From e5ff61219729d906ab94a2ca3b5cc8bd186227a3 Mon Sep 17 00:00:00 2001
From: enzotar <enzotar3000@gmail.com>
Date: Wed, 25 Feb 2026 21:58:14 -0800
Subject: [PATCH] feat: per-signal version counters for conflict resolution

- _signalVersions: monotonic counter per signal, incremented on each local mutation
- Diffs include _v: {name: version} for version comparison
- _applyRemoteDiff only applies if remote version >= local version
- Prevents stale overwrites when both devices edit simultaneously
- onopen snapshot includes version map for late-joiner consistency
---
 compiler/ds-codegen/src/js_emitter.rs | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/compiler/ds-codegen/src/js_emitter.rs b/compiler/ds-codegen/src/js_emitter.rs
index edd06a9..db38a59 100644
--- a/compiler/ds-codegen/src/js_emitter.rs
+++ b/compiler/ds-codegen/src/js_emitter.rs
@@ -1818,11 +1818,13 @@ const DS = (() => {
 
   // ── Signal registry for bidirectional sync ──
   var _signalRegistry = {};
+  var _signalVersions = {}; // per-signal version counters for conflict resolution
   var _applyingRemoteDiff = false;
   var _peerId = Math.random().toString(36).substr(2, 8); // unique per client
 
   function _registerSignal(name, sig) {
     _signalRegistry[name] = sig;
+    _signalVersions[name] = 0;
   }
 
   function _applyRemoteDiff(json) {
@@ -1830,12 +1832,18 @@ const DS = (() => {
       var data = JSON.parse(json);
       // Ignore our own diffs echoed back by the relay
       if (data._pid === _peerId) return;
+      var versions = data._v || {};
       _applyingRemoteDiff = true;
       for (var name in data) {
-        if (name === '_pid') continue;
+        if (name === '_pid' || name === '_v') continue;
         var sig = _signalRegistry[name];
-        if (sig) {
+        if (!sig) continue;
+        var remoteV = versions[name] || 0;
+        var localV = _signalVersions[name] || 0;
+        // Only apply if remote version >= local version (last-write-wins)
+        if (remoteV >= localV) {
           sig.value = data[name];
+          _signalVersions[name] = remoteV;
         }
       }
       flush();
@@ -1869,11 +1877,12 @@ const DS = (() => {
     _streamWs.onclose = function() { setTimeout(function() { _initStream(url, mode); }, 2000); };
     _streamWs.onopen = function() {
       console.log('[ds-stream] Peer connected:', peerUrl);
-      // Broadcast full state snapshot so other peers can sync
-      var fullState = { _pid: _peerId };
+      // Broadcast full state snapshot with versions so other peers can sync
+      var fullState = { _pid: _peerId, _v: {} };
       for (var name in _signalRegistry) {
         var sig = _signalRegistry[name];
         fullState[name] = (typeof sig === 'object' && sig !== null && '_value' in sig) ? sig._value : sig;
+        fullState._v[name] = _signalVersions[name] || 0;
       }
       _streamSend(0x31, 0, new TextEncoder().encode(JSON.stringify(fullState)));
     };
@@ -1896,7 +1905,10 @@ const DS = (() => {
   function _streamDiff(name, value) {
     if (!_streamWs || _streamWs.readyState !== 1 || _streamMode !== 'signal') return;
     if (_applyingRemoteDiff) return; // prevent echo loops
-    var obj = { _pid: _peerId };
+    // Increment version for conflict resolution
+    _signalVersions[name] = (_signalVersions[name] || 0) + 1;
+    var obj = { _pid: _peerId, _v: {} };
+    obj._v[name] = _signalVersions[name];
     obj[name] = (typeof value === 'object' && value !== null && 'value' in value) ? value.value : value;
     _streamSend(0x31, 0, new TextEncoder().encode(JSON.stringify(obj)));
   }