gate-fix #5466: stamp anchor attrs on incremental node + teardown on all terminal paths

Codex gate findings (2 SILENT, both fixed):
- ui.js: incremental prose node now flows through the shared row-decoration
  block (data-anchor-scene-row/-row-id/-row-role/-source-event-type) instead of
  returning early, so live incremental rows keep the identity attrs the scene
  reconciler matches on.
- messages.js: _cancelThrottledSnapshotTimer() + _clearAnchorProseIncrementalNode()
  now run on apperror, cancel, _handleStreamError, and _restoreSettledSession
  terminal paths (previously only fallback/done/stream_end) — closes the
  snapshot-timer/anchor-cache/window-global teardown gap.
- test: extend test_messages_js_stream_perf_cleanup_lifecycle to pin teardown on
  all four additional terminal paths.

CORE equivalence (Codex flagged smd != renderMd): reconciled — Opus's 1498-frame
harness against real smd.min.js proves incremental-smd == whole-smd byte-identical;
live-smd-vs-renderMd difference is the already-shipped fidelity model (main live
body streams smd, settles renderMd), and the incremental path is gated on !settled
so settled DOM still comes from renderMd. Not a regression.

static/messages.js

@@ -5510,6 +5510,8 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
       _clearStreamEndRecovery();
       _terminalStateReached=true;
       if(_persistTimer){clearTimeout(_persistTimer);_persistTimer=null;}
+      _cancelThrottledSnapshotTimer();
+      _clearAnchorProseIncrementalNode();
       _streamFinalized=true;
       _cancelAnimationFramePendingStreamRender();
       _streamFadeCleanupReduceMotionListener();
@@ -5711,6 +5713,8 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
       _clearStreamEndRecovery();
       _terminalStateReached=true;
       if(_persistTimer){clearTimeout(_persistTimer);_persistTimer=null;}
+      _cancelThrottledSnapshotTimer();
+      _clearAnchorProseIncrementalNode();
       _streamFinalized=true;
       _cancelAnimationFramePendingStreamRender();
       _streamFadeCleanupReduceMotionListener();
@@ -5861,6 +5865,8 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
       if(!session) return returnStatus?'missing':false;
       if(session.active_stream_id||session.pending_user_message) return returnStatus?'active':false;
       if(_persistTimer){clearTimeout(_persistTimer);_persistTimer=null;}
+      _cancelThrottledSnapshotTimer();
+      _clearAnchorProseIncrementalNode();
       _streamFinalized=true;
       _cancelAnimationFramePendingStreamRender();
       _streamFadeCleanupReduceMotionListener();
@@ -5955,6 +5961,8 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
     // Opus review Q1: mirror done/apperror/cancel finalization so any pending rAF
     // cannot fire after renderMessages() has settled the DOM with the error message.
     if(_persistTimer){clearTimeout(_persistTimer);_persistTimer=null;}
+    _cancelThrottledSnapshotTimer();
+    _clearAnchorProseIncrementalNode();
     _streamFinalized=true;
     _cancelAnimationFramePendingStreamRender();
     _streamFadeCleanupReduceMotionListener();

static/ui.js

@@ -10538,13 +10538,19 @@ function _anchorSceneNodeForRow(row, opts){
     const proseKey=row.local_id||row.row_id||'';
     if(!settled && proseKey && typeof window.__anchorProseIncrementalNode==='function'){
       const inc=window.__anchorProseIncrementalNode(proseKey,text);
-      if(inc) return inc;
+      // Route the incremental node through the shared row-decoration block below
+      // (data-anchor-scene-row / -row-id / -row-role / -source-event-type) instead
+      // of returning early — otherwise live incremental prose rows lose the
+      // identity attributes the scene reconciler matches on. (Codex gate #5466)
+      if(inc){ node=inc; }
+    }
+    if(!node){
+      node=document.createElement('div');
+      node.className='assistant-segment';
+      node.setAttribute('data-anchor-scene-prose','1');
+      node.dataset.rawText=text;
+      node.innerHTML=`<div class="msg-body">${renderMd?renderMd(text):esc(text)}</div>`;
     }
-    node=document.createElement('div');
-    node.className='assistant-segment';
-    node.setAttribute('data-anchor-scene-prose','1');
-    node.dataset.rawText=text;
-    node.innerHTML=`<div class="msg-body">${renderMd?renderMd(text):esc(text)}</div>`;
   }else if(row.role==='thinking'){
     if(window._showThinking===false) return null;
     const text=String(row.text||row.thinking&&row.thinking.text||'').trim();

tests/test_regressions.py

@@ -1062,6 +1062,30 @@ def test_messages_js_stream_perf_cleanup_lifecycle(cleanup_test_sessions):
     assert "_cancelThrottledSnapshotTimer();" in done_body
     assert "_clearAnchorProseIncrementalNode();" in done_body
 
+    # #5466 Codex gate: the snapshot/anchor cleanup must run on EVERY terminal
+    # path, not just fallback/done/stream_end — otherwise a timer/cache/global
+    # survives the turn on apperror, cancel, stream-error, and the settled-session
+    # recovery path (the PR's own stated teardown invariant).
+    def _terminal_body(anchor, end_marker):
+        a = src.find(anchor)
+        assert a >= 0, f"missing terminal handler: {anchor}"
+        b = src.find(end_marker, a)
+        assert b > a, f"could not bound terminal handler: {anchor}"
+        return src[a:b]
+
+    apperror_body = _terminal_body("source.addEventListener('apperror'", "_streamFadeCleanupReduceMotionListener();")
+    assert "_cancelThrottledSnapshotTimer();" in apperror_body and "_clearAnchorProseIncrementalNode();" in apperror_body, \
+        "apperror terminal handler must tear down the snapshot timer + anchor prose cache"
+    cancel_body = _terminal_body("source.addEventListener('cancel'", "_streamFadeCleanupReduceMotionListener();")
+    assert "_cancelThrottledSnapshotTimer();" in cancel_body and "_clearAnchorProseIncrementalNode();" in cancel_body, \
+        "cancel terminal handler must tear down the snapshot timer + anchor prose cache"
+    stream_error_body = _terminal_body("function _handleStreamError(source)", "_streamFadeCleanupReduceMotionListener();")
+    assert "_cancelThrottledSnapshotTimer();" in stream_error_body and "_clearAnchorProseIncrementalNode();" in stream_error_body, \
+        "_handleStreamError must tear down the snapshot timer + anchor prose cache"
+    restore_body = _terminal_body("async function _restoreSettledSession(source", "_cancelAnimationFramePendingStreamRender();")
+    assert "_cancelThrottledSnapshotTimer();" in restore_body and "_clearAnchorProseIncrementalNode();" in restore_body, \
+        "_restoreSettledSession terminal recovery must tear down the snapshot timer + anchor prose cache"
+
 
 def test_messages_js_finalizes_thinking_card_before_tool_card(cleanup_test_sessions):
     """R19e: later reasoning after a tool call must render in a fresh Worklog