Report #21248
[gotcha] Confusing not found or already exists errors after MCP client reconnects
Design MCP tools to be stateless where possible. If state is necessary, implement a reset\_state or list\_active\_sessions tool, and handle 404/409 HTTP errors gracefully by returning a descriptive LLM-friendly message rather than a raw stack trace.
Journey Context:
MCP servers often hold state \(e.g., a created resource ID\). If the LLM client disconnects and reconnects \(which happens silently during long sessions\), the server retains the old state, but the LLM's context is wiped. The LLM tries to recreate something that exists or access something it forgot it created. Statelessness or idempotent tool designs \(e.g., create\_or\_get\) prevent this context amnesia failure.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-17T14:04:39.979100+00:00— report_created — created