigwin32-25.0.28-preview-AAAAAICM5AMResOGQnQ85mfe60TTOQeMtt7GRATUOKoP",
             .lazy = true,
         },
+        .diffz = .{
+            .url = "git+https://github.com/ziglibs/diffz.git#fbdf690b87db6b1142bbce6d4906f90b09ce60bb",
+            .hash = "diffz-0.0.1-G2tlIezMAQBwGNGDs7Hn_N25dWSjEzgR_FAx9GFAvCuZ",
+        },
     },
     .paths = .{
         "include",
diff --git a/src/diff.zig b/src/diff.zig
index ffded8c..76f7b9b 100644
--- a/src/diff.zig
+++ b/src/diff.zig
@@ -1,10 +1,5 @@
-const std = @import("std");
-const tp = @import("thespian");
-const dizzy = @import("dizzy");
-const Buffer = @import("Buffer");
-const tracy = @import("tracy");
-
-const module_name = @typeName(@This());
+pub const dizzy = @import("dizzy.zig");
+pub const diffz = @import("diffz.zig");
 
 pub const Kind = enum { insert, delete };
 pub const Diff = struct {
@@ -22,260 +17,3 @@ pub const Edit = struct {
     end: usize,
     bytes: []const u8,
 };
-
-pub fn create() !AsyncDiffer {
-    return .{ .pid = try Process.create() };
-}
-
-pub const AsyncDiffer = struct {
-    pid: ?tp.pid,
-
-    pub fn deinit(self: *@This()) void {
-        if (self.pid) |pid| {
-            pid.send(.{"shutdown"}) catch {};
-            pid.deinit();
-            self.pid = null;
-        }
-    }
-
-    fn text_from_root(root: Buffer.Root, eol_mode: Buffer.EolMode) ![]const u8 {
-        var text: std.Io.Writer.Allocating = .init(std.heap.c_allocator);
-        defer text.deinit();
-        try root.store(&text.writer, eol_mode);
-        return text.toOwnedSlice();
-    }
-
-    pub const CallBack = fn (from: tp.pid_ref, edits: []Diff) void;
-
-    pub fn diff_buffer(self: @This(), cb: *const CallBack, buffer: *const Buffer) tp.result {
-        const eol_mode = buffer.file_eol_mode;
-        const text_dst = text_from_root(buffer.root, eol_mode) catch |e| return tp.exit_error(e, @errorReturnTrace());
-        errdefer std.heap.c_allocator.free(text_dst);
-        const text_src = if (buffer.get_vcs_content()) |vcs_content|
-            std.heap.c_allocator.dupe(u8, vcs_content) catch |e| return tp.exit_error(e, @errorReturnTrace())
-        else
-            text_from_root(buffer.last_save orelse return, eol_mode) catch |e| return tp.exit_error(e, @errorReturnTrace());
-        errdefer std.heap.c_allocator.free(text_src);
-        const text_dst_ptr: usize = if (text_dst.len > 0) @intFromPtr(text_dst.ptr) else 0;
-        const text_src_ptr: usize = if (text_src.len > 0) @intFromPtr(text_src.ptr) else 0;
-        if (self.pid) |pid| try pid.send(.{ "D", @intFromPtr(cb), text_dst_ptr, text_dst.len, text_src_ptr, text_src.len });
-    }
-};
-
-const Process = struct {
-    receiver: Receiver,
-
-    const Receiver = tp.Receiver(*Process);
-    const allocator = std.heap.c_allocator;
-
-    pub fn create() !tp.pid {
-        const self = try allocator.create(Process);
-        errdefer allocator.destroy(self);
-        self.* = .{
-            .receiver = Receiver.init(Process.receive, self),
-        };
-        return tp.spawn_link(allocator, self, Process.start, module_name);
-    }
-
-    fn start(self: *Process) tp.result {
-        errdefer self.deinit();
-        tp.receive(&self.receiver);
-    }
-
-    fn deinit(self: *Process) void {
-        allocator.destroy(self);
-    }
-
-    fn receive(self: *Process, from: tp.pid_ref, m: tp.message) tp.result {
-        errdefer self.deinit();
-
-        var cb: usize = 0;
-        var text_dst_ptr: usize = 0;
-        var text_dst_len: usize = 0;
-        var text_src_ptr: usize = 0;
-        var text_src_len: usize = 0;
-
-        return if (try m.match(.{ "D", tp.extract(&cb), tp.extract(&text_dst_ptr), tp.extract(&text_dst_len), tp.extract(&text_src_ptr), tp.extract(&text_src_len) })) blk: {
-            const text_dst = if (text_dst_len > 0) @as([*]const u8, @ptrFromInt(text_dst_ptr))[0..text_dst_len] else "";
