fix(downloader): persist completed aria2 seeds

downloader/internal/engine/aria2.go

@@ -62,10 +62,24 @@ func (a Aria2) Start(ctx context.Context) (*exec.Cmd, error) {
 	if err != nil {
 		return nil, err
 	}
+	args, err := a.startArgs(rpcURL.port)
+	if err != nil {
+		return nil, err
+	}
+	cmd := exec.Command(path, args...)
+	configureEngineProcess(cmd)
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+	go func() { _ = cmd.Wait() }()
+	return cmd, nil
+}
+
+func (a Aria2) startArgs(rpcPort string) ([]string, error) {
 	args := []string{
 		"--enable-rpc=true",
 		"--rpc-listen-all=false",
-		"--rpc-listen-port=" + rpcURL.port,
+		"--rpc-listen-port=" + rpcPort,
 		"--dir=" + a.Dir,
 		"--continue=true",
 		"--allow-overwrite=true",
@@ -85,18 +99,13 @@ func (a Aria2) Start(ctx context.Context) (*exec.Cmd, error) {
 			"--input-file="+sessionPath,
 			"--save-session="+sessionPath,
 			"--save-session-interval=30",
+			"--force-save=true",
 		)
 	}
 	if a.Secret != "" {
 		args = append(args, "--rpc-secret="+a.Secret)
 	}
-	cmd := exec.Command(path, args...)
-	configureEngineProcess(cmd)
-	if err := cmd.Start(); err != nil {
-		return nil, err
-	}
-	go func() { _ = cmd.Wait() }()
-	return cmd, nil
+	return args, nil
 }
 
 func (a Aria2) Check(ctx context.Context) error {

downloader/internal/engine/engine_test.go

@@ -74,6 +74,25 @@ func TestHTTPRejectsMagnet(t *testing.T) {
 	}
 }
 
+func TestAria2StartArgsForceSaveCompletedSeeds(t *testing.T) {
+	stateDir := t.TempDir()
+	args, err := (Aria2{Dir: t.TempDir(), StateDir: stateDir}).startArgs("6800")
+	if err != nil {
+		t.Fatal(err)
+	}
+	joined := strings.Join(args, "\n")
+	for _, expected := range []string{
+		"--input-file=" + filepath.Join(stateDir, "aria2.session"),
+		"--save-session=" + filepath.Join(stateDir, "aria2.session"),
+		"--save-session-interval=30",
+		"--force-save=true",
+	} {
+		if !strings.Contains(joined, expected) {
+			t.Fatalf("expected aria2 args to contain %q, got %v", expected, args)
+		}
+	}
+}
+
 func TestHTTPDownloadResumesExistingFile(t *testing.T) {
 	var rangeHeader string
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {