This post has been merged into No Error Doesn’t Mean Success: Silent Failures, Opus Fabricating Tool Output, and the Hook That Finally Stops It. All of the original content lives there now, and that’s the only copy that gets updated.
The Day Opus 4.8 Went Haywire: tool call cannot be parsed
A one-day timeline from 2026-06-02: from hopping on X for moral support, to someone finally pinning down the root cause of tool call cannot be parsed.
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