fix: keep configure_structured_logging working when no root handler exists

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/praisonai-agents/praisonaiagents/_logging.py

@@ -143,10 +143,16 @@ def configure_root_logger():
     
     Uses standard StreamHandler by default for performance.
     RichHandler is only used when LOGLEVEL=DEBUG for better debugging experience.
-    Does nothing if the host application already configured the root logger.
+    Does nothing if the host application already configured the root logger,
+    or when ``LOGLEVEL`` is not set explicitly.
     """
     if _host_configured_logging():
         return
+    if 'LOGLEVEL' not in os.environ:
+        # A library must not install root handlers by default: that turns the
+        # host's later logging.basicConfig() into a no-op. Without handlers,
+        # WARNING+ records still reach stderr via logging.lastResort.
+        return
 
     loglevel = os.environ.get('LOGLEVEL', 'WARNING').upper()
     
@@ -238,8 +244,13 @@ def configure_structured_logging():
     """
     if os.environ.get('PRAISONAI_STRUCTURED_LOGS', '').lower() == 'true':
         structured_formatter = StructuredFormatter()
+        root = logging.getLogger()
+        # Explicit opt-in: install a root handler if none exists (the SDK no
+        # longer installs one on import unless LOGLEVEL is set).
+        if not root.handlers:
+            root.addHandler(logging.StreamHandler())
         # Reconfigure the root logger handler so propagating loggers get JSON output
-        for handler in logging.getLogger().handlers:
+        for handler in root.handlers:
             handler.setFormatter(structured_formatter)
         # Also reconfigure any praisonaiagents loggers that have their own handlers
         for logger_name in logging.Logger.manager.loggerDict:

src/praisonai-agents/tests/unit/test_issue_6294_logging.py

@@ -0,0 +1,36 @@
+"""Regression tests for issue #6294: no root log handler by default."""
+import logging
+
+
+def test_import_leaves_root_logging_to_host(monkeypatch):
+    from praisonaiagents import _logging
+
+    root = logging.getLogger()
+    monkeypatch.delenv("LOGLEVEL", raising=False)
+    monkeypatch.setattr(root, "handlers", [])
+    _logging.configure_root_logger()
+    assert root.handlers == []
+
+
+def test_explicit_loglevel_still_installs_root_handler(monkeypatch):
+    from praisonaiagents import _logging
+
+    root = logging.getLogger()
+    monkeypatch.setenv("LOGLEVEL", "WARNING")
+    monkeypatch.setattr(root, "handlers", [])
+    monkeypatch.setattr(root, "level", root.level)
+    _logging.configure_root_logger()
+    assert root.handlers
+
+
+def test_structured_logging_works_without_loglevel(monkeypatch):
+    from praisonaiagents import _logging
+
+    root = logging.getLogger()
+    monkeypatch.delenv("LOGLEVEL", raising=False)
+    monkeypatch.setenv("PRAISONAI_STRUCTURED_LOGS", "true")
+    monkeypatch.setattr(root, "handlers", [])
+    _logging.configure_root_logger()
+    _logging.configure_structured_logging()
+    assert len(root.handlers) == 1
+    assert isinstance(root.handlers[0].formatter, _logging.StructuredFormatter)