Self-Eval Bias

An agent that just produced a plan, a diff, or a report cannot fairly grade it in the same context. The reasoning that justified writing it is still loaded — every doubt was already resolved in favor of shipping. Asked to review, the same context reliably returns "looks good, ship it." This is not review. It is rationalization wearing a review's uniform.

The pattern shows up hardest in planner/generator/evaluator architectures where the evaluator drifts toward leniency over long runs — the prompts it reads fill up with the generator's reasoning, and skepticism erodes. (See Prithvi's March 2026 post on the three-agent harness: https://blog.anthropic.com/three-agent-harness-march-2026.)

When to apply

• You just wrote code, a plan, or a claim, and the next step is "confirm it's correct".
• A reviewer verdict comes back positive with no cited line numbers, no failing case explored, no counter-example attempted.
• You're about to mark a feature passes: true, close an issue, or hand off to the next session.
• The evaluator persona in a multi-agent loop has agreed with the last N generator outputs in a row.

Procedure