How to Handle Escaped JSON from Cohere Output in n8n

1const raw = $json.text || $json.output || $json.message?.content || '';
2
3// Diagnostic output
4return [{
5  json: {
6    raw_type: typeof raw,
7    raw_length: raw.length,
8    first_chars: raw.substring(0, 300),
9    has_double_backslash: raw.includes('\\\\'),
10    has_escaped_quotes: raw.includes('\\"'),
11    has_literal_backslash_n: raw.includes('\\n'),
12    starts_with_quote: raw.startsWith('"'),
13    raw_output: raw
14  }
15}];

1const raw = $json.text || $json.output || $json.message?.content || '';
2
3function unescapeAndParse(text) {
4  let str = text.trim();
5
6  // If the entire output is wrapped in outer quotes, remove them
7  if (str.startsWith('"') && str.endsWith('"')) {
8    try {
9      str = JSON.parse(str); // This unescapes one level
10    } catch (e) {
11      str = str.slice(1, -1);
12    }
13  }
14
15  // Attempt 1: Direct parse
16  try {
17    return JSON.parse(str);
18  } catch (e) {}
19
20  // Attempt 2: Unescape double-escaped characters
21  let unescaped = str
22    .replace(/\\\\/g, '\\')        // \\\\ → \\
23    .replace(/\\"/g, '"')          // \\" → "
24    .replace(/\\n/g, '\n')         // \\n → newline
25    .replace(/\\t/g, '\t')         // \\t → tab
26    .replace(/\\r/g, '\r');        // \\r → return
27
28  try {
29    return JSON.parse(unescaped);
30  } catch (e) {}
31
32  // Attempt 3: Strip markdown fences then retry
33  const fenceMatch = str.match(/```(?:json)?\s*\n?([\s\S]*?)\n?\s*```/);
34  if (fenceMatch) {
35    try {
36      return JSON.parse(fenceMatch[1].trim());
37    } catch (e) {}
38  }
39
40  // Attempt 4: Extract JSON object from surrounding text
41  const jsonMatch = str.match(/\{[\s\S]*\}/);
42  if (jsonMatch) {
43    try {
44      return JSON.parse(jsonMatch[0]);
45    } catch (e) {}
46  }
47
48  return null;
49}
50
51const parsed = unescapeAndParse(raw);
52
53if (parsed) {
54  return [{ json: { data: parsed, parse_status: 'success' } }];
55}
56
57return [{ json: { raw_text: raw, parse_status: 'failed' } }];

1// Cohere preamble (system prompt) for clean JSON output:
2const preamble = `You are a data extraction API.
3
4RULES:
51. Return ONLY a single JSON object
62. Do not escape characters unnecessarily
73. Use standard double quotes for JSON keys and string values
84. Do not wrap the JSON in markdown code fences
95. Do not add explanatory text before or after
106. Do not double-escape special characters
117. Newlines in string values should be \\n (single escape)
12
13The response MUST start with { and end with }
14
15Output schema:
16{"field1": "string", "field2": number, "items": ["array of strings"]}`;

1// When using HTTP Request node to call Cohere Chat API directly:
2// The response structure is:
3// {
4//   "response_id": "...",
5//   "text": "<your JSON output here>",
6//   "generation_id": "...",
7//   "chat_history": [...],
8//   "finish_reason": "COMPLETE",
9//   "meta": { "api_version": {...}, "billed_units": {...} }
10// }
11
12// Extract the text field which contains your actual LLM output
13const cohereResponse = $json;
14const llmOutput = cohereResponse.text || '';
15
16// Now unescape and parse as shown in previous steps
17let cleaned = llmOutput.trim();
18if (cleaned.startsWith('"') && cleaned.endsWith('"')) {
19  try { cleaned = JSON.parse(cleaned); } catch(e) { cleaned = cleaned.slice(1,-1); }
20}
21
22try {
23  const data = JSON.parse(cleaned);
24  return [{ json: { data, cohere_meta: cohereResponse.meta } }];
25} catch (e) {
26  return [{ json: { raw: llmOutput, parse_error: e.message } }];
27}