diff --git a/Makefile b/Makefile
index e22ecac2..9eb445f3 100644
--- a/Makefile
+++ b/Makefile
@@ -34,3 +34,5 @@ test-integration: lint
 	until docker exec postgres pg_isready -U at_user; do sleep 1; done; \
 	$(POETRY) run pytest tests/integration; \
 	'
+.PHONY: test-all
+test-all: test test-integration
\ No newline at end of file
diff --git a/alphatrion/__init__.py b/alphatrion/__init__.py
index e69de29b..0f7e1309 100644
--- a/alphatrion/__init__.py
+++ b/alphatrion/__init__.py
@@ -0,0 +1,3 @@
+from alphatrion.experiment.craft_exp import CraftExperiment as CraftExperiment
+from alphatrion.observe.observe import log_artifact as log_artifact
+from alphatrion.runtime.runtime import init as init
diff --git a/alphatrion/artifact/artifact.py b/alphatrion/artifact/artifact.py
index c128a81f..05a6cbc3 100644
--- a/alphatrion/artifact/artifact.py
+++ b/alphatrion/artifact/artifact.py
@@ -3,14 +3,13 @@
 import oras.client
 
 from alphatrion import consts
-from alphatrion.runtime.runtime import Runtime
 
 SUCCESS_CODE = 201
 
 
 class Artifact:
-    def __init__(self, runtime: Runtime, insecure: bool = False):
-        self._runtime = runtime
+    def __init__(self, project_id: str, insecure: bool = False):
+        self._project_id = project_id
         self._url = os.environ.get(consts.ARTIFACT_REGISTRY_URL)
         self._url = self._url.replace("https://", "").replace("http://", "")
         self._client = oras.client.OrasClient(
@@ -52,16 +51,17 @@ def push(
             raise ValueError("No files to push.")
 
         url = self._url if self._url.endswith("/") else f"{self._url}/"
-        target = f"{url}{self._runtime._project_id}/{experiment_name}:{version}"
+        target = f"{url}{self._project_id}/{experiment_name}:{version}"
 
         try:
             self._client.push(target, files=files_to_push)
         except Exception as e:
             raise RuntimeError("Failed to push artifacts") from e
 
+    # TODO: should we store it in the metadb instead?
     def list_versions(self, experiment_name: str) -> list[str]:
         url = self._url if self._url.endswith("/") else f"{self._url}/"
-        target = f"{url}{self._runtime._project_id}/{experiment_name}"
+        target = f"{url}{self._project_id}/{experiment_name}"
         try:
             tags = self._client.get_tags(target)
             return tags
@@ -70,7 +70,7 @@ def list_versions(self, experiment_name: str) -> list[str]:
 
     def delete(self, experiment_name: str, versions: str | list[str]):
         url = self._url if self._url.endswith("/") else f"{self._url}/"
-        target = f"{url}{self._runtime._project_id}/{experiment_name}"
+        target = f"{url}{self._project_id}/{experiment_name}"
 
         try:
             self._client.delete_tags(target, tags=versions)
diff --git a/alphatrion/experiment/base.py b/alphatrion/experiment/base.py
index f9f3091c..cb4b9aa9 100644
--- a/alphatrion/experiment/base.py
+++ b/alphatrion/experiment/base.py
@@ -3,9 +3,8 @@
 
 from pydantic import BaseModel, Field, field_validator
 
-from alphatrion.artifact.artifact import Artifact
 from alphatrion.metadata.sql_models import COMPLETED_STATUS, ExperimentStatus
-from alphatrion.runtime.runtime import Runtime
+from alphatrion.runtime.runtime import global_runtime
 
 
 class CheckpointConfig(BaseModel):
@@ -75,9 +74,7 @@ class Experiment:
 
     def __init__(
         self,
-        runtime: Runtime,
         config: ExperimentConfig | None = None,
-        artifact_insecure: bool = False,
     ):
         """
         :param runtime: the Runtime instance
@@ -87,9 +84,8 @@ def __init__(
             artifact registry. Default is False.
         """
 
