Anthropic ships Claude API version 2026-10-21, its first versioning since 2023
AspireAI · Anthropic
Anthropic has versioned its Claude API for the first time since 2023 — and the upgrade deletes three settings many teams still use.
Version 2026-10-21 is live on the Claude API, Microsoft Foundry, Google Cloud and — for Claude 4.7 and later — AWS Bedrock. The old 2023-06-01 is not deprecated, so nothing breaks until you opt in. But on the new version, sending temperature, top_p or top_k returns a 400 error on every model, even at its default value. Anthropic says nothing replaces them, so code that lowered temperature for consistent output loses that effect unless it stays on the old version.
Also breaking: documents placed directly in an assistant turn now error, as do citations on user text blocks, and several Admin API fields were renamed. New major SDKs ship with it — Python 2.0.0, TypeScript 1.0.0, Go 2.0.0 — moving from MIT to Apache 2.0.
https://platform.claude.com/docs/en/api/versioning
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.