claude-code-sdk

name

claude-code-sdk

description

Claude Code extensibility and configuration reference: plugins, plugin dependencies, hooks, skills, rules, subagents, agent teams, channels, MCP servers, output styles, memory, settings, server-managed settings, sandboxing, auto mode, routines, scheduled tasks, cloud reviews (ultraplan/ultrareview), remote control, web sessions, computer use, model configuration, and Agent SDK (incl. TypeScript V2 preview). Invoke whenever Claude Code itself is the subject — questions, configuration, building extensions, debugging, or understanding internals.

Claude Code SDK

Authoritative reference for Claude Code extensibility and configuration. Use this skill when building, configuring, or debugging any Claude Code extension mechanism.

References

• Skills — [${CLAUDE_SKILL_DIR}/references/skills.md] frontmatter fields, invocation control matrix, paths: shared mechanic with rules, skillOverrides setting, string substitutions, dynamic context injection, subagent execution via fork, compaction budget, description budget (1,536-char per-entry, 1% context aggregate), bundled skills
• Rules — [${CLAUDE_SKILL_DIR}/references/rules.md] .claude/rules/*.md discovery (recursive), two loading modes (unconditional = launch-time priority; conditional via paths:), paths: syntax (comma-string OR YAML list), project vs personal scope, InstructionsLoaded hook with all 5 matchers, sharing patterns, claudeMdExcludes
• Plugins — [${CLAUDE_SKILL_DIR}/references/plugins.md] plugin.json schema (incl. dependencies array v2.1.110+, experimental.monitors v2.1.105+, experimental.themes v2.1.118+), directory layout, ${CLAUDE_PLUGIN_ROOT}/_DATA env vars, marketplace.json (5 source types + allowCrossMarketplaceDependenciesOn), LSP server configs, bin/ PATH contract, claude plugin tag --push and claude plugin prune, allowedChannelPlugins managed setting
• Hooks — [${CLAUDE_SKILL_DIR}/references/hooks.md] all 29 events with input/output JSON schemas and matcher values, 5 hook types (command, http, prompt, agent, mcp_tool) with handler fields, exit code blocking table (incl. PreCompact blocking v2.1.105+), async hooks, decision control patterns, security
• Subagents — [${CLAUDE_SKILL_DIR}/references/subagents.md] 5 built-in agents, custom agent frontmatter, tool control, MCP scoping, worktree isolation, invocation methods, agent teams (architecture, tasks, messaging, hooks, lifecycle)
• MCP — [${CLAUDE_SKILL_DIR}/references/mcp.md] .mcp.json schema, 3 transports (HTTP/SSE/stdio), scopes and precedence, OAuth (incl. headersHelper), env var expansion, managed config, tool search, alwaysLoad (v2.1.121+), 2KB description cap, anthropic/maxResultSizeChars per-tool override, elicitation, resources, prompts as commands
• Memory — [${CLAUDE_SKILL_DIR}/references/memory.md] full .claude directory tree, CLAUDE.md hierarchy and loading order, @import syntax (max depth 5), auto memory (MEMORY.md 200-line/25KB cap), path-specific rules
• Settings — [${CLAUDE_SKILL_DIR}/references/settings.md] 5-level scope hierarchy, server-managed settings (v2.1.30 Enterprise / v2.1.38 Teams), 50+ settings keys, permission rule syntax per tool type, 6 permission modes, sandbox config (filesystem/network isolation), claude project purge (v2.1.126), expanded protected paths
• Auto Mode — [${CLAUDE_SKILL_DIR}/references/auto-mode.md] classifier mechanics (Sonnet 4.6 background, never sees tool results), prompt-injection resistance, default block lists, failure modes (3-consecutive / 20-total circuit breaker), autoMode.{environment,allow,soft_deny} config (v2.1.118+ $defaults sentinel), CLI subcommands, enterprise lockdown
• Cloud — [${CLAUDE_SKILL_DIR}/references/cloud.md] surface comparison (versions, plans, provider restrictions), Routines (v2.1.105+, schedule/API/GitHub triggers, /fire endpoint), Ultraplan (v2.1.91+), Ultrareview (v2.1.86+ with pricing tier), Remote Control (v2.1.51+ vs --teleport), Claude Code on the Web, Code Review, Computer Use (v2.1.85+ macOS-only)
• Model config — [${CLAUDE_SKILL_DIR}/references/model-config.md] aliases (incl. [1m] variants), effort levels (low/medium/high/xhigh/max — available levels depend on the model), opusplan hybrid routing, third-party provider pinning, prompt caching env vars
• Output styles — [${CLAUDE_SKILL_DIR}/references/output-styles.md] 3 built-in styles, custom style frontmatter, keep-coding-instructions flag, system prompt modification pipeline, activation timing (session start only)
• Channels — [${CLAUDE_SKILL_DIR}/references/channels.md] MCP server contract, one-way vs two-way types, sender gating, permission relay, console (API key) auth (v2.1.128+), allowedChannelPlugins allowlist (v2.1.84+), enterprise controls, built-in plugins (Telegram/Discord/iMessage/fakechat)
• Tools — [${CLAUDE_SKILL_DIR}/references/tools.md] built-in tools by category with permission requirements, name patterns for permission rules, agent tool restrictions, hook matchers, skill allowed-tools
• Status line — [${CLAUDE_SKILL_DIR}/references/statusline.md] configuration fields, complete JSON input schema, ANSI colors, OSC 8 clickable links, caching by session_id, plugin delivery
• Agent SDK — [${CLAUDE_SKILL_DIR}/references/agent-sdk.md] entry points (query/ClaudeSDKClient/ unstable_v2_* preview), session-based send/stream patterns, full options reference, sessions (continue/resume/fork), system prompt config, permissions, hooks, custom tools, MCP, subagents, streaming, structured outputs, headless init.plugin_errors schema, Claude Agent SDK v0.1.0 migration, TS↔Python differences
• Best practices — [${CLAUDE_SKILL_DIR}/references/best-practices.md] context window mechanics, verification patterns, scheduling (/loop//proactive alias, cron tools, cloud/desktop), checkpointing and rewind, extension mechanism selection table

