feat(orchestrator): add subagent session tree endpoint

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

apps/orchestrator/src/agent-ingestion/agent-ingestion.service.ts

@@ -25,14 +25,14 @@ export class AgentIngestionService {
       where: { sessionId: agentId },
       create: {
         sessionId: agentId,
-        parentSessionId: parentAgentId,
+        parentSessionId: parentAgentId ?? null,
         missionId,
         taskId,
         agentType,
         status: "spawning",
       },
       update: {
-        parentSessionId: parentAgentId,
+        parentSessionId: parentAgentId ?? null,
         missionId,
         taskId,
         agentType,

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

@@ -0,0 +1,30 @@
+import { Injectable } from "@nestjs/common";
+import { PrismaService } from "../../prisma/prisma.service";
+import { AgentTreeResponseDto } from "./dto/agent-tree-response.dto";
+
+@Injectable()
+export class AgentTreeService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  async getTree(): Promise<AgentTreeResponseDto[]> {
+    const entries = await this.prisma.agentSessionTree.findMany({
+      orderBy: { spawnedAt: "desc" },
+      take: 200,
+    });
+
+    const response: AgentTreeResponseDto[] = [];
+    for (const entry of entries) {
+      response.push({
+        sessionId: entry.sessionId,
+        parentSessionId: entry.parentSessionId ?? null,
+        status: entry.status,
+        agentType: entry.agentType ?? null,
+        taskSource: entry.taskSource ?? null,
+        spawnedAt: entry.spawnedAt.toISOString(),
+        completedAt: entry.completedAt?.toISOString() ?? null,
+      });
+    }
+
+    return response;
+  }
+}

apps/orchestrator/src/api/agents/agents-killswitch.controller.spec.ts

@@ -7,6 +7,7 @@ import { KillswitchService } from "../../killswitch/killswitch.service";
 import { AgentEventsService } from "./agent-events.service";
 import { AgentMessagesService } from "./agent-messages.service";
 import { AgentControlService } from "./agent-control.service";
+import { AgentTreeService } from "./agent-tree.service";
 import type { KillAllResult } from "../../killswitch/killswitch.service";
 
 describe("AgentsController - Killswitch Endpoints", () => {
@@ -41,6 +42,9 @@ describe("AgentsController - Killswitch Endpoints", () => {
     pauseAgent: ReturnType<typeof vi.fn>;
     resumeAgent: ReturnType<typeof vi.fn>;
   };
+  let mockTreeService: {
+    getTree: ReturnType<typeof vi.fn>;
+  };
 
   beforeEach(() => {
     mockKillswitchService = {
@@ -89,6 +93,10 @@ describe("AgentsController - Killswitch Endpoints", () => {
       resumeAgent: vi.fn().mockResolvedValue(undefined),
     };
 
+    mockTreeService = {
+      getTree: vi.fn().mockResolvedValue([]),
+    };
+
     controller = new AgentsController(
       mockQueueService as unknown as QueueService,
       mockSpawnerService as unknown as AgentSpawnerService,
@@ -96,7 +104,8 @@ describe("AgentsController - Killswitch Endpoints", () => {
       mockKillswitchService as unknown as KillswitchService,
       mockEventsService as unknown as AgentEventsService,
       mockMessagesService as unknown as AgentMessagesService,
-      mockControlService as unknown as AgentControlService
+      mockControlService as unknown as AgentControlService,
+      mockTreeService as unknown as AgentTreeService
     );
   });
 

apps/orchestrator/src/api/agents/agents.controller.spec.ts

@@ -6,6 +6,7 @@ import { KillswitchService } from "../../killswitch/killswitch.service";
 import { AgentEventsService } from "./agent-events.service";
 import { AgentMessagesService } from "./agent-messages.service";
 import { AgentControlService } from "./agent-control.service";
+import { AgentTreeService } from "./agent-tree.service";
 import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
 
 describe("AgentsController", () => {
@@ -42,6 +43,9 @@ describe("AgentsController", () => {
     pauseAgent: ReturnType<typeof vi.fn>;
     resumeAgent: ReturnType<typeof vi.fn>;
   };
+  let treeService: {
+    getTree: ReturnType<typeof vi.fn>;
+  };
 
   beforeEach(() => {
     // Create mock services
@@ -93,6 +97,10 @@ describe("AgentsController", () => {
       resumeAgent: vi.fn().mockResolvedValue(undefined),
     };
 
