feat: add LangfuseProvider for remote trace evaluation

pyproject.toml

@@ -44,6 +44,7 @@ dev = [
     "ruff>=0.13.0,<0.15.0",
 ]
 
+langfuse = ["langfuse>=2.0.0,<3"]
 otel = ["opentelemetry-exporter-otlp-proto-http>=1.30.0,<2.0.0"]
 
 [tool.ruff]
@@ -53,7 +54,7 @@ include = ["src/**/*.py", "tests/**/*.py", "tests_integ/**/*.py"]
 [tool.hatch.envs.hatch-test]
 installer = "uv"
 extra-args = ["-n", "auto", "-vv"]
-features = ["otel"]
+features = ["otel", "langfuse"]
 dependencies = [
     "pytest>=8.0.0,<10.0.0",
     "pytest-cov>=7.0.0,<8.0.0",
@@ -91,7 +92,7 @@ prepare = [
 
 [tool.hatch.envs.hatch-static-analysis]
 installer = "uv"
-features = ["otel"]
+features = ["otel", "langfuse"]
 dependencies = [
   "mypy>=1.15.0,<2.0.0",
   "ruff>=0.13.0,<0.15.0",

src/strands_evals/providers/__init__.py

@@ -1,3 +1,5 @@
+from typing import Any
+
 from .exceptions import (
     ProviderError,
     SessionNotFoundError,
@@ -9,9 +11,19 @@
 )
 
 __all__ = [
+    "LangfuseProvider",
     "ProviderError",
     "SessionNotFoundError",
     "TraceNotFoundError",
     "TraceProvider",
     "TraceProviderError",
-]
+]
+
+
+def __getattr__(name: str) -> Any:
+    """Lazy-load providers that depend on optional packages."""
+    if name == "LangfuseProvider":
+        from .langfuse_provider import LangfuseProvider
+
+        return LangfuseProvider
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")

src/strands_evals/providers/exceptions.py

@@ -4,22 +4,14 @@
 class TraceProviderError(Exception):
     """Base exception for trace provider errors."""
 
-    pass
-
 
 class SessionNotFoundError(TraceProviderError):
     """No traces found for the given session ID."""
 
-    pass
-
 
 class TraceNotFoundError(TraceProviderError):
     """Trace with the given ID not found."""
 
-    pass
-
 
 class ProviderError(TraceProviderError):
     """Provider is unreachable or returned an error."""
-
-    pass