diff --git a/agentplatform/agent_engines/templates/adk.py b/agentplatform/agent_engines/templates/adk.py
index ce9c9bb967..9eaa49ce46 100644
--- a/agentplatform/agent_engines/templates/adk.py
+++ b/agentplatform/agent_engines/templates/adk.py
@@ -2172,7 +2172,8 @@ def _tracing_enabled(self) -> bool:
         )
 
     def project_id(self) -> Optional[str]:
-        if project := self._tmpl_attrs.get("project"):
+        project = self._tmpl_attrs.get("project")
+        if project and str(project).isdigit():
             try:
                 from google.cloud.aiplatform.utils import (
                     resource_manager_utils,
@@ -2184,4 +2185,4 @@ def project_id(self) -> Optional[str]:
             except (exceptions.PermissionDenied, exceptions.Unauthenticated):
                 return project
 
-        return None
+        return project or None
diff --git a/tests/unit/agentplatform/frameworks/test_frameworks_adk.py b/tests/unit/agentplatform/frameworks/test_frameworks_adk.py
index 99e9881cc4..a3725842d9 100644
--- a/tests/unit/agentplatform/frameworks/test_frameworks_adk.py
+++ b/tests/unit/agentplatform/frameworks/test_frameworks_adk.py
@@ -60,6 +60,7 @@ def __init__(self, name: str, model: str):
 _TEST_LOCATION = "us-central1"
 _TEST_PROJECT = "test-project"
 _TEST_PROJECT_ID = "test-project-id"
+_TEST_PROJECT_NUMBER = "123456789"
 _TEST_API_KEY = "test-api-key"
 _TEST_MODEL = "gemini-2.0-flash"
 _TEST_USER_ID = "test_user_id"
@@ -1251,7 +1252,7 @@ def test_default_instrumentor_enablement(
 
         # Assert
         default_instrumentor_builder_mock.assert_called_once_with(
-            _TEST_PROJECT_ID,
+            _TEST_PROJECT,
             enable_tracing=want_tracing_setup,
             enable_logging=want_logging_setup,
         )
@@ -1314,7 +1315,7 @@ def test_custom_instrumentor_enablement(
 
         # Assert
         if want_custom_instrumentor_called:
-            custom_instrumentor.assert_called_once_with(_TEST_PROJECT_ID)
+            custom_instrumentor.assert_called_once_with(_TEST_PROJECT)
         else:
             custom_instrumentor.assert_not_called()
 
@@ -1347,7 +1348,7 @@ def test_tracing_setup(
             headers=mock.ANY,
         )
 
-        get_project_id_mock.assert_called_with(_TEST_PROJECT)
+        get_project_id_mock.assert_not_called()
 
         user_agent = otlp_span_exporter_mock.call_args.kwargs["headers"]["User-Agent"]
         assert (
@@ -1358,6 +1359,38 @@ def test_tracing_setup(
             is not None
         )
 
+    def test_project_id_skips_lookup_for_project_id(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        """Project IDs are returned as-is without a GetProject call."""
+        app = adk_template.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = _TEST_PROJECT
+
+        assert app.project_id() == _TEST_PROJECT
+        get_project_id_mock.assert_not_called()
+
+    def test_project_id_resolves_project_number(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        """Project numbers are resolved to project IDs via GetProject."""
+        app = adk_template.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = _TEST_PROJECT_NUMBER
+
+        assert app.project_id() == _TEST_PROJECT_ID
+        get_project_id_mock.assert_called_once_with(_TEST_PROJECT_NUMBER)
+
+    def test_project_id_without_project(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        app = adk_template.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = None
+
+        assert app.project_id() is None
+        get_project_id_mock.assert_not_called()
+
     @pytest.mark.usefixtures("caplog")
     def test_enable_tracing(
         self,
diff --git a/tests/unit/vertex_adk/test_agent_engine_templates_adk.py b/tests/unit/vertex_adk/test_agent_engine_templates_adk.py
index a359289406..98078145dc 100644
--- a/tests/unit/vertex_adk/test_agent_engine_templates_adk.py
+++ b/tests/unit/vertex_adk/test_agent_engine_templates_adk.py
@@ -59,6 +59,7 @@ def __init__(self, name: str, model: str):
 _TEST_LOCATION = "us-central1"
 _TEST_PROJECT = "test-project"
 _TEST_PROJECT_ID = "test-project-id"
+_TEST_PROJECT_NUMBER = "123456789"
 _TEST_API_KEY = "test-api-key"
 _TEST_MODEL = "gemini-2.0-flash"
 _TEST_USER_ID = "test_user_id"
@@ -1064,7 +1065,7 @@ def test_tracing_setup(
             headers=mock.ANY,
         )
 
-        get_project_id_mock.assert_called_with(_TEST_PROJECT)
+        get_project_id_mock.assert_not_called()
 
         user_agent = otlp_span_exporter_mock.call_args.kwargs["headers"]["User-Agent"]
         assert (
@@ -1075,6 +1076,44 @@ def test_tracing_setup(
             is not None
         )
 
