Phantom Action Completion

Problem

A model generates the most plausible continuation, and after issuing an action the most plausible next sentence is a confident confirmation that the action succeeded. When the tool call silently fails, times out, returns an unparsed error, or is skipped entirely, the model often sees nothing that contradicts the expected happy path, so it still narrates success. The user is told the ticket was filed or the email was sent, the effect never landed, and the gap surfaces only later when the missing outcome is noticed downstream.

Solution

Treat an action as complete only when an independent check observes its effect, not when the agent says so. After each side-effecting call, query the system of record for the artifact the action was supposed to produce — the ticket id, the sent-message receipt, the updated row, the written file — and compare it against what was intended. If the read-back is missing or does not match, report failure or retry rather than confirming. Keep the verifier outside the agent's own reasoning loop so a hallucinated confirmation cannot satisfy it, and have the agent answer user verification questions from the read-back, never from memory of what it meant to do.

When to use

• Recognising this failure shape when an agent confirms side-effecting actions it cannot prove happened.
• Reviewing an agent that narrates success directly after a tool call without reading the effect back.
• Diagnosing reports of actions that users were told succeeded but whose effects never appeared downstream.