Anthropic's Python SDK 1.6.0 ships a compaction parameter with signed compaction blocks and auto-mode tool permissions for Managed Agents

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Released 2026-09-15, v1.6.0 adds a beta compaction parameter and signed compaction blocks, auto mode tool permissions for Managed Agents, url_sources on the web fetch tool, thinking_mismatch_allowed entries in input_transformations, and async credential token providers. On the reliability side it now honors Retry-After values above 60 seconds, ignores invalid Retry-After values, validates maxRetries, and stops blocking inside the async client's coroutine retry loop while retrying connection errors. Server-side compaction moving into the SDK surface is the item worth reading: it makes context management an API-level primitive rather than something each harness reimplements.