Expose browser filesystem through MCP

[masnwilliams]

summary

• add a manage_browser_files MCP tool backed by the existing browser filesystem SDK
• support text and base64 writes/uploads, embedded-resource downloads, directory archives, and filesystem management actions
• register the toolset and document the new model-facing capability

testing

• bun test (90 tests passed)
• bunx tsc --noEmit
• targeted Prettier check for changed files
• bun run build compiled and typechecked successfully, then stopped during page-data collection because KERNEL_CLI_PROD_CLIENT_ID is not set in the local environment

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Note

Medium Risk
Destructive VM filesystem actions (delete, move, permission changes) are exposed to authenticated MCP clients; behavior is bounded to per-session browser VMs but misuse or path mistakes could affect automation artifacts.

Overview
Introduces manage_browser_files, a new manage_* MCP tool that exposes filesystem operations on running browser VMs via client.browsers.fs. Models can list, inspect, read, write, upload (including multi-file and zip extract), download files or directory zips, and perform moves, deletes, mkdir, and permission changes—all scoped by session_id and an action parameter.

Read vs download: text reads return plain text; download and download_dir_zip return embedded MCP resources (kernel-browser-file://… URIs with base64 blobs). Writes and uploads accept utf8 or base64 content (with validation before hitting the API), since the server cannot read the caller’s local paths.

Registration adds the browser_files toolset (aliases browser_fs, manage_browser_files), updates the disabled-toolsets test list, and bumps the README model-facing tool count to 18.

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Project	Deployment	Actions	Updated (UTC)
mcp	Ready	Preview	Aug 7, 2026 6:14pm

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