Read the relevant reference before making detailed changes. References provide field-level schemas, complete tables, and implementation details.

Concepts

Skill — Prompt template in SKILL.md loaded on-demand when description matches user request. Frontmatter controls invocation, tool access, model, effort (incl. xhigh where the model supports it), execution context (context: fork for subagent), scoped hooks, and paths: glob filter for file-pattern auto-activation. Supports string substitutions ($ARGUMENTS, ${CLAUDE_SKILL_DIR}, ${CLAUDE_EFFORT}) and dynamic context injection via !`command`. Per-skill description cap: 1,536 chars (raised from 250 in v2.1.105). Aggregate description budget: 1% of context window with 8,000-char fallback (override via SLASH_COMMAND_TOOL_CHAR_BUDGET). The skillOverrides setting toggles per-skill visibility/invocability in four states; the /skills menu writes it.

Rule — Modular project context in .claude/rules/*.md (project) or ~/.claude/rules/*.md (personal). Two loading modes: without paths: loads at launch with the same priority as .claude/CLAUDE.md — use to split an overgrown CLAUDE.md into topic files. With paths: is conditional, only injected when working with files matching the glob. Discovery is recursive across subdirectories. paths: accepts a comma-separated string or a YAML list (YAML-list form added in v2.1.84). The InstructionsLoaded hook fires for each rule loaded with matchers session_start, nested_traversal, path_glob_match, include, and compact. Rules are file-triggered; skills are task-triggered. The paths: field is a shared mechanic between rules and skills — same syntax, same semantics, applied to two primitives.

