feat: add custom User-Agent header to identify CLI traffic

cmd/client_factory.go

@@ -8,10 +8,15 @@ import (
 	"github.com/coingecko/coingecko-cli/internal/ws"
 )
 
+// userAgent is the User-Agent header sent with all API and WebSocket requests.
+var userAgent = "coingecko-cli/" + version
+
 // newAPIClient is the factory used by command handlers to create API clients.
 // Tests override this to inject httptest-backed clients.
 var newAPIClient = func(cfg *config.Config) *api.Client {
-	return api.NewClient(cfg)
+	c := api.NewClient(cfg)
+	c.UserAgent = userAgent
+	return c
 }
 
 // loadConfig is the function used by command handlers to load configuration.
@@ -27,5 +32,7 @@ type Streamer interface {
 // newStreamer is the factory used by command handlers to create WebSocket clients.
 // Tests override this to inject test doubles.
 var newStreamer = func(cfg *config.Config, coinIDs []string) Streamer {
-	return ws.NewClient(cfg, coinIDs)
+	c := ws.NewClient(cfg, coinIDs)
+	c.UserAgent = userAgent
+	return c
 }

cmd/dryrun.go

@@ -81,6 +81,7 @@ func printDryRunFull(cfg *config.Config, cmdName, opKey, endpoint string, params
 		headers[headerKey] = masked
 	}
 	headers["Accept"] = "application/json"
+	headers["User-Agent"] = userAgent
 
 	out := dryRunOutput{
 		Method:     "GET",

internal/api/client.go

@@ -170,6 +170,7 @@ type Client struct {
 	http       *http.Client
 	baseURLVal string // override; empty = use cfg.BaseURL()
 	cfg        *config.Config
+	UserAgent  string // sent with every request; set by cmd layer
 }
 
 func NewClient(cfg *config.Config) *Client {
@@ -206,6 +207,7 @@ func (c *Client) get(ctx context.Context, path string, result any) error {
 	}
 	c.cfg.ApplyAuth(req)
 	req.Header.Set("Accept", "application/json")
+	req.Header.Set("User-Agent", c.UserAgent)
 
 	resp, err := c.http.Do(req)
 	if err != nil {

internal/api/client_test.go

@@ -21,6 +21,21 @@ func testClient(handler http.HandlerFunc) (*Client, *httptest.Server) {
 	return c, srv
 }
 
+func TestUserAgentHeader(t *testing.T) {
+	var gotUA string
+	c, srv := testClient(func(w http.ResponseWriter, r *http.Request) {
+		gotUA = r.Header.Get("User-Agent")
+		w.WriteHeader(200)
+		_, _ = w.Write([]byte("{}"))
+	})
+	defer srv.Close()
+
+	c.UserAgent = "coingecko-cli/v1.2.3"
+	var result map[string]any
+	_ = c.get(context.Background(), "/test", &result)
+	assert.Equal(t, "coingecko-cli/v1.2.3", gotUA)
+}
+
 func TestAuthHeadersSent(t *testing.T) {
 	var gotHeader string
 	c, srv := testClient(func(w http.ResponseWriter, r *http.Request) {

internal/ws/client.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"math/rand/v2"
+	"net/http"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -41,9 +42,10 @@ type CoinUpdate struct {
 
 // Client manages a WebSocket connection to CoinGecko's streaming API.
 type Client struct {
-	cfg     *config.Config
-	coinIDs []string
-	wsURL   string
+	cfg       *config.Config
+	coinIDs   []string
+	wsURL     string
+	UserAgent string // sent with WebSocket handshake; set by cmd layer
 
 	conn    *websocket.Conn
 	updates chan *CoinUpdate
@@ -134,11 +136,14 @@ func (c *Client) Close() error {
 func (c *Client) connect(ctx context.Context) error {
 	url := c.wsURL + "?x_cg_pro_api_key=" + c.cfg.APIKey
 
+	header := http.Header{}
+	header.Set("User-Agent", c.UserAgent)
+
 	dialer := websocket.Dialer{
 		HandshakeTimeout: 10 * time.Second,
 	}
 
-	conn, _, err := dialer.DialContext(ctx, url, nil)
+	conn, _, err := dialer.DialContext(ctx, url, header)
 	if err != nil {
 		return err
 	}

internal/ws/client_test.go

@@ -379,6 +379,44 @@ func TestConnect_APIKeyInQueryParam(t *testing.T) {
 	require.NoError(t, client.Close())
 }
 
+func TestConnect_UserAgentHeader(t *testing.T) {
+	var gotUA string
+	var mu sync.Mutex
+
+	srv := newTestWSServer(t, func(conn *websocket.Conn) {
+		happyHandshake(t, conn)
+		for {
+			if _, _, err := conn.ReadMessage(); err != nil {
+				return
+			}
+		}
+	})
+	// Wrap handler to capture User-Agent from the handshake request.
+	origHandler := srv.Config.Handler
+	srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		mu.Lock()
+		gotUA = r.Header.Get("User-Agent")
+		mu.Unlock()
+		origHandler.ServeHTTP(w, r)
+	})
+
+	client := NewClient(paidCfg(), []string{"bitcoin"})
+	client.SetURL(wsURL(srv))
+	client.UserAgent = "coingecko-cli/v1.2.3"
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	_, err := client.Connect(ctx)
+	require.NoError(t, err)
+
+	mu.Lock()
+	assert.Equal(t, "coingecko-cli/v1.2.3", gotUA)
+	mu.Unlock()
+
+	require.NoError(t, client.Close())
+}
+
 func TestCloseWithoutConnect(t *testing.T) {
 	client := NewClient(paidCfg(), []string{"bitcoin"})
 	// Close() should not hang if Connect() was never called.