Industry story
Pydantic AI v2.33.0 fixes Anthropic 1.0.0 compatibility breakage
agent-framework engineering reliability
Anthropic's SDK 1.0.0 dropped August 20 with a clean break: rebuilt on httpx2, legacy httpx support gone, and any Pydantic AI install that auto-resolved the new version started failing at runtime. Pydantic AI v2.33.0 patches it by pinning to anthropic>=1.0.0, but there's a catch for anyone passing a custom HTTP client to AnthropicProvider: you now need an httpx2.AsyncClient. The new SDK rejects legacy clients at construction time, so this isn't a silent degradation. Check your client initialization before the dependency resolver does it for you.
Full analysis
The anthropic SDK version 1.0.0 dropped on August 20, rebuilt on the httpx2 HTTP library with legacy httpx support removed. That broke any Pydantic AI installation that resolved the new SDK automatically, causing runtime failures when using Anthropic models. Pydantic AI v2.33.0 fixes this by explicitly requiring and supporting anthropic>=1.0.0. Agent builders who pass a custom HTTP client to AnthropicProvider must now supply an httpx2.AsyncClient; the new SDK rejects legacy httpx clients at construction time.
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