Module roots 

MCP client-roots adoption (opt-in, fallback-only).

Some hosts advertise the directory the user is working in via the MCP roots capability — opencode does it on every connection. This module consumes that advertisement so a server configured with workspace.adopt_client_roots: true and no workspace.root can bind the client’s directory instead of making the operator hand-write a path the client already offered.

Three properties this module exists to preserve, in order:

1. Fallback only. Anything the operator configured — manifest workspace.root, --watch, --source-root, --workspace, or a runtime set_root_dir — makes the workspace RootOwnership::Operator, and adoption refuses to touch it. Forever, including across later roots/list_changed notifications.
2. Contained. Adoption calls Workspace::adopt_client_root, which is the same validate-canonicalize-contain-activate path set_root_dir uses. A workspace.sandbox_root boundary therefore applies identically to a path proposed by an external party. The spec is explicit that roots are “informational guidance rather than an access-control mechanism” — the boundary is what contains them.
3. Invisible to everyone else. The guard chain is ordered cheapest-first and exits before any I/O for a server that did not opt in or a client that does not advertise roots, so no roots/list request is ever put on the wire for such a client and no connect latency is added. The handler also runs on a task rmcp spawns, so even the opted-in path never delays the client’s session.

Deprecated upstream

MCP roots is deprecated as of protocol revision 2026-07-28 (SEP-2577): “New implementations SHOULD NOT adopt it; existing implementations SHOULD migrate to passing directories or files via tool parameters, resource URIs, or server configuration.” It is eligible for removal in the first revision released on or after 2027-07-28, and that revision drops the server→client roots/list request and notifications/roots/list_changed entirely.

This module is built anyway, deliberately: it is opt-in, so it costs deployments that do not enable it nothing, and rmcp negotiates 2025-11-25, where the mechanism is live and fully implemented. The migration path when it goes away is the one the spec names — pass the directory via a tool parameter, a resource URI, or server configuration (workspace.root).

Functions

file_uri_to_path

Convert a file:// URI to a filesystem path.