Claude Code Cheat Sheet, October 2026: the complete state of play

My fourth Claude Code cheat sheet in seven months, and the first one I didn't feel like calling an "update". Between June's v2.1.170 and October 9's v2.1.296, Anthropic shipped about 125 versions, including four new models and plugins that can redraw the interface. And the default permission mode changed its very nature. Adding badges to the June edition was no longer enough.

So this time I rebuilt the reference from scratch, from the official documentation downloaded page by page on October 13, and aimed for exhaustiveness in the strict sense: every command, every hook event, every flag, and in an appendix each of the 243 settings.json keys and 391 environment variables. The article that goes with it takes stock of what moved since June, and of what disappeared.

In brief

• What: an exhaustive cheat sheet for Claude Code v2.1.296 (October 9, 2026), as interactive HTML, in English and French, checked against code.claude.com.
• Key figures: ~120 built-in commands and skills, 33 hook events, 46 tools, 243 settings, 391 environment variables.
• Models: Opus 5.5 is the default everywhere ($4 / $20 per MTok, medium effort), plus Sonnet 5.5, Haiku 5.5, and Fable 5.1 as an option for big jobs.
• What changed in nature: auto mode became the default mode, subagents run in the background, and mods let you change Claude Code from the inside.
• Why it matters: you now steer Claude Code by goals and delegate to background agents, instead of approving each command.

The cheat sheet

• English: interactive HTML
• Français : HTML interactif

Same palette as the previous ones (dark background, gold accent), with three badges: NEW for anything that wasn't in the June edition, CHANGED for anything whose behavior changed, REMOVED for anything that no longer exists. The page now renders properly on mobile, which the earlier editions didn't (they forced a fixed 1,400-pixel width).

What's covered

State of play: where Claude Code stands in October 2026

Models: the 5.5 generation settles in

It was a busy summer. Sonnet 5 landed on July 2, Opus 5 on July 24, then the next generation: Fable 5.1 on September 1, Opus 5.5 on the 22nd, Sonnet 5.5 on the 28th, and Haiku 5.5 on October 7. In June I had to annotate the cheat sheet in a hurry after Fable 5 was suspended. The Fable family is back, and the fable alias now points to 5.1.

All of them have a native one-million-token context. Since v2.1.280, Opus is the default model on every plan, Pro and Team Standard included (they used to be on Sonnet). Default effort on the 5.5 models drops to medium, which the documentation recommends for well-scoped everyday work, and it is now saved per model. Finally, ultracode has become an independent toggle (/effort ultracode on) that plans a workflow for each substantive task, at any level.

On the safety side, recent models run with classifiers (cybersecurity, biology). A flagged request automatically switches to a fallback model depending on the category: Opus 4.8 for cyber, Opus 5 for bio. If you work on a security repository and see unexplained switches, switchModelsOnFlag makes Claude Code ask you first.

Auto mode is no longer optional

To me this is the most structural change of the period. In June, auto mode was a feature you turned on. On August 14 it became the default mode for new Pro, Max and Team sessions, and since v2.1.284 (September 28) it is the default for every interactive session on every plan and provider, unless permissions.defaultMode says otherwise.

The idea: a classifier evaluates each action instead of asking you to click. It now runs server-side by default, and its calls no longer count against your usage limits. It was hardened all summer: it blocks git reset --hard or git clean -fd when you didn't ask to throw work away, refuses terraform destroy without an explicit request, forbids access to cloud metadata endpoints, asks before the first read outside the working directory, and now names the rule behind a denial (for example [Data Exfiltration]). The /auto-mode-setup command drafts the autoMode.environment section that describes your trusted repositories and domains.

As a consequence, the old "default" mode is now called Manual, and bypassPermissions can no longer be turned on from a repository's settings. I covered the old model in the Permissions and security article. The rule syntax there still holds; what moved is the starting point.

Parallelism became the norm

In June, agent view had just arrived. Four months later, parallelism is everywhere, and the documentation now lists five distinct ways to get several agents working:

• Subagents run in the background by default since July. They can nest three levels deep, twenty can run at once, and their permission requests surface in the main session. The frontmatter gains omitClaudeMd, autoCompactWindow and effort (see the subagents article for the basics).
• Fork is on by default: a forked subagent inherits the whole conversation and the cache. /subtask starts one, and /fork now copies the entire session into a background session with its own worktree.
• Agent view (claude agents, or ← on an empty prompt) gains search by name, the n: filter, classifier-written titles, and a link to the associated PR or GitLab MR.
• Dynamic workflows orchestrate tens to hundreds of agents from a JavaScript script Claude writes. Saved in .claude/workflows/, they become commands.
• Projects (Pro and Max beta) launch parallel cloud threads from a single conversation.

