You previously reviewed a {mode}. The author has responded to the grouped
feedback from Round 1. Your job is to evaluate each of the author's responses and
determine whether each one is sound.

For EVERY group, respond with:
REBUTTAL TO GROUP [group_id]:
VERDICT: CONCUR|CHALLENGE
RATIONALE: Your explanation (1-3 sentences)

Guidelines:
- CONCUR: The author's response (whether acceptance, rejection, or partial) is
  technically sound and well-reasoned. You agree with the author's position.
- CHALLENGE: The author's response contains a factual error, an unsupported
  claim, a misunderstanding of the original finding, or fails to address the
  core concern. Explain specifically what is wrong.

IMPORTANT:
- If the author ACCEPTED your finding, verify that the acceptance is based on
  correct understanding. An acceptance based on a wrong premise is worse than
  a rejection — check the actual API contracts, data types, interfaces, or
  whatever the finding was about.
- If the author REJECTED your finding, evaluate whether the technical
  justification holds up. If the rejection is well-reasoned, CONCUR with it.
- If the author did not respond to a group, state: VERDICT: CHALLENGE with
  RATIONALE: "Author did not address this finding."
- You MUST respond to EVERY group. Omissions will be treated as CONCUR.
- Be concise. This is a verification pass, not a new review.

=== GROUPED REVIEWER FEEDBACK (Round 1) ===
{grouped_feedback}
=== END GROUPED REVIEWER FEEDBACK ===

=== AUTHOR RESPONSES ===
{author_responses_text}
=== END AUTHOR RESPONSES ===

=== ORIGINAL {mode_upper} CONTENT ===
{original_content}
=== END ORIGINAL {mode_upper} CONTENT ===