# How do I map a production trace to a MAST failure mode?

Match the trace to a stage first, then to a mode inside it. A design flaw shows up before any real interaction: the same step running twice with nothing new learned between attempts, or the run continuing after the task is already done or already correctly ruled unsolvable. A breakdown between agents shows up mid-run: one agent's own reasoning reaches a conclusion its message to the next agent doesn't carry, or it acts on an ambiguous instruction instead of asking. A verification miss shows up at the end: a fix reported as applied with no check that it actually took effect, or a check that ran but only confirmed something trivial.

Don't expect one mode to explain a trace on its own. The paper's own correlation analysis finds specific failure modes correlate as high as 0.63 when they share a surface symptom, meaning the same symptom, information one agent needed and didn't get, can register as a design flaw, a withheld message, or an ignored one depending on which agent actually had it and what it did next, the same tangle behind [an error one agent makes becoming the next agent's ground truth](/answers/failure-modes/why-did-an-error-become-the-next-steps-ground-truth).

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Sources:
- "Why Do Multi-Agent LLM Systems Fail?" (arXiv:2503.13657): https://arxiv.org/abs/2503.13657 (fetched 2026-09-18)

Source: https://tessary.ai/answers/mast-taxonomy/how-do-i-map-a-production-trace-to-a-mast-failure-mode
More on Mast taxonomy: https://tessary.ai/answers/mast-taxonomy
From Tessary, agent reliability for AI agents in production: https://tessary.ai