fix(#338): Add max concurrent agents limit

- Add MAX_CONCURRENT_AGENTS configuration (default: 20)
- Check current agent count before spawning
- Reject spawn requests with 429 Too Many Requests when limit reached
- Add comprehensive tests for limit enforcement

Refs #338

apps/orchestrator/src/config/orchestrator.config.spec.ts

@@ -83,4 +83,30 @@ describe("orchestratorConfig", () => {
       expect(config.valkey.url).toBe("redis://localhost:6379");
     });
   });
+
+  describe("spawner config", () => {
+    it("should use default maxConcurrentAgents of 20 when not set", () => {
+      delete process.env.MAX_CONCURRENT_AGENTS;
+
+      const config = orchestratorConfig();
+
+      expect(config.spawner.maxConcurrentAgents).toBe(20);
+    });
+
+    it("should use provided maxConcurrentAgents when MAX_CONCURRENT_AGENTS is set", () => {
+      process.env.MAX_CONCURRENT_AGENTS = "50";
+
+      const config = orchestratorConfig();
+
+      expect(config.spawner.maxConcurrentAgents).toBe(50);
+    });
+
+    it("should handle MAX_CONCURRENT_AGENTS of 10", () => {
+      process.env.MAX_CONCURRENT_AGENTS = "10";
+
+      const config = orchestratorConfig();
+
+      expect(config.spawner.maxConcurrentAgents).toBe(10);
+    });
+  });
 });

apps/orchestrator/src/config/orchestrator.config.ts

@@ -37,4 +37,7 @@ export const orchestratorConfig = registerAs("orchestrator", () => ({
   yolo: {
     enabled: process.env.YOLO_MODE === "true",
   },
+  spawner: {
+    maxConcurrentAgents: parseInt(process.env.MAX_CONCURRENT_AGENTS ?? "20", 10),
+  },
 }));