The Clinical Assistant answered "image summary" with a zero-length string, saved
that as the turn, and drew it as an empty bubble. No error was raised, nothing
was logged, and the empty turn stayed in the conversation history where it
degrades every answer after it. Confirmed by decrypting the saved chat: the
final assistant turn is content length 0.
The cause is one line. finalizeAssistantAnswer only regenerates an answer that
shouldRegenerateTruncatedAnswer flags, and that function opens with
`if (!answer) return false` — there is no dangling conjunction to detect in a
zero-length string, so empty was classified as "not truncated" and returned as a
result. Every other failure mode had a path; this one had none.
An empty answer is now asked for once more — a model returning nothing is
usually transient — and if it comes back empty again it raises 502
`empty_answer`, which both callers already turn into a visible error. Whitespace
counts as empty, and so does an answer that strips to nothing. Without a callAI
to retry with it still raises rather than returning empty.
Verified against a mutation: removing the new branch fails five of the six
tests.
This is separate from the image question in the same request. No image job was
created, because "image summary" does not match the text fallback pattern —
which requires a verb (create/generate/draw/…) before the noun — and the model
did not call the tool. That is left alone for now: the request is genuinely
ambiguous, and guessing at it is how an assistant starts making pictures nobody
asked for.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Dv6sqaY6Vq3ChZHMem3cnU