Plugin — Distributable package of skills, agents, hooks, MCP servers, LSP servers, output styles, monitors, themes, and default settings. Manifest at .claude-plugin/plugin.json (only name is required when present). Skills namespaced as /plugin:skill. Two path variables: ${CLAUDE_PLUGIN_ROOT} (install dir, changes on update) and ${CLAUDE_PLUGIN_DATA} (persistent data dir). Marketplace supports 5 source types. bin/ adds executables to Bash PATH (W14 2026). Plugins ship custom color themes via experimental.themes (v2.1.118+) and background monitors via experimental.monitors (v2.1.105+; the top-level monitors key is deprecated as of v2.1.129).

Plugin Dependencies — A plugin can declare other plugins it needs in the dependencies array of plugin.json (v2.1.110+). Entries are bare strings (track latest) or objects {name, version, marketplace} with semver ranges (~, ^, >=, =). Pre-releases excluded unless opted in (^2.0.0-0). Cross-marketplace dependencies are blocked unless the target is listed in allowCrossMarketplaceDependenciesOn in the root marketplace.json. Tag releases with {plugin-name}--v{version} via claude plugin tag --push; remove orphans with claude plugin prune (v2.1.121+). plugin uninstall --prune cascades.

Hook — Deterministic automation at 29 lifecycle events. Five types: command (shell), http (POST to URL), prompt (single-turn LLM, 30s), agent (multi-turn with tools, 60s), mcp_tool (in-process MCP). Matcher patterns filter when hooks fire (exact string, pipe-delimited list, or regex). Exit code 2 blocks the operation for blocking events. PreCompact gained the ability to block as of v2.1.105. PostToolUse hookSpecificOutput.updatedToolOutput replaces tool output for ALL tools (v2.1.121, was MCP-only). All matching hooks run in parallel.

MCP Server — External tool/resource provider via Model Context Protocol. Three transports: HTTP (recommended for remote), SSE (deprecated), stdio (local processes). OAuth 2.0 for remote servers. Scope precedence: local > project > user > plugin > Claude.ai connectors. Tool search defers schema loading for large tool sets; alwaysLoad: true (v2.1.121+) bypasses deferral per server. Tool descriptions and server instructions cap at 2KB (v2.1.84+). Per-tool result-size override via anthropic/maxResultSizeChars (v2.1.91+). Supports elicitation and @server:uri resources.

Output Style — Persona/behavior modifier that replaces parts of the default system prompt — the only mechanism that does this. Built-in: Default, Explanatory, Learning. keep-coding-instructions: false (default) removes coding guidance; true appends style on top of full prompt. Applied at session start only (not mid-conversation) due to prompt caching.

CLAUDE.md / Memory — Project memory providing persistent context. Hierarchy: managed > project > user > local. Loaded by walking up from cwd. Supports @path imports (max depth 5). Auto memory: MEMORY.md (first 200 lines or 25KB) loaded each session; topic files read on demand. claudeMdExcludes skips irrelevant CLAUDE.md in monorepos. Modular content lives in rules (see Rule concept above).

Subagent — Isolated context for delegated tasks. Five built-in types: Explore (haiku, read-only), Plan (inherited model, read-only), general-purpose (inherited model, all tools), statusline-setup (sonnet), Claude Code Guide (haiku). Custom agents in .claude/agents/ with frontmatter for tools, model, MCP scoping. Invocation: automatic delegation, @-mention, --agent flag (session-wide). Subagents cannot spawn other subagents. Supports persistent memory, worktree isolation, scoped MCP servers.

Agent Teams — Multi-agent orchestration with shared task lists and inter-agent messaging. Lead creates team, spawns teammates, coordinates work. Tasks have states (pending/in_progress/completed), dependencies, and ownership. Teammates go idle between turns and wake on message. Team-specific hooks: TeammateIdle, TaskCreated, TaskCompleted. Experimental: requires CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1.

