Release v0.51.291 — Release JG (stage-s2 — preserve live turn content on switch-away #3668) (#3704)

* fix(#3668): snapshot live turn before stream teardown on session switch

The 'stays gone' variant: switching away from a streaming session during a quiet
window (mid tool-exec / silent thinking, between content SSE events) left a
stale/absent live-turn snapshot, so restoreLiveTurnHtmlForSession() failed on
switch-back and loadSession()'s fallback rebuilt with an empty appendThinking(),
permanently losing streamed thinking/tool content (only the elapsed clock
survived). closeLiveStream() now snapshots the live-turn DOM via
snapshotLiveTurnHtmlForSession(sessionId) BEFORE closing the source + tearing
down LIVE_STREAMS, so switch-back always restores the exact state shown at
switch-away. + regression test asserting snapshot precedes teardown.

* docs(changelog): v0.51.291 — Release JG (stage-s2, #3668)

---------

Co-authored-by: nesquena-hermes <[email protected]>

CHANGELOG.md

@@ -3,6 +3,11 @@
 
 ## [Unreleased]
 
+## [v0.51.291] — 2026-06-06 — Release JG (stage-s2 — preserve live turn content when switching away mid-stream)
+
+### Fixed
+- **Switching away from a streaming session no longer loses the in-progress thinking/tool content.** When you clicked to another chat while a session was streaming during a quiet window (mid tool-execution or silent reasoning, between content events) and then switched back, the live turn's tool cards and thinking could disappear permanently — only the elapsed-time clock survived — until the response finished and the transcript re-rendered from the server. Cause: the live-turn DOM snapshot was only captured on content/`tool_complete` SSE events, so the switch-away teardown could run with a stale-or-absent snapshot, and the switch-back fallback rebuilt an empty thinking card. `closeLiveStream()` now snapshots the live turn **before** tearing the stream down, so switching back restores the exact state shown at switch-away. (#3668)
+
 ## [v0.51.290] — 2026-06-06 — Release JF (stage-s1 — profile provider/model now respected in session resolution)
 
 ### Fixed

static/messages.js

@@ -787,6 +787,15 @@ function closeLiveStream(sessionId, streamId, source){
   if(!live) return;
   if(streamId&&live.streamId!==streamId) return;
   if(source&&live.source!==source) return;
+  // Snapshot the current live-turn DOM BEFORE tearing the stream down. The
+  // per-event snapshot (snapshotLiveTurn) only fires on content/tool_complete
+  // SSE events, so switching away during a quiet window (mid tool-exec, silent
+  // thinking) would leave a stale-or-absent snapshot — on switch-back
+  // restoreLiveTurnHtmlForSession() then fails and loadSession()'s fallback
+  // rebuilds with an EMPTY appendThinking(), permanently losing the streamed
+  // thinking/tool content (only the elapsed clock survives). Capturing here
+  // guarantees switch-back restores the exact state shown at switch-away. (#3668)
+  if(typeof snapshotLiveTurnHtmlForSession==='function') snapshotLiveTurnHtmlForSession(sessionId);
   try{live.source.close();}catch(_){ }
   delete LIVE_STREAMS[sessionId];
   // closeLiveStream() is called during session-switch teardown for any session

tests/test_issue3668_prompt_card_reshow_on_switch.py

@@ -229,3 +229,44 @@ def test_sse_initial_event_reshows_pending_prompt():
     assert "showApprovalForSession(sid" in MESSAGES_JS
     # the 'initial' SSE event specifically is wired (not only the live event).
     assert "addEventListener('initial'" in MESSAGES_JS
+
+
+def test_close_live_stream_snapshots_turn_before_teardown():
+    """#3668 'stays gone' variant: switching away from a streaming session during
+    a quiet window (mid tool-exec / silent thinking, between content SSE events)
+    must still preserve the live thinking/tool content on switch-back.
+
+    The per-event snapshot (snapshotLiveTurn) only fires on content/tool_complete
+    events, so closeLiveStream() — the switch-away teardown — must capture a DOM
+    snapshot BEFORE closing the source. Otherwise restoreLiveTurnHtmlForSession()
+    finds no/stale snapshot and loadSession()'s fallback rebuilds with an EMPTY
+    appendThinking(), permanently losing the streamed content (only the elapsed
+    clock survives — the reported signature).
+    """
+    # Extract the closeLiveStream body and assert the snapshot precedes teardown.
+    start = MESSAGES_JS.index("function closeLiveStream(")
+    brace = MESSAGES_JS.index("{", start)
+    depth = 0
+    body = ""
+    for i in range(brace, len(MESSAGES_JS)):
+        if MESSAGES_JS[i] == "{":
+            depth += 1
+        elif MESSAGES_JS[i] == "}":
+            depth -= 1
+            if depth == 0:
+                body = MESSAGES_JS[brace + 1 : i]
+                break
+    assert body, "closeLiveStream body not found"
+    snap_idx = body.find("snapshotLiveTurnHtmlForSession(sessionId)")
+    close_idx = body.find("live.source.close()")
+    delete_idx = body.find("delete LIVE_STREAMS[sessionId]")
+    assert snap_idx != -1, (
+        "closeLiveStream() must snapshot the live turn (snapshotLiveTurnHtmlForSession) "
+        "before tearing the stream down, or switch-away during a quiet window loses content (#3668)."
+    )
+    assert close_idx != -1 and snap_idx < close_idx, (
+        "the snapshot must be taken BEFORE live.source.close()."
+    )
+    assert delete_idx != -1 and snap_idx < delete_idx, (
+        "the snapshot must be taken BEFORE LIVE_STREAMS teardown."
+    )