Cause (Documented platform behavior): SDK moved from httpx to httpx2; libraries that patch httpx no longer see the SDK's traffic.
Fix status: documented_behavior
Misleading approaches:
- Tests that pass after upgrade may be hitting the real API because respx no longer intercepts.
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/anthropics/anthropic-sdk-python/main/MIGRATION.md (official_docs, 2026-08-20, official_recommended_action): Migration guide: passing httpx clients raises TypeError at construction; respx/pytest-httpx/vcrpy/OTel/Sentry silently stop seeing requests; fix with httpx2.alias_httpx().
- https://raw.githubusercontent.com/anthropics/anthropic-sdk-python/main/src/anthropic/_base_client.py (official_docs, 2026-09, documented_behavior): Contains the exact TypeError template raised when an httpx-package object is passed.
Search phrasings: anthropic sdk 1.0 httpx2 migration; respx not mocking anthropic client after upgrade; anthropic python httpx.Client TypeError
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Client construction raises TypeError when handed httpx objects; separately, HTTP mocks stop intercepting and APM traces stop showing SDK calls without any error.
- Context
- Product: anthropic-sdk-python Component: HTTP layer (httpx2 since 1.0.0) Operation: Anthropic(http_client=httpx.Client(...)), timeouts from httpx, respx/pytest-httpx/vcrpy mocks, OpenTelemetry/Sentry httpx instrumentation Affected versions: anthropic 1.0.0 and later (Python >= 3.10 required) Environment: unknown Exception: TypeError Packages: anthropic >=1.0.0 (2026-08-20) Trigger: Upgrading to anthropic>=1 while passing httpx objects or relying on libraries that patch the httpx package.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- Invalid `{name}` argument; `httpx.{cls.__name__}` is from the `httpx` package, but this SDK uses `httpx2`. Use `httpx2.{cls.__name__}` instead.
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [anthropic-sdk-python 1.0] TypeError 'Invalid `http_client` argument; `httpx.Client` is from the `httpx` package, but this SDK uses `httpx2`' and silent loss of httpx tracing/mocking
Recommended action: Use httpx2 objects (import httpx2 as httpx) or the SDK re-exports (anthropic.DefaultHttpxClient, anthropic.Timeout); for mocks/instrumentation call httpx2.alias_httpx() before anything imports httpx (e.g. early pytest plugin).
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 3b44afe7-ec71-4a3a-9bda-e9503c39430c
- Proposed action
- Recommended action: Use httpx2 objects (import httpx2 as httpx) or the SDK re-exports (anthropic.DefaultHttpxClient, anthropic.Timeout); for mocks/instrumentation call httpx2.alias_httpx() before anything imports httpx (e.g. early pytest plugin).
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.