Add run journal replay timeline parity checks

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- **PR TBD** by @franksong2702 (refs #2376, refs #1925, refs #2283, refs #2361, refs #2363) — Adds a focused run-journal replay parity check for long tool-heavy turns. The frontend regression coverage now pins that replayed `reasoning`, `interim_assistant`, `tool`, `tool_complete`, `compressing`, `compressed`, `metering`, and terminal events enter the same EventSource timeline handlers as live streaming, and that each user-visible long-task event advances the replay cursor to avoid duplicate replay. The run-state consistency RFC now calls out live/replay timeline parity explicitly.
+
 ## [v0.51.74] — 2026-05-16 — Release AX (stage-367 — 4-PR safe-lane batch — #2362 table-cell spacing + #2363 run-state-consistency RFC + #2365 custom_providers list-format + #2367 settings sidebar i18n)
 
 ### Added

docs/rfcs/webui-run-state-consistency-contract.md

@@ -78,7 +78,10 @@ while WebUI still has multiple overlapping state stores.
    assistant just acted.
 5. **Replay is idempotent.** Replaying a run from a cursor must not duplicate
    transcript rows, thinking content, interim assistant text, tool cards, or
-   compression cards.
+   compression cards. Replayed long-task events should enter the same
+   browser-facing timeline renderer as live SSE events so recovery does not
+   downgrade a structured Thinking / progress / tool / compression turn into a
+   separate flattened presentation.
 6. **Compression is not current intent.** Automatic compression summaries and
    reference cards are recovery/handoff material. They must not be treated as a
    new user request, active-turn content, or the default visible explanation for
@@ -102,6 +105,8 @@ context reconstruction, or session metadata:
 - What happens after browser refresh, session switch, SSE reconnect, and WebUI
   restart?
 - Does replay rebuild the same scene without duplicates?
+- Does replay use the same timeline-rendering path as live SSE for thinking,
+  interim assistant text, tool cards, compression cards, and terminal states?
 - Can this change move a session in the sidebar without meaningful user or
   assistant activity?
 - Can automatic compression or recovery text become visible active-turn content?
@@ -147,4 +152,3 @@ The two documents should be read together:
 4. If #1925 introduces a new adapter-backed runtime layer, update this RFC or
    replace it with the accepted implementation contract so these invariants do
    not live only in historical discussion.
-

tests/test_run_journal_frontend_static.py

@@ -35,3 +35,60 @@ def test_frontend_replay_cursor_uses_eventsource_last_event_id():
     assert "source.addEventListener(_runJournalEventName,_rememberRunJournalCursor)" in MESSAGES_SRC
     assert "after_seq=${encodeURIComponent(String(_runJournalReplayAfterSeq()))}" in MESSAGES_SRC
     assert "after_seq=0" not in MESSAGES_SRC
+
+
+def test_replayed_long_task_events_enter_the_same_live_timeline_handlers():
+    """Run-journal replay must not grow a parallel long-task renderer.
+
+    The run-state consistency contract depends on replayed journal events
+    flowing through the same EventSource handlers as live streams.  Otherwise a
+    live long task can render as Thinking -> progress text -> tool cards, while
+    the same journaled event sequence replays as a flattened or reordered scene.
+    """
+    wire_pos = MESSAGES_SRC.index("function _wireSSE(source)")
+    wire_block = MESSAGES_SRC[wire_pos : MESSAGES_SRC.index("async function _restoreSettledSession", wire_pos)]
+    replay_events = [
+        "reasoning",
+        "interim_assistant",
+        "tool",
+        "tool_complete",
+        "compressing",
+        "compressed",
+        "metering",
+        "done",
+        "apperror",
+    ]
+
+    for event_name in replay_events:
+        assert f"source.addEventListener('{event_name}'" in wire_block, (
+            f"{event_name} must be handled by the shared live/replay SSE pipeline"
+        )
+
+    assert "updateThinking(" in wire_block, "reasoning replay should use the live Thinking card path"
+    assert "appendLiveToolCard(tc)" in wire_block, "tool replay should use live tool-card rendering"
+    assert "setCompressionUi({" in wire_block, "compression replay should use the compression card path"
+    assert "_runJournalReplayParams()" in MESSAGES_SRC, "replay attachments should enter _wireSSE via EventSource"
+
+
+def test_run_journal_cursor_tracks_every_long_task_timeline_event():
+    """Every user-visible long-task event needs cursor tracking for parity replay."""
+    cursor_loop_pos = MESSAGES_SRC.index("for(const _runJournalEventName of [")
+    cursor_loop = MESSAGES_SRC[cursor_loop_pos : cursor_loop_pos + 700]
+    timeline_events = [
+        "token",
+        "interim_assistant",
+        "reasoning",
+        "tool",
+        "tool_complete",
+        "compressing",
+        "compressed",
+        "metering",
+        "done",
+        "apperror",
+        "cancel",
+    ]
+
+    for event_name in timeline_events:
+        assert f"'{event_name}'" in cursor_loop, (
+            f"{event_name} must advance the replay cursor to avoid duplicate timeline replay"
+        )