-            const text_src = if (text_src_len > 0) @as([*]const u8, @ptrFromInt(text_src_ptr))[0..text_src_len] else "";
-            break :blk do_diff_async(from, cb, text_dst, text_src) catch |e| tp.exit_error(e, @errorReturnTrace());
-        } else if (try m.match(.{"shutdown"}))
-            tp.exit_normal();
-    }
-
-    fn do_diff_async(from_: tp.pid_ref, cb_addr: usize, text_dst: []const u8, text_src: []const u8) !void {
-        defer std.heap.c_allocator.free(text_dst);
-        defer std.heap.c_allocator.free(text_src);
-        const cb_: *AsyncDiffer.CallBack = if (cb_addr == 0) return else @ptrFromInt(cb_addr);
-
-        var arena_ = std.heap.ArenaAllocator.init(allocator);
-        defer arena_.deinit();
-        const arena = arena_.allocator();
-
-        const edits = try diff(arena, text_dst, text_src);
-        cb_(from_, edits);
-    }
-};
-
-pub fn diff(allocator: std.mem.Allocator, dst: []const u8, src: []const u8) ![]Diff {
-    var arena_ = std.heap.ArenaAllocator.init(allocator);
-    defer arena_.deinit();
-    const arena = arena_.allocator();
-    const frame = tracy.initZone(@src(), .{ .name = "diff" });
-    defer frame.deinit();
-
-    var dizzy_edits = std.ArrayListUnmanaged(dizzy.Edit){};
-    var scratch = std.ArrayListUnmanaged(u32){};
-    var diffs: std.ArrayList(Diff) = .empty;
-    errdefer diffs.deinit(allocator);
-
-    const scratch_len = 4 * (dst.len + src.len) + 2;
-    try scratch.ensureTotalCapacity(arena, scratch_len);
-    scratch.items.len = scratch_len;
-
-    try dizzy.PrimitiveSliceDiffer(u8).diff(arena, &dizzy_edits, src, dst, scratch.items);
-
-    if (dizzy_edits.items.len > 2)
-        try diffs.ensureTotalCapacity(allocator, (dizzy_edits.items.len - 1) / 2);
-
-    var lines_dst: usize = 0;
-    var pos_src: usize = 0;
-    var pos_dst: usize = 0;
-    var last_offset: usize = 0;
-
-    for (dizzy_edits.items) |dizzy_edit| {
-        switch (dizzy_edit.kind) {
-            .equal => {
-                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
-                pos_src += dist;
-                pos_dst += dist;
-                scan_char(src[dizzy_edit.range.start..dizzy_edit.range.end], &lines_dst, '\n', &last_offset);
-            },
-            .insert => {
-                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
-                pos_src += 0;
-                pos_dst += dist;
-                const line_start_dst: usize = lines_dst;
-                scan_char(dst[dizzy_edit.range.start..dizzy_edit.range.end], &lines_dst, '\n', null);
-                (try diffs.addOne(allocator)).* = .{
-                    .kind = .insert,
-                    .line = line_start_dst,
-                    .offset = last_offset,
-                    .start = dizzy_edit.range.start,
-                    .end = dizzy_edit.range.end,
-                    .bytes = dst[dizzy_edit.range.start..dizzy_edit.range.end],
-                };
-            },
-            .delete => {
-                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
-                pos_src += dist;
-                pos_dst += 0;
-                (try diffs.addOne(allocator)).* = .{
-                    .kind = .delete,
-                    .line = lines_dst,
-                    .offset = last_offset,
-                    .start = dizzy_edit.range.start,
-                    .end = dizzy_edit.range.end,
-                    .bytes = src[dizzy_edit.range.start..dizzy_edit.range.end],
-                };
-            },
-        }
-    }
-    return diffs.toOwnedSlice(allocator);
-}
-
-pub fn get_edits(allocator: std.mem.Allocator, dst: []const u8, src: []const u8) ![]Edit {
-    var arena_ = std.heap.ArenaAllocator.init(allocator);
-    defer arena_.deinit();
-    const arena = arena_.allocator();
