[dajiaohuang]

What and why?

On Windows, the documented path-only errorTracking.sourcemaps.minifiedPathPrefix is joined using the host filesystem separator. A real esbuild consumer with /static/js and assets/main.js passed \static\js\assets\main.js to the sourcemap sender instead of /static/js/assets/main.js.

This is independent of the debug-ID quoting change in #529; it does not change debug-ID extraction.

How?

Normalize native relative-path separators and use POSIX joining only for path-only URL prefixes. Filesystem paths and full-URL handling remain unchanged. Add a public-adapter build regression for all five supported bundlers and clarify the URL-path documentation.

Validation

• Windows base-failing esbuild consumer reproduced the incorrect URL above; the minimal correction passed that reproduction.
• Final focused public-adapter regression: 5/5 passed (esbuild, Rollup, Rspack, Vite, Webpack), with tiny owned fixtures and the final sender mocked. Seven older tests in that file were excluded by the focused test-name filter.
• yarn typecheck:all passed twice; changed TypeScript files pass ESLint and Prettier; git diff --check passed.
• Tests used Windows Node 24.14.1 and repository Yarn 4.10.3, BUILD_PLUGINS_ENV=test, blocked network, dummy authentication and no real upload.

Limits: the broader local runs were not green (factory 70/71, feature/helpers 138/163, Git 30/44); Windows/POSIX assertion assumptions, missing fixture dependency/Git setup, and the independently repaired URL behavior were distinguished rather than treating these counts as full acceptance. Root yarn format exceeded Windows command-line length; scoped ESLint passed. yarn cli integrity stopped at child spawn yarn ENOENT although bundled Yarn itself ran directly, so full generated/compliance verification remains outstanding. No full browser, hosted-CI, live Datadog, or version-matrix validation is claimed.

[jakub-g]

@dajiaohuang could you please rebase this PR and sign your commit? We require signed commits for merging.

[crousseaux]

lgtm