diff --git a/components/renku_data_services/notebooks/apispec.py b/components/renku_data_services/notebooks/apispec.py
index 860256726..eec402048 100644
--- a/components/renku_data_services/notebooks/apispec.py
+++ b/components/renku_data_services/notebooks/apispec.py
@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  api.spec.yaml
-#   timestamp: 2024-10-28T16:00:32+00:00
+#   timestamp: 2024-12-11T13:03:50+00:00
 
 from __future__ import annotations
 
diff --git a/components/renku_data_services/session/api.spec.yaml b/components/renku_data_services/session/api.spec.yaml
index 11b188344..d607cbe42 100644
--- a/components/renku_data_services/session/api.spec.yaml
+++ b/components/renku_data_services/session/api.spec.yaml
@@ -535,6 +535,9 @@ components:
       description: A container image
       type: string
       maxLength: 500
+      # NOTE: regex for an image name, optionally with a tag or sha256 specified
+      # based on https://github.com/opencontainers/distribution-spec/blob/main/spec.md
+      pattern: "^[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*(\\/[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*)*(:[a-zA-Z0-9_][a-zA-Z0-9._-]{0,127}|@sha256:[a-fA-F0-9]{64}){0,1}$" 
       example: renku/renkulab-py:3.10-0.18.1
     DefaultUrl:
       description: The default path to open in a session
diff --git a/components/renku_data_services/session/apispec.py b/components/renku_data_services/session/apispec.py
index 1a14b30ab..94f84b00d 100644
--- a/components/renku_data_services/session/apispec.py
+++ b/components/renku_data_services/session/apispec.py
@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  api.spec.yaml
-#   timestamp: 2024-11-24T09:32:46+00:00
+#   timestamp: 2024-12-11T13:31:04+00:00
 
 from __future__ import annotations
 
@@ -57,6 +57,7 @@ class Environment(BaseAPISpec):
         description="A container image",
         example="renku/renkulab-py:3.10-0.18.1",
         max_length=500,
+        pattern="^[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*(\\/[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*)*(:[a-zA-Z0-9_][a-zA-Z0-9._-]{0,127}|@sha256:[a-fA-F0-9]{64}){0,1}$",
     )
     default_url: str = Field(
         ...,
@@ -118,6 +119,7 @@ class EnvironmentPost(BaseAPISpec):
         description="A container image",
         example="renku/renkulab-py:3.10-0.18.1",
         max_length=500,
+        pattern="^[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*(\\/[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*)*(:[a-zA-Z0-9_][a-zA-Z0-9._-]{0,127}|@sha256:[a-fA-F0-9]{64}){0,1}$",
     )
     default_url: str = Field(
         "/lab",
@@ -178,6 +180,7 @@ class EnvironmentPatch(BaseAPISpec):
         description="A container image",
         example="renku/renkulab-py:3.10-0.18.1",
         max_length=500,
+        pattern="^[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*(\\/[a-z0-9]+((\\.|_|__|-+)[a-z0-9]+)*)*(:[a-zA-Z0-9_][a-zA-Z0-9._-]{0,127}|@sha256:[a-fA-F0-9]{64}){0,1}$",
     )
     default_url: Optional[str] = Field(
         None,
diff --git a/test/bases/renku_data_services/data_api/test_sessions.py b/test/bases/renku_data_services/data_api/test_sessions.py
index bd2dfc0e1..c0f1c71fa 100644
--- a/test/bases/renku_data_services/data_api/test_sessions.py
+++ b/test/bases/renku_data_services/data_api/test_sessions.py
@@ -80,11 +80,21 @@ async def test_get_session_environment(
 
 
 @pytest.mark.asyncio
-async def test_post_session_environment(sanic_client: SanicASGITestClient, admin_headers) -> None:
+@pytest.mark.parametrize(
+    "image_name",
+    [
+        "renku/renku",
+        "u/renku/renku:latest",
+        "docker.io/renku/renku:latest",
+        "renku/renku@sha256:eceed25752d7544db159e4144a41ed6e96e667f39ff9fa18322d79c33729a18c",
+        "registry.renkulab.io/john.doe/test-34:38d8b3d",
+    ],
+)
+async def test_post_session_environment(sanic_client: SanicASGITestClient, admin_headers, image_name: str) -> None:
     payload = {
         "name": "Environment 1",
         "description": "A session environment.",
-        "container_image": "some_image:some_tag",
+        "container_image": image_name,
     }
 
     _, res = await sanic_client.post("/api/data/environments", headers=admin_headers, json=payload)
@@ -93,7 +103,32 @@ async def test_post_session_environment(sanic_client: SanicASGITestClient, admin
     assert res.json is not None
     assert res.json.get("name") == "Environment 1"
     assert res.json.get("description") == "A session environment."
-    assert res.json.get("container_image") == "some_image:some_tag"
+    assert res.json.get("container_image") == image_name
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "image_name",
+    [
+        "https://example.com/r/test:latest",
+        "renku/_bla",
+        "renku/test:töst",
+        "renku/test@sha254:abcd",
+        " renku/test:latest",
+    ],
+)
+async def test_post_session_environment_invalid_image(
+    sanic_client: SanicASGITestClient, admin_headers, image_name: str
+) -> None:
+    payload = {
+        "name": "Environment 1",
+        "description": "A session environment.",
+        "container_image": image_name,
+    }
+
+    _, res = await sanic_client.post("/api/data/environments", headers=admin_headers, json=payload)
+
+    assert res.status_code == 422, res.text
 
 
 @pytest.mark.asyncio