{"version":"2.1.271","anchor":"api-400-error-classification-extended-for-turn-scoped-system","canonical_anchor":"api-400-error-classification-extended-for-turn-scoped-system","heading":"API 400-error classification extended for turn-scoped system messages and thinking-resumption","tier":"internal","area":"Elsewhere","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.271\/e\/api-400-error-classification-extended-for-turn-scoped-system","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.271","markdown":"### API 400-error classification extended for turn-scoped system messages and thinking-resumption\n\nTwo new API error patterns are now specifically recognized: turn-scoped system messages and thinking-resumption rejections\n\n**What**\n\nClaude Code now recognizes two additional specific patterns among the 400-error responses the Claude API can return:\n\n- a validation error related to `clear_at` and \"turn-scoped system message\"\n\n- a 400 error tied to the `thinking_resumption` beta feature header\n\n**Why**\n\nSorting these into their own specific categories, rather than lumping them into a generic rejection, likely helps Claude Code decide when to retry a request or fall back to a different approach, and improves how these errors are tracked internally.\n\n- Area: Elsewhere\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 1\/5"}