Observed arrival · 2026-08-25
MCP Lab Tests the Ways MCP Systems Break
An open-source scenario runner and test server for reproducing timeouts, cancellations, hangs, and disconnects in Model Context Protocol systems.
Field notes
MCP Lab models failures as checked scenario files rather than ad hoc manual tests. The visible example calls a delay tool with a 250-millisecond delay, a 1,000-millisecond timeout, and a 500-millisecond maximum-duration assertion. The current capability list includes cancellation-aware delays, client-cancelled hangs, in-flight transport loss, and a separate ping path for health and post-condition checks. Streamable HTTP transport and JUnit report output are identified as planned rather than implemented.
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