Channels — Push external events into a running session via MCP servers spawned over stdio. One-way (alerts/webhooks) or two-way (chat with reply tools). Sender gating required to prevent prompt injection. Permission relay enables remote tool approval. Console (API key) auth supported as of v2.1.128+; orgs with managed settings must set channelsEnabled: true. Built-in plugins: Telegram, Discord, iMessage, fakechat. allowedChannelPlugins (v2.1.84+) is the enterprise allowlist. Research preview, requires --channels per session.

Auto Mode — Permission mode where a separate classifier model (Sonnet 4.6, background) reviews actions before they run. The auto permission mode IS the classifier. Available v2.1.83+ on Max/Team/Enterprise/API plans (Anthropic API only — not Bedrock/Vertex/Foundry). The classifier never sees tool results, so prompt injection from tool output cannot influence its decisions. Three-consecutive / 20-total denial circuit breaker. Configure trust via autoMode.{environment,allow,soft_deny} with the $defaults sentinel (v2.1.118+). Enterprise lockdown: disableAutoMode, allowManagedDomainsOnly, allowManagedReadPathsOnly, allowManagedHooksOnly.

Routines — Templated cloud agents on Anthropic infrastructure (v2.1.105+). Triggered by schedule (/schedule or /routines CLI), API call (/fire endpoint with one-time bearer token), or GitHub events (Claude GitHub App). Daily run cap with extra-usage fallback; webhook hourly caps in research preview.

Cloud Reviews — Two cloud-based review surfaces. Ultraplan (v2.1.91+) drafts complex plans in a web session for browser review; /ultraplan [prompt] or include ultraplan keyword; auto-creates default cloud env (v2.1.101+); disconnects active Remote Control. Ultrareview (v2.1.86+) runs parallel agents to find and verify bugs in a remote sandbox; /ultrareview (current branch) or /ultrareview <PR#>; pricing tier (Pro/Max 3 free runs through 2026-05-05, then $5–$20 per review extra usage). Neither runs on Bedrock/Vertex/Foundry. Local /review is a separate, simpler multi-agent local review.

Remote Control — Continue a local session from phone/tablet/browser (v2.1.51+). claude remote-control server mode, --remote-control interactive flag, or /remote-control mid-session. Distinct from --teleport (cloud-to-local session move). Org policy can disable; admin gates and "needs auth" vs "failed" status are surfaced explicitly.

Web Sessions — Run Claude Code in the cloud from claude.ai/code. --remote opts a local session into cloud sandbox; sessions move via --teleport. Local-bundle fallback via CCR_FORCE_BUNDLE=1 for repos that fail to upload.

Server-Managed Settings — Enterprise admins ship Claude Code config from the Claude.ai admin console without device management infrastructure (v2.1.30 Enterprise, v2.1.38 Teams). Server-checked first (no merge with endpoint-managed). forceRemoteSettingsRefresh enables fail-closed startup. MCP distribution and per-group config not supported.

Computer Use — macOS-only GUI automation in CLI (v2.1.85+, W14 2026). Opt-in via /mcp computer-use enable. Pro/Max plans only; Claude.ai auth required. Per-app approval with broad-reach warnings; control tiers: view-only, click-only, full. Machine-wide screenshare lock is the dominant failure mode.

Settings — Configuration hierarchy: server-managed > managed > CLI args > local > project > user. Array-valued settings (permissions, sandbox paths) concatenate and deduplicate across scopes — they do not replace. Six permission modes: default, plan, acceptEdits, auto (v2.1.83+), dontAsk, bypassPermissions. Permission evaluation: deny > ask > allow (first match wins). Sandbox provides filesystem and network isolation with allowWrite/denyWrite/allowRead/ denyRead paths.

