diff --git a/backend/tests/e2e/test_agent_workflows.py b/backend/tests/e2e/test_agent_workflows.py
new file mode 100644
index 0000000..c5a1a8c
--- /dev/null
+++ b/backend/tests/e2e/test_agent_workflows.py
@@ -0,0 +1,646 @@
+"""
+Agent E2E Workflow Tests.
+
+Tests complete workflows for AI agents including:
+- Agent type management (admin-only)
+- Agent instance spawning and lifecycle
+- Agent status transitions (pause/resume/terminate)
+- Authorization and access control
+
+Usage:
+    make test-e2e          # Run all E2E tests
+"""
+
+from uuid import uuid4
+
+import pytest
+
+pytestmark = [
+    pytest.mark.e2e,
+    pytest.mark.postgres,
+    pytest.mark.asyncio,
+]
+
+
+class TestAgentTypesAdminWorkflows:
+    """Test agent type management (admin-only operations)."""
+
+    async def test_create_agent_type_requires_superuser(self, e2e_client):
+        """Test that creating agent types requires superuser privileges."""
+        # Register regular user
+        email = f"regular-{uuid4().hex[:8]}@example.com"
+        password = "RegularPass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Regular",
+                "last_name": "User",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        # Try to create agent type
+        response = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "name": "Test Agent",
+                "slug": f"test-agent-{uuid4().hex[:8]}",
+                "personality_prompt": "You are a helpful assistant.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+
+        assert response.status_code == 403
+
+    async def test_superuser_can_create_agent_type(self, e2e_client, e2e_superuser):
+        """Test that superuser can create and manage agent types."""
+        slug = f"test-type-{uuid4().hex[:8]}"
+
+        # Create agent type
+        create_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Product Owner Agent",
+                "slug": slug,
+                "description": "A product owner agent for requirements gathering",
+                "expertise": ["requirements", "user_stories", "prioritization"],
+                "personality_prompt": "You are a product owner focused on delivering value.",
+                "primary_model": "claude-3-opus",
+                "fallback_models": ["claude-3-sonnet"],
+                "model_params": {"temperature": 0.7, "max_tokens": 4000},
+                "mcp_servers": ["knowledge-base"],
+                "is_active": True,
+            },
+        )
+
+        assert create_resp.status_code == 201, f"Failed: {create_resp.text}"
+        agent_type = create_resp.json()
+
+        assert agent_type["name"] == "Product Owner Agent"
+        assert agent_type["slug"] == slug
+        assert agent_type["primary_model"] == "claude-3-opus"
+        assert agent_type["is_active"] is True
+        assert "requirements" in agent_type["expertise"]
+
+    async def test_list_agent_types_public(self, e2e_client, e2e_superuser):
+        """Test that any authenticated user can list agent types."""
+        # First create an agent type as superuser
+        slug = f"list-test-{uuid4().hex[:8]}"
+        await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": f"List Test Agent {slug}",
+                "slug": slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+
+        # Register regular user
+        email = f"lister-{uuid4().hex[:8]}@example.com"
+        password = "ListerPass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "List",
+                "last_name": "User",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        # List agent types as regular user
+        list_resp = await e2e_client.get(
+            "/api/v1/agent-types",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+
+        assert list_resp.status_code == 200
+        data = list_resp.json()
+        assert "data" in data
+        assert "pagination" in data
+        assert data["pagination"]["total"] >= 1
+
+    async def test_get_agent_type_by_slug(self, e2e_client, e2e_superuser):
+        """Test getting agent type by slug."""
+        slug = f"slug-test-{uuid4().hex[:8]}"
+
+        # Create agent type
+        await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": f"Slug Test {slug}",
+                "slug": slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+
+        # Get by slug (route is /slug/{slug}, not /by-slug/{slug})
+        get_resp = await e2e_client.get(
+            f"/api/v1/agent-types/slug/{slug}",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+
+        assert get_resp.status_code == 200
+        data = get_resp.json()
+        assert data["slug"] == slug
+
+    async def test_update_agent_type(self, e2e_client, e2e_superuser):
+        """Test updating an agent type."""
+        slug = f"update-test-{uuid4().hex[:8]}"
+
+        # Create agent type
+        create_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Original Name",
+                "slug": slug,
+                "personality_prompt": "Original prompt.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+        agent_type_id = create_resp.json()["id"]
+
+        # Update agent type
+        update_resp = await e2e_client.patch(
+            f"/api/v1/agent-types/{agent_type_id}",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Updated Name",
+                "description": "Added description",
+            },
+        )
+
+        assert update_resp.status_code == 200
+        updated = update_resp.json()
+        assert updated["name"] == "Updated Name"
+        assert updated["description"] == "Added description"
+        assert updated["personality_prompt"] == "Original prompt."  # Unchanged
+
+
+class TestAgentInstanceWorkflows:
+    """Test agent instance spawning and lifecycle."""
+
+    async def test_spawn_agent_workflow(self, e2e_client, e2e_superuser):
+        """Test complete workflow: create type -> create project -> spawn agent."""