-    const frame = tracy.initZone(@src(), .{ .name = "diff" });
-    defer frame.deinit();
-
-    var dizzy_edits = std.ArrayListUnmanaged(dizzy.Edit){};
-    var scratch = std.ArrayListUnmanaged(u32){};
-    var edits = std.ArrayList(Edit).init(allocator);
-
-    const scratch_len = 4 * (dst.len + src.len) + 2;
-    try scratch.ensureTotalCapacity(arena, scratch_len);
-    scratch.items.len = scratch_len;
-
-    try dizzy.PrimitiveSliceDiffer(u8).diff(arena, &dizzy_edits, src, dst, scratch.items);
-
-    if (dizzy_edits.items.len > 2)
-        try edits.ensureTotalCapacity((dizzy_edits.items.len - 1) / 2);
-
-    var pos: usize = 0;
-
-    for (dizzy_edits.items) |dizzy_edit| {
-        switch (dizzy_edit.kind) {
-            .equal => {
-                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
-                pos += dist;
-            },
-            .insert => {
-                (try edits.addOne()).* = .{
-                    .kind = .insert,
-                    .start = pos,
-                    .end = pos,
-                    .bytes = dst[dizzy_edit.range.start..dizzy_edit.range.end],
-                };
-                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
-                pos += dist;
-            },
-            .delete => {
-                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
-                pos += 0;
-                (try edits.addOne()).* = .{
-                    .kind = .delete,
-                    .start = pos,
-                    .end = pos + dist,
-                    .bytes = "",
-                };
-            },
-        }
-    }
-    return edits.toOwnedSlice();
-}
-
-fn scan_char(chars: []const u8, lines: *usize, char: u8, last_offset: ?*usize) void {
-    var pos = chars;
-    while (pos.len > 0) {
-        if (pos[0] == char) {
-            if (last_offset) |off| off.* = pos.len - 1;
-            lines.* += 1;
-        }
-        pos = pos[1..];
-    }
-}
-
-pub fn assert_edits_valid(allocator: std.mem.Allocator, dst: []const u8, src: []const u8, edits: []Edit) void {
-    const frame = tracy.initZone(@src(), .{ .name = "diff validate" });
-    defer frame.deinit();
-    var result = std.ArrayListUnmanaged(u8){};
-    var tmp = std.ArrayListUnmanaged(u8){};
-    defer result.deinit(allocator);
-    defer tmp.deinit(allocator);
-    result.appendSlice(allocator, src) catch @panic("assert_edits_valid OOM");
-
-    for (edits) |edit| {
-        tmp.clearRetainingCapacity();
-        tmp.appendSlice(allocator, result.items[0..edit.start]) catch @panic("assert_edits_valid OOM");
-        tmp.appendSlice(allocator, edit.bytes) catch @panic("assert_edits_valid OOM");
-        tmp.appendSlice(allocator, result.items[edit.end..]) catch @panic("assert_edits_valid OOM");
-        result.clearRetainingCapacity();
-        result.appendSlice(allocator, tmp.items) catch @panic("assert_edits_valid OOM");
-    }
-
-    if (!std.mem.eql(u8, dst, result.items)) {
-        write_file(src, "bad_diff_src") catch @panic("invalid edits write failed");
-        write_file(dst, "bad_diff_dst") catch @panic("invalid edits write failed");
-        write_file(result.items, "bad_diff_result") catch @panic("invalid edits write failed");
-        @panic("invalid edits");
-    }
-}
-
-fn write_file(data: []const u8, file_name: []const u8) !void {
-    var file = try std.fs.cwd().createFile(file_name, .{ .truncate = true });
-    defer file.close();
-    return file.writeAll(data);
-}
diff --git a/src/diffz.zig b/src/diffz.zig
new file mode 100644
index 0000000..dabb199
--- /dev/null
+++ b/src/diffz.zig
@@ -0,0 +1,179 @@
+const std = @import("std");
+const tp = @import("thespian");
+const diffz = @import("diffz");
+const Buffer = @import("Buffer");
+const tracy = @import("tracy");
+
+const module_name = @typeName(@This());
+