-        self._runtime = runtime
-        self._artifact = Artifact(runtime, insecure=artifact_insecure)
         self._config = config or ExperimentConfig()
+        self._runtime = global_runtime()
 
         self._steps = 0
         self._best_metric_value = None
@@ -100,13 +96,11 @@ def __init__(
     @classmethod
     def run(
         cls,
-        project_id: str,
         config: ExperimentConfig | None = None,
         name: str | None = None,
         description: str | None = None,
         meta: dict | None = None,
         labels: dict | None = None,
-        artifact_insecure: bool = False,
     ):
         """
         :param project_id: the project ID to run the experiment under
@@ -121,12 +115,7 @@ def run(
         :return: a context manager that yields an Experiment instance
         """
 
-        runtime = Runtime(project_id=project_id)
-        exp = Experiment(
-            runtime=runtime,
-            config=config,
-            artifact_insecure=artifact_insecure,
-        )
+        exp = Experiment(config=config)
         return RunContext(
             exp, name=name, description=description, meta=meta, labels=labels
         )
@@ -234,32 +223,6 @@ def running_time(self) -> int:
             return 0
         return int((datetime.now(UTC) - self._start_at).total_seconds())
 
-    def log_artifact(
-        self,
-        exp_id: int,
-        paths: str | list[str],
-        version: str = "latest",
-    ):
-        """
-        Log artifacts (files) to the artifact registry.
-        :param exp_id: the experiment ID
-        :param paths: list of file paths to log.
-            Support one or multiple files or a folder.
-            If a folder is provided, all files in the folder will be logged.
-            Don't support nested folders currently.
-            Only files in the first level of the folder will be logged.
-        :param version: the version (tag) to log the files under
-        """
-
-        if not paths:
-            raise ValueError("no files specified to log")
-
-        exp = self._runtime._metadb.get_exp(exp_id=exp_id)
-        if exp is None:
-            raise ValueError(f"Experiment with id {exp_id} does not exist.")
-
-        self._artifact.push(experiment_name=exp.name, paths=paths, version=version)
-
 
 class RunContext:
     """A context manager for running experiments."""
diff --git a/alphatrion/experiment/craft_exp.py b/alphatrion/experiment/craft_exp.py
index df577783..b8d578c9 100644
--- a/alphatrion/experiment/craft_exp.py
+++ b/alphatrion/experiment/craft_exp.py
@@ -1,5 +1,4 @@
-from alphatrion.experiment.base import Experiment
-from alphatrion.runtime.runtime import Runtime
+from alphatrion.experiment.base import Experiment, ExperimentConfig
 
 
 class CraftExperiment(Experiment):
@@ -10,7 +9,7 @@ class CraftExperiment(Experiment):
     Opposite to other experiment classes, you need to call all these methods yourself.
     """
 
-    def __init__(self, runtime: Runtime):
-        super().__init__(runtime)
-        # Disable checkpointing by default for CraftExperiment
+    def __init__(self, config: ExperimentConfig | None = None):
+        super().__init__(config=config)
+        # Disable auto-checkpointing by default for CraftExperiment
         self._config.checkpoint.enabled = False
diff --git a/alphatrion/observe/__init__.py b/alphatrion/observe/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/alphatrion/observe/observe.py b/alphatrion/observe/observe.py
new file mode 100644
index 00000000..5d05fd57
--- /dev/null
+++ b/alphatrion/observe/observe.py
@@ -0,0 +1,40 @@
+from alphatrion.runtime.runtime import global_runtime
+
+
+def log_artifact(
+    exp_id: int,
+    paths: str | list[str],
+    version: str = "latest",
+):
+    """
+    Log artifacts (files) to the artifact registry.
+
+    :param exp_id: the experiment ID
+    :param paths: list of file paths to log.
+        Support one or multiple files or a folder.
+        If a folder is provided, all files in the folder will be logged.
+        Don't support nested folders currently.
+        Only files in the first level of the folder will be logged.
+    :param version: the version (tag) to log the files
+    """
+
+    if not paths:
+        raise ValueError("no files specified to log")
+
+    runtime = global_runtime()
+    if runtime is None:
+        raise RuntimeError("Runtime is not initialized. Please call init() first.")
+
+    exp = runtime._metadb.get_exp(exp_id=exp_id)
+    if exp is None:
+        raise ValueError(f"Experiment with id {exp_id} does not exist.")
+
+    runtime._artifact.push(experiment_name=exp.name, paths=paths, version=version)
+
+
+# def log_params(exp_id: int, params: dict):
+#     runtime = global_runtime()
+#     if runtime is None:
+#         raise RuntimeError("Runtime is not initialized. Please call init() first.")
+
+#     runtime._metadb.log_params(exp_id=exp_id, params=params)
diff --git a/alphatrion/runtime/runtime.py b/alphatrion/runtime/runtime.py
index 8f7297be..51571914 100644
--- a/alphatrion/runtime/runtime.py
+++ b/alphatrion/runtime/runtime.py
@@ -1,10 +1,34 @@
+# ruff: noqa: PLW0603
 import os
 