+        # 1. Create agent type as superuser
+        type_slug = f"spawn-test-type-{uuid4().hex[:8]}"
+        type_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Spawn Test Agent",
+                "slug": type_slug,
+                "personality_prompt": "You are a helpful agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+        assert type_resp.status_code == 201
+        agent_type = type_resp.json()
+        agent_type_id = agent_type["id"]
+
+        # 2. Create a project (superuser can create projects too)
+        project_slug = f"spawn-test-project-{uuid4().hex[:8]}"
+        project_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"name": "Spawn Test Project", "slug": project_slug},
+        )
+        assert project_resp.status_code == 201
+        project = project_resp.json()
+        project_id = project["id"]
+
+        # 3. Spawn agent instance
+        spawn_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "agent_type_id": agent_type_id,
+                "project_id": project_id,
+                "name": "My PO Agent",
+            },
+        )
+
+        assert spawn_resp.status_code == 201, f"Failed: {spawn_resp.text}"
+        agent = spawn_resp.json()
+
+        assert agent["name"] == "My PO Agent"
+        assert agent["status"] == "idle"
+        assert agent["project_id"] == project_id
+        assert agent["agent_type_id"] == agent_type_id
+
+    async def test_list_project_agents(self, e2e_client, e2e_superuser):
+        """Test listing agents in a project."""
+        # Setup: Create agent type and project
+        type_slug = f"list-agents-type-{uuid4().hex[:8]}"
+        type_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "List Agents Type",
+                "slug": type_slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+        agent_type_id = type_resp.json()["id"]
+
+        project_slug = f"list-agents-project-{uuid4().hex[:8]}"
+        project_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"name": "List Agents Project", "slug": project_slug},
+        )
+        project_id = project_resp.json()["id"]
+
+        # Spawn multiple agents
+        for i in range(3):
+            await e2e_client.post(
+                f"/api/v1/projects/{project_id}/agents",
+                headers={
+                    "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+                },
+                json={
+                    "agent_type_id": agent_type_id,
+                    "project_id": project_id,
+                    "name": f"Agent {i + 1}",
+                },
+            )
+
+        # List agents
+        list_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}/agents",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+
+        assert list_resp.status_code == 200
+        data = list_resp.json()
+        assert data["pagination"]["total"] == 3
+        assert len(data["data"]) == 3
+
+
+class TestAgentLifecycle:
+    """Test agent lifecycle operations (pause/resume/terminate)."""
+
+    async def test_agent_pause_and_resume(self, e2e_client, e2e_superuser):
+        """Test pausing and resuming an agent."""
+        # Setup: Create agent type, project, and agent
+        type_slug = f"pause-test-type-{uuid4().hex[:8]}"
+        type_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Pause Test Type",
+                "slug": type_slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+        agent_type_id = type_resp.json()["id"]
+
+        project_slug = f"pause-test-project-{uuid4().hex[:8]}"
+        project_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"name": "Pause Test Project", "slug": project_slug},
+        )
+        project_id = project_resp.json()["id"]
+
+        spawn_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "agent_type_id": agent_type_id,
+                "project_id": project_id,
+                "name": "Pausable Agent",
+            },
+        )
+        agent_id = spawn_resp.json()["id"]
+        assert spawn_resp.json()["status"] == "idle"
+
+        # Pause agent
+        pause_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents/{agent_id}/pause",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+        assert pause_resp.status_code == 200, f"Failed: {pause_resp.text}"
+        assert pause_resp.json()["status"] == "paused"
+
+        # Resume agent
+        resume_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents/{agent_id}/resume",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+        assert resume_resp.status_code == 200, f"Failed: {resume_resp.text}"
+        assert resume_resp.json()["status"] == "idle"
+
+    async def test_agent_terminate(self, e2e_client, e2e_superuser):
+        """Test terminating an agent."""
+        # Setup
+        type_slug = f"terminate-type-{uuid4().hex[:8]}"
+        type_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Terminate Type",
+                "slug": type_slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+        agent_type_id = type_resp.json()["id"]
+
+        project_slug = f"terminate-project-{uuid4().hex[:8]}"
+        project_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"name": "Terminate Project", "slug": project_slug},
+        )
+        project_id = project_resp.json()["id"]
+
+        spawn_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "agent_type_id": agent_type_id,
+                "project_id": project_id,
+                "name": "To Be Terminated",
+            },
+        )
+        agent_id = spawn_resp.json()["id"]
+
+        # Terminate agent (returns MessageResponse, not agent status)
+        terminate_resp = await e2e_client.delete(
+            f"/api/v1/projects/{project_id}/agents/{agent_id}",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+
+        assert terminate_resp.status_code == 200
+        assert "message" in terminate_resp.json()
+
+        # Verify terminated agent cannot be resumed (returns 400 or 422)
+        resume_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents/{agent_id}/resume",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+        assert resume_resp.status_code in [400, 422]  # Invalid transition
+
+
+class TestAgentAccessControl:
+    """Test agent access control and authorization."""
+
+    async def test_user_cannot_access_other_project_agents(
+        self, e2e_client, e2e_superuser
+    ):
+        """Test that users cannot access agents in projects they don't own."""