Agent SDK — Programmatic interface for building custom agents using Claude Code as a library. TypeScript (@anthropic-ai/claude-agent-sdk, package renamed from claude-code-sdk in v0.1.0) and Python (claude-agent-sdk). Entry points: query() and ClaudeSDKClient (V1 stable); unstable_v2_createSession/unstable_v2_resumeSession/ unstable_v2_prompt with separate send/stream and await using lifecycle (V2 preview). Sessions persist via continue/resume/fork. Headless --output-format stream-json returns init.plugin_errors with both dependency demotions (v2.1.111+) and --plugin-dir failures (v2.1.128+). CLAUDE_CODE_FORK_SUBAGENT=1 works in non-interactive claude -p (v2.1.121+).

Choosing the Right Extension Mechanism

When to Use Each

• CLAUDE.md — persistent project context for every session: conventions, build commands, team practices. Loads automatically. Keep under 200 lines; bloated CLAUDE.md causes instruction drift. Instructions are advisory — for guaranteed execution, use hooks.

• Rules — modular project context that you'd otherwise put in CLAUDE.md, with optional file-pattern scoping. Use when CLAUDE.md is getting too large to read in one pass (split into topic files under .claude/rules/), or when context is only relevant when editing a specific subtree (path-scoped rules with paths:). File-triggered, not task-triggered. Don't use for task instructions — that's a skill. Don't use for enforcement — that's a hook.

• Skills — reusable domain expertise or workflows loaded on-demand. Two patterns:

  • Reference content — knowledge applied inline (conventions, patterns). Auto-triggered by description match or paths: glob.
  • Task content — step-by-step actions (deploy, commit). Runs in subagent (context: fork), manual invocation (disable-model-invocation: true).

• Subagents — isolated work with tool restrictions, or when verbose output should stay out of main context. Custom agents get their own system prompt and tool set. Use when isolation, specialization, or context protection matters.

• Agent teams — parallel work across multiple independent agents with task coordination and messaging. Use when work decomposes into independent units benefiting from simultaneous execution.

• Hooks — deterministic automation that must always happen. Formatting after edits, blocking destructive commands, injecting context, enforcing policies. Unlike CLAUDE.md and rules (advisory), hooks are guaranteed to run.

• MCP servers — connecting to external services: databases, APIs, issue trackers. The integration layer for tools and resources from outside the local environment.

• Channels — pushing external events into a running session. For real-time signals from chat platforms, webhooks, CI results, or monitoring alerts. Requires explicit opt-in per session.

• Output styles — changing how Claude communicates (tone, format, persona) without changing capabilities. The only mechanism that replaces parts of the system prompt.

• Plugins — packaging and distributing any combination of the above as a single installable unit. Declare cross-plugin dependencies via the array.

Skill Content Design

• Reference content (conventions, patterns) — context: inline (default), disable-model-invocation: false. Auto or manual trigger. Claude uses it alongside conversation.
• Task content (deploy, generate, commit) — context: fork, disable-model-invocation: true. Manual only. Skill becomes subagent's prompt with no conversation history.

Skill Invocation Control

Frontmatter	User	Claude	Context loading
(default)	Yes	Yes	Description always loaded; full skill when invoked
disable-model-invocation: true	Yes	No	Nothing loaded until user invokes
user-invocable: false	No	Yes	Description always loaded; full skill when invoked

paths: filters auto-invocation only — manual /skill-name always works. Combining paths: with disable-model-invocation: true makes auto-activation impossible (the description leaves context, so the filter has nothing to filter). To get path-scoped auto-only behavior, set user-invocable: false instead.

Subagent Selection

• Read-only exploration — built-in Explore (haiku, accepts thoroughness: quick/medium/very thorough)
• Plan mode research — built-in Plan (inherited model, read-only)
• Complex multi-step task — built-in general-purpose (inherited model, all tools)
• Specialized role — custom agent in .claude/agents/ with own prompt and tool restrictions
• Skill in isolation — skill with context: fork + agent field
• Session-wide mode — claude --agent <name> or agent in settings
• Parallel coordination — agent teams via TeamCreate

Hook Type Selection

• command — deterministic (lint, validate, format). Timeout: 600s. Supports async: true for background.
• http — POST to URL. Non-2xx = non-blocking error. Supports header env var interpolation.
• prompt — LLM judgment on hook input alone. Timeout: 30s. Returns {ok, reason}.
• agent — LLM with file/command access. Timeout: 60s. Same response schema as prompt.
• mcp_tool — in-process MCP tool dispatched as a hook. Use when a hook needs structured tool semantics.

