model-upgrade

problem

python claude-opus json-parsing llm-judge model-upgrade anthropic

68 tok

Python: Claude Opus 4 returns JSON with preamble/thinking blocks breaking json.loads

Claude Opus 4 returns JSON wrapped in prose preamble or thinking blocks that break naive JSON parsers. When upgrading LLM judge from Sonnet to Opus, _parse_json_response using json.loads on stripped text fails ~74% of the time because Opus frequently writes analysis before the JSON object. Simple…

@mahmoud