+        # Superuser creates agent type
+        type_slug = f"access-type-{uuid4().hex[:8]}"
+        type_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Access Type",
+                "slug": type_slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+        agent_type_id = type_resp.json()["id"]
+
+        # Superuser creates project and spawns agent
+        project_slug = f"protected-project-{uuid4().hex[:8]}"
+        project_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"name": "Protected Project", "slug": project_slug},
+        )
+        project_id = project_resp.json()["id"]
+
+        spawn_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "agent_type_id": agent_type_id,
+                "project_id": project_id,
+                "name": "Protected Agent",
+            },
+        )
+        agent_id = spawn_resp.json()["id"]
+
+        # Create a different user
+        email = f"other-user-{uuid4().hex[:8]}@example.com"
+        password = "OtherPass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Other",
+                "last_name": "User",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        other_tokens = login_resp.json()
+
+        # Other user tries to access the agent
+        get_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}/agents/{agent_id}",
+            headers={"Authorization": f"Bearer {other_tokens['access_token']}"},
+        )
+
+        # Should be forbidden or not found
+        assert get_resp.status_code in [403, 404]
+
+    async def test_cannot_spawn_with_inactive_agent_type(
+        self, e2e_client, e2e_superuser
+    ):
+        """Test that agents cannot be spawned from inactive agent types."""
+        # Create agent type
+        type_slug = f"inactive-type-{uuid4().hex[:8]}"
+        type_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Inactive Type",
+                "slug": type_slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+                "is_active": True,
+            },
+        )
+        agent_type_id = type_resp.json()["id"]
+
+        # Deactivate the agent type
+        await e2e_client.patch(
+            f"/api/v1/agent-types/{agent_type_id}",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"is_active": False},
+        )
+
+        # Create project
+        project_slug = f"inactive-spawn-project-{uuid4().hex[:8]}"
+        project_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"name": "Inactive Spawn Project", "slug": project_slug},
+        )
+        project_id = project_resp.json()["id"]
+
+        # Try to spawn agent with inactive type
+        spawn_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "agent_type_id": agent_type_id,
+                "project_id": project_id,
+                "name": "Should Fail",
+            },
+        )
+
+        # 422 is correct for validation errors per REST conventions
+        assert spawn_resp.status_code == 422
+
+
+class TestAgentMetrics:
+    """Test agent metrics endpoint."""
+
+    async def test_get_agent_metrics(self, e2e_client, e2e_superuser):
+        """Test retrieving agent metrics."""
+        # Setup
+        type_slug = f"metrics-type-{uuid4().hex[:8]}"
+        type_resp = await e2e_client.post(
+            "/api/v1/agent-types",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "name": "Metrics Type",
+                "slug": type_slug,
+                "personality_prompt": "Test agent.",
+                "primary_model": "claude-3-sonnet",
+            },
+        )
+        agent_type_id = type_resp.json()["id"]
+
+        project_slug = f"metrics-project-{uuid4().hex[:8]}"
+        project_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={"name": "Metrics Project", "slug": project_slug},
+        )
+        project_id = project_resp.json()["id"]
+
+        spawn_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/agents",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "agent_type_id": agent_type_id,
+                "project_id": project_id,
+                "name": "Metrics Agent",
+            },
+        )
+        agent_id = spawn_resp.json()["id"]
+
+        # Get metrics
+        metrics_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}/agents/{agent_id}/metrics",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+
+        assert metrics_resp.status_code == 200
+        metrics = metrics_resp.json()
+
+        # Verify AgentInstanceMetrics structure
+        assert "total_instances" in metrics
+        assert "active_instances" in metrics
+        assert "idle_instances" in metrics
+        assert "total_tasks_completed" in metrics
+        assert "total_tokens_used" in metrics
+        assert "total_cost_incurred" in metrics
diff --git a/backend/tests/e2e/test_mcp_workflows.py b/backend/tests/e2e/test_mcp_workflows.py
new file mode 100644
index 0000000..264bfca
--- /dev/null
+++ b/backend/tests/e2e/test_mcp_workflows.py
@@ -0,0 +1,460 @@
+"""
+MCP and Context Engine E2E Workflow Tests.
+
+Tests complete workflows involving MCP servers and the Context Engine
+against real PostgreSQL. These tests verify:
+- MCP server listing and tool discovery
+- Context engine operations
+- Admin-only MCP operations with proper authentication
+- Error handling for MCP operations
+
+Usage:
+    make test-e2e          # Run all E2E tests
+"""
+
+from uuid import uuid4
+
+import pytest
+
+pytestmark = [
+    pytest.mark.e2e,
+    pytest.mark.postgres,
+    pytest.mark.asyncio,
+]
+
+
+class TestMCPServerDiscovery:
+    """Test MCP server listing and discovery workflows."""
+
+    async def test_list_mcp_servers(self, e2e_client):
+        """Test listing MCP servers returns expected configuration."""
+        response = await e2e_client.get("/api/v1/mcp/servers")
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        # Should have servers configured
+        assert "servers" in data
+        assert "total" in data
+        assert isinstance(data["servers"], list)
+
+        # Should have at least llm-gateway and knowledge-base
+        server_names = [s["name"] for s in data["servers"]]
+        assert "llm-gateway" in server_names
+        assert "knowledge-base" in server_names
+
+    async def test_list_all_mcp_tools(self, e2e_client):
+        """Test listing all tools from all MCP servers."""
+        response = await e2e_client.get("/api/v1/mcp/tools")
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert "tools" in data
+        assert "total" in data
+        assert isinstance(data["tools"], list)
+
+    async def test_mcp_health_check(self, e2e_client):
+        """Test MCP health check returns server status."""
