fix: strip control bytes when copying logs to clipboard (#4762)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/container/sanitize.go

@@ -0,0 +1,19 @@
+package container
+
+import "strings"
+
+// stripControlBytes removes C0 control characters except tab (\x09), newline
+// (\x0a) and carriage return (\x0d). A NUL byte terminates the clipboard string
+// on Windows, dropping everything after it.
+func stripControlBytes(r rune) rune {
+	if (r >= 0x00 && r <= 0x08) || r == 0x0b || r == 0x0c || (r >= 0x0e && r <= 0x1f) {
+		return -1
+	}
+	return r
+}
+
+// SanitizeForPlainText strips ANSI escape sequences and control bytes so log
+// text is safe to copy to the clipboard or open in a text editor.
+func SanitizeForPlainText(str string) string {
+	return strings.Map(stripControlBytes, StripANSI(str))
+}

internal/container/sanitize_test.go

@@ -0,0 +1,25 @@
+package container
+
+import "testing"
+
+func TestSanitizeForPlainText(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{"strips NUL bytes that truncate clipboard text on Windows", "before\x00after", "beforeafter"},
+		{"strips other C0 control bytes", "a\x01b\x07c\x1fd", "abcd"},
+		{"preserves tab, newline and carriage return", "a\tb\nc\r\nd", "a\tb\nc\r\nd"},
+		{"removes ANSI escape sequences", "\x1b[31mred\x1b[0m text", "red text"},
+		{"leaves plain text untouched", "plain log line", "plain log line"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := SanitizeForPlainText(tt.input); got != tt.expected {
+				t.Errorf("SanitizeForPlainText(%q) = %q, want %q", tt.input, got, tt.expected)
+			}
+		})
+	}
+}

internal/web/logs.go

@@ -197,7 +197,8 @@ func (h *handler) fetchLogsBetweenDates(w http.ResponseWriter, r *http.Request)
 					}
 				}
 				if plainText {
-					fmt.Fprintf(writer, "%s\n", event.RawMessage)
+					// Strip ANSI and control bytes; a NUL byte truncates clipboard text on Windows
+					fmt.Fprintf(writer, "%s\n", container.SanitizeForPlainText(event.RawMessage))
 				} else if err := encoder.Encode(event); err != nil {
 					log.Error().Err(err).Msg("error encoding log event")
 				}