+    treeService = {
+      getTree: vi.fn().mockResolvedValue([]),
+    };
+
     // Create controller with mocked services
     controller = new AgentsController(
       queueService as unknown as QueueService,
@@ -101,7 +109,8 @@ describe("AgentsController", () => {
       killswitchService as unknown as KillswitchService,
       eventsService as unknown as AgentEventsService,
       messagesService as unknown as AgentMessagesService,
-      controlService as unknown as AgentControlService
+      controlService as unknown as AgentControlService,
+      treeService as unknown as AgentTreeService
     );
   });
 
@@ -113,6 +122,27 @@ describe("AgentsController", () => {
     expect(controller).toBeDefined();
   });
 
+  describe("getAgentTree", () => {
+    it("should return tree entries", async () => {
+      const entries = [
+        {
+          sessionId: "agent-1",
+          parentSessionId: null,
+          status: "running",
+          agentType: "worker",
+          taskSource: "internal",
+          spawnedAt: "2026-03-07T00:00:00.000Z",
+          completedAt: null,
+        },
+      ];
+
+      treeService.getTree.mockResolvedValue(entries);
+
+      await expect(controller.getAgentTree()).resolves.toEqual(entries);
+      expect(treeService.getTree).toHaveBeenCalledTimes(1);
+    });
+  });
+
   describe("listAgents", () => {
     it("should return empty array when no agents exist", () => {
       // Arrange

apps/orchestrator/src/api/agents/agents.controller.ts

@@ -30,6 +30,8 @@ import { AgentEventsService } from "./agent-events.service";
 import { GetMessagesQueryDto } from "./dto/get-messages-query.dto";
 import { AgentMessagesService } from "./agent-messages.service";
 import { AgentControlService } from "./agent-control.service";
+import { AgentTreeService } from "./agent-tree.service";
+import { AgentTreeResponseDto } from "./dto/agent-tree-response.dto";
 import { InjectAgentDto } from "./dto/inject-agent.dto";
 import { PauseAgentDto, ResumeAgentDto } from "./dto/control-agent.dto";
 
@@ -56,7 +58,8 @@ export class AgentsController {
     private readonly killswitchService: KillswitchService,
     private readonly eventsService: AgentEventsService,
     private readonly messagesService: AgentMessagesService,
-    private readonly agentControlService: AgentControlService
+    private readonly agentControlService: AgentControlService,
+    private readonly agentTreeService: AgentTreeService
   ) {}
 
   /**
@@ -78,6 +81,7 @@ export class AgentsController {
       // Spawn agent using spawner service
       const spawnResponse = this.spawnerService.spawnAgent({
         taskId: dto.taskId,
+        ...(dto.parentAgentId !== undefined ? { parentAgentId: dto.parentAgentId } : {}),
         agentType: dto.agentType,
         context: dto.context,
       });
@@ -152,6 +156,13 @@ export class AgentsController {
     };
   }
 
+  @Get("tree")
+  @UseGuards(OrchestratorApiKeyGuard)
+  @Throttle({ default: { limit: 200, ttl: 60000 } })
+  async getAgentTree(): Promise<AgentTreeResponseDto[]> {
+    return this.agentTreeService.getTree();
+  }
+
   /**
    * List all agents
    * @returns Array of all agent sessions with their status

apps/orchestrator/src/api/agents/agents.module.ts

@@ -9,6 +9,7 @@ import { AgentEventsService } from "./agent-events.service";
 import { PrismaModule } from "../../prisma/prisma.module";
 import { AgentMessagesService } from "./agent-messages.service";
 import { AgentControlService } from "./agent-control.service";
+import { AgentTreeService } from "./agent-tree.service";
 
 @Module({
   imports: [QueueModule, SpawnerModule, KillswitchModule, ValkeyModule, PrismaModule],
@@ -18,6 +19,7 @@ import { AgentControlService } from "./agent-control.service";
     AgentEventsService,
     AgentMessagesService,
     AgentControlService,
+    AgentTreeService,
   ],
 })
 export class AgentsModule {}

apps/orchestrator/src/api/agents/dto/agent-tree-response.dto.ts

@@ -0,0 +1,9 @@
+export class AgentTreeResponseDto {
+  sessionId!: string;
+  parentSessionId!: string | null;
+  status!: string;
+  agentType!: string | null;
+  taskSource!: string | null;
+  spawnedAt!: string;
+  completedAt!: string | null;
+}

apps/orchestrator/src/api/agents/dto/spawn-agent.dto.ts

@@ -116,6 +116,10 @@ export class SpawnAgentDto {
   @IsOptional()
   @IsIn(["strict", "standard", "minimal", "custom"])
   gateProfile?: GateProfileType;
+
+  @IsOptional()
+  @IsString()
+  parentAgentId?: string;
 }
 