+        response = await e2e_client.get("/api/v1/mcp/health")
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert "servers" in data
+        assert "healthy_count" in data
+        assert "unhealthy_count" in data
+        assert "total" in data
+
+    async def test_list_circuit_breakers(self, e2e_client):
+        """Test listing circuit breaker status."""
+        response = await e2e_client.get("/api/v1/mcp/circuit-breakers")
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert "circuit_breakers" in data
+        assert isinstance(data["circuit_breakers"], list)
+
+
+class TestMCPServerTools:
+    """Test MCP server tool listing."""
+
+    async def test_list_llm_gateway_tools(self, e2e_client):
+        """Test listing tools from LLM Gateway server."""
+        response = await e2e_client.get("/api/v1/mcp/servers/llm-gateway/tools")
+
+        # May return 200 with tools or 404 if server not connected
+        assert response.status_code in [200, 404, 502]
+
+        if response.status_code == 200:
+            data = response.json()
+            assert "tools" in data
+            assert "total" in data
+
+    async def test_list_knowledge_base_tools(self, e2e_client):
+        """Test listing tools from Knowledge Base server."""
+        response = await e2e_client.get("/api/v1/mcp/servers/knowledge-base/tools")
+
+        # May return 200 with tools or 404/502 if server not connected
+        assert response.status_code in [200, 404, 502]
+
+        if response.status_code == 200:
+            data = response.json()
+            assert "tools" in data
+            assert "total" in data
+
+    async def test_invalid_server_returns_404(self, e2e_client):
+        """Test that invalid server name returns 404."""
+        response = await e2e_client.get("/api/v1/mcp/servers/nonexistent-server/tools")
+
+        assert response.status_code == 404
+
+
+class TestContextEngineWorkflows:
+    """Test Context Engine operations."""
+
+    async def test_context_engine_health(self, e2e_client):
+        """Test context engine health endpoint."""
+        response = await e2e_client.get("/api/v1/context/health")
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert data["status"] == "healthy"
+        assert "mcp_connected" in data
+        assert "cache_enabled" in data
+
+    async def test_get_token_budget_claude_sonnet(self, e2e_client):
+        """Test getting token budget for Claude 3 Sonnet."""
+        response = await e2e_client.get("/api/v1/context/budget/claude-3-sonnet")
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert data["model"] == "claude-3-sonnet"
+        assert "total_tokens" in data
+        assert "system_tokens" in data
+        assert "knowledge_tokens" in data
+        assert "conversation_tokens" in data
+        assert "tool_tokens" in data
+        assert "response_reserve" in data
+
+        # Verify budget allocation makes sense
+        assert data["total_tokens"] > 0
+        total_allocated = (
+            data["system_tokens"]
+            + data["knowledge_tokens"]
+            + data["conversation_tokens"]
+            + data["tool_tokens"]
+            + data["response_reserve"]
+        )
+        assert total_allocated <= data["total_tokens"]
+
+    async def test_get_token_budget_with_custom_max(self, e2e_client):
+        """Test getting token budget with custom max tokens."""
+        response = await e2e_client.get(
+            "/api/v1/context/budget/claude-3-sonnet",
+            params={"max_tokens": 50000},
+        )
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert data["model"] == "claude-3-sonnet"
+        # Custom max should be respected or capped
+        assert data["total_tokens"] <= 50000
+
+    async def test_count_tokens(self, e2e_client):
+        """Test token counting endpoint."""
+        response = await e2e_client.post(
+            "/api/v1/context/count-tokens",
+            json={
+                "content": "Hello, this is a test message for token counting.",
+                "model": "claude-3-sonnet",
+            },
+        )
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert "token_count" in data
+        assert data["token_count"] > 0
+        assert data["model"] == "claude-3-sonnet"
+
+
+class TestAdminMCPOperations:
+    """Test admin-only MCP operations require authentication."""
+
+    async def test_tool_call_requires_auth(self, e2e_client):
+        """Test that tool execution requires authentication."""
+        response = await e2e_client.post(
+            "/api/v1/mcp/call",
+            json={
+                "server": "llm-gateway",
+                "tool": "count_tokens",
+                "arguments": {"text": "test"},
+            },
+        )
+
+        # Should require authentication
+        assert response.status_code in [401, 403]
+
+    async def test_circuit_reset_requires_auth(self, e2e_client):
+        """Test that circuit breaker reset requires authentication."""
+        response = await e2e_client.post(
+            "/api/v1/mcp/circuit-breakers/llm-gateway/reset"
+        )
+
+        assert response.status_code in [401, 403]
+
+    async def test_server_reconnect_requires_auth(self, e2e_client):
+        """Test that server reconnect requires authentication."""
+        response = await e2e_client.post("/api/v1/mcp/servers/llm-gateway/reconnect")
+
+        assert response.status_code in [401, 403]
+
+    async def test_context_stats_requires_auth(self, e2e_client):
+        """Test that context stats requires authentication."""
+        response = await e2e_client.get("/api/v1/context/stats")
+
+        assert response.status_code in [401, 403]
+
+    async def test_context_assemble_requires_auth(self, e2e_client):
+        """Test that context assembly requires authentication."""
