What
In a component that handles tabs, MCP clients, and search, pressing the Tab key used to move focus the same way Left/Right arrow keys do. Now Tab only prevents its default browser behavior and no longer triggers that navigation.
Why
This stops Tab from being treated as an extra pair of arrow keys in this component, which likely avoids surprising focus jumps for anyone using Tab for its usual purpose nearby.
Names in the bundleTab
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 since
Anthropic's documentation has since written up Tab, on Create a Message Batch.
- `close_tab: optional BetaBrowserCloseTabConfig or null`api/beta/messages/batches/create see the edit
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
The finding does not say what, if anything, Tab does now besides preventing default, or which specific pane/search UI this affects.
Anthropic's documentation agrees
Anthropic's documentation has since written up Tab, on Create a Message Batch.