Move managed variable registry onto config

logfire/_internal/config.py

@@ -128,6 +128,7 @@
     from typing import TextIO
 
     from logfire.variables import VariablesConfig
+    from logfire.variables.variable import TemplateVariable, Variable
 
     from .main import Logfire
 
@@ -1019,6 +1020,7 @@ def __init__(
         self._variable_provider: VariableProvider = NoOpVariableProvider()
         self._logger_provider = ProxyLoggerProvider(NoOpLoggerProvider())
         self._otlp_forwarding = OTLPForwardingManager([])
+        self._variables: dict[str, Variable[Any] | TemplateVariable[Any, Any]] = {}
         # This ensures that we only call OTEL's global set_tracer_provider once to avoid warnings.
         self._has_set_providers = False
         self._initialized = False

logfire/_internal/main.py

@@ -165,12 +165,15 @@ def __init__(
         self._sample_rate = sample_rate
         self._console_log = console_log
         self._otel_scope = otel_scope
-        self._variables: dict[str, Variable[Any] | TemplateVariable[Any, Any]] = {}
 
     @property
     def config(self) -> LogfireConfig:
         return self._config
 
+    @property
+    def _variables(self) -> dict[str, Variable[Any] | TemplateVariable[Any, Any]]:
+        return self._config._variables  # pyright: ignore[reportPrivateUsage]
+
     @property
     def resource_attributes(self) -> Mapping[str, Any]:
         return self._tracer_provider.resource.attributes
@@ -2748,17 +2751,18 @@ class PromptInputs(BaseModel):
         return variable
 
     def variables_clear(self) -> None:
-        """Clear all registered variables from this Logfire instance.
+        """Clear all variables registered with this Logfire instance's config.
 
         This removes all variables previously registered via [`var()`][logfire.Logfire.var]
-        or [`template_var()`][logfire.Logfire.template_var],
-        allowing them to be re-registered. This is primarily intended for use in tests
-        to ensure a clean state between test cases.
+        or [`template_var()`][logfire.Logfire.template_var] on this instance or any
+        [`with_settings()`][logfire.Logfire.with_settings] sibling that shares its config,
+        allowing them to be re-registered. This is primarily intended for use in tests to
+        ensure a clean state between test cases.
         """
         self._variables.clear()
 
     def variables_get(self) -> list[Variable[Any] | TemplateVariable[Any, Any]]:
-        """Get all variables registered with this Logfire instance."""
+        """Get all variables registered with this Logfire instance's config."""
         return list(self._variables.values())
 
     def variables_push(

tests/test_push_variables.py

@@ -1283,6 +1283,48 @@ def test_get_variables_returns_all_registered() -> None:
     assert var3 in variables
 
 
+def test_with_settings_shares_registered_variables() -> None:
+    """Variables registered on with_settings() siblings share one config registry."""
+    from logfire._internal.main import Logfire
+
+    lf = Logfire()
+    lf2 = lf.with_settings(tags=['other'])
+
+    var1 = lf.var(name='feature_a', default=False, type=bool)
+    var2 = lf2.var(name='feature_b', default='hello', type=str)
+
+    assert lf.variables_get() == [var1, var2]
+    assert lf2.variables_get() == [var1, var2]
+
+
+def test_with_settings_duplicate_variable_names_conflict() -> None:
+    """Duplicate variable names are rejected across with_settings() siblings."""
+    from logfire._internal.main import Logfire
+
+    lf = Logfire()
+    lf2 = lf.with_settings(tags=['other'])
+
+    lf.var(name='feature_enabled', default=False, type=bool)
+    with pytest.raises(ValueError, match="A variable with name 'feature_enabled' has already been registered"):
+        lf2.var(name='feature_enabled', default=True, type=bool)
+
+
+def test_variables_clear_clears_with_settings_siblings() -> None:
+    """variables_clear() clears the shared config registry."""
+    from logfire._internal.main import Logfire
+
+    lf = Logfire()
+    lf2 = lf.with_settings(tags=['other'])
+
+    lf.var(name='feature_a', default=False, type=bool)
+    lf2.var(name='feature_b', default='hello', type=str)
+
+    lf.variables_clear()
+
+    assert lf.variables_get() == []
+    assert lf2.variables_get() == []
+
+
 # --- Validation tests ---
 
 

tests/test_variable_composition.py

@@ -755,6 +755,21 @@ def test_simple_reference(self, config_kwargs: dict[str, Any]):
         assert result.composed_from[0].name == 'greeting'
         assert result.composed_from[0].value == 'Hello'
 
+    def test_code_default_reference_across_with_settings_siblings(self, config_kwargs: dict[str, Any]):
+        """Code-default composition sees variables registered on with_settings() siblings."""
+        lf = logfire.configure(**config_kwargs)
+        lf2 = lf.with_settings(tags=['other'])
+
+        lf.var(name='greeting', default='Hello', type=str)
+        main = lf2.var(name='main', default='@{greeting}@ World', type=str)
+
+        result = main.get()
+
+        assert result.value == 'Hello World'
+        assert len(result.composed_from) == 1
+        assert result.composed_from[0].name == 'greeting'
+        assert result.composed_from[0].value == 'Hello'
+
     def test_override_participates_in_composition(self, config_kwargs: dict[str, Any]):
         """An override value containing @{ref}@ is expanded against the live config.