fix: clear runtime fields on compression snapshots

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Context-compression snapshot preservation now clears archived parent runtime fields (`active_stream_id`, `pending_user_message`, attachments, and start timestamp) before saving the old session id. This prevents a completed continuation session from leaving its parent looking permanently active/running after compression.
+
 ### Added
 
 - **PR #2099** by @dobby-d-elf — Adds an opt-in `Settings → Preferences → Fade text effect` toggle (off by default). When enabled, newly streamed output tokens are revealed through an adaptive playout buffer and animated with an opacity-only fade similar to ChatGPT and other frontier LLM apps. Implementation details: fade locked per stream to avoid mid-stream toggle rewind; reduced-motion users get non-animated text; live cursor hidden while fade is active; custom renderer on `streaming-markdown` parser wraps only newly-appended words; animated spans replace themselves with plain text on `animationend` (no long-lived wrapper buildup in long responses); unsafe streamed `href`/`src` values blocked in fade renderer `set_attr` path. Performance tuning: 200ms base fade duration scaling to 350ms for fast output, 16ms word stagger, 320ms done-drain wait cap, 160 wps visual cap, max 2-3 words/frame, brief pauses after sentence punctuation. Default-off means existing users see no change. 293-line regression test pinning the contract.

api/streaming.py

@@ -1862,6 +1862,37 @@ def _drop_checkpointed_current_user_from_context(messages, msg_text):
     return history
 
 
+def _save_pre_compression_snapshot(session, old_session_id):
+    """Persist the archived pre-compression session without live turn state.
+
+    During context compression the same ``Session`` object is reused for the new
+    continuation id.  Before the final continuation save clears
+    ``active_stream_id`` and ``pending_*``, we also preserve an old-id snapshot so
+    the full pre-compression transcript remains recoverable.  That archived
+    parent must not keep the current stream bookkeeping, otherwise the sidebar can
+    reopen the parent as a permanently running session while the child already
+    contains the completed answer.
+    """
+    saved_sid = session.session_id
+    saved_active_stream_id = getattr(session, 'active_stream_id', None)
+    saved_pending_user_message = getattr(session, 'pending_user_message', None)
+    saved_pending_attachments = list(getattr(session, 'pending_attachments', []) or [])
+    saved_pending_started_at = getattr(session, 'pending_started_at', None)
+    session.session_id = old_session_id
+    session.active_stream_id = None
+    session.pending_user_message = None
+    session.pending_attachments = []
+    session.pending_started_at = None
+    try:
+        session.save(touch_updated_at=False, skip_index=True)
+    finally:
+        session.session_id = saved_sid
+        session.active_stream_id = saved_active_stream_id
+        session.pending_user_message = saved_pending_user_message
+        session.pending_attachments = saved_pending_attachments
+        session.pending_started_at = saved_pending_started_at
+
+
 def _stream_writeback_is_current(session, stream_id):
     """Return True only while a worker still owns the session writeback.
 
@@ -3651,18 +3682,14 @@ def _run_agent_streaming(
                                 # before save then restored after — but the on-disk
                                 # copy persisted with parent=None, breaking
                                 # fork-of-fork lineage traversal.  (#2227 + #2223)
-                                saved_sid = s.session_id
-                                s.session_id = old_sid
                                 try:
-                                    s.save(touch_updated_at=False, skip_index=True)
+                                    _save_pre_compression_snapshot(s, old_sid)
                                     logger.info(
                                         "Preserved pre-compression session %s (%d messages) to disk",
                                         old_sid, len(s.messages),
                                     )
                                 except Exception:
                                     logger.debug("Failed to preserve pre-compression session file", exc_info=True)
-                                finally:
-                                    s.session_id = saved_sid
                         except OSError:
                             logger.debug("Could not read old session file before preservation")
                     # Always link the continuation session to its immediate predecessor

tests/test_compression_snapshot_runtime_clear.py

@@ -0,0 +1,47 @@
+from api import streaming
+
+
+class FakeSession:
+    def __init__(self):
+        self.session_id = "new_session"
+        self.parent_session_id = "original_parent"
+        self.active_stream_id = "live-stream"
+        self.pending_user_message = "current prompt"
+        self.pending_attachments = [{"name": "file.txt"}]
+        self.pending_started_at = 123.0
+        self.messages = [{"role": "user", "content": "current prompt"}]
+        self.saved_payload = None
+
+    def save(self, *, touch_updated_at=True, skip_index=False):
+        self.saved_payload = {
+            "session_id": self.session_id,
+            "parent_session_id": self.parent_session_id,
+            "active_stream_id": self.active_stream_id,
+            "pending_user_message": self.pending_user_message,
+            "pending_attachments": list(self.pending_attachments),
+            "pending_started_at": self.pending_started_at,
+            "touch_updated_at": touch_updated_at,
+            "skip_index": skip_index,
+        }
+
+
+def test_pre_compression_snapshot_clears_runtime_fields_while_restoring_continuation_state():
+    session = FakeSession()
+
+    streaming._save_pre_compression_snapshot(session, "old_session")
+
+    assert session.saved_payload == {
+        "session_id": "old_session",
+        "parent_session_id": "original_parent",
+        "active_stream_id": None,
+        "pending_user_message": None,
+        "pending_attachments": [],
+        "pending_started_at": None,
+        "touch_updated_at": False,
+        "skip_index": True,
+    }
+    assert session.session_id == "new_session"
+    assert session.active_stream_id == "live-stream"
+    assert session.pending_user_message == "current prompt"
+    assert session.pending_attachments == [{"name": "file.txt"}]
+    assert session.pending_started_at == 123.0