Anthropic's Python SDK 1.0 Can Make Your APM Stop Seeing Claude Traffic
v1.0 moved the HTTP layer from httpx to httpx2. A type checker catches nearly every break — except the one where OpenTelemetry, Sentry, respx, pytest-httpx and vcrpy keep working and quietly stop seeing your requests.
NeuroX AI · August 24, 2026
anthropic 1.0.0 shipped on 20 August and moved the SDK's HTTP layer from httpx to httpx2. The migration guide is blunt about what that costs you: tracing and mocking libraries "keep working but silently stop seeing the SDK's requests."
Read the failure mode, not the diff. OpenTelemetry's HTTPXClientInstrumentor, Sentry's httpx integration, respx, pytest-httpx and vcrpy all work by patching the httpx package. The SDK no longer imports it. Nothing raises. Your spans just stop containing the most expensive dependency in the stack, and your HTTP-mocking tests stop intercepting the calls they were written to intercept.
Contrast that with the rest of the release. Legacy Text Completions removed, temperature/top_p/top_k gone from messages.create(), .text and .content now methods, Bedrock raising a ValueError instead of silently defaulting to us-east-1 — every one of those is a TypeError or a red squiggle. The guide even recommends running pyright as your checklist. It catches almost everything. The instrumentation gap is the part it structurally cannot see.
One line fixes it: call httpx2.alias_httpx() at the top of your entry point, before anything imports httpx.
The wider lesson is the one we keep relearning. An upgrade that breaks loudly is cheap. An upgrade that breaks your ability to observe the upgrade is the expensive kind — and you find it weeks later, in a bill or an incident, not in CI.