fix: exclude hidden snapshots from pin quota

api/routes.py

@@ -99,6 +99,25 @@ def _session_field(session, field, default=None):
     return getattr(session, field, default)
 
 
+def _session_counts_toward_pin_quota(session) -> bool:
+    """Return True when a pinned session should consume visible pin quota."""
+    if not _session_field(session, "pinned", False):
+        return False
+    if _session_field(session, "archived", False):
+        return False
+    if isinstance(session, dict):
+        row = session
+    elif hasattr(session, "compact"):
+        row = session.compact()
+    else:
+        row = {
+            "pre_compression_snapshot": _session_field(session, "pre_compression_snapshot", False),
+            "source_tag": _session_field(session, "source_tag", None),
+            "default_hidden": _session_field(session, "default_hidden", False),
+        }
+    return not _hide_from_default_sidebar(row)
+
+
 # ── Profile-scoped session/project filtering (#1611, #1614) ────────────────
 #
 # Sessions and projects are stored in the WebUI sidecar without per-row
@@ -2730,6 +2749,7 @@ from api.models import (
     merge_session_messages_append_only,
     _session_message_merge_key,
     _is_empty_partial_activity_message,
+    _hide_from_default_sidebar,
     prune_session_from_index,
     ensure_cron_project,
     is_cron_session,
@@ -6509,7 +6529,7 @@ def handle_post(handler, parsed) -> bool:
             # so must run outside our own LOCK acquire below).
             persisted_pinned_ids = {
                 _session_field(existing, "session_id", None) for existing in all_sessions()
-                if _session_field(existing, "pinned", False) and not _session_field(existing, "archived", False)
+                if _session_counts_toward_pin_quota(existing)
             }
             with LOCK:
                 # Final authoritative count: merge persisted-pinned with the
@@ -6519,7 +6539,7 @@ def handle_post(handler, parsed) -> bool:
                 pinned_ids = set(persisted_pinned_ids)
                 pinned_ids.update(
                     sid for sid, existing in SESSIONS.items()
-                    if getattr(existing, "pinned", False) and not getattr(existing, "archived", False)
+                    if _session_counts_toward_pin_quota(existing)
                 )
                 pinned_ids.discard(body["session_id"])
                 pinned_sessions_limit = int(load_settings().get("pinned_sessions_limit", 3) or 3)

api/streaming.py

@@ -2286,8 +2286,10 @@ def _preserve_pre_compression_snapshot(s, old_sid: str) -> None:
             # pre-existing parent_session_id lineage.
             saved_sid = s.session_id
             saved_snapshot = bool(getattr(s, 'pre_compression_snapshot', False))
+            saved_pinned = bool(getattr(s, 'pinned', False))
             s.session_id = old_sid
             s.pre_compression_snapshot = True
+            s.pinned = False
             # Stage-359 / PR #2295: clear runtime stream-state fields on the
             # archived snapshot so the sidebar does not reopen the parent as
             # a permanently-running session while the child already holds the
@@ -2314,6 +2316,7 @@ def _preserve_pre_compression_snapshot(s, old_sid: str) -> None:
             finally:
                 s.session_id = saved_sid
                 s.pre_compression_snapshot = saved_snapshot
+                s.pinned = saved_pinned
                 s.active_stream_id = saved_active_stream_id
                 s.pending_user_message = saved_pending_user_message
                 s.pending_attachments = saved_pending_attachments
@@ -2326,6 +2329,7 @@ def _preserve_pre_compression_snapshot(s, old_sid: str) -> None:
         snapshot = Session.load(old_sid)
         if snapshot:
             snapshot.pre_compression_snapshot = True
+            snapshot.pinned = False
             # Stage-359 Opus SHOULD-FIX: clear runtime fields on the loaded
             # snapshot too. If the disk snapshot was last persisted while the
             # parent was live, it could carry a stale active_stream_id /