Stable Error Model
MCP Rigor failures carry a stable code, category, sanitized message, and QA-facing action.
| Category | Baseline code | QA action |
|---|---|---|
| configuration | MCP-CONFIG-000 | Check suite target and settings. |
| language compilation | MCP-LANG-000 | Correct the highlighted statement. |
| data loading | MCP-DATA-000 | Check the named source, row, and column. |
| extension | MCP-EXT-000 | Review manifest, permission, and export. |
| server spawn | MCP-SPAWN-000 | Check command and working directory. |
| initialization | MCP-INIT-000 | Inspect why MCP initialization did not finish. |
| transport | MCP-TRANSPORT-000 | Check process/HTTP connection and server logs. |
| MCP error | MCP-REMOTE-000 | Review the server's MCP code and message. |
| schema | MCP-SCHEMA-000 | Compare the result with the required schema. |
| assertion | MCP-ASSERT-000 | Compare expected path/value with response. |
| timeout | MCP-TIMEOUT-000 | Inspect server performance or explicit timeout. |
| cancellation | MCP-CANCEL-000 | The operation was stopped before completion. |
| cleanup | MCP-CLEANUP-000 | Inspect cleanup steps and server shutdown. |
| internal | MCP-INTERNAL-000 | Preserve sanitized evidence and report the bug. |
Specific existing codes remain stable within these categories. APIs expose classifyFailure(), formatFailure(), RigorError, and FAILURE_CODES. New codes may be added, but released codes are not repurposed.
Terminal formatting removes control sequences before display. Private causes and stacks are not part of the stable user-facing contract.