+        response = await e2e_client.post(
+            "/api/v1/context/assemble",
+            json={
+                "project_id": "test-project",
+                "agent_id": "test-agent",
+                "query": "test query",
+                "model": "claude-3-sonnet",
+            },
+        )
+
+        assert response.status_code in [401, 403]
+
+    async def test_cache_invalidate_requires_auth(self, e2e_client):
+        """Test that cache invalidation requires authentication."""
+        response = await e2e_client.post("/api/v1/context/cache/invalidate")
+
+        assert response.status_code in [401, 403]
+
+
+class TestAdminMCPWithAuthentication:
+    """Test admin MCP operations with superuser authentication."""
+
+    async def test_superuser_can_get_context_stats(self, e2e_client, e2e_superuser):
+        """Test that superuser can get context engine stats."""
+        response = await e2e_client.get(
+            "/api/v1/context/stats",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert "cache" in data
+        assert "settings" in data
+
+    @pytest.mark.skip(
+        reason="Requires MCP servers (llm-gateway, knowledge-base) to be running"
+    )
+    async def test_superuser_can_assemble_context(self, e2e_client, e2e_superuser):
+        """Test that superuser can assemble context."""
+        response = await e2e_client.post(
+            "/api/v1/context/assemble",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "project_id": f"test-project-{uuid4().hex[:8]}",
+                "agent_id": f"test-agent-{uuid4().hex[:8]}",
+                "query": "What is the status of the project?",
+                "model": "claude-3-sonnet",
+                "system_prompt": "You are a helpful assistant.",
+                "compress": True,
+                "use_cache": False,
+            },
+        )
+
+        assert response.status_code == 200, f"Failed: {response.text}"
+        data = response.json()
+
+        assert "content" in data
+        assert "total_tokens" in data
+        assert "context_count" in data
+        assert "budget_used_percent" in data
+        assert "metadata" in data
+
+    async def test_superuser_can_invalidate_cache(self, e2e_client, e2e_superuser):
+        """Test that superuser can invalidate cache."""
+        response = await e2e_client.post(
+            "/api/v1/context/cache/invalidate",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            params={"project_id": "test-project"},
+        )
+
+        assert response.status_code == 204
+
+    async def test_regular_user_cannot_access_admin_operations(self, e2e_client):
+        """Test that regular (non-superuser) cannot access admin operations."""
+        email = f"regular-{uuid4().hex[:8]}@example.com"
+        password = "RegularUser123!"
+
+        # Register regular user
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Regular",
+                "last_name": "User",
+            },
+        )
+
+        # Login
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        # Try to access admin endpoint
+        response = await e2e_client.get(
+            "/api/v1/context/stats",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+
+        # Should be forbidden for non-superuser
+        assert response.status_code == 403
+
+
+class TestMCPInputValidation:
+    """Test input validation for MCP endpoints."""
+
+    async def test_server_name_max_length(self, e2e_client):
+        """Test that server name has max length validation."""
+        long_name = "a" * 100  # Exceeds 64 char limit
+
+        response = await e2e_client.get(f"/api/v1/mcp/servers/{long_name}/tools")
+
+        assert response.status_code == 422
+
+    async def test_server_name_invalid_characters(self, e2e_client):
+        """Test that server name rejects invalid characters."""
+        invalid_name = "server@name!invalid"
+
+        response = await e2e_client.get(f"/api/v1/mcp/servers/{invalid_name}/tools")
+
+        assert response.status_code == 422
+
+    async def test_token_count_empty_content(self, e2e_client):
+        """Test token counting with empty content."""
+        response = await e2e_client.post(
+            "/api/v1/context/count-tokens",
+            json={"content": ""},
+        )
+
+        # Empty content is valid, should return 0 tokens
+        if response.status_code == 200:
+            data = response.json()
+            assert data["token_count"] == 0
+        else:
+            # Or it might be rejected as invalid
+            assert response.status_code == 422
+
+
+class TestMCPWorkflowIntegration:
+    """Test complete MCP workflows end-to-end."""
+
+    async def test_discovery_to_budget_workflow(self, e2e_client):
+        """Test complete workflow: discover servers -> check budget -> ready for use."""
+        # 1. Discover available servers
+        servers_resp = await e2e_client.get("/api/v1/mcp/servers")
+        assert servers_resp.status_code == 200
+        servers = servers_resp.json()["servers"]
+        assert len(servers) > 0
+
+        # 2. Check context engine health
+        health_resp = await e2e_client.get("/api/v1/context/health")
+        assert health_resp.status_code == 200
+        health = health_resp.json()
+        assert health["status"] == "healthy"
+
+        # 3. Get token budget for a model
+        budget_resp = await e2e_client.get("/api/v1/context/budget/claude-3-sonnet")
+        assert budget_resp.status_code == 200
+        budget = budget_resp.json()
+
+        # 4. Verify system is ready for context assembly
+        assert budget["total_tokens"] > 0
+        assert health["mcp_connected"] is True
+
+    @pytest.mark.skip(
+        reason="Requires MCP servers (llm-gateway, knowledge-base) to be running"
+    )
+    async def test_full_context_assembly_workflow(self, e2e_client, e2e_superuser):
+        """Test complete context assembly workflow with superuser."""
