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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 v2.1.257 ·

New 400-error classification for tool_addition/tool_removal API errors

Rejected mid-conversation tool additions are now sorted into specific 400-error reasons for retry and telemetry.

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KindInternal Changesin v2.1.257,
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Rejected mid-conversation tool additions are now sorted into specific 400-error reasons for retry and telemetry.

New internal classification logic sorts 400 errors from beta tool-use blocks into specific reasons: header_rejected, block_type_unknown, after_paused_turn, model_unsupported, too_many_definitions, pfc_only, unknown_tool_reference, or other. This applies when a tool_addition or tool_removal request is rejected, likely feeding retry and telemetry logic for beta feature flags.

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Names in the bundleheader_rejectedmodel_unsupportedtoo_many_definitions

See this entry in the whole of v2.1.257 →

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