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How does Claude Code Prompt Cache & Compact Works

This document describes how Claude Code manages Anthropic's prompt cache, performs context compaction (summarization) without losing user task context, and structures its system prompt for maximum cache efficiency.

Big-Picture Architecture

┌──────────────────────────────────────────────────────────────────────────┐
│                         CLAUDE CODE TURN LIFE CYCLE                      │
│                                                                          │

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import re

# Dictionary mapping similar characters include unicode to their normalized form
CHAR_MAPPINGS = {
    # Map variations of 'a' to 'a'
    'a': r"[a4@àáâäãåαаǎăąāạⱥₐᵃᴀꙺꬱ\u0251\u1D41A\u1D44E\u1D482\u1D4B6\u1D4EA\u1D51E\u1D552\u1D586\u1D5BA\u1D5EE\u1D622\u1D656\u1D68A]",
    
    # Map variations of 'b' to 'b'
    'b': r"[b6ƀɓḃḅḇƃȸ\u1D41\u1D45\u1D79\u1D7D\u1D422\u1D456\u1D48A\u1D4BE\u1D4F2\u1D526\u1D55A\u1D58E\u1D5C2]",
    

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Great Tests

• Test on thing
• If that things break,only one test fails
• Repeatable
• Don't rely on run order
• Don't require external resources

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Computer Program Efficiency Optimizing Best Practice.

Why Do?

• High impact, High value if fixed.
• Valid, Required functionality
• We can set reasonable efficiency
• Nothing more important

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/**
 *
 * @param {Object} [constraints={ video: true }] constraints - MediaStreamConstraints
 * @returns {Promise<MediaStream>}
 */
export function getDisplayMedia(constraints = defaultDisplayMediaConstraints) {
  return global.navigator.mediaDevices
    .getDisplayMedia(constraints)
    .then(stream => {
      // support for Chrome's content hint stuff which prefers detail over fluent video.

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[Unit]
Description=coTURN STUN/TURN Server
Documentation=man:coturn(1) man:turnadmin(1) man:turnserver(1)
After=network.target

[Service]
AmbientCapabilities=CAP_NET_BIND_SERVICE
User=turnserver
Group=turnserver
Type=forking

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iOS bitcode not support yet

H264 Hardware Acceleration

Enabled by default for the latest builds of WebRTC

iOS Required

• libresolv.tbd
• AVFoundation.framework
• CoreMedia.framework

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image: docker:latest

variables:
  REPOSITORY_URL: xxx.dkr.ecr.us-west-2.amazonaws.com/xxx
  REGION: us-west-2
  TASK_DEFINTION_NAME: xxx
  CLUSTER_NAME: xxx
  SERVICE_NAME: xxx

services:

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Configuring Linux usage limits with Docker and AWS ECS

• ECS TASK Definitions.

"containerDefinitions": [
    {
...
      "ulimits": [
 {

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Development Phase:

Step 1: Create Certificate .pem from Certificate .p12
Command: openssl pkcs12 -clcerts -nokeys -out apns-dev-cert.pem -in apns-dev-cert.p12

Step 2: Create Key .pem from Key .p12
Command : openssl pkcs12 -nocerts -out apns-dev-key.pem -in apns-dev-key.p12

Step 3: Optional (If you want to remove pass phrase asked in second step)
Command : openssl rsa -in apns-dev-key.pem -out apns-dev-key-noenc.pem