Claude Code

Claude Code is Anthropic's coding agent for exploring and editing codebases with long-context reasoning.

It started as a terminal-first workflow and now also reaches IDE, desktop, and web surfaces while remaining strongest for agentic coding loops.

Week of 2026-08-17: /design (research preview) drafts editable UI artboards before implementation; Remote Control is generally available for starting a machine-local session from the Claude app.

v2.1.251 (2026-08-28): seat-based Enterprise subscriptions default to Opus 5, matching other premium plans; PreModelSwitch and PostModelSwitch hooks can block, confirm, or annotate a model switch.

v2.1.259 (2026-09-02): managedMcpServers lets organizations push HTTP/SSE MCP servers to every user (command entries skipped). allowedMcpServers now filters only user-added servers; use deniedMcpServers to block managed entries.

2026-09-17: Projects (beta) turn a Claude Code project into a coordinator conversation that delegates to parallel cloud threads (each a session on its own branch), with shared memory and a project library. Rolling out first to select Pro/Max cloud-session users; local/network threads are not yet available.

From v2.1.284 (2026-09-28), the sonnet alias resolves to Claude Sonnet 5.5 on the Claude API. The default model stays Opus 5.5; switch with /model sonnet. Default effort in Claude Code is medium.

2026-10-01: mods (v2.1.287+) are TypeScript functions shipped inside plugins that can rewrite prompts, observe or answer tool calls, add UI, or replace built-in features such as /diff, in the CLI and desktop app. Mods are not sandboxed and run with Claude Code’s own access; `claude plugin validate` lists what a mod hooks, and admins govern mods through plugin marketplace policy and managed settings.

v2.1.292 (2026-10-06): local stdio MCP servers now negotiate MCP protocol version 2026-07-28 by default. Set `MCP_PROTOCOL_NEGOTIATION=legacy` to keep the older negotiation if a server breaks.

v2.1.293 (2026-10-07): Claude Haiku 5.5 (claude-haiku-5-5) is the default Haiku model on the Anthropic API.

v2.1.295 (2026-10-08): command and HTTP hooks accept `onFailure: "block"`, so a hook that cannot start, times out, or exits with an unexpected code blocks the action instead of letting it through. Claude apps gateway upstreams gain an optional `models` allow-list and time-to-first-byte timeouts, and remote MCP servers reconnect with backoff after outages.

v2.1.296 (2026-10-09): subagent frontmatter accepts `autoCompactWindow`, `CLAUDE_CODE_WORKFLOW_SUBAGENT_MODEL` sets the model for workflow subagents, and the MCP tool-description limit rises from 2,048 to 4,096 characters. /cost and SDK cost figures now price Sonnet 5.5 cache reads at $0.10 per 1M tokens.