Anthropic releases v1.0 of its Python SDK with breaking changes

On August 20, 2026, Anthropic released v1.0 of its Python SDK. It moved the HTTP layer to httpx2, required Python 3.10 or later and removed the Text Completions API along with sampling parameters on Messages methods.

Archive entry: this covers an event from August 20, 2026, and we published it on November 8, 2026. The details come from sources dated at the time and may have changed since.

On August 20, 2026, Anthropic released version 1.0 of its anthropic Python SDK, a major release with breaking changes. Claude Code v2.1.239 followed on August 21, 2026 with a migration command, as the Claude Code v2.1.239 release page on GitHub shows.

What changed in version 1.0

The HTTP layer moved from httpx to httpx2, a maintained, API-compatible fork. Custom http_client, Timeout and transport objects were built from httpx2, and calling httpx2.alias_httpx() at startup kept tracing or mocking libraries that patch httpx working.
Version 1.0 required Python 3.10 or later.
It removed the legacy Text Completions API, the temperature, top_p and top_k parameters on Messages methods, and the tool runner's client-side compaction_control.
On the async client, .with_raw_response results needed await response.parse().
AnthropicBedrock raised an error when no AWS region was configured, instead of defaulting to us-east-1.

What it meant for Python projects

Python projects that pinned anthropic loosely could break on upgrade, especially those that passed sampling parameters, used Bedrock without a region, or patched httpx.

Migration help and sources

The Claude Code command, /claude-api upgrade, migrated Python projects from anthropic 0.x to 1.x. Timeouts in 1.x used anthropic.Timeout, not httpx.Timeout. A v1 migration guide listed every change with before-and-after snippets, and the Claude Platform release notes record the SDK release.

Sources

Release v2.1.239 · anthropics/claude-code · GitHub (Anthropic (GitHub), August 21, 2026, official)
Claude Platform release notes - Claude Platform Docs (Anthropic (Claude Platform Docs), August 20, 2026, official)

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