+        project_id = f"e2e-project-{uuid4().hex[:8]}"
+        agent_id = f"e2e-agent-{uuid4().hex[:8]}"
+
+        # 1. Check budget before assembly
+        budget_resp = await e2e_client.get("/api/v1/context/budget/claude-3-sonnet")
+        assert budget_resp.status_code == 200
+        _ = budget_resp.json()  # Verify valid response
+
+        # 2. Count tokens in sample content
+        count_resp = await e2e_client.post(
+            "/api/v1/context/count-tokens",
+            json={"content": "This is a test message for context assembly."},
+        )
+        assert count_resp.status_code == 200
+        token_count = count_resp.json()["token_count"]
+        assert token_count > 0
+
+        # 3. Assemble context
+        assemble_resp = await e2e_client.post(
+            "/api/v1/context/assemble",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+            json={
+                "project_id": project_id,
+                "agent_id": agent_id,
+                "query": "Summarize the current project status",
+                "model": "claude-3-sonnet",
+                "system_prompt": "You are a project management assistant.",
+                "task_description": "Generate a status report",
+                "conversation_history": [
+                    {"role": "user", "content": "What's the project status?"},
+                    {
+                        "role": "assistant",
+                        "content": "Let me check the current status.",
+                    },
+                ],
+                "compress": True,
+                "use_cache": False,
+            },
+        )
+        assert assemble_resp.status_code == 200
+        assembled = assemble_resp.json()
+
+        # 4. Verify assembly results
+        assert assembled["total_tokens"] > 0
+        assert assembled["context_count"] > 0
+        assert assembled["budget_used_percent"] > 0
+        assert assembled["budget_used_percent"] <= 100
+
+        # 5. Get stats to verify the operation was recorded
+        stats_resp = await e2e_client.get(
+            "/api/v1/context/stats",
+            headers={
+                "Authorization": f"Bearer {e2e_superuser['tokens']['access_token']}"
+            },
+        )
+        assert stats_resp.status_code == 200
diff --git a/backend/tests/e2e/test_project_workflows.py b/backend/tests/e2e/test_project_workflows.py
new file mode 100644
index 0000000..5218f14
--- /dev/null
+++ b/backend/tests/e2e/test_project_workflows.py
@@ -0,0 +1,684 @@
+"""
+Project and Agent E2E Workflow Tests.
+
+Tests complete project management workflows with real PostgreSQL:
+- Project CRUD and lifecycle management
+- Agent spawning and lifecycle
+- Issue management within projects
+- Sprint planning and execution
+
+Usage:
+    make test-e2e          # Run all E2E tests
+"""
+
+from datetime import date, timedelta
+from uuid import uuid4
+
+import pytest
+
+pytestmark = [
+    pytest.mark.e2e,
+    pytest.mark.postgres,
+    pytest.mark.asyncio,
+]
+
+
+class TestProjectCRUDWorkflows:
+    """Test complete project CRUD workflows."""
+
+    async def test_create_project_workflow(self, e2e_client):
+        """Test creating a project as authenticated user."""
+        # Register and login
+        email = f"project-owner-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Project",
+                "last_name": "Owner",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        # Create project
+        project_slug = f"test-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "name": "E2E Test Project",
+                "slug": project_slug,
+                "description": "A project for E2E testing",
+                "autonomy_level": "milestone",
+            },
+        )
+
+        assert create_resp.status_code == 201, f"Failed: {create_resp.text}"
+        project = create_resp.json()
+        assert project["name"] == "E2E Test Project"
+        assert project["slug"] == project_slug
+        assert project["status"] == "active"
+        assert project["agent_count"] == 0
+        assert project["issue_count"] == 0
+
+    async def test_list_projects_only_shows_owned(self, e2e_client):
+        """Test that users only see their own projects."""
+        # Create two users with projects
+        users = []
+        for i in range(2):
+            email = f"user-{i}-{uuid4().hex[:8]}@example.com"
+            password = "SecurePass123!"
+
+            await e2e_client.post(
+                "/api/v1/auth/register",
+                json={
+                    "email": email,
+                    "password": password,
+                    "first_name": f"User{i}",
+                    "last_name": "Test",
+                },
+            )
+            login_resp = await e2e_client.post(
+                "/api/v1/auth/login",
+                json={"email": email, "password": password},
+            )
+            tokens = login_resp.json()
+
+            # Each user creates their own project
+            project_slug = f"user{i}-project-{uuid4().hex[:8]}"
+            await e2e_client.post(
+                "/api/v1/projects",
+                headers={"Authorization": f"Bearer {tokens['access_token']}"},
+                json={
+                    "name": f"User {i} Project",
+                    "slug": project_slug,
+                },
+            )
+            users.append({"email": email, "tokens": tokens, "slug": project_slug})
+
+        # User 0 should only see their project
+        list_resp = await e2e_client.get(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {users[0]['tokens']['access_token']}"},
+        )
+        assert list_resp.status_code == 200
+        data = list_resp.json()
+        slugs = [p["slug"] for p in data["data"]]
+        assert users[0]["slug"] in slugs
+        assert users[1]["slug"] not in slugs
+
+    async def test_project_lifecycle_pause_resume(self, e2e_client):
+        """Test pausing and resuming a project."""
