fix: client-cancelled GET /v0/servers returns 499 without error log (#1335)

Maps context.Canceled from ListServers to 499 and skips the error-level log on client disconnect.

Merged as-is per maintainer decision; known follow-up tracked in #1337 (500-path error-detail leak + WriteHeader claim correction + nits).

Author: advancedresearcharray

internal/api/handlers/v0/list_errors.go

@@ -0,0 +1,21 @@
+package v0
+
+import (
+	"context"
+	"errors"
+	"log"
+
+	"github.com/danielgtaylor/huma/v2"
+)
+
+// ListServersError maps ListServers failures; client disconnects must not log as 500s.
+func ListServersError(ctx context.Context, err error) error {
+	if err == nil {
+		return nil
+	}
+	if errors.Is(err, context.Canceled) || errors.Is(ctx.Err(), context.Canceled) {
+		return huma.NewError(499, "Client closed request", err)
+	}
+	log.Printf("list servers failed: %v", err)
+	return huma.Error500InternalServerError("Failed to get registry list", err)
+}

internal/api/handlers/v0/list_errors_test.go

@@ -0,0 +1,31 @@
+package v0_test
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/danielgtaylor/huma/v2"
+	v0 "github.com/modelcontextprotocol/registry/internal/api/handlers/v0"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestListServersError_clientCanceled(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	err := v0.ListServersError(ctx, errors.New("error iterating rows: context canceled"))
+	require.Error(t, err)
+	var se huma.StatusError
+	require.True(t, errors.As(err, &se))
+	assert.Equal(t, 499, se.GetStatus())
+}
+
+func TestListServersError_realFailure(t *testing.T) {
+	err := v0.ListServersError(context.Background(), errors.New("database unavailable"))
+	require.Error(t, err)
+	var se huma.StatusError
+	require.True(t, errors.As(err, &se))
+	assert.Equal(t, 500, se.GetStatus())
+}

internal/api/handlers/v0/servers.go

@@ -132,8 +132,7 @@ func RegisterServersEndpoints(api huma.API, pathPrefix string, registry service.
 		// Get paginated results with filtering
 		servers, nextCursor, err := registry.ListServers(ctx, filter, input.Cursor, input.Limit)
 		if err != nil {
-			log.Printf("list servers failed: %v", err)
-			return nil, huma.Error500InternalServerError("Failed to get registry list")
+			return nil, ListServersError(ctx, err)
 		}
 
 		// Convert []*ServerResponse to []ServerResponse