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ResearchWed, August 19, 2026·18h ago2 sources corroborating

HarnessRisk benchmarks safety failures in agent harnesses

The benchmark tests how agent harness risks emerge across lifecycle phases and configurations.

Why it matters

The results suggest agent safety depends not only on the model but also on harness design, configuration and operational lifecycle controls. The finding that Harness Configuration was the most vulnerable phase highlights a practical risk area for deployed agent systems.

The key points

  • 1.HarnessRisk covers six phases of agent harness operation.
  • 2.Attack success ranged from 12.6% to 80.9% across tested setups.
  • 3.Harness Configuration was the most vulnerable phase.

Researchers introduced HarnessRisk, a lifecycle-oriented benchmark for safety in LLM agent harnesses that manage tools, extensions, persistent state, permissions and external actions. The benchmark includes 128 sandboxed cases pairing benign user objectives with adversarial instructions embedded in untrusted workflow artifacts. Across three harnesses, six language models and 14 model and harness configurations, attack success ranged from 12.6% to 80.9%, while Utility stayed between 75.0% and 97.6%.

Try this today

Audit agent harness configuration defaults and security-sensitive parameters before expanding tool or permission access.

Sources & original reporting

This brief summarizes and links to reporting from the publishers below.

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