+        # Setup user and project
+        email = f"lifecycle-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Lifecycle",
+                "last_name": "Test",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        project_slug = f"lifecycle-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Lifecycle Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Pause the project
+        pause_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/pause",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert pause_resp.status_code == 200
+        assert pause_resp.json()["status"] == "paused"
+
+        # Resume the project
+        resume_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/resume",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert resume_resp.status_code == 200
+        assert resume_resp.json()["status"] == "active"
+
+    async def test_project_archive(self, e2e_client):
+        """Test archiving a project (soft delete)."""
+        # Setup user and project
+        email = f"archive-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Archive",
+                "last_name": "Test",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        project_slug = f"archive-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Archive Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Archive the project
+        archive_resp = await e2e_client.delete(
+            f"/api/v1/projects/{project_id}",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert archive_resp.status_code == 200
+        assert archive_resp.json()["success"] is True
+
+        # Verify project is archived
+        get_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert get_resp.status_code == 200
+        assert get_resp.json()["status"] == "archived"
+
+
+class TestIssueWorkflows:
+    """Test issue management workflows within projects."""
+
+    async def test_create_and_list_issues(self, e2e_client):
+        """Test creating and listing issues in a project."""
+        # Setup user and project
+        email = f"issue-test-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Issue",
+                "last_name": "Tester",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        project_slug = f"issue-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Issue Test Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Create multiple issues
+        issues = []
+        for i in range(3):
+            issue_resp = await e2e_client.post(
+                f"/api/v1/projects/{project_id}/issues",
+                headers={"Authorization": f"Bearer {tokens['access_token']}"},
+                json={
+                    "project_id": project_id,
+                    "title": f"Test Issue {i + 1}",
+                    "body": f"Description for issue {i + 1}",
+                    "priority": ["low", "medium", "high"][i],
+                },
+            )
+            assert issue_resp.status_code == 201, f"Failed: {issue_resp.text}"
+            issues.append(issue_resp.json())
+
+        # List issues
+        list_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}/issues",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert list_resp.status_code == 200
+        data = list_resp.json()
+        assert data["pagination"]["total"] == 3
+
+    async def test_issue_status_transitions(self, e2e_client):
+        """Test issue status workflow transitions."""
+        # Setup user and project
+        email = f"status-test-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Status",
+                "last_name": "Tester",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        project_slug = f"status-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Status Test Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Create issue
+        issue_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/issues",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "project_id": project_id,
+                "title": "Status Workflow Issue",
+                "body": "Testing status transitions",
+            },
+        )
+        issue = issue_resp.json()
+        issue_id = issue["id"]
+        assert issue["status"] == "open"
+
+        # Transition through statuses
+        for new_status in ["in_progress", "in_review", "closed"]:
+            update_resp = await e2e_client.patch(
+                f"/api/v1/projects/{project_id}/issues/{issue_id}",
+                headers={"Authorization": f"Bearer {tokens['access_token']}"},
+                json={"status": new_status},
+            )
+            assert update_resp.status_code == 200, f"Failed: {update_resp.text}"
+            assert update_resp.json()["status"] == new_status
+
+    async def test_issue_filtering(self, e2e_client):
+        """Test issue filtering by status and priority."""
+        # Setup user and project
+        email = f"filter-test-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Filter",
+                "last_name": "Tester",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        project_slug = f"filter-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Filter Test Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Create issues with different priorities
+        for priority in ["low", "medium", "high"]:
+            await e2e_client.post(
+                f"/api/v1/projects/{project_id}/issues",
+                headers={"Authorization": f"Bearer {tokens['access_token']}"},
+                json={
+                    "project_id": project_id,
+                    "title": f"{priority.title()} Priority Issue",
+                    "priority": priority,
+                },
+            )
+
+        # Filter by high priority
+        filter_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}/issues",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            params={"priority": "high"},
+        )
+        assert filter_resp.status_code == 200
+        data = filter_resp.json()
+        assert data["pagination"]["total"] == 1
+        assert data["data"][0]["priority"] == "high"
+
+
+class TestSprintWorkflows:
+    """Test sprint planning and execution workflows."""
+
+    async def test_sprint_lifecycle(self, e2e_client):
+        """Test complete sprint lifecycle: plan -> start -> complete."""
+        # Setup user and project
+        email = f"sprint-test-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Sprint",
+                "last_name": "Tester",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        project_slug = f"sprint-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Sprint Test Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Create sprint
+        today = date.today()
+        sprint_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/sprints",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "project_id": project_id,
+                "name": "Sprint 1",
+                "number": 1,
+                "goal": "Complete initial features",
+                "start_date": today.isoformat(),
+                "end_date": (today + timedelta(days=14)).isoformat(),
+            },
+        )
+        assert sprint_resp.status_code == 201, f"Failed: {sprint_resp.text}"
+        sprint = sprint_resp.json()
+        sprint_id = sprint["id"]
+        assert sprint["status"] == "planned"
+
+        # Start sprint
+        start_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/sprints/{sprint_id}/start",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert start_resp.status_code == 200, f"Failed: {start_resp.text}"
+        assert start_resp.json()["status"] == "active"
+
+        # Complete sprint
+        complete_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/sprints/{sprint_id}/complete",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert complete_resp.status_code == 200, f"Failed: {complete_resp.text}"
+        assert complete_resp.json()["status"] == "completed"
+
+    async def test_add_issues_to_sprint(self, e2e_client):
+        """Test adding issues to a sprint."""