+    def test_project_id_skips_lookup_for_project_id(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        """Project IDs are returned as-is without a GetProject call."""
+        app = agent_engines.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = _TEST_PROJECT
+        # Discard the lookup that vertexai.init() made in setup_method.
+        get_project_id_mock.reset_mock()
+
+        assert app.project_id() == _TEST_PROJECT
+        get_project_id_mock.assert_not_called()
+
+    def test_project_id_resolves_project_number(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        """Project numbers are resolved to project IDs via GetProject."""
+        app = agent_engines.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = _TEST_PROJECT_NUMBER
+        # Discard the lookup that vertexai.init() made in setup_method.
+        get_project_id_mock.reset_mock()
+
+        assert app.project_id() == _TEST_PROJECT_ID
+        get_project_id_mock.assert_called_once_with(_TEST_PROJECT_NUMBER)
+
+    def test_project_id_without_project(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        app = agent_engines.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = None
+        # Discard the lookup that vertexai.init() made in setup_method.
+        get_project_id_mock.reset_mock()
+
+        assert app.project_id() is None
+        get_project_id_mock.assert_not_called()
+
     @pytest.mark.usefixtures("caplog")
     def test_enable_tracing(
         self,
diff --git a/tests/unit/vertex_adk/test_reasoning_engine_templates_adk.py b/tests/unit/vertex_adk/test_reasoning_engine_templates_adk.py
index e956f06e1a..391dc7298a 100644
--- a/tests/unit/vertex_adk/test_reasoning_engine_templates_adk.py
+++ b/tests/unit/vertex_adk/test_reasoning_engine_templates_adk.py
@@ -47,6 +47,7 @@ def __init__(self, name: str, model: str):
 _TEST_LOCATION = "us-central1"
 _TEST_PROJECT = "test-project"
 _TEST_PROJECT_ID = "test-project-id"
+_TEST_PROJECT_NUMBER = "123456789"
 _TEST_MODEL = "gemini-2.0-flash"
 _TEST_USER_ID = "test_user_id"
 _TEST_AGENT_NAME = "test_agent"
@@ -1010,11 +1011,9 @@ def test_tracing_setup(
             headers=mock.ANY,
         )
 
-        calls = [
-            mock.call(project_number=_TEST_PROJECT_ID, credentials=mock.ANY),
-            mock.call(_TEST_PROJECT_ID),
-        ]
-        get_project_id_mock.assert_has_calls(calls)
+        get_project_id_mock.assert_called_once_with(
+            project_number=_TEST_PROJECT_ID, credentials=mock.ANY
+        )
 
         user_agent = otlp_span_exporter_mock.call_args.kwargs["headers"]["User-Agent"]
         assert (
@@ -1029,6 +1028,44 @@ def test_tracing_setup(
             == expected_attributes
         )
 
+    def test_project_id_skips_lookup_for_project_id(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        """Project IDs are returned as-is without a GetProject call."""
+        app = reasoning_engines.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = _TEST_PROJECT
+        # Discard the lookup that vertexai.init() made in setup_method.
+        get_project_id_mock.reset_mock()
+
+        assert app.project_id() == _TEST_PROJECT
+        get_project_id_mock.assert_not_called()
+
+    def test_project_id_resolves_project_number(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        """Project numbers are resolved to project IDs via GetProject."""
+        app = reasoning_engines.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = _TEST_PROJECT_NUMBER
+        # Discard the lookup that vertexai.init() made in setup_method.
+        get_project_id_mock.reset_mock()
+
+        assert app.project_id() == _TEST_PROJECT_ID
+        get_project_id_mock.assert_called_once_with(_TEST_PROJECT_NUMBER)
+
+    def test_project_id_without_project(
+        self,
+        get_project_id_mock: mock.Mock,
+    ):
+        app = reasoning_engines.AdkApp(agent=_TEST_AGENT)
+        app._tmpl_attrs["project"] = None
+        # Discard the lookup that vertexai.init() made in setup_method.
+        get_project_id_mock.reset_mock()
+
+        assert app.project_id() is None
+        get_project_id_mock.assert_not_called()
+
     @mock.patch.dict(os.environ)
     def test_span_content_capture_disabled_by_default(self):
         app = reasoning_engines.AdkApp(agent=_TEST_AGENT)
diff --git a/vertexai/agent_engines/templates/adk.py b/vertexai/agent_engines/templates/adk.py
index 76398ba03c..5f814b5b12 100644
--- a/vertexai/agent_engines/templates/adk.py
+++ b/vertexai/agent_engines/templates/adk.py
@@ -1868,7 +1868,8 @@ def _tracing_enabled(self) -> bool:
         )
 
     def project_id(self) -> Optional[str]:
-        if project := self._tmpl_attrs.get("project"):
+        project = self._tmpl_attrs.get("project")
+        if project and str(project).isdigit():
             try:
                 from google.cloud.aiplatform.utils import (
                     resource_manager_utils,
@@ -1880,4 +1881,4 @@ def project_id(self) -> Optional[str]:
             except (exceptions.PermissionDenied, exceptions.Unauthenticated):
                 return project
 
-        return None
+        return project or None
diff --git a/vertexai/preview/reasoning_engines/templates/adk.py b/vertexai/preview/reasoning_engines/templates/adk.py
index ed8909d804..003812ab3a 100644
--- a/vertexai/preview/reasoning_engines/templates/adk.py
+++ b/vertexai/preview/reasoning_engines/templates/adk.py
@@ -1765,7 +1765,8 @@ def _warn_if_telemetry_api_disabled(self):
             _warn(_TELEMETRY_API_DISABLED_WARNING % (project, project))
 
     def project_id(self) -> Optional[str]:
-        if project := self._tmpl_attrs.get("project"):
+        project = self._tmpl_attrs.get("project")
+        if project and str(project).isdigit():
             try:
                 from google.cloud.aiplatform.utils import (
                     resource_manager_utils,
@@ -1777,4 +1778,4 @@ def project_id(self) -> Optional[str]:
             except (exceptions.PermissionDenied, exceptions.Unauthenticated):
                 return project
 
-        return None
+        return project or None