feat: add MessageChainString for clearer error context

errors.go

@@ -199,6 +199,15 @@ outer:
 	return buffer.String()
 }
 
+// MessageChainString returns a formatted string of the full message chain.
+// Each message in the chain is joined with " -> ".
+func (p *Error) MessageChainString() string {
+	if p == nil {
+		return ""
+	}
+	return strings.Join(p.MessageChain, " -> ")
+}
+
 // VerboseString returns the error message, stack trace and params
 func (p *Error) VerboseString() string {
 	return fmt.Sprintf("%s\nParams: %+v\n%s", p.Error(), p.Params, p.StackString())

errors_test.go

@@ -604,6 +604,31 @@ func TestStackStringChasesCausalChain(t *testing.T) {
 	assert.Contains(t, ss, "failyFunction")
 }
 
+func TestMessageChainString(t *testing.T) {
+	t.Run("simple chain", func(t *testing.T) {
+		err := &Error{
+			Code:         ErrInternalService,
+			MessageChain: []string{"top-level", "cause"},
+		}
+		out := err.MessageChainString()
+		assert.Equal(t, "top-level -> cause", out)
+	})
+
+	t.Run("single message", func(t *testing.T) {
+		err := &Error{
+			Code:         ErrNotFound,
+			MessageChain: []string{"only one"},
+		}
+		out := err.MessageChainString()
+		assert.Equal(t, "only one", out)
+	})
+
+	t.Run("nil error returns empty string", func(t *testing.T) {
+		var err *Error
+		assert.Equal(t, "", err.MessageChainString())
+	})
+}
+
 func TestCircularErrorProducesFiniteOutputWithStackFrames(t *testing.T) {
 	orig := failyFunction()
 	err := Augment(orig, "something may be up", nil)