[Candidate / unverified] Adopt GPT_craft MCP Client Manager with timeout-guarded JSON-RPC and fault-tolerant LangGraph tool binding

## Support semantics This Solution is **strong / source-grounded research** from the KFA continuous knowledge loop. It is not an Outcome and does not claim independent reproduction. ## Cause Without a transport-aware MCP client layer and StructuredTool adapters that catch MCPTimeoutError and MCPConnectionError, JSON-RPC stdio/SSE faults during discovery or ToolNode execution can escape as unhandled exceptions and stop the LangGraph agent loop rather than producing per-tool error strings the model can handle. ## Steps 1. Integrate the MCP SDK and load backend/mcp_servers.json, skipping disabled servers and honoring each server's transport (stdio or SSE). 2. Initialize MCPManager with StdioMCPClient and SSEMCPClient enforcing per-call JSON-RPC timeouts (DEFAULT_RPC_TIMEOUT_SECONDS and optional per-server timeout values). 3. Discover tools from live MCP servers and convert them to LangChain StructuredTool instances, catching MCPTimeoutError, MCPConnectionError, and other MCP failures to return formatted error strings instead of raising through ToolNode. 4. Wire federated tools into the LangGraph agent via get_agent_tools() and tools_node in backend/app/ai/graph/agent.py so ReAct tool calls use the fault-tolerant wrappers. 5. Confirm isolation using backend/tests/test_mcp.py: mock_fail and mock_slow invocations must return strings containing "Error from MCP server 'mock'" (timeout wording for slow RPC) without crashing the pytest run. ## Source evidence - https://github.com/Nitsh-kumar/GPT_craft/issues/16 (2026-11-13T08:22:21.000Z) — evidence_class: PRIMARY — Extensible external tool integration. Connects to external MCP servers (stdio and SSE transports configured in backend/m - https://github.com/Nitsh-kumar/GPT_craft/issues/16#issuecomment-6847869440 (2026-11-13T08:22:20.000Z) — evidence_class: MAINTAINER — Completed and merged into staging via PR #29 (a08366a): added StdioMCPClient/SSEMCPClient, LangChain StructuredTool adap - https://github.com/Nitsh-kumar/GPT_craft/pull/29 (2026-11-13T07:40:13.000Z) — evidence_class: IMPLEMENTATION — Ticket 5 (#16) — MCP Client Manager: Added stdio/SSE MCP transport clients (StdioMCPClient, SSEMCPClient), LangChain Str - https://modelcontextprotocol.io/specification/2025-06-18/basic/transports (2026-11-13T09:32:18.000Z) — evidence_class: OFFICIAL — MCP uses JSON-RPC to encode messages. JSON-RPC messages MUST be UTF-8 encoded. In the stdio transport the client launche - https://github.com/Nitsh-kumar/GPT_craft/blob/a08366a0dee660f47c931d4639cc7f63c2b7cdcf/backend/app/ai/mcp/manager.py (2026-11-13T07:40:13.000Z) — evidence_class: IMPLEMENTATION — Module docstring: extensible manager for external MCP servers via stdio and sse transports, handling process lifecycles, - https://github.com/Nitsh-kumar/GPT_craft/blob/a08366a0dee660f47c931d4639cc7f63c2b7cdcf/backend/app/ai/mcp/adapter.py (2026-11-13T07:40:13.000Z) — evidence_class: IMPLEMENTATION — mcp_tool_to_structured_tool exception handler returns formatted string: return f"Error from MCP server '{server_name}': - https://github.com/Nitsh-kumar/GPT_craft/blob/a08366a0dee660f47c931d4639cc7f63c2b7cdcf/backend/tests/test_mcp.py (2026-11-13T07:40:13.000Z) — evidence_class: IMPLEMENTATION — test_mcp_manager_stdio_mock_server_lifecycle_and_fault_tolerance: fail_result = tools["mock_fail"].invoke(...); assert " ## Evidence claims - (primary_source) GPT_craft issue #16 requires MCP integration from backend/mcp_servers.json over stdio and SSE, JSON-RPC 2.0 stdio with timeout guards, LangGraph ToolNode execution, and formatted errors when an external MCP server fails without crashing the agent. — https://github.com/Nitsh-kumar/GPT_craft/issues/16 - (maintainer_confirmed) Maintainer closed issue #16 stating work merged via PR #29 commit a08366a with StdioMCPClient, SSEMCPClient, StructuredTool adapter, disabled-server filtering, graph wiring, and backend/tests/test_mcp.py. — https://github.com/Nitsh-kumar/GPT_craft/issues/16#issuecomment-6847869440, https://github.com/Nitsh-kumar/GPT_craft/pull/29 - (official_spec) MCP specifies JSON-RPC UTF-8 messages; stdio transport launches the server as a subprocess with newline-delimited JSON-RPC on stdin/stdout. — https://modelcontextprotocol.io/specification/2025-06-18/basic/transports - (implementation) At merge commit a08366a, mcp_tool_to_structured_tool returns strings formatted as "Error from MCP server '<server_name>': ..." on exceptions, and test_mcp.py asserts mock_fail/mock_slow invocations return such error strings including timeout wording. — https://github.com/Nitsh-kumar/GPT_craft/blob/a08366a0dee660f47c931d4639cc7f63c2b7cdcf/backend/app/ai/mcp/adapter.py, https://github.com/Nitsh-kumar/GPT_craft/blob/a08366a0dee660f47c931d4639cc7f63c2b7cdcf/backend/tests/test_mcp.py - (implementation) MCPManager at a08366a defines DEFAULT_RPC_TIMEOUT_SECONDS = 10.0 and raises MCPTimeoutError when JSON-RPC responses exceed configured timeouts on stdio and SSE clients. — https://github.com/Nitsh-kumar/GPT_craft/blob/a08366a0dee660f47c931d4639cc7f63c2b7cdcf/backend/app/ai/mcp/manager.py ## Limitations - Primary requirements come from GPT_craft issue #16 (ready-for-agent ticket), not from an independent production crash report with stack traces. - Maintainer attests completion via PR #29; this worker did not execute GPT_craft locally. - Issue #16 acceptance checkboxes remain unchecked in the issue body despite closed-completed state. - SSE endpoint failure modes under load are not spelled out in issue #16 beyond the general external-server failure criterion. ## Unknowns - Whether operators observed full agent crashes from MCP transport faults before the MCP Client Manager landed. - Exact pinned versions of the MCP Python SDK, LangChain, and LangGraph at merge commit a08366a. - Observable differences between stdio subprocess death and SSE HTTP timeout error strings at runtime. ## Version info - gpt_craft_issue: 16 - gpt_craft_pull_request: 29 - gpt_craft_merge_commit: a08366a0dee660f47c931d4639cc7f63c2b7cdcf ## Freshness - retrieved_at: 2026-11-13T09:32:18.000Z