Command hooks are the default. Prompt/agent hooks limited to 8 events.

Settings Scope Selection

• Organization policy (no MDM) — Server-managed (Claude.ai admin console). Cannot be overridden by endpoint settings.
• Organization policy (MDM) — Managed. System paths. Cannot be overridden.
• Personal cross-project — User. ~/.claude/settings.json
• Team-shared — Project. .claude/settings.json
• Personal project-specific — Local. .claude/settings.local.json

Precedence: server-managed > managed > CLI args > local > project > user. Arrays concatenate across scopes.

Quick Reference

Skill Locations

• Server-managed — Claude.ai admin console (organization-wide, no MDM required)
• Enterprise (MDM) — managed settings
• Personal — ~/.claude/skills/<name>/SKILL.md
• Project — .claude/skills/<name>/SKILL.md
• Plugin — <plugin>/skills/<name>/SKILL.md

Plugin Layout

plugin-name/
├── .claude-plugin/
│   └── plugin.json        # Manifest (name required; declares dependencies, monitors, themes)
├── skills/                # Skills as <name>/SKILL.md
├── agents/                # Custom subagents (.md)
├── output-styles/         # Output style files (.md)
├── hooks/
│   └── hooks.json         # Hook config
├── monitors/              # experimental.monitors background monitors (v2.1.105+)
├── themes/                # experimental.themes color themes (v2.1.118+)
├── bin/                   # Executables added to Bash PATH (W14 2026)
├── settings.json          # Default settings (agent key only)
├── .mcp.json              # MCP server definitions
├── .lsp.json              # LSP server configs
└── README.md

.claude Directory

.claude/
├── CLAUDE.md              # Project instructions (or ./CLAUDE.md at repo root)
├── settings.json          # Project settings (shared via VCS)
├── settings.local.json    # Local settings (gitignored)
├── skills/                # Project skills (with optional paths: glob frontmatter)
├── agents/                # Custom subagents
├── rules/                 # Modular rules (*.md, optional paths: frontmatter)
├── hooks.json             # Project hooks (alternative to settings.json hooks)
├── .mcp.json              # Project MCP servers
└── .lsp.json              # Project LSP servers

Hook Events (29)

Can block:

• UserPromptSubmit — before prompt processing. All 5 hook types.
• UserPromptExpansion — when a slash command expands to a prompt. All 5 hook types. Matcher: command_name.
• PreToolUse — before tool executes. All 5 types. Matcher: tool name.
• PostToolBatch — once per resolved parallel batch. All 5 types. No matcher. Stops the agentic loop.
• PreCompact — before compaction (blocking added v2.1.105). Command, http.
• PermissionRequest — permission dialog shown. All 5 types. Matcher: tool name.
• SubagentStop — subagent finishes. All 5 types. Matcher: agent type.
• TaskCreated — task being created (v2.1.84+). All 5 types.
• TaskCompleted — task marked complete. All 5 types.
• Stop — Claude finishes responding. All 5 types.
• TeammateIdle — teammate going idle. Command, http.
• WorktreeCreate — worktree being created (HTTP hookSpecificOutput.worktreePath v2.1.84+). Command, http.
• Elicitation / ElicitationResult — MCP user input. Command, http. Matcher: server name.

