# Failure modes

A failure mode is a recurring, nameable way an agent goes wrong. Common ones: hallucinated facts,
wrong tool selection, malformed tool arguments, context lost mid-conversation, loops that never
terminate, tasks declared done that were not, instructions overridden by retrieved content.

Failure modes exist because agent failures share causes. A given prompt, retrieval setup, or tool
interface produces the same class of error across many different inputs, so failures that look
unrelated in isolation often turn out to be the same mode with the same cause.

Naming a mode makes it measurable. Once a failure mode has a name, it's concrete enough to write a
grader for, count, and track over time. A mode observed at a specific rate is a measurement, and a
set of modes with rates describes an agent's reliability precisely enough to compare across
versions.

Which modes dominate depends on the architecture, because each architecture creates its own
opportunities to fail. RAG agents fail at grounding, tool-heavy agents fail at argument formation,
and multi-agent systems fail at handoffs. The distribution across modes is usually skewed, with a
small number of modes accounting for most observed failures.

## Questions answered under this concept

- [Are most agent errors caused by the agent's own logic?](https://tessary.ai/answers/failure-modes/are-most-agent-errors-caused-by-the-agents-own-logic)
- [Can content an agent retrieves override its own instructions?](https://tessary.ai/answers/failure-modes/can-retrieved-content-override-an-agents-instructions)
- [How do multi-agent systems actually fail?](https://tessary.ai/answers/failure-modes/how-do-multi-agent-systems-actually-fail)
- [How do I catch an agent that claims a task is done when it isn't?](https://tessary.ai/answers/failure-modes/how-do-you-catch-an-agent-claiming-a-task-is-done)
- [What causes a retry storm in an agent?](https://tessary.ai/answers/failure-modes/what-causes-a-retry-storm-in-an-agent)
- [What is inter-agent misalignment?](https://tessary.ai/answers/failure-modes/what-is-inter-agent-misalignment)
- [Why did an error one agent made become the next step's ground truth?](https://tessary.ai/answers/failure-modes/why-did-an-error-become-the-next-steps-ground-truth)

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Source: https://tessary.ai/answers/failure-modes
All concepts: https://tessary.ai/answers
From Tessary, agent reliability for AI agents in production: https://tessary.ai