Merge remote-tracking branch 'origin/master' into paperclip/pr-6222

CHANGELOG.md

@@ -11,6 +11,8 @@
 
 ### Fixed
 
+- **Reopening a WebUI tab after a large active session is fast again, even when the session has few messages but large tool outputs.** The reconnect display-path tail optimization only fired based on message *count*, so a session with a handful of messages but multi-MB tool-call JSON forced a slow full-scan merge (bootstrap could take tens of seconds). The optimization now also fires when the session sidecar file exceeds 500 KB, regardless of message count — the same messages are returned (verified: identical message set, count, offset, and truncation metadata), just via the fast path. Thanks @webtecnica. (#6260)
+
 - **OIDC allowlist values containing spaces (e.g. a group named `Hermes Users`) are no longer split into separate entries.** The allowlist parser split comma-separated values on all whitespace, so a multi-word group/user name became two spurious entries. Allowlist parsing now splits only on commas/newlines (multi-word values stay intact and match their exact signed claim — strictly tightening, no security loosening), while OAuth **scope** parsing keeps its space-delimited behavior per RFC 6749 §3.3. A blank allowlist entry no longer bricks an OIDC-only deployment. Thanks @webtecnica. (#6244)
 
 - **`/sessions` and `/resume` typed in the composer now open the session browser instead of being sent as chat text.** Both commands appeared in the slash-command autocomplete (they're exposed by `/api/commands`) but the WebUI send-time dispatch didn't handle them, so they were posted to the agent as plain text. They now open the native WebUI session browser and clear the composer — on desktop and (via the mobile-aware opener) on phone-width layouts. Thanks @webtecnica. (#6245, #6224)

api/routes.py

@@ -8522,6 +8522,10 @@ def _parse_msg_limit(raw):
     return max(1, min(value, _MAX_MSG_LIMIT))
 
 
+# If a sidecar JSON file exceeds this threshold, the display-path tail
+# optimization fires regardless of message count.  Sessions with few messages
+# but large tool outputs (multi-MB JSON) should not force a full-scan merge.
+_SIDECAR_BYTE_TAIL_THRESHOLD = 500_000  # 500 KB
 # Defensive row backstop for the GET /api/session display path's state.db read.
 # This is NOT a semantic window (the display window counts visible rows
 # post-reconciliation via _message_window_for_display); it is a safety net so a
@@ -8641,6 +8645,16 @@ def _limited_webui_messages_for_display_with_sidecar(session, sidecar_messages,
     )
 
 
+def _sidecar_file_exceeds_threshold(session_id, threshold_bytes) -> bool:
+    """Check if the sidecar JSON file for ``session_id`` exceeds ``threshold_bytes``."""
+    from api.config import SESSION_DIR
+    try:
+        p = SESSION_DIR / f"{session_id}.json"
+        return os.path.isfile(p) and os.path.getsize(p) > threshold_bytes
+    except Exception:
+        return False
+
+
 def _state_db_since_timestamp_for_limited_display(session, msg_limit, msg_before=None):
     """Return (timestamp floor, sidecar messages) for bounded state.db tail reads.
 
@@ -8671,7 +8685,9 @@ def _state_db_since_timestamp_for_limited_display(session, msg_limit, msg_before
         return None, sidecar_messages
     raw_budget = max(300, limit * 10)
     if len(sidecar_messages) <= raw_budget:
-        return None, sidecar_messages
+        _sid = getattr(session, "session_id", "") or ""
+        if not _sid or not _sidecar_file_exceeds_threshold(_sid, _SIDECAR_BYTE_TAIL_THRESHOLD):
+            return None, sidecar_messages
 
     floor = min(sidecar_timestamps[-raw_budget:])
     sidecar_before_count = sum(1 for ts in sidecar_timestamps if ts < floor)