What probably matters to youSection of the release
What
Turning Fast mode on or off, from /config, /fast or the fast-mode picker, now checks for in-flight turns and runs your PreModelSwitch hook against the model it would move to. If the hook denies it or answers "ask", fast mode stays off and you get an error telling you to run /model to switch first, then enable fast mode. This used to be an immediate state flip with no checks.
Details
The toggle now shows a cancellable "Applying fast mode…" / "Waiting for the workspace…" state while the hook runs.
If the model changes underneath the hook, the toggle is abandoned with a message asking you to try again.
The fast mode option itself only appears when its own two internal checks pass.
Evidence
Fast mode was not enabled: the model changed while PreModelSwitch hooks ran; try again, Model switch blocked by a PreModelSwitch hook
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed sinceAnthropic's documentation has since written up /fast, on Extension Support Matrix.| [fast-agent](https://github.com/evalstate/fast-agent) | | | | [Partial](https://github.com/evalstate/fast-agent/blob/main/docs/docs/mcp/skills-over-mcp.md) |extensions/client-matrixsee the edit
Added sinceA small documentation edit on Speed up responses with fast mode touched a line naming /fast after this was published.* **Usage credits turned on for subscription plans**: on a Pro, Max, Team, or Enterprise plan, your account must have [usage credits](/docs/en/costs#add-usage-credits-to-your-subscription) turned on, which allows billing beyond your plan's…fast-modesee the edit
Added sinceA small documentation edit on Telemetry and egress touched a line naming /config after this was published.With `disableEssentialTelemetry`, `disableNonessentialTelemetry`, `disableNonessentialServices`, and `disableAutoUpdates` all set to `true`, the desktop application makes **no outbound connections to Anthropic-operated hosts at runtime**. …third-party/claude-desktop/telemetrysee the edit
Confirmed sinceAnthropic's documentation has since written up /config, on MCP, plugins, skills, and hooks.| `.mcp.json` | MCP servers bundled with this plugin. A JSON object keyed by server name: `{"mcpServers": {"<name>": {"type": "http", "url": "...", "oauth": true}}}`. A remote entry uses `type` (`http` or `sse`), not `transport`, and suppo…third-party/claude-desktop/extensionssee the edit
How sure we are
Two sources agreeTwo things we can check say the same as this entry.
Anthropic's documentation agreesAnthropic's documentation has since written up /config, on MCP, plugins, skills, and hooks.
Anthropic's release notes agreeAdded PreModelSwitch and PostModelSwitch hook events (block, confirm, or annotate a model switch); SessionStart resume hooks now receive…
