How to Pass Conversation History to Anthropic Claude Reliably in n8n

1// Code node — JavaScript
2// Validate and fix conversation history for Claude
3
4const items = $input.all();
5const rawMessages = items[0].json.memory
6  || items[0].json.messages
7  || items[0].json.chatHistory
8  || [];
9
10const currentMessage = items[0].json.message
11  || items[0].json.text
12  || items[0].json.chatInput
13  || '';
14
15// Step 1: Extract system messages for the system parameter
16const systemMessages = rawMessages
17  .filter(m => m.role === 'system')
18  .map(m => m.content || m.text)
19  .join('\n');
20
21// Step 2: Filter to only user/assistant messages
22let messages = rawMessages
23  .filter(m => m.role === 'user' || m.role === 'assistant' || m.role === 'human' || m.role === 'ai')
24  .map(m => ({
25    role: (m.role === 'human' || m.role === 'user') ? 'user' : 'assistant',
26    content: m.content || m.text || m.message || ''
27  }))
28  .filter(m => m.content.trim() !== '');
29
30// Step 3: Merge consecutive same-role messages
31const merged = [];
32for (const msg of messages) {
33  if (merged.length > 0 && merged[merged.length - 1].role === msg.role) {
34    merged[merged.length - 1].content += '\n' + msg.content;
35  } else {
36    merged.push({ ...msg });
37  }
38}
39
40// Step 4: Ensure first message is from user
41if (merged.length > 0 && merged[0].role !== 'user') {
42  merged.shift(); // Remove leading assistant message
43}
44
45// Step 5: Add current user message
46if (currentMessage.trim()) {
47  if (merged.length > 0 && merged[merged.length - 1].role === 'user') {
48    merged[merged.length - 1].content += '\n' + currentMessage;
49  } else {
50    merged.push({ role: 'user', content: currentMessage });
51  }
52}
53
54return [{
55  json: {
56    messages: merged,
57    system: systemMessages || 'You are a helpful assistant.',
58    messageCount: merged.length,
59    sessionId: items[0].json.sessionId || 'default'
60  }
61}];

1// HTTP Request node body for direct Claude API call
2{
3  "model": "claude-3-5-sonnet-20241022",
4  "max_tokens": 2048,
5  "system": "{{ $json.system }}",
6  "messages": {{ JSON.stringify($json.messages) }}
7}

1// Code node — JavaScript
2// Store the conversation turn in memory
3
4const claudeResponse = $input.first().json;
5const userMessage = $('Format History').first().json.messages.slice(-1)[0]?.content || '';
6const assistantMessage = claudeResponse.content?.[0]?.text || '';
7
8return [{
9  json: {
10    sessionId: $('Format History').first().json.sessionId,
11    userMessage,
12    assistantMessage,
13    // For Postgres node direct insert:
14    role_user: 'user',
15    content_user: userMessage,
16    role_assistant: 'assistant',
17    content_assistant: assistantMessage
18  }
19}];

1// Add to the Format History Code node
2const MAX_MESSAGES = 40;
3const KEEP_RECENT = 10;
4
5if (merged.length > MAX_MESSAGES) {
6  const oldMessages = merged.slice(0, merged.length - KEEP_RECENT);
7  const recentMessages = merged.slice(-KEEP_RECENT);
8
9  // Flag for summarization (handle in a separate branch)
10  return [{
11    json: {
12      needsSummarization: true,
13      oldMessages,
14      recentMessages,
15      system: systemMessages || 'You are a helpful assistant.',
16      sessionId: items[0].json.sessionId || 'default'
17    }
18  }];
19}
20
21// Normal flow continues if under limit