Finds the first syntax error with line, column and a caret, then repairs the document with a tolerant parser that records every change: comments, trailing or missing commas, single or smart quotes, unquoted keys, = instead of :, NaN/Infinity/undefined, Python True/False/None, hex and malformed numbers, raw line breaks in strings, unterminated strings and containers, and several concatenated documents (wrapped in an array). The repaired JSON is pretty-printed; the report lists the error, each fix with its position and, optionally, the values at a JSONPath. The preview highlights the error line and every repaired line. Everything runs locally.