On top of that comes cross-session messaging (August): two Claude Code sessions on the same machine can write to each other through SendMessage, and @name in the prompt mentions another session.

Extending Claude Code: enter mods

Skills, subagents, hooks, MCP and plugins were already there. On October 1 (v2.1.287) a new layer arrived: mods. A mod is a plugin written in JavaScript or TypeScript that runs inside Claude Code. Where a hook launches an external script, a mod can draw a pane next to the transcript, add a band above the prompt, create a command that runs without a Claude turn, hold a tool call while it asks a question, or send a request to another model. Anthropic uses the mechanism for its own features too: the /diff panel is a mod.

The trade-off is spelled out in the docs: a mod runs with your permissions, reads your secrets, sees every prompt and can approve a tool call on your behalf. I would only install them from a marketplace I control.

Hooks keep growing as well: we're up to 33 events (from 27 in June), including DirectoryAdded, PreModelSwitch and PostModelSwitch. The new onFailure: "block" field (v2.1.295) closes a real gap for anyone relying on hooks as a safeguard: a security hook that crashes or times out now blocks the action instead of letting it through.

Other notable ecosystem additions: claude plugin eval to test a plugin against a run without it, /skill-doctor to spot skills that cost context without being used, syncing of the skills and plugins enabled on claude.ai, and AGENTS.md support when a project has no CLAUDE.md. /import codex, /import gemini and /import cursor bring over another agent's configuration.

Beyond the terminal

Claude Code lives less and less in the terminal alone:

• Desktop comes to Linux in beta (Ubuntu 22.04+, Debian 12+), with a built-in browser, an iOS Simulator, background computer use on macOS, pop-out panes and automatic continuation after a usage limit. /resume there picks up sessions started from the CLI.
• Artifacts publish interactive pages to claude.ai from the session, and can call your MCP connectors on every view.
• Self-hosted environments run cloud sessions on the company's own infrastructure (Team and Enterprise beta).
• Remote Control is out of preview, and the mobile app shows your machines as cards you can start a session on.
• Claude in Chrome has been generally available since July.

Review and security

Four tools now complement each other. /code-review hunts bugs in a background agent, at five effort levels, and can comment on the PR or apply fixes. /simplify handles cleanup. /ultrareview sends a fleet of agents into the cloud. On the security side, the security-guidance plugin reviews each edit, and the Claude Security plugin (July) runs a full multi-agent scan with a threat model, then turns the findings you pick into patches to review. Finally, /verify and /run launch the application to see that a change actually works, beyond the tests.

On the enterprise side

Administrators got a lot of levers: deniedModels and availableModelsMatch: "exact" to block a model until it's approved, maxEffortLevel, allowedProviders, modelPricing to show costs at negotiated rates, managedMcpServers to hand out MCP servers, and the self-hosted Claude apps gateway (SSO, policies, spend limits) in front of Bedrock, Vertex or Foundry. A repository's settings can no longer turn on telemetry, Remote Control or Claude in Chrome: those now belong to the user or the admin.

What disappeared

• Ultraplan (the /ultraplan command and keyword): removed in August.
• /vim and /pr-comments: removed. Vim mode is set in /config.
• The TodoWrite and Task* tools are no longer provided to recent models (CLAUDE_CODE_ENABLE_TODO_TOOLS=1 brings them back), and TaskOutput is gone.
• Glob and Grep are absent by default on macOS, Linux and WSL: Claude uses find and grep, which actually run embedded versions of bfs and ugrep.
• /agents no longer opens a wizard: ask Claude to create the agent, or edit .claude/agents/.

My takeaway

Back in December, in my 20-article series, Claude Code was a terminal assistant you watched command by command. In October, the tool is designed for you to hand it a goal (/goal), let it break the goal down, delegate to background agents, and let a classifier act as the guardrail. The user's job shifts toward defining the frame: rules, hooks, CLAUDE.md, spend limits. That is exactly the idea behind Kaizen, the Claude Code SDLC I presented last week: when the agent speeds everything up, critical rules have to be enforced by code.

The flip side is surface area. 243 settings and 391 environment variables is a lot, and part of this cheat sheet exists so you can find the right lever without rereading 220 documentation pages. /doctor and /skill-doctor go in the right direction by helping you remove what no longer serves.

Official sources: Changelog, What's new, Commands, CLI reference, Hooks reference, Model configuration, Mods overview, All settings, Environment variables.

Previous editions are still available: June EN · FR, April EN · FR, March EN · FR.

If you spot a mistake or something missing, let me know and I'll fix the cheat sheet.