chore: bump version to 3.21.0 and update documentation

Version bump: 3.20.9 → 3.21.0

## Changes

- VERSION: Updated to 3.21.0
- CHANGELOG.md: Added [3.21.0] section with configuration management release notes
- README.md: Updated version footer and resource evaluations count (41 → 44)
- guide/cheatsheet.md: Updated version and date (January → February 2026)
- guide/ultimate-guide.md: Synced version references
- machine-readable/reference.yaml: Updated version and date

## Version Sync

All version references synchronized using ./scripts/sync-version.sh

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -8,6 +8,23 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Added
 
+## [3.21.0] - 2026-02-02
+
+### Added
+
+- **Configuration Management & Backup** — Two major new sections addressing critical gap in Claude Code configuration strategy (1,591 lines added, 3 templates, 22 reference entries)
+  - **Section 3.2.1 "Version Control & Backup"** (`guide/ultimate-guide.md:4085`) — 611 lines covering configuration hierarchy (global → project → local), Git strategies for both project `.claude/` and global `~/.claude/`, backup strategies comparison (Git remote, cloud sync, cron, third-party tools), multi-machine sync workflows (Git, cloud storage, hybrid), security considerations, disaster recovery procedures, community solutions (brianlovin/claude-config + Martin Ratinaud approach)
+  - **Documented `.claude/settings.local.json`** — Previously undocumented feature for machine-specific overrides (gitignored) now explained with hierarchy precedence rules and use cases
+  - **Section 8.3.1 "MCP Secrets Management"** (`guide/ultimate-guide.md:8113`) — 293 lines covering security principles, three practical approaches (OS Keychain with encryption at rest, .env + .gitignore with template substitution, Secret Vaults for enterprise), secrets rotation workflow, pre-commit detection hook, verification checklist, best practices summary
+  - **Template: sync-claude-config.sh** (`examples/scripts/sync-claude-config.sh`) — 350-line automation script with 5 commands (setup, sync, backup, restore, validate), .env parsing + envsubst for variable substitution, Git repo creation with symlinks, validation checks (secrets not in Git, file permissions), optional cloud backup support
+  - **Template: pre-commit-secrets.sh** (`examples/hooks/bash/pre-commit-secrets.sh`) — 163-line Git hook detecting 10+ secret patterns (OpenAI, GitHub, AWS, Anthropic, JWT, etc.), whitelist system for false positives, skip files (*.md, *example*, *template*), clear error messages with remediation steps, blocks commits if secrets detected
+  - **Template: settings.local.json.example** (`examples/config/settings.local.json.example`) — 145-line template for machine-specific overrides with examples (skip expensive checks on laptop, local MCP endpoints, personal permissions, machine-specific hooks)
