# Claude Code v2.1.257

- Product: Claude Code (https://whatsnew.fyi/product/claude-code)
- Vendor: Anthropic
- Date: 2026-09-01
- Version: v2.1.257
- Original notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.257
- Permalink: https://whatsnew.fyi/product/claude-code/releases/v2.1.257

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **added** — Added Claude Fable 5.1 (claude-fable-5-1) as the new default Fable model with 1M context and $10/$50 per Mtok pricing with $0.25/Mtok cache reads
- **added** — Added Time format (timeFormat) and timeZone settings supporting 12-hour, 24-hour, 24-hour UTC, or custom strftime patterns for turn-end clock and transcript-view timestamps
- **added** — Added Containment Escape rule to auto mode to prevent auto-approval of cloud metadata-credential fetches, egress evasion, and cross-tenant reach unless marked as expected
- **added** — Added CLAUDE_CODE_SUBAGENT_MODEL_FORCE environment variable to apply the configured subagent model to every subagent, ignoring per-spawn and agent-definition model overrides
- **added** — Added s flag in /effort command to change effort for the current session only, matching /model behavior
- **added** — Added /doctor warning for stale sandbox mask files left by killed sessions
- **added** — Added one-time prompt in auto mode before first file read outside working directories with option to block such reads via permissions.blockReadsOutsideWorkingDirectories
- **added** — Added support for gateway-supplied description on discovered /model picker entries via CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY
- **added** — Added Agents context to make Ctrl+S and Ctrl+T rebindable in claude agents
- **fixed** — Fixed settings in a .claude/ folder created after startup not being picked up until restart
- **fixed** — Fixed sessions dispatched from an agent view opened with ← always starting in the original session's permission mode instead of respecting target directory's defaultMode and agent's permissionMode
- **fixed** — Fixed keybindings.json rebinds of Ctrl+G being ignored in claude agents
- **fixed** — Fixed background sessions failing to start on macOS npm installs during self-update and on Windows when a stale daemon lock file pointed at a reused process id
- **fixed** — Fixed the working spinner stopping while a response streams behind a slash-command panel
- **fixed** — Fixed background session state.json detail repeating its own dispatch prompt after a scheduled wake-up
- **fixed** — Fixed claude agents keeping a background session re-prompted buried in Completed after it finished again; Completed now orders by latest finish
- **fixed** — Fixed claude --bg from a directory that was just deleted reporting backgrounded and leaving a crashed session row; now prints reason and exits 1
- **fixed** — Fixed Remote Control connecting mid-session re-sending the Bash tool definition, causing a prompt-cache miss
- **fixed** — Fixed doubly-listed custom Authorization header overriding configured credential on Bedrock, Mantle, Vertex, and WIF; Vertex setup wizard no longer picks up leftover Anthropic profile from ~/.config/anthropic

##### 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

_[Truncated at 4000 characters — full notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.257]_