How to Fix Claude API’s 400 Orphaned Tool Result Error in Production

BetterClaude Gateway: The Silent Guardian Against Claude API’s Achilles’ Heel The core question this article answers: When Claude API returns a 400 error due to orphaned tool results in conversation history, how can you automatically fix it without touching a single line of client code? If you’ve built anything non-trivial with Claude’s function calling, you’ve seen it: a perfectly working application suddenly crashes with tool_result block(s) that reference non-existent tool_use ids. This isn’t a rate limit or a temporary outage—it’s a data corruption error that stops production systems cold. BetterClaude Gateway is an edge-deployed proxy that detects these “orphan” blocks …