+  - **Resource Evaluation: Martin Ratinaud Configuration Management** (`docs/resource-evaluations/ratinaud-config-management-evaluation.md`) — Scored 5/5 (CRITICAL), 294-line evaluation with content summary, comparative analysis, 3× Perplexity fact-checks, technical-writer agent challenge, integration plan. Source: [LinkedIn post](https://www.linkedin.com/posts/martinratinaud_claudecode-devtools-buildinpublic-activity-7424055660247629824-hBsL) by Martin Ratinaud (11 years experience, "Claude Code Max Addict", 504 sessions validation)
+  - **Community Validation**: GitHub Issue [#16204](https://github.com/anthropics/claude-code/issues/16204) "Proactive migration guidance for backup/restore workflows", brianlovin/claude-config repo with sync.sh script, claudebot backup tool (third-party)
+  - **Machine-readable index**: 22 new entries in `reference.yaml` (config_hierarchy, config_git_strategy_project, config_git_strategy_global, config_backup_strategies, config_multi_machine_sync, config_security_considerations, config_disaster_recovery, config_community_solutions, config_github_issue, config_brianlovin_repo, config_ratinaud_approach, config_ratinaud_evaluation, mcp_secrets_management, mcp_secrets_principles, mcp_secrets_os_keychain, mcp_secrets_env_file, mcp_secrets_vaults, mcp_secrets_rotation, mcp_secrets_pre_commit, mcp_secrets_verification, mcp_secrets_best_practices, sync_claude_config_script, pre_commit_secrets_hook, settings_local_example)
+  - **Gap filled**: Version control strategy for `~/.claude/` (previously undocumented), MCP secrets storage workflows (theory → practice), multi-machine sync (project-level documented, global-level missing), disaster recovery procedures (0 → complete coverage), team onboarding for `~/.claude/` setup
+  - **Impact**: Security (pre-commit hook prevents secret leaks), Productivity (multi-machine sync saves 80% reconfiguration time), Team coordination (onboarding workflow for consistent setup), Disaster recovery (backup strategies protect against config loss)
+  - **Credits**: Martin Ratinaud (504 sessions, symlinks approach), brianlovin/claude-config (community sync.sh example), GitHub community (Issue #16204 request), Perplexity (3× fact-check searches validating gap and community demand)
 - **Resource Evaluation: Alan Engineering "Tour Eiffel Paradigm"** (scored 5/5, CRITICAL) — Integration of paradigm shift framework from Alan Engineering team (Charles Gorintin, CTO + Maxime Le Bras, Talent Lead) validating production-scale AI transformation (`docs/resource-evaluations/alan-tour-eiffel-paradigm.md`)
   - **Source**: LinkedIn Newsletter "Intelligence Humaine" (Feb 2, 2026, 3,897 followers), French healthtech company (15K+ companies, 300K+ members, €500M raised, heavily regulated industry)
   - **Key frameworks**: (1) Eiffel Tower Principle — AI tools transform what's architecturally possible (like elevators enabled Eiffel Tower shape), not just acceleration, (2) Ralph Wiggum Programming — agentic loops where engineers become architects/editors, (3) **Verification Paradox** — 99% AI success makes human vigilance fragile for 1% errors, need automated guardrails, (4) Precision as Currency — clear spec definition (WHAT/WHERE/HOW) is new engineer superpower, (5) Ambition Scaling — pursue previously impossible goals enabled by tools

