← Claude Code changelog

Claude Code 2.1.257

This release introduces Fable 5.1 as the new default model, offering an expansive 1M context window and updated pricing for advanced interactions. It delivers crucial security enhancements, including containment escape rules, file read prompts outside working directories, and stronger permission checks to safeguard your environment. Extensive performance improvements ensure faster rendering, more responsive input, and smoother streaming, while a broad array of fixes address critical reliability issues like background session failures, prompt cache misses, and credential handling for cloud integrations. Dedicated updates for VSCode users provide a revamped model picker, output style selection, and improved session management, collectively enhancing the overall experience for all users with a focus on stability and security.

Added

  • 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"
  • Added collapsible ACCOUNT & USAGE and SESSION MANAGER section headers to the session list panel, with the account email, the usage meter, and a View details link opening the usage dialog
  • Added a model pill to the input footer that shows the current model and opens the model picker, with an Effort row and a "More models" page
  • Added a collapse toggle to the Ungrouped section of the session list
  • Added output style selection to the command menu, including custom styles

Improved

  • Improved rendering performance: less re-render work per turn in long conversations, streaming no longer slows down as the reply grows, and background-agent updates no longer re-render the whole screen
  • Improved prompt input responsiveness by reducing per-keystroke rendering work
  • Improved policy helper diagnostics — refresh failures now show in `/status`, declining the managed-settings dialog prints why Claude Code exited, and helper timeouts are reported as timeouts
  • Improved `/code-review --comment` to post findings on GitLab merge requests via `glab mr note` instead of reporting the target as unsupported
  • Improved notifications: an MCP elicitation or permission ask queued under another dialog now sends its idle desktop notification at the same delay as a visible ask
  • Improved verbose/transcript output: async hook completion notices that arrive together now appear on one line instead of one line per hook
  • Improved `claude self-hosted-runner --configure-git` to also enable git push negotiation, so the first push of a new branch from a stale clone uploads only the new commits instead of the whole tree
  • Improved liveness reporting to SDK hosts while a response is held open by gateway keep-alives, so long waits under a raised `CLAUDE_STREAM_IDLE_TIMEOUT_MS` are not mistaken for a hung session
  • Improved MCP connection and OAuth debug/error logs so credentials carried in a server's URL or request headers are redacted
  • Improved `/fork` to keep the original conversation's prompt cache in the new background session: its worktree briefing now arrives as a message instead of a system-prompt change
  • Improved emoji autocomplete to accept the remaining GitHub/Slack shortcode aliases (`:satisfied:`, `:telephone:`, `:collision:`, …)

Changed

  • Changed `--effort` to lift a new model's default-effort hold for that session only rather than permanently; an effort picked on claude.ai for a Remote Control session now applies during the hold
  • Changed a `policyHelper` in MDM or `managed-settings.json` shadowed at launch by cached server-managed settings to run (or exit) as soon as the fetch reports them removed, not at the next launch
  • Changed `managedSourcesBehavior: "merge"` to take `sandbox.credentials.awsPairs` and `sandbox.ripgrep` whole from the highest managed source that sets them instead of combining the sources' values
  • Changed gateway model discovery (`CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY=1`) to run even when `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC` is set, since it only queries your gateway
  • Changed `claude --resume <session-id> --bg` to continue that session under its own ID when nothing is running it, instead of silently starting a copy; a copy is now announced
  • Changed `/btw` history browsing from `←`/`→` to `Shift+←`/`Shift+→` (or `[`/`]`), stepping through your recent side questions and back to the live answer
  • Changed `defaultMode: "bypassPermissions"` in `.claude/settings.json` or `.claude/settings.local.json` to be ignored, like `"auto"`; set it in user or managed settings, or pass `--permission-mode`
  • Changed `fable` and `best` in Claude apps gateway sessions to keep resolving to Fable 5 for now, since gateways not yet configured for Fable 5.1 reject it; pick Fable 5.1 in `/model` to use it
  • Changed `--add-dir`, `/add-dir`, and `additionalDirectories` to refuse network paths (UNC shares, `/net/<host>` automounts) with a message before touching them; on Windows use a mapped drive letter
  • Changed Claude apps gateway sign-in and token refresh requests to verify the gateway's pinned TLS certificate, as the managed settings fetch already does
  • Changed Cowork and claude.ai cloud sessions: reading an artifact that isn't yours now always asks you first, even in auto mode
  • Changed the action menu to list slash commands in a filterable "Slash commands" dialog instead of inline; picking one runs it; the MCP servers dialog gained the same filter box
  • Changed "Delete session" to "Archive session": archived sessions move to a collapsible "Archived sessions" group at the bottom of the list with an Unarchive action

