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Claude Code v2.1.257

Released · Anthropic

Changes MCP server config, settings files, skills and plugins, subagent definitions

Models:Makes Claude Fable 5.1 the default

What the release notes say

What's changed

  • Added Claude Fable 5.1 (claude-fable-5-1), now the default Fable model — 1M context, $10/$50 per Mtok with $0.25/Mtok cache reads
  • Added "Time format" (timeFormat) and timeZone settings: 12-hour, 24-hour, 24-hour UTC, or a strftime pattern for the turn-end clock and transcript-view timestamps
  • Added a Containment Escape rule to auto mode so cloud metadata-credential fetches, egress evasion, and cross-tenant reach are no longer auto-approved unless your environment marks them expected
  • Added CLAUDE_CODE_SUBAGENT_MODEL_FORCE to apply CLAUDE_CODE_SUBAGENT_MODEL (or the main model) to every subagent, ignoring per-spawn and agent-definition model overrides
  • Added s in /effort to change effort for the current session only, matching /model
  • Added a /doctor warning for stale sandbox mask files left by a killed session
  • Added a one-time prompt in auto mode before the first file read outside the working directories, with the option to block such reads (permissions.blockReadsOutsideWorkingDirectories)
  • Added support for a gateway-supplied description on discovered /model picker entries (CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY); entries without one still read "From gateway"
  • Fixed settings in a .claude/ folder created after startup not being picked up until restart
  • Fixed sessions dispatched from an agent view opened with ← always starting in the original session's permission mode, overriding the target directory's defaultMode and the agent's permissionMode
  • Fixed keybindings.json rebinds of Ctrl+G being ignored in claude agents; its Ctrl+S / Ctrl+T are now rebindable via the new Agents context
  • Fixed background sessions failing to start on macOS npm installs during a self-update, and on Windows when a stale daemon lock file pointed at a reused process id
  • Fixed the working spinner stopping while a response streams behind a slash-command panel
  • Fixed a background session's state.json detail repeating its own dispatch prompt after a scheduled wake-up
  • Fixed claude agents keeping a background session you re-prompted buried in Completed after it finished again; Completed now orders by the latest finish
  • Fixed claude --bg from a directory that was just deleted reporting "backgrounded" and leaving a crashed session row; it now prints the reason and exits 1
  • Fixed Remote Control connecting mid-session re-sending the Bash tool definition, causing a prompt-cache miss
  • Fixed a doubly-listed custom Authorization header overriding the configured credential on Bedrock, Mantle, Vertex, and WIF, and the Vertex setup wizard picking up a leftover Anthropic profile from ~/.config/anthropic
  • Fixed Claude apps gateway sending stray host Authorization or profile headers to Foundry, Vertex, and Bedrock, and Foundry Entra ID upstreams not starting when ANTHROPIC_FOUNDRY_API_KEY is set
  • Fixed a leftover Anthropic API key or auth token being sent alongside your Foundry subscription key in API-key mode
  • Fixed /schedule routines whose prompt was saved without a message role and then ran with nothing to do
  • Fixed claude agents not saying that a background session is waiting for you to approve a message from another session, or who sent it
  • Fixed a prompt stashed with Ctrl+S inside an opened background session being lost when the session went idle or was stopped and then reopened
  • Fixed telemetry (OTEL) settings pushed through server-managed settings being ignored on warm starts, including desktop-app Code sessions
  • Fixed a teammate permission request being answered twice when the leader's mailbox write was briefly locked
  • Fixed a phantom duplicate slash-command row rendering below the in-flight turn while a command's auto-continued response streamed
  • Fixed policyHelper timeoutMs and refreshIntervalMs values above the timer maximum (2147483647) causing failures or re-runs every millisecond; they are now clamped
  • Fixed the token counter freezing or crawling after switching to another subagent's transcript, and made background subagents' and teammates' counters update live while a response streams
  • Fixed sandbox network hosts written with a trailing dot (example.com.): a deniedDomains entry didn't block the host inside the sandbox, and "don't ask again" for such a host kept prompting
  • Fixed dismissing the Remote Control consent prompt (Esc, or n at claude remote-control) counting as consent, so the next request connected without asking
  • Fixed /mcp reconnect and enable still connecting a settings-file MCP server that a managed MCP allow/deny list or strictPluginOnlyCustomization loaded after startup should block
  • Fixed claude mcp remove leaving a remote server's stored OAuth credentials behind when strictPluginOnlyCustomization locks MCP to plugin-only servers
  • Fixed Remote Control (claude remote-control) sessions started from the Claude app ignoring the selected model and running on the machine's default instead
  • Fixed --disallowedTools and session deny rules being dropped after the first settings reload when allowManagedPermissionRulesOnly is enabled
  • Fixed --resume listing a backgrounded conversation twice and --continue reopening its stalled pre-background copy; --continue now also opens finished background sessions
  • Fixed fullscreen mode not letting you click ! shell command output to expand it
  • Fixed background sessions left running an older Claude Code binary piling up across auto-updates instead of being retired
  • Fixed claude agents --json briefly switching the terminal to raw mode and undoing another program's terminal settings on exit
  • Fixed Proactive output style sessions busy-looping with filler messages and repeated log reads instead of idling while a background command or Monitor they started is still running