feat(connector-mcp): adopt MCP servers as connectors (ADR-0024)#1424
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Add @objectstack/connector-mcp — a single generic adapter that turns any
Model Context Protocol server into an ordinary type:'api' connector on the
automation engine, with no per-server code.
- createMcpConnector(): connect over stdio or streamable-HTTP, call
tools/list, map each tool to a connector action (name→key,
description→label/description, inputSchema→inputSchema), and dispatch
connector_action calls to tools/call. Results normalise to the shared
{ ok, content, ... } envelope; logical tool errors surface as ok:false.
- ConnectorMcpPlugin: registers via the existing engine.registerConnector()
path (no new engine surface, no mcp_call node) and tears the MCP connection
down on destroy(). Fail-soft when the server or automation engine is absent.
- Credentials stay with the MCP server (transport env/headers), never in
ConnectorSchema or the discovery-exposed def.
- Mirrors the connector-rest/connector-slack conventions; the real MCP SDK
client is lazily imported and injectable so unit tests stay hermetic.
https://claude.ai/code/session_01G9v2WA48voVBSkQ7sjFkqC
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Keeps @objectstack/connector-mcp versioned in lockstep with the rest of the public monorepo, satisfying scripts/check-changeset-fixed.mjs (the Validate Package Dependencies CI gate). https://claude.ai/code/session_01G9v2WA48voVBSkQ7sjFkqC
os-zhuang
marked this pull request as ready for review
May 31, 2026 23:05
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Summary
Implements ADR-0024: ship
@objectstack/connector-mcp, a single generic adapter that turns any Model Context Protocol (MCP) server into an ordinarytype: 'api'connector on the automation engine — with no per-server code. One adapter unlocks the entire MCP ecosystem (filesystem, GitHub, Slack, databases, search, hundreds of community servers).What's in the package
Mirrors the
connector-rest/connector-slackconventions (Apache-2.0, tsup build, acreate…Connectorfactory + a…Plugin).createMcpConnector({ transport, include?, … })— connects over stdio or streamable-HTTP, callstools/list, and builds theConnectordefinition once. Each tool maps mechanically to an action (name → key,description → label/description,inputSchema → inputSchema); each handler closes over the tool name and dispatches totools/call. Results normalise to the shared{ ok, content, … }envelope — a logical tool error surfaces asok: falserather than throwing, so a flow can branch on${node.ok}.ConnectorMcpPlugin— registers the connector through the existingengine.registerConnector()path (no new engine surface, nomcp_callnode, no parallel registry — the anti-patterns ADR-0024 §5 rules out) and tears the MCP connection down ondestroy(). Fail-soft: an unreachable server or a missing automation engine is logged and skipped.connector_actionnode, the discovery route, and the Studio palette all see a plain connector — they never know it is MCP-backed (ADR-0024 §2).Security posture (ADR-0024 §3)
Credentials live with the MCP server, not in
ConnectorSchema. The operator-supplied transportenv(stdio) /headers(http) are passed straight to the MCP client and kept out of the serialized, discovery-exposeddef. The open tier runs an operator-provided server with operator-provided credentials; managed secrets, per-tenant lifecycle, and sandboxed stdio execution remain the enterprise tier (§4).Implementation notes
clientFactory), mirroringconnector-rest'sfetchImpl— so unit tests stay hermetic and the SDK only loads when a real connection is made.Pluginlifecycle exposesdestroy()(notstop()), so teardown is wired todestroy()to ensure the MCP connection / child process is actually released on shutdown.Testing
pnpm build— ✅ ESM + CJS + DTSpnpm exec tsc --noEmit— ✅ strictpnpm test— ✅ 9 passing (discovery → action mapping,includeallowlist,tools/calldispatch + result normalisation incl.isError, lifecycle/close, and an end-to-end flow throughLiteKernel+ the automation engine)Follow-ups (out of scope, per ADR-0024)
examples/entry (reference filesystem / GitHub MCP server → allowlisted actions in a flow).https://claude.ai/code/session_01G9v2WA48voVBSkQ7sjFkqC
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