 /**

apps/orchestrator/src/spawner/agent-spawner.service.ts

@@ -115,7 +115,13 @@ export class AgentSpawnerService implements OnModuleDestroy {
     }
 
     void this.agentIngestionService
-      .recordAgentSpawned(agentId, undefined, undefined, request.taskId, request.agentType)
+      .recordAgentSpawned(
+        agentId,
+        request.parentAgentId,
+        undefined,
+        request.taskId,
+        request.agentType
+      )
       .catch((error: unknown) => {
         const errorMessage = error instanceof Error ? error.message : String(error);
         this.logger.error(`Failed to record spawned ingestion for ${agentId}: ${errorMessage}`);

apps/orchestrator/src/spawner/types/agent-spawner.types.ts

@@ -40,6 +40,8 @@ export interface SpawnAgentOptions {
 export interface SpawnAgentRequest {
   /** Unique task identifier */
   taskId: string;
+  /** Optional parent session identifier for subagent lineage */
+  parentAgentId?: string;
   /** Type of agent to spawn */
   agentType: AgentType;
   /** Context for task execution */

docs/TASKS.md

@@ -124,8 +124,8 @@ Target version: `v0.0.23`
 | MS23-P0-001 | done        | p0-foundation | Prisma schema: AgentConversationMessage, AgentSessionTree, AgentProviderConfig, OperatorAuditLog | #693  | api          | feat/ms23-p0-schema    | —                                               | MS23-P0-002,MS23-P0-003,MS23-P0-004,MS23-P0-005,MS23-P1-001 | codex | 2026-03-06 | 2026-03-06   | 15K      | —    | taskSource field per mosaic-queue note in PRD |
 | MS23-P0-002 | done        | p0-foundation | Agent message ingestion: wire spawner/lifecycle to write messages to DB                          | #693  | orchestrator | feat/ms23-p0-ingestion | MS23-P0-001                                     | MS23-P0-006                                                 | codex | 2026-03-06 | 2026-03-07      | 20K      | —    |                                               |
 | MS23-P0-003 | done        | p0-foundation | Orchestrator API: GET /agents/:id/messages + SSE stream endpoint                                 | #693  | orchestrator | feat/ms23-p0-stream    | MS23-P0-001                                     | MS23-P0-006                                                 | codex | 2026-03-06 | 2026-03-07      | 20K      | —    |                                               |
-| MS23-P0-004 | in-progress | p0-foundation | Orchestrator API: POST /agents/:id/inject + pause/resume endpoints                               | #693  | orchestrator | feat/ms23-p0-controls  | MS23-P0-001                                     | MS23-P0-006                                                 | codex | 2026-03-07     | —            | 15K      | —    |                                               |
-| MS23-P0-005 | not-started | p0-foundation | Subagent tree: parentAgentId on spawn registration + GET /agents/tree                            | #693  | orchestrator | feat/ms23-p0-tree      | MS23-P0-001                                     | MS23-P0-006                                                 | —     | —          | —            | 15K      | —    |                                               |
+| MS23-P0-004 | done        | p0-foundation | Orchestrator API: POST /agents/:id/inject + pause/resume endpoints                               | #693  | orchestrator | feat/ms23-p0-controls  | MS23-P0-001                                     | MS23-P0-006                                                 | codex | 2026-03-07 | 2026-03-07 | 15K      | —    |                                               |
+| MS23-P0-005 | in-progress | p0-foundation | Subagent tree: parentAgentId on spawn registration + GET /agents/tree                            | #693  | orchestrator | feat/ms23-p0-tree      | MS23-P0-001                                     | MS23-P0-006                                                 | —     | —          | —            | 15K      | —    |                                               |
 | MS23-P0-006 | not-started | p0-foundation | Unit + integration tests for all P0 orchestrator endpoints                                       | #693  | orchestrator | test/ms23-p0           | MS23-P0-002,MS23-P0-003,MS23-P0-004,MS23-P0-005 | MS23-P1-001                                                 | —     | —          | —            | 20K      | —    | Phase 0 gate: SSE stream verified via curl    |
 
 ### Phase 1 — Provider Interface (Plugin Architecture)