+        # Setup user and project
+        email = f"sprint-issues-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "SprintIssues",
+                "last_name": "Tester",
+            },
+        )
+        login_resp = await e2e_client.post(
+            "/api/v1/auth/login",
+            json={"email": email, "password": password},
+        )
+        tokens = login_resp.json()
+
+        project_slug = f"sprint-issues-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Sprint Issues Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Create sprint
+        today = date.today()
+        sprint_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/sprints",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "project_id": project_id,
+                "name": "Sprint 1",
+                "number": 1,
+                "start_date": today.isoformat(),
+                "end_date": (today + timedelta(days=14)).isoformat(),
+            },
+        )
+        assert sprint_resp.status_code == 201, f"Failed: {sprint_resp.text}"
+        sprint = sprint_resp.json()
+        sprint_id = sprint["id"]
+
+        # Create issue
+        issue_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/issues",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "project_id": project_id,
+                "title": "Sprint Issue",
+                "story_points": 5,
+            },
+        )
+        issue = issue_resp.json()
+        issue_id = issue["id"]
+
+        # Add issue to sprint
+        add_resp = await e2e_client.post(
+            f"/api/v1/projects/{project_id}/sprints/{sprint_id}/issues",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            params={"issue_id": issue_id},
+        )
+        assert add_resp.status_code == 200, f"Failed: {add_resp.text}"
+
+        # Verify issue is in sprint
+        issue_check = await e2e_client.get(
+            f"/api/v1/projects/{project_id}/issues/{issue_id}",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert issue_check.json()["sprint_id"] == sprint_id
+
+
+class TestCrossEntityValidation:
+    """Test validation across related entities."""
+
+    async def test_cannot_access_other_users_project(self, e2e_client):
+        """Test that users cannot access projects they don't own."""
+        # Create two users
+        owner_email = f"owner-{uuid4().hex[:8]}@example.com"
+        other_email = f"other-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        # Register owner
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": owner_email,
+                "password": password,
+                "first_name": "Owner",
+                "last_name": "User",
+            },
+        )
+        owner_tokens = (
+            await e2e_client.post(
+                "/api/v1/auth/login",
+                json={"email": owner_email, "password": password},
+            )
+        ).json()
+
+        # Register other user
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": other_email,
+                "password": password,
+                "first_name": "Other",
+                "last_name": "User",
+            },
+        )
+        other_tokens = (
+            await e2e_client.post(
+                "/api/v1/auth/login",
+                json={"email": other_email, "password": password},
+            )
+        ).json()
+
+        # Owner creates project
+        project_slug = f"private-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {owner_tokens['access_token']}"},
+            json={"name": "Private Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Other user tries to access
+        access_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}",
+            headers={"Authorization": f"Bearer {other_tokens['access_token']}"},
+        )
+        assert access_resp.status_code == 403
+
+    async def test_duplicate_project_slug_rejected(self, e2e_client):
+        """Test that duplicate project slugs are rejected."""
+        email = f"dup-test-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Dup",
+                "last_name": "Tester",
+            },
+        )
+        tokens = (
+            await e2e_client.post(
+                "/api/v1/auth/login",
+                json={"email": email, "password": password},
+            )
+        ).json()
+
+        slug = f"unique-slug-{uuid4().hex[:8]}"
+
+        # First creation should succeed
+        resp1 = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "First Project", "slug": slug},
+        )
+        assert resp1.status_code == 201
+
+        # Second creation with same slug should fail
+        resp2 = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Second Project", "slug": slug},
+        )
+        assert resp2.status_code == 409  # Conflict
+
+
+class TestIssueStats:
+    """Test issue statistics endpoints."""
+
+    async def test_issue_stats_aggregation(self, e2e_client):
+        """Test that issue stats are correctly aggregated."""
+        email = f"stats-test-{uuid4().hex[:8]}@example.com"
+        password = "SecurePass123!"
+
+        await e2e_client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": email,
+                "password": password,
+                "first_name": "Stats",
+                "last_name": "Tester",
+            },
+        )
+        tokens = (
+            await e2e_client.post(
+                "/api/v1/auth/login",
+                json={"email": email, "password": password},
+            )
+        ).json()
+
+        project_slug = f"stats-project-{uuid4().hex[:8]}"
+        create_resp = await e2e_client.post(
+            "/api/v1/projects",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={"name": "Stats Project", "slug": project_slug},
+        )
+        project = create_resp.json()
+        project_id = project["id"]
+
+        # Create issues with different priorities and story points
+        await e2e_client.post(
+            f"/api/v1/projects/{project_id}/issues",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "project_id": project_id,
+                "title": "High Priority",
+                "priority": "high",
+                "story_points": 8,
+            },
+        )
+        await e2e_client.post(
+            f"/api/v1/projects/{project_id}/issues",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+            json={
+                "project_id": project_id,
+                "title": "Low Priority",
+                "priority": "low",
+                "story_points": 2,
+            },
+        )
+
+        # Get stats
+        stats_resp = await e2e_client.get(
+            f"/api/v1/projects/{project_id}/issues/stats",
+            headers={"Authorization": f"Bearer {tokens['access_token']}"},
+        )
+        assert stats_resp.status_code == 200
+        stats = stats_resp.json()
+        assert stats["total"] == 2
+        assert stats["total_story_points"] == 10