Cannot block:

• SessionStart — session begins/resumes. Command, mcp_tool. Matcher: session source.
• Setup — fires on --init-only / -p --init / -p --maintenance. Command, mcp_tool. Matchers: init, maintenance. CLAUDE_ENV_FILE available.
• InstructionsLoaded — CLAUDE.md or rule loaded. Command, mcp_tool. Matchers: session_start, nested_traversal, path_glob_match, include, compact.
• PermissionDenied — permission rejected (incl. auto-mode classifier). Command, http. Matcher: tool name.
• PostToolUse — after tool success. All 5 types. Matcher: tool name. decision: "block" feeds reason to Claude but cannot undo execution. hookSpecificOutput.updatedToolOutput replaces output for ALL tools (v2.1.121+).
• PostToolUseFailure — after tool failure. All 5 types. Matcher: tool name.
• Notification — notification sent. Command, http. Matchers include elicitation_complete, elicitation_response.
• SubagentStart — subagent spawned. Command, http. Matcher: agent type.
• StopFailure — turn ended from API error. Command, http. Matchers include oauth_org_not_allowed.
• ConfigChange — config file changed. Command, http. Can block except policy_settings.
• CwdChanged — working directory changed. Command only.
• FileChanged — watched file changed. Command only. Matcher: literal filenames.
• WorktreeRemove — worktree being removed. Command, http.
• PostCompact — after compaction. Command, http. Matcher: trigger type.
• SessionEnd — session terminates. Command, http. Timeout: 1.5s. Matcher: exit reason.

Permission Modes

• default — asks for each tool lacking an allow rule
• plan — read-only until plan approved, then executes
• acceptEdits — auto-approves file edits, asks for shell commands
• auto — classifier model auto-approves safe actions; blocks scope escalation, untrusted infrastructure, hostile content. Requires v2.1.83+; Max/Team/Enterprise/API only; Anthropic API only. --enable-auto-mode flag was removed in v2.1.111.
• dontAsk — auto-denies permission prompts (explicitly allowed tools still work)
• bypassPermissions — skips all checks (requires managed setting or --dangerously-skip-permissions). v2.1.126 expanded the bypass to .claude/, .git/, .vscode/, .idea/, .husky/, shell config files. Catastrophic-removal circuit breaker (rm -rf /, rm -rf ~) still prompts.

Memory Hierarchy

• Managed policy — OS system paths. Organization-wide. Cannot be excluded.
• Project — ./CLAUDE.md or ./.claude/CLAUDE.md. Shared via VCS.
• User — ~/.claude/CLAUDE.md. Personal, all projects.
• Local — ./CLAUDE.local.md. Personal, current project.
• Rules — .claude/rules/*.md (project) and ~/.claude/rules/*.md (personal). Optional paths: frontmatter for file-scoped loading. Without paths: — same priority as project CLAUDE.md.
• Auto memory — ~/.claude/projects/<project>/memory/MEMORY.md. First 200 lines or 25KB loaded per session. Topic files read on demand.

Model Aliases

• opus — latest Opus (Opus 4.7 as of W16 2026)
• sonnet — latest Sonnet (currently Sonnet 4.6)
• haiku — fast model for simple tasks
• opus[1m] / sonnet[1m] — 1M token context window variants
• opusplan — Opus for plan mode, Sonnet for execution
• best — most capable model (currently = opus)
• default — clears override, uses account default

Effort levels: low, medium, high, xhigh, max. Available levels depend on the model. Set via /effort, --effort, or effortLevel setting; per-skill effort: overrides session.

Slash Commands

/loop (also /proactive alias as of v2.1.105), /schedule, /routines, /ultraplan, /ultrareview, /team-onboarding, /autofix-pr, /usage, /branch, /skills, /permissions, /effort, /remote-control.

Related Skills

• prompt-engineering — instruction design techniques for any AI artifact
• skill-engineering — SKILL.md design, description formulas, content architecture
• subagent-engineering — agent prompt design, tool scoping, team coordination
• output-style-engineering — persona definition, tone examples, behavioral rules