fix(tui_gateway): bind the branched agent to the parent profile's home + state.db

session.branch wrote the child ROW into the parent's profile db but
built the live agent with the launch defaults: _make_agent fell back to
_get_db() and no HERMES_HOME override was active. The branched agent's
own message flushes — and any later compression rotation it performed —
therefore landed back on the launch profile, splitting the lineage one
turn after the branch. Mirror session.create/resume: open the parent
profile's SessionDB for the agent and hold the home override across the
build, so config/skills/memory resolve to the profile too.

Spotted in #70605's sibling implementation of the same fix.

Co-authored-by: HexLab98 <liruixinch@outlook.com>

tests/test_tui_gateway_server.py

@@ -9151,11 +9151,12 @@ def test_session_branch_writes_to_parent_profile_db(monkeypatch, tmp_path):
     monkeypatch.setattr(server, "_get_db", lambda: LaunchDB())
     monkeypatch.setattr("hermes_state.SessionDB", ProfileDB)
     monkeypatch.setattr(server, "_claim_active_session_slot", lambda *a, **k: (None, None))
-    monkeypatch.setattr(
-        server,
-        "_make_agent",
-        lambda *a, **k: FakeAgent(),
-    )
+
+    def _fake_make_agent(*a, **k):
+        seen["agent_session_db"] = k.get("session_db")
+        return FakeAgent()
+
+    monkeypatch.setattr(server, "_make_agent", _fake_make_agent)
     monkeypatch.setattr(server, "_set_session_context", lambda *a, **k: {})
     monkeypatch.setattr(server, "_clear_session_context", lambda *a, **k: None)
     monkeypatch.setattr(server, "_resolve_model", lambda: "test-model")
@@ -9182,6 +9183,10 @@ def test_session_branch_writes_to_parent_profile_db(monkeypatch, tmp_path):
         assert seen.get("launch_create") is None
         child_sid = resp["result"]["session_id"]
         assert server._sessions[child_sid]["profile_home"] == str(profile_home)
+        # The branched AGENT must be bound to the parent profile's state.db —
+        # not just the row. Otherwise its own flushes (and a later compression
+        # rotation) land on the launch db, splitting the lineage again.
+        assert isinstance(seen.get("agent_session_db"), ProfileDB)
     finally:
         for k in list(server._sessions):
             server._sessions.pop(k, None)

tui_gateway/server.py

@@ -9734,27 +9734,48 @@ def _(rid, params: dict) -> dict:
                 lease.release()
             return _err(rid, 5008, f"branch failed: {e}")
     try:
-        tokens = _set_session_context(new_key)
+        # Bind the branched AGENT to the parent's profile, mirroring
+        # session.create/resume: home override so config/skills/memory resolve
+        # to the profile during the build, and the profile's own state.db
+        # handle so the live agent's message flushes — and any later
+        # compression rotation — persist there. Writing only the row to the
+        # parent's db while the agent stayed on the launch handle would
+        # recreate the cross-profile split one turn later.
+        parent_home = session.get("profile_home")
+        branch_db = None
+        if parent_home:
+            from hermes_state import SessionDB
+
+            branch_db = SessionDB(db_path=Path(parent_home) / "state.db")
+        home_token = (
+            set_hermes_home_override(parent_home) if parent_home else None
+        )
         try:
-            agent = _make_agent(
+            tokens = _set_session_context(new_key)
+            try:
+                agent = _make_agent(
+                    new_sid,
+                    new_key,
+                    session_id=new_key,
+                    session_db=branch_db,
+                    platform_override=source,
+                )
+            finally:
+                _clear_session_context(tokens)
+            _init_session(
                 new_sid,
                 new_key,
-                session_id=new_key,
-                platform_override=source,
+                agent,
+                list(history),
+                cols=session.get("cols", 80),
+                cwd=_session_cwd(session),
+                session_db=branch_db,
+                source=source,
+                profile_home=parent_home,
             )
         finally:
-            _clear_session_context(tokens)
-        parent_home = session.get("profile_home")
-        _init_session(
-            new_sid,
-            new_key,
-            agent,
-            list(history),
-            cols=session.get("cols", 80),
-            cwd=_session_cwd(session),
-            source=source,
-            profile_home=parent_home,
-        )
+            if home_token is not None:
+                reset_hermes_home_override(home_token)
         if new_sid in _sessions:
             _sessions[new_sid]["active_session_lease"] = lease
     except Exception as e: