feat(cli): add on_session_finalize and on_session_reset plugin hooks

Plugins can now subscribe to session boundary events via
ctx.register_hook('on_session_finalize', ...) and
ctx.register_hook('on_session_reset', ...).

on_session_finalize — fires during CLI exit (/quit, Ctrl-C) and
before /new or /reset, giving plugins a chance to flush or clean up.

on_session_reset — fires after a new session is created via
/new or /reset, so plugins can initialize per-session state.

Closes #5592

cli.py

@@ -612,6 +612,11 @@ def _run_cleanup():
         pass
     # Shut down memory provider (on_session_end + shutdown_all) at actual
     # session boundary — NOT per-turn inside run_conversation().
+    try:
+        from hermes_cli.plugins import invoke_hook as _invoke_hook
+        _invoke_hook("on_session_finalize", session_id=_active_agent_ref.session_id if _active_agent_ref else None, platform="cli")
+    except Exception:
+        pass
     try:
         if _active_agent_ref and hasattr(_active_agent_ref, 'shutdown_memory_provider'):
             _active_agent_ref.shutdown_memory_provider(
@@ -3314,6 +3319,22 @@ class HermesCLI:
         flush_tool_summary()
         print()
     
+    def _notify_session_boundary(self, event_type: str) -> None:
+        """Fire a session-boundary plugin hook (on_session_finalize or on_session_reset).
+
+        Non-blocking — errors are caught and logged.  Safe to call from any
+        lifecycle point (shutdown, /new, /reset).
+        """
+        try:
+            from hermes_cli.plugins import invoke_hook as _invoke_hook
+            _invoke_hook(
+                event_type,
+                session_id=self.agent.session_id if self.agent else None,
+                platform=getattr(self, "platform", None) or "cli",
+            )
+        except Exception:
+            pass
+
     def new_session(self, silent=False):
         """Start a fresh session with a new session ID and cleared agent state."""
         if self.agent and self.conversation_history:
@@ -3321,6 +3342,10 @@ class HermesCLI:
                 self.agent.flush_memories(self.conversation_history)
             except (Exception, KeyboardInterrupt):
                 pass
+            self._notify_session_boundary("on_session_finalize")
+        elif self.agent:
+            # First session or empty history — still finalize the old session
+            self._notify_session_boundary("on_session_finalize")
 
         old_session_id = self.session_id
         if self._session_db and old_session_id:
@@ -3365,6 +3390,7 @@ class HermesCLI:
                     )
                 except Exception:
                     pass
+            self._notify_session_boundary("on_session_reset")
 
         if not silent:
             print("(^_^)v New session started!")

hermes_cli/plugins.py

@@ -61,6 +61,8 @@ VALID_HOOKS: Set[str] = {
     "post_api_request",
     "on_session_start",
     "on_session_end",
+    "on_session_finalize",
+    "on_session_reset",
 }
 
 ENTRY_POINTS_GROUP = "hermes_agent.plugins"

tests/test_session_boundary_hooks.py

@@ -0,0 +1,66 @@
+import pytest
+from unittest.mock import MagicMock, patch
+from hermes_cli.plugins import VALID_HOOKS, PluginManager
+import os
+import shutil
+import tempfile
+from cli import HermesCLI
+
+
+def test_session_hooks_in_valid_hooks():
+    """Verify on_session_finalize and on_session_reset are registered as valid hooks."""
+    assert "on_session_finalize" in VALID_HOOKS
+    assert "on_session_reset" in VALID_HOOKS
+
+
+@patch("hermes_cli.plugins.invoke_hook")
+def test_session_finalize_on_reset(mock_invoke_hook):
+    """Verify on_session_finalize fires when /new or /reset is used."""
+    cli = HermesCLI()
+    cli.agent = MagicMock()
+    cli.agent.session_id = "test-session-id"
+
+    # Simulate /new command which triggers on_session_finalize for the old session
+    cli.new_session(silent=True)
+
+    # Check if on_session_finalize was called for the old session
+    mock_invoke_hook.assert_any_call(
+        "on_session_finalize", session_id="test-session-id", platform="cli"
+    )
+    # Check if on_session_reset was called for the new session
+    mock_invoke_hook.assert_any_call(
+        "on_session_reset", session_id=cli.session_id, platform="cli"
+    )
+
+
+@patch("hermes_cli.plugins.invoke_hook")
+def test_session_finalize_on_cleanup(mock_invoke_hook):
+    """Verify on_session_finalize fires during CLI exit cleanup."""
+    import cli as cli_mod
+
+    mock_agent = MagicMock()
+    mock_agent.session_id = "cleanup-session-id"
+    cli_mod._active_agent_ref = mock_agent
+    cli_mod._cleanup_done = False
+
+    cli_mod._run_cleanup()
+
+    mock_invoke_hook.assert_any_call(
+        "on_session_finalize", session_id="cleanup-session-id", platform="cli"
+    )
+
+
+@patch("hermes_cli.plugins.invoke_hook")
+def test_hook_errors_are_caught(mock_invoke_hook):
+    """Verify hook exceptions are caught and don't crash the agent."""
+    mgr = PluginManager()
+
+    # Register a hook that raises
+    def bad_callback(**kwargs):
+        raise Exception("Hook failed")
+
+    mgr._hooks["on_session_finalize"] = [bad_callback]
+
+    # This should not raise
+    results = mgr.invoke_hook("on_session_finalize", session_id="test", platform="cli")
+    assert results == []