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fix: treat IPv4-mapped IPv6 loopback as localhost - #3255
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OrKoN
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Oct 20, 2026
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What
isLocalhostreturnedfalsefor IPv4-mapped IPv6 loopback addresses such asws://[::ffff:127.0.0.1]:9222.URLserializes that host as[::ffff:7f00:1], which matched neither the[::1]check nor the dotted IPv4 regex.isLocalBrowserinToolHandler.tsusesisLocalhoston the browser'swsEndpoint. So a browser that is reached on a mapped loopback address was treated as remote, and file verification used theremoteoption instead oflocal. Telemetry'sis_localhosthad the same problem.Fix
The check now also accepts hostnames matching
[::ffff:7fXX:XXXX], which is 127.0.0.0/8 in mapped form. Mapped non-loopback addresses ([::ffff:128.0.0.1],[::ffff:192.168.1.1]) still returnfalse.Tests
I added
should return true for IPv4-mapped IPv6 loopbacktotests/utils/url.test.ts. It fails before the change and passes after. I rantests/utils/url.test.ts(36 tests) with tsx against the source rather than doing a fullnpm run build. Prettier check passes.AI assistance: I used an AI coding assistant (Grok Bot) to help find and write this fix. I reviewed the change and ran the tests myself.