Anthropic: Claude Code v2.1.131 — Windows VS Code activation and Mantle x-api-key hotfix

What does v2.1.131 fix?

Anthropic published Claude Code v2.1.131 on May 6, 2026, at 07:47 UTC — a hotfix release addressing two critical bugs reported on Windows and in the Mantle integration.

The first bug prevented activation of the Claude Code extension for Visual Studio Code. The bundled SDK contained a hardcoded build path in the createRequire polyfill — a path pointing to the build environment that did not exist on user systems. The result: the require() call failed before the extension had a chance to initialize.

What about Mantle authentication?

The second bug concerned authentication toward Mantle endpoints. Mantle is Anthropic’s internal model inference infrastructure used within Claude Code workflows.

The client was not sending the x-api-key HTTP header in requests, causing all API calls to Mantle to return HTTP 401 Unauthorized. The hotfix adds the header to the outgoing authentication configuration.

Which platforms are covered?

Binaries are published for macOS ARM64 and x64, Linux ARM64 and x64 (both glibc and musl variants), and Windows ARM64 and x64. The glibc + musl coverage matters for users running Claude Code inside Alpine Linux containers.

For context: createRequire is a Node.js function that creates a CommonJS-style require() call inside ECMAScript modules — it is used when modern ESM code needs to load older CommonJS modules. A hardcoded path in its polyfill means the build system left a reference to its own directory structure instead of a portable path, which breaks as soon as the binary leaves the CI environment.