 from alphatrion import consts
+from alphatrion.artifact.artifact import Artifact
 from alphatrion.metadata.sql import SQLStore
 
+__RUNTIME__ = None
 
+
+def init(project_id: str, artifact_insecure: bool = False):
+    """
+    Initialize the AlphaTrion runtime environment.
+
+    :param project_id: the project ID to initialize the environment for
+    :param artifact_insecure: whether to use insecure connection to the
+        artifact registry
+    """
+    global __RUNTIME__
+    __RUNTIME__ = Runtime(project_id=project_id, artifact_insecure=artifact_insecure)
+
+
+def global_runtime():
+    return __RUNTIME__
+
+
+# Runtime contains all kinds of clients, e.g., metadb client, artifact client, etc.
 class Runtime:
-    def __init__(self, project_id: str):
+    def __init__(self, project_id: str, artifact_insecure: bool = False):
         self._project_id = project_id
         self._metadb = SQLStore(os.getenv(consts.METADATA_DB_URL), init_tables=True)
+        self._artifact = Artifact(
+            project_id=self._project_id, insecure=artifact_insecure
+        )
diff --git a/tests/integration/artifact/test_artifact.py b/tests/integration/artifact/test_artifact.py
index e15bac9b..09ac7f86 100644
--- a/tests/integration/artifact/test_artifact.py
+++ b/tests/integration/artifact/test_artifact.py
@@ -5,23 +5,22 @@
 
 import pytest
 
-from alphatrion.artifact.artifact import Artifact
 from alphatrion.experiment.base import Experiment
-from alphatrion.runtime.runtime import Runtime
+from alphatrion.observe.observe import log_artifact
+from alphatrion.runtime.runtime import global_runtime, init
 
 
 @pytest.fixture
 def artifact():
-    # We use a local registry for testing, it doesn't mean
-    # it will always successfully with cloud registries.
-    # We may need e2e tests for that.
-    runtime = Runtime(project_id="test_project")
-    artifact = Artifact(runtime=runtime, insecure=True)
+    init(project_id="test_project", artifact_insecure=True)
+    artifact = global_runtime()._artifact
+
     yield artifact
 
 
 def test_push_with_files(artifact):
-    # Create a temporary directory with some files
+    init(project_id="test_project", artifact_insecure=True)
+
     with tempfile.TemporaryDirectory() as tmpdir:
         os.chdir(tmpdir)
 
@@ -45,6 +44,8 @@ def test_push_with_files(artifact):
 
 
 def test_push_with_folder(artifact):
+    init(project_id="test_project", artifact_insecure=True)
+
     with tempfile.TemporaryDirectory() as tmpdir:
         os.chdir(tmpdir)
 
@@ -66,13 +67,13 @@ def test_push_with_folder(artifact):
 
 
 def test_save_checkpoint():
+    init(project_id="test_project", artifact_insecure=True)
+
     with Experiment.run(
-        project_id="test_project",
         name="context_exp",
         description="Context manager test",
         meta={"key": "value"},
         labels={"type": "unit"},
-        artifact_insecure=True,
     ) as exp:
         with tempfile.TemporaryDirectory() as tmpdir:
             os.chdir(tmpdir)
@@ -81,18 +82,21 @@ def test_save_checkpoint():
             with open(file1, "w") as f:
                 f.write("This is file1.")
 
-            exp.log_artifact(1, paths="file1.txt", version="v1")
-            versions = exp._artifact.list_versions("context_exp")
+            log_artifact(1, paths="file1.txt", version="v1")
+            versions = exp._runtime._artifact.list_versions("context_exp")
             assert "v1" in versions
 
             with open("file1.txt", "w") as f:
                 f.write("This is modified file1.")
 