Fixed

  • 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
  • Fixed subagents stopping when a response was cut off mid-stream by a computer sleep, dropped connection, or server error; they now automatically continue instead of ending with an incomplete response
  • Fixed `←` doing nothing in the `/btw` panel inside a `claude agents` session: it now returns to the agents list (even mid-answer), and the panel comes back when you reopen the session
  • Fixed sessions with an advisor model set missing the prompt cache on background requests (compaction, `/recap`, prompt suggestions) and re-sending the full conversation uncached each time
  • Fixed `claude -p` exiting about 5 seconds after its final result while a Monitor the model armed was still running; it now waits for the watch to fire or time out
  • Fixed a `permissions.ask` rule being skipped in auto mode when the matching command ran inside a compound command or subshell, letting it run without the confirmation prompt
  • Fixed plugins being able to read files outside their own directory through a declared command, agent, skill, hooks or other component path that is a symlink; such paths are now refused with an error
  • Fixed `/add-dir` rejecting a directory inside the current working directory; it now loads that directory's skills, commands, and agents like `--add-dir` does at startup
  • Fixed the main agent not being told when you resume a subagent you had stopped from its transcript view
  • Fixed a crash when pasting ANSI-colored text (e.g. a CI log) into dialogs like `/feedback`
  • Fixed `claude mcp add/remove` hanging or exhausting memory when the project's `.mcp.json` is a FIFO or a device-file symlink; it now fails fast with an actionable message
  • Fixed unbounded memory growth when non-JSONL data is piped into `claude -p --input-format stream-json`; it now fails fast with a clear error
  • Fixed backgrounding a turn (`←` or Ctrl+B) while a subagent or other tool was running occasionally making the background session treat that tool as rejected instead of re-running it
  • Fixed Bash `Read()`/`Edit()` deny rules not applying to `< file` redirects and reader commands like `tac` and `egrep`; a deny rule on any argument or redirect target now refuses the command
  • Fixed resuming or messaging a subagent whose transcript had grown past 5 MB (for example after reading many images) failing with "No transcript found"
  • Fixed worktree-isolated sessions refusing Bash loops, `$VAR` reads, `"$(…)"` and heredocs that never touch git as "too complex to verify that it stays inside the worktree"
  • Fixed `/model` and `/effort` showing a prompt-cache warning after rewinding a conversation back to empty
  • Fixed prompt-cache misses on every turn in long screenshot-heavy sessions once images exceeded the per-request size cap
  • Fixed the Edit permission prompt's diff view rendering emoji and multi-code-point characters with incorrect widths
  • Fixed WebSocket MCP server connection failures being logged as "[object ErrorEvent]" instead of the underlying error
  • Fixed background sessions failing to open with "Couldn't start the background service" while another Claude Code process was downloading an npm update; the start now waits for it
  • Fixed background commands that detach from their shell (for example under `timeout` or `setsid`) surviving a task stop or Claude Code exit
  • Fixed Claude not being told when you stop a background command from the tasks panel or a connected client
  • Fixed stopping a background subagent leaving its monitors running
  • Fixed sandboxed git commands in a linked worktree losing write access to the repository's common `.git` directory after `cd` into a subdirectory
  • Fixed Bedrock and Bedrock Mantle requests going silent during long hidden-thinking phases on Opus 4.7 and later, which let idle timeouts cut the connection; the stream now carries progress events
  • Fixed launching Claude Code after a Claude apps gateway expired or revoked your session: it now says the session ended and offers `/login` instead of reporting a network error
  • Fixed cloud sessions losing git/GitHub credentials for the rest of the session when the session's network proxy failed to start at launch; it now retries in the background and recovers
  • Fixed leftover `cc-daemon-*` folders in the system temp directory after an interrupted background daemon start; the `cleanupPeriodDays` retention sweep now removes them
  • Fixed Bash permission checks auto-approving certain `[[ ]]` conditionals that zsh parses differently from bash; these commands now prompt for approval
  • Fixed the managed-settings approval prompt showing the generic warning instead of its telemetry wording when the settings also turn detailed tracing or raw API body logging off, or trace export on
  • Fixed agent-team teammates in tmux/iTerm2 panes sometimes staying open after acknowledging a shutdown request
  • Fixed the keyless Console sign-in ("Sign in with your Console account") not applying your organization's server-managed settings, and `/status` not showing the Organization for that sign-in
  • Fixed third-party provider deployments (Bedrock, Vertex, and others) still showing claude.ai-only features (remote sessions, dictation, usage) and calling claude.ai with a leftover login
  • Fixed the session list panel's usage meter staying blank after the panel loads; it now shows the last known usage immediately
  • Fixed the "Enable Remote Control for all sessions" toggle so turning it on or off applies to sessions that are already open, not only to new ones
  • Fixed screen reader announcements: a control character before a fence or heading no longer drops visible lines from speech, and bold markers spanning a heading are no longer mis-paired

Removed

  • Removed the Ctrl+E command explanation on Bash and PowerShell permission prompts