diff --git a/server/package.json b/server/package.json
index a800ad4..3468f84 100644
--- a/server/package.json
+++ b/server/package.json
@@ -8,7 +8,8 @@
     "dev": "tsx src/index.ts",
     "build": "tsc -p tsconfig.json",
     "start": "node dist/index.js",
-    "typecheck": "tsc -p tsconfig.json --noEmit"
+    "typecheck": "tsc -p tsconfig.json --noEmit",
+    "test": "vitest run"
   },
   "dependencies": {
     "@fastify/cors": "^11.2.0",
diff --git a/server/src/lib/DownloadManager.ts b/server/src/lib/DownloadManager.ts
index ac5781d..12e897c 100644
--- a/server/src/lib/DownloadManager.ts
+++ b/server/src/lib/DownloadManager.ts
@@ -23,12 +23,22 @@ export type DownloadTask = {
 };
 
 // Map to store active task metadata in memory (for speed)
-// Ideally this would be persisted to JSON in the session folder for crash recovery
+// Ideally this would be persisted to JSON in the session folder for crash recovery.
+// As tasks de uma sessão são removidas quando ela expira (ver construtor), então o
+// mapa não cresce sem limite num servidor de longa duração.
 const tasks = new Map<string, DownloadTask>();
 
 export class DownloadManager {
 
-    constructor(private globalAgent: Dispatcher) { }
+    constructor(private globalAgent: Dispatcher) {
+        sessionManager.onDestroy((sessionId) => this.dropSession(sessionId));
+    }
+
+    private dropSession(sessionId: string) {
+        for (const [id, task] of tasks) {
+            if (task.sessionId === sessionId) tasks.delete(id);
+        }
+    }
 
     public getTasks(sessionId: string): DownloadTask[] {
         return Array.from(tasks.values()).filter(t => t.sessionId === sessionId);
diff --git a/server/src/lib/SessionManager.ts b/server/src/lib/SessionManager.ts
index 93bf5a8..2c02b78 100644
--- a/server/src/lib/SessionManager.ts
+++ b/server/src/lib/SessionManager.ts
@@ -21,6 +21,7 @@ type SessionData = {
 
 export class SessionManager {
     private sessions: Map<string, SessionData> = new Map();
+    private destroyListeners: Array<(sessionId: string) => void> = [];
 
     constructor() {
         // Ensure storage root exists
@@ -29,7 +30,8 @@ export class SessionManager {
         }
 
         // Start Garbage Collector
-        setInterval(() => this.cleanup(), 60 * 1000); // Check every minute
+        // unref: o coletor não deve impedir o processo de encerrar (nem os testes).
+        setInterval(() => this.cleanup(), 60 * 1000).unref(); // Check every minute
         console.log("[SessionManager] Garbage Collector started.");
     }
 
@@ -89,6 +91,14 @@ export class SessionManager {
         }
     }
 
+    /**
+     * Registra um callback chamado quando uma sessão é destruída (expiração),
+     * para quem guarda estado por sessão poder descartá-lo.
+     */
+    public onDestroy(listener: (sessionId: string) => void) {
+        this.destroyListeners.push(listener);
+    }
+
     /**
      * Removes expired sessions and deletes their files.
      */
@@ -128,6 +138,7 @@ export class SessionManager {
 
     private destroySession(id: string) {
         this.sessions.delete(id);
+        for (const listener of this.destroyListeners) listener(id);
         const path = this.getSessionPath(id);
         if (existsSync(path)) {
             try {
diff --git a/server/test/helpers.ts b/server/test/helpers.ts
new file mode 100644
index 0000000..03e3eb7
--- /dev/null
+++ b/server/test/helpers.ts
@@ -0,0 +1,18 @@
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { vi } from "vitest";
+
+/**
+ * Carrega os módulos do servidor com um STORAGE_ROOT temporário.
+ * O SessionManager lê a variável e cria o singleton no import, então o módulo
+ * precisa ser reimportado a cada teste.
+ */
+export async function loadModules() {
+    const storageRoot = mkdtempSync(join(tmpdir(), "downloader-test-"));
+    process.env.STORAGE_ROOT = storageRoot;
+    vi.resetModules();
+    const { sessionManager } = await import("../src/lib/SessionManager.js");
+    const { DownloadManager } = await import("../src/lib/DownloadManager.js");
+    return { storageRoot, sessionManager, DownloadManager };
+}
diff --git a/server/test/sessions.test.ts b/server/test/sessions.test.ts
new file mode 100644
index 0000000..a93ca00
--- /dev/null
+++ b/server/test/sessions.test.ts
@@ -0,0 +1,74 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { createServer, type Server } from "node:http";
+import type { AddressInfo } from "node:net";
+import { existsSync, readdirSync, rmSync } from "node:fs";
+import { Agent } from "undici";
+import { loadModules } from "./helpers.js";
+
+const HOUR = 60 * 60 * 1000;
+
+let origin: Server;
+let originUrl: string;
+
+beforeEach(async () => {
+    vi.useFakeTimers({ toFake: ["setInterval", "Date"] });
+    origin = createServer((_req, res) => {
+        res.setHeader("content-length", "5");
+        res.end("hello");
+    });
+    await new Promise<void>((done) => origin.listen(0, "127.0.0.1", done));
+    originUrl = `http://127.0.0.1:${(origin.address() as AddressInfo).port}/file.txt`;
+});
+
+afterEach(async () => {
+    vi.useRealTimers();
+    await new Promise((done) => origin.close(done));
+});
+
+async function waitForStatus(
+    read: () => string | undefined,
+    wanted: string,
+) {
+    for (let i = 0; i < 500 && read() !== wanted; i++) {
+        await new Promise((done) => setImmediate(done));
+    }
+    expect(read()).toBe(wanted);
+}
+
+describe("tasks e sessões", () => {
+    it("descarta as tasks e os arquivos quando a sessão expira", async () => {
+        const { sessionManager, DownloadManager, storageRoot } = await loadModules();
+        const manager = new DownloadManager(new Agent());
+
+        const session = sessionManager.getSession();
+        const task = await manager.queueDownload(session.id, originUrl);
+        await waitForStatus(() => manager.getTask(task.id)?.status, "completed");
+        expect(readdirSync(`${storageRoot}/${session.id}`)).toHaveLength(1);
+
+        vi.setSystemTime(Date.now() + HOUR + 1000);
+        vi.advanceTimersByTime(60_000); // dispara o coletor
+
+        expect(manager.getTask(task.id)).toBeUndefined();
+        expect(manager.getTasks(session.id)).toEqual([]);
+        expect(existsSync(`${storageRoot}/${session.id}`)).toBe(false);
+        rmSync(storageRoot, { recursive: true, force: true });
+    });
+
+    it("mantém as tasks de outras sessões ainda ativas", async () => {
+        const { sessionManager, DownloadManager, storageRoot } = await loadModules();
+        const manager = new DownloadManager(new Agent());
+
+        const expiring = sessionManager.getSession();
+        await manager.queueDownload(expiring.id, originUrl);
+
+        vi.setSystemTime(Date.now() + HOUR - 1000);
+        const alive = sessionManager.getSession(); // criada perto do fim da outra
+        const kept = await manager.queueDownload(alive.id, originUrl);
+        vi.setSystemTime(Date.now() + 2000);
+        vi.advanceTimersByTime(60_000);
+
+        expect(manager.getTasks(expiring.id)).toEqual([]);
+        expect(manager.getTask(kept.id)).toBeDefined();
+        rmSync(storageRoot, { recursive: true, force: true });
+    });
+});