             # push folder instead
-            exp.log_artifact(1, paths=["file1.txt"], version="v2")
-            versions = exp._artifact.list_versions("context_exp")
+            log_artifact(1, paths=["file1.txt"], version="v2")
+            versions = exp._runtime._artifact.list_versions("context_exp")
             assert "v2" in versions
 
-        exp._artifact.delete(experiment_name="context_exp", versions=["v1", "v2"])
-        versions = exp._artifact.list_versions("context_exp")
+        exp._runtime._artifact.delete(
+            experiment_name="context_exp",
+            versions=["v1", "v2"],
+        )
+        versions = exp._runtime._artifact.list_versions("context_exp")
         assert len(versions) == 0
diff --git a/tests/integration/test_sdk.py b/tests/integration/test_sdk.py
new file mode 100644
index 00000000..f01c16dd
--- /dev/null
+++ b/tests/integration/test_sdk.py
@@ -0,0 +1,26 @@
+import os
+import tempfile
+
+import alphatrion as at
+
+
+def test_sdk():
+    at.init(project_id="test_project", artifact_insecure=True)
+
+    with at.CraftExperiment.run(
+        name="craft_exp",
+        description="test description",
+        meta={"key": "value"},
+        labels={"type": "unit"},
+    ) as exp:
+        with tempfile.TemporaryDirectory() as tmpdir:
+            os.chdir(tmpdir)
+
+            file = "file.txt"
+            with open(file, "w") as f:
+                f.write("Hello, AlphaTrion!")
+
+            at.log_artifact(2, paths=file, version="v1")
+
+        versions = exp._runtime._artifact.list_versions("craft_exp")
+        assert "v1" in versions
diff --git a/tests/unit/artifact/test_artifact.py b/tests/unit/artifact/test_artifact.py
index 02a41bae..489995bf 100644
--- a/tests/unit/artifact/test_artifact.py
+++ b/tests/unit/artifact/test_artifact.py
@@ -3,17 +3,13 @@
 
 import pytest
 
-from alphatrion.artifact.artifact import Artifact
-from alphatrion.runtime.runtime import Runtime
+from alphatrion.runtime.runtime import global_runtime, init
 
 
 @pytest.fixture
 def artifact():
-    # We use a local registry for testing, it doesn't mean
-    # it will always successfully with cloud registries.
-    # We may need e2e tests for that.
-    runtime = Runtime(project_id="test_project")
-    artifact = Artifact(runtime=runtime, insecure=True)
+    init(project_id="test_project", artifact_insecure=True)
+    artifact = global_runtime()._artifact
     yield artifact
 
 
diff --git a/tests/unit/experiment/test_base_exp.py b/tests/unit/experiment/test_base_exp.py
index 852cdacd..61ff822e 100644
--- a/tests/unit/experiment/test_base_exp.py
+++ b/tests/unit/experiment/test_base_exp.py
@@ -2,13 +2,13 @@
 
 from alphatrion.experiment.craft_exp import Experiment
 from alphatrion.metadata.sql_models import ExperimentStatus
-from alphatrion.runtime.runtime import Runtime
+from alphatrion.runtime.runtime import init
 
 
 @pytest.fixture
 def exp():
-    runtime = Runtime(project_id="test_project")
-    exp = Experiment(runtime=runtime)
+    init(project_id="test_project", artifact_insecure=True)
+    exp = Experiment()
     yield exp
 
 
diff --git a/tests/unit/experiment/test_craft_exp.py b/tests/unit/experiment/test_craft_exp.py
index 6261bbcf..a23981c6 100644
--- a/tests/unit/experiment/test_craft_exp.py
+++ b/tests/unit/experiment/test_craft_exp.py
@@ -2,11 +2,13 @@
 
 from alphatrion.experiment.craft_exp import CraftExperiment
 from alphatrion.metadata.sql_models import ExperimentStatus
+from alphatrion.runtime.runtime import init
 
 
 def test_craft_experiment():
+    init(project_id="test_project", artifact_insecure=True)
+
     with CraftExperiment.run(
-        project_id="test_project",
         name="context_exp",
         description="Context manager test",
         meta={"key": "value"},