diff --git a/.github/workflows/codspeed.yml b/.github/workflows/codspeed.yml
new file mode 100644
index 0000000..85e5958
--- /dev/null
+++ b/.github/workflows/codspeed.yml
@@ -0,0 +1,34 @@
+name: CodSpeed
+
+on:
+  pull_request:
+    branches:
+      - "main"
+      - "dev"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  id-token: write
+
+jobs:
+  codspeed:
+    name: Run benchmarks
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          enable-cache: true
+          cache-dependency-glob: "uv.lock"
+
+      - name: Install the project
+        run: uv sync --dev
+
+      - name: Run benchmarks
+        uses: CodSpeedHQ/action@v4
+        with:
+          mode: simulation
+          run: uv run pytest tests/test_benchmarks.py --codspeed
diff --git a/README.md b/README.md
index 7e3a2d3..bda99cc 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # danom
 
-[![PyPI Downloads](https://static.pepy.tech/personalized-badge/danom?period=total&units=INTERNATIONAL_SYSTEM&left_color=BLACK&right_color=BLUE&left_text=downloads)](https://pepy.tech/projects/danom) ![coverage](./coverage.svg)
+[![PyPI Downloads](https://static.pepy.tech/personalized-badge/danom?period=total&units=INTERNATIONAL_SYSTEM&left_color=BLACK&right_color=BLUE&left_text=downloads)](https://pepy.tech/projects/danom) ![coverage](./coverage.svg) [![CodSpeed](https://img.shields.io/endpoint?url=https://codspeed.io/badge.json)](https://codspeed.io/second-ed/danom?utm_source=badge)
 
 # API Reference
 
@@ -275,6 +275,7 @@ Alternatively the map method can be used to return a new type instance with the
 │   ├── __init__.py
 │   ├── conftest.py
 │   ├── test_api.py
+│   ├── test_benchmarks.py
 │   ├── test_monad_laws.py
 │   ├── test_new_type.py
 │   ├── test_result.py
diff --git a/pyproject.toml b/pyproject.toml
index fae79a9..73aa687 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "danom"
-version = "0.11.2"
+version = "0.11.3"
 description = "Functional streams and monads"
 readme = "README.md"
 license = "MIT"
diff --git a/src/danom/_stream.py b/src/danom/_stream.py
index e85bb21..f301dc4 100644
--- a/src/danom/_stream.py
+++ b/src/danom/_stream.py
@@ -7,7 +7,7 @@
 from collections.abc import Awaitable, Callable, Iterable, Sequence
 from concurrent.futures import ProcessPoolExecutor, ThreadPoolExecutor
 from copy import deepcopy
-from enum import Enum, auto
+from enum import Enum
 from functools import reduce
 from itertools import batched
 from typing import ParamSpec, TypeVar, cast
@@ -312,10 +312,15 @@ def partition(
             seq_tuple = self.par_collect(workers=workers, use_threads=use_threads)
         else:
             seq_tuple = self.collect()
-        return (
-            Stream(seq=tuple(x for x in seq_tuple if fn(x))),
-            Stream(seq=tuple(x for x in seq_tuple if not fn(x))),
-        )
+
+        pos, neg = [], []
+
+        for x in seq_tuple:
+            if fn(x):
+                pos.append(x)
+            else:
+                neg.append(x)
+        return (Stream.from_iterable(pos), Stream.from_iterable(neg))
 
     def fold(
         self, initial: T, fn: Callable[[T, U], T], *, workers: int = 1, use_threads: bool = False
@@ -442,7 +447,7 @@ async def async_collect(self) -> Awaitable[tuple[U, ...]]:
 
 
 class _Nothing(Enum):
-    NOTHING = auto()
+    NOTHING = 0
 
 
 PlannedOps = tuple[str, StreamFn]
diff --git a/tests/conftest.py b/tests/conftest.py
index bf93208..9ba58e0 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -11,10 +11,42 @@
 REPO_ROOT = Path(__file__).parents[1]
 
 
+def is_positive(x: float) -> bool:
+    return x > 0
+
+
+def lt_100(x: float) -> bool:
+    return x < 100  # noqa: PLR2004
+
+
 def add[T: (str, float, int)](a: T, b: T) -> T:
     return a + b  # ty: ignore[unsupported-operator]
 
