Require calling MCP::Client#connect before sending requests on stdio transport#427
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koic wants to merge 1 commit into
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Require calling MCP::Client#connect before sending requests on stdio transport#427koic wants to merge 1 commit into
MCP::Client#connect before sending requests on stdio transport#427koic wants to merge 1 commit into
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…o transport ## Motivation and Context The MCP specification requires an `initialize` request followed by `notifications/initialized` before any other interaction. Issue modelcontextprotocol#334 makes that handshake explicit on the stdio client, matching the Python SDK (`ClientSession.initialize()`) and TypeScript SDK (`Client.connect(transport)`). The change was staged to avoid a hard break. Phase 1 (modelcontextprotocol#336) added `MCP::Client::Stdio#connect` while keeping an implicit-init compatibility shim on the first `send_request`. Phase 2 (modelcontextprotocol#338) emitted a deprecation warning when that shim ran. The warning has shipped since 0.16.0, so this final phase removes the shim. ## How Has This Been Tested? `send_request` now raises a `RuntimeError` when `connect` has not been called, and no longer auto-starts the subprocess. `connect` is the sole entry point that spawns the process and performs the handshake, which avoids leaving an orphaned subprocess behind. The stdio test suite was reworked to call `connect` explicitly, a regression test was added for the new guard, and `rake test` passes (1145 runs, 0 failures). ## Breaking Changes Stdio clients that send requests without calling `MCP::Client#connect` now raise a `RuntimeError` instead of silently initializing. Call `client.connect` before the first request. Closes modelcontextprotocol#334
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Motivation and Context
The MCP specification requires an
initializerequest followed bynotifications/initializedbefore any other interaction. Issue #334 makes that handshake explicit on the stdio client, matching the Python SDK (ClientSession.initialize()) and TypeScript SDK (Client.connect(transport)).The change was staged to avoid a hard break. Phase 1 (#336) added
MCP::Client::Stdio#connectwhile keeping an implicit-init compatibility shim on the firstsend_request. Phase 2 (#338) emitted a deprecation warning when that shim ran. The warning has shipped since 0.16.0, so this final phase removes the shim.How Has This Been Tested?
send_requestnow raises aRuntimeErrorwhenconnecthas not been called, and no longer auto-starts the subprocess.connectis the sole entry point that spawns the process and performs the handshake, which avoids leaving an orphaned subprocess behind.The stdio test suite was reworked to call
connectexplicitly, a regression test was added for the new guard, andrake testpasses (1145 runs, 0 failures).Breaking Changes
Stdio clients that send requests without calling
MCP::Client#connectnow raise aRuntimeErrorinstead of silently initializing. Callclient.connectbefore the first request.Closes #334
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