# Week 36 · August 31 – September 4, 2026

> Switch to Claude Fable 5.1, let computer use run in the background on Desktop, and watch Claude's edits in a live /diff panel.

Releases [v2.1.251 → v2.1.261](https://code.claude.com/docs/en/changelog.md#2-1-251)
4 features · August 31 – September 4

Claude Fable 5.1
new model

Claude Fable 5.1 is available in Claude Code with a 1M-token context window, and the `fable` alias now selects it. In Claude apps gateway sessions, `fable` still selects Fable 5. If your gateway serves Fable 5.1, run `/model claude-fable-5-1`. Requires v2.1.257 or later.

Switch the current session to Fable 5.1 and save it as your default:

```text Claude Code theme={null}
> /model fable
```

On the Anthropic API, the picker lists Fable only once the server reports it available for your organization, but typing `/model fable` checks with the server directly.

[Work with Fable](https://code.claude.com/docs/en/model-config.md#work-with-fable)

Computer use runs in the background on Desktop
Desktop

On macOS, computer use in the Claude Code Desktop app now works in the background: Claude sees and acts in the apps you've approved while you keep working. Background computer use is in beta on Pro and Max plans.

![A Claude Code Desktop session where Claude asks to use Xcode, with a Computer use permission card that reads Let Claude see and act in the apps you approve, in the background or with full control of your screen, next to an Enable button](https://mintcdn.com/claude-code/f9HTZGyMtxIFOUgt/images/whats-new/background-computer-use.jpg?fit=max\&auto=format\&n=f9HTZGyMtxIFOUgt\&q=85\&s=a599a6c6fa544cb8d1b426b93706caf4)

[Let Claude use your computer](https://code.claude.com/docs/en/desktop.md#let-claude-use-your-computer)

Live diff panel in fullscreen rendering
v2.1.260

In fullscreen rendering, `/diff` now opens a panel beside the conversation instead of a viewer you have to close. The panel lists the changed files with their added and removed line counts and refreshes each time Claude edits a file or runs a shell command. Select lines in the panel with the mouse to attach them to your next prompt.

<video autoPlay muted loop playsInline src="https://mintcdn.com/claude-code/f9HTZGyMtxIFOUgt/images/whats-new/diff-panel.mp4?fit=max&auto=format&n=f9HTZGyMtxIFOUgt&q=85&s=9d7553c19e7f227891cd95f1f59d796d" />

With fullscreen rendering on, inside a git repository, and in a terminal at least 110 columns wide, toggle the panel:

```text Claude Code theme={null}
> /diff
```

Run `/diff` again or click the `✕` in its header to close it.

[Diff panel](https://code.claude.com/docs/en/interactive-mode.md#diff-panel)

Find unused skills with /skill-doctor
CLI

`/skill-doctor` shows what each of your skills costs in context and how often it gets used, so you can decide which ones to turn off. Every skill in the [skill listing](https://code.claude.com/docs/en/skills.md#skill-descriptions-are-cut-short) adds to your context on every turn, whether or not Claude ever uses it. Requires v2.1.252 or later and isn't available in sessions that skip [feature-flag fetching](https://code.claude.com/docs/en/env-vars.md#features-that-need-feature-flag-fetching).

Run it in an interactive session to open the report in the `/plugin` manager's **Stats** tab:

```text Claude Code theme={null}
> /skill-doctor
```

In non-interactive mode with `-p`, Claude Code prints the report as text instead.

[Find unused skills](https://code.claude.com/docs/en/skills.md#find-unused-skills)

Other wins

A [`PreModelSwitch`](https://code.claude.com/docs/en/hooks#premodelswitch) hook can block a model switch you request, and a [`PostModelSwitch`](https://code.claude.com/docs/en/hooks#postmodelswitch) hook can add context for Claude after the session's model changes[`/cost`](https://code.claude.com/docs/en/costs#prompt-cache-statistics) adds a `Prompt cache (main)` line: the share of input tokens served from cache, the cache misses, whether the cache is warm, and a likely cause for the last miss when Claude Code can name one. Status line scripts get a matching `prompt_cache` objectOrganizations can list HTTP and SSE MCP servers under the [`managedMcpServers`](https://code.claude.com/docs/en/managed-mcp#provide-servers-through-managed-settings) managed setting to give them to every user, in addition to the servers that users add on their own`/effort` and the `/model` picker now [save a separate effort level for each model](https://code.claude.com/docs/en/model-config.md#adjust-effort-level); press `s` instead of `Enter` to apply a level to the current session onlyBy default, the auto mode classifier [now also blocks](https://code.claude.com/docs/en/permission-modes.md#what-the-classifier-blocks-by-default) actions such as requesting credentials from the cloud instance-metadata endpoint or connecting to sibling containers that Claude didn't startIn auto mode, Claude Code asks you before Claude [first reads a file outside your working directories](https://code.claude.com/docs/en/permission-modes.md#first-read-outside-the-working-directories), with an option to block such reads from then onRaise [`bashOutputMaxChars`](https://code.claude.com/docs/en/settings-reference#bashoutputmaxchars) and [`taskOutputMaxChars`](https://code.claude.com/docs/en/settings-reference#taskoutputmaxchars), up to 128,000 characters, so Claude receives more of the output from a successful command or background task inlineThe prompt's [word-editing shortcuts follow readline](https://code.claude.com/docs/en/interactive-mode.md#make-ctrl-w-delete-back-to-whitespace) for everyone, and the `keybindingFlavor` setting no longer has any effect. `Ctrl+W` deletes back to the previous whitespace, and `Alt+B`, `Alt+F`, and `Alt+D` treat punctuation such as `/` and `.` as word breaksIf you set `defaultMode` to `"bypassPermissions"` in a project's `.claude/settings.json` or `.claude/settings.local.json`, it [no longer takes effect](https://code.claude.com/docs/en/permission-modes.md#which-mode-a-session-starts-in) and the session starts in Manual mode; set `"bypassPermissions"` in user or managed settings instead, or pass `--permission-mode`Seat-based Enterprise plans now [default to Opus 5](https://code.claude.com/docs/en/model-config.md#default-model-setting)In the VS Code extension, click the model name at the bottom of the prompt box to [open the model picker](https://code.claude.com/docs/en/vs-code.md#use-the-prompt-box)In the VS Code extension, select **Output styles** in the command menu's Customize section to [pick an output style](https://code.claude.com/docs/en/vs-code.md#use-the-prompt-box), including your custom ones

[Full changelog for v2.1.251–v2.1.261 →](https://code.claude.com/docs/en/changelog.md#2-1-251)