fix: report a missing --file-part or --config file as a usage error

internal/cli/cli_test.go

@@ -865,6 +865,7 @@ func TestUsageErrors(t *testing.T) {
 		{"mutually exclusive targets", []string{"send", "-a", "http://x", "-e", "http://y", "hi"}},
 		{"malformed agent-card url", []string{"card", "get", "-a", "http://exa mple.com"}},
 		{"missing agent-card file", []string{"card", "get", "-a", "/no/such/card.json"}},
+		{"missing --file-part file", []string{"send", "-a", "http://x", "--file-part", "/no/such/file.txt"}},
 	}
 
 	for _, tt := range tests {

internal/clicfg/loader.go

@@ -22,6 +22,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/a2aproject/a2a-cli/internal/clierr"
 	"github.com/joho/godotenv"
 	"gopkg.in/yaml.v3"
 )
@@ -83,7 +84,7 @@ func loadLocal(opts LoadOpts) (*loadedFile, error) {
 	if opts.ConfigPath != "" {
 		values, err := loadConfigFile(opts.ConfigPath)
 		if err != nil {
-			return nil, fmt.Errorf("reading --config %q: %w", opts.ConfigPath, err)
+			return nil, clierr.Usage(fmt.Sprintf("reading --config %q: %v", opts.ConfigPath, err))
 		}
 		return &loadedFile{path: opts.ConfigPath, values: values}, nil
 	}

internal/clicfg/store_test.go

@@ -16,10 +16,13 @@ package clicfg
 
 import (
 	"bytes"
+	"errors"
 	"os"
 	"path/filepath"
 	"strings"
 	"testing"
+
+	"github.com/a2aproject/a2a-cli/internal/clierr"
 )
 
 func TestLoadStore(t *testing.T) {
@@ -217,6 +220,16 @@ func TestLoadStoreErrors(t *testing.T) {
 	}
 }
 
+func TestLoadMissingConfigIsUsageError(t *testing.T) {
+	t.Parallel()
+
+	_, err := Load(LoadOpts{ConfigPath: filepath.Join(t.TempDir(), "missing.yaml")})
+	var ce *clierr.Error
+	if !errors.As(err, &ce) || ce.Code != clierr.CodeUsage {
+		t.Fatalf("Load() error = %v, want a usage error", err)
+	}
+}
+
 func TestLoadWalksUpForLocalEnv(t *testing.T) {
 	t.Parallel()
 

internal/flagparse/parts.go

@@ -23,6 +23,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/a2aproject/a2a-cli/internal/clierr"
 	"github.com/a2aproject/a2a-go/v2/a2a"
 	"github.com/spf13/pflag"
 )
@@ -118,7 +119,7 @@ func buildFilePart(ref, mediaType string) (*a2a.Part, error) {
 	path := strings.TrimPrefix(ref, "file://")
 	data, err := os.ReadFile(path)
 	if err != nil {
-		return nil, fmt.Errorf("reading --file-part %q: %w", ref, err)
+		return nil, clierr.Usage(fmt.Sprintf("reading --file-part %q: %v", ref, err))
 	}
 	p := a2a.NewRawPart(data)
 	p.Filename = filepath.Base(path)