What Claude Code Is
The agentic CLI/IDE tool explained — the session loop, install, and where everything lives.
CLAUDE.md & Memory Files
The highest-leverage Claude Code customization: persistent project memory.
AGENTS.md & Cross-Tool Interop
The open standard every coding agent reads — and how to keep it in sync with your CLAUDE.md.
Plan Mode
Read-only investigate-and-propose before any edits run — the safest way to tackle big changes.
IDE Integrations
VS Code and JetBrains extensions, inline diffs, and shared settings.
settings.json: The Config System
File tiers and precedence, key sections, and project vs personal config.
Permissions & Permission Modes
allow/ask/deny rules and modes — cut prompts without losing safety.
Custom Slash Commands
Turn a repeatable workflow into one word.
Output Styles
Change Claude Code's tone, verbosity, and teaching behaviour.
Statusline Customization
Surface model, cwd, context budget and git state with a custom script.
Spec-Driven Development with Spec Kit
Stop vibe-coding big features. Make an executable spec the source of truth, then have Claude Code build from it — with GitHub's Spec Kit.
Context Management
/compact vs /clear, auto-compaction, and staying effective as sessions grow.
Checkpoints & Rewind
Undo Claude's edits, roll back a whole session, and compress context with /rewind — the safety net for ambitious runs.
Hooks: Deterministic Automation
Run commands at lifecycle events to enforce formatting, gates, and safety.
Skills: On-Demand Expertise
SKILL.md, progressive disclosure, and Skill vs command vs subagent vs MCP.
Subagents & Parallel Agents
Delegate to isolated-context agents with scoped tools — and when not to.
Subagent Fleet Limits: Concurrency Caps & Nested Depth
On July 21, 2026 Claude Code capped concurrent subagents at 20 and killed nested spawning. Three days later nesting came back at depth 3. Here are the four env vars, the error you'll hit, why the caps exist, and how to design fleets that survive them.
Dynamic Workflows & ultracode
Orchestrate tens to hundreds of subagents from a script Claude writes — for codebase audits, large migrations, and cross-checked research.
Inter-Session Messaging
Make two Claude Code terminals talk without you copy-pasting — the three shipping patterns for peer-to-peer session messaging, and the trust boundary you must not skip.
MCP Servers in Claude Code
Connect databases, GitHub, browsers and more via the Model Context Protocol.
Background Tasks, /loop & Scheduling
Long-running commands, recurring loops, and scheduled cloud agents.
Auto-Commit Background Agents: Draft-PR Handoff
On July 1, 2026 Claude Code v2.1.198 let background agents commit, push, and open a draft PR on their own. Five weeks later v2.1.221 tuned the default. Here is what the flow actually does, the notification hook it fires, why the community wanted an off switch, and the propose-only pattern that still works.
Plugins & Marketplaces
Bundle skills, agents, commands, hooks and MCP into one installable unit.
Git Worktrees & Parallel Workstreams
Run multiple isolated Claude sessions on one repo without them colliding.
Headless Mode & the Agent SDK
Run Claude Code in CI, and build production agents on the same harness.
Self-Hosted Environments: run cloud sessions on your own boxes
Practitioner guide to the claude self-hosted-runner beta (shipped Aug 7, 2026 in v2.1.224). Run Claude Code web, mobile and desktop cloud sessions on infrastructure you control — egress-only, no inbound holes, one-user-at-a-time isolation. Architecture, quickstart, runner lifecycle, git creds, autoscaling, and the six gotchas that catch every first fleet.
The MCP Token Tax
Why connecting MCP servers can burn 50k–150k tokens before your first request — and the three fixes: Tool Search, code execution, and knowing when a CLI call wins.
Accessibility
Screen reader mode, vim ergonomics, mouse and scroll controls, and high-contrast themes in Claude Code.
Troubleshooting Claude Code
Symptom-to-fix for hangs, high memory, broken search, compaction thrashing, and garbled terminals.