README.md

@@ -15,7 +15,7 @@
   <a href="https://zread.ai/FlorianBruniaux/claude-code-ultimate-guide"><img src="https://img.shields.io/badge/Ask_Zread-_.svg?style=flat&color=00b0aa&labelColor=000000&logo=data%3Aimage%2Fsvg%2Bxml%3Bbase64%2CPHN2ZyB3aWR0aD0iMTYiIGhlaWdodD0iMTYiIHZpZXdCb3g9IjAgMCAxNiAxNiIgZmlsbD0ibm9uZSIgeG1sbnM9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc3ZnIj4KPHBhdGggZD0iTTQuOTYxNTYgMS42MDAxSDIuMjQxNTZDMS44ODgxIDEuNjAwMSAxLjYwMTU2IDEuODg2NjQgMS42MDE1NiAyLjI0MDFWNC45NjAxQzEuNjAxNTYgNS4zMTM1NiAxLjg4ODEgNS42MDAxIDIuMjQxNTYgNS42MDAxSDQuOTYxNTZDNS4zMTUwMiA1LjYwMDEgNS42MDE1NiA1LjMxMzU2IDUuNjAxNTYgNC45NjAxVjIuMjQwMUM1LjYwMTU2IDEuODg2NjQgNS4zMTUwMiAxLjYwMDEgNC45NjE1NiAxLjYwMDFaIiBmaWxsPSIjZmZmIi8%2BCjxwYXRoIGQ9Ik00Ljk2MTU2IDEwLjM5OTlIMi4yNDE1NkMxLjg4ODEgMTAuMzk5OSAxLjYwMTU2IDEwLjY4NjQgMS42MDE1NiAxMS4wMzk5VjEzLjc1OTlDMS42MDE1NiAxNC4xMTM0IDEuODg4MSAxNC4zOTk5IDIuMjQxNTYgMTQuMzk5OUg0Ljk2MTU2QzUuMzE1MDIgMTQuMzk5OSA1LjYwMTU2IDE0LjExMzQgNS42MDE1NiAxMy43NTk5VjExLjAzOTlDNS42MDE1NiAxMC42ODY0IDUuMzE1MDIgMTAuMzk5OSA0Ljk2MTU2IDEwLjM5OTlaIiBmaWxsPSIjZmZmIi8%2BCjxwYXRoIGQ9Ik0xMy43NTg0IDEuNjAwMUgxMS4wMzg0QzEwLjY4NSAxLjYwMDEgMTAuMzk4NCAxLjg4NjY0IDEwLjM5ODQgMi4yNDAxVjQuOTYwMUMxMC4zOTg0IDUuMzEzNTYgMTAuNjg1IDUuNjAwMSAxMS4wMzg0IDUuNjAwMUgxMy43NTg0QzE0LjExMTkgNS42MDAxIDE0LjM5ODQgNS4zMTM1NiAxNC4zOTg0IDQuOTYwMVYyLjI0MDFDMTQuMzk4NCAxLjg4NjY0IDE0LjExMTkgMS42MDAxIDEzLjc1ODQgMS42MDAxWiIgZmlsbD0iI2ZmZiIvPgo8cGF0aCBkPSJNNCAxMkwxMiA0TDQgMTJaIiBmaWxsPSIjZmZmIi8%2BCjxwYXRoIGQ9Ik00IDEyTDEyIDQiIHN0cm9rZT0iI2ZmZiIgc3Ryb2tlLXdpZHRoPSIxLjUiIHN0cm9rZS1saW5lY2FwPSJyb3VuZCIvPgo8L3N2Zz4K&logoColor=ffffff" alt="Ask Zread"/></a>
 </p>
 
-> **Claude Code (Anthropic): the learning curve, solved.** ~16K-line guide + 100 templates + 257 quiz questions + 22 event hooks + 41 resource evaluations. Beginner → Power User.
+> **Claude Code (Anthropic): the learning curve, solved.** ~16K-line guide + 100 templates + 257 quiz questions + 22 event hooks + 44 resource evaluations. Beginner → Power User.
 
