Emit configuration span after logfire.configure()

logfire/_internal/config.py

@@ -1352,6 +1352,30 @@ def fix_pid():  # pragma: no cover
 
             self._ensure_flush_after_aws_lambda()
 
+        self._emit_configuration_span()
+
+    def _emit_configuration_span(self) -> None:
+        """Emit a span describing the active Logfire configuration and installed packages."""
+        from logfire._internal.collect_system_info import collect_package_info
+        from logfire._internal.main import Logfire
+
+        with handle_internal_errors:
+            config_dict: dict[str, Any] = {}
+            for f in dataclasses.fields(_LogfireConfigData):
+                value = getattr(self, f.name, None)
+                if f.name in ('token', 'api_key') and value:
+                    config_dict[f.name] = '[REDACTED]'
+                elif dataclasses.is_dataclass(value) and not isinstance(value, type):
+                    config_dict[f.name] = {sf.name: getattr(value, sf.name) for sf in dataclasses.fields(value)}
+                else:
+                    config_dict[f.name] = value
+            Logfire(config=self).info(
+                'Logfire configured',
+                logfire_version=VERSION,
+                logfire_config=config_dict,
+                package_versions=collect_package_info(),
+            )
+
     def force_flush(self, timeout_millis: int = 30_000) -> bool:
         """Force flush all spans and metrics.
 

tests/conftest.py

@@ -122,8 +122,38 @@ def config_kwargs(
     )
 
 
+_original_emit_configuration_span: Any = None
+
+
+@pytest.fixture(autouse=True)
+def _disable_configured_span(monkeypatch: pytest.MonkeyPatch) -> None:  # pyright: ignore[reportUnusedFunction]
+    """Skip the "Logfire configured" span in tests.
+
+    The span is useful in production but adds noise to nearly every snapshot test
+    and would shift trace/span ids when using `IncrementalIdGenerator`.
+    A dedicated test in `test_configure.py` exercises the emit path explicitly.
+    """
+    from logfire._internal.config import LogfireConfig
+
+    global _original_emit_configuration_span
+    if _original_emit_configuration_span is None:
+        _original_emit_configuration_span = LogfireConfig._emit_configuration_span  # pyright: ignore[reportPrivateUsage]
+
+    def _no_op(self: LogfireConfig) -> None:
+        pass
+
+    monkeypatch.setattr(LogfireConfig, '_emit_configuration_span', _no_op)
+
+
+@pytest.fixture
+def real_emit_configuration_span() -> Any:
+    """Return the unpatched `_emit_configuration_span` so a single test can exercise it."""
+    assert _original_emit_configuration_span is not None
+    return _original_emit_configuration_span
+
+
 @pytest.fixture(autouse=True)
-def config(config_kwargs: dict[str, Any], metrics_reader: InMemoryMetricReader) -> None:
+def config(_disable_configured_span: None, config_kwargs: dict[str, Any], metrics_reader: InMemoryMetricReader) -> None:
     logfire.variables_clear()
     configure(
         **config_kwargs,

tests/test_configure.py

@@ -1597,6 +1597,29 @@ def test_configure_twice_no_warning(caplog: LogCaptureFixture):
     assert not caplog.messages
 
 
+def test_configuration_span_emitted(real_emit_configuration_span: Any, exporter: TestExporter):
+    from logfire._internal.config import GLOBAL_CONFIG
+
+    GLOBAL_CONFIG.token = 'pylf_v1_us_FAKE_TOKEN_xyz'
+    try:
+        real_emit_configuration_span(GLOBAL_CONFIG)
+    finally:
+        GLOBAL_CONFIG.token = None
+
+    spans = [
+        s for s in exporter.exported_spans_as_dict(parse_json_attributes=True) if s['name'] == 'Logfire configured'
+    ]
+    assert len(spans) == 1
+    attrs = spans[0]['attributes']
+    assert attrs['logfire_version']
+    assert isinstance(attrs['package_versions'], dict)
+    assert 'logfire' in attrs['package_versions']
+    cfg = attrs['logfire_config']
+    assert isinstance(cfg, dict)
+    assert 'service_name' in cfg
+    assert cfg['token'] == '[REDACTED]'
+
+
 def test_exit_open_spans_exports_suspended_generator_span_before_shutdown() -> None:
     script_path = Path(__file__).parent / 'import_used_for_tests' / 'open_span_at_shutdown.py'
 
@@ -1609,7 +1632,7 @@ def test_exit_open_spans_exports_suspended_generator_span_before_shutdown() -> N
     )
 
     assert result.returncode == 0, result.stderr
-    assert result.stdout == 'open span at shutdown\n'
+    assert result.stdout == 'Logfire configured\nopen span at shutdown\n'
 
 
 def test_send_to_logfire_under_pytest():