+const diff_ = @import("diff.zig");
+const Kind = diff_.Kind;
+const Diff = diff_.Diff;
+const Edit = diff_.Edit;
+
+pub fn create() !AsyncDiffer {
+    return .{ .pid = try Process.create() };
+}
+
+pub const AsyncDiffer = struct {
+    pid: ?tp.pid,
+
+    pub fn deinit(self: *@This()) void {
+        if (self.pid) |pid| {
+            pid.send(.{"shutdown"}) catch {};
+            pid.deinit();
+            self.pid = null;
+        }
+    }
+
+    fn text_from_root(root: Buffer.Root, eol_mode: Buffer.EolMode) ![]const u8 {
+        var text: std.Io.Writer.Allocating = .init(std.heap.c_allocator);
+        defer text.deinit();
+        try root.store(&text.writer, eol_mode);
+        return text.toOwnedSlice();
+    }
+
+    pub const CallBack = fn (from: tp.pid_ref, edits: []Diff) void;
+
+    pub fn diff_buffer(self: @This(), cb: *const CallBack, buffer: *const Buffer) tp.result {
+        const eol_mode = buffer.file_eol_mode;
+        const text_dst = text_from_root(buffer.root, eol_mode) catch |e| return tp.exit_error(e, @errorReturnTrace());
+        errdefer std.heap.c_allocator.free(text_dst);
+        const text_src = if (buffer.get_vcs_content()) |vcs_content|
+            std.heap.c_allocator.dupe(u8, vcs_content) catch |e| return tp.exit_error(e, @errorReturnTrace())
+        else
+            text_from_root(buffer.last_save orelse return, eol_mode) catch |e| return tp.exit_error(e, @errorReturnTrace());
+        errdefer std.heap.c_allocator.free(text_src);
+        const text_dst_ptr: usize = if (text_dst.len > 0) @intFromPtr(text_dst.ptr) else 0;
+        const text_src_ptr: usize = if (text_src.len > 0) @intFromPtr(text_src.ptr) else 0;
+        if (self.pid) |pid| try pid.send(.{ "D", @intFromPtr(cb), text_dst_ptr, text_dst.len, text_src_ptr, text_src.len });
+    }
+};
+
+const Process = struct {
+    receiver: Receiver,
+
+    const Receiver = tp.Receiver(*Process);
+    const allocator = std.heap.c_allocator;
+
+    pub fn create() !tp.pid {
+        const self = try allocator.create(Process);
+        errdefer allocator.destroy(self);
+        self.* = .{
+            .receiver = Receiver.init(Process.receive, self),
+        };
+        return tp.spawn_link(allocator, self, Process.start, module_name);
+    }
+
+    fn start(self: *Process) tp.result {
+        errdefer self.deinit();
+        tp.receive(&self.receiver);
+    }
+
+    fn deinit(self: *Process) void {
+        allocator.destroy(self);
+    }
+
+    fn receive(self: *Process, from: tp.pid_ref, m: tp.message) tp.result {
+        errdefer self.deinit();
+
+        var cb: usize = 0;
+        var text_dst_ptr: usize = 0;
+        var text_dst_len: usize = 0;
+        var text_src_ptr: usize = 0;
+        var text_src_len: usize = 0;
+
+        return if (try m.match(.{ "D", tp.extract(&cb), tp.extract(&text_dst_ptr), tp.extract(&text_dst_len), tp.extract(&text_src_ptr), tp.extract(&text_src_len) })) blk: {
+            const text_dst = if (text_dst_len > 0) @as([*]const u8, @ptrFromInt(text_dst_ptr))[0..text_dst_len] else "";
+            const text_src = if (text_src_len > 0) @as([*]const u8, @ptrFromInt(text_src_ptr))[0..text_src_len] else "";
+            break :blk do_diff_async(from, cb, text_dst, text_src) catch |e| tp.exit_error(e, @errorReturnTrace());
+        } else if (try m.match(.{"shutdown"}))
+            tp.exit_normal();
+    }
+
+    fn do_diff_async(from_: tp.pid_ref, cb_addr: usize, text_dst: []const u8, text_src: []const u8) !void {
+        defer std.heap.c_allocator.free(text_dst);
+        defer std.heap.c_allocator.free(text_src);
+        const cb_: *AsyncDiffer.CallBack = if (cb_addr == 0) return else @ptrFromInt(cb_addr);
+
+        var arena_ = std.heap.ArenaAllocator.init(allocator);
+        defer arena_.deinit();
+        const arena = arena_.allocator();
+
