# Claude Code v2.1.251

- Product: Claude Code (https://whatsnew.fyi/product/claude-code)
- Vendor: Anthropic
- Date: 2026-08-28
- Version: v2.1.251
- Original notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.251
- Permalink: https://whatsnew.fyi/product/claude-code/releases/v2.1.251

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 `PreModelSwitch` and `PostModelSwitch` hook events to block, confirm, or annotate a model switch; `SessionStart` resume hooks now receive session staleness and estimated re-cache cost
- **added** — Added live streaming of a foreground subagent's tool calls and results to Remote Control clients
- **added** — Added a Spend limit bar to `/usage` and a `rate_limits.spend_limit` status line field for developers behind a Claude apps gateway with spend limits
- **added** — Added a per-session prompt-cache line to `/cost` with hit ratio, misses, tokens re-cached, and warm/cold status, plus a matching `prompt_cache` object for status line scripts
- **added** — Added `attach`, `logs`, `stop`, `respawn`, and `rm` to `claude --help`; the `--resume` message now names the exact `claude attach <id>` command
- **fixed** — Fixed file tools (Read, Write, Edit) following a symlink swapped inside the working directory after the permission check, which could read or write outside the approved location
- **fixed** — Fixed plugin commands declared in a marketplace entry being able to point outside the plugin directory; such paths are now rejected with a path-traversal error
- **fixed** — Fixed project settings being able to enable detailed beta tracing or raw API body logging, and a lower-scope beta tracing endpoint bypassing an OTLP collector pinned by managed settings or a host app
- **fixed** — Fixed the Workflow tool reading a `scriptPath` outside what the session may read before the permission check ran
- **fixed** — Fixed Grep and Glob not applying `Read(...)` deny rules to files reached through a symlinked search path
- **fixed** — Fixed conversations getting stuck on "text content blocks must be non-empty" errors after a turn where the model produced only thinking
- **fixed** — Fixed the first launch on a fresh install starting in default mode instead of auto mode for accounts whose startup default is auto mode
- **fixed** — Fixed Opus 5 requests failing with "effort ... is not supported when thinking is disabled" when effort was xhigh/max and thinking was turned off; effort is now sent as `high` in that case
- **fixed** — Fixed replying to a message Claude Desktop delivered from another session: `SendMessage` to that session id now delivers through Claude Desktop instead of failing
- **fixed** — Fixed TUI lag with many parallel subagents: per-second progress ticks now replace their predecessor instead of piling up in the transcript
- **fixed** — Fixed agent teams: a teammate's final answer now arrives in the idle notification instead of a content-free "available" notice
- **fixed** — Fixed background subagents being unable to reply to a message from an unnamed sibling or parent agent
- **fixed** — Fixed managed-settings `disableAutoMode` arriving mid-session not moving an already-running auto-mode session back to default mode
- **fixed** — Fixed a "switch to Opus 1M for 5x more context" tip that appeared even when the current Opus model already has a 1M context window
- **fixed** — Fixed Claude apps gateway sessions treating a stored Anthropic profile as active in `/status` and retrying gateway 401s with it

##### What's changed

- Added `PreModelSwitch` and `PostModelSwitch` hook events (block, confirm, or annotate a model switch); `SessionStart` resume hooks now receive session staleness and the estimated re-cache cost
- Added live streaming of a foreground subagent's tool calls and results to Remote Control clients (background subagents, the default, still show status only)
- Added a Spend limit bar to `/usage` and a `rate_limits.spend_limit` status line field for developers behind a Claude apps gateway with spend limits
- Added a per-session prompt-cache line to `/cost` (hit ratio, misses, tokens re-cached, warm/cold) and a matching `prompt_cache` object for status line scripts
- Added `attach`, `logs`, `stop`, `respawn`, and `rm` to `claude --help`; the `--resume` message for a running background session now names the exact `claude attach <id>` command
- Fixed file tools (Read, Write, Edit) following a symlink swapped inside the working directory after the permission check, which could read or write outside the approved location
- Fixed plugin commands declared in a marketplace entry being able to point outside the plugin directory; such paths are now rejected with a path-traversal error
- Fixed project settings being able to enable detailed beta tracing or raw API body logging, and a lower-scope beta tracing endpoint bypassing an OTLP collector pinned by managed settings or a host app
- Fixed the Workflow tool reading (and quoting in errors) a `scriptPath` outside what the session may read before the permission check ran
- Fixed Grep and Glob not applying `Read(...)` deny rules to files reached through a symlinked search path
- Fixed conversations getting stuck on "text content blocks must be non-empty" errors after a turn where the model produced only thinking
- Fixed the first launch on a fresh install starting in default mode instead of auto mode for accounts whose startup default is auto mode
- Fixed Opus 5 requests failing with "effort … is not supported when thinking is disabled" when effort was xhigh/max and thinking was turned off; effort is now sent as `high` in that case
- Fixed replying to a message Claude Desktop delivered from another session: `SendMessage` to that session id now delivers through Claude Desktop instead of failing with "not reachable"
- Fixed TUI lag with many parallel subagents: per-second progress ticks now replace their predecessor instead of piling up in the transcript
- Fixed agent teams: a teammate's final answer not reaching the team lead — it now arrives in the idle notification instead of a content-free "available" notice
- Fixed background subagents being unable to reply to a message from an unnamed sibling or parent agent (`from` was the agent type, which is not an address)
- Fixed managed-settings `disableAutoMode` arriving mid-session not moving an already-running auto-mode session back to default mode
- Fixed a "switch to Opus 1M for 5x more context" tip that appeared even when the current Opus model already has a 1M context window
- Fixed Claude apps gateway sessions treating a stored Anthropic profile (e.g. a Console sign-in) as active: listing it in `/status` and retrying gateway 401s with it, though requests never use it
- Fixed cloud sessions telling Claude the model had changed when the host was only setting the session's initial model
- Fixed Remote Control reporting a failure when an organization's policy disables it; it now shows a single quiet notice instead
- Fixed `/mcp reconnect` on Remote Control showing a generic withheld-detail error instead of the real remedy when a server was disabled in another session
- Fixed `--input-format stream-json`: client-injected assistant tool calls sent without a message id were merged into the first one and their results lost, including when resuming older sessions
- Fixed session transcripts being silently overwritten when a directory change relocated a session onto an existing same-ID transcript
- Fixed background sessions and their

_[Truncated at 4000 characters — full notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.251]_