[sanchitrk]

Summary

Stacked on #80. Adds MCP resources, and handling for results the model isn't shown in full. Everything stays on the host: MCP runs in the harness process and never touches a session's sandbox, local or remote.

Resource tools (src/mcp/resources.ts)

• list_mcp_resources, list_mcp_resource_templates and read_mcp_resource, named and shaped like the tools other agents use, so models trained on them use them unchanged.
• They're registered when any enabled, non-hidden server offers resources, and reach every such server when they run.
• With a server, one page is listed and cursor continues it. Without one, every page of every server is listed, and servers that fail go into errors.
• MCP App resources (ui://, profile=mcp-app) and icons are left out of listings.
• Reads become text and images; several contents are labelled with their URIs.

Result content (src/mcp/content.ts)

• Text over 20 KB keeps its start and end, cut in the middle, and the full text is saved to a file whose path the result names.
• Binary resources are saved; text-typed blobs (text/*, JSON, XML) are shown as text.
• Resource links name read_mcp_resource when the server's resources can be read.

Saved files (src/mcp/output.ts)

• They go to the host temp directory as codework-mcp-*, mode 0600, created exclusively, never into a sandbox.

One request path (src/mcp/mcp.ts)

• Tool calls and resource requests share it: the current connection is looked up when the request runs, a dropped one reconnects, an expired HTTP session gets one more attempt on a new session, and a sign-in failure is reported. Tool calls are still never retried otherwise.

Docs

• A new page, customize/mcp: where servers run (always on your machine), mcp.json, project overrides, exposure, resources, connections.

Review fixes (2026-10-15)

• Strict paging. Listing every server's resources or templates uses the SDK's own pagination and limits, as tools() does. A server repeating a cursor can't keep a listing running.
• Opaque cursors. A cursor goes back exactly as the server gave it; only server names and URIs are trimmed. The fixture's cursor is now " page-2 " to prove it.
• Test cleanup. Tests remove the files they save, and read saved paths between the message's own delimiters, so a temp directory with spaces still parses.
• Docs. Which servers a message waits for, that exposure changes keep a server running, and where server logs go.

Review fixes (2026-10-24)

• Blank cursor: cursor: "" means no cursor; any other cursor still goes back exactly as given.
• Connecting servers: resource tools wait for servers still connecting, so none is silently left out of a listing.
• Errors: resource failures carry the server's own message; listings already name the server beside it.
• Docs: where stdio servers start off a local sandbox, $NAME values, command caching, sign-in, and retries after a failed connect.
• Tests: the third exchange lists with a blank cursor.
• Images: tool and resource images go through the shared inline pipeline (format conversion and resizing, as the read tool does); one that can't be converted becomes a note.

Test plan

• test/mcp.session.test.ts gains a third exchange, through the full harness against a real stdio server. It covers:
  • the server's configured cwd
  • a resource link
  • a 30 KB result cut below 21 KB, with the saved file holding all of it
  • listing every page and paging one server by cursor, with the ui:// resource left out
  • templates
  • a text read and a binary read, with the binary saved as a 0600 host file holding the right bytes
  • an unknown server
• test/mcp.client.test.ts: artifact updated for saved binaries and resource links
• Full harness suite: 514 passed, 34 skipped (live/remote)
• vp check and vp run typecheck

🤖 Generated with Claude Code

[sanchitrk]

Review (2026-10-24)

Resource tools, truncation, saved files and the ui:// filter all check out.

should-fix: a blank cursor should mean no cursor

• Where: resources.ts (L121 in this head) keeps cursor: "".
• Why it matters: models often fill optional strings with "".
  • With no server, list_mcp_resources({ cursor: "" }) fails with "cursor can only be used when a server is specified".
  • With a server, "" is sent to it as a cursor, and many servers reject it.
• Fix: keep non-blank cursors byte-exact, but treat blank ones as absent: value.trim() === "" ? undefined : value.

Confirmed, no action:

• The saved-output path isn't readable from a remote sandbox. That was decided (host-only, no notice to the model), so it isn't raised again here.
• Not listing resources at connect, only checking the resources capability, matches current reference behaviour.