diff --git a/tests/tui_gateway/test_config_set_session_profile_scope.py b/tests/tui_gateway/test_config_set_session_profile_scope.py
new file mode 100644
index 0000000000..67c7a213e4
--- /dev/null
+++ b/tests/tui_gateway/test_config_set_session_profile_scope.py
@@ -0,0 +1,64 @@
+"""``config.set`` bound by ``session_id`` alone persists into the session's profile (issue #85669).
+
+Desktop app-global remote mode and the Ink TUI send ``config.set`` with ``session_id`` and no
+``profile`` param. The session record carries ``profile_home``; a write that ignores it lands in
+the launch profile's config.yaml while the focused profile silently keeps its old value.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+import yaml
+
+import tui_gateway.server as server
+
+
+def _write_cfg(home: Path, busy: str, approvals: str) -> None:
+    home.mkdir(parents=True, exist_ok=True)
+    (home / "config.yaml").write_text(
+        yaml.safe_dump({"display": {"busy_input_mode": busy}, "approvals": {"mode": approvals}}),
+        encoding="utf-8",
+    )
+
+
+def _read(home: Path) -> dict:
+    return yaml.safe_load((home / "config.yaml").read_text(encoding="utf-8")) or {}
+
+
+@pytest.fixture
+def homes(tmp_path, monkeypatch):
+    launch, worker = tmp_path / "launch", tmp_path / "profiles" / "worker"
+    _write_cfg(launch, "queue", "manual")
+    _write_cfg(worker, "queue", "manual")
+    monkeypatch.setenv("HERMES_HOME", str(launch))
+    monkeypatch.setattr(server, "_hermes_home", launch)
+    monkeypatch.setattr(server, "_cfg_cache", None)
+    monkeypatch.setattr(server, "_cfg_sig", None)
+    monkeypatch.setattr(server, "_cfg_path", None)
+    monkeypatch.setattr(server, "_emit", lambda *a, **k: None)
+    return launch, worker
+
+
+@pytest.mark.parametrize(
+    ("key", "value", "section", "field"),
+    [("busy", "steer", "display", "busy_input_mode"), ("approval_mode", "off", "approvals", "mode")],
+)
+def test_session_bound_config_set_writes_the_session_profile(homes, key, value, section, field):
+    launch, worker = homes
+    session = {"agent": None, "profile_home": str(worker), "session_key": "worker-session"}
+    with patch.dict(server._sessions, {"s-worker": session}, clear=False):
+        resp = server._methods["config.set"]("rid", {"session_id": "s-worker", "key": key, "value": value})
+    assert resp["result"]["value"] == value
+    assert _read(worker)[section][field] == value
+    assert _read(launch)[section][field] != value
+
+
+def test_unbound_config_set_still_writes_the_launch_profile(homes):
+    launch, worker = homes
+    resp = server._methods["config.set"]("rid", {"key": "busy", "value": "steer"})
+    assert resp["result"]["value"] == "steer"
+    assert _read(launch)["display"]["busy_input_mode"] == "steer"
+    assert _read(worker)["display"]["busy_input_mode"] == "queue"
diff --git a/tui_gateway/methods_config_set.py b/tui_gateway/methods_config_set.py
index 583112df83..eeb83c24e8 100644
--- a/tui_gateway/methods_config_set.py
+++ b/tui_gateway/methods_config_set.py
@@ -414,7 +414,10 @@ def _set_cwd(rid, params, key, value, session):
     if not os.path.isdir(cwd):
         return _err(rid, 4002, f"working directory does not exist: {raw}")
     _write_config_key("terminal.cwd", cwd)
-    os.environ["TERMINAL_CWD"] = cwd
+    # ``TERMINAL_CWD`` is the LAUNCH process's; a profile-bound session persists its cwd through its
+    # own config.yaml (written above under the session scope) and must not leak it into other profiles.
+    if not (isinstance(session, dict) and session.get("profile_home")):
+        os.environ["TERMINAL_CWD"] = cwd
     return _kv(rid, "terminal.cwd", cwd, cwd=cwd, branch=git_probe.branch(cwd))
 
 
diff --git a/tui_gateway/server.py b/tui_gateway/server.py
index 47c7c21f90..40bf6bcb17 100644
--- a/tui_gateway/server.py
+++ b/tui_gateway/server.py
@@ -553,10 +553,21 @@ def _profile_scoped(handler):
     systemd / ``op run`` injection); once multiplexing is active it binds its own scope from the env
     frozen at activation (``_session_profile_runtime_scope``), never ambient state a secondary context
     might have poisoned (#107422).
+
+    No ``profile`` param but a ``session_id`` naming a live session: that session's ``profile_home``
+    is the scope. The TUI and the Desktop's ambient dispatcher send session-bound RPCs with the
+    session id alone, so a ``config.set`` from a focused worker session otherwise persisted into the
+    LAUNCH profile's config.yaml while the worker's stayed unchanged (#85669).
     """
     def wrapper(rid, params):
-        home = _profile_home(params.get("profile") if isinstance(params, dict) else None)
-        with _session_profile_runtime_scope({"profile_home": str(home) if home else None}):
+        p = params if isinstance(params, dict) else {}
+        if str(p.get("profile") or "").strip():
+            home = _profile_home(p.get("profile"))
+            profile_home = str(home) if home else None
+        else:
+            session = _sessions.get(str(p.get("session_id") or ""))
+            profile_home = session.get("profile_home") if isinstance(session, dict) else None
+        with _session_profile_runtime_scope({"profile_home": profile_home or None}):
             return handler(rid, params)
     return wrapper