+        const edits = try diff(arena, text_dst, text_src);
+        cb_(from_, edits);
+    }
+};
+
+pub fn diff(allocator: std.mem.Allocator, dst: []const u8, src: []const u8) error{OutOfMemory}![]Diff {
+    var arena_ = std.heap.ArenaAllocator.init(allocator);
+    defer arena_.deinit();
+    const arena = arena_.allocator();
+    const frame = tracy.initZone(@src(), .{ .name = "diff" });
+    defer frame.deinit();
+
+    var diffs: std.ArrayList(Diff) = .empty;
+    errdefer diffs.deinit(allocator);
+
+    const dmp = diffz.default;
+    const diff_list = try diffz.diff(&dmp, arena, src, dst, true);
+
+    if (diff_list.items.len > 2)
+        try diffs.ensureTotalCapacity(allocator, (diff_list.items.len - 1) / 2);
+
+    var lines_dst: usize = 0;
+    var pos_src: usize = 0;
+    var pos_dst: usize = 0;
+    var last_offset: usize = 0;
+
+    for (diff_list.items) |diffz_diff| {
+        switch (diffz_diff.operation) {
+            .equal => {
+                const dist = diffz_diff.text.len;
+                pos_src += dist;
+                pos_dst += dist;
+                scan_char(diffz_diff.text, &lines_dst, '\n', &last_offset);
+            },
+            .insert => {
+                const dist = diffz_diff.text.len;
+                pos_src += 0;
+                pos_dst += dist;
+                const line_start_dst: usize = lines_dst;
+                scan_char(diffz_diff.text, &lines_dst, '\n', null);
+                (try diffs.addOne(allocator)).* = .{
+                    .kind = .insert,
+                    .line = line_start_dst,
+                    .offset = last_offset,
+                    .start = line_start_dst + last_offset,
+                    .end = line_start_dst + last_offset + dist,
+                    .bytes = diffz_diff.text,
+                };
+            },
+            .delete => {
+                const dist = diffz_diff.text.len;
+                pos_src += dist;
+                pos_dst += 0;
+                (try diffs.addOne(allocator)).* = .{
+                    .kind = .delete,
+                    .line = lines_dst,
+                    .offset = last_offset,
+                    .start = lines_dst + last_offset,
+                    .end = lines_dst + last_offset + dist,
+                    .bytes = diffz_diff.text,
+                };
+            },
+        }
+    }
+    return diffs.toOwnedSlice(allocator);
+}
+
+fn scan_char(chars: []const u8, lines: *usize, char: u8, last_offset: ?*usize) void {
+    var pos = chars;
+    while (pos.len > 0) {
+        if (pos[0] == char) {
+            if (last_offset) |off| off.* = pos.len - 1;
+            lines.* += 1;
+        }
+        pos = pos[1..];
+    }
+}
diff --git a/src/dizzy.zig b/src/dizzy.zig
new file mode 100644
index 0000000..e8c9bd5
--- /dev/null
+++ b/src/dizzy.zig
@@ -0,0 +1,269 @@
+const std = @import("std");
+const tp = @import("thespian");
+const dizzy = @import("dizzy");
+const Buffer = @import("Buffer");
+const tracy = @import("tracy");
+
+const module_name = @typeName(@This());
+
+const diff_ = @import("diff.zig");
+const Kind = diff_.Kind;
+const Diff = diff_.Diff;
+const Edit = diff_.Edit;
+
+pub fn create() !AsyncDiffer {
+    return .{ .pid = try Process.create() };
+}
+
+pub const AsyncDiffer = struct {
+    pid: ?tp.pid,
+
+    pub fn deinit(self: *@This()) void {
+        if (self.pid) |pid| {
+            pid.send(.{"shutdown"}) catch {};
+            pid.deinit();
+            self.pid = null;
+        }
+    }
+
+    fn text_from_root(root: Buffer.Root, eol_mode: Buffer.EolMode) ![]const u8 {
+        var text: std.Io.Writer.Allocating = .init(std.heap.c_allocator);
+        defer text.deinit();
+        try root.store(&text.writer, eol_mode);
+        return text.toOwnedSlice();
+    }
+
+    pub const CallBack = fn (from: tp.pid_ref, edits: []Diff) void;
+
