diff --git a/bugsink/api_mixins.py b/bugsink/api_mixins.py
new file mode 100644
index 0000000..c240f57
--- /dev/null
+++ b/bugsink/api_mixins.py
@@ -0,0 +1,42 @@
+from rest_framework.exceptions import ValidationError
+
+
+class ExpandableSerializerMixin:
+    expandable_fields = {}
+
+    def __init__(self, *args, **kwargs):
+        self._expand = set(kwargs.pop("expand", []))
+        super().__init__(*args, **kwargs)
+
+    def to_representation(self, instance):
+        data = super().to_representation(instance)
+        for field, serializer_cls in self.expandable_fields.items():
+            if field in self._expand:
+                data[field] = serializer_cls(getattr(instance, field)).data
+        return data
+
+
+class ExpandViewSetMixin:
+    """
+    Mixin for ViewSets that support ?expand=...
+    Requires the serializer class to define expandable_fields.
+    """
+
+    def get_serializer(self, *args, **kwargs):
+        expand = self.request.query_params.getlist("expand")
+        if expand:
+            if len(expand) == 1 and "," in expand[0]:
+                expand = expand[0].split(",")
+
+            serializer_cls = self.get_serializer_class()
+            expandable = getattr(serializer_cls, "expandable_fields", None)
+            if expandable is None:
+                raise ValidationError({"expand": ["Expansions are not supported on this endpoint."]})
+
+            invalid = [f for f in expand if f not in expandable]
+            if invalid:
+                raise ValidationError({"expand": [f"Unknown field: {name}" for name in invalid]})
+
+            kwargs["expand"] = expand
+
+        return super().get_serializer(*args, **kwargs)
diff --git a/projects/api_views.py b/projects/api_views.py
index 111bf0a..41a9c6a 100644
--- a/projects/api_views.py
+++ b/projects/api_views.py
@@ -1,6 +1,8 @@
 from django.shortcuts import get_object_or_404
 from rest_framework import viewsets
+
 from bugsink.api_pagination import AscDescCursorPagination
+from bugsink.api_mixins import ExpandViewSetMixin
 
 from .models import Project
 from .serializers import (
@@ -18,7 +20,7 @@ class ProjectPagination(AscDescCursorPagination):
     default_direction = "asc"
 
 
-class ProjectViewSet(viewsets.ModelViewSet):
+class ProjectViewSet(ExpandViewSetMixin, viewsets.ModelViewSet):
     """
     /api/canonical/0/projects/
     GET /projects/           → list ordered by name ASC, hides soft-deleted, optional ?team=<uuid> filter
diff --git a/projects/serializers.py b/projects/serializers.py
index 0bdbb20..0dcceca 100644
--- a/projects/serializers.py
+++ b/projects/serializers.py
@@ -2,6 +2,9 @@ from rest_framework import serializers
 from bugsink.api_fields import EnumLowercaseChoiceField
 
 from teams.models import Team
+from bugsink.api_mixins import ExpandableSerializerMixin
+
+from teams.serializers import TeamDetailSerializer
 from .models import Project, ProjectVisibility
 
 
@@ -28,7 +31,8 @@ class ProjectListSerializer(serializers.ModelSerializer):
         ]
 
 
-class ProjectDetailSerializer(serializers.ModelSerializer):
+class ProjectDetailSerializer(ExpandableSerializerMixin, serializers.ModelSerializer):
+    expandable_fields = {"team": TeamDetailSerializer}
     visibility = EnumLowercaseChoiceField(ProjectVisibility)
     dsn = serializers.CharField(read_only=True)
 
diff --git a/projects/test_api.py b/projects/test_api.py
index 7bf9366..c452567 100644
--- a/projects/test_api.py
+++ b/projects/test_api.py
@@ -1,4 +1,4 @@
-from django.test import TestCase
+from django.test import TestCase as DjangoTestCase
 from django.urls import reverse
 from rest_framework.test import APIClient
 
@@ -7,7 +7,7 @@ from teams.models import Team
 from projects.models import Project
 
 
-class ProjectApiTests(TestCase):
+class ProjectApiTests(DjangoTestCase):
     def setUp(self):
         self.client = APIClient()
         token = AuthToken.objects.create()
@@ -75,3 +75,64 @@ class ProjectApiTests(TestCase):
         p = Project.objects.create(team=self.team, name="Temp")
         r = self.client.delete(reverse("api:project-detail", args=[p.id]))
         self.assertEqual(r.status_code, 405)
+
+
+class ExpansionTests(DjangoTestCase):
+    """
+    Expansion tests are exercised via ProjectViewSet, but the intent is to validate the
+    generic ExpandableSerializerMixin infrastructure.
+    """
+
+    def setUp(self):
+        self.client = APIClient()
+        token = AuthToken.objects.create()
+        self.client.credentials(HTTP_AUTHORIZATION=f"Bearer {token.token}")
+        self.team = Team.objects.create(name="T")
+        self.project = Project.objects.create(name="P", team=self.team)
+
+    def _get(self, expand=None):
+        url = reverse("api:project-detail", args=[self.project.id])
+        qp = {"expand": expand} if expand else {}
+        return self.client.get(url, qp)
+
+    def test_default_no_expand(self):
+        r = self._get()
+        self.assertEqual(r.status_code, 200)
+        data = r.json()
+        # team is just rendered as a reference, not expanded
+        self.assertEqual(data["team"], str(self.team.id))
+
+    def test_with_valid_expand(self):
+        r = self._get("team")
+        self.assertEqual(r.status_code, 200)
+        data = r.json()
+        # team is fully expanded into object
+        self.assertEqual(data["team"]["id"], str(self.team.id))
+        self.assertEqual(data["team"]["name"], self.team.name)
+
+    def test_with_invalid_expand(self):
+        r = self._get("not_a_field")
+        self.assertEqual(r.status_code, 400)
+        self.assertEqual(
+            r.json(),
+            {"expand": ["Unknown field: not_a_field"]},
+        )
+
+    def test_with_comma_separated_expands(self):
+        # only 'team' is valid, 'not_a_field' should trigger 400
+        r = self._get("team,not_a_field")
+        self.assertEqual(r.status_code, 400)
+        self.assertEqual(
+            r.json(),
+            {"expand": ["Unknown field: not_a_field"]},
+        )
+
+    def test_expand_rejected_when_not_supported(self):
+        # ProjectListSerializer does not support expand
+        url = reverse("api:project-list")
+        r = self.client.get(url, {"expand": "team"})
+        self.assertEqual(r.status_code, 400)
+        self.assertEqual(
+            r.json(),
+            {"expand": ["Expansions are not supported on this endpoint."]},
+        )