feat(orchestrator): MS23-P1-002 InternalAgentProvider (#719)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/orchestrator/src/api/agents/agent-tree.service.spec.ts

@@ -7,6 +7,8 @@ describe("AgentTreeService", () => {
   let prisma: {
     agentSessionTree: {
       findMany: ReturnType<typeof vi.fn>;
+      count: ReturnType<typeof vi.fn>;
+      findUnique: ReturnType<typeof vi.fn>;
     };
   };
 
@@ -14,6 +16,8 @@ describe("AgentTreeService", () => {
     prisma = {
       agentSessionTree: {
         findMany: vi.fn(),
+        count: vi.fn(),
+        findUnique: vi.fn(),
       },
     };
 
@@ -24,6 +28,141 @@ describe("AgentTreeService", () => {
     vi.clearAllMocks();
   });
 
+  describe("listSessions", () => {
+    it("returns paginated sessions and cursor", async () => {
+      const sessions = [
+        {
+          id: "tree-2",
+          sessionId: "agent-2",
+          parentSessionId: null,
+          provider: "internal",
+          missionId: null,
+          taskId: "task-2",
+          taskSource: "queue",
+          agentType: "worker",
+          status: "running",
+          spawnedAt: new Date("2026-03-07T11:00:00.000Z"),
+          completedAt: null,
+          metadata: {},
+        },
+        {
+          id: "tree-1",
+          sessionId: "agent-1",
+          parentSessionId: null,
+          provider: "internal",
+          missionId: null,
+          taskId: "task-1",
+          taskSource: "queue",
+          agentType: "worker",
+          status: "running",
+          spawnedAt: new Date("2026-03-07T10:00:00.000Z"),
+          completedAt: null,
+          metadata: {},
+        },
+      ];
+
+      prisma.agentSessionTree.findMany.mockResolvedValue(sessions);
+      prisma.agentSessionTree.count.mockResolvedValue(7);
+
+      const result = await service.listSessions(undefined, 2);
+
+      expect(prisma.agentSessionTree.findMany).toHaveBeenCalledWith({
+        where: undefined,
+        orderBy: [{ spawnedAt: "desc" }, { sessionId: "desc" }],
+        take: 2,
+      });
+      expect(prisma.agentSessionTree.count).toHaveBeenCalledWith();
+      expect(result.sessions).toEqual(sessions);
+      expect(result.total).toBe(7);
+      expect(result.cursor).toBeTypeOf("string");
+    });
+
+    it("applies cursor filter when provided", async () => {
+      prisma.agentSessionTree.findMany.mockResolvedValue([]);
+      prisma.agentSessionTree.count.mockResolvedValue(0);
+
+      const cursorDate = "2026-03-07T10:00:00.000Z";
+      const cursorSessionId = "agent-5";
+      const cursor = Buffer.from(
+        JSON.stringify({
+          spawnedAt: cursorDate,
+          sessionId: cursorSessionId,
+        }),
+        "utf8"
+      ).toString("base64url");
+
+      await service.listSessions(cursor, 25);
+
+      expect(prisma.agentSessionTree.findMany).toHaveBeenCalledWith({
+        where: {
+          OR: [
+            {
+              spawnedAt: {
+                lt: new Date(cursorDate),
+              },
+            },
+            {
+              spawnedAt: new Date(cursorDate),
+              sessionId: {
+                lt: cursorSessionId,
+              },
+            },
+          ],
+        },
+        orderBy: [{ spawnedAt: "desc" }, { sessionId: "desc" }],
+        take: 25,
+      });
+    });
+
+    it("ignores invalid cursor values", async () => {
+      prisma.agentSessionTree.findMany.mockResolvedValue([]);
+      prisma.agentSessionTree.count.mockResolvedValue(0);
+
+      await service.listSessions("invalid-cursor", 10);
+
+      expect(prisma.agentSessionTree.findMany).toHaveBeenCalledWith({
+        where: undefined,
+        orderBy: [{ spawnedAt: "desc" }, { sessionId: "desc" }],
+        take: 10,
+      });
+    });
+  });
+
+  describe("getSession", () => {
+    it("returns matching session entry", async () => {
+      const session = {
+        id: "tree-1",
+        sessionId: "agent-123",
+        parentSessionId: null,
+        provider: "internal",
+        missionId: null,
+        taskId: "task-1",
+        taskSource: "queue",
+        agentType: "worker",
+        status: "running",
+        spawnedAt: new Date("2026-03-07T11:00:00.000Z"),
+        completedAt: null,
+        metadata: {},
+      };
+      prisma.agentSessionTree.findUnique.mockResolvedValue(session);
+
+      const result = await service.getSession("agent-123");
+
+      expect(prisma.agentSessionTree.findUnique).toHaveBeenCalledWith({
+        where: { sessionId: "agent-123" },
+      });
+      expect(result).toEqual(session);
+    });
+
+    it("returns null when session does not exist", async () => {
+      prisma.agentSessionTree.findUnique.mockResolvedValue(null);
+
+      const result = await service.getSession("agent-missing");
+
+      expect(result).toBeNull();
+    });
+  });
+
   describe("getTree", () => {
     it("returns mapped entries from Prisma", async () => {
       prisma.agentSessionTree.findMany.mockResolvedValue([