 
+def triple(x: float) -> float:
+    return x * 3
+
+
+def is_gt_ten(x: float) -> float:
+    return x > 10  # noqa: PLR2004
+
+
+def min_two(x: float) -> float:
+    return x - 2
+
+
+def is_even_num(x: float) -> bool:
+    return x % 2 == 0
+
+
+def square(x: float) -> float:
+    return x * x
+
+
+def is_lt_400(x: float) -> float:
+    return x < 400  # noqa: PLR2004
+
+
 def has_len(value: str) -> bool:
     return len(value) > 0
 
diff --git a/tests/test_benchmarks.py b/tests/test_benchmarks.py
new file mode 100644
index 0000000..87ee454
--- /dev/null
+++ b/tests/test_benchmarks.py
@@ -0,0 +1,174 @@
+from __future__ import annotations
+
+from danom import Err, Ok, Result, Stream, all_of, any_of, compose, identity, invert, new_type
+from tests.conftest import (
+    add_one,
+    double,
+    has_len,
+    is_even,
+    is_even_num,
+    is_gt_ten,
+    is_lt_400,
+    is_positive,
+    lt_100,
+    min_two,
+    square,
+    triple,
+)
+
+
+def test_stream_map(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        Stream.from_iterable(range(10_000)).map(add_one).collect()
+
+
+def test_stream_filter(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        Stream.from_iterable(range(10_000)).filter(is_even).collect()
+
+
+def test_stream_map_filter_chain(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        (
+            Stream.from_iterable(range(10_000))
+            .map(triple)
+            .filter(is_gt_ten)  # ty: ignore[invalid-argument-type]
+            .map(min_two)
+            .filter(is_even_num)
+            .map(square)
+            .filter(is_lt_400)  # ty: ignore[invalid-argument-type]
+            .collect()
+        )
+
+
+def test_stream_fold(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        Stream.from_iterable(range(1_000)).fold(0, lambda a, b: a + b)
+
+
+def test_stream_partition(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        Stream.from_iterable(range(1_000)).partition(is_even)
+
+
+def test_ok_creation(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        for i in range(1_000):
+            Ok(i)
+
+
+def test_err_creation(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        for i in range(1_000):
+            Err(error=i)
+
+
+def test_ok_map_chain(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        Ok(1).map(add_one).map(double).map(add_one)
+
+
+def test_ok_and_then_chain(benchmark) -> None:
+    def safe_add_one(x: float) -> Result:
+        return Ok(x + 1)
+
+    @benchmark
+    def _() -> None:
+        Ok(1).and_then(safe_add_one).and_then(safe_add_one).and_then(safe_add_one)
+
+
+def test_err_map_short_circuit(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        Err(error=TypeError()).map(add_one).map(double).map(add_one)
+
+
+def test_result_unwrap(benchmark) -> None:
+    ok = Ok(42)
+
+    @benchmark
+    def _() -> None:
+        ok.unwrap()
+
+
+def test_stream_of_results(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        (
+            Stream.from_iterable([Ok(i) for i in range(100)])
+            .filter(Result.result_is_ok)
+            .map(Result.result_unwrap)
+            .collect()
+        )
+
+
+def test_compose(benchmark) -> None:
+    fn = compose(add_one, double, add_one)
+
+    @benchmark
+    def _() -> None:
+        fn(5)
+
+
+def test_all_of(benchmark) -> None:
+    fn = all_of(is_even, is_positive, lt_100)
+
+    @benchmark
+    def _() -> None:
+        fn(42)
+
+
+def test_any_of(benchmark) -> None:
+    fn = any_of(is_even, is_positive, lt_100)
+
+    @benchmark
+    def _() -> None:
+        fn(42)
+
+
+def test_identity(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        identity(42)
+
+
+def test_invert(benchmark) -> None:
+    fn = invert(is_even)
+
+    @benchmark
+    def _() -> None:
+        fn(3)
+
+
+PositiveFloat = new_type("PositiveFloat", float, validators=[is_positive])
+
+
+def test_new_type_creation(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        PositiveFloat(42.0)
+
+
+def test_new_type_map(benchmark) -> None:
+    val = PositiveFloat(10.0)
+
+    @benchmark
+    def _() -> None:
+        val.map(double)
+
+
+StrType = new_type("StrType", str, validators=[has_len], converters=[str])
+
+
+def test_new_type_with_converter(benchmark) -> None:
+    @benchmark
+    def _() -> None:
+        StrType(12345)
diff --git a/tests/test_safe.py b/tests/test_safe.py
index e9ea1a2..562802d 100644
--- a/tests/test_safe.py
+++ b/tests/test_safe.py
@@ -67,7 +67,7 @@ def test_traceback():
         "Traceback (most recent call last):",
         '  File "./src/danom/_safe.py", line 34, in __call__',
         "    return Ok(self.func(*args, **kwargs))",
-        '  File "./tests/conftest.py", line 85, in div_zero',
+        '  File "./tests/conftest.py", line 117, in div_zero',
         "    return x / 0",
         "ZeroDivisionError: division by zero",
     ]
@@ -79,4 +79,4 @@ def test_traceback():
 
     missing_lines = [line for line in expected_lines if line not in tb_lines]
 
-    assert missing_lines == []
+    assert missing_lines == [], f"lines don't match {tb_lines = }"
diff --git a/uv.lock b/uv.lock
index 30f0b57..21352d7 100644
--- a/uv.lock
+++ b/uv.lock
@@ -317,7 +317,7 @@ wheels = [
 
 [[package]]
 name = "danom"
-version = "0.11.2"
+version = "0.11.3"
 source = { editable = "." }
 dependencies = [
     { name = "attrs" },