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Sweep 22 Sep 2026 · 17:19Z Build v2.1.280 501 read Stable v2.1.267 Latest v2.1.280 Next v2.1.280 Feeds RSS JSON llms.txt Unofficial
Claude Code v2.1.263 ·

New thinkingPrefixMismatchBehavior field on API telemetry, tied to a 'block_binding' beta feature

API telemetry can now log a thinking-block mismatch setting, but only under a specific unreleased beta header.

TierUnder the hoodhow much it should matter to you
Useful3my rating, 1 to 5
Signal4worth watching, 1 to 5
AreaTelemetrywhat it touches
KindIn Developmentin v2.1.263,
Under the hood Nothing to try yet

API telemetry can now log a thinking-block mismatch setting, but only under a specific unreleased beta header.

The tengu_api_query and tengu_api_success telemetry events now carry a thinkingPrefixMismatchBehavior field. It's populated from block_binding.mismatch_behavior, which is attached to the thinking config only when a specific beta header is present and the request doesn't already carry its own thinking key.

See this entry in the whole of v2.1.263 →

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