+    pub fn diff_buffer(self: @This(), cb: *const CallBack, buffer: *const Buffer) tp.result {
+        const eol_mode = buffer.file_eol_mode;
+        const text_dst = text_from_root(buffer.root, eol_mode) catch |e| return tp.exit_error(e, @errorReturnTrace());
+        errdefer std.heap.c_allocator.free(text_dst);
+        const text_src = if (buffer.get_vcs_content()) |vcs_content|
+            std.heap.c_allocator.dupe(u8, vcs_content) catch |e| return tp.exit_error(e, @errorReturnTrace())
+        else
+            text_from_root(buffer.last_save orelse return, eol_mode) catch |e| return tp.exit_error(e, @errorReturnTrace());
+        errdefer std.heap.c_allocator.free(text_src);
+        const text_dst_ptr: usize = if (text_dst.len > 0) @intFromPtr(text_dst.ptr) else 0;
+        const text_src_ptr: usize = if (text_src.len > 0) @intFromPtr(text_src.ptr) else 0;
+        if (self.pid) |pid| try pid.send(.{ "D", @intFromPtr(cb), text_dst_ptr, text_dst.len, text_src_ptr, text_src.len });
+    }
+};
+
+const Process = struct {
+    receiver: Receiver,
+
+    const Receiver = tp.Receiver(*Process);
+    const allocator = std.heap.c_allocator;
+
+    pub fn create() !tp.pid {
+        const self = try allocator.create(Process);
+        errdefer allocator.destroy(self);
+        self.* = .{
+            .receiver = Receiver.init(Process.receive, self),
+        };
+        return tp.spawn_link(allocator, self, Process.start, module_name);
+    }
+
+    fn start(self: *Process) tp.result {
+        errdefer self.deinit();
+        tp.receive(&self.receiver);
+    }
+
+    fn deinit(self: *Process) void {
+        allocator.destroy(self);
+    }
+
+    fn receive(self: *Process, from: tp.pid_ref, m: tp.message) tp.result {
+        errdefer self.deinit();
+
+        var cb: usize = 0;
+        var text_dst_ptr: usize = 0;
+        var text_dst_len: usize = 0;
+        var text_src_ptr: usize = 0;
+        var text_src_len: usize = 0;
+
+        return if (try m.match(.{ "D", tp.extract(&cb), tp.extract(&text_dst_ptr), tp.extract(&text_dst_len), tp.extract(&text_src_ptr), tp.extract(&text_src_len) })) blk: {
+            const text_dst = if (text_dst_len > 0) @as([*]const u8, @ptrFromInt(text_dst_ptr))[0..text_dst_len] else "";
+            const text_src = if (text_src_len > 0) @as([*]const u8, @ptrFromInt(text_src_ptr))[0..text_src_len] else "";
+            break :blk do_diff_async(from, cb, text_dst, text_src) catch |e| tp.exit_error(e, @errorReturnTrace());
+        } else if (try m.match(.{"shutdown"}))
+            tp.exit_normal();
+    }
+
+    fn do_diff_async(from_: tp.pid_ref, cb_addr: usize, text_dst: []const u8, text_src: []const u8) !void {
+        defer std.heap.c_allocator.free(text_dst);
+        defer std.heap.c_allocator.free(text_src);
+        const cb_: *AsyncDiffer.CallBack = if (cb_addr == 0) return else @ptrFromInt(cb_addr);
+
+        var arena_ = std.heap.ArenaAllocator.init(allocator);
+        defer arena_.deinit();
+        const arena = arena_.allocator();
+
+        const edits = try diff(arena, text_dst, text_src);
+        cb_(from_, edits);
+    }
+};
+
+pub fn diff(allocator: std.mem.Allocator, dst: []const u8, src: []const u8) ![]Diff {
+    var arena_ = std.heap.ArenaAllocator.init(allocator);
+    defer arena_.deinit();
+    const arena = arena_.allocator();
+    const frame = tracy.initZone(@src(), .{ .name = "diff" });
+    defer frame.deinit();
+
+    var dizzy_edits = std.ArrayListUnmanaged(dizzy.Edit){};
+    var scratch = std.ArrayListUnmanaged(u32){};
+    var diffs: std.ArrayList(Diff) = .empty;
+    errdefer diffs.deinit(allocator);
+
+    const scratch_len = 4 * (dst.len + src.len) + 2;
+    try scratch.ensureTotalCapacity(arena, scratch_len);
+    scratch.items.len = scratch_len;
+
+    try dizzy.PrimitiveSliceDiffer(u8).diff(arena, &dizzy_edits, src, dst, scratch.items);
