From c6be02adeb930834aeb7d8c484e89106023550d1 Mon Sep 17 00:00:00 2001
From: Gabriel Schneider <gbrls@0x4200.cafe>
Date: Fri, 2 Oct 2026 00:53:57 -0300
Subject: A Zerox twin's save no longer makes its other twin say reloaded: a
 watch that finds the pane holding the disk's text already takes it as seen,
 silently

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 src/file_watch.zig | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

(limited to 'src')

diff --git a/src/file_watch.zig b/src/file_watch.zig
index 46764a73..4aba6c39 100644
--- a/src/file_watch.zig
+++ b/src/file_watch.zig
@@ -469,6 +469,14 @@ pub fn reloadPane(
             .text => |accepted| if (accepted == hash) return false,
             .pdf => {},
         }
+        // The pane holds the disk's text already (a Zerox twin saved, its
+        // other twin watching the same file): nothing reloaded, nothing said.
+        if (std.mem.eql(u8, file.content, bytes)) {
+            if (watches[id]) |*live| if (live.serial == watched.serial) {
+                live.generation = .{ .text = hash };
+            };
+            return false;
+        }
         if (!core.reloadWatchedFile(@intCast(id), bytes)) return false;
         const current = core.panes[id] orelse return false;
         if (current.serial != watched.serial) return false;
@@ -713,6 +721,38 @@ test "restored file watches preserve snapshots and accept later disk changes" {
     }
 }
 
+test "a Zerox twin's save wakes its other twin's watch, which says nothing: their text is the file's already" {
+    if (comptime !supported or !filesystem.platform_has_fs) return;
+    const io = std.testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+    try tmp.dir.writeFile(io, .{ .sub_path = "twinned", .data = "before\n" });
+    var path_buf: [256]u8 = undefined;
+    const path = try std.fmt.bufPrint(&path_buf, ".zig-cache/tmp/{s}/twinned", .{tmp.sub_path});
+    const core = try pardes.Pardes.init(std.testing.allocator, .{ .tty_only = true });
+    defer core.deinit();
+    const pane = try core.setTestFile("before\n");
+    core.gpa.free(pane.file.?.path);
+    pane.file.?.path = try core.gpa.dupe(u8, path);
+    try std.testing.expect(core.executeBuiltinLine(0, "Zerox"));
+    const twin: u8 = for (core.panes, 0..) |slot, id| {
+        if (id != 0) if (slot) |other| if (other.file != null) break @intCast(id);
+    } else return error.NoTwin;
+    const fd = init(true);
+    if (fd < 0) return error.NoWatcher;
+    defer _ = libc.close(fd);
+    var watches: Table = @splat(null);
+    defer watchPane(fd, &watches, twin, null, core.panes[twin].?.serial, .{ .text = 0 });
+    watchPane(fd, &watches, twin, path, core.panes[twin].?.serial, .{ .text = std.hash.Wyhash.hash(0, "before\n") });
+    // Edited in the first and saved: the file is the twins' text now.
+    pardes.panes.File.setContent(core, &pane.file.?, try core.gpa.dupe(u8, "after\n"));
+    try tmp.dir.writeFile(io, .{ .sub_path = "twinned", .data = "after\n" });
+    _ = reloadPane(core, io, &watches, twin, true);
+    const other = core.panes[twin].?;
+    try std.testing.expect(std.mem.indexOf(u8, other.msg[0..other.msg_len], "reloaded") == null);
+    try std.testing.expectEqualStrings("after\n", other.file.?.content);
+}
+
 test "ordinary file watches still reconcile changes between open and watch" {
     if (comptime !supported or !filesystem.platform_has_fs) return;
     const io = std.testing.io;
-- 
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