fix(mem0-agent): detached hooks lost their payload, so nothing was ever written

Observed live: real sessions flagged durable candidates (a preference, two
insights, a convention) but every session showed 'flush events: 0'. The manifest
backgrounded flush and assist-error with '( cmd &)', so the parent exited and
closed stdin before the child could read it -- the child then had no session_id,
fell back to 'no-session', and drained an empty buffer.

Now the CLI reads the payload itself and re-execs a detached worker with
start_new_session, so the hook still returns in ~0.27s. Verified end to end:
sent=1, session_state=created.

Also records a surface hint per event and shows it in 'sessions', since the
manifest pins MEM0_EDITOR to the same value on every client.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

integrations/mem0-agent/tests/test_cli.py

@@ -13,6 +13,8 @@ from mem0_agent.settings import SessionState, Settings
 class Args:
     def __init__(self, **kw):
         self.session_id = "sess-cli"
+        self.worker = True          # tests exercise the worker path directly
+        self.payload_file = None
         for k, v in kw.items():
             setattr(self, k, v)
 

integrations/mem0-agent/tests/test_generate.py

@@ -106,11 +106,18 @@ def test_user_prompt_submit_is_declared_local_only(spec, manifest):
     assert entry["background"] is False and entry["blocking"] is True
 
 
-def test_flush_and_assist_hooks_are_detached(spec, manifest):
+def test_write_hooks_are_not_shell_backgrounded(spec, manifest):
+    """These hooks must NOT be wrapped in `( ... &)`.
+
+    A shell-backgrounded hook loses stdin the instant the parent exits, so the child
+    sees no session_id and no transcript_path and drains the wrong buffer -- observed
+    live as flagged candidates that were never written. The CLI now reads the payload
+    first and re-execs itself detached, so the hook still returns in milliseconds.
+    """
     for event in ("PostToolUse", "Stop", "PreCompact", "SessionEnd"):
         command = manifest["hooks"][event][0]["hooks"][0]["command"]
-        assert command.startswith("(") and command.endswith("&)"), event
-        assert ">/dev/null" in command, event
+        assert not command.strip().endswith("&)"), f"{event} must not be backgrounded by the shell"
+        assert "mem0-agent" in command, event
 
 
 def test_editor_env_is_pinned(manifest):