+
+    if (dizzy_edits.items.len > 2)
+        try diffs.ensureTotalCapacity(allocator, (dizzy_edits.items.len - 1) / 2);
+
+    var lines_dst: usize = 0;
+    var pos_src: usize = 0;
+    var pos_dst: usize = 0;
+    var last_offset: usize = 0;
+
+    for (dizzy_edits.items) |dizzy_edit| {
+        switch (dizzy_edit.kind) {
+            .equal => {
+                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
+                pos_src += dist;
+                pos_dst += dist;
+                scan_char(src[dizzy_edit.range.start..dizzy_edit.range.end], &lines_dst, '\n', &last_offset);
+            },
+            .insert => {
+                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
+                pos_src += 0;
+                pos_dst += dist;
+                const line_start_dst: usize = lines_dst;
+                scan_char(dst[dizzy_edit.range.start..dizzy_edit.range.end], &lines_dst, '\n', null);
+                (try diffs.addOne(allocator)).* = .{
+                    .kind = .insert,
+                    .line = line_start_dst,
+                    .offset = last_offset,
+                    .start = dizzy_edit.range.start,
+                    .end = dizzy_edit.range.end,
+                    .bytes = dst[dizzy_edit.range.start..dizzy_edit.range.end],
+                };
+            },
+            .delete => {
+                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
+                pos_src += dist;
+                pos_dst += 0;
+                (try diffs.addOne(allocator)).* = .{
+                    .kind = .delete,
+                    .line = lines_dst,
+                    .offset = last_offset,
+                    .start = dizzy_edit.range.start,
+                    .end = dizzy_edit.range.end,
+                    .bytes = src[dizzy_edit.range.start..dizzy_edit.range.end],
+                };
+            },
+        }
+    }
+    return diffs.toOwnedSlice(allocator);
+}
+
+pub fn get_edits(allocator: std.mem.Allocator, dst: []const u8, src: []const u8) ![]Edit {
+    var arena_ = std.heap.ArenaAllocator.init(allocator);
+    defer arena_.deinit();
+    const arena = arena_.allocator();
+    const frame = tracy.initZone(@src(), .{ .name = "diff" });
+    defer frame.deinit();
+
+    var dizzy_edits = std.ArrayListUnmanaged(dizzy.Edit){};
+    var scratch = std.ArrayListUnmanaged(u32){};
+    var edits = std.ArrayList(Edit).init(allocator);
+
+    const scratch_len = 4 * (dst.len + src.len) + 2;
+    try scratch.ensureTotalCapacity(arena, scratch_len);
+    scratch.items.len = scratch_len;
+
+    try dizzy.PrimitiveSliceDiffer(u8).diff(arena, &dizzy_edits, src, dst, scratch.items);
+
+    if (dizzy_edits.items.len > 2)
+        try edits.ensureTotalCapacity((dizzy_edits.items.len - 1) / 2);
+
+    var pos: usize = 0;
+
+    for (dizzy_edits.items) |dizzy_edit| {
+        switch (dizzy_edit.kind) {
+            .equal => {
+                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
+                pos += dist;
+            },
+            .insert => {
+                (try edits.addOne()).* = .{
+                    .kind = .insert,
+                    .start = pos,
+                    .end = pos,
+                    .bytes = dst[dizzy_edit.range.start..dizzy_edit.range.end],
+                };
+                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
+                pos += dist;
+            },
+            .delete => {
+                const dist = dizzy_edit.range.end - dizzy_edit.range.start;
+                pos += 0;
+                (try edits.addOne()).* = .{
+                    .kind = .delete,
+                    .start = pos,
+                    .end = pos + dist,
+                    .bytes = "",
+                };
+            },
+        }
+    }
