Summary

FsCheckPropertyTestExecutor.cs:195 allocates a char[] on every call:

var newlineIndex = afterShrunk.IndexOfAny(['\r', '\n']);

The ['\r', '\n'] collection expression allocates a fresh array each invocation. Hoist to a static SearchValues<char>:

private static readonly SearchValues<char> _lineEndings = SearchValues.Create("\r\n");
// ...
var newlineIndex = afterShrunk.AsSpan().IndexOfAny(_lineEndings);

Impact

Low — this is an error path (only runs when a property-based test fails and a shrunk counterexample is being parsed). No measurable runtime gain in the common case. Filed for consistency with the rest of the codebase, which already uses static SearchValues<char> (e.g. MetadataFilterMatcher.cs:243, PathValidator.cs:10).

Acceptance

• Static SearchValues<char> field added
• No per-call array allocation
• FsCheck tests still pass

Found during a hot-path API-modernization sweep.