Anthropic Data Handling

Overview

Handle data responsibly when building with Claude — manage the 200K token context window efficiently, implement conversation trimming strategies, redact PII before sending to the API, and configure data retention settings.

Context Window Management

Claude models have a 200K token context window. Managing it efficiently is critical.

// Count tokens before sending
const count = await client.messages.countTokens({
  model: 'claude-sonnet-4-20250514',
  messages,
  system: systemPrompt,
});

// Budget: 200K total - max_tokens (output) = available input
const MAX_CONTEXT = 200_000;
const MAX_OUTPUT = 4096;
const inputBudget = MAX_CONTEXT - MAX_OUTPUT;

if (count.input_tokens > inputBudget) {
  // Trim oldest messages, keep system prompt + recent context
  messages = trimToFit(messages, inputBudget);
}

Instructions

Step 1: Conversation Trimming

function trimConversation(messages: MessageParam[], maxTokens: number): MessageParam[] {
  // Always keep the first message (often contains key context)
  // Keep the most recent messages
  // Drop middle turns first
  if (messages.length <= 4) return messages;

  const first = messages[0];
  const recent = messages.slice(-6); // Last 3 turns
  return [first, ...recent];
}

PII Handling

// Strip PII before sending to Claude (if not needed for the task)
function redactPII(text: string): string {
  return text
    .replace(/\b[\w._%+-]+@[\w.-]+\.\w{2,}\b/g, '[EMAIL]')
    .replace(/\b\d{3}[-.]?\d{3}[-.]?\d{4}\b/g, '[PHONE]')
    .replace(/\b\d{3}-\d{2}-\d{4}\b/g, '[SSN]')
    .replace(/\b\d{4}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b/g, '[CARD]');
}

Data Retention

• Default: Anthropic does not use API data for training
• Zero retention: Available on Enterprise plans
• Your responsibility: Don't store Claude responses containing user PII longer than needed

Output