+    return edits.toOwnedSlice();
+}
+
+fn scan_char(chars: []const u8, lines: *usize, char: u8, last_offset: ?*usize) void {
+    var pos = chars;
+    while (pos.len > 0) {
+        if (pos[0] == char) {
+            if (last_offset) |off| off.* = pos.len - 1;
+            lines.* += 1;
+        }
+        pos = pos[1..];
+    }
+}
+
+pub fn assert_edits_valid(allocator: std.mem.Allocator, dst: []const u8, src: []const u8, edits: []Edit) void {
+    const frame = tracy.initZone(@src(), .{ .name = "diff validate" });
+    defer frame.deinit();
+    var result = std.ArrayListUnmanaged(u8){};
+    var tmp = std.ArrayListUnmanaged(u8){};
+    defer result.deinit(allocator);
+    defer tmp.deinit(allocator);
+    result.appendSlice(allocator, src) catch @panic("assert_edits_valid OOM");
+
+    for (edits) |edit| {
+        tmp.clearRetainingCapacity();
+        tmp.appendSlice(allocator, result.items[0..edit.start]) catch @panic("assert_edits_valid OOM");
+        tmp.appendSlice(allocator, edit.bytes) catch @panic("assert_edits_valid OOM");
+        tmp.appendSlice(allocator, result.items[edit.end..]) catch @panic("assert_edits_valid OOM");
+        result.clearRetainingCapacity();
+        result.appendSlice(allocator, tmp.items) catch @panic("assert_edits_valid OOM");
+    }
+
+    if (!std.mem.eql(u8, dst, result.items)) {
+        write_file(src, "bad_diff_src") catch @panic("invalid edits write failed");
+        write_file(dst, "bad_diff_dst") catch @panic("invalid edits write failed");
+        write_file(result.items, "bad_diff_result") catch @panic("invalid edits write failed");
+        @panic("invalid edits");
+    }
+}
+
+fn write_file(data: []const u8, file_name: []const u8) !void {
+    var file = try std.fs.cwd().createFile(file_name, .{ .truncate = true });
+    defer file.close();
+    return file.writeAll(data);
+}
diff --git a/src/tui/editor.zig b/src/tui/editor.zig
index 63e34cc..b389557 100644
--- a/src/tui/editor.zig
+++ b/src/tui/editor.zig
@@ -5156,7 +5156,7 @@ pub const Editor = struct {
                         const frame = tracy.initZone(@src(), .{ .name = "editor diff syntax" });
                         defer frame.deinit();
                         const diff = @import("diff");
-                        const edits = try diff.diff(self.allocator, content, old_content.written());
+                        const edits = try diff.dizzy.diff(self.allocator, content, old_content.written());
                         defer self.allocator.free(edits);
                         for (edits) |edit|
                             syntax_process_edit(syn, edit);
@@ -6087,7 +6087,7 @@ pub const Editor = struct {
         var last_end_row: usize = 0;
         var last_end_col_pos: usize = 0;
 
-        const diffs = try @import("diff").diff(self.allocator, new_content, content);
+        const diffs = try @import("diff").dizzy.diff(self.allocator, new_content, content);
         defer self.allocator.free(diffs);
         var first = true;
         for (diffs) |diff| {
diff --git a/src/tui/editor_gutter.zig b/src/tui/editor_gutter.zig
index 7e655c1..44f120a 100644
--- a/src/tui/editor_gutter.zig
+++ b/src/tui/editor_gutter.zig
@@ -35,7 +35,7 @@ symbols: bool,
 width: usize = 4,
 editor: *ed.Editor,
 editor_widget: ?*const Widget = null,
-diff_: diff.AsyncDiffer,
+diff_: diff.diffz.AsyncDiffer,
 diff_symbols: std.ArrayList(Symbol),
 
 const Self = @This();
@@ -55,7 +55,7 @@ pub fn create(allocator: Allocator, parent: Widget, event_source: Widget, editor
         .highlight = tui.config().highlight_current_line_gutter,
         .symbols = tui.config().gutter_symbols,
         .editor = editor,
-        .diff_ = try diff.create(),
+        .diff_ = try diff.diffz.create(),
         .diff_symbols = .empty,
     };
     try tui.message_filters().add(MessageFilter.bind(self, filter_receive));