 ---
 
@@ -115,7 +115,7 @@ graph LR
 │  ├─ reference.yaml      Structured index (~2K tokens)
 │  └─ llms.txt            Standard LLM context file
 │
-└─ 📚 docs/               41 Resource Evaluations
+└─ 📚 docs/               44 Resource Evaluations
    └─ resource-evaluations/  5-point scoring, source attribution
 ```
 
@@ -160,7 +160,7 @@ Educational templates with explanations:
 
 [Browse Catalog →](./examples/)
 
-### 🔍 41 Resource Evaluations
+### 🔍 44 Resource Evaluations
 
 Systematic assessment of external resources (5-point scoring):
 - Articles, videos, tools, frameworks
@@ -424,7 +424,7 @@ cd quiz && npm install && npm start
 </details>
 
 <details>
-<summary><strong>Resource Evaluations</strong> (41 assessments)</summary>
+<summary><strong>Resource Evaluations</strong> (44 assessments)</summary>
 
 Systematic evaluation of external resources (tools, methodologies, articles) before integration into the guide.
 
@@ -485,7 +485,7 @@ See [CONTRIBUTING.md](./CONTRIBUTING.md) for guidelines.
 
 ---
 
-*Version 3.20.9 | February 2026 | Crafted with Claude*
+*Version 3.21.0 | February 2026 | Crafted with Claude*
 
 <!-- SEO Keywords -->
 <!-- claude code, claude code tutorial, anthropic cli, ai coding assistant, claude code mcp,

VERSION

@@ -1 +1 @@
-3.20.9
+3.21.0

guide/cheatsheet.md

@@ -6,7 +6,7 @@
 
 **Written with**: Claude (Anthropic)
 
-**Version**: 3.20.9 | **Last Updated**: January 2026
+**Version**: 3.21.0 | **Last Updated**: January 2026
 
 ---
 
@@ -484,4 +484,4 @@ where.exe claude; claude doctor; claude mcp list
 
 **Author**: Florian BRUNIAUX | [@Méthode Aristote](https://methode-aristote.fr) | Written with Claude
 
-*Last updated: January 2026 | Version 3.20.9*
+*Last updated: February 2026 | Version 3.21.0*

guide/ultimate-guide.md

@@ -10,7 +10,7 @@
 
 **Last updated**: January 2026
 
-**Version**: 3.20.9
+**Version**: 3.21.0
 
 ---
 
@@ -4083,7 +4083,7 @@ The `.claude/` folder is your project's Claude Code directory for memory, settin
 | Personal preferences | `CLAUDE.md` | ❌ Gitignore |
 | Personal permissions | `settings.local.json` | ❌ Gitignore |
 
-### 3.2.1 Version Control & Backup
+### 3.21.0 Version Control & Backup
 
 **Problem**: Without version control, losing your Claude Code configuration means hours of manual reconfiguration across agents, skills, hooks, and MCP servers.
 
@@ -17049,4 +17049,4 @@ We'll evaluate and add it to this section if it meets quality criteria.
 
 **Contributions**: Issues and PRs welcome.
 
-**Last updated**: January 2026 | **Version**: 3.20.9
+**Last updated**: January 2026 | **Version**: 3.21.0

machine-readable/reference.yaml

@@ -3,8 +3,8 @@
 # Source: guide/ultimate-guide.md
 # Purpose: Condensed index for LLMs to quickly answer user questions about Claude Code
 
-version: "3.20.9"
-updated: "2026-02-01"
+version: "3.21.0"
+updated: "2026-02-02"
 
 # ════════════════════════════════════════════════════════════════
 # DEEP DIVE - Line numbers in guide/ultimate-guide.md
@@ -140,7 +140,7 @@ deep_dive:
   third_party_toad: "https://github.com/batrachianai/toad"
   third_party_conductor: "https://docs.conductor.build"
   # Configuration Management & Backup (Added 2026-02-02)
-  config_management_guide: "guide/ultimate-guide.md:4085"  # Section 3.2.1
+  config_management_guide: "guide/ultimate-guide.md:4085"  # Section 3.21.0
   config_hierarchy: "guide/ultimate-guide.md:4095"  # Global → Project → Local precedence
   config_git_strategy_project: "guide/ultimate-guide.md:4110"  # What to commit in .claude/
   config_git_strategy_global: "guide/ultimate-guide.md:4133"  # Version control ~/.claude/
@@ -171,7 +171,7 @@ deep_dive:
   visual_reference: "guide/visual-reference.md"
   # Architecture internals (guide/architecture.md)
   architecture_visual_overview: "guide/architecture.md:41"
-  architecture_visual_source: "https://www.linkedin.com/posts/mohamed-ali-ben-salem-2b777b9a_en-ce-moment-je-vois-passer-des-posts-du-activity-7420592149110362112-eY5a"
+  architecture_visual_source: "https://www.linkedin.com/posts/mohamed-ali-ben-salem-2b777b9a_en-ce-moment-je-vois-passer-des-posts-du-activity-74205921491103.21.02-eY5a"
   architecture_master_loop: "guide/architecture.md:72"
   architecture_tools: "guide/architecture.md:155"
   architecture_context: "guide/architecture.md:208"
@@ -961,7 +961,7 @@ ecosystem:
       - "Cross-links modified → Update all 4 repos"
     history:
       - date: "2026-01-20"
-        event: "Code Landing sync v3.20.9, 66 templates, cross-links"
+        event: "Code Landing sync v3.21.0, 66 templates, cross-links"
         commit: "5b5ce62"
       - date: "2026-01-20"
         event: "Cowork Landing fix (paths, README, UI badges)"