diff --git a/src/promptum/providers/exceptions.py b/src/promptum/providers/exceptions.py
index 65d2230..3ccc96f 100644
--- a/src/promptum/providers/exceptions.py
+++ b/src/promptum/providers/exceptions.py
@@ -50,6 +50,5 @@ def __init__(
         self.last_response_body = last_response_body
         self.retry_delays = retry_delays
         super().__init__(
-            f"Request failed after {attempts} attempts"
-            f" (last status {last_status_code})"
+            f"Request failed after {attempts} attempts (last status {last_status_code})"
         )
diff --git a/src/promptum/providers/openrouter.py b/src/promptum/providers/openrouter.py
index a20991c..883c2f9 100644
--- a/src/promptum/providers/openrouter.py
+++ b/src/promptum/providers/openrouter.py
@@ -78,10 +78,9 @@ async def generate(
         if conflicts:
             raise ValueError(
                 f"Cannot override reserved payload fields: {', '.join(sorted(conflicts))}"
-                )
+            )
         payload.update(kwargs)
 
-
         for attempt in range(config.max_attempts):
             start_time = time.perf_counter()
             try:
@@ -133,9 +132,7 @@ async def generate(
                     retry_delays.append(delay)
                     await self._sleep(delay)
                 else:
-                    raise ProviderTransientError(
-                        config.max_attempts, retry_delays
-                    ) from e
+                    raise ProviderTransientError(config.max_attempts, retry_delays) from e
 
         raise ProviderRetryExhaustedError(
             config.max_attempts, last_status_code, last_response_body, retry_delays
diff --git a/src/promptum/session/report.py b/src/promptum/session/report.py
index ee10cf4..756a485 100644
--- a/src/promptum/session/report.py
+++ b/src/promptum/session/report.py
@@ -15,8 +15,8 @@ def __post_init__(self):
     def get_summary(self) -> Summary:
         total = len(self.results)
         passed = sum(1 for r in self.results if r.passed)
-        execution_errors=self._count_execution_errors()
-        validation_failures=self._count_validation_failures()
+        execution_errors = self._count_execution_errors()
+        validation_failures = self._count_validation_failures()
 
         latencies = [r.metrics.latency_ms for r in self.results if r.metrics]
         total_cost = sum(r.metrics.cost_usd or 0 for r in self.results if r.metrics)
@@ -42,7 +42,7 @@ def filter(
         tags: Sequence[str] | None = None,
         passed: bool | None = None,
     ) -> "Report":
-        filtered = list(self.results)
+        filtered = self.results
 
         if model is not None:
             filtered = [r for r in filtered if r.test_case.model == model]
@@ -71,8 +71,4 @@ def _count_execution_errors(self) -> int:
         return sum(1 for r in self.results if r.execution_error is not None)
 
     def _count_validation_failures(self) -> int:
-        return sum(
-            1
-            for r in self.results
-            if not r.passed and r.execution_error is None
-        )
+        return sum(1 for r in self.results if not r.passed and r.execution_error is None)
diff --git a/tests/benchmark/test_report_filtering.py b/tests/benchmark/test_report_filtering.py
index 1b12f88..cadbdc9 100644
--- a/tests/benchmark/test_report_filtering.py
+++ b/tests/benchmark/test_report_filtering.py
@@ -40,3 +40,10 @@ def test_report_group_by_model(sample_report: Report) -> None:
     assert "model2" in grouped
     assert len(grouped["model1"].results) == 2
     assert len(grouped["model2"].results) == 1
+
+
+def test_report_no_filter(sample_report: Report) -> None:
+    unfiltered = sample_report.filter(model=None, tags=None, passed=None)
+    assert isinstance(unfiltered, Report)
+    assert len(unfiltered.results) == len(sample_report.results)
+    assert unfiltered == sample_report
diff --git a/tests/providers/test_openrouter.py b/tests/providers/test_openrouter.py
index 2d1ffd5..16b678d 100644
--- a/tests/providers/test_openrouter.py
+++ b/tests/providers/test_openrouter.py
@@ -367,8 +367,6 @@ async def test_generate_uses_per_call_retry_config_over_default(
         client._client.post = AsyncMock(side_effect=responses)
         client._sleep = AsyncMock()
 
-        content, _ = await client.generate(
-            prompt="hello", model="m", retry_config=per_call_config
-        )
+        content, _ = await client.generate(prompt="hello", model="m", retry_config=per_call_config)
 
     assert content == "Hello, world!"
diff --git a/tests/validation/test_json_schema.py b/tests/validation/test_json_schema.py
index 272cfc4..d63dc0a 100644
--- a/tests/validation/test_json_schema.py
+++ b/tests/validation/test_json_schema.py
@@ -42,6 +42,7 @@ def test_json_schema_describe_includes_validator_info_and_required_keys() -> Non
     assert "a" in description
     assert "b" in description
 
+
 def test_json_schema_describe_without_required_keys() -> None:
     validator = JsonSchema(required_keys=())
     description = validator.describe()
diff --git a/tests/validation/test_regex.py b/tests/validation/test_regex.py
index fe3d4ce..6f065a7 100644
--- a/tests/validation/test_regex.py
+++ b/tests/validation/test_regex.py
@@ -32,6 +32,7 @@ def test_regex_describe_includes_validator_name_and_pattern() -> None:
     assert "Regex" in description
     assert r"\d+" in description
 
+
 def test_regex_with_ignorecase_flag() -> None:
     validator = Regex(r"hello", flags=re.IGNORECASE)