New ByteDance paper asks a much better question about AI agents: did the instruction actually change anything?

We might be overestimating how controllable AI agents are because our tests often agree with their defaults.

Want to know whether your agent actually follows instructions? Give it a rule that goes against what it normally does.

Harness-IF tests that harder case: rules that push against a model's default behavior, spread across the places coding agents actually read, including system prompts, tool descriptions, skill descriptions, project files, and user instructions.

Across 12 frontier models and 60 multi-turn coding tasks, every model scored worse on these against-prior rules, i.e. once instructions pushed against its natural defaults.

– arxiv. org/abs/2608.11727

Title: "Harness-IF: Evaluating Instruction Following Across Instruction Surfaces in Coding Agents"