unexpected end of file while scanning a string, maybe an unc

Error message

unexpected end of file while scanning a string, maybe an unclosed quote?

What it means

Panic in lexer.scanQuotedString when EOF arrives before the closing quote of a quoted token (the delimiter rune never reappeared). Escaped delimiters (\" inside "...") are handled, so this means a genuinely unterminated string literal in the nginx config.

Source

Thrown at agent/utils/nginx/parser/lexer.go:175

}

func (s *lexer) skipWhitespace() {
	s.readWhile(isSpace)
}

func (s *lexer) scanComment() flag.Flag {
	return s.NewToken(flag.Comment).Lit(s.readUntil(isEndOfLine))
}

func (s *lexer) scanQuotedString(delimiter rune) flag.Flag {
	var buf bytes.Buffer
	tok := s.NewToken(flag.QuotedString)
	_, _ = buf.WriteRune(s.read())
	for {
		ch := s.read()

		if ch == rune(flag.EOF) {
			panic("unexpected end of file while scanning a string, maybe an unclosed quote?")
		}

		if ch == '\\' && (s.peek() == delimiter) {
			buf.WriteRune(ch)
			buf.WriteRune(s.read())
			continue
		}

		_, _ = buf.WriteRune(ch)
		if ch == delimiter {
			break
		}
	}

	return tok.Lit(buf.String())
}

func (s *lexer) scanKeyword() flag.Flag {

View on GitHub (pinned to 5ac7c80881)

Solutions

Locate the last edited quoted value (grep -n '"' file and check odd counts) and close the literal
Escape embedded quotes as \" rather than leaving them bare
Run nginx -t before reloading so syntax errors surface outside the agent's parser

Example fix

# before
proxy_set_header X-Long "shortened;
# after
proxy_set_header X-Long "shortened";

Defensive patterns

Strategy: validation

Validate before calling

python3 - <<'PY'
import sys, re
for i, line in enumerate(open(sys.argv[1]), 1):
    for q in ('"', "'"):
        if len(re.findall(q, line)) % 2 == 1:
            print(f'odd {q!r} count on line {i}: {line.rstrip()}')
PY <config-file>

Prevention

Keep quotes paired on a single line in nginx configs; escape \" inside values
nginx -t before reload; it reports unterminated strings with line numbers

When it happens

Trigger: Parsing a config with a directive like proxy_set_header X-Foo "bar; or return 301 'target; — the opening " or ' is never closed before end of file.

Common situations: Hand-editing a regex or header value and dropping the closing quote; a generated config where a variable expanded to text containing a quote; copy-paste truncation.

Related errors

AI-assisted analysis of 1Panel-dev/1Panel@5ac7c80881 (2026-08-15). Data as JSON: /api/errors/4f416f228a9ac329. Report an issue: GitHub.