[tiensonqin]

Summary

Read Darwin PreferredLanguages only from the global AppleLanguages domain. When it is absent, return an empty list rather than falling back to NSLocale.preferredLanguages, which becomes app-scoped after SaveLocale.

Remove only TestLocales' invalid nonempty-list assumption; preserve region validation, saved-language round trips, cleanup, and the system-before/after equality invariant. No new tests, APIs, dependencies or SDK-feature changes.

Testing

• Preserved pristine-5c failure (x-Test versus en-001); reproduced red with the existing invariant and verified green after the minimal production fix.
• Before any test preference mutation, a temporary native pre-main guard verified the actual synthetic main CFBundle ID ai.devin.mygo.locale79be43a0. The guard and application-bundle runner are outside the repository; no global/human preference writes or GUI testing.
• CGO_ENABLED=0 go test -count=1 -timeout 20m -exec <owned-application test runner> ./...: passed. Only the Darwin test binary is wrapped; MYGO_E2E is absent.
• CGO_ENABLED=1 go test -race -count=1 -exec <owned-application test runner> ./internal/darwin: passed (race instrumentation only).
• CGO-disabled build, vet and mygo_noinspector vet: Darwin arm64, Linux amd64 and Windows amd64 passed. Gofmt/diff checks passed.
• Paired Go 1.27.3 release-size builds for counter-native and hello: no byte growth in all ten pairs (Darwin arm64; Linux amd64/arm64; Windows amd64/arm64).

Tested on:

• macOS
• Windows
• Linux
• Web
• Other: Linux/Windows cross-build and vet only, not runtime acceptance

AI disclosure

• Tool and model: Devin, built by Cognition AI; underlying model/version is not exposed by this environment.
• Used for: implementation, existing-test adjustment, validation and this description.
• A human read every line of this change and can explain it.

Link to Devin session: https://app.devin.ai/sessions/79be43a0fc7b4ee3b783fa85566b6c1d
Open in Devin Desktop: https://app.devin.ai/desktop/session/79be43a0fc7b4ee3b783fa85566b6c1d?variant=devin
Requested by: @tiensonqin

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring