Add GetDag endpoint to execution_api

airflow-core/src/airflow/api_fastapi/execution_api/datamodels/dags.py

@@ -0,0 +1,35 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+
+from datetime import datetime
+
+from airflow.api_fastapi.core_api.base import BaseModel
+
+
+class DagResponse(BaseModel):
+    """Schema for DAG response."""
+
+    dag_id: str
+    is_paused: bool
+    bundle_name: str | None
+    bundle_version: str | None
+    relative_fileloc: str | None
+    owners: str | None
+    tags: list[str]
+    next_dagrun: datetime | None

airflow-core/src/airflow/api_fastapi/execution_api/routes/__init__.py

@@ -24,6 +24,7 @@
     assets,
     connections,
     dag_runs,
+    dags,
     health,
     hitl,
     task_instances,
@@ -43,6 +44,7 @@
 authenticated_router.include_router(asset_events.router, prefix="/asset-events", tags=["Asset Events"])
 authenticated_router.include_router(connections.router, prefix="/connections", tags=["Connections"])
 authenticated_router.include_router(dag_runs.router, prefix="/dag-runs", tags=["Dag Runs"])
+authenticated_router.include_router(dags.router, prefix="/dags", tags=["Dags"])
 authenticated_router.include_router(task_instances.router, prefix="/task-instances", tags=["Task Instances"])
 authenticated_router.include_router(
     task_reschedules.router, prefix="/task-reschedules", tags=["Task Reschedules"]

airflow-core/src/airflow/api_fastapi/execution_api/routes/dags.py

@@ -0,0 +1,59 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+
+from fastapi import APIRouter, HTTPException, status
+
+from airflow.api_fastapi.common.db.common import SessionDep
+from airflow.api_fastapi.execution_api.datamodels.dags import DagResponse
+from airflow.models.dag import DagModel
+
+router = APIRouter()
+
+
+@router.get(
+    "/{dag_id}",
+    responses={
+        status.HTTP_404_NOT_FOUND: {"description": "DAG not found for the given dag_id"},
+    },
+)
+def get_dag(
+    dag_id: str,
+    session: SessionDep,
+) -> DagResponse:
+    """Get a DAG."""
+    dag_model: DagModel | None = session.get(DagModel, dag_id)
+    if not dag_model:
+        raise HTTPException(
+            status.HTTP_404_NOT_FOUND,
+            detail={
+                "reason": "not_found",
+                "message": f"The Dag with dag_id: `{dag_id}` was not found",
+            },
+        )
+
+    return DagResponse(
+        dag_id=dag_model.dag_id,
+        is_paused=dag_model.is_paused,
+        bundle_name=dag_model.bundle_name,
+        bundle_version=dag_model.bundle_version,
+        relative_fileloc=dag_model.relative_fileloc,
+        owners=dag_model.owners,
+        tags=sorted(tag.name for tag in dag_model.tags),
+        next_dagrun=dag_model.next_dagrun,
+    )

airflow-core/src/airflow/api_fastapi/execution_api/versions/__init__.py

@@ -39,9 +39,11 @@
     ModifyDeferredTaskKwargsToJsonValue,
     RemoveUpstreamMapIndexesField,
 )
+from airflow.api_fastapi.execution_api.versions.v2026_04_13 import AddDagEndpoint
 
 bundle = VersionBundle(
     HeadVersion(),
+    Version("2026-04-13", AddDagEndpoint),
     Version(
         "2026-03-31",
         MakeDagRunStartDateNullable,

airflow-core/src/airflow/api_fastapi/execution_api/versions/v2026_04_13.py

@@ -0,0 +1,28 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+
+from cadwyn import VersionChange, endpoint
+
+
+class AddDagEndpoint(VersionChange):
+    """Add the `/dags/{dag_id}` endpoint."""
+
+    description = __doc__
+
+    instructions_to_migrate_to_previous_version = (endpoint("/dags/{dag_id}", ["GET"]).didnt_exist,)

airflow-core/tests/unit/api_fastapi/execution_api/versions/head/test_dags.py

@@ -0,0 +1,128 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from unittest.mock import ANY
+
+import pytest
+from sqlalchemy import update
+
+from airflow.models import DagModel
+from airflow.providers.standard.operators.empty import EmptyOperator
+
+from tests_common.test_utils.db import clear_db_runs
+
+pytestmark = pytest.mark.db_test
+
+
+class TestDag:
+    def setup_method(self):
+        clear_db_runs()
+
+    def teardown_method(self):
+        clear_db_runs()
+
+    @pytest.mark.parametrize(
+        ("state", "expected"),
+        [
+            pytest.param(True, True),
+            pytest.param(False, False),
+        ],
+    )
+    def test_get_dag(self, client, session, dag_maker, state, expected):
+        """Test getting a DAG."""
+
+        dag_id = "test_get_dag"
+        next_dagrun = datetime(2026, 4, 13, tzinfo=timezone.utc)
+
+        with dag_maker(dag_id=dag_id, session=session, serialized=True, tags=["z_tag", "a_tag"]):
+            EmptyOperator(task_id="test_task")
+
+        session.execute(
+            update(DagModel)
+            .where(DagModel.dag_id == dag_id)
+            .values(
+                is_paused=state,
+                bundle_version="bundle-version",
+                relative_fileloc="dags/example.py",
+                owners="owner_1",
+                next_dagrun=next_dagrun,
+            )
+        )
+
+        session.commit()
+
+        response = client.get(
+            f"/execution/dags/{dag_id}",
+        )
+
+        assert response.status_code == 200
+        assert response.json() == {
+            "dag_id": dag_id,
+            "is_paused": expected,
+            "bundle_name": "dag_maker",
+            "bundle_version": "bundle-version",
+            "relative_fileloc": "dags/example.py",
+            "owners": "owner_1",
+            "tags": ["a_tag", "z_tag"],
+            "next_dagrun": "2026-04-13T00:00:00Z",
+        }
+
+    def test_dag_not_found(self, client, session, dag_maker):
+        """Test Dag not found"""
+
+        dag_id = "test_get_dag"
+
+        response = client.get(
+            f"/execution/dags/{dag_id}",
+        )
+
+        assert response.status_code == 404
+        assert response.json() == {
+            "detail": {
+                "message": "The Dag with dag_id: `test_get_dag` was not found",
+                "reason": "not_found",
+            }
+        }
+
+    def test_get_dag_defaults(self, client, session, dag_maker):
+        """Test getting a DAG with default model values."""
+
+        dag_id = "test_get_dag_defaults"
+
+        with dag_maker(dag_id=dag_id, session=session, serialized=True):
+            EmptyOperator(task_id="test_task")
+
+        session.commit()
+
+        response = client.get(
+            f"/execution/dags/{dag_id}",
+        )
+
+        assert response.status_code == 200
+        assert response.json() == {
+            "dag_id": dag_id,
+            "is_paused": False,
+            "bundle_name": "dag_maker",
+            "bundle_version": None,
+            "relative_fileloc": "test_dags.py",
+            "owners": "airflow",
+            "tags": [],
+            "next_dagrun": ANY,
+        }

airflow-core/tests/unit/api_fastapi/execution_api/versions/v2026_03_31/test_dags.py

@@ -0,0 +1,34 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+
+import pytest
+
+pytestmark = pytest.mark.db_test
+
+
+@pytest.fixture
+def old_ver_client(client):
+    client.headers["Airflow-API-Version"] = "2026-03-31"
+    return client
+
+
+def test_dag_endpoint_not_available_in_previous_version(old_ver_client):
+    response = old_ver_client.get("/execution/dags/test_dag")
+
+    assert response.status_code == 404

airflow-core/tests/unit/dag_processing/test_processor.py

@@ -1911,6 +1911,7 @@ def get_type_names(union_type):
             "GetAssetEventByAssetAlias",
             "GetDagRun",
             "GetDagRunState",
+            "GetDag",
             "GetDRCount",
             "GetTaskBreadcrumbs",
             "GetTaskRescheduleStartDate",
@@ -1935,6 +1936,7 @@ def get_type_names(union_type):
         in_task_runner_but_not_in_dag_processing_process = {
             "AssetResult",
             "AssetEventsResult",
+            "DagResult",
             "DagRunResult",
             "DagRunStateResult",
             "DRCount",

airflow-core/tests/unit/jobs/test_triggerer_job.py

@@ -1317,6 +1317,7 @@ def get_type_names(union_type):
             "ResendLoggingFD",
             "CreateHITLDetailPayload",
             "SetRenderedMapIndex",
+            "GetDag",
         }
 
         in_task_but_not_in_trigger_runner = {
@@ -1336,6 +1337,7 @@ def get_type_names(union_type):
             "PreviousDagRunResult",
             "PreviousTIResult",
             "HITLDetailRequestResult",
+            "DagResult",
         }
 
         supervisor_diff = (

task-sdk/src/airflow/sdk/api/client.py

@@ -45,6 +45,7 @@
     AssetEventsResponse,
     AssetResponse,
     ConnectionResponse,
+    DagResponse,
     DagRun,
     DagRunStateResponse,
     DagRunType,
@@ -772,6 +773,18 @@ def get_previous(
         return PreviousDagRunResult(dag_run=resp.json())
 
 
+class DagsOperations:
+    __slots__ = ("client",)
+
+    def __init__(self, client: Client):
+        self.client = client
+
+    def get(self, dag_id: str) -> DagResponse:
+        """Get a DAG via the API server."""
+        resp = self.client.get(f"dags/{dag_id}")
+        return DagResponse.model_validate_json(resp.read())
+
+
 class HITLOperations:
     """
     Operations related to Human in the loop. Require Airflow 3.1+.
@@ -1012,6 +1025,12 @@ def hitl(self):
         """Operations related to HITL Responses."""
         return HITLOperations(self)
 
+    @lru_cache()  # type: ignore[misc]
+    @property
+    def dags(self) -> DagsOperations:
+        """Operations related to DAGs."""
+        return DagsOperations(self)
+
 
 # This is only used for parsing. ServerResponseError is raised instead
 class _ErrorBody(BaseModel):