Claude in Chrome file uploads gain a hosted path and a size limit

What

Claude in Chrome lets Claude control your Chrome browser, and its file_upload action uploads files to a web page. It used to be prepared only on your own machine. Now:

• In hosted setups, the host can read the files instead of a local read, and the upload can pass a maxTotalBytes limit (from FILE_UPLOAD_MAX_TOTAL_BYTES) plus the hosted session.
• A new anthropic/chromeUploadMaxBytes setting caps the upload size.
• file_upload now takes paths rather than files.
• file_upload is refused only in a remote session with no host.
• file_upload cannot run inside browser_batch, which bundles several browser actions. In that case the whole call is refused with the message 'file_upload cannot run inside browser_batch in this session', and nothing in the call runs.

MCP servers are add-on programs that provide tools. MCP tool calls can now merge extra details, mcpCallMeta, into the request's _meta field, which is how the upload passes its information along.

Separately, when an MCP session expires and is reconnected, a tool call is retried only if it cannot have run already, the tool is safe to run at the same time as others, or the tool says repeating it is harmless (idempotentHint). Before, it was always retried.

Why

Browser file uploads can work in hosted or remote setups within a size limit. Batched browser actions that include an upload now fail as a whole, and MCP tools that change things are not run twice after a reconnect.