---
id: known-bugs/askuserquestion-can-fail-to-parse-its-own-call
title: 'AskUserQuestion can fail to parse its own call'
theme: known-bugs
status: open
created: 2026-08-21
date_source: stated
order: 3
---

**`AskUserQuestion` rejected a well-formed call with `InputValidationError: called with input that could
not be parsed as JSON`.** Seen 2026-08-21 in the deploy commander's first turn, on Sonnet.

The tell is in the transcript: the failed call arrives as `{"__unparsedToolInput": {"raw": "{\"questions\":
[…"}}` — the arguments reached the harness as a **string** rather than an object, and the harness reported
that as the model's fault. The retry, byte-identical in intent, went through and the question rendered
normally.

So it is recoverable and it self-corrected, which is why it is filed here rather than treated as urgent.
What makes it worth fixing anyway: this is the same tool as the stall bug fixed earlier the same day, on
the path where an agent asks a question and waits. A parse failure there burns a turn, and if it happened
on the **second** attempt too the agent would most likely give up asking and guess — which is the failure
mode the question mechanism exists to prevent.

Worth capturing the raw payload when this fires rather than only the first 200 bytes, since the message
truncates exactly where the interesting part would be.