fix: keep explicit forks out of lineage report

api/agent_sessions.py

@@ -199,6 +199,8 @@ def _is_continuation_session(parent: dict | None, child: dict | None) -> bool:
     """
     if not parent or not child:
         return False
+    if str(child.get('session_source') or '').strip().lower() == 'fork':
+        return False
     parent_source = str(parent.get('source') or '').strip().lower()
     child_source = str(child.get('source') or '').strip().lower()
     if parent_source and child_source and parent_source != child_source:
@@ -496,6 +498,7 @@ def read_session_lineage_report(db_path: Path, session_id: str | None, max_hops:
                 return _empty_lineage_report(sid)
 
             source_expr = _optional_col('source', session_cols)
+            session_source_expr = _optional_col('session_source', session_cols)
             title_expr = _optional_col('title', session_cols)
             started_expr = _optional_col('started_at', session_cols, '0')
             ended_expr = _optional_col('ended_at', session_cols)
@@ -509,6 +512,7 @@ def read_session_lineage_report(db_path: Path, session_id: str | None, max_hops:
                     f"""
                     SELECT s.id,
                            {source_expr},
+                           {session_source_expr},
                            {title_expr},
                            {started_expr},
                            {parent_expr},
@@ -551,6 +555,7 @@ def read_session_lineage_report(db_path: Path, session_id: str | None, max_hops:
                     f"""
                     SELECT s.id,
                            {source_expr},
+                           {session_source_expr},
                            {title_expr},
                            {started_expr},
                            {parent_expr},

tests/test_session_lineage_report.py

@@ -18,6 +18,7 @@ def _ensure_state_db(path):
         CREATE TABLE sessions (
             id TEXT PRIMARY KEY,
             source TEXT,
+            session_source TEXT,
             title TEXT,
             model TEXT,
             started_at REAL NOT NULL,
@@ -31,14 +32,14 @@ def _ensure_state_db(path):
     return conn
 
 
-def _insert_state_row(conn, sid, *, parent=None, ended_at=None, end_reason=None, started_at=None, source="webui"):
+def _insert_state_row(conn, sid, *, parent=None, ended_at=None, end_reason=None, started_at=None, source="webui", session_source=None):
     conn.execute(
         """
         INSERT INTO sessions
-        (id, source, title, model, started_at, message_count, parent_session_id, ended_at, end_reason)
-        VALUES (?, ?, ?, 'openai/gpt-5', ?, 2, ?, ?, ?)
+        (id, source, session_source, title, model, started_at, message_count, parent_session_id, ended_at, end_reason)
+        VALUES (?, ?, ?, ?, 'openai/gpt-5', ?, 2, ?, ?, ?)
         """,
-        (sid, source, sid.replace("_", " "), started_at or time.time(), parent, ended_at, end_reason),
+        (sid, source, session_source, sid.replace("_", " "), started_at or time.time(), parent, ended_at, end_reason),
     )
     conn.commit()
 
@@ -104,6 +105,32 @@ def test_lineage_report_keeps_cross_surface_parent_out_of_hidden_segments(tmp_pa
         conn.close()
 
 
+def test_lineage_report_keeps_explicit_forks_out_of_hidden_segments(tmp_path):
+    conn = _ensure_state_db(tmp_path / "state.db")
+    t0 = time.time() - 100
+    try:
+        _insert_state_row(conn, "lineage_report_root", started_at=t0, ended_at=t0 + 5, end_reason="compression")
+        _insert_state_row(
+            conn,
+            "lineage_report_fork",
+            parent="lineage_report_root",
+            started_at=t0 + 6,
+            session_source="fork",
+        )
+
+        report = agent_sessions.read_session_lineage_report(tmp_path / "state.db", "lineage_report_fork")
+
+        assert report["lineage_key"] == "lineage_report_fork"
+        assert report["tip_session_id"] == "lineage_report_fork"
+        assert report["total_segments"] == 1
+        assert [s["session_id"] for s in report["segments"]] == ["lineage_report_fork"]
+        assert report["segments"][0]["role"] == "tip"
+        assert report["children"] == []
+        assert report["manual_review"] is False
+    finally:
+        conn.close()
+
+
 def test_lineage_report_surfaces_non_continuation_children_without_mutation(tmp_path):
     conn = _ensure_state_db(